JP7458437B2 - Optical element, variable focus element and head mounted display - Google Patents

Description

The following disclosure relates to an optical element, a variable focus element including the optical element, and a head mounted display including the variable focus element.

In recent years, variable-focus optical systems have been proposed for head-mounted displays and other applications that combine Pancharatnam Berry (PB) lenses with optical elements such as switchable half-wave plates (sHWPs). sHWPs are devices that can switch the polarization state of left-right circularly polarized light, and are realized using liquid crystal.

As a technique related to a variable focus optical system, for example, Patent Document 1 includes a waveguide and a broadband adaptive lens assembly, the waveguide guiding light in a lateral direction parallel to the output surface of the waveguide. and further configured to externally couple the guided light through the output surface, through which the broadband adaptive lens assembly internally couples externally coupled light from the waveguide. A display device configured to couple and diffraction is disclosed.

Patent Document 2 discloses a variable focus block including an sHWP and a plurality of liquid crystal lenses.

Patent Document 3 discloses an achromatic polarization switch that converts linearly polarized light with an initial polarization orientation, the switch comprising: a first liquid crystal (LC) cell having a first orientation axis with respect to the initial polarization orientation; a second LC cell having a second orientation axis with respect to the axis.

Patent Document 4 discloses a first laminated birefringent layer and a second laminated birefringent layer, each local optical axis of which extends over the respective thicknesses of the first layer and the second layer. an optical system comprising a first laminated birefringent layer and a second laminated birefringent layer rotated at a torsion angle and aligned along an interface between the first layer and the second layer; A device is disclosed.

Specific Publication No. 2021-501361 US Patent No. 10379419 Special Publication No. 2009-524106 Special table 2014-528597 publication

Patent Documents 1 to 4 described above have a device structure that can switch over a wide band between polarization modulation that changes the polarization state of left and right circularly polarized light and polarization non-modulation that does not change the polarization state of left and right circularly polarized light, and that can also be made thinner. There is a problem that it is difficult to realize this.

The present invention has been made in view of the above-mentioned current situation, and provides an optical element that can switch between polarization modulation and non-polarization modulation over a wide band and that can be made thinner, a variable focus element equipped with the above-mentioned optical element, and the above-mentioned. An object of the present invention is to provide a head mounted display including a variable focus element.

(1) One embodiment of the present invention includes a liquid crystal cell including a first substrate, a liquid crystal layer, and a second substrate;
a 1/4 wavelength film, the liquid crystal layer contains liquid crystal molecules that are twistedly aligned between the first substrate and the second substrate, and the liquid crystal cell includes the first substrate and the second substrate. At least one of the substrates has an electrode for applying a voltage to the liquid crystal layer, and the electrode is arranged in a first state in which the liquid crystal molecules on the first substrate side are aligned in a first alignment direction; The liquid crystal molecules on the substrate side are arranged to be switchable between a second state in which the liquid crystal molecules on the substrate side are aligned in a second alignment direction perpendicular to the first alignment direction in plan view by applying a voltage to the liquid crystal layer. The switching between the first state and the second state controls the polarization state of light incident on the liquid crystal cell, and when circularly polarized light enters the liquid crystal cell, in the first state, The circularly polarized light is converted into a first linearly polarized light, and in the second state, the circularly polarized light is a second linearly polarized light having a polarization direction perpendicular to the polarization direction of the first linearly polarized light in a plan view. When linearly polarized light enters the liquid crystal cell, in the first state, the linearly polarized light is converted into first circularly polarized light, and in the second state, the linearly polarized light is converted into first circularly polarized light. An optical element that converts the polarized light into a second circularly polarized light that rotates in the opposite direction to the direction of rotation of the polarized light.

(2) In addition to the configuration of (1), an embodiment of the present invention is an optical element in which the liquid crystal cell further includes a first weakly anchored horizontal alignment film disposed between the first substrate and the liquid crystal layer, and a second weakly anchored horizontal alignment film disposed between the liquid crystal layer and the second substrate, the electrodes include a first comb electrode disposed on the first substrate such that the comb teeth of a pixel electrode and a common electrode are fitted together, and the electrodes include a second comb electrode disposed on the second substrate such that the comb teeth of a pixel electrode and a common electrode are fitted together, and the extension direction of the first comb electrode is oblique to the extension direction of the second comb electrode in a plan view.

(3) Furthermore, in an embodiment of the present invention, in addition to the configuration of (1) above, the liquid crystal cell further includes a weakly anchored horizontal structure disposed between the first substrate and the liquid crystal layer. an alignment film; and a vertical alignment film disposed between the liquid crystal layer and the second substrate; a first comb-teeth electrode provided so that the comb-teeth of the comb-teeth fit into each other; and a comb-teeth-shaped pixel electrode and a common electrode superimposed on the first comb-teeth electrode via an insulating layer. has a second comb-teeth electrode provided so that the comb-teeth fit into each other, and in plan view, the extending direction of the first comb-teeth electrode is the same as the extending direction of the second comb-teeth electrode. An optical element perpendicular to a direction.

(4) Further, in an embodiment of the present invention, in addition to the configuration of (1) above, the electrode has a comb-like pixel electrode and a common electrode on the first substrate, the comb-like teeth of which fit into each other. A first comb-shaped electrode is provided to intersect with each other, and a comb-shaped pixel electrode and a common electrode are overlapped with the first comb-shaped electrode via a first insulating layer, and the comb-shaped pixel electrode and the common electrode A second comb-teeth electrode is provided so that the comb-teeth fit into each other, and in the second substrate, the comb-teeth-shaped pixel electrode and the common electrode are arranged so that the comb-teeth fit into each other. The provided third comb-teeth electrode overlaps the third comb-teeth electrode via the second insulating layer, and the comb-teeth-shaped pixel electrode and the common electrode are arranged such that the comb-teeth fit into each other. a fourth comb-teeth electrode provided so as to intersect with each other; in plan view, the extending direction of the first comb-teeth electrode is orthogonal to the extending direction of the second comb-teeth electrode; The stretching direction of the third comb-teeth electrode is orthogonal to the stretching direction of the fourth comb-teeth electrode, and the stretching direction of the first comb-teeth electrode is the stretching direction of the third comb-teeth electrode. An optical element that is installed diagonally to the surface.

(5) In addition to the configuration of (1), an embodiment of the present invention is an optical element in which the liquid crystal cell further has a bistable alignment film having two stable alignment directions arranged between the first substrate and the liquid crystal layer, the electrodes have a first comb electrode on the first substrate, in which a comb-shaped pixel electrode and a common electrode are arranged so that their comb teeth fit together, and the electrodes have a second comb electrode on the second substrate, in which a comb-shaped pixel electrode and a common electrode are arranged so that their comb teeth fit together, and the extension direction of the first comb electrode is oblique to the extension direction of the second comb electrode in a plan view.

(6) Further, in an embodiment of the present invention, in addition to the configuration of (1) above, the liquid crystal cell further includes a first vertically aligned layer disposed between the first substrate and the liquid crystal layer. a second vertical alignment film disposed between the liquid crystal layer and the second substrate, and the electrode includes a planar first electrode on the first substrate; a second electrode that overlaps the first electrode with a first insulating layer interposed therebetween and is provided with a slit portion; in the second substrate, a planar third electrode; It has a fourth electrode that overlaps the third electrode through a layer and is provided with a slit portion, and in plan view, the extending direction of the slit portion provided in the second electrode is the same as that of the fourth electrode. An optical element arranged obliquely with respect to the extending direction of the slit section provided in the electrode.

(7) Furthermore, in one embodiment of the present invention, in addition to the configuration of (1), (2), (3), (4), (5), or (6), the refractive index anisotropy Δn of the liquid crystal layer is 0.12 or less.

(8) Furthermore, an embodiment of the present invention has the configuration of (1), (2), (3), (4), (5), (6), or (7) above. In addition, the 1/4 wavelength film is a first 1/4 wavelength film, and a second 1/4 wavelength film is further provided on the opposite side of the first 1/4 wavelength film from the liquid crystal cell. an optical element.

(9) In addition to the configuration of (8) above, one embodiment of the present invention is an optical element in which the first quarter-wave film has reverse wavelength dispersion characteristics.

(10) In addition to the configuration of (8) or (9) above, an embodiment of the present invention provides that the first 1/4 wavelength film has an in-plane retardation at a wavelength of 450 nm with respect to an in-plane retardation at a wavelength of 550 nm. An optical element having an internal phase difference of 0.7 times or more and 1 time or less.

(11) In addition to the configuration of (8), (9), or (10), an embodiment of the present invention provides an in-plane retardation at a wavelength of 550 nm of the first 1/4 wavelength film. An optical element having an in-plane retardation at a wavelength of 650 nm with respect to that of 1 to 1.3 times.

(12) In addition to the configuration of (8), (9), (10) or (11), an embodiment of the present invention is an optical element in which the in-plane retardation of the first quarter-wave film at a wavelength of 550 nm is 30 nm or more and 230 nm or less.

(13) In addition, in one embodiment of the present invention, in addition to the configuration of (8), (9), (10), (11), or (12), the second 1/4 wavelength film has flat wavelength dispersion characteristics.

(14) In addition, one embodiment of the present invention is an optical element having the configuration of (8), (9), (10), (11), (12) or (13) above, in which the in-plane retardation of the second 1/4 wavelength film at a wavelength of 550 nm is 110 nm or more and 175 nm or less.

(15) Further, other embodiments of the present invention include the above (1), the above (2), the above (3), the above (4), the above (5), the above (6), the above (7), the above (8), comprising the optical element described in (9), (10), (11), (12), (13), or (14), and a Pancharatnam Berry lens; Variable focus element.

(16) In addition to the configuration of (15) above, an embodiment of the present invention is a variable focus element, wherein the Pancharatnam Berry lens is disposed within the optical element.

(17) Another embodiment of the present invention is a head-mounted display comprising the variable focus element described in (15) or (16) above.

(18) Further, in another embodiment of the present invention, in addition to the configuration of (1) above, the liquid crystal cell further includes a first vertically aligned layer disposed between the first substrate and the liquid crystal layer. a second vertical alignment film disposed between the liquid crystal layer and the second substrate, the liquid crystal layer containing liquid crystal molecules having negative dielectric anisotropy, At least one of the first vertical alignment film and the second vertical alignment film is an optical element that controls the tilt direction of the liquid crystal molecules in a state where no voltage is applied.

(19) In addition to the configuration of (18), one embodiment of the present invention is an optical element in which the electrode has a planar electrode on at least one of the first substrate and the second substrate, and an electrode that overlaps the planar electrode via an insulating layer and has a slit portion.

(20) Further, an embodiment of the present invention is an optical element, in addition to the configuration described in (18) or (19) above, wherein the pitch of the electrodes provided with the slit portions is 1 μm or more and 5 μm or less.

(21) Further, in an embodiment of the present invention, in addition to the configuration of (18), (19), or (20), at least one of the first vertical alignment film and the second vertical alignment film is provided. is an optical element that is a vertical alignment film with weak anchoring.

(22) In addition to the configuration described in (18), (19), (20), or (21), an embodiment of the present invention provides retardation of the liquid crystal layer in a voltage applied state at a wavelength of 550 nm. An optical element in which Δnd is 180 nm or more and 280 nm or less.

(23) In addition to the above (18), (19), (20), (21), or (22), an embodiment of the present invention provides a refractive index anisotropy of the liquid crystal layer. An optical element having a property Δn of 0.12 or less.

(24) In addition to the configuration of (18), (19), (20), (21), (22), or (23), an embodiment of the present invention may include the optical element The light incident on the optical element is circularly polarized.

(25) Further, other embodiments of the present invention are described in (18), (19), (20), (21), (22), (23), or (24) above. and a Pancharatnam Berry lens.

(26) In addition to the configuration of (25), one embodiment of the present invention is a variable focus element, in which the Pancharatnam Berry lens is disposed within the optical element.

(27) Another embodiment of the present invention is a head-mounted display comprising the variable focus element described in (25) or (26) above.

According to the present invention, an optical element that can switch between polarization modulation and non-polarization modulation over a wide band and that can be made thin, a variable focus element including the optical element, and a head mounted display including the variable focus element. can be provided.

1 is a schematic cross-sectional view of an optical element according to Embodiment 1. FIG. 1 is a schematic perspective view of a liquid crystal cell included in the optical element according to Embodiment 1. FIG. 2 is a schematic diagram illustrating the orientation of liquid crystal molecules in a first state and a second state of the optical element according to Embodiment 1. FIG. FIG. 2 is a schematic diagram illustrating polarization states of the optical element according to Embodiment 1 in a first state and a second state. FIG. 3 is a diagram showing an example of the axial orientation of the optical element according to the first embodiment. 3 is a diagram showing a Stokes plot of each layer in a first state of the optical element according to Embodiment 1. FIG. 3 is a schematic cross-sectional view of an optical element according to Comparative Form 1. FIG. FIG. 11 is a schematic cross-sectional view of an optical element according to Comparative Example 2. 3 is a graph showing an example of wavelength dispersion of Stokes parameter S3 during modulation of optical elements according to Embodiment 1, Comparative Form 1, and Comparative Form 2. 3 is a schematic cross-sectional view of a liquid crystal cell included in an optical element according to Embodiment 2. FIG. FIG. 3 is a schematic perspective view of a liquid crystal cell included in an optical element according to a second embodiment. 7 is a schematic plan view showing the direction of an electric field applied to an optical element according to Embodiment 2. FIG. 7 is a diagram showing an example of an axial orientation of an optical element according to Embodiment 2. FIG. FIG. 7 is a schematic perspective view of a liquid crystal cell included in an optical element according to Embodiment 3. 11A to 11C are schematic diagrams illustrating the alignment of liquid crystal molecules in a first state and a second state of an optical element according to a third embodiment. FIG. 7 is a schematic perspective view of a liquid crystal cell included in an optical element according to a fourth embodiment. FIG. 7 is a schematic cross-sectional view of a liquid crystal cell included in an optical element according to Embodiment 5. FIG. 7 is a schematic perspective view of a liquid crystal cell included in an optical element according to Embodiment 5. 7 is a diagram showing an example of the axial orientation of an optical element according to Embodiment 5. FIG. FIG. 7 is a schematic diagram illustrating the orientation of liquid crystal molecules in a first state and a second state of an optical element according to Embodiment 5. FIG. 7 is a schematic cross-sectional view of an optical element according to Embodiment 6. FIG. 7 is a schematic perspective view of a liquid crystal cell included in an optical element according to a sixth embodiment. FIG. 7 is a diagram showing an example of the axial orientation of an optical element according to Embodiment 6. FIG. 7 is a schematic cross-sectional view of a variable focus element according to Embodiment 7. 12 is an example of a schematic cross-sectional view of a PB lens included in a variable focus element according to Embodiment 7. FIG. FIG. 7 is a schematic cross-sectional view of a variable focus element according to Modification 1 of Embodiment 7. FIG. 7 is an enlarged schematic cross-sectional view of a variable focus element according to Modification 1 of Embodiment 7. FIG. 7 is a schematic plan view showing an orientation pattern of a PB lens included in a variable focus element according to Modification 1 of Embodiment 7; FIG. 7 is a schematic cross-sectional view illustrating a detailed configuration of a variable focus element according to Modification 1 of Embodiment 7; FIG. 7 is a diagram illustrating the polarization state in the F-2.5 mode of the variable focus element according to Modification 1 of Embodiment 7. FIG. 8 is a schematic cross-sectional view of a head-mounted display according to Embodiment 8. FIG. 13 is a schematic perspective view showing an example of the appearance of a head mounted display according to an eighth embodiment. 3 is a graph explaining the voltage applied to the optical element according to Example 1. FIG. 3 is a graph showing the Stokes parameter S3 at the time of non-modulation with respect to the retardation of the liquid crystal layer included in the optical element according to Example 1. FIG. 3 is a graph showing the Stokes parameter S3 during modulation with respect to the retardation of the liquid crystal layer included in the optical element according to Example 1. FIG. 11 is a graph showing the Stokes parameter S3 in a non-modulated state versus the twist angle of a liquid crystal layer included in the optical element according to Example 1. 3 is a graph showing the Stokes parameter S3 during modulation with respect to the twist angle of the liquid crystal layer included in the optical element according to Example 1. FIG. 11 is a graph showing the Stokes parameter S3 in a non-modulated state versus the azimuth angle of the slow axis of a quarter-wave film with reverse wavelength dispersion included in the optical element according to Example 1. 3 is a graph showing the Stokes parameter S3 during modulation with respect to the azimuth angle of the slow axis of the quarter-wavelength film with reverse wavelength dispersion included in the optical element according to Example 1. FIG. 3 is a graph showing the Stokes parameter S3 at the time of non-modulation with respect to the phase difference of a quarter-wavelength film with reverse wavelength dispersion included in the optical element according to Example 1. FIG. 3 is a graph showing the Stokes parameter S3 during modulation with respect to the phase difference of a quarter-wavelength film with reverse wavelength dispersion included in the optical element according to Example 1. FIG. 3 is a graph showing the Stokes parameter S3 at the time of non-modulation with respect to the azimuth angle of the slow axis of the quarter-wavelength film with flat wavelength dispersion included in the optical element according to Example 1. FIG. 3 is a graph showing the Stokes parameter S3 at the time of modulation with respect to the azimuth angle of the slow axis of the quarter-wavelength film with flat wavelength dispersion included in the optical element according to Example 1. FIG. 3 is a graph showing the Stokes parameter S3 at the time of non-modulation with respect to the phase difference of a quarter-wavelength film with flat wavelength dispersion included in the optical element according to Example 1. FIG. 11 is a graph showing the Stokes parameter S3 during modulation versus the phase difference of a quarter-wave film with flat wavelength dispersion included in the optical element according to Example 1. 3 is a schematic cross-sectional view of an optical element according to Comparative Example 1. FIG. 3 is a schematic cross-sectional view of an optical element according to Comparative Example 2. FIG. 11 is a graph showing chromatic dispersion of the Stokes parameter S3 during modulation for the optical elements according to Example 1, Comparative Example 1, and Comparative Example 2. 3 is a graph showing the wavelength dispersion of the Stokes parameter S3 of the optical elements according to Example 1, Comparative Example 1, and Comparative Example 2 at the time of non-modulation. 3 is a graph showing the wavelength dispersion of the Stokes parameter S3 during modulation of the optical elements according to Example 1, Example 2, and Comparative Example 1. 3 is a graph showing the wavelength dispersion of the Stokes parameter S3 of the optical elements according to Example 1, Example 2, and Comparative Example 1 at the time of non-modulation. FIG. 7 is a diagram illustrating the alignment direction of a bistable alignment film included in the optical element according to Example 4-1. FIG. 4 is a diagram illustrating the alignment direction of a bistable alignment film included in the optical element according to Example 4-2. 7 is a graph illustrating the applied voltage in the first state of the optical element according to Example 5. 3 is a graph showing the wavelength dispersion of the Stokes parameter S3 during modulation of the optical elements according to Example 1, Example 2, Example 5, Comparative Example 1, and Comparative Example 2. 3 is a graph showing the chromatic dispersion of the Stokes parameter S3 of the optical elements according to Example 1, Example 2, Example 5, Comparative Example 1, and Comparative Example 2 at the time of non-modulation. 11 is a graph showing chromatic dispersion of the Stokes parameter S3 during modulation for the optical elements according to Example 1, Example 2, Example 5, Example 6, Comparative Example 1, and Comparative Example 2. 3 is a graph showing the wavelength dispersion of the Stokes parameter S3 of the optical elements according to Example 1, Example 2, Example 5, Example 6, Comparative Example 1, and Comparative Example 2 at the time of non-modulation. 7 is a diagram showing the axial orientation of an optical element included in a variable focus element according to Example 7. FIG. FIG. 7 is a schematic diagram illustrating a first alignment process in the manufacturing process of a variable focus element according to Example 7. FIG. 7 is a schematic diagram illustrating a second alignment process in the manufacturing process of a variable focus element according to Example 7. FIG. 7 is a schematic diagram illustrating a third alignment process in the manufacturing process of a variable focus element according to Example 7. FIG. 7 is a schematic diagram illustrating a fourth alignment process in the manufacturing process of a variable focus element according to Example 7. FIG. 7 is a schematic cross-sectional view of an optical element according to Embodiment 9. FIG. 9 is a schematic cross-sectional view of a liquid crystal cell included in an optical element according to Embodiment 9. FIG. 9 is a schematic diagram illustrating the orientation of liquid crystal molecules in a first state and a second state of an optical element according to Embodiment 9. FIG. 7 is a diagram showing a Stokes plot of each layer in a first state of the optical element according to Embodiment 9. 13A to 13C are schematic diagrams illustrating the polarization state of the optical element according to the ninth embodiment in a first state. 10 is a schematic cross-sectional view of an optical element according to Embodiment 10. FIG. 10 is a schematic cross-sectional view of a liquid crystal cell included in an optical element according to Embodiment 10. FIG. FIG. 7 is a schematic diagram illustrating the orientation of liquid crystal molecules in a first state and a second state of the optical element according to Embodiment 10. FIG. 7 is a schematic cross-sectional view of an optical element according to Embodiment 11. FIG. 7 is a schematic cross-sectional view of a liquid crystal cell included in an optical element according to Embodiment 11. FIG. 7 is a schematic diagram illustrating the orientation of liquid crystal molecules in a first state and a second state of an optical element according to Embodiment 11. FIG. FIG. 7 is a schematic cross-sectional view of an optical element according to Embodiment 12. FIG. 7 is a schematic cross-sectional view of a liquid crystal cell included in an optical element according to Embodiment 12. FIG. 7 is a schematic diagram illustrating the orientation of liquid crystal molecules in a first state and a second state of an optical element according to Embodiment 12. 13 is a schematic cross-sectional view of a variable focus element according to a modification of Embodiment 13. FIG. FIG. 23 is an enlarged schematic cross-sectional view of a variable focal length element according to a modified example of the thirteenth embodiment. FIG. 7 is a schematic diagram illustrating the orientation of liquid crystal molecules in a first state and a second state of an optical element according to a modification of Embodiment 13. FIG. 12 is a schematic cross-sectional view illustrating a detailed configuration of a variable focus element according to a modification of Embodiment 13. FIG. 12 is a diagram illustrating the polarization state in the F-2.5 mode of a variable focus element according to a modification of the thirteenth embodiment. 7 is a graph illustrating the applied voltage in the first state of the optical element according to Example 8. 7 is a graph illustrating the applied voltage in the second state of the optical element according to Example 8. 3 is a schematic cross-sectional view of an optical element according to Comparative Example 3. FIG. 3 is a schematic cross-sectional view of an optical element according to Comparative Example 4. FIG. 7 is a graph showing wavelength dispersion of Stokes parameter S3 during modulation of optical elements according to Example 8, Comparative Example 3, and Comparative Example 4. 12 is a graph showing the wavelength dispersion of the Stokes parameter S3 of optical elements according to Example 8, Comparative Example 3, and Comparative Example 4 at the time of non-modulation. 7 is a graph illustrating the applied voltage in the first state of the optical element according to Example 9. 12 is a graph illustrating the applied voltage in the second state of the optical element according to Example 9. 7 is a graph showing wavelength dispersion of Stokes parameter S3 during modulation of optical elements according to Example 8, Example 9, and Comparative Example 3. 7 is a graph showing the wavelength dispersion of the Stokes parameter S3 of the optical elements according to Example 8, Example 9, and Comparative Example 3 at the time of non-modulation. 12 is a graph illustrating the applied voltage in the first state of the optical element according to Example 10. 7 is a graph illustrating the applied voltage in the second state of the optical element according to Example 10. 13 is a graph showing the chromatic dispersion of the Stokes parameter S3 during modulation for the optical elements according to Examples 8 to 10 and Comparative Example 3. 13 is a graph showing the chromatic dispersion of the Stokes parameter S3 in the non-modulated state of the optical elements according to Examples 8 to 10 and Comparative Example 3. 12 is a graph illustrating the applied voltage in the first state of the optical element according to Example 11. 12 is a graph illustrating the applied voltage in the second state of the optical element according to Example 11. 13 is a graph illustrating an applied voltage in a first state of the optical element according to Example 12. 12 is a graph illustrating the applied voltage in the second state of the optical element according to Example 12. FIG. 13 is a diagram showing a simulation result of the viewing angle characteristics of the optical element of Comparative Example 3 in a non-modulated state. FIG. 13 is a diagram showing a simulation result of the viewing angle characteristics during modulation of the optical element of Comparative Example 3. FIG. 12 is a diagram showing simulation results of viewing angle characteristics of the optical element of Example 9 in non-modulation. FIG. 9 is a diagram showing simulation results of viewing angle characteristics during modulation of the optical element of Example 9. FIG. 12 is a diagram showing simulation results of viewing angle characteristics of the optical element of Example 12 in the non-modulated state. FIG. 13 is a diagram showing a simulation result of the viewing angle characteristics during modulation of the optical element of Example 12. FIG. 13 is a diagram showing simulation results of viewing angle characteristics of the optical element of Example 13 in non-modulation. FIG. 12 is a diagram showing simulation results of viewing angle characteristics during modulation of the optical element of Example 13.

Embodiments of the present invention will be described below. The present invention is not limited to the content described in the following embodiments, and design changes can be made as appropriate within the scope that satisfies the configuration of the present invention. In the following description, the same reference numerals will be used for the same parts or parts having similar functions in different drawings, and repeated explanations will be omitted as appropriate. Each aspect of the present invention may be combined as appropriate without departing from the gist of the present invention.

(Definition of terms)
In this specification, azimuth means the direction when the target direction is projected onto the substrate surface on the output side of the optical element, and is expressed by the angle (azimuth angle) between it and the reference azimuth. Ru. Here, the reference orientation (0°) is set to the direction when the alignment direction of the liquid crystal molecules on the first substrate side in the first state is projected onto the substrate surface on the output side of the optical element. That is, the azimuth angle of the alignment direction of liquid crystal molecules on the first substrate side in the first state is set to 0°. The azimuth angle is defined as a positive angle when counterclockwise from the reference azimuth, and a negative angle when clockwise from the reference azimuth. Both counterclockwise and clockwise represent rotation directions when the optical element is viewed from the output side. In addition, the azimuth angle represents a value measured when the optical element is viewed in plan from the output side.

In this specification, two straight lines (including axes, directions, and orientations) being orthogonal to each other means that they are orthogonal when the optical element is viewed in plan from the output side. Also, when one of two straight lines is provided diagonally with respect to the other straight line, it means that one straight line is provided diagonally with respect to the other straight line when the optical element is viewed from the output side in plan. means. Moreover, the angle formed by two straight lines means the angle formed by one straight line and the other straight line when the optical element is viewed in plan from the output side.

In this specification, two straight lines (including axes, directions, and orientations) being orthogonal means that the angle between them is 90°±3°, preferably 90°±1°, more preferably This means 90°±0.5°, particularly preferably 90° (completely orthogonal). Two straight lines being parallel means that the angle between them is 0°±3°, preferably 0°±1°, more preferably 0°±0.5°, particularly preferably 0° ° (perfectly parallel).

In this specification, in-plane retardation (in-plane phase difference) Rp is defined as Rp=(ns−nf)d. Further, the retardation Rth in the thickness direction is defined as Rth=(nz−(nx+ny)/2)d. ns refers to the larger one of nx and ny, and nf refers to the smaller one. In addition, nx and ny indicate the principal refractive index in the in-plane direction of the birefringent layer (including the retardation film and the liquid crystal layer), and nz indicates the principal refractive index in the out-of-plane direction, that is, the direction perpendicular to the plane of the birefringent layer. represents the principal refractive index, and d represents the thickness of the birefringent layer.

In this specification, the wavelength for measuring optical parameters such as the principal refractive index and phase difference is 550 nm unless otherwise specified.

Embodiments of the present invention will be described below. The present invention is not limited to the content described in the following embodiments, and design changes can be made as appropriate within the scope that satisfies the configuration of the present invention.

(Embodiment 1)
FIG. 1 is a schematic cross-sectional view of an optical element according to Embodiment 1. FIG. 2 is a schematic perspective view of a liquid crystal cell included in the optical element according to the first embodiment. FIG. 3 is a schematic diagram illustrating the orientation of liquid crystal molecules in the first state and the second state of the optical element according to the first embodiment. FIG. 4 is a schematic diagram illustrating polarization states of the optical element according to the first embodiment in the first state and the second state. FIG. 5 is a diagram showing an example of the axial orientation of the optical element according to the first embodiment.

As shown in FIGS. 1 to 5, the optical element 10 of the present embodiment includes a liquid crystal cell 11 including a first substrate 100, a liquid crystal layer 300, and a second substrate 200, and a liquid crystal cell 11 as the 1/4 wavelength film. The liquid crystal layer 300 includes liquid crystal molecules 310 twistedly aligned between the first substrate 100 and the second substrate 200. The liquid crystal cell 11 has an electrode 11E for applying voltage to the liquid crystal layer 300 on at least one of the first substrate 100 and the second substrate 200. The electrode 11E has a first state in which the liquid crystal molecules 311 on the first substrate 100 side are aligned in the first alignment direction 311A, and a first state in which the liquid crystal molecules 311 on the first substrate 100 side are aligned in the first alignment direction 311A in plan view. By applying a voltage to the liquid crystal layer 300, the liquid crystal layer 300 is arranged to be able to switch between a second state in which the liquid crystal layers are aligned in a second alignment direction 311B orthogonal to the liquid crystal layer 300. The switching between the first state and the second state is to control the polarization state of the light incident on the liquid crystal cell 11. When circularly polarized light enters the liquid crystal cell 11, in the first state, the polarization state of the light incident on the liquid crystal cell 11 is changed. The polarized light is converted to a first linearly polarized light, and in the second state, the circularly polarized light is converted to a second linearly polarized light having a polarization direction perpendicular to the polarization direction of the first linearly polarized light in a plan view. When linearly polarized light is incident on the liquid crystal cell 11, in the first state, the linearly polarized light is converted to first circularly polarized light, and in the second state, the linearly polarized light is converted to the first circularly polarized light. It is converted into a second circularly polarized light that rotates in the opposite direction to the direction of rotation. By adopting such an aspect, while suppressing the thickness of the optical element 10, it is possible to output the circularly polarized light that has entered the optical element 10 without modulating it, and to output it after modulating the circularly polarized light that has entered the optical element 10. It becomes possible to switch over a wide band between the two states. That is, it is possible to realize an optical element 10 that can switch between polarization modulation and non-polarization modulation over a wide band and can be made thinner.

In the first state, the liquid crystal molecules 311 on the first substrate 100 side are aligned in the first alignment direction 311A, and in the second state, the liquid crystal molecules 311 on the first substrate 100 side are aligned in the first alignment direction in plan view. They are arranged in a second orientation direction 311B orthogonal to the direction 311A. Here, the alignment direction of liquid crystal molecules on the first substrate side is the alignment direction of liquid crystal molecules horizontally aligned in the vicinity of the first substrate. More specifically, when the alignment film provided on the liquid crystal layer side of the first substrate is a horizontal alignment film, the alignment direction of liquid crystal molecules on the first substrate side is defined as the alignment direction of the liquid crystal molecules on the first substrate side of the liquid crystal layer. Refers to the alignment direction of liquid crystal molecules located in a location. When the alignment film provided on the liquid crystal layer side of the first substrate is a vertical alignment film, since the liquid crystal molecules located at the interface of the liquid crystal layer on the first substrate side are vertically aligned, the liquid crystal molecules on the first substrate side The alignment direction refers to the alignment direction of horizontally aligned liquid crystal molecules located inside the liquid crystal layer from the interface on the first substrate side.

Similarly, the alignment direction of liquid crystal molecules on the second substrate side is the alignment direction of liquid crystal molecules horizontally aligned in the vicinity of the second substrate. More specifically, when the alignment film provided on the liquid crystal layer side of the second substrate is a horizontal alignment film, the alignment direction of liquid crystal molecules on the second substrate side is defined as the alignment direction of the liquid crystal molecules on the second substrate side of the liquid crystal layer. Refers to the alignment direction of liquid crystal molecules located in a location. If the alignment film provided on the liquid crystal layer side of the second substrate is a vertical alignment film, the liquid crystal molecules located at the interface of the liquid crystal layer on the second substrate side are vertically aligned, so the liquid crystal molecules on the second substrate side The alignment direction refers to the alignment direction of horizontally aligned liquid crystal molecules located inside the liquid crystal layer from the interface on the second substrate side.

Here, the orientation direction of the liquid crystal molecules on the first substrate side and the orientation direction of the liquid crystal molecules on the second substrate side can be determined by measuring the liquid crystal cell with Axoscan (manufactured by Optoscience) and from the output Mueller matrix. can. Specifically, when positive type liquid crystal molecules are filled, the measurement is performed when no voltage is applied, and when negative type liquid crystal molecules are filled, the measurement is performed when voltage is applied (for example, 5 V). Furthermore, the alignment direction of the liquid crystal molecules on the first substrate side and the alignment direction of the liquid crystal molecules on the second substrate side can also be determined by software that fits the cell thickness and twist angle of the liquid crystal in Axoscan.

Switching between the first state and the second state is to control the polarization state of light incident on the liquid crystal cell 11. When circularly polarized light is incident on the liquid crystal cell 11, in the first state, the circularly polarized light is converted into first linearly polarized light, and in the second state, the circularly polarized light is converted into the first linearly polarized light in plan view. is converted into a second linearly polarized light having a polarization direction perpendicular to the polarization direction of . When linearly polarized light is incident on the liquid crystal cell 11, in the first state, the linearly polarized light is converted into first circularly polarized light, and in the second state, the linearly polarized light is converted into the rotation direction of the first circularly polarized light. It is converted into a second circularly polarized light that rotates in the opposite direction.

Here, when circularly polarized light is incident on the liquid crystal cell 11, it is sufficient that the circularly polarized light is approximately converted into first linearly polarized light in the first state. For example, in the first state, the light may be first linearly polarized light around a wavelength of 550 nm (specifically, wavelengths of 530 nm or more, 570 nm), and may be elliptically polarized light at other wavelengths. Further, in the second state, it is sufficient that the circularly polarized light is approximately converted into the second linearly polarized light. For example, in the second state, the light may be second linearly polarized light around a wavelength of 550 nm (specifically, a wavelength of 530 nm or more, 570 nm), and may be elliptically polarized light at other wavelengths.

Further, when linearly polarized light is incident on the liquid crystal cell 11, it is sufficient that the linearly polarized light is approximately converted into first circularly polarized light in the first state. For example, in the first state, the light may be first circularly polarized light around a wavelength of 550 nm (specifically, a wavelength of 530 nm or more, 570 nm), and may be elliptically polarized light at other wavelengths. Furthermore, in the second state, it is sufficient that the linearly polarized light is approximately converted into the second circularly polarized light. For example, in the second state, the light may be second circularly polarized light around a wavelength of 550 nm (specifically, a wavelength of 530 nm or more, 570 nm), and may be elliptically polarized light at other wavelengths.

In this embodiment, a case will be described in which circularly polarized light is incident on the liquid crystal cell 11, but similar effects can be obtained when linearly polarized light is incident on the liquid crystal cell 11.

The liquid crystal cell 11 includes a first substrate 100, a liquid crystal layer 300, and a second substrate 200 in this order. In the optical element 10, switching between the first state and the second state is achieved by generating electric fields in two directions in the in-plane direction in at least one of the first substrate 100 and the second substrate 200. It makes it possible.

For example, a weak anchoring alignment film with an alignment regulating force as close to 0 as possible is arranged between the first substrate 100 and the liquid crystal layer 300 and at least one between the second substrate 200 and the liquid crystal layer 300. By doing so, it is possible to switch between the first state and the second state. Specifically, examples include using an alignment film called a slide film that maintains the alignment of liquid crystal molecules, and using an alignment film that has alignment regulating force in two directions, an azimuth angle of 0° and an azimuth angle of 90°. Details will be explained below.

As shown in FIG. 1, it is preferable that the optical element 10 of this embodiment further includes a second quarter wavelength film 13 on the opposite side of the first quarter wavelength film 12 from the liquid crystal cell 11. . By adopting such an aspect, polarization modulation and polarization non-modulation can be switched over a wider band. Below, an embodiment will be described in which the optical element 10 includes a liquid crystal cell 11, a first quarter-wavelength film 12, and a second quarter-wavelength film 13 in order from the incident side to the output side.

2, the liquid crystal cell 11 further includes a first weak anchoring horizontal alignment film 411 disposed between the first substrate 100 and the liquid crystal layer 300, and a second weak anchoring horizontal alignment film 421 disposed between the liquid crystal layer 300 and the second substrate 200. The electrode 11E includes a first comb electrode 120 on the first substrate 100, in which a comb-shaped pixel electrode and a common electrode are arranged so that their comb teeth fit together, and a second comb electrode 220 on the second substrate 200, in which a comb-shaped pixel electrode and a common electrode are arranged so that their comb teeth fit together. In a plan view, the extension direction 120A of the first comb electrode 120 is obliquely arranged with respect to the extension direction 220A of the second comb electrode 220.

By adopting such an aspect, when the first comb-shaped electrode 120 is in a non-voltage applied state and the second comb-shaped electrode 220 is in a voltage-applied state, the circularly polarized light incident on the liquid crystal cell 11 (for example, After passing through the liquid crystal cell 11, the right-handed circularly polarized light becomes first linearly polarized light. That is, the first state can be realized. Furthermore, the first linearly polarized light passes through the first 1/4 wavelength film 12 and the second 1/4 wavelength film 13, thereby becoming circularly polarized light whose polarization state is different from that of the circularly polarized light incident on the liquid crystal cell 11. (for example, left-handed circularly polarized light). In this way, in the first state, the circularly polarized light incident on the optical element 10 is converted into circularly polarized light with a different polarization state (for example, right-handed circularly polarized light is converted into left-handed circularly polarized light), and the output polarization modulation is broadband. It is realized by

Further, when the first comb-teeth electrode 120 is in a voltage applied state and the second comb-teeth electrode 220 is in a non-voltage applied state, the circularly polarized light (for example, right-handed circularly polarized light) incident on the liquid crystal cell 11 is 11, it becomes second linearly polarized light having a polarization direction perpendicular to the polarization direction of the first linearly polarized light in plan view. That is, the second state can be realized. Further, the second linearly polarized light passes through the first 1/4 wavelength film 12 and the second 1/4 wavelength film 13, thereby becoming circularly polarized light having the same polarization state as the circularly polarized light that entered the liquid crystal cell 11. The polarized light (for example, right-handed circularly polarized light) is emitted as it is in a wide band. In this way, in the second state, polarization non-modulation is realized in a wide band, in which the circularly polarized light incident on the optical element 10 is output while remaining in the same polarization state (for example, right-handed circularly polarized light).

In this embodiment, an embodiment will be described in which the liquid crystal cell 11, the first 1/4 wavelength film 12, and the second 1/4 wavelength film 13 are provided in order from the incident side to the output side. The stacking order may be reversed. Specifically, from the incident side to the output side, the second 1/4 wavelength film 13, the first 1/4 wavelength film 12, and the liquid crystal cell 11 It may also have the following. Also in this case, in the first state, the circularly polarized light incident on the optical element 10 is converted into circularly polarized light with a different polarization state (for example, right-handed circularly polarized light is converted into left-handed circularly polarized light), and the output polarization modulation is broadband. In the second state, polarization non-modulation is realized in a wide band in which the circularly polarized light incident on the optical element 10 is outputted in the same polarization state (for example, as right-handed circularly polarized light). In addition, when the lamination order is reversed, the slow axis 12A of the first quarter wavelength film 12 and the slow axis 13A of the second quarter wavelength film 13 are adjusted as appropriate.

The liquid crystal layer 300 contains liquid crystal molecules 310 that are twistedly aligned between the first substrate 100 and the second substrate 200. In each of the first state and the second state, the liquid crystal molecules 310 are twisted and oriented from the first substrate 100 side to the second substrate 200 side.

The twisted orientation of the liquid crystal molecules 310 can be achieved, for example, by adding a chiral agent to the liquid crystal material. The chiral agent is not particularly limited, and conventionally known ones can be used. As the chiral agent, for example, S-811 (manufactured by Merck & Co., Ltd.) can be used.

In plan view, the angle between the orientation direction (first orientation direction) 311A of the liquid crystal molecules 311 on the first substrate 100 side in the first state and the orientation direction 312A of the liquid crystal molecules 312 on the second substrate 200 side is 57. It is preferably 63° or more and 75° or less, still more preferably 66° or more and 72° or less. By adopting such an aspect, polarization modulation and polarization non-modulation can be switched over a wider band. Hereinafter, in plan view, the angle between the orientation direction of liquid crystal molecules on the first substrate side and the orientation direction of liquid crystal molecules on the second substrate side is also referred to as a twist angle.

In a plan view, the angle between the alignment direction (second alignment direction) 311B of the liquid crystal molecules 311 on the first substrate 100 side in the second state and the alignment direction 312B of the liquid crystal molecules 312 on the second substrate 200 side is preferably 57° or more and 82° or less, more preferably 63° or more and 75° or less, and even more preferably 66° or more and 72° or less. By adopting such an embodiment, it is possible to effectively switch between polarization modulation and polarization non-modulation in a wide band. The twist angle in the first state and the twist angle in the second state may be the same or different, but it is preferable that they are the same.

In plan view, the angle α between the stretching direction 120A and the stretching direction 220A (however, α is a real number greater than 0° and less than 90°), and the twist angle A of the liquid crystal molecules 310 included in the liquid crystal layer 300 are: In the first state and the second state, it is preferable that the following (Formula AX1) is satisfied, it is more preferable that the following (Formula AX2) is satisfied, and it is still more preferable that the following (Formula AX3) is satisfied. By adopting such an aspect, polarization modulation and polarization non-modulation can be effectively switched over a wide band.
85°-A≦α≦95°-A (Formula AX1)
88°-A≦α≦92°-A (Formula AX2)
α=90°-A (Formula AX3)

The twist angle A is preferably 60° or more and 80° or less, more preferably 64° or more and 76° or less, and even more preferably 68° or more and 72° or less. By adopting such an aspect, polarization modulation and polarization non-modulation can be switched more effectively over a wide band.

The azimuth angle of the stretching direction 120A is 0°, the azimuth angle of the stretching direction 220A is 160° (that is, the angle α between the stretching direction 120A and the stretching direction 220A is 20° in plan view), and the liquid crystal molecules 310 When the twist angle A is 70° and the liquid crystal layer 300 contains positive liquid crystal molecules 310, as shown in FIGS. 3 to 5, the first comb-shaped electrode 120 is When the second comb-teeth electrode 220 is in a voltage applied state, the azimuth angle of the alignment direction 311A of the liquid crystal molecules 311 on the first substrate 100 side is 0°, and the azimuth angle of the alignment direction 311A of the liquid crystal molecules 312 on the second substrate 200 side is A first state in which the azimuth angle of the alignment direction 312A is 70° can be realized. Further, when the first comb-teeth electrode 120 is in a voltage applied state and the second comb-teeth electrode 220 is in a no-voltage applied state, the azimuth angle of the alignment direction 311B of the liquid crystal molecules 311 on the first substrate 100 side is 90°, and the azimuth angle of the alignment direction 312B of the liquid crystal molecules 312 on the second substrate 200 side is 160°.

When the liquid crystal layer 300 contains negative type liquid crystal molecules 310, when the first comb electrode 120 is in a voltage applied state and the second comb electrode 220 is in a voltage non-applied state, a first state can be realized in which the azimuth angle of the alignment direction 311A of the liquid crystal molecules 311 on the first substrate 100 side is 0° and the azimuth angle of the alignment direction 312A of the liquid crystal molecules 312 on the second substrate 200 side is 70°. When the first comb electrode 120 is in a voltage non-applied state and the second comb electrode 220 is in a voltage applied state, a second state can be realized in which the azimuth angle of the alignment direction 311B of the liquid crystal molecules 311 on the first substrate 100 side is 90° and the azimuth angle of the alignment direction 312B of the liquid crystal molecules 312 on the second substrate 200 side is 160°.

FIG. 6 is a diagram showing a Stokes plot of each layer in the first state of the optical element according to the first embodiment. FIG. 6 shows the polarization state (role of each layer) when light passes through each layer in the first state. The principle of polarization modulation of the optical element 10 according to Embodiment 1 will be explained in detail using the Poincaré sphere shown in FIG.

As shown in (1) of FIG. 6, right-handed circularly polarized light (S3=+1) enters the liquid crystal cell 11.

After passing through the liquid crystal cell 11 twisted by 70°, the light is once converted into the polarization state shown in the plot (2) of FIG. The points in each plot represent plots of different wavelengths from 380 nm to 780 nm. Wavelengths around 550 nm are linearly polarized light (on the equator on the Poincare sphere), but other wavelengths are plotted in the northern hemisphere of the Poincare sphere and are elliptically polarized light.

Thereafter, it passes through the first quarter-wavelength film 12 (specifically, a quarter-wavelength film with reverse wavelength dispersion), resulting in the plot shown in FIG. 6 (3).

Furthermore, when it passes through the second quarter-wave film 13 (specifically, a quarter-wave film with flat wavelength dispersion), almost all wavelengths are emitted as left-handed circularly polarized light (south pole position on the Poincaré sphere), as shown in plot (4) of Figure 6. In other words, it can be seen that modulation from right-handed circularly polarized light to left-handed circularly polarized light has occurred.

Similarly, in the second state (non-modulated), the light becomes linearly polarized once after passing through the liquid crystal cell 11 twisted by 70°. However, since the entire orientation of the liquid crystal cell 11 is rotated by 90 degrees, the linearly polarized light differs from the first state (during modulation) by about 90 degrees. Then, after passing through the first 1/4 wavelength film 12 and the second 1/4 wavelength film 13, all wavelengths become right-handed circularly polarized light. That is, right-handed circularly polarized light can be emitted as right-handed circularly polarized light, and is not modulated.

In this way, the first state and the second state have the same orientation of the liquid crystal molecules 310, which is 70° twist, but the entire system is different by 90°. By using the optical element 10 of this embodiment, it is possible to reversibly switch between two states, the first state and the second state. A switchable half wave plate (sHWP) element can be realized.

Here, when attempting to realize sHWP with a single liquid crystal layer, a configuration of the optical element 10R1 of Comparative Form 1 using a liquid crystal cell 11R1 including a TN liquid crystal layer 300R1 twisted by 90° as shown in FIG. 7 is considered. It will be done. More specifically, the optical element 10R1 of Comparative Form 1 includes a quarter-wavelength film 14R whose slow axis has an azimuth angle of 75°, and a half-wavelength film whose slow axis has an azimuth angle of 15°. 15R, the liquid crystal cell 11R1, the 1/2 wavelength film 16R whose slow axis has an azimuth of -75°, and the 1/4 wavelength film 17R whose slow axis has an azimuth of -15°. Be prepared. FIG. 7 is a schematic cross-sectional view of an optical element according to Comparative Form 1.

In addition, when attempting to realize sHWP with two liquid crystal layers, an optical system of comparative form 2 in which a TN liquid crystal layer 300R2 with a 70° twist and a TN liquid crystal layer 300R3 with a -70° twist are laminated, as shown in FIG. A configuration of the element 10R2 is considered. FIG. 8 is a schematic cross-sectional view of an optical element according to Comparative Form 2.

Figure 9 is a graph showing an example of the wavelength dispersion of the Stokes parameter S3 during modulation for the optical elements according to embodiment 1, comparative embodiment 1, and comparative embodiment 2. Figure 9 shows the wavelength dependency of the polarization state of the emitted light when right-handed circularly polarized light (Stokes parameter S3 = +1) is incident. The closer S3 is to -1, the more it is converted to left-handed circularly polarized light. The closer it is to -1 over a wide wavelength range, the wider the bandwidth during modulation.

Although the optical element 10R1 of Comparative Form 1 is easy to design, it is difficult to widen the band as shown in FIG. 9 due to the influence of wavelength dispersion of the 90° twisted TN liquid crystal layer 300R1. Furthermore, although it is possible to widen the band with the optical element 10R2 of Comparative Form 2, it is difficult to make it thinner. In addition, when polarization is modulated (when converting right-handed circularly polarized light into left-handed circularly polarized light), the band is wide, but because it is driven by a vertical electric field, when polarization is not modulated (when right-handed circularly polarized light is directly emitted as right-handed circularly polarized light), , all liquid crystal molecules do not become vertically aligned when voltage is applied, and a wide band cannot be achieved due to the influence of residual retardation. On the other hand, the optical element 10 of this embodiment can switch left and right circularly polarized light over a wide band.

Patent Document 1 does not disclose polarization modulation characteristics at all. Patent Document 1 discloses a configuration of a single-layer TN liquid crystal layer, but in this configuration, polarization conversion is only performed appropriately at a specific wavelength during polarization modulation (inactive or voltage OFF in Patent Document 1). Therefore, it is not possible to achieve broadband polarization conversion. Moreover, although Patent Document 1 discloses a structure in which a plurality of liquid crystal layers are stacked, there are problems in that the manufacturing of the optical element becomes complicated and the thickness increases.

More specifically, in the single-layer configuration disclosed in Patent Document 1, the liquid crystal molecules are twisted 90° during polarization modulation, and are vertically oriented when a vertical electric field is applied during polarization non-modulation. Because the liquid crystal molecules are twisted 90° during polarization modulation, there is wavelength dependence, and polarization modulation cannot be achieved over a wide bandwidth. Even if it were possible to achieve polarization modulation over a wide bandwidth by adjusting the twist angle of the liquid crystal molecules or the cell thickness of the liquid crystal layer, it would be impossible to achieve polarization non-modulation over a wide bandwidth due to the influence of residual retardation by the liquid crystal molecules near the substrate during polarization non-modulation. In other words, it is not possible to achieve both polarization modulation and polarization non-modulation over a wide bandwidth.

On the other hand, in the optical element 10 of this embodiment, the liquid crystal molecules 310 maintain a 70° twisted state both during polarization modulation and non-polarization modulation, and these two states are obtained by rotating the entire system by 90°. Drive similarly. As a result, polarization modulation and non-polarization modulation can be achieved over a wide band.

The above-mentioned Patent Document 2 discloses a variable focus element in which tunability is imparted to the depth of focus by combining a plurality of sets (for example, 6 sets) of sHWP and Pancharatnam Berry (PB) lenses. There is. Therefore, when the sHWP becomes thicker, there is a problem that the entire variable focus element becomes thicker. In a configuration that realizes sHWP with two liquid crystal layers (70° twisted TN liquid crystal layer 300R2 and -70° twisted TN liquid crystal layer 300R3) as in Comparative Form 2 above, as many as 12 liquid crystal layers are required in 6 sets. Therefore, it is difficult to make the variable focus element thinner. Therefore, optical elements that are sHWPs are required to be thin and capable of realizing polarization modulation and non-modulation over a wide band.

The first substrate 100 includes a first support substrate 110 and a first comb-teeth electrode 120. The second substrate 200 includes a second support substrate 210 and a second comb-teeth electrode 220.

Examples of the first support substrate 110 and the second support substrate 210 include insulating substrates such as glass substrates and plastic substrates. Examples of the material for the glass substrate include glasses such as float glass and soda glass. Examples of the material of the plastic substrate include plastics such as polyethylene terephthalate, polybutylene terephthalate, polyether sulfone, polycarbonate, and alicyclic polyolefin.

The first comb-teeth electrode 120 has a first pixel electrode that is a comb-teeth electrode and a first common electrode that is a comb-teeth electrode. The second comb-teeth electrode 220 has a second pixel electrode that is a comb-teeth electrode and a second common electrode that is a comb-teeth electrode. The first pixel electrode and the second pixel electrode are hereinafter simply referred to as pixel electrodes, and the first common electrode and the second common electrode are also simply referred to as common electrode hereinafter. The pixel electrode and the common electrode are made of a transparent conductive material such as indium tin oxide (ITO), indium zinc oxide (IZO), zinc oxide (ZnO), or tin oxide (SnO), or an alloy thereof, using a sputtering method or the like. It can be formed by forming a single layer or a plurality of layers, and then patterning using a photolithography method.

The pitch of the first comb-teeth electrodes 120 is preferably 1 μm or more and 5 μm or less. By adopting such an aspect, it becomes possible to efficiently rotate the liquid crystal molecules 311 on the first substrate 100 side, and it becomes easier to obtain a uniform twisted orientation. Similarly, the pitch of the second comb-teeth electrodes 220 is preferably 1 μm or more and 5 μm or less. By adopting such an aspect, it becomes possible to efficiently rotate the liquid crystal molecules 312 on the second substrate 200 side, and it becomes easier to obtain a uniform twisted orientation. Here, the comb-teeth electrode has a structure in which linear electrode portions and slit portions are arranged alternately, and the pitch of the comb-teeth electrode is the sum of the widths of a set of linear electrode portions and slit portions. means.

In this specification, a voltage application state in which a voltage equal to or higher than a threshold is applied between a pair of common electrodes and a pixel electrode is also simply referred to as a "voltage application state" or "voltage application state", A state in which no voltage is applied (including a case in which a voltage below a threshold is applied) between the electrode and the electrode is also simply referred to as a "state in which no voltage is applied" or "when no voltage is applied."

The liquid crystal layer 300 contains a liquid crystal material, and by applying a voltage to the liquid crystal layer 300 and changing the orientation state of the liquid crystal molecules 310 in the liquid crystal material in response to the applied voltage, the polarization state of light passing through the liquid crystal layer 300 can be changed.

The liquid crystal molecule 310 may be a positive type liquid crystal molecule having a positive dielectric anisotropy (Δε) defined by the following formula (L), or a negative type liquid crystal molecule having a negative value. However, in this embodiment, positive-type liquid crystal molecules will be described as an example. Note that the long axis direction of the liquid crystal molecules is the slow axis direction. In addition, liquid crystal molecules are homogeneously aligned when no voltage is applied (no voltage applied state), and the direction of the long axis of the liquid crystal molecules in the no voltage applied state is also the initial orientation direction of the liquid crystal molecules. say.
Δε = (permittivity in the long axis direction of liquid crystal molecules) - (permittivity in the short axis direction of liquid crystal molecules) (L)

The retardation Δnd of the liquid crystal layer 300 in a state where no voltage is applied at a wavelength of 550 nm is preferably 180 nm or more and 280 nm or less, more preferably 200 nm or more and 260 nm or less, and preferably 220 nm or more and 240 nm or less. More preferred. By adopting such an aspect, polarization modulation and polarization non-modulation can be switched over a wider band.

The refractive index anisotropy Δn of the liquid crystal layer 300 is preferably 0.12 or less, more preferably 0.1 or less. By adopting such an aspect, it becomes possible to reduce the wavelength dispersion of the liquid crystal layer 300 itself, and it is possible to switch between polarization modulation and polarization non-modulation over a wider band.

The thickness d of the liquid crystal layer 300 is preferably 2 μm or more and 4.2 μm or less.

The first weak anchoring horizontal alignment film 411 and the second weak anchoring horizontal alignment film 421 will be described. The weakly anchoring alignment film refers to an alignment film that has a weak alignment regulating force for liquid crystal molecules. In the weakly anchored alignment film of this embodiment, viscoelasticity is a more important factor than simple anchoring energy (elasticity). The weakly anchoring alignment film may be, for example, a lubricating interface. As used herein, a lubricated interface is an interface induced by a lubricated interface induction region. The lubricating interface induction region refers to a region that is less ordered than the liquid crystal phase.

The lubricant interface inducing region may be a lubricious interface inducing liquid region. The lubricant interface-induced liquid region refers to a region of the lubricant interface-induced region that is in a liquid phase. The lubricant interface-inducing region is not limited to the lubricant interface-inducing liquid region (liquid phase), but also includes regions forming gel layers, regions with low order parameters (orientational order), regions with a decreased clearing point, and It may be an ordered region including a partially disordered region, a region including a highly motile region, or the like.

Preferably, the lubricant interface inducing region includes a lubricant interface inducing agent. The lubricant interface inducing region may contain only a lubricant interface inducing agent, or may contain a lubricious interface inducing agent and a liquid crystal component. Further, the lubricating interface inducer may be contained in the liquid crystal layer 300, may be introduced separately from the liquid crystal layer 300, may be included in the supporting substrate in advance, or may be chemically modified in advance to support the supporting substrate. It may be combined with the substrate.

The lubricating interface inducer is preferably a compound having a polar group, a polymerizable compound, a polymer compound, or an ionic liquid. The polymer compound preferably has at least one of two or more alkyl groups having different chain lengths, mesogenic groups, and photoisomerizable groups.

It is preferable that the liquid crystal layer 300 and the lubricant interface inducer exhibit a phase separation structure so that the liquid crystal layer 300 forms a liquid crystal phase and the lubricant interface inducer forms a liquid phase in the lubricant interface inducer region. The lubricating interface inducing agent may form a gel layer that is less ordered than the liquid crystal phase in the lubricious interface inducing region.

The weakly anchoring alignment film is preferably, for example, a slippery interface provided at the interface between the liquid crystal layer 300 and the lubricant interface induction region.

The first weakly anchored horizontal alignment film 411 and the second weakly anchored horizontal alignment film 421 are preferably slippery interfaces (slippery films). For example, by using a material in which dodecyl acrylate is mixed in the liquid crystal layer 300, a liquid phase of dodecyl acrylate (isotropic phase) forms a lubricant interface induction region, and the interface between the liquid crystal layer 300 and the lubricant interface induction region forms a slippery film.

By having such an interface, it is possible to orient the liquid crystal molecules in any direction using an electric field and maintain that state. Among slippery films, a film that remembers such orientation is sometimes called a slide film. Once the liquid crystal molecules are aligned in one direction, applying an electric field in another direction can change the alignment direction of the liquid crystal molecules. That is, multiple stable states can be created by an electric field. In this embodiment, a first state and a second state can be created. In addition to the materials exemplified above, materials described in JP 2006-084536A, WO 2017/034023, etc. can also be used.

The weakly anchoring alignment film may be, for example, an alignment film whose azimuthal anchoring energy is less than 1×10 ⁻⁴ J/m ² . The azimuthal anchoring energy can be calculated by various known methods, such as the torque balance method, the Nehruwall method, calculation from an electric field response threshold, calculation from a rotating magnetic field, and the like. Note that the azimuthal anchoring energy described in this specification is calculated using a calculation method from an electric field response threshold. Although the lower limit of the azimuthal anchoring energy of the weakly anchored alignment film is not particularly limited, the azimuthal anchoring energy of the weakly anchored alignment film is, for example, 1×10 ⁻¹⁰ J/m ² or more.

The azimuth anchoring energy of the first weak anchoring horizontal alignment film 411 is preferably 1×10 ⁻¹⁰ J/m ² or more and less than 1×10 ⁻⁴ J/m ² , more preferably 1×10 ⁻¹⁰ J/m ² or more and 1×10 ⁻⁵ J/m ² or less, and even more preferably 1×10 ⁻¹⁰ J/m ² or more and 1×10 ⁻⁶ J/m ² or less. By adopting such an embodiment, it is possible to effectively switch between polarization modulation and polarization non-modulation in a wide band.

The azimuthal anchoring energy of the second weak anchoring horizontal alignment film 421 is preferably 1×10 ⁻¹⁰ J/m ² or more and less than 1×10 ⁻⁴ J/m ² , and 1×10 ⁻ It is more preferably ¹⁰ J/m ² or more and 1×10 ⁻⁵ J/m ² or less, and even more preferably 1×10 ⁻¹⁰ J/m ² or more and 1×10 ⁻⁶ J/m ² or less. preferable. By adopting such an aspect, polarization modulation and non-polarization modulation can be effectively switched over a wide band.

A weakly anchored alignment film can be formed by performing an alignment process, or it can also be formed without performing an alignment process. Specifically, the weak anchoring alignment film may be a rubbed alignment film, a photo alignment film, or an untreated alignment film that has not been subjected to alignment treatment. .

A rubbing alignment film is produced by, for example, forming an alignment film material containing a rubbing alignment film polymer on a substrate, and then rolling a roller wrapped in cloth made of rayon, cotton, etc. at a constant rotation speed and the distance between the roller and the substrate. It is obtained by rotating the film in a maintained state and rubbing the surface of the film containing the rubbing alignment film polymer in a predetermined direction (rubbing method). By changing the conditions of the rubbing process, the azimuthal anchoring energy of the alignment film can be adjusted and a weakly anchored alignment film can be formed.

Examples of the polymer for the rubbed alignment film include polyimide. The rubbed alignment film polymers contained in the rubbed alignment film may be one type or two or more types.

A photo-aligned film can be obtained, for example, by forming an alignment film material containing a photo-alignable polymer with photofunctional groups on a substrate, and then irradiating the substrate with polarized ultraviolet light to generate anisotropy on the surface of the film containing the photo-alignable polymer (photo-alignment method). By changing the conditions of the photo-alignment process and the material structure, it is possible to adjust the azimuthal anchoring energy of the alignment film and form an alignment film with weak anchoring.

The photo-alignable polymer has, for example, at least one photo-functional group selected from a cyclobutane group, an azobenzene group, a chalcone group, a cinnamate group, a coumarin group, a stilbene group, a phenol ester group, and a phenylbenzoate group. Examples include polymers. The number of photo-alignable polymers contained in the photo-alignment film may be one type or two or more types. The photofunctional group possessed by the photoalignable polymer may be present in the main chain of the polymer, may be present in the side chain of the polymer, or may be present in both the main chain and the side chain of the polymer. .

The type of photoreaction of the above-mentioned photoalignable polymer is also not particularly limited, but includes photodecomposition type polymers, phototransposition type polymers (preferably photofries rearrangement type polymers), photoisomerization type polymers, photodimerization type polymers, and photocrosslinking type polymers. can be cited as a suitable example. Any of these can be used alone, or two or more types can be used in combination. Among these, from the viewpoint of alignment stability, photodegradable polymers whose reaction wavelength (main sensitivity wavelength) is around 254 nm and phototransposition polymers whose reaction wavelength (main sensitivity wavelength) is around 254 nm are particularly preferred. Photoisomerizable polymers and photodimerizable polymers having photofunctional groups in their side chains are also preferred.

The main chain structure of the photo-alignable polymer is not particularly limited, but preferred examples include polyamic acid structure, polyimide structure, poly(meth)acrylic acid structure, polysiloxane structure, polyethylene structure, polystyrene structure, and polyvinyl structure. can.

The untreated alignment film can be obtained, for example, by forming an alignment film material containing an alignment film polymer on a substrate. Examples of the alignment film polymer include polyimide and polyhexyl methacrylate. The alignment film polymer contained in the untreated alignment film may be one type or two or more types.

In addition to polyimide and polyhexyl methacrylate, the alignment film polymer contained in the untreated alignment film includes polymers described in International Publication No. 2017/034023, and among them, polyethylene glycol, polypropylene glycol, etc. Polyalkylene oxides such as are preferred.

The horizontal alignment film has a function of aligning liquid crystal molecules in the liquid crystal layer in the horizontal direction with respect to the surface of the horizontal alignment film when no voltage is applied. Here, the liquid crystal molecules are aligned horizontally with respect to the surface of the horizontal alignment film means that the pretilt angle of the liquid crystal molecules is 0° or more and 5° or less with respect to the surface of the horizontal alignment film, It means preferably 0° or more and 2° or less, more preferably 0° or more and 1° or less. The pretilt angle of liquid crystal molecules means the angle at which the long axis of the liquid crystal molecules is inclined with respect to the main surface of the alignment film when no voltage is applied to the liquid crystal layer.

In this specification, the alignment film provided between the first substrate 100 and the liquid crystal layer 300 is also referred to as a first alignment film 410, and the alignment film provided between the second substrate 200 and the liquid crystal layer 300 is also referred to as a second alignment film. It is also referred to as an alignment film 420.

The 1/4 wavelength film (specifically, the first 1/4 wavelength film 12 and the second 1/4 wavelength film 13) has an in-plane wavelength of 20 nm or more and 240 nm or less for light with a wavelength of at least 550 nm. Any material that provides a phase difference may be used.

Examples of the material for the quarter wavelength film include photopolymerizable liquid crystal materials. Examples of the structure of the photopolymerizable liquid crystal material include a structure having a photopolymerizable group such as an acrylate group or a methacrylate group at the end of the skeleton of a liquid crystal molecule.

A quarter wavelength film can be formed, for example, by the method described below. First, a photopolymerizable liquid crystal material is dissolved in an organic solvent such as propylene glycol monomethyl ether acetate (PGMEA). Next, the obtained solution is applied onto the surface of a substrate (for example, a polyethylene terephthalate (PET) film) to form a coating film of the solution. Thereafter, a 1/4 wavelength film is formed by sequentially performing pre-baking, light irradiation (for example, ultraviolet ray irradiation), and main baking on the coating film of this solution.

Alternatively, a liquid crystal polymer obtained by adding a chiral agent to the photopolymerizable liquid crystal material and polymerizing it in a 70° twisted state may be used as a 1/4 wavelength film.

As the 1/4 wavelength film, for example, a stretched polymer film can also be used. Examples of the material for the polymer film include cycloolefin polymer, polycarbonate, polysulfone, polyethersulfone, polyethylene terephthalate, polyethylene, polyvinyl alcohol, norbornene, triacetylcellulose, diacylcellulose, and the like.

It is preferable that the first quarter wavelength film 12 has reverse wavelength dispersion characteristics. By adopting such an aspect, polarization modulation and polarization non-modulation can be switched over a wider band. Here, in this specification, "wavelength dispersion of a retardation film" refers to the correlation between the absolute value of the retardation provided by the retardation film and the wavelength of incident light. In the visible light range, the property that the absolute value of the retardation imparted by a retardation film does not change even if the wavelength of incident light changes is called "flat wavelength dispersion property." In addition, in the visible light range, the property that the absolute value of the retardation imparted by a retardation film decreases as the wavelength of the incident light increases is called "positive wavelength dispersion property." The property that the absolute value of the retardation imparted by the retardation film increases as the retardation film increases is called "reverse wavelength dispersion property."

The in-plane retardation of the first quarter-wavelength film 12 at a wavelength of 450 nm relative to the in-plane retardation at a wavelength of 550 nm is preferably 0.7 times or more and 1 time or less. By adopting such an aspect, polarization modulation and polarization non-modulation can be switched over a wider band.

The in-plane retardation of the first quarter-wavelength film 12 at a wavelength of 650 nm relative to the in-plane retardation at a wavelength of 550 nm is preferably 1 time or more and 1.3 times or less. By adopting such an aspect, polarization modulation and polarization non-modulation can be switched over a wider band.

The in-plane retardation of the first quarter-wavelength film 12 at a wavelength of 550 nm is preferably 30 nm or more and 230 nm or less. By adopting such an aspect, polarization modulation and polarization non-modulation can be switched over a wider band.

When the azimuth angle of the alignment direction 311A of the liquid crystal molecules 311 on the first substrate 100 side in the first state is 0°, the light beam of the first 1/4 wavelength film 12 and the second 1/4 wavelength film 13 is The azimuth angle of the slow axis of the 1/4 wavelength film on the side far from the emission side (in this embodiment, the slow axis 12A of the first 1/4 wavelength film 12) is 48° or more and 66° or less. is preferred. By adopting such an aspect, polarization modulation and polarization non-modulation can be switched over a wider band.

The second quarter wavelength film 13 preferably has flat wavelength dispersion characteristics. By adopting such an aspect, polarization modulation and polarization non-modulation can be switched over a wider band.

The in-plane retardation of the second quarter-wavelength film 13 at a wavelength of 550 nm is preferably 110 nm or more and 175 nm or less. By adopting such an aspect, polarization modulation and polarization non-modulation can be switched over a wider band.

When the azimuth angle of the alignment direction 311A of the liquid crystal molecules 311 on the first substrate 100 side in the first state is 0°, the light beam of the first 1/4 wavelength film 12 and the second 1/4 wavelength film 13 is The azimuth angle of the slow axis of the 1/4 wavelength film on the side closer to the output side (in this embodiment, the slow axis 13A of the second 1/4 wavelength film 13) is 3° or more and 22° or less. is preferred. By adopting such an aspect, polarization modulation and polarization non-modulation can be switched over a wider band.

The angle between the slow axis 12A of the first quarter wavelength film 12 and the slow axis 13A of the second quarter wavelength film 13 is preferably 40° or more and 50° or less, and 42 It is more preferably 44° or more and 46° or less, even more preferably 45° or more, and particularly preferably 45°.

In this embodiment in which the liquid crystal layer 300 contains positive liquid crystal molecules 310, the orientation direction 311A of the liquid crystal molecules 311 on the first substrate 100 side in the first state is the extension of the first comb-teeth electrode 120 in plan view. It corresponds to direction 120A. Therefore, when the azimuth angle of the orientation direction 311A of the liquid crystal molecules 311 on the first substrate 100 side in the first state is 0°, for example, as shown in FIG. 5, the azimuth angle of the stretching direction 120A is 0°, The azimuth angle of the stretching direction 220A is 160°, the azimuth angle of the slow axis 12A of the first 1/4 wavelength film 12 is 57.2°, and the azimuth angle of the slow axis 13A of the second 1/4 wavelength film 13 is The azimuth angle can be set to 12.2°.

Preferably, the light incident on the optical element 10 is circularly polarized light. By adopting such an aspect, it is possible to realize the optical element 10 that can switch the polarization state of circularly polarized light.

(Embodiment 2)
In this embodiment, features unique to this embodiment will be mainly described, and descriptions of contents overlapping with the above-mentioned embodiment 1 will be omitted. This embodiment is substantially the same as embodiment 1, except that the configuration of the liquid crystal cell 11 is different.

FIG. 10 is a schematic cross-sectional view of a liquid crystal cell included in the optical element according to the second embodiment. FIG. 11 is a schematic perspective view of a liquid crystal cell included in the optical element according to the second embodiment. FIG. 12 is a schematic plan view showing the direction of an electric field applied to the optical element according to the second embodiment. FIG. 13 is a diagram showing an example of the axial orientation of the optical element according to the second embodiment.

The liquid crystal cell 11 of the optical element 10 of this embodiment further includes a weakly anchored horizontal alignment film 412 disposed between the first substrate 100 and the liquid crystal layer 300, and a vertical alignment film 422 disposed between the liquid crystal layer 300 and the second substrate 200, as shown in FIG. 10 and FIG. 11. The electrode 11E includes a first comb electrode 121 on the first substrate 100, in which a comb-shaped pixel electrode and a common electrode are arranged so that their comb teeth fit together, and a second comb electrode 122 that overlaps the first comb electrode 121 via an insulating layer 140 and is arranged so that the comb-shaped pixel electrode and the common electrode are arranged so that their comb teeth fit together. In a plan view, the extension direction 121A of the first comb electrode 121 is perpendicular to the extension direction 122A of the second comb electrode 122.

By adopting such an aspect, as shown in FIGS. 12 and 13, when the first comb-shaped electrode 121 is in a non-voltage state and the second comb-shaped electrode 122 is in a voltage-applied state, the liquid crystal The circularly polarized light (for example, right-handed circularly polarized light) incident on the cell 11 becomes the first linearly polarized light after passing through the liquid crystal cell 11. That is, the first state can be realized. Furthermore, the first linearly polarized light passes through the first 1/4 wavelength film 12 and the second 1/4 wavelength film 13, thereby becoming circularly polarized light whose polarization state is different from that of the circularly polarized light incident on the liquid crystal cell 11. (for example, left-handed circularly polarized light). In this way, in the first state, the circularly polarized light incident on the optical element 10 is converted into circularly polarized light with a different polarization state (for example, right-handed circularly polarized light is converted into left-handed circularly polarized light), and the output polarization modulation is broadband. It is realized by

Furthermore, when the first comb-teeth electrode 121 is in a voltage applied state and the second comb-teeth electrode 122 is in a non-voltage applied state, the circularly polarized light (for example, right-handed circularly polarized light) incident on the liquid crystal cell 11 is 11, it becomes second linearly polarized light having a polarization direction perpendicular to the polarization direction of the first linearly polarized light in plan view. That is, the second state can be realized. Further, the second linearly polarized light passes through the first 1/4 wavelength film 12 and the second 1/4 wavelength film 13, thereby becoming circularly polarized light having the same polarization state as the circularly polarized light that entered the liquid crystal cell 11. The polarized light (for example, right-handed circularly polarized light) is emitted as it is in a wide band. In this way, in the second state, polarization non-modulation is realized in a wide band, in which the circularly polarized light incident on the optical element 10 is output while remaining in the same polarization state (for example, right-handed circularly polarized light).

As shown in FIG. 10, the liquid crystal cell 11 of the present embodiment is a twisted HAN (Hybrid Aligned Nematic) cell, in which a first substrate 100, a weak anchoring film that is a slippery film, , a horizontal alignment film 412 , a liquid crystal layer 300 containing a chiral agent, a vertical alignment film 422 , and a second substrate 200 . The liquid crystal molecules 310 included in the liquid crystal layer 300 may be negative type liquid crystal molecules or positive type liquid crystal molecules, but in the embodiment, the liquid crystal layer 300 includes positive type liquid crystal molecules 310. This will be explained using an example.

As shown in FIG. 11, the first substrate 100 includes a first support substrate 110, a second comb-teeth electrode 122, an insulating layer 140, and a first comb-teeth electrode 121 in this order. The second substrate 200 includes a second support substrate 210 .

The insulating layer 140 has a function of insulating the first comb-teeth electrode 121 and the second comb-teeth electrode 122. As the insulating layer 140, an inorganic insulating film, an organic insulating film, or a laminate of the above organic insulating film and inorganic insulating film can be used. As the inorganic insulating film, for example, an inorganic film (relative dielectric constant ε=5 to 7) such as silicon nitride (SiN _x ) or silicon oxide (SiO ₂ ), or a laminated film thereof can be used. As the organic insulating film, for example, an organic film having a low dielectric constant (relative dielectric constant ε=2 to 5) such as a photosensitive acrylic resin, or a laminated film thereof can be used. More specifically, as the organic insulating film, organic films such as acrylic resin, polyimide resin, novolak resin, etc., and laminates thereof can be used.

The first comb-teeth electrode 121 has a first pixel electrode that is a comb-teeth electrode and a first common electrode that is a comb-teeth electrode. The second comb-teeth electrode 122 has a second pixel electrode that is a comb-teeth electrode and a second common electrode that is a comb-teeth electrode.

The pitch of the first comb-teeth electrodes 121 is preferably 1 μm or more and 5 μm or less. By adopting such an aspect, it becomes possible to efficiently rotate the liquid crystal molecules 311 on the first substrate 100 side, and it becomes easier to obtain a uniform twisted orientation. Similarly, the pitch of the second comb-teeth electrodes 122 is preferably 1 μm or more and 5 μm or less. By adopting such an aspect, it becomes possible to efficiently rotate the liquid crystal molecules 311 on the first substrate 100 side, and it becomes easier to obtain a uniform twisted orientation.

As shown in FIG. 12, when a voltage is applied to the second comb-teeth electrode 122 and no voltage is applied to the first comb-teeth electrode 121, an electric field is generated in the first electric field direction 120E1 (first state). When no voltage is applied to the second comb-teeth electrode 122 and a voltage is applied to the first comb-teeth electrode 121, an electric field is generated in the second electric field direction 120E2 (second state). In this manner, the optical element 10 of the second embodiment is capable of rotating the azimuth angle of the alignment direction of the liquid crystal molecules 311 on the first substrate 100 side by 90 degrees using an electric field.

The vertical alignment film 422 has a function of aligning liquid crystal molecules in the liquid crystal layer in a direction perpendicular to the surface of the vertical alignment film when no voltage is applied. Here, the liquid crystal molecules are aligned perpendicularly to the surface of the vertical alignment film means that the pretilt angle of the liquid crystal molecules is 86° or more and 90° or less with respect to the surface of the vertical alignment film, It means preferably 87° or more and 89° or less, more preferably 87.5° or more and 89° or less.

The vertical alignment film 422 is preferably a strong anchoring vertical alignment film. A strong anchoring alignment film refers to an alignment film that has a strong alignment control force for liquid crystal molecules, for example, an alignment film having an azimuthal anchoring energy of 1×10 ⁻⁴ J/m ² or more. There is no particular limit to the upper limit of the azimuthal anchoring energy of a strong anchoring alignment film, but the azimuthal anchoring energy of a strong anchoring alignment film is, for example, 1×10 ⁻¹ J/m ² or less.

The azimuthal anchoring energy of the vertical alignment film 422 is preferably 1×10 ⁻⁴ J/m ² or more and 1×10 ⁻¹ J/m ² or less. By adopting such an aspect, polarization modulation and polarization non-modulation can be switched over a wider band.

The weak anchoring horizontal alignment film 412 is preferably a slippery film. By adopting such an aspect, polarization modulation and polarization non-modulation can be switched over a wider band.

In the first embodiment, since the alignment films on both sides are weakly anchored, there is room for improvement in alignment disturbance and response speed. In this embodiment in which one side is vertically aligned (HAN structure), the vertical alignment film 422 is strongly anchored on one side, so that the alignment is easily stabilized, and the optical element 10 can have excellent reliability. In the case of the HAN structure, not only the azimuthal anchoring energy of the weakly anchored horizontal alignment film 412 but also the polar anchoring energy is important. Due to the HAN orientation, if the polar angle anchoring energy of the weakly anchoring horizontal alignment film 412 is small, it will be affected by the strong anchoring alignment film (vertical alignment film 422) on the second substrate 200 side, and the ideal HAN It becomes easy to collapse due to orientation.

Therefore, the polar angle anchoring energy of the weak anchoring horizontal alignment film 412 is preferably 1×10 ⁻⁵ J/m ² or more, more preferably 1×10 ⁻⁴ J/m ² or more. , more preferably 1×10 ⁻³ J/m ² or more. The upper limit of the polar angle anchoring energy of the weak anchoring horizontal alignment film 412 is not particularly limited, and the polar angle anchoring energy of the weak anchoring horizontal alignment film 412 is, for example, 1×10 ⁻¹ J/m ² It is as follows. Polar anchoring energy can be measured in a similar manner as azimuthal anchoring energy. Further, the polar anchoring energy of the alignment film can be adjusted in the same manner as the azimuthal anchoring energy.

The polar angle anchoring energy of the weak anchoring horizontal alignment film 412 is preferably 1×10 ⁻⁵ J/m ² or more and 1×10 ⁻¹ J/m 2 or less, and 1×10 ⁻⁴ J/m ² or more. It is more preferably 1×10 ⁻¹ J/m ² or more and 1×10 −1 J/m ² or less, and ^even more preferably 1×10 ⁻³ J/m 2 or more and 1×10 ⁻¹ J/m ² or less. By adopting such an aspect, it becomes easier to obtain an ideal HAN orientation.

In this embodiment in which the liquid crystal layer 300 contains positive liquid crystal molecules 310, the orientation direction 311A of the liquid crystal molecules 311 on the first substrate 100 side in the first state is the extension of the first comb-teeth electrode 121 in plan view. It corresponds to direction 121A. Therefore, when the azimuth angle of the alignment direction 311A of the liquid crystal molecules 311 on the first substrate 100 side in the first state is 0°, for example, as shown in FIG. The azimuth angle of the direction 122A is 90°, the azimuth angle of the slow axis 13A of the second 1/4 wavelength film 13 is 4°, and the azimuth angle of the slow axis 12A of the first 1/4 wavelength film 12 is It can be set at 49°.

(Embodiment 3)
In this embodiment, features unique to this embodiment will be mainly explained, and explanations of contents that overlap with those of Embodiments 1 and 2 will be omitted. This embodiment is substantially the same as Embodiment 1 except that the configuration of the liquid crystal cell 11 is different.

FIG. 14 is a schematic perspective view of a liquid crystal cell included in the optical element according to Embodiment 3. FIG. 15 is a schematic diagram illustrating the orientation of liquid crystal molecules in the first state and the second state of the optical element according to the third embodiment.

As shown in FIGS. 14 and 15, the electrode 11E included in the optical element 10 of this embodiment is formed by forming a comb-like pixel electrode and a common electrode on the first substrate 100 such that the comb-like teeth fit into each other. The first comb-shaped electrode 121 provided on the first comb-shaped electrode 121 overlaps the first comb-shaped electrode 121 via the first insulating layer 141, and the comb-shaped pixel electrode and the common electrode A second comb-shaped electrode 122 is provided so that the teeth fit into each other, and in the second substrate 200, the comb-shaped pixel electrode and the common electrode are arranged so that the comb teeth fit into each other. The provided third comb-shaped electrode 221 overlaps the third comb-shaped electrode 221 via the second insulating layer 241, and the comb-shaped pixel electrode and the common electrode are connected to each other's comb-shaped electrodes. It has a fourth comb-teeth electrode 222 that is provided so as to fit into each other. In plan view, the extending direction 121A of the first comb-teeth electrode 121 is perpendicular to the extending direction 122A of the second comb-teeth electrode 122, and the extending direction 221A of the third comb-teeth electrode 221 is perpendicular to the extending direction 122A of the second comb-teeth electrode 122. The extending direction 121A of the first comb-teeth electrode 121 is perpendicular to the extending direction 222A of the comb-teeth electrode 222, and is provided obliquely to the extending direction 221A of the third comb-teeth electrode 221.

By adopting such an aspect, as shown in FIG. 15, the first comb-teeth electrode 121 is in a non-voltage applied state, the second comb-teeth electrode 122 is in a voltage-applied state, and the third comb-teeth electrode 221 is in a voltage-applied state. When a voltage is applied to the fourth comb electrode 222 and no voltage is applied to the fourth comb electrode 222, the circularly polarized light (for example, right-handed circularly polarized light) incident on the liquid crystal cell 11 becomes the first linearly polarized light after passing through the liquid crystal cell 11. Become. That is, the first state can be realized. Furthermore, the first linearly polarized light passes through the first 1/4 wavelength film 12 and the second 1/4 wavelength film 13, thereby becoming circularly polarized light whose polarization state is different from that of the circularly polarized light incident on the liquid crystal cell 11. (for example, left-handed circularly polarized light). In this way, in the first state, the circularly polarized light incident on the optical element 10 is converted into circularly polarized light with a different polarization state (for example, right-handed circularly polarized light is converted into left-handed circularly polarized light), and the output polarization modulation is broadband. It is realized by

Furthermore, when the first comb electrode 121 is in a voltage applied state, the second comb electrode 122 is in a voltage unapplied state, the third comb electrode 221 is in a voltage unapplied state, and the fourth comb electrode 222 is in a voltage applied state, the circularly polarized light (e.g., right-handed circularly polarized light) incident on the liquid crystal cell 11 becomes a second linearly polarized light having a polarization direction perpendicular to the polarization direction of the first linearly polarized light in a planar view after passing through the liquid crystal cell 11. That is, the second state can be realized. Furthermore, the second linearly polarized light passes through the first quarter-wave film 12 and the second quarter-wave film 13, and is output in a wide band as circularly polarized light (e.g., right-handed circularly polarized light) having the same polarization state as the circularly polarized light incident on the liquid crystal cell 11. In this way, in the second state, polarization non-modulation is realized in a wide band in which the circularly polarized light incident on the optical element 10 is output in the same polarization state (e.g., right-handed circularly polarized light).

In this way, in the optical element 10 of this embodiment, a voltage is applied to both the first substrate 100 and the second substrate 200, and then the voltage is lowered to achieve the first and second states. In the first and second states, the electric field directions of both substrates differ by 90°. In this embodiment, the orientation of both the first substrate 100 and the second substrate 200 can be determined by voltage, thereby increasing the response speed.

As shown in FIG. 14, the first substrate 100 includes, in order, a first support substrate 110, a second comb-teeth electrode 122, a first insulating layer 141, and a first comb-teeth electrode 121. . The second substrate 200 includes, in order, a second support substrate 210, a third comb-shaped electrode 221, a second insulating layer 241, and a fourth comb-shaped electrode 222.

The first insulating layer 141 has a function of insulating the first comb tooth electrode 121 from the second comb tooth electrode 122. The second insulating layer 241 has a function of insulating the third comb tooth electrode 221 from the fourth comb tooth electrode 222. The first insulating layer 141 and the second insulating layer 241 can be the same as the insulating layer 140.

The first comb-teeth electrode 121 has a first pixel electrode that is a comb-teeth electrode and a first common electrode that is a comb-teeth electrode. The second comb-teeth electrode 122 has a second pixel electrode that is a comb-teeth electrode and a second common electrode that is a comb-teeth electrode. The third comb-teeth electrode 221 has a third pixel electrode that is a comb-teeth electrode and a third common electrode that is a comb-teeth electrode. The fourth comb-teeth electrode 222 has a fourth pixel electrode that is a comb-teeth electrode and a fourth common electrode that is a comb-teeth electrode.

The pitch of the first comb-teeth electrodes 121 is preferably 1 μm or more and 5 μm or less. By adopting such an aspect, it becomes possible to efficiently rotate the liquid crystal molecules 311 on the first substrate 100 side, and it becomes easier to obtain a uniform twisted orientation. Similarly, the pitch of the second comb-teeth electrodes 122 is preferably 1 μm or more and 5 μm or less. By adopting such an aspect, it becomes possible to efficiently rotate the liquid crystal molecules 311 on the first substrate 100 side, and it becomes easier to obtain a uniform twisted orientation.

The pitch of the third comb-teeth electrode 221 is preferably 1 μm or more and 5 μm or less. By adopting such an aspect, it becomes possible to efficiently rotate the liquid crystal molecules 312 on the second substrate 200 side, and it becomes easier to obtain a uniform twisted orientation. Similarly, the pitch of the fourth comb-teeth electrode 222 is preferably 1 μm or more and 5 μm or less. By adopting such an aspect, it becomes possible to efficiently rotate the liquid crystal molecules 312 on the second substrate 200 side, and it becomes easier to obtain a uniform twisted orientation.

In plan view, the angle β between the stretching direction 121A and the stretching direction 221A (where β is a real number greater than 0° and less than 90°), and the twist angle B of the liquid crystal molecules 310 included in the liquid crystal layer 300 are: In the first state and the second state, it is preferable that the following (Formula BX1) is satisfied, it is more preferable that the following (Formula BX2) is satisfied, and it is still more preferable that the following (Formula BX3) is satisfied. By adopting such an aspect, polarization modulation and polarization non-modulation can be effectively switched over a wide band.
85°-B≦β≦95°-B (Formula BX1)
88°-B≦β≦92°-B (Formula BX2)
β=90°−B (Formula BX3)

The twist angle B is preferably 60° or more and 80° or less, more preferably 64° or more and 76° or less, and even more preferably 68° or more and 72° or less. By adopting such an aspect, polarization modulation and polarization non-modulation can be switched more effectively over a wide band.

The azimuth angle of the stretching direction 121A is 0°, the azimuth angle of the stretching direction 221A is 160° (that is, the angle β between the stretching direction 121A and the stretching direction 221A is 20° in plan view), and the liquid crystal molecules 310 When the twist angle B of is 70° and the liquid crystal layer 300 contains positive liquid crystal molecules 310, as shown in FIG. When the second comb-teeth electrode 220 is in a voltage applied state, the third comb-teeth electrode 221 is in a voltage applied state, and the fourth comb-teeth electrode 222 is in a no-voltage applied state, the first substrate 100 side A first state can be realized in which the azimuth angle of the alignment direction 311A of the liquid crystal molecules 311 is 0° and the azimuth angle of the alignment direction 312A of the liquid crystal molecules 312 on the second substrate 200 side is 70°. Further, the first comb-teeth electrode 120 is in a voltage applied state, the second comb-teeth electrode 220 is in a no-voltage applied state, the third comb-teeth electrode 221 is in a no-voltage applied state, and the fourth comb-teeth electrode 220 is in a no-voltage applied state. When the tooth electrode 222 is in a voltage applied state, the azimuth angle of the alignment direction 311B of the liquid crystal molecules 311 on the first substrate 100 side is 90°, and the azimuth angle of the alignment direction 312B of the liquid crystal molecules 312 on the second substrate 200 side is 90°. A second state in which is 160° can be realized.

When the liquid crystal layer 300 contains negative type liquid crystal molecules 310, when the first comb tooth electrode 121 is in a voltage applied state, the second comb tooth electrode 122 is in a voltage not applied state, the third comb tooth electrode 221 is in a voltage not applied state, and the fourth comb tooth electrode 222 is in a voltage applied state, a first state can be realized in which the azimuth angle of the alignment direction 311A of the liquid crystal molecules 311 on the first substrate 100 side is 0° and the azimuth angle of the alignment direction 312A of the liquid crystal molecules 312 on the second substrate 200 side is 70°. Furthermore, when the first comb tooth electrode 121 is in a no-voltage-applied state, the second comb tooth electrode 122 is in a voltage-applied state, the third comb tooth electrode 221 is in a voltage-applied state, and the fourth comb tooth electrode 222 is in a no-voltage-applied state, a second state can be realized in which the azimuth angle of the alignment direction 311B of the liquid crystal molecules 311 on the first substrate 100 side is 90°, and the azimuth angle of the alignment direction 312B of the liquid crystal molecules 312 on the second substrate 200 side is 160°.

In the present embodiment in which the liquid crystal layer 300 contains positive liquid crystal molecules 310, the alignment direction 311A of the liquid crystal molecules 311 on the first substrate 100 side in the first state is the same as that provided on the first comb-teeth electrode 121 in plan view. This corresponds to the extending direction 121A of the comb-teeth electrode. Therefore, when the azimuth angle of the alignment direction 311A of the liquid crystal molecules 311 on the first substrate 100 side in the first state is 0°, for example, the azimuth angle of the stretching direction 121A is 0°, and the azimuth angle of the stretching direction 122A and the stretching direction 222A is 0°. The azimuth angle of the stretching direction 221A is 160°, the azimuth angle of the slow axis 12A of the first 1/4 wavelength film 12 is 57.2°, and the azimuth angle of the second 1/4 wavelength film 12 is 90°. The azimuth angle of the slow axis 13A of the film 13 can be set to 12.2°.

Similar to Embodiments 1 and 2 above, the optical element 10 of this embodiment includes a first weakly anchored horizontal alignment film disposed between the first substrate 100 and the liquid crystal layer 300, and a liquid crystal layer. 300 and a second weakly anchoring horizontal alignment film disposed between the second substrate 200 and the second substrate 200. By adopting such an embodiment, the liquid crystal molecules near the interface can also be uniformly aligned while maintaining the horizontal alignment.

(Embodiment 4)
In this embodiment, features unique to this embodiment will be mainly explained, and explanations of contents that overlap with those of Embodiments 1 to 3 will be omitted. This embodiment is substantially the same as Embodiment 1, except that a bistable alignment film is used in place of the first weakly anchored horizontal alignment film 411.

FIG. 16 is a schematic perspective view of a liquid crystal cell included in the optical element according to Embodiment 4. As shown in FIG. 16, the liquid crystal cell 11 included in the optical element 10 of this embodiment further includes a bistable alignment layer having stable alignment directions in two directions, which is disposed between the first substrate 100 and the liquid crystal layer 300. It has a membrane 413. The electrode 11E has a first comb-teeth electrode 120 in which a comb-teeth-shaped pixel electrode and a common electrode are provided so that the comb-teeth fit into each other on the first substrate 100, and a first comb-teeth electrode 120 on the second substrate 200. In this case, the comb-shaped pixel electrode and the common electrode have a second comb-shaped electrode 220 provided so that the comb-shaped pixel electrode and the common electrode fit into each other. In plan view, the extending direction 120A of the first comb-teeth electrode 120 is provided diagonally with respect to the extending direction 220A of the second comb-teeth electrode 220.

By adopting such an aspect, when the first comb-shaped electrode 120 is in a non-voltage applied state and the second comb-shaped electrode 220 is in a voltage-applied state, the circularly polarized light incident on the liquid crystal cell 11 (for example, After passing through the liquid crystal cell 11, the right-handed circularly polarized light becomes first linearly polarized light. That is, the first state can be realized. Furthermore, the first linearly polarized light passes through the first 1/4 wavelength film 12 and the second 1/4 wavelength film 13, thereby becoming circularly polarized light whose polarization state is different from that of the circularly polarized light incident on the liquid crystal cell 11. (for example, left-handed circularly polarized light). In this way, in the first state, the circularly polarized light incident on the optical element 10 is converted into circularly polarized light with a different polarization state (for example, right-handed circularly polarized light is converted into left-handed circularly polarized light), and the output polarization modulation is broadband. It is realized by

Furthermore, when the first comb-teeth electrode 121 is in a voltage applied state and the second comb-teeth electrode 122 is in a non-voltage applied state, the circularly polarized light (for example, right-handed circularly polarized light) incident on the liquid crystal cell 11 is 11, it becomes second linearly polarized light having a polarization direction perpendicular to the polarization direction of the first linearly polarized light in plan view. That is, the second state can be realized. Further, the second linearly polarized light passes through the first 1/4 wavelength film 12 and the second 1/4 wavelength film 13, thereby becoming circularly polarized light having the same polarization state as the circularly polarized light that entered the liquid crystal cell 11. The polarized light (for example, right-handed circularly polarized light) is emitted as it is in a wide band. In this way, in the second state, polarization non-modulation is realized in a wide band, in which the circularly polarized light incident on the optical element 10 is output while remaining in the same polarization state (for example, right-handed circularly polarized light).

The bistable alignment film 413 is an alignment film having stable alignment directions in two directions (first direction 413A and second direction 413B). In plan view, the first direction 413A and the second direction 413B are orthogonal to each other, and the first direction 413A is parallel to the orientation direction 311A of the liquid crystal molecules 311 on the first substrate 100 side in the first state. It is preferable that Since the azimuth angle of the alignment direction 311A of the liquid crystal molecules 311 on the first substrate 100 side is 0° in the first state and 90° in the second state, the first direction 413A and the second direction The orientations of the directions 413B are orthogonal to each other, and the first direction 413A is parallel to the orientation direction 311A of the liquid crystal molecules 311 on the first substrate 100 side in the first state. The alignment direction of the liquid crystal molecules 311 on the first substrate 100 side can be energetically stabilized by the bistable alignment film 413. As a result, it is possible to realize an optical element 10 with better alignment stability than in the first embodiment in which the alignment direction of the liquid crystal molecules 310 is defined only by voltage.

The bistable alignment film 413 can be formed by light irradiation or by rubbing the uneven substrate.

When using light irradiation, for example, the bistable alignment film 413 can be formed using a material that is a mixture of two polymers having different photofunctional wavelengths. After applying a solution of a mixture of two polymers with different photofunctional wavelengths on a substrate, for example, irradiation with polarized ultraviolet rays of a certain wavelength, and then irradiation with polarized ultraviolet rays of a different wavelength and direction. A bistable alignment film 413 having stable alignment directions in two directions, the eye direction and the second direction, can be formed.

When using a textured substrate and a rubbing process, for example, a structure having grooves in a specific direction is formed using a polymer on the substrate, and the rubbing process is performed in a direction different from the direction of the grooves. The liquid crystal molecules have two forces: a force that tends to align them in the groove direction and a force that tends to align them in the rubbing direction, and it is possible to form a bistable alignment film 413 that has stable alignment directions in two directions.

The optical element 10 of this embodiment may include a second alignment film 420 between the second substrate 200 and the liquid crystal layer 300. The second alignment film 420 is, for example, a weak anchoring horizontal alignment film 423. The weak anchoring horizontal alignment film 423 is preferably a slippery film. By adopting such an aspect, polarization modulation and polarization non-modulation can be switched over a wider band.

The second alignment film 420 may be, for example, a vertical alignment film. As the vertical alignment film, a film similar to the vertical alignment film 422 can be used.

(Embodiment 5)
In this embodiment, features unique to this embodiment will be mainly explained, and explanations of contents that overlap with those of Embodiments 1 to 4 will be omitted. This embodiment is substantially the same as Embodiment 1 except that the configuration of the liquid crystal cell 11 is different.

FIG. 17 is a schematic cross-sectional view of a liquid crystal cell included in the optical element according to Embodiment 5. FIG. 18 is a schematic perspective view of a liquid crystal cell included in the optical element according to Embodiment 5. FIG. 19 is a diagram showing an example of the axial orientation of the optical element according to the fifth embodiment. Since the alignment of liquid crystal molecules near the interface of the substrate is vertical and the orientation cannot be defined, in FIG. 19, the alignment direction of the liquid crystal molecules is defined by the electrode direction.

As shown in FIGS. 17 to 19, the liquid crystal cell 11 included in the optical element 10 of this embodiment further includes a first vertical alignment film 414 disposed between the first substrate 100 and the liquid crystal layer 300. , a second vertical alignment film 424 disposed between the liquid crystal layer 300 and the second substrate 200. The electrode 11E includes, on the first substrate 100, a planar first electrode 131 and a second electrode 132 that overlaps the first electrode 131 via the first insulating layer 141 and is provided with a slit portion 132S. In the second substrate 200, a planar third electrode 231, and a fourth electrode 232 that overlaps the third electrode 231 via the second insulating layer 241 and is provided with a slit portion 232S. has. In plan view, the extending direction 132A of the slit portion 132S provided in the second electrode 132 is arranged diagonally with respect to the extending direction 232A of the slit portion 232S provided in the fourth electrode 232.

By adopting such an aspect, when a voltage is applied between the first electrode 131 and the second electrode 132 and a voltage is not applied between the third electrode 231 and the fourth electrode 232, the light incident on the liquid crystal cell 11 The circularly polarized light (for example, right-handed circularly polarized light) becomes first linearly polarized light after passing through the liquid crystal cell 11. That is, the first state can be realized. Furthermore, the first linearly polarized light passes through the first 1/4 wavelength film 12 and the second 1/4 wavelength film 13, thereby becoming circularly polarized light whose polarization state is different from that of the circularly polarized light incident on the liquid crystal cell 11. (for example, left-handed circularly polarized light). In this way, in the first state, the circularly polarized light incident on the optical element 10 is converted into circularly polarized light with a different polarization state (for example, right-handed circularly polarized light is converted into left-handed circularly polarized light), and the output polarization modulation is broadband. It is realized by

Further, when the voltage is not applied between the first electrode 131 and the second electrode 132 and the voltage is applied between the third electrode 231 and the fourth electrode 232, the circularly polarized light (for example, the right When the circularly polarized light passes through the liquid crystal cell 11, it becomes a second linearly polarized light having a polarization direction perpendicular to the polarization direction of the first linearly polarized light in plan view. That is, the second state can be realized. Furthermore, the second linearly polarized light passes through the first 1/4 wavelength film 12 and the second 1/4 wavelength film 13, thereby becoming circularly polarized light having the same polarization state as the circularly polarized light that entered the liquid crystal cell 11. The polarized light (for example, right-handed circularly polarized light) is emitted as it is in a wide band. In this way, in the second state, polarization non-modulation is realized in a wide band in which the circularly polarized light incident on the optical element 10 is output while remaining in the same polarization state (for example, right-handed circularly polarized light).

Note that one of the first electrode 131 and the second electrode 132 is a pixel electrode, and the other is a common electrode. One of the third electrode 231 and the fourth electrode 232 is a pixel electrode, and the other is a common electrode. In FIG. 18, both the first substrate 100 and the second substrate 200 include electrodes provided with a planar electrode and a slit portion in order toward the liquid crystal layer 300 side. The arrangement of the electrodes is not limited to this, and an electrode provided with a slit portion and a planar electrode may be provided in order toward the liquid crystal layer 300 side.

In plan view, the angle γ (γ is a real number greater than 0° and less than 90°) between the stretching direction 132A and the stretching direction 232A and the twist angle C of the liquid crystal molecules 310 contained in the liquid crystal layer 300 preferably satisfy the following (Formula CX1), more preferably satisfy the following (Formula CX2), and even more preferably satisfy the following (Formula CX3) in the first state and the second state. By adopting such an embodiment, it is possible to effectively switch between polarization modulation and polarization non-modulation in a wide band.
85°-C≦γ≦95°-C (Formula CX1)
88°-C≦γ≦92°-C (Formula CX2)
γ = 90°-C (Equation CX3)

The twist angle C is preferably 60° or more and 80° or less, more preferably 64° or more and 76° or less, and even more preferably 68° or more and 72° or less. By adopting such an aspect, polarization modulation and polarization non-modulation can be switched more effectively over a wide band.

The azimuth angle of the stretching direction 132A is 0°, the azimuth angle of the stretching direction 232A is 160° (that is, the angle γ between the stretching direction 132A and the stretching direction 232A is 20° in plan view), and the liquid crystal molecules 310 When the twist angle C is 70° and the liquid crystal layer 300 contains negative liquid crystal molecules 310, a voltage is applied between the first electrode 131 and the second electrode 132, and the third electrode 231 and the second electrode When no voltage is applied between the four electrodes 232, the azimuth angle of the alignment direction 311A of the liquid crystal molecules 311 on the first substrate 100 side is 0°, and the azimuth angle of the alignment direction 312A of the liquid crystal molecules 312 on the second substrate 200 side is 0°. A first state in which the azimuth angle is 70° can be achieved. Furthermore, when no voltage is applied between the first electrode 131 and the second electrode 132 and a voltage is applied between the third electrode 231 and the fourth electrode 232, the alignment direction of the liquid crystal molecules 311 on the first substrate 100 side A second state can be realized in which the azimuth angle of the liquid crystal molecules 311B is 90° and the azimuth angle of the orientation direction 312B of the liquid crystal molecules 312 on the second substrate 200 side is 160°.

Note that when the liquid crystal layer 300 contains positive liquid crystal molecules 310, no voltage is applied between the first electrode 131 and the second electrode 132, and a voltage is applied between the third electrode 231 and the fourth electrode 232. In this case, a first state in which the azimuth angle of the alignment direction 311A of the liquid crystal molecules 311 on the first substrate 100 side is 0° and the azimuth angle of the alignment direction 312A of the liquid crystal molecules 312 on the second substrate 200 side is 70°. can be realized. Further, when a voltage is applied between the first electrode 131 and the second electrode 132 and a voltage is not applied between the third electrode 231 and the fourth electrode 232, the alignment direction of the liquid crystal molecules 311 on the first substrate 100 side A second state can be realized in which the azimuth angle of the liquid crystal molecules 311B is 90° and the azimuth angle of the alignment direction 312B of the liquid crystal molecules 312 on the second substrate 200 side is 160°.

The first substrate 100 has, in order, a first support substrate 110, a planar first electrode 131, a first insulating layer 141, and a second electrode 132. The second substrate 200 has, in order, a second support substrate 210, a planar third electrode 231, a second insulating layer 241, and a fourth electrode 232 provided with a slit portion 232S.

The pitch of the second electrode 132 provided with the slit portions 132S is preferably 1 μm or more and 5 μm or less. By adopting such an aspect, it becomes possible to efficiently rotate the liquid crystal molecules 311 on the first substrate 100 side, and it becomes easier to obtain a uniform twisted orientation. Further, the pitch of the fourth electrode 232 provided with the slit portion 232S is preferably 1 μm or more and 5 μm or less. By adopting such an aspect, it becomes possible to efficiently rotate the liquid crystal molecules 312 on the second substrate 200 side, and it becomes easier to obtain a uniform twisted orientation. Here, the electrode provided with the slit portion has a structure in which linear electrode portions and slit portions are arranged alternately, and the pitch of the electrode provided with the slit portion is determined by the pitch of the electrode provided with the slit portion. This means the total width of the slit portion and the slit portion.

The liquid crystal molecules 310 are preferably negative type liquid crystal molecules. With this embodiment, by applying a large vertical voltage between the first substrate 100 and the second substrate 200, the negative liquid crystal molecules 310 can be tilted and horizontally aligned. In the first state and the second state, the voltage difference between the first electrode 131 and the third electrode 231 is preferably 1V or more, more preferably 3V or more, and still more preferably 5V or more. preferable. By adopting such an aspect, the liquid crystal molecules 310 can be horizontally aligned more effectively. Although the upper limit of the voltage difference between the first electrode 131 and the third electrode 231 is not particularly limited, the voltage difference between the first electrode 131 and the third electrode 231 is, for example, 20V or less. The voltage difference between the first electrode 131 and the third electrode 231 is preferably 1V or more and 20V or less, more preferably 3V or more and 20V or less, and even more preferably 5V or more and 20V or less. preferable.

Further, a weak voltage is applied between the pixel electrode and the common electrode between the first electrode 131 and the second electrode 132 and between the third electrode 231 and the fourth electrode 232, respectively, to change the in-plane alignment direction of the liquid crystal molecules 310. can be controlled. When the liquid crystal molecules 310 are negative type liquid crystal molecules, the liquid crystal molecules 310 are oriented in the direction in which the slit portions 132S and 232S extend (the direction perpendicular to the electric field) in the plane. At this time, if a strong transverse electric field is applied, the alignment twist of the liquid crystal due to chiral force will be disturbed, so it is preferable that the transverse electric field is weak.

For example, the voltage difference between the first electrode 131 and the second electrode 132 in the first state is preferably 3V or less, more preferably 1V or less, and even more preferably 0.5V or less. . Further, the potential difference between the third electrode 231 and the fourth electrode 232 in the second state is preferably 3V or less, more preferably 1V or less, and even more preferably 0.5V or less. Although the lower limit of the voltage difference between the first electrode 131 and the second electrode 132 in the first state is not particularly limited, the voltage difference between the first electrode 131 and the second electrode 132 in the first state is, for example, , 0.01V or more. Further, the lower limit value of the voltage difference between the third electrode 231 and the fourth electrode 232 in the second state is not particularly limited, but the voltage difference between the third electrode 231 and the fourth electrode 232 in the second state is , for example, 0.01V or more.

The voltage difference between the first electrode 131 and the second electrode 132 in the first state is preferably 0.01 V or more and 3 V or less, and more preferably 0.05 V or more and 1 V or less. The potential difference between the third electrode 231 and the fourth electrode 232 in the second state is preferably 0.01 V or more and 3 V or less, and more preferably 0.05 V or more and 1 V or less.

The first vertical alignment film 414 and the second vertical alignment film 424 can be the same as the vertical alignment film 422. In the optical element 10 of this embodiment, since vertical alignment films are arranged on both substrate sides, it is possible to realize an optical element 10 with higher productivity than when horizontal alignment films are arranged.

The first vertical alignment film 414 and the second vertical alignment film 424 may impart a small tilt angle to the liquid crystal molecules. Specifically, the first vertical alignment film 414 and the second vertical alignment film 424 may impart a pretilt angle of 85° or more and 90° or less to the liquid crystal molecules 310.

FIG. 20 is a schematic diagram illustrating the orientation of liquid crystal molecules in the first state and the second state of the optical element according to the fifth embodiment. As shown in FIG. 20, the liquid crystal molecules 310 are vertically aligned very close to the first substrate 100 and the second substrate 200, but within the liquid crystal layer 300, the horizontal alignment is twisted at approximately 70°. It has been realized.

In this embodiment, in which the liquid crystal layer 300 contains negative liquid crystal molecules 310, in a plan view, the alignment direction 311A of the liquid crystal molecules 311 on the first substrate 100 side in the first state coincides with the stretching direction 132A of the slit portion 132S provided in the second electrode 132. Therefore, when the azimuth angle of the alignment direction 311A of the liquid crystal molecules 311 on the first substrate 100 side in the first state is set to 0°, for example, the azimuth angle of the stretching direction 132A can be set to 0°, the azimuth angle of the stretching direction 232A can be set to 160°, the azimuth angle of the slow axis 12A of the first ¼ wavelength film 12 can be set to 57.2°, and the azimuth angle of the slow axis 13A of the second ¼ wavelength film 13 can be set to 12.2°.

Regarding the optical element 10 of this embodiment, as in other embodiments, the modulation characteristics and non-modulation characteristics can be tuned as appropriate by designing the retardation Δnd and twist angle of the liquid crystal layer 300.

(Embodiment 6)
In this embodiment, features unique to this embodiment will be mainly explained, and explanations of contents that overlap with those of Embodiments 1 to 5 will be omitted. This embodiment is substantially the same as Embodiment 1, except that it does not include the second quarter-wavelength film 13.

FIG. 21 is a schematic cross-sectional view of an optical element according to Embodiment 6. FIG. 22 is a schematic perspective view of a liquid crystal cell included in the optical element according to Embodiment 6. FIG. 23 is a diagram showing an example of the axial orientation of the optical element according to the sixth embodiment.

As shown in FIGS. 21 to 23, the optical element 10 of this embodiment includes a liquid crystal cell 11 similar to that of Embodiment 1, and a reverse wavelength dispersion 1/4 wavelength film as a first 1/4 wavelength film 12. It is equipped with With such an embodiment, while suppressing the thickness of the optical element 10, a state in which the circularly polarized light incident on the optical element 10 is emitted without being modulated, and a state in which the circularly polarized light incident on the optical element 10 is modulated and emitted. It becomes possible to switch over a wide band. That is, it is possible to realize an optical element 10 that can switch between polarization modulation and non-polarization modulation over a wide band and can be made thinner.

When the first 1/4 wavelength film 12 is disposed on the emission side of the liquid crystal cell 11 as in this embodiment, the azimuth angle of the slow axis 12A of the first 1/4 wavelength film 12 is 3°. As mentioned above, it is preferable that the angle is 22° or less. Further, when the first quarter wavelength film 12 is arranged on the incident side of the liquid crystal cell 11, the azimuth angle of the slow axis 12A of the first quarter wavelength film 12 is 48° or more and 67° or less. It is preferable that By adopting such an aspect, polarization modulation and polarization non-modulation can be switched over a wider band.

Up to this point, the case where the liquid crystal molecules are positive-type liquid crystal molecules or negative-type liquid crystal molecules has been described, but a dual-frequency drive liquid crystal may be used as the liquid crystal molecules. A dual-frequency driven liquid crystal is a liquid crystal molecule that behaves as a positive type liquid crystal molecule with a positive Δε at low frequencies and a negative type liquid crystal molecule with a negative Δε at high frequencies. When using a dual-frequency liquid crystal, there is no need to provide comb-shaped electrodes with different angles on the upper and lower substrates (the first substrate 100 and the second substrate 200), and it is possible to drive one comb-shaped electrode at a low frequency. The liquid crystal molecules are oriented in a direction perpendicular to the direction in which the electrodes are stretched, and when high frequency driving is performed, the liquid crystal molecules are oriented in the direction in which the electrodes are stretched, so that the electrode configuration can be simplified.

(Embodiment 7)
In this embodiment, features unique to this embodiment will be mainly explained, and explanations of contents that overlap with those of Embodiments 1 to 6 will be omitted. In this embodiment, a variable focus element including the optical element (sHWP) of Embodiments 1 to 6 above will be described. FIG. 24 is a schematic cross-sectional view of a variable focus element according to Embodiment 7. A variable focus element 30 of this embodiment shown in FIG. 24 includes an optical element 10 and a Pancharatnam Berry (PB) lens 20.

As described above, the optical element 10 of Embodiments 1 to 6 can modulate circularly polarized light. Furthermore, since the PB lens 20 has different focal lengths for right-handed circularly polarized light and left-handed circularly polarized light, the variable focus element 30 can be realized by combining the optical element 10 and the PB lens 20.

The PB lens 20 has a function of condensing and diverging circularly polarized light. The PB lens 20 can be produced, for example, by the method described in International Publication No. 2019/189818.

Figure 25 is an example of a cross-sectional schematic diagram of a PB lens provided in a variable focus element according to embodiment 7. As shown in Figure 25, the PB lens 20 has an optically anisotropic layer 320A. As an example, the PB lens 20 refracts and transmits incident light in a predetermined direction, targeting circularly polarized light. Note that in Figure 25, the incident light is left-handed circularly polarized light.

In the part shown in FIG. 25, the optically anisotropic layer 320A has three regions R0, R1, and R2 from the left side in FIG. 25, and the length Λ of one period is different in each region. Specifically, the length Λ of one period becomes shorter in the order of regions R0, R1, and R2. Further, the regions R1 and R2 have a structure in which the optical axis is twisted and rotated in the thickness direction of the optically anisotropic layer (hereinafter also referred to as a twisted structure). The torsion angle in the thickness direction of region R1 is smaller than the torsion angle in the thickness direction of region R2. Note that the region R0 is a region that does not have a torsion structure (that is, the torsion angle is 0°). Note that the twist angle is the twist angle in the entire thickness direction.

In the optical element 10, when the left-handed circularly polarized light LC1 is incident on the in-plane region R1 of the optically anisotropic layer 320A, the direction of the optical axis of the liquid crystal molecules 320 is continuous in the direction of the arrow X with respect to the incident direction. While rotating, the light is refracted in one direction at a predetermined angle and transmitted. Similarly, when the left-handed circularly polarized light LC2 is incident on the in-plane region R2 of the optically anisotropic layer 320A, it is refracted at a predetermined angle in the direction of the arrow X with respect to the incident direction and is transmitted. Similarly, when the left-handed circularly polarized light LC0 is incident on the in-plane region R0 of the optically anisotropic layer 320A, it is refracted at a predetermined angle in the direction of the arrow X with respect to the incident direction and is transmitted.

Here, the angle of refraction by the optically anisotropic layer 320A is as shown in FIG. 25 because one period Λ R2 of the liquid crystal alignment pattern in region R2 is shorter than one period Λ _R1 of the liquid crystal alignment pattern in region _R1 . Regarding the angle of refraction with respect to the incident light, the angle θ _R2 of the transmitted light in the region R2 is larger than the angle θ _R1 of the transmitted light in the region R1. Furthermore, since one period Λ _R0 of the liquid crystal alignment pattern in region R0 is longer than one period Λ _R1 of the liquid crystal alignment pattern in region R1, as shown in FIG. The light angle θ _R0 is smaller than the transmitted light angle θ _R1 of the region R1.

Here, in light diffraction by an optically anisotropic layer having a liquid crystal alignment pattern in which the direction of the optical axis of the liquid crystal molecules changes while continuously rotating within the plane, the diffraction efficiency decreases as the diffraction angle increases. In other words, there is a problem that the intensity of the diffracted light becomes weak. Therefore, if the optically anisotropic layer is configured to have regions with different lengths of one period in which the direction of the optical axis of the liquid crystal molecules rotates 180 degrees in the plane, the diffraction angle will differ depending on the incident position of the light. Therefore, the amount of diffracted light varies depending on the in-plane incident position. That is, depending on the in-plane incident position, there are regions where the transmitted and diffracted light becomes dark.

On the other hand, the PB lens 20 of this embodiment has a region in which the optically anisotropic layer twists and rotates in the thickness direction, and has regions in which the magnitude of the twist angle in the thickness direction is different. In the example shown in FIG. 25, the torsion angle φ _R2 in the thickness direction of the region R2 of the optically anisotropic layer 320A is larger than the torsion angle φ _R1 in the thickness direction of the region R1. Further, the region R0 does not have a twisted structure in the thickness direction. Thereby, it is possible to suppress a decrease in the diffraction efficiency of refracted light.

In the example shown in FIG. 25, by providing a twisted structure to regions R1 and R2 with larger diffraction angles than region R0, it is possible to suppress a decrease in the amount of light refracted in regions R1 and R2. Further, by making the twist angle of the twist structure of the region R2, which has a larger diffraction angle than the region R1, larger than that of the region R1, it is possible to suppress a decrease in the amount of light refracted in the region R2. This allows the amount of transmitted light to be made uniform depending on the in-plane incident position.

Thus, in the PB lens 20 of this embodiment, in areas in the plane where refraction by the optically anisotropic layer is large, incident light passes through a layer with a large twist angle in the thickness direction and is refracted. In contrast, in areas in the plane where refraction by the optically anisotropic layer is small, incident light passes through a layer with a small twist angle in the thickness direction and is refracted. That is, in the PB lens 20, the twist angle in the thickness direction in the plane can be set according to the magnitude of refraction by the optically anisotropic layer, thereby making it possible to brighten the transmitted light relative to the incident light. Therefore, the PB lens 20 can reduce the refraction angle dependency of the amount of transmitted light in the plane.

The angle of refraction of light within the plane of the optically anisotropic layer 320A increases as one period Λ of the liquid crystal alignment pattern becomes shorter. Furthermore, the torsion angle in the in-plane thickness direction of the optically anisotropic layer 320A is one period in a region where the direction of the optical axis is rotated by 180 degrees along the arrow X direction in one period Λ. It has a larger area than the larger area of Λ. In the PB lens 20, as an example, as shown in FIG. 25, one period Λ _R2 of the liquid crystal alignment pattern in the region R2 of the optically anisotropic layer 320A is shorter than one period Λ _R1 of the liquid crystal alignment pattern in the region R1. , the twist angle φ _R2 is large in the thickness direction. That is, the region R2 of the optically anisotropic layer 320A on the light incident side refracts light to a greater extent.

Therefore, by setting the in-plane thickness direction twist angle φ for one period Λ of the target liquid crystal orientation pattern, it is possible to advantageously brighten the transmitted light that is refracted at different angles in different regions in the plane.

In the PB lens 20, as described above, the shorter the period Λ of the liquid crystal alignment pattern, the larger the angle of refraction. This makes it possible to brighten the transmitted light. Therefore, in the PB lens 20, it is preferable to have a region in which the length of one period of the liquid crystal alignment pattern differs from the permutation of the length of one period and the permutation of the twist angle in the thickness direction.

From the above, the PB lens 20 includes the optically anisotropic layer 320A formed using a liquid crystal composition containing the liquid crystal molecules 320, and the optically anisotropic layer 320A has an optical axis derived from the liquid crystal molecules whose direction is in the plane. has a liquid crystal alignment pattern that continuously rotates and changes along at least one direction within the range, and has a region in which the optical axis is twisted and rotated in the thickness direction of the optically anisotropic layer 320A. It is preferable to have regions having different twist angles in the thickness direction.

The PB lens 20 may have regions in which the length of one period in the liquid crystal alignment pattern is different, where one period is the length of the in-plane rotation of the optical axis derived from the liquid crystal molecules 320 by 180 degrees. preferable.

In the optically anisotropic layer 320A, a plurality of regions having different lengths of one period in the liquid crystal alignment pattern are arranged in the order of the length of one period, and the torsion angle in the thickness direction is large. A plurality of regions having different values are arranged in the order of the magnitude of the torsion angle in the thickness direction, and the direction of the permutation of the length of one period and the direction of the permutation of the magnitude of the torsion angle in the thickness direction. It is preferable that the two regions have different regions.

It is preferable that the optically anisotropic layer 320A has a region in which the twist angle in the thickness direction is 10° to 360°.

The optically anisotropic layer 320A is configured such that the one cycle of the liquid crystal alignment pattern gradually changes in the one direction in which the direction of the optical axis derived from the liquid crystal molecules 320 in the liquid crystal alignment pattern changes while continuously rotating. , is preferably short.

The liquid crystal orientation pattern of the optically anisotropic layer 320A is preferably a concentric pattern extending from the inside to the outside in the direction in which the orientation of the optical axis derived from the liquid crystal molecules 320 changes while continuously rotating.

The PB lens 20 shown in FIG. 25 is a PB lens whose torsion angle changes within the plane, and is an element with high diffraction efficiency even when the diffraction angle is large. It is also possible to use a PB lens that does not. Specifically, the PB lens 20 may be a PB lens with no twist in the thickness direction or with a constant twist angle in the plane, for example, the polarization diffraction method described in Japanese Patent Publication No. 2008-532085. A grid can be used.

The PB lens 20 is a PB lens equipped with a plurality of optically anisotropic layers 320A, and has the optically anisotropic layers 320A having different twist angle directions in the thickness direction of the optically anisotropic layer 320A. It is preferable.

The PB lens 20 is a PB lens having multiple optically anisotropic layers 320A, and it is preferable that the optically anisotropic layers 320A have different twist angles in the thickness direction of the optically anisotropic layers 320A.

The PB lens 20 is a PB lens having multiple optically anisotropic layers 320A, and it is preferable that the optically anisotropic layers 320A have a liquid crystal orientation pattern in which the directions of the optical axes derived from the liquid crystal molecules 320 continuously rotate along at least one direction in the plane are the same.

The length of one period in the liquid crystal alignment pattern is preferably 50 μm or less.

The variable focus element 30 may be a binary variable focus element 30A that includes one set of a laminate including the optical element 10 and the PB lens 20, or may include two sets of laminates including the optical element 10 and the PB lens 20. A multi-stage variable focus element 30B including the above may be used. In this way, by combining a plurality of sets of the optical element 10 and the PB lens 20, it is possible to realize a variable focus element 30B with multi-stage tunability.

The variable focus element 30 can be produced, for example, by attaching the PB lens 20 produced by the method described in International Publication No. 2019/189818 to the optical element 10.

(Variation 1 of the seventh embodiment)
In this modification, a variable focus element 30 in which the PB lens 20 in the seventh embodiment is disposed in an optical element 10 and in-cell will be described. Fig. 26 is a cross-sectional schematic diagram of a variable focus element according to a first modification of the seventh embodiment. Fig. 27 is an enlarged cross-sectional schematic diagram of a variable focus element according to the first modification of the seventh embodiment.

As shown in FIG. 26, the variable focus element 30 of this modification is a multi-stage variable focus element 30B including two or more sets of laminates each consisting of an optical element 10 and a PB lens 20.

The PB lens 20 included in the variable focus element 30 of this modification is arranged within the optical element 10, as shown in FIG. By making the PB lens 20 in-cell in this way, there is no need to attach the PB lens 20 externally, so manufacturing costs can be significantly reduced. Moreover, it becomes possible to suppress the thickness of the variable focus element 30. Note that in FIG. 26, the optical element 10 and the PB lens 20 are shown separately for convenience.

More specifically, the variable focus element 30 of this modification includes, in order from the incident side to the exit side, a second 1/4 wavelength film 13, a first 1/4 wavelength film 12, and a first 1/4 wavelength film 13. It includes a substrate 100, a liquid crystal layer 300, a PB lens 20, and a second substrate 200. The variable focus element 30 may include a first alignment film 410 between the first substrate 100 and the liquid crystal layer 300. Further, the variable focus element 30 may include a second alignment film 420 between the second substrate 200 and the liquid crystal layer 300.

Here, when the first 1/4 wavelength film 12 and the second 1/4 wavelength film 13 are arranged on the emission side of the liquid crystal cell 11 as in the first to seventh embodiments, in the first state, The circularly polarized light (for example, right-handed circularly polarized light) that has entered the optical element 10 first enters the liquid crystal cell 11 and is converted into first linearly polarized light, and the first linearly polarized light has a first quarter wavelength. The light enters the film 12 and the second quarter-wavelength film 13 and is converted into circularly polarized light (for example, left-handed circularly polarized light). In the second state, the circularly polarized light (for example, right-handed circularly polarized light) that has entered the optical element 10 first enters the liquid crystal cell 11 and is converted into second linearly polarized light, and the second linearly polarized light is The light enters the first quarter-wavelength film 12 and the second quarter-wavelength film 13 and is converted into circularly polarized light (for example, right-handed circularly polarized light).

On the other hand, when the first 1/4 wavelength film 12 and the second 1/4 wavelength film 13 are arranged on the incident side of the liquid crystal cell 11 as in this modification, in the first state, the optical element 10 The incident circularly polarized light (for example, right-handed circularly polarized light) first enters the first 1/4 wavelength film 12 and the second 1/4 wavelength film 13 and is converted into linearly polarized light. The light enters the cell 11 and is converted into first circularly polarized light (for example, left-handed circularly polarized light). Furthermore, in the second state, the circularly polarized light (for example, right-handed circularly polarized light) that has entered the optical element 10 first enters the first quarter-wavelength film 12 and the second quarter-wavelength film 13, and then enters the first quarter-wavelength film 12 and the second quarter-wavelength film 13 to form a straight line. The linearly polarized light enters the liquid crystal cell 11 and is converted into second circularly polarized light (for example, right-handed circularly polarized light).

When the azimuth angle of the alignment direction 311A of the liquid crystal molecules 311 on the first substrate 100 side in the first state is 0°, it is preferable that the azimuth angle of the slow axis of the first quarter-wave film 12 or the second quarter-wave film 13 that is closer to the light emission side (in this modified example, the slow axis 12A of the first quarter-wave film 12) is 3° or more and 22° or less. By adopting such an embodiment, it is possible to switch between polarization modulation and polarization non-modulation over a wider band.

When the azimuth angle of the alignment direction 311A of the liquid crystal molecules 311 on the first substrate 100 side in the first state is 0°, the light beam of the first 1/4 wavelength film 12 and the second 1/4 wavelength film 13 is The azimuth angle of the slow axis of the 1/4 wavelength film on the side far from the emission side (in this modification, the slow axis 13A of the second 1/4 wavelength film 13) is 48° or more and 66° or less. is preferred. By adopting such an aspect, polarization modulation and polarization non-modulation can be switched over a wider band.

In other words, the in-cell PB lens 20 (PB lens layer) is an in-cell retardation layer patterned so that the slow axis direction rotates within the plane.

The PB lens can be made into an in-cell, for example, as follows. A photosensitive material for forming an in-cell PB lens containing a polymer represented by the following general formula (PB-1) is coated on the second substrate 200, and after forming a film for forming a PB lens, the PB lens is formed. The PB lens 20 can be made into an in-cell by performing orientation treatment on the film.

（上記式中、Ｖはスペーサ基を表し、Ｗは光官能基を有する二価の有機基を表し、Ｒ^５は一価の基を表し、ｐは１以上の整数を表す。）

(In the above formula, V represents a spacer group, W represents a divalent organic group having a photofunctional group, ^R5 represents a monovalent group, and p represents an integer of 1 or more.)

V in the above general formula (PB-1) represents a spacer group. V preferably has an alkylene group having 2 or more carbon atoms represented by -(CH ₂ ) _n - (where n is an integer of 2 or more). By adopting such an aspect, a good phase difference can be produced. The alkylene group is preferably linear.

W in the above general formula (PB-1) represents a divalent organic group having a photofunctional group. Examples of the divalent organic group having a photofunctional group include divalent organic groups containing a photofunctional group (photoreactive site) that causes reactions such as photodimerization, photoisomerization, photofries rearrangement, and photodecomposition. . Examples of photofunctional groups capable of photodimerization and photoisomerization include cinnamate groups, chalcone groups, coumarin groups, and stilbene groups. Examples of photofunctional groups capable of photoisomerization include azobenzene groups and the like. Examples of the photofunctional group capable of photo-Fries rearrangement include a phenol ester group. Examples of the photofunctional group that can be photodecomposed include a cyclobutane ring and the like.

R ⁵ in the above general formula (PB-1) represents a monovalent group. R ⁵ is preferably a hydrogen atom or a monovalent hydrocarbon group, and more preferably a hydrogen atom, a methyl group, or an ethyl group.

The orientation treatment of the PB lens formation film is performed by a plurality of orientation treatments, and the directions of the polarized light irradiated in the plurality of orientation treatments are different from each other. The orientation treatment of the PB lens formation film includes, for example, a first orientation treatment in which the PB lens formation film is oriented with polarized light having an azimuth angle of 0°, a second orientation treatment in which the PB lens formation film is oriented with polarized light having an azimuth angle of 45°, a third orientation treatment in which the PB lens formation film is oriented with polarized light having an azimuth angle of 90°, and a fourth orientation treatment in which the PB lens formation film is oriented with polarized light having an azimuth angle of 135°.

FIG. 28 is a schematic plan view showing an orientation pattern of a PB lens included in a variable focus element according to Modification 1 of Embodiment 7. As shown in FIG. 28, in the orientation pattern of the PB lens 20, for example, the orientation direction rotates continuously from the center toward the outer periphery. Furthermore, in plan view, the alignment direction of the liquid crystal molecules 310 at the radius R is all the same. In other words, it has a predetermined angular distribution depending on the distance from the center. The period P ₁ and the diffraction angle θ of the alignment pattern are expressed as P ₁ =2×λ/sin θ, and the shorter the period of the alignment pattern, the more light can be diffracted. Therefore, if you want to obtain a focusing lens effect, you can achieve this by widening the pitch toward the center of the optical element (smaller the diffraction angle) and decreasing the pitch toward the outer periphery (larger the diffraction angle).

PB lenses 20 having different diopters D, which will be described later, can be manufactured by changing the design of this alignment pattern period. Further, the orientation pattern can also be set based on International Publication No. 2020/186123, PCT International Publication No. 2008-532085, etc.

In the present embodiment, a case has been described in which the alignment process is performed through four exposures, but the variable focus element 30 with higher diffraction efficiency can be obtained as the number of exposure divisions increases. Manufacturing using multi-photo alignment processing using a photo-alignment device is compatible with existing liquid crystal factories and can be manufactured with high productivity. In this embodiment, the production of the PB lens 20 by multi-light alignment processing has been described, but the alignment pattern may be produced by existing methods such as optical interference method or direct laser writing.

The phase difference of the in-cell PB lens 20 (PB lens layer) is preferably 100 nm or more and 500 nm or less, more preferably 200 nm or more and 350 nm or less, and particularly preferably λ/2 (i.e., 275 nm). The diffraction efficiency is expressed by the following formula (1), and is maximum when Δnd = λ/2.

The variable focus element 30 of this modification, that is, the multi-stage variable focus element 30 in which a plurality of laminates of the optical element 10 and the PB lens 20 in-celled in the optical element 10 are combined, is configured as follows, for example. have characteristics.

FIG. 29 is a schematic cross-sectional view illustrating a detailed configuration of a variable focus element according to Modification 1 of Embodiment 7. As shown in FIG. 29, the variable focus element 30 includes, in order from the incident side to the output side, the optical element 10, the first PB lens 20A1, the optical element 10, the first PB lens 20A1, and the optical element 10, second PB lens 20A2, optical element 10, second PB lens 20A2, optical element 10, third PB lens 20A3, optical element 10, third PB lens 20A3 , is equipped with.

The first PB lens 20A1 has a diopter D = ±0.25, the second PB lens 20A2 has a diopter D = ±0.5, and the third PB lens 20A3 has a diopter D = ±1 lens characteristic. They have a + (converging) characteristic when right-handed circularly polarized light is incident, and a - (diverging) characteristic when left-handed circularly polarized light is incident.

The following Table 1 explains the state of the optical element 10 and the PB lenses 20A1, 20A2, and 20A3 in each mode of the variable focal element 30 according to the first modification of the seventh embodiment.

The F0 mode will be explained using Table 1 above. In this mode, all optical elements 10 are in the second state (unmodulated). When the right-handed circularly polarized light is incident, it is not modulated by the first optical element 10 and enters the first first PB lens 20A1 as it is. Here, the light is focused at 0.25D. At this time, the emitted light becomes left-handed circularly polarized light. Here, it is a characteristic of the PB lens 20 that the direction of circularly polarized light changes even after passing through the PB lens 20. Since the optical element 10 is non-modulated, the light passes through the second optical element 10 as left circularly polarized light. In the first PB lens 20A1 of the two eyes, a divergence of -0.25D occurs. As a result, the incident light passes through the first four lenses from the incident side (optical element 10, first PB lens 20A1, optical element 10 and first PB lens 20A1) as is. Thereafter, the light also passes through the second PB lens 20A2 and the PB lens 20A3 in the same manner, and is emitted as it is as the incident light at 0D.

The F1 mode will be explained using Table 1 above. In this mode, only the fourth optical element 10 from the incident side is in the first state. In this state, after passing through the first second PB lens 20A2, the light is left circularly polarized and 0.5D is imparted, similar to the F0 mode. Subsequently, the optical element in the first state converts the light into right-handed circularly polarized light. Subsequently, the second PB lens 20A2 imparts +0.5D to the light, and outputs it as left-handed circularly polarized light with a total of 1D. Thereafter, the light is emitted as 1D left-handed circularly polarized light. Since the light becomes left-handed circularly polarized light after passing through the second PB lens 20A2, the sign at the third PB lens 20A3 is opposite to that at F0.

The F-2.5 mode will be explained using Table 1 and FIG. 30 above. FIG. 30 is a diagram explaining the polarization state in the F-2.5 mode of the variable focal point element according to the first modification of the seventh embodiment. As shown in Table 1 and FIG. 30, in the F-2.5 mode, the first four lenses from the entrance side (optical element 10, first PB lens 20A1, optical element 10 and first PB lens 20A1) give -0.5D to the right circularly polarized light, and the last four lenses on the exit side (optical element 10, third PB lens 20A3, optical element 10 and third PB lens 20A3) give -2D to the light, and it is output as right circularly polarized light with a total of -2.5D.

In addition, by using the same principle, multiple focal lengths can be achieved depending on which optical element 10 is set to the first state of the modulation state. In this modified example, only three conditions are shown.

In the seventh embodiment and the first modification of the seventh embodiment, a mode including a film-like (in-cell polymer-like) PB lens has been described, but the PB lens itself may be formed of a liquid crystal layer. In this modification, a PB lens formed of a liquid crystal layer will be described.

As in the seventh embodiment and the first modification of the seventh embodiment, a polymer PB lens is called a passive PB lens because it cannot be varied by voltage. On the other hand, a PB lens formed of a fluid liquid crystal layer is called an active PB lens because it can be driven by voltage.

An active PB lens can be manufactured by the following procedure. First, a PB lens pattern alignment process is performed on the alignment film of one of the pair of substrates. The alignment film on the other substrate is a weak anchoring alignment film (slippery interface). Note that transparent electrodes are provided on both substrates. When this pair of substrates are bonded together with the liquid crystal layer sandwiched between them, the liquid crystal molecules are aligned along the pattern subjected to the alignment treatment, and the liquid crystal layer also takes on the alignment of the PB lens pattern. This makes it possible to realize an active PB lens. More preferably, a PSA (Polymer sustained alignment) treatment is then performed to stabilize the alignment of the interface of liquid crystal molecules, thereby making it possible to obtain an active PB lens with higher alignment stability and reliability.

Since the active PB lens has a PB lens pattern in the voltage OFF state, it condenses or diverges light depending on the incident polarization state. When the voltage is ON, the liquid crystal molecules are vertically aligned, so light is transmitted as is without converging or diverging.

In contrast to the variable focus element that combines sHWP and passive PB lens as in Embodiment 7, which has binary switching between convergence and divergence, the variable focus element that combines sHWP and active PB lens as in this modification example The focusing element can switch between three values: convergence, divergence, and transmission. As a result, smoother focus control is possible. Alternatively, the number of layers of voltage-driven elements can be reduced in order to achieve the same number of focal length steps.

(Embodiment 8)
In this embodiment, features unique to this embodiment will be mainly explained, and explanations of contents that overlap with the above-mentioned Embodiments 1 to 7 and their modifications will be omitted. In this embodiment, a head mounted display including a variable focus element 30 will be described. FIG. 31 is a schematic cross-sectional view of a head mounted display according to Embodiment 8. FIG. 32 is a schematic perspective view showing an example of the appearance of a head mounted display according to Embodiment 8.

As shown in FIGS. 31 and 32, the head mounted display 1 of this embodiment includes a display panel 1P that displays an image, a retardation plate 40, and a variable focus element 30. By using the head-mounted display 1, the light emitted from the display panel 1P such as a liquid crystal display device or an organic electroluminescent display device becomes circularly polarized light through the retardation plate 40, which passes through the variable focus element 30, visible to user U.

(Embodiment 9)
In this embodiment, features unique to this embodiment will be mainly explained, and explanations of contents that overlap with the above-mentioned Embodiments 1 to 8 and their modifications will be omitted. This embodiment is substantially the same as Embodiment 5 except that the configuration of the liquid crystal cell 11 is different.

FIG. 64 is a schematic cross-sectional view of an optical element according to Embodiment 9. FIG. 65 is a schematic cross-sectional view of a liquid crystal cell included in the optical element according to Embodiment 9. FIG. 66 is a schematic diagram illustrating the orientation of liquid crystal molecules in the first state and the second state of the optical element according to Embodiment 9. Since the alignment of liquid crystal molecules near the interface of the substrate is vertical and the orientation cannot be defined, in FIG. 66, the alignment direction of the liquid crystal molecules is defined by the electrode direction.

Note that in Embodiments 1 to 7, Modification 1 of Embodiment 7, Embodiment 8, and this embodiment, the reference orientation (0°) is the liquid crystal molecule on the first substrate 100 side in the first state. The orientation direction 311A of the liquid crystal molecules 311 on the first substrate 100 side in the first state is set to the direction when the orientation direction 311A of the liquid crystal molecules 311 is projected onto the substrate surface on the output side of the optical element 10. This corresponds to the horizontal right direction of the screen of the liquid crystal cell 11 when viewed from the side.

The liquid crystal cell 11 included in the optical element 10 of this embodiment shown in FIGS. 64 to 66 further includes a first vertical alignment film 414 disposed between the first substrate 100 and the liquid crystal layer 300, and a second vertical alignment film 424 disposed between the second substrate 200 and the second substrate 200 . The liquid crystal layer 300 contains liquid crystal molecules 310 having negative dielectric anisotropy. At least one of the first vertical alignment film 414 and the second vertical alignment film 424 controls the tilt direction of the liquid crystal molecules 310 in a state where no voltage is applied.

The electrode 11E includes, on at least one of the first substrate 100 and the second substrate 200, a planar electrode and an electrode that overlaps the planar electrode via an insulating layer and is provided with a slit portion. It is preferable. A pair of electrodes consisting of a planar electrode and an electrode that overlaps the planar electrode with an insulating layer interposed therebetween and is provided with a slit portion is also referred to as an FFS electrode.

More specifically, the liquid crystal cell 11 included in the optical element 10 of this embodiment shown in FIGS. 64 to 66 further includes a first vertical alignment film disposed between the first substrate 100 and the liquid crystal layer 300. 414, and a second vertical alignment film 424 disposed between the liquid crystal layer 300 and the second substrate 200. The liquid crystal layer 300 contains liquid crystal molecules 310 having negative dielectric anisotropy. The electrode 11E includes, on the first substrate 100, a planar first electrode 131 and a second electrode 132 that overlaps the first electrode 131 via the first insulating layer 141 and is provided with a slit portion 132S. The second substrate 200 has a solid electrode 240. In plan view, the extending direction 132A of the slit portion 132S provided in the second electrode 132 is orthogonal to the orientation direction 311X of the liquid crystal molecules 311 on the first substrate 100 side in a state where no voltage is applied.

By adopting such an aspect, as shown in FIG. 66, a voltage lower than the threshold value is applied between the first electrode 131 and the second electrode 132, and at least When a voltage equal to or higher than the threshold is applied between one side and the solid electrode 240, circularly polarized light (for example, right-handed circularly polarized light) incident on the liquid crystal cell 11 becomes first linearly polarized light after passing through the liquid crystal cell 11. That is, the first state can be realized.

Further, as shown in FIG. 66, a voltage equal to or higher than the threshold is applied between the first electrode 131 and the second electrode 132, and at least one of the first electrode 131 and the second electrode 132 is connected to the solid electrode 240. When a voltage equal to or higher than the threshold is applied during the period, the circularly polarized light (for example, right-handed circularly polarized light) incident on the liquid crystal cell 11 becomes orthogonal to the polarization direction of the first linearly polarized light in plan view after passing through the liquid crystal cell 11. The second linearly polarized light has a polarization direction of . That is, the second state can be realized.

Note that one of the first electrode 131 and the second electrode 132 is a pixel electrode, and the other is a common electrode. In FIG. 65, the first substrate 100 includes a planar electrode and an electrode provided with a slit portion in order toward the liquid crystal layer 300 side, but the arrangement of the planar electrode and the electrode provided with a slit portion is The present invention is not limited to this, and an electrode provided with a slit portion and a planar electrode may be provided in order toward the liquid crystal layer 300 side.

In this embodiment, the alignment films on the first substrate 100 side and the second substrate 200 side are vertical alignment films. Furthermore, an FFS electrode is provided on at least one substrate (first substrate 100 in this embodiment), and a voltage between the FFS substrate and a counter substrate (second substrate 200 in this embodiment) that faces the substrate provided with the FFS electrode is The liquid crystal molecules 310 are driven by. Negative type liquid crystal molecules 310 are used as the liquid crystal molecules 310, and by adding a chiral agent, the liquid crystal molecules 310 are adjusted to be oriented while being twisted by about 70 degrees. At this time, by adjusting the direction of tilt applied to the alignment film and the voltage applied between the pixel electrode and the common electrode constituting the FFS electrode, the orientation of the entire system can be rotated by 90 degrees to obtain a first state and a second state. Orientation.

In this specification, the tilt direction refers to the orientation of liquid crystal molecules in a state where no voltage is applied, and is also referred to as tilt orientation. Moreover, the tilt angle is the same as the above-mentioned pretilt angle. Also, having a tilt means that the tilt angle is less than 89.9° (more specifically, 0° or more and less than 89.9°), and not having a tilt means that the tilt angle is less than 89.9° (more specifically, 0° or more and less than 89.9°). is 89.9° or more (more specifically, 89.9° or more and 90° or less).

At least one of the liquid crystal molecules 311 on the first substrate 100 side and the liquid crystal molecules 312 on the second substrate 200 side preferably has a tilt. For example, when the liquid crystal molecules 311 on the first substrate 100 side have a tilt, the tilt direction of the liquid crystal molecules 311 on the first substrate 100 side is preferably perpendicular to the direction in which the FFS electrodes extend. More specifically, the alignment direction 311X of the liquid crystal molecules 311 on the first substrate 100 side in a state where no voltage is applied is perpendicular to the extending direction 132A of the slit portion 132S provided in the second electrode 132. is preferred. At this time, it is desirable that the tilt orientation of the liquid crystal molecules 311 on the first substrate 100 side is approximately 0° (for example, -10° or more and +10° or less), and the liquid crystal molecules 312 on the second substrate 200 side have a tilt direction. It is preferable not to do so.

Furthermore, if the liquid crystal molecules 312 on the second substrate 200 side have a tilt, it is preferable that the tilt orientation of the liquid crystal molecules 312 on the second substrate 200 side is approximately 70° (e.g., 60° or more and 80° or less), and it is preferable that the liquid crystal molecules 311 on the first substrate 100 side have no tilt.

Furthermore, both the liquid crystal molecules 311 on the first substrate 100 side and the liquid crystal molecules 312 on the second substrate 200 side may have a tilt.

When the azimuth angle of the extension direction 132A is 90°, the alignment direction 311X of the liquid crystal molecules 311 on the first substrate 100 side in the no voltage applied state is 0°, the twist angle of the liquid crystal molecules 310 is 70°, and the liquid crystal layer 300 contains negative liquid crystal molecules 310, as shown in Figures 64 to 66, when a voltage less than the threshold is applied between the first electrode 131 and the second electrode 132, and a voltage equal to or greater than the threshold is applied between the first electrode 131 and the second electrode 132 and the solid electrode 240, a first state can be realized in which the azimuth angle of the alignment direction 311A of the liquid crystal molecules 311 on the first substrate 100 side is 0° and the azimuth angle of the alignment direction 312A of the liquid crystal molecules 312 on the second substrate 200 side is 70°. Furthermore, when a voltage equal to or greater than the threshold value is applied between the first electrode 131 and the second electrode 132, and when a voltage equal to or greater than the threshold value is applied between the first electrode 131 and the second electrode 132 and the solid electrode 240, a second state can be realized in which the azimuth angle of the alignment direction 311B of the liquid crystal molecules 311 on the first substrate 100 side is 90°, and the azimuth angle of the alignment direction 312B of the liquid crystal molecules 312 on the second substrate 200 side is 160°.

The retardation Δnd of the liquid crystal layer 300 in the absence of applied voltage at a wavelength of 550 nm is preferably 180 nm or more and 280 nm or less. The refractive index anisotropy Δn of the liquid crystal layer 300 is preferably 0.12 or less, and more preferably 0.1 or less.

In this embodiment, when the azimuth angle of the alignment direction 311A of the liquid crystal molecules 311 on the first substrate 100 side in the first state is 0°, the first quarter-wave film 12 and the second quarter-wave film 13, the azimuth angle of the slow axis of the quarter wavelength film on the side far from the light emission side (in this embodiment, the slow axis 12A of the first quarter wavelength film 12) is 58° or more, 78° It is preferable that it is less than or equal to °. By adopting such an aspect, polarization modulation and polarization non-modulation can be switched over a wider band.

In this embodiment, when the azimuth angle of the alignment direction 311A of the liquid crystal molecules 311 on the first substrate 100 side in the first state is 0°, it is preferable that the azimuth angle of the slow axis of the first quarter-wave film 12 or the second quarter-wave film 13 that is closer to the light emission side (in this embodiment, the slow axis 13A of the second quarter-wave film 13) is 13° or more and 33° or less. By adopting such an embodiment, it is possible to switch between polarization modulation and polarization non-modulation over a wider band.

The angle between the slow axis 12A of the first quarter wavelength film 12 and the slow axis 13A of the second quarter wavelength film 13 is preferably 40° or more and 50° or less, and 42 It is more preferably 44° or more and 46° or less, even more preferably 45° or more, and particularly preferably 45°.

In this embodiment, the azimuth angle of the slow axis 12A of the first 1/4 wavelength film 12 is set to 58° or more and 78° or less, and the slow axis of the second 1/4 wavelength film 13 is set to 58° or more and 78° or less. By setting the azimuth angle of 13A to 13° or more and 33° or less, in the first state, the first linearly polarized light is divided into the first 1/4 wavelength film 12 and the second 1/4 wavelength film 13. By passing through the liquid crystal cell 11, the circularly polarized light (for example, right-handed circularly polarized light) that has entered the liquid crystal cell 11 is converted into circularly polarized light (for example, left-handed circularly polarized light) that has a different polarization state (for example, left-handed circularly polarized light). In this way, in the first state, the circularly polarized light incident on the optical element 10 is converted into circularly polarized light with a different polarization state (for example, right-handed circularly polarized light is converted into left-handed circularly polarized light), and the output polarization modulation is broadband. It is realized by Further, the second linearly polarized light passes through the first 1/4 wavelength film 12 and the second 1/4 wavelength film 13 so that the polarization state is the same as that of the circularly polarized light incident on the liquid crystal cell 11. It is emitted as circularly polarized light (for example, right-handed circularly polarized light) in a wide band. In this way, in the second state, polarization non-modulation is realized in a wide band, in which the circularly polarized light incident on the optical element 10 is output while remaining in the same polarization state (for example, right-handed circularly polarized light).

Figure 67 is a diagram showing the Stokes plots of each layer in the first state of the optical element according to embodiment 9. Figure 68 is a schematic diagram explaining the polarization state in the first state of the optical element according to embodiment 9. Figure 67 shows the polarization state (role of each layer) when light passes through each layer in the first state. The principle of polarization modulation of the optical element 10 according to embodiment 9 will be explained in detail using the Poincaré sphere in Figure 67 and Figure 68.

As shown in (1) of FIG. 67, right-handed circularly polarized light (S3=+1) enters the liquid crystal cell 11.

After passing through the 70° twisted liquid crystal cell 11, the light is converted once into the polarization state shown in plot (2) in Figure 67. Each plot point represents a different wavelength from 380 nm to 780 nm. Light with a wavelength of around 550 nm is linearly polarized (on the equator on the Poincaré sphere), but other wavelengths are plotted in the northern hemisphere of the Poincaré sphere and are elliptically polarized.

Then it passes through the first quarter-wave film 12 (specifically, a quarter-wave film with reverse wavelength dispersion), resulting in plot (3) in Figure 67.

Furthermore, when passing through the second 1/4 wavelength film 13 (specifically, a 1/4 wavelength film with flat wavelength dispersion), almost all the wavelengths are left circular as shown in the plot (4) of FIG. It is emitted as polarized light (the position of the south pole on the Poincaré sphere). That is, as shown in FIG. 68, it can be seen that the right-handed circularly polarized light was modulated into the left-handed circularly polarized light.

Similarly, in the second state (non-modulated), the light becomes linearly polarized once after passing through the liquid crystal cell 11 twisted by 70°. However, since the entire orientation of the liquid crystal cell 11 is rotated by 90 degrees, the linearly polarized light differs from the first state (during modulation) by about 90 degrees. Then, after passing through the first 1/4 wavelength film 12 and the second 1/4 wavelength film 13, all wavelengths become right-handed circularly polarized light. That is, right-handed circularly polarized light can be emitted as right-handed circularly polarized light, and is not modulated.

In this way, the first state and the second state have the same orientation of the liquid crystal molecules 310, which is 70° twist, but the entire system is different by 90°. By using the optical element 10 of this embodiment, it is possible to reversibly switch between two states, the first state and the second state. A switchable half wave plate (sHWP) element can be realized.

The second 1/4 wavelength film 13 (specifically, a 1/4 wavelength film with flat wavelength dispersion) is, for example, a positive A plate or a negative A plate. The second 1/4 wavelength film 13 (specifically, a 1/4 wavelength film with flat wavelength dispersion) is preferably a negative A plate. By adopting such an aspect, viewing angle characteristics during non-modulation can be improved.

The pitch of the second electrode 132 provided with the slit portions 132S is preferably 1 μm or more and 5 μm or less. By reducing the pitch in this manner, the orientation of the liquid crystal molecules 310 changes more uniformly, and the modulation characteristics can be improved.

The solid electrode 240 is an electrode that does not have slits or openings at least in the area that overlaps with the optical opening of the pixel in a planar view. The solid electrode 240, the pixel electrode and the common electrode, can be formed by forming a single layer or multiple layers of transparent conductive materials such as indium tin oxide (ITO), indium zinc oxide (IZO), zinc oxide (ZnO), tin oxide (SnO), or alloys thereof by sputtering or the like, and then patterning the layers using photolithography.

The liquid crystal molecules 310 of this embodiment are negative type liquid crystal molecules 310. With this embodiment, by applying a large vertical voltage between the first substrate 100 and the second substrate 200, the negative liquid crystal molecules 310 can be tilted and horizontally aligned. In the first state and the second state, the voltage difference between the first electrode 131 and the second electrode 132 and the solid electrode 240 is preferably 1V or more, more preferably 3V or more, and 4V or more. It is more preferable that By adopting such an aspect, the liquid crystal molecules 310 can be horizontally aligned more effectively. Although the upper limit of the voltage difference between the first electrode 131 and the second electrode 132 and the solid electrode 240 is not particularly limited, the voltage difference between the first electrode 131 and the second electrode 132 and the solid electrode 240 is as follows: For example, it is 7V or less. The voltage difference between the first electrode 131 and the second electrode 132 and the solid electrode 240 is preferably 1V or more and 7V or less, more preferably 3V or more and 7V or less, and 4V or more and 7V or less. It is more preferable that

Furthermore, between the first electrode 131 and the second electrode 132, a weak voltage can be applied between the pixel electrode and the common electrode to control the in-plane orientation direction of the liquid crystal molecules 310. When the liquid crystal molecules 310 are negative type liquid crystal molecules, the liquid crystal molecules 310 are oriented in the extension direction of the slit portion 132S (direction perpendicular to the electric field) in the plane. In this case, applying a strong transverse electric field interferes with the twisting of the liquid crystal orientation due to chiral force, so it is preferable that the transverse electric field is weak.

When the voltage difference between the first electrode 131 and the second electrode 132 and the solid electrode 240 is 7V or less, for example, the voltage difference between the first electrode 131 and the second electrode 132 in the first state is It is preferable that it is 0.6V or less. Moreover, it is preferable that the potential difference between the first electrode 131 and the second electrode 132 in the second state is 2V or less. Although the lower limit of the voltage difference between the first electrode 131 and the second electrode 132 in the first state is not particularly limited, the voltage difference between the first electrode 131 and the second electrode 132 in the first state is, for example, , 0.01V or more. Further, the lower limit value of the voltage difference between the first electrode 131 and the second electrode 132 in the second state is not particularly limited, but the voltage difference between the first electrode 131 and the second electrode 132 in the second state is , for example, 0.6V or more.

The voltage difference between the first electrode 131 and the second electrode 132 in the first state is preferably 0.01V or more and 0.6V or less. Moreover, it is preferable that the potential difference between the first electrode 131 and the second electrode 132 in the second state is 0.6V or more and 2V or less.

As the first vertical alignment film 414 and the second vertical alignment film 424, those similar to those in Embodiment 5 can be used. In this embodiment, since vertical alignment films are arranged on both substrate sides, it is possible to realize an optical element 10 with higher productivity than when horizontal alignment films are arranged.

At least one of the first vertical alignment film 414 and the second vertical alignment film 424 is preferably a weak anchoring vertical alignment film. By adopting such an aspect, polarization modulation and polarization non-modulation can be switched over a wider band and at a lower voltage. Here, the weakly anchoring vertical alignment film may be weakly anchored in at least one of the polar angle and the azimuthal angle.

Preferably, the light incident on the optical element 10 is circularly polarized light. By adopting such an aspect, it is possible to realize the optical element 10 that can switch the polarization state of circularly polarized light.

(Modification of Embodiment 9)
In the ninth embodiment, the voltage difference between the first electrode 131 and the second electrode 132 and the solid electrode 240 in the first state and the second state is preferably 8V or more. By adopting such an aspect, the liquid crystal molecules 310 can be horizontally aligned more effectively. Although the upper limit of the voltage difference between the first electrode 131 and the second electrode 132 and the solid electrode 240 is not particularly limited, the voltage difference between the first electrode 131 and the second electrode 132 and the solid electrode 240 is as follows. For example, it is 20V or less. The voltage difference between the first electrode 131 and the second electrode 132 and the solid electrode 240 is preferably 8V or more and 20V or less.

When the voltage difference between the first electrode 131 and the second electrode 132 and the solid electrode 240 is 8V or more, for example, the voltage difference between the first electrode 131 and the second electrode 132 in the first state is It is preferable that it is 2V or less. Moreover, it is preferable that the potential difference between the first electrode 131 and the second electrode 132 in the second state is 3V or less. Although the lower limit of the voltage difference between the first electrode 131 and the second electrode 132 in the first state is not particularly limited, the voltage difference between the first electrode 131 and the second electrode 132 in the first state is, for example, , 0.01V or more. Further, the lower limit value of the voltage difference between the first electrode 131 and the second electrode 132 in the second state is not particularly limited, but the voltage difference between the first electrode 131 and the second electrode 132 in the second state is , for example, 1.1V or more.

The voltage difference between the first electrode 131 and the second electrode 132 in the first state is preferably 0.01V or more and 2V or less. Moreover, it is preferable that the potential difference between the first electrode 131 and the second electrode 132 in the second state is 1.1 V or more and 3 V or less.

By applying a voltage as in this modified example, the liquid crystal molecules 310 near the interface are also tilted, making it possible to realize a sHWP with a wide viewing angle. In this case, the cell thickness, twist pitch, and angle of the retardation film can be changed as appropriate.

(Embodiment 10)
In this embodiment, the features unique to this embodiment will be mainly described, and the description of the contents overlapping with the above-mentioned embodiments 1 to 9 and their modifications will be omitted. This embodiment is substantially the same as embodiment 9, except that the configuration of the liquid crystal cell 11 and the preferred voltages applied to the electrodes are different.

FIG. 69 is a schematic cross-sectional view of an optical element according to Embodiment 10. FIG. 70 is a schematic cross-sectional view of a liquid crystal cell included in the optical element according to Embodiment 10. FIG. 71 is a schematic diagram illustrating the orientation of liquid crystal molecules in the first state and the second state of the optical element according to Embodiment 10. Since the alignment of liquid crystal molecules near the interface of the substrate is vertical and the orientation cannot be defined, in FIG. 71, the alignment direction of the liquid crystal molecules is defined by the electrode direction.

In this embodiment, the reference direction (0°) is the orientation direction 311A of the liquid crystal molecules 311 on the first substrate 100 side in the first state projected onto the substrate surface on the output side of the optical element 10. The alignment direction 311A of the liquid crystal molecules 311 on the first substrate 100 side in the first state corresponds to the horizontal right direction of the screen of the liquid crystal cell 11 when the optical element 10 is viewed from the output side.

The liquid crystal cell 11 included in the optical element 10 of this embodiment shown in FIGS. 69 to 71 further includes a first vertical alignment film 414 disposed between the first substrate 100 and the liquid crystal layer 300, and a second vertical alignment film 424 disposed between the second substrate 200 and the second substrate 200 . The liquid crystal layer 300 contains liquid crystal molecules 310 having negative dielectric anisotropy. The electrode 11E includes, on the first substrate 100, a planar first electrode 131 and a second electrode 132 that overlaps the first electrode 131 via the first insulating layer 141 and is provided with a slit portion. In the second substrate 200, a planar third electrode 231 and a fourth electrode 232 which overlaps the third electrode 231 via the second insulating layer 241 and is provided with a slit portion 232S are provided. have In plan view, the extending direction 132A of the slit portion 132S provided in the second electrode 132 is arranged obliquely with respect to the extending direction 232A of the slit portion 232S provided in the fourth electrode 232, and no voltage is applied. is parallel to the alignment direction 311X of the liquid crystal molecules 311 on the first substrate 100 side, and the extending direction 232A of the slit portion 232S provided in the fourth electrode 232 is parallel to the alignment direction 311 is parallel to the orientation direction 312X.

By adopting such an aspect, as shown in FIG. 71, when a voltage is applied between the first electrode 131 and the second electrode 132 and a voltage is not applied between the third electrode 231 and the fourth electrode 232, In addition, the circularly polarized light (for example, right-handed circularly polarized light) incident on the liquid crystal cell 11 becomes the first linearly polarized light after passing through the liquid crystal cell 11. That is, the first state can be realized.

Also, as shown in FIG. 71, when no voltage is applied between the first electrode 131 and the second electrode 132 and a voltage is applied between the third electrode 231 and the fourth electrode 232, circularly polarized light (e.g., right-handed circularly polarized light) incident on the liquid crystal cell 11 passes through the liquid crystal cell 11 and becomes second linearly polarized light having a polarization direction perpendicular to the polarization direction of the first linearly polarized light in a planar view. In other words, the second state can be realized.

Note that one of the first electrode 131 and the second electrode 132 is a pixel electrode, and the other is a common electrode. One of the third electrode 231 and the fourth electrode 232 is a pixel electrode, and the other is a common electrode. In FIG. 70, both the first substrate 100 and the second substrate 200 are provided with electrodes provided with a planar electrode and a slit portion in order toward the liquid crystal layer 300 side. The arrangement of the electrodes is not limited to this, and an electrode provided with a slit portion and a planar electrode may be provided in order toward the liquid crystal layer 300 side.

At least one of the liquid crystal molecules 311 on the first substrate 100 side and the liquid crystal molecules 312 on the second substrate 200 side preferably has a tilt. For example, when the liquid crystal molecules 311 on the first substrate 100 side have a tilt, it is preferable that the tilt orientation of the liquid crystal molecules 311 on the first substrate 100 side and the orientation of the extension direction of the FFS electrode on the first substrate 100 side are parallel. More specifically, it is preferable that the orientation direction 311X of the liquid crystal molecules 311 on the first substrate 100 side in a no voltage application state and the orientation direction 132A of the slit portion 132S provided in the second electrode 132 are parallel. At this time, it is preferable that the tilt orientation of the liquid crystal molecules 311 on the first substrate 100 side is approximately 0° (for example, -10° or more and +10° or less), and it is preferable that the liquid crystal molecules 312 on the second substrate 200 side do not have a tilt.

Further, when the liquid crystal molecules 312 on the second substrate 200 side have a tilt, the tilt direction of the liquid crystal molecules 312 on the second substrate 200 side and the orientation of the stretching direction of the FFS electrode on the second substrate 200 side should be parallel. is preferred. More specifically, the alignment direction 312X of the liquid crystal molecules 312 on the second substrate 200 side in a state where no voltage is applied is parallel to the extending direction 232A of the slit portion 232S provided in the fourth electrode 232. It is preferable. At this time, it is desirable that the tilt orientation of the liquid crystal molecules 312 on the second substrate 200 side is approximately 160° (for example, 150° or more and 170° or less), and the liquid crystal molecules 311 on the first substrate 100 side should have a tilt direction. Preferably not.

Furthermore, both the liquid crystal molecules 311 on the first substrate 100 side and the liquid crystal molecules 312 on the second substrate 200 side may have a tilt.

In plan view, the angle γ between the stretching direction 132A and the stretching direction 232A (where γ is a real number greater than 0° and less than 90°), and the twist angle C of the liquid crystal molecules 310 included in the liquid crystal layer 300 are: In the first state and the second state, it is preferable that the above (Formula CX1) is satisfied, it is more preferable that the above (Formula CX2) is satisfied, and it is still more preferable that the above (Formula CX3) is satisfied. By adopting such an aspect, polarization modulation and polarization non-modulation can be effectively switched over a wide band.

The twist angle C is preferably 60° or more and 80° or less, more preferably 64° or more and 76° or less, and even more preferably 68° or more and 72° or less. By adopting such an aspect, polarization modulation and polarization non-modulation can be switched more effectively over a wide band.

The azimuth angle of the stretching direction 132A is 0°, the alignment direction 311X of the liquid crystal molecules 311 on the first substrate 100 side in the state of no voltage application is 0°, the azimuth angle of the stretching direction 232A is 160°, and no voltage is applied. When the alignment direction 312X of the liquid crystal molecules 312 on the second substrate 200 side in the applied state is 160°, the twist angle of the liquid crystal molecules 310 is 70°, and the liquid crystal layer 300 contains negative liquid crystal molecules 310. , as shown in FIGS. 69 to 71, when a voltage is applied between the first electrode 131 and the second electrode 132 and a voltage is not applied between the third electrode 231 and the fourth electrode 232, the first substrate A first state can be realized in which the azimuth angle of the orientation direction 311A of the liquid crystal molecules 311 on the 100 side is 0°, and the azimuth angle of the orientation direction 312A of the liquid crystal molecules 312 on the second substrate 200 side is 70°. Furthermore, when no voltage is applied between the first electrode 131 and the second electrode 132 and a voltage is applied between the third electrode 231 and the fourth electrode 232, the alignment direction of the liquid crystal molecules 311 on the first substrate 100 side A second state can be realized in which the azimuth angle of the liquid crystal molecules 311B is 90° and the azimuth angle of the alignment direction 312B of the liquid crystal molecules 312 on the second substrate 200 side is 160°.

The pitch of the second electrode 132 provided with the slit portions 132S is preferably 1 μm or more and 5 μm or less. By reducing the pitch in this way, the orientation of the liquid crystal molecules 310 changes more uniformly, and the modulation characteristics can be improved. Further, the pitch of the fourth electrode 232 provided with the slit portion 232S is preferably 1 μm or more and 5 μm or less. By adopting such an embodiment, the orientation of the liquid crystal molecules 310 can be changed more uniformly, and the modulation characteristics can be improved.

The liquid crystal molecules 310 of this embodiment are negative type liquid crystal molecules 310. With this embodiment, by applying a large vertical voltage between the first substrate 100 and the second substrate 200, the negative liquid crystal molecules 310 can be tilted and horizontally aligned. In the first state and the second state, the voltage difference between the first electrode 131 and the second electrode 132 and the third electrode 231 and the fourth electrode 232 is preferably 1V or more, and preferably 3V or more. More preferably, it is 4V or more. By adopting such an aspect, the liquid crystal molecules 310 can be horizontally aligned more effectively. Although the upper limit of the voltage difference between the first electrode 131 and the second electrode 132 and the third electrode 231 and the fourth electrode 232 is not particularly limited, The voltage difference between the electrode 232 and the electrode 232 is, for example, 7V or less. The voltage difference between the first electrode 131 and the second electrode 132 and the third electrode 231 and the fourth electrode 232 is preferably 1V or more and 7V or less, more preferably 3V or more and 7V or less, More preferably, the voltage is 4V or more and 7V or less.

Further, a weak voltage is applied between the pixel electrode and the common electrode between the first electrode 131 and the second electrode 132 and between the third electrode 231 and the fourth electrode 232, respectively, to change the in-plane alignment direction of the liquid crystal molecules 310. can be controlled. When the liquid crystal molecules 310 are negative type liquid crystal molecules, the liquid crystal molecules 310 are oriented in the direction in which the slit portions 132S and 232S extend (the direction perpendicular to the electric field) in the plane. At this time, if a strong transverse electric field is applied, the alignment twist of the liquid crystal due to chiral force will be disturbed, so it is preferable that the transverse electric field is weak.

When the voltage difference between the first electrode 131 and the second electrode 132 and the third electrode 231 and the fourth electrode 232 is 7V or less, for example, the voltage difference between the first electrode 131 and the second electrode 132 in the first state is preferably 2V or less. The voltage difference between the third electrode 231 and the fourth electrode 232 in the first state is preferably 0.6V or less. The lower limit value of the voltage difference between the first electrode 131 and the second electrode 132 in the first state is not particularly limited, but the voltage difference between the first electrode 131 and the second electrode 132 in the first state is, for example, 0.7V or more. In addition, the lower limit value of the voltage difference between the third electrode 231 and the fourth electrode 232 in the first state is not particularly limited, but the voltage difference between the third electrode 231 and the fourth electrode 232 in the first state is, for example, 0.01V or more.

The voltage difference between the first electrode 131 and the second electrode 132 in the first state is preferably 0.7V or more and 2V or less. The voltage difference between the third electrode 231 and the fourth electrode 232 in the first state is preferably 0.01V or more and 0.6V or less.

In addition, the voltage difference between the first electrode 131 and the second electrode 132 in the second state is preferably 0.6 V or less. The voltage difference between the third electrode 231 and the fourth electrode 232 in the second state is preferably 2 V or less. The lower limit of the voltage difference between the first electrode 131 and the second electrode 132 in the second state is not particularly limited, but the voltage difference between the first electrode 131 and the second electrode 132 in the second state is, for example, 0.01 V or more. In addition, the lower limit of the voltage difference between the third electrode 231 and the fourth electrode 232 in the second state is not particularly limited, but the voltage difference between the third electrode 231 and the fourth electrode 232 in the second state is, for example, 0.7 V or more.

The voltage difference between the first electrode 131 and the second electrode 132 in the second state is preferably 0.01 V or more and 0.6 V or less. The voltage difference between the third electrode 231 and the fourth electrode 232 in the second state is preferably 0.7 V or more and 2 V or less.

As the first vertical alignment film 414 and the second vertical alignment film 424, those similar to those in Embodiment 5 can be used. In this embodiment, since vertical alignment films are arranged on both substrate sides, it is possible to realize an optical element 10 with higher productivity than when horizontal alignment films are arranged.

At least one of the first vertical alignment film 414 and the second vertical alignment film 424 is preferably a weak anchoring vertical alignment film. By adopting such an aspect, polarization modulation and polarization non-modulation can be switched over a wider band and at a lower voltage. Here, the weakly anchoring vertical alignment film may be weakly anchored in at least one of the polar angle and the azimuthal angle.

(Modification of Embodiment 10)
In the tenth embodiment, the voltage difference between the first electrode 131 and the second electrode 132 and the third electrode 231 and the fourth electrode 232 in the first state and the second state is preferably 8V or more. By adopting such an aspect, the liquid crystal molecules 310 can be horizontally aligned more effectively. Although the upper limit of the voltage difference between the first electrode 131 and the second electrode 132 and the third electrode 231 and the fourth electrode 232 is not particularly limited, The voltage difference between the electrode 232 and the electrode 232 is, for example, 20V or less. The voltage difference between the first electrode 131 and the second electrode 132 and the third electrode 231 and the fourth electrode 232 is preferably 8V or more and 20V or less.

When the voltage difference between the first electrode 131 and the second electrode 132 and the third electrode 231 and the fourth electrode 232 is 8V or more, for example, the difference between the first electrode 131 and the second electrode 132 in the first state It is preferable that the voltage difference is 3V or less. The voltage difference between the third electrode 231 and the fourth electrode 232 in the first state is preferably 2V or less. Although the lower limit of the voltage difference between the first electrode 131 and the second electrode 132 in the first state is not particularly limited, the voltage difference between the first electrode 131 and the second electrode 132 in the first state is, for example, , 1.1V or more. Further, the lower limit of the voltage difference between the third electrode 231 and the fourth electrode 232 in the first state is not particularly limited, but the voltage difference between the third electrode 231 and the fourth electrode 232 in the first state is , for example, 0.01V or more.

The voltage difference between the first electrode 131 and the second electrode 132 in the first state is preferably 1.1V or more and 3V or less. The voltage difference between the third electrode 231 and the fourth electrode 232 in the first state is preferably 0.01V or more and 2V or less.

Moreover, it is preferable that the voltage difference between the first electrode 131 and the second electrode 132 in the second state is 2V or less. The voltage difference between the third electrode 231 and the fourth electrode 232 in the second state is preferably 3V or less. Although the lower limit of the voltage difference between the first electrode 131 and the second electrode 132 in the second state is not particularly limited, the voltage difference between the first electrode 131 and the second electrode 132 in the second state is, for example, , 0.01V or more. Further, the lower limit value of the voltage difference between the third electrode 231 and the fourth electrode 232 in the second state is not particularly limited, but the voltage difference between the third electrode 231 and the fourth electrode 232 in the second state is , for example, 1.1V or more.

The voltage difference between the first electrode 131 and the second electrode 132 in the second state is preferably 0.01V or more and 2V or less. The voltage difference between the third electrode 231 and the fourth electrode 232 in the second state is preferably 1.1V or more and 3V or less.

By applying a voltage as in this modification, even the liquid crystal molecules 310 near the interface are tilted, so it is possible to realize a sHWP with a wide viewing angle. At this time, the cell thickness, twist pitch, and angle of the retardation film can be changed as appropriate.

(Embodiment 11)
In this embodiment, the features unique to this embodiment will be mainly described, and the description of the contents overlapping with those of the above-mentioned embodiments 1 to 10 and their modifications will be omitted. This embodiment is substantially the same as embodiment 9, except that the configuration of the liquid crystal cell 11, the preferred azimuth angles of the slow axis 12A of the first ¼ wavelength film 12 and the slow axis 13A of the second ¼ wavelength film 13, and the preferred voltage applied to the electrodes are different.

Figure 72 is a cross-sectional schematic diagram of an optical element according to embodiment 11. Figure 73 is a cross-sectional schematic diagram of a liquid crystal cell provided in the optical element according to embodiment 11. Figure 74 is a schematic diagram explaining the alignment of liquid crystal molecules in the first state and the second state of the optical element according to embodiment 11. Since the alignment of the liquid crystal molecules near the interface of the substrates is vertical and the orientation cannot be specified, in Figure 74 the alignment direction of the liquid crystal molecules is specified by the electrode direction.

In this embodiment, the reference direction (0°) is the orientation direction 311A of the liquid crystal molecules 311 on the first substrate 100 side in the first state projected onto the substrate surface on the output side of the optical element 10. The alignment direction 311A of the liquid crystal molecules 311 on the first substrate 100 side in the first state corresponds to the horizontal right direction of the screen of the liquid crystal cell 11 when the optical element 10 is viewed from the output side.

The liquid crystal cell 11 included in the optical element 10 of this embodiment shown in FIGS. 72 to 74 further includes a first vertical alignment film 414 disposed between the first substrate 100 and the liquid crystal layer 300, and a second vertical alignment film 424 disposed between the second substrate 200 and the second substrate 200 . The liquid crystal layer 300 contains liquid crystal molecules 310 having negative dielectric anisotropy. The electrode 11E includes, on the first substrate 100, a planar first electrode 131 and a second electrode 132 that overlaps the first electrode 131 via the first insulating layer 141 and is provided with a slit portion. In the second substrate 200, a planar third electrode 231 and a fourth electrode 232 which overlaps the third electrode 231 via the second insulating layer 241 and is provided with a slit portion 232S are provided. have In a plan view, the orientation direction 311X of the liquid crystal molecules 311 on the first substrate 100 side in a state where no voltage is applied is the extension direction 132A of the slit portion 132S provided in the second electrode 132 and the slit portion provided in the fourth electrode 232. 232S, and perpendicular to the stretching direction 132A of the slit portion 132S provided in the second electrode 132, and with respect to the stretching direction 232A of the slit portion 232S provided in the fourth electrode 232. It is placed diagonally.

By adopting such an aspect, as shown in FIG. 74, when a voltage is applied between the first electrode 131 and the second electrode 132 and a voltage is not applied between the third electrode 231 and the fourth electrode 232, In addition, the circularly polarized light (for example, right-handed circularly polarized light) incident on the liquid crystal cell 11 becomes the first linearly polarized light after passing through the liquid crystal cell 11. That is, the first state can be realized.

Further, as shown in FIG. 74, when no voltage is applied between the first electrode 131 and the second electrode 132 and a voltage is applied between the third electrode 231 and the fourth electrode 232, the incident light enters the liquid crystal cell 11. When the circularly polarized light (for example, right-handed circularly polarized light) passes through the liquid crystal cell 11, it becomes second linearly polarized light having a polarization direction perpendicular to the polarization direction of the first linearly polarized light in plan view. That is, the second state can be realized.

Note that one of the first electrode 131 and the second electrode 132 is a pixel electrode, and the other is a common electrode. One of the third electrode 231 and the fourth electrode 232 is a pixel electrode, and the other is a common electrode. In FIG. 73, both the first substrate 100 and the second substrate 200 are provided with electrodes provided with a planar electrode and a slit portion in order toward the liquid crystal layer 300 side. The arrangement of the electrodes is not limited to this, and an electrode provided with a slit portion and a planar electrode may be provided in order toward the liquid crystal layer 300 side.

At least one of the liquid crystal molecules 311 on the first substrate 100 side and the liquid crystal molecules 312 on the second substrate 200 side preferably has a tilt. For example, when the liquid crystal molecules 311 on the first substrate 100 side have a tilt, the tilt direction of the liquid crystal molecules 311 on the first substrate 100 side may be orthogonal to the direction of stretching of the FFS electrode on the first substrate 100 side. preferable. More specifically, the alignment direction 311X of the liquid crystal molecules 311 on the first substrate 100 side in a state where no voltage is applied is perpendicular to the extending direction 132A of the slit portion 132S provided in the second electrode 132. is preferred. At this time, it is desirable that the tilt direction of the liquid crystal molecules 311 on the first substrate 100 side is approximately -45° (for example, -55° or more and -35° or less), and the liquid crystal molecules 312 on the second substrate 200 side are tilted. It is preferable not to have. Further, the liquid crystal molecules 312 on the second substrate 200 side may have a tilt, and the liquid crystal molecules 311 on the first substrate 100 side may not have a tilt. Furthermore, both the liquid crystal molecules 311 on the first substrate 100 side and the liquid crystal molecules 312 on the second substrate 200 side may have a tilt.

In plan view, it is preferable that the angle δ (δ is a real number greater than 0° and less than 90°) between the alignment direction 311X and the stretching direction 232A and the twist angle D1 of the liquid crystal molecules 310 contained in the liquid crystal layer 300 satisfy the following formula (DX1) in the first state and the second state. By adopting such an embodiment, it is possible to effectively switch between polarization modulation and polarization non-modulation in a wide band.
80°-D1≦δ≦100°-D1 (Formula DX1)

The twist angle D1 is preferably 60° or more and 80° or less, more preferably 64° or more and 76° or less, and even more preferably 68° or more and 72° or less. By adopting such an aspect, polarization modulation and polarization non-modulation can be switched more effectively over a wide band.

The azimuth angle of the stretching direction 132A is 90°, the orientation direction 311X of the liquid crystal molecules 311 on the first substrate 100 side in the state of no voltage application is 0°, the azimuth angle of the stretching direction 232A is 160°, When the twist angle of 310 is 70° and the liquid crystal layer 300 contains negative liquid crystal molecules 310, a voltage is applied between the first electrode 131 and the second electrode 132 as shown in FIGS. 72 to 74. In this state, when no voltage is applied between the third electrode 231 and the fourth electrode 232, the azimuth angle of the alignment direction 311A of the liquid crystal molecules 311 on the first substrate 100 side is 0°, and It is possible to realize a first state in which the azimuth angle of the alignment direction 312A of the liquid crystal molecules 312 is 70°. Furthermore, when no voltage is applied between the first electrode 131 and the second electrode 132 and a voltage is applied between the third electrode 231 and the fourth electrode 232, the alignment direction of the liquid crystal molecules 311 on the first substrate 100 side A second state can be realized in which the azimuth angle of the liquid crystal molecules 311B is 90° and the azimuth angle of the orientation direction 312B of the liquid crystal molecules 312 on the second substrate 200 side is 160°.

When the azimuth angle of the orientation direction 311A of the liquid crystal molecules 311 on the first substrate 100 side in the first state is 0°, the light beam of the first 1/4 wavelength film 12 and the second 1/4 wavelength film 13 is The azimuth angle of the slow axis of the 1/4 wavelength film on the side far from the emission side (in this embodiment, the slow axis 12A of the first 1/4 wavelength film 12) is 58° or more and 78° or less. is preferred. By adopting such an aspect, polarization modulation and polarization non-modulation can be switched over a wider band.

When the azimuth angle of the orientation direction 311A of the liquid crystal molecules 311 on the first substrate 100 side in the first state is 0°, the light beam of the first 1/4 wavelength film 12 and the second 1/4 wavelength film 13 is The azimuth angle of the slow axis of the 1/4 wavelength film on the side closer to the output side (in this embodiment, the slow axis 13A of the second 1/4 wavelength film 13) is 13° or more and 33° or less. is preferred. By adopting such an aspect, polarization modulation and polarization non-modulation can be switched over a wider band.

The angle between the slow axis 12A of the first quarter wavelength film 12 and the slow axis 13A of the second quarter wavelength film 13 is preferably 40° or more and 50° or less, and 42 It is more preferably 44° or more and 46° or less, even more preferably 45° or more, and particularly preferably 45°.

In this embodiment, the azimuth angle of the alignment direction 311A of the liquid crystal molecules 311 on the first substrate 100 side in the first state is set to 0°, the azimuth angle of the slow axis 12A of the first quarter-wave film 12 is set to 58° or more and 78° or less, and the azimuth angle of the slow axis 13A of the second quarter-wave film 13 is set to 13° or more and 33° or less. In the first state, the first linearly polarized light passes through the first quarter-wave film 12 and the second quarter-wave film 13, and is converted in a wide band into circularly polarized light (e.g., left circularly polarized light) having a different polarization state from the circularly polarized light (e.g., right circularly polarized light) incident on the liquid crystal cell 11. In this way, in the first state, polarization modulation is realized in a wide band in which the circularly polarized light incident on the optical element 10 is converted into circularly polarized light with a different polarization state (e.g., right circularly polarized light is converted into left circularly polarized light) and output. Furthermore, the second linearly polarized light passes through the first quarter-wave film 12 and the second quarter-wave film 13, and is emitted in a wide band as circularly polarized light (e.g., right-handed circularly polarized light) having the same polarization state as the circularly polarized light incident on the liquid crystal cell 11. In this way, in the second state, polarization non-modulation is realized in a wide band, in which the circularly polarized light incident on the optical element 10 is emitted in the same polarization state (e.g., right-handed circularly polarized light).

The pitch of the second electrode 132 provided with the slit portions 132S is preferably 1 μm or more and 5 μm or less. By reducing the pitch in this way, the orientation of the liquid crystal molecules 310 changes more uniformly, and the modulation characteristics can be improved. Further, the pitch of the fourth electrode 232 provided with the slit portion 232S is preferably 1 μm or more and 5 μm or less. By adopting such an embodiment, the orientation of the liquid crystal molecules 310 can be changed more uniformly, and the modulation characteristics can be improved.

The liquid crystal molecules 310 of this embodiment are negative type liquid crystal molecules 310. With this embodiment, by applying a large vertical voltage between the first substrate 100 and the second substrate 200, the negative liquid crystal molecules 310 can be tilted and horizontally aligned. In the first state and the second state, the voltage difference between the first electrode 131 and the second electrode 132 and the third electrode 231 and the fourth electrode 232 is preferably 1V or more, and preferably 3V or more. More preferably, it is 4V or more. By adopting such an aspect, the liquid crystal molecules 310 can be horizontally aligned more effectively. Although the upper limit of the voltage difference between the first electrode 131 and the second electrode 132 and the third electrode 231 and the fourth electrode 232 is not particularly limited, The voltage difference between the electrode 232 and the electrode 232 is, for example, 7V or less. The voltage difference between the first electrode 131 and the second electrode 132 and the third electrode 231 and the fourth electrode 232 is preferably 1V or more and 7V or less, more preferably 3V or more and 7V or less, More preferably, the voltage is 4V or more and 7V or less.

Further, a weak voltage is applied between the pixel electrode and the common electrode between the first electrode 131 and the second electrode 132 and between the third electrode 231 and the fourth electrode 232, respectively, to change the in-plane alignment direction of the liquid crystal molecules 310. can be controlled. When the liquid crystal molecules 310 are negative type liquid crystal molecules, the liquid crystal molecules 310 are oriented in the direction in which the slit portions 132S and 232S extend (the direction perpendicular to the electric field) in the plane. At this time, if a strong transverse electric field is applied, the alignment twist of the liquid crystal due to chiral force will be disturbed, so it is preferable that the transverse electric field is weak.

If the voltage difference between the first electrode 131 and the second electrode 132 and the third electrode 231 and the fourth electrode 232 is 7V or less, for example, the difference between the first electrode 131 and the second electrode 132 in the first state It is preferable that the voltage difference is 2V or less. The voltage difference between the third electrode 231 and the fourth electrode 232 in the first state is preferably 0.6V or less. Although the lower limit of the voltage difference between the first electrode 131 and the second electrode 132 in the first state is not particularly limited, the voltage difference between the first electrode 131 and the second electrode 132 in the first state is, for example, , 0.7V or more. Further, the lower limit of the voltage difference between the third electrode 231 and the fourth electrode 232 in the first state is not particularly limited, but the voltage difference between the third electrode 231 and the fourth electrode 232 in the first state is , for example, 0.01V or more.

The voltage difference between the first electrode 131 and the second electrode 132 in the first state is preferably 0.7V or more and 2V or less. The voltage difference between the third electrode 231 and the fourth electrode 232 in the first state is preferably 0.01V or more and 0.6V or less.

In addition, the voltage difference between the first electrode 131 and the second electrode 132 in the second state is preferably 0.6 V or less. The voltage difference between the third electrode 231 and the fourth electrode 232 in the second state is preferably 2 V or less. The lower limit of the voltage difference between the first electrode 131 and the second electrode 132 in the second state is not particularly limited, but the voltage difference between the first electrode 131 and the second electrode 132 in the second state is, for example, 0.01 V or more. In addition, the lower limit of the voltage difference between the third electrode 231 and the fourth electrode 232 in the second state is not particularly limited, but the voltage difference between the third electrode 231 and the fourth electrode 232 in the second state is, for example, 0.7 V or more.

The voltage difference between the first electrode 131 and the second electrode 132 in the second state is preferably 0.01V or more and 0.6V or less. The voltage difference between the third electrode 231 and the fourth electrode 232 in the second state is preferably 0.7V or more and 2V or less.

As the first vertical alignment film 414 and the second vertical alignment film 424, those similar to those in Embodiment 5 can be used. In this embodiment, since vertical alignment films are arranged on both substrate sides, it is possible to realize an optical element 10 with higher productivity than when horizontal alignment films are arranged.

At least one of the first vertical alignment film 414 and the second vertical alignment film 424 is preferably a weak anchoring vertical alignment film. By adopting such an aspect, polarization modulation and polarization non-modulation can be switched over a wider band and at a lower voltage. Here, the weakly anchoring vertical alignment film may be weakly anchored in at least one of the polar angle and the azimuthal angle.

(Modification of the eleventh embodiment)
In the above-mentioned embodiment 11, in the first state and the second state, it is also preferable that the voltage difference between the first electrode 131 and the second electrode 132 and the third electrode 231 and the fourth electrode 232 is 8V or more. By adopting such an embodiment, it is possible to more effectively align the liquid crystal molecules 310 horizontally. Although the upper limit of the voltage difference between the first electrode 131 and the second electrode 132 and the third electrode 231 and the fourth electrode 232 is not particularly limited, the voltage difference between the first electrode 131 and the second electrode 132 and the third electrode 231 and the fourth electrode 232 is, for example, 20V or less. It is preferable that the voltage difference between the first electrode 131 and the second electrode 132 and the third electrode 231 and the fourth electrode 232 is 8V or more and 20V or less.

When the voltage difference between the first electrode 131 and the second electrode 132 and the third electrode 231 and the fourth electrode 232 is 8V or more, for example, the difference between the first electrode 131 and the second electrode 132 in the first state It is preferable that the voltage difference is 3V or less. The voltage difference between the third electrode 231 and the fourth electrode 232 in the first state is preferably 2V or less. Although the lower limit of the voltage difference between the first electrode 131 and the second electrode 132 in the first state is not particularly limited, the voltage difference between the first electrode 131 and the second electrode 132 in the first state is, for example, , 1.1V or more. Further, the lower limit of the voltage difference between the third electrode 231 and the fourth electrode 232 in the first state is not particularly limited, but the voltage difference between the third electrode 231 and the fourth electrode 232 in the first state is , for example, 0.01V or more.

The voltage difference between the first electrode 131 and the second electrode 132 in the first state is preferably 1.1V or more and 3V or less. The voltage difference between the third electrode 231 and the fourth electrode 232 in the first state is preferably 0.01V or more and 2V or less.

Furthermore, the voltage difference between the first electrode 131 and the second electrode 132 in the second state is preferably 2V or less. The voltage difference between the third electrode 231 and the fourth electrode 232 in the second state is preferably 3V or less. The lower limit of the voltage difference between the first electrode 131 and the second electrode 132 in the second state is not particularly limited, but the voltage difference between the first electrode 131 and the second electrode 132 in the second state is, for example, 0.01V or more. Furthermore, the lower limit of the voltage difference between the third electrode 231 and the fourth electrode 232 in the second state is not particularly limited, but the voltage difference between the third electrode 231 and the fourth electrode 232 in the second state is, for example, 1.1V or more.

The voltage difference between the first electrode 131 and the second electrode 132 in the second state is preferably 0.01V or more and 2V or less. The voltage difference between the third electrode 231 and the fourth electrode 232 in the second state is preferably 1.1V or more and 3V or less.

By applying a voltage as in this modification, even the liquid crystal molecules 310 near the interface are tilted, so it is possible to realize a sHWP with a wide viewing angle. At this time, the cell thickness, twist pitch, and angle of the retardation film can be changed as appropriate.

(Embodiment 12)
In this embodiment, features unique to this embodiment will be mainly described, and descriptions of contents that overlap with the above-described Embodiments 1 to 11 and their modifications will be omitted. This embodiment is substantially the same as Embodiment 9, except that the configuration of the liquid crystal cell 11 and the preferred voltage applied to the electrodes are different.

FIG. 75 is a schematic cross-sectional view of an optical element according to Embodiment 12. FIG. 76 is a schematic cross-sectional view of a liquid crystal cell included in an optical element according to Embodiment 12. FIG. 77 is a schematic diagram illustrating the orientation of liquid crystal molecules in the first state and the second state of the optical element according to Embodiment 12. Since the alignment of liquid crystal molecules near the interface of the substrate is vertical and the orientation cannot be defined, in FIG. 77, the alignment direction of the liquid crystal molecules is defined by the electrode direction.

In this embodiment, the reference direction (0°) is the orientation direction 311A of the liquid crystal molecules 311 on the first substrate 100 side in the first state projected onto the substrate surface on the output side of the optical element 10. The alignment direction 311A of the liquid crystal molecules 311 on the first substrate 100 side in the first state corresponds to the horizontal right direction of the screen of the liquid crystal cell 11 when the optical element 10 is viewed from the output side.

The liquid crystal cell 11 included in the optical element 10 of this embodiment shown in FIGS. 75 to 77 further includes a first vertical alignment film 414 disposed between the first substrate 100 and the liquid crystal layer 300, and a second vertical alignment film 424 disposed between the second substrate 200 and the second substrate 200 . The liquid crystal layer 300 contains liquid crystal molecules 310 having negative dielectric anisotropy. The electrode 11E includes, on the first substrate 100, a planar first electrode 131 and a second electrode 132 that overlaps the first electrode 131 via the first insulating layer 141 and is provided with a slit portion. In the second substrate 200, a planar third electrode 231 and a fourth electrode 232 which overlaps the third electrode 231 via the second insulating layer 241 and is provided with a slit portion 232S are provided. have In a plan view, the orientation direction 311X of the liquid crystal molecules 311 on the first substrate 100 side in a state where no voltage is applied is the extension direction 132A of the slit portion 132S provided in the second electrode 132 and the slit portion provided in the fourth electrode 232. 232S, and perpendicular to the stretching direction 132A of the slit portion 132S provided in the second electrode 132, and with respect to the stretching direction 232A of the slit portion 232S provided in the fourth electrode 232. It is placed diagonally.

By adopting this configuration, as shown in FIG. 77, when a voltage is applied between the first electrode 131 and the second electrode 132 and no voltage is applied between the third electrode 231 and the fourth electrode 232, circularly polarized light (e.g., right-handed circularly polarized light) that enters the liquid crystal cell 11 becomes a first linearly polarized light after passing through the liquid crystal cell 11. In other words, the first state can be realized.

Also, as shown in FIG. 77, when no voltage is applied between the first electrode 131 and the second electrode 132 and a voltage is applied between the third electrode 231 and the fourth electrode 232, circularly polarized light (e.g., right-handed circularly polarized light) incident on the liquid crystal cell 11 passes through the liquid crystal cell 11 and becomes second linearly polarized light having a polarization direction perpendicular to the polarization direction of the first linearly polarized light in a planar view. In other words, the second state can be realized.

One of the first electrode 131 and the second electrode 132 is a pixel electrode, and the other is a common electrode. One of the third electrode 231 and the fourth electrode 232 is a pixel electrode, and the other is a common electrode. In FIG. 77, both the first substrate 100 and the second substrate 200 are provided with a planar electrode and an electrode with a slit portion in that order toward the liquid crystal layer 300 side, but the arrangement of the planar electrode and the electrode with a slit portion is not limited to this, and an electrode with a slit portion and a planar electrode may be provided in that order toward the liquid crystal layer 300 side.

At least one of the liquid crystal molecules 311 on the first substrate 100 side and the liquid crystal molecules 312 on the second substrate 200 side preferably has a tilt. For example, when the liquid crystal molecules 311 on the first substrate 100 side have a tilt, in this embodiment, the tilt direction of the liquid crystal molecules 311 on the first substrate 100 side and the direction of stretching of the FFS electrode on the first substrate 100 side are determined. are preferably orthogonal, and more preferably the angle between the two is 90°. More specifically, the alignment direction 311X of the liquid crystal molecules 311 on the first substrate 100 side in a state where no voltage is applied is perpendicular to the extending direction 132A of the slit portion 132S provided in the second electrode 132. is preferable, and it is more preferable that the angle between the two is 90°. At this time, the tilt orientation of the liquid crystal molecules 311 on the first substrate 100 side is preferably approximately 0° (for example, -10° or more and +10° or less), and the liquid crystal molecules 312 on the second substrate 200 side should not have a tilt. is preferred. Further, the liquid crystal molecules 312 on the second substrate 200 side may have a tilt, and the liquid crystal molecules 311 on the first substrate 100 side may not have a tilt. Furthermore, both the liquid crystal molecules 311 on the first substrate 100 side and the liquid crystal molecules 312 on the second substrate 200 side may have a tilt.

In plan view, the angle δ between the alignment direction 311X and the stretching direction 232A (where δ is a real number greater than 0° and less than 90°) and the twist angle D1 of the liquid crystal molecules 310 included in the liquid crystal layer 300 are: It is preferable that the above (Formula DX1) is satisfied in the first state and the second state. By adopting such an aspect, polarization modulation and polarization non-modulation can be effectively switched over a wide band.

The twist angle D1 is preferably 60° or more and 80° or less, more preferably 64° or more and 76° or less, and even more preferably 68° or more and 72° or less. By adopting such an embodiment, it is possible to more effectively switch between polarization modulation and polarization non-modulation over a wide bandwidth.

The azimuth angle of the stretching direction 132A is 90°, the orientation direction 311X of the liquid crystal molecules 311 on the first substrate 100 side in the state of no voltage application is 0°, the azimuth angle of the stretching direction 232A is 160°, When the twist angle of 310 is 70° and the liquid crystal layer 300 contains negative liquid crystal molecules 310, no voltage is applied between the first electrode 131 and the second electrode 132, as shown in FIGS. 75 to 77. When a voltage is not applied between the third electrode 231 and the fourth electrode 232 in the applied state, the azimuth angle of the alignment direction 311A of the liquid crystal molecules 311 on the first substrate 100 side is 0°, and the second substrate 200 A first state in which the azimuth angle of the orientation direction 312A of the side liquid crystal molecules 312 is 70° can be realized. Further, when a voltage is applied between the first electrode 131 and the second electrode 132 and a voltage is applied between the third electrode 231 and the fourth electrode 232, the alignment direction 311B of the liquid crystal molecules 311 on the first substrate 100 side It is possible to realize a second state in which the azimuth angle of is 90° and the azimuth angle of the alignment direction 312B of the liquid crystal molecules 312 on the second substrate 200 side is 160°.

The pitch of the second electrode 132 provided with the slit portions 132S is preferably 1 μm or more and 5 μm or less. By reducing the pitch in this way, the orientation of the liquid crystal molecules 310 changes more uniformly, and the modulation characteristics can be improved. Further, the pitch of the fourth electrode 232 provided with the slit portion 232S is preferably 1 μm or more and 5 μm or less. By adopting such an embodiment, the orientation of the liquid crystal molecules 310 can be changed more uniformly, and the modulation characteristics can be improved.

The liquid crystal molecules 310 of this embodiment are negative type liquid crystal molecules 310. With this embodiment, by applying a large vertical voltage between the first substrate 100 and the second substrate 200, the negative liquid crystal molecules 310 can be tilted and horizontally aligned. In the first state and the second state, the voltage difference between the first electrode 131 and the second electrode 132 and the third electrode 231 and the fourth electrode 232 is preferably 1V or more, and preferably 3V or more. More preferably, it is 4V or more. By adopting such an aspect, the liquid crystal molecules 310 can be horizontally aligned more effectively. Although the upper limit of the voltage difference between the first electrode 131 and the second electrode 132 and the third electrode 231 and the fourth electrode 232 is not particularly limited, The voltage difference between the electrode 232 and the electrode 232 is, for example, 7V or less. The voltage difference between the first electrode 131 and the second electrode 132 and the third electrode 231 and the fourth electrode 232 is preferably 1V or more and 7V or less, more preferably 3V or more and 7V or less, More preferably, the voltage is 4V or more and 7V or less.

Furthermore, between the first electrode 131 and the second electrode 132, and between the third electrode 231 and the fourth electrode 232, a weak voltage can be applied between the pixel electrode and the common electrode to control the in-plane orientation direction of the liquid crystal molecules 310. When the liquid crystal molecules 310 are negative type liquid crystal molecules, the liquid crystal molecules 310 are oriented in the extension direction of the slit portions 132S, 232S (direction perpendicular to the electric field) in the plane. In this case, applying a strong transverse electric field interferes with the twisting of the liquid crystal orientation due to chiral force, so it is preferable that the transverse electric field is weak.

When the voltage difference between the first electrode 131 and the second electrode 132 and the third electrode 231 and the fourth electrode 232 is 7V or less, for example, the voltage difference between the first electrode 131 and the second electrode 132 in the first state is preferably 0.6V or less. The voltage difference between the third electrode 231 and the fourth electrode 232 in the first state is preferably 0.6V or less. The lower limit value of the voltage difference between the first electrode 131 and the second electrode 132 in the first state is not particularly limited, but the voltage difference between the first electrode 131 and the second electrode 132 in the first state is, for example, 0.01V or more. In addition, the lower limit value of the voltage difference between the third electrode 231 and the fourth electrode 232 in the first state is not particularly limited, but the voltage difference between the third electrode 231 and the fourth electrode 232 in the first state is, for example, 0.01V or more.

The voltage difference between the first electrode 131 and the second electrode 132 in the first state is preferably 0.01V or more and 0.6V or less. The voltage difference between the third electrode 231 and the fourth electrode 232 in the first state is preferably 0.01V or more and 0.6V or less.

Moreover, it is preferable that the voltage difference between the first electrode 131 and the second electrode 132 in the second state is 2V or less. It is preferable that the voltage difference between the third electrode 231 and the fourth electrode 232 in the second state is 2V or less. Although the lower limit of the voltage difference between the first electrode 131 and the second electrode 132 in the second state is not particularly limited, the voltage difference between the first electrode 131 and the second electrode 132 in the second state is, for example, , 0.7V or more. Further, the lower limit value of the voltage difference between the third electrode 231 and the fourth electrode 232 in the second state is not particularly limited, but the voltage difference between the third electrode 231 and the fourth electrode 232 in the second state is , for example, 0.7V or more.

The voltage difference between the first electrode 131 and the second electrode 132 in the second state is preferably 0.7V or more and 2V or less. The voltage difference between the third electrode 231 and the fourth electrode 232 in the second state is preferably 0.7V or more and 2V or less.

As the first vertical alignment film 414 and the second vertical alignment film 424, those similar to those in Embodiment 5 can be used. In this embodiment, since vertical alignment films are arranged on both substrate sides, it is possible to realize an optical element 10 with higher productivity than when horizontal alignment films are arranged.

(Modification of Embodiment 12)
In the twelfth embodiment, the voltage difference between the first electrode 131 and the second electrode 132 and the third electrode 231 and the fourth electrode 232 in the first state and the second state is preferably 8V or more. By adopting such an aspect, the liquid crystal molecules 310 can be horizontally aligned more effectively. Although the upper limit of the voltage difference between the first electrode 131 and the second electrode 132 and the third electrode 231 and the fourth electrode 232 is not particularly limited, The voltage difference between the electrode 232 and the electrode 232 is, for example, 20V or less. The voltage difference between the first electrode 131 and the second electrode 132 and the third electrode 231 and the fourth electrode 232 is preferably 8V or more and 20V or less.

When the voltage difference between the first electrode 131 and the second electrode 132 and the third electrode 231 and the fourth electrode 232 is 8V or more, for example, the difference between the first electrode 131 and the second electrode 132 in the first state It is preferable that the voltage difference is 2V or less. The voltage difference between the third electrode 231 and the fourth electrode 232 in the first state is preferably 2V or less. Although the lower limit of the voltage difference between the first electrode 131 and the second electrode 132 in the first state is not particularly limited, the voltage difference between the first electrode 131 and the second electrode 132 in the first state is, for example, , 0.01V or more. Further, the lower limit of the voltage difference between the third electrode 231 and the fourth electrode 232 in the first state is not particularly limited, but the voltage difference between the third electrode 231 and the fourth electrode 232 in the first state is , for example, 0.01V or more.

The voltage difference between the first electrode 131 and the second electrode 132 in the first state is preferably 0.01V or more and 2V or less. The voltage difference between the third electrode 231 and the fourth electrode 232 in the first state is preferably 0.01V or more and 2V or less.

Moreover, it is preferable that the voltage difference between the first electrode 131 and the second electrode 132 in the second state is 3V or less. The voltage difference between the third electrode 231 and the fourth electrode 232 in the second state is preferably 3V or less. Although the lower limit of the voltage difference between the first electrode 131 and the second electrode 132 in the second state is not particularly limited, the voltage difference between the first electrode 131 and the second electrode 132 in the second state is, for example, , 1.1V or more. Further, the lower limit value of the voltage difference between the third electrode 231 and the fourth electrode 232 in the second state is not particularly limited, but the voltage difference between the third electrode 231 and the fourth electrode 232 in the second state is , for example, 1.1V or more.

The voltage difference between the first electrode 131 and the second electrode 132 in the second state is preferably 1.1 V or more and 3 V or less. The voltage difference between the third electrode 231 and the fourth electrode 232 in the second state is preferably 1.1 V or more and 3 V or less.

By applying a voltage as in this modification, even the liquid crystal molecules 310 near the interface are tilted, so it is possible to realize a sHWP with a wide viewing angle. At this time, the cell thickness, twist pitch, and angle of the retardation film can be changed as appropriate.

(Embodiment 13)
In this embodiment, features unique to this embodiment will be mainly described, and descriptions of contents that overlap with the above-described Embodiments 1 to 12 and their modifications will be omitted. In this embodiment, a variable focus element including the optical element (sHWP) of the above embodiments 9 to 12 and their modified examples will be described.

Similarly to the seventh embodiment, the optical elements (sHWP) of the ninth to twelfth embodiments and their modifications can also be combined with the PB lens 20 to configure the variable focus element 30.

(Modification of Embodiment 13)
Similar to the first modification of the seventh embodiment, in this modification, the PB lens 20 of the thirteenth embodiment is disposed within the optical element 10, and the variable focus element 30 is in-celled. In this modification, description of contents that overlap with Modification 1 of Embodiment 7 will be omitted.

FIG. 78 is a schematic cross-sectional view of a variable focus element according to a modification of the thirteenth embodiment. FIG. 79 is an enlarged schematic cross-sectional view of a variable focus element according to a modification of the thirteenth embodiment. FIG. 80 is a schematic diagram illustrating the orientation of liquid crystal molecules in the first state and the second state of an optical element according to a modification of the thirteenth embodiment. Since the alignment of liquid crystal molecules near the interface of the substrate is vertical and the orientation cannot be defined, in FIG. 80, the alignment direction of the liquid crystal molecules is defined by the electrode direction.

In this embodiment, the reference direction (0°) is the orientation direction 311A of the liquid crystal molecules 311 on the first substrate 100 side in the first state projected onto the substrate surface on the output side of the optical element 10. The alignment direction 311A of the liquid crystal molecules 311 on the first substrate 100 side in the first state corresponds to the horizontal right direction of the screen of the liquid crystal cell 11 when the optical element 10 is viewed from the output side.

As shown in FIG. 78, the variable focus element 30 of this modification is a multi-stage variable focus element 30B including two or more sets of laminates each consisting of an optical element 10 and a PB lens 20.

The PB lens 20 included in the variable focus element 30 of this modification is arranged within the optical element 10, as shown in FIG. By making the PB lens 20 in-cell in this way, there is no need to attach the PB lens 20 externally, so manufacturing costs can be significantly reduced. Moreover, it becomes possible to suppress the thickness of the variable focus element 30. Note that in FIG. 78, the optical element 10 and the PB lens 20 are shown separately for convenience.

More specifically, the variable focus element 30 of this modified example includes, in order from the entrance side to the exit side, a second quarter-wave film 13, a first quarter-wave film 12, a first substrate 100, a liquid crystal layer 300, a PB lens 20, and a second substrate 200. The variable focus element 30 may include a first vertical alignment film 414 between the first substrate 100 and the liquid crystal layer 300. The variable focus element 30 may also include a second vertical alignment film 424 between the second substrate 200 and the liquid crystal layer 300.

Here, when the first quarter-wave film 12 and the second quarter-wave film 13 are disposed on the emission side of the liquid crystal cell 11 as in the above embodiments 9 to 12 and their modifications, In one state, circularly polarized light (for example, right-handed circularly polarized light) incident on the optical element 10 first enters the liquid crystal cell 11 and is converted into first linearly polarized light, and the first linearly polarized light is converted into first linearly polarized light. The light enters the 1/4 wavelength film 12 and the second 1/4 wavelength film 13 and is converted into circularly polarized light (for example, left circularly polarized light). In the second state, the circularly polarized light (for example, right-handed circularly polarized light) that has entered the optical element 10 first enters the liquid crystal cell 11 and is converted into second linearly polarized light, and the second linearly polarized light is The light enters the first quarter-wavelength film 12 and the second quarter-wavelength film 13 and is converted into circularly polarized light (for example, right-handed circularly polarized light).

On the other hand, when the first 1/4 wavelength film 12 and the second 1/4 wavelength film 13 are arranged on the incident side of the liquid crystal cell 11 as in this modification, in the first state, the optical element 10 The incident circularly polarized light (for example, right-handed circularly polarized light) first enters the first 1/4 wavelength film 12 and the second 1/4 wavelength film 13 and is converted into linearly polarized light. The light enters the cell 11 and is converted into first circularly polarized light (for example, left-handed circularly polarized light). Furthermore, in the second state, the circularly polarized light (for example, right-handed circularly polarized light) that has entered the optical element 10 first enters the first quarter-wavelength film 12 and the second quarter-wavelength film 13, and then enters the first quarter-wavelength film 12 and the second quarter-wavelength film 13 to form a straight line. The linearly polarized light enters the liquid crystal cell 11 and is converted into second circularly polarized light (for example, right-handed circularly polarized light).

In this modification, a case where the optical element of Embodiment 9 is used as the optical element 10 will be described as an example. The azimuth angle of the stretching direction 132A is 90°, the orientation direction 311X of the liquid crystal molecules 311 on the first substrate 100 side in a state where no voltage is applied is 0°, and the twist angle of the liquid crystal molecules 310 is 70°, and When the liquid crystal layer 300 contains negative liquid crystal molecules 310, as shown in FIGS. 78 to 80, a voltage below the threshold is applied between the first electrode 131 and the second electrode 132, and the first When a voltage equal to or higher than the threshold is applied between the electrode 131 and the second electrode 132 and the solid electrode 240, the azimuth angle of the orientation direction 311A of the liquid crystal molecules 311 on the first substrate 100 side is 0°, and the second A first state in which the azimuth angle of the alignment direction 312A of the liquid crystal molecules 312 on the substrate 200 side is 70° can be realized. Further, a voltage equal to or higher than the threshold value was applied between the first electrode 131 and the second electrode 132, and a voltage equal to or higher than the threshold value was applied between the first electrode 131 and the second electrode 132 and the solid electrode 240. In this case, the second state is such that the azimuth angle of the alignment direction 311B of the liquid crystal molecules 311 on the first substrate 100 side is 90°, and the azimuth angle of the alignment direction 312B of the liquid crystal molecules 312 on the second substrate 200 side is 160°. It can be realized.

As shown in FIG. 80, when the azimuth angle of the alignment direction 311A of the liquid crystal molecules 311 on the first substrate 100 side in the first state is 0°, the first 1/4 wavelength film 12 and the second 1/4 wavelength film 12 The azimuth angle of the slow axis of the 1/4 wavelength film on the side closer to the light emission side of the wavelength film 13 (in this modification, the slow axis 12A of the first 1/4 wavelength film 12) is -2°. As mentioned above, it is preferable that the angle is 18° or less. By adopting such an aspect, polarization modulation and polarization non-modulation can be switched over a wider band.

As shown in FIG. 80, when the azimuth angle of the alignment direction 311A of the liquid crystal molecules 311 on the first substrate 100 side in the first state is 0°, it is preferable that the azimuth angle of the slow axis of the quarter-wave film farthest from the light emission side among the first quarter-wave film 12 and the second quarter-wave film 13 (the slow axis 13A of the second quarter-wave film 13 in this modified example) is 38° or more and 58° or less. By adopting such an embodiment, it is possible to switch between polarization modulation and polarization non-modulation over a wider band.

FIG. 81 is a schematic cross-sectional view illustrating a detailed configuration of a variable focus element according to a modification of the thirteenth embodiment. As shown in FIG. 81, the variable focus element 30 includes, in order from the incident side to the exit side, the optical element 10, the first PB lens 20A1, the optical element 10, the first PB lens 20A1, and the optical element 10, second PB lens 20A2, optical element 10, second PB lens 20A2, optical element 10, third PB lens 20A3, optical element 10, third PB lens 20A3 , is equipped with.

The first PB lens 20A1 has a diopter D=±0.25, the second PB lens 20A2 has a diopter D=±0.5, and the third PB lens 20A3 has a diopter D=±1 lens characteristic. has. It has the characteristic of + (condensing) when right-handed circularly polarized light is incident, and - (diverging) when left-handed circularly polarized light is incident.

Table 2 below is a table explaining the states of the optical element 10 and the PB lenses 20A1, 20A2, and 20A3 in each mode of the variable focus element 30 according to a modification of the thirteenth embodiment.

The F0 mode will be explained using Table 2 above. In this mode, all optical elements 10 are in the second state (unmodulated). When the right-handed circularly polarized light is incident, it is not modulated by the first optical element 10 and enters the first first PB lens 20A1 as it is. Here, the light is focused at 0.25D. At this time, the emitted light becomes left-handed circularly polarized light. Here, it is a characteristic of the PB lens 20 that the direction of the circularly polarized light changes even after passing through the PB lens 20. Since the optical element 10 is non-modulated, the light passes through the second optical element 10 as left-handed circularly polarized light. In the first PB lens 20A1 of the two eyes, a divergence of -0.25D occurs. As a result, the incident light passes through the first four lenses from the incident side (optical element 10, first PB lens 20A1, optical element 10 and first PB lens 20A1) as is. Thereafter, the light also passes through the second PB lens 20A2 and the PB lens 20A3 in the same manner, and is emitted as it is as the incident light at 0D.

The F1 mode will be explained using Table 2 above. In this mode, only the fourth optical element 10 from the incident side is in the first state. In this state, after passing through the first second PB lens 20A2, the light is left circularly polarized and 0.5D is imparted, similar to the F0 mode. Subsequently, the optical element in the first state converts the light into right-handed circularly polarized light. Subsequently, the second PB lens 20A2 imparts +0.5D to the light, and outputs it as left-handed circularly polarized light with a total of 1D. Thereafter, the light is emitted as 1D left-handed circularly polarized light. Since the light becomes left-handed circularly polarized light after passing through the second PB lens 20A2, the sign at the third PB lens 20A3 is opposite to that at F0.

The F-2.5 mode will be explained using Table 2 and FIG. 82 above. FIG. 82 is a diagram illustrating the polarization state in the F-2.5 mode of a variable focus element according to a modification of the thirteenth embodiment. As shown in Table 2 and FIG. 82, in the F-2.5 mode, the first four lenses from the incident side (optical element 10, first PB lens 20A1, optical element 10 and first PB lens 20A1) becomes right-handed circularly polarized light with -0.5D added to it, and -2D is added to the last four lenses on the exit side (optical element 10, third PB lens 20A3, optical element 10 and third PB lens 20A3). and is emitted as right-handed circularly polarized light with a total of -2.5D.

In addition, based on the same principle, multiple levels of focal length can be realized depending on which optical element 10 is set to the first modulated state. In this modified example, only three conditions are shown.

In Embodiment 13 and this modified example, a mode including a film-like (in-cell polymer-like) PB lens was described, but as in Modified Example 1 of Embodiment 7, the PB lens itself is formed of a liquid crystal layer. You can.

(Embodiment 14)
In this embodiment, features unique to this embodiment will be mainly explained, and explanations of contents that overlap with the above-mentioned Embodiments 1 to 13 and their modifications will be omitted. In this embodiment, a head mounted display including the variable focus element 30 of the thirteenth embodiment and its modification will be described.

Similar to the eighth embodiment, the head mounted display 1 of this embodiment includes a display panel 1P that displays an image, a retardation plate 40, and a variable focus element 30. By using the head-mounted display 1, the light emitted from the display panel 1P such as a liquid crystal display device or an organic electroluminescent display device becomes circularly polarized light through the retardation plate 40, which passes through the variable focus element 30, visible to user U.

The effects of the present invention will be explained below using examples and comparative examples, but the present invention is not limited to these examples.

(Example 1)
An optical element 10 of Example 1 having a configuration similar to that of Embodiment 1 was manufactured. The optical element 10 of Example 1 includes, in order from the incident side to the output side, a liquid crystal cell 11, a reverse wavelength dispersion 1/4 wavelength film as a first 1/4 wavelength film 12, and a second 1/4 wavelength film 12. A quarter-wavelength film with flat wavelength dispersion as a quarter-wavelength film 13 was provided. The azimuth angle of the slow axis of the quarter-wavelength film with reverse wavelength dispersion (the slow axis 12A of the first quarter-wavelength film 12) is 57.2°, which is the same as that of the quarter-wavelength film with flat wavelength dispersion. The azimuth angle of the slow axis (the slow axis 13A of the second 1/4 wavelength film 13) was 12.2. Specifically, the optical element 10 of Example 1 was manufactured as follows.

A first substrate 100 having a first comb-tooth electrode 120 and a second substrate 200 having a second comb-tooth electrode 220 were prepared. The electrode direction of the first substrate 100 (extension direction 120A of the first comb-tooth electrode 120) and the electrode direction of the second substrate 200 (extension direction 220A of the second comb-tooth electrode 220) were formed so as to have the angle relationship shown in FIG. 5 when bonded together. In addition, a photospacer having a height of 3.6 μm was arranged on the second substrate 200.

Next, a film of PMMA (polymethyl methacrylate) was formed on both the first substrate 100 provided with the first comb-teeth electrode 120 and the second substrate 200 provided with the second comb-teeth electrode 220. Subsequently, a sealing material was drawn on the second substrate 200, and the first substrate 100 and the second substrate 200 were bonded to each other with the liquid crystal material sandwiched therebetween, thereby producing the liquid crystal cell 11.

The liquid crystal material used here was a mixture of positive type liquid crystal molecules with positive dielectric anisotropy (Δn = 0.066), 5 wt % dodecyl acrylate (C12A) and chiral agent S-811. The concentration of the chiral agent was set so that the twist angle between the upper and lower substrates in the liquid crystal cell was 70°.

After heating this liquid crystal cell 11 to an isotropic phase state, the temperature was lowered to room temperature while applying a voltage to the first substrate 100, to obtain a liquid crystal cell 11 with uniform horizontal alignment, comprising a first weakly anchored horizontal alignment film 411 and a second weakly anchored horizontal alignment film 421. Furthermore, a reverse wavelength dispersion quarter-wave film (first quarter-wave film 12) and a flat wavelength dispersion quarter-wave film (second quarter-wave film 13) were attached to the liquid crystal cell 11 obtained above, to obtain the optical element (sHWP element) 10 of Example 1.

FIG. 33 is a graph illustrating the voltage applied to the optical element according to Example 1. As shown in FIG. 33, when a voltage is applied to the second substrate 200 of the optical element 10 of Example 1, a transverse electric field on the second substrate 200 side causes a second The liquid crystal molecules 312 on the substrate 200 side were aligned in the 70° direction. After that, when the voltage on the second substrate 200 is weakened (not zero), the liquid crystal molecules 312 on the second substrate 200 side remain aligned in the 70° direction along the electric field direction, while the liquid crystal molecules 311 on the first substrate 100 side , it slid due to the chiral twisting force added to the liquid crystal material and was oriented in the 0° direction. This was the first state. Note that even after the voltage was turned off, this first state of alignment was maintained.

When a voltage is applied to the first substrate 100 and then weakened in the opposite manner to the above, the liquid crystal molecules 311 on the first substrate 100 side move in the 90° direction (azimuth angle 90 ), and the liquid crystal molecules 312 on the second substrate 200 side were oriented in a 160° direction (azimuth angle of 160°) due to chiral force. This was the second state. In this way, the optical element 10 of Example 1 was able to switch between the second state and the first state by applying voltage to the first substrate 100 or applying voltage to the second substrate 200.

As shown in FIG. 5, the first state and the second state are the same in that the liquid crystal molecules 311 on the first substrate 100 side and the liquid crystal molecules 312 on the second substrate 200 side are twisted by 70°. However, the entire system was rotated by 90 degrees.

In order to consider the design of a suitable liquid crystal cell, optical calculations were performed on the optical element 10 of Example 1 using LCD-MASTER 1D manufactured by Shintech. In the following, based on the results obtained by simulation, a range in which modulation of 90% or more can be achieved in the wavelength range of 450 nm to 630 nm (including when not modulated) is determined to be a preferable range. Further, in the graph shown below, only wavelengths of 450 nm and 630 nm are shown for simplicity.

First, in order to examine a suitable range of retardation Δnd of the liquid crystal layer 300 at a wavelength of 550 nm in a state where no voltage is applied, The wavelength dispersion of the Stokes parameter S3 during modulation and during modulation was determined by simulation. FIG. 34 is a graph showing the Stokes parameter S3 at the time of non-modulation with respect to the retardation of the liquid crystal layer included in the optical element according to Example 1. FIG. 35 is a graph showing the Stokes parameter S3 during modulation with respect to the retardation of the liquid crystal layer included in the optical element according to Example 1.

As shown in FIGS. 34 and 35, it was found that the retardation Δnd of the liquid crystal layer 300 at a wavelength of 550 nm with no voltage applied is preferably 180 nm or more and 280 nm or less.

In order to examine a suitable range of the twist angle of the liquid crystal layer 300, the wavelength dispersion of the Stokes parameter S3 in non-modulation and modulation with respect to the twist angle of the liquid crystal layer 300 included in the optical element 10 of Example 1 was determined by simulation. Ta. FIG. 36 is a graph showing the Stokes parameter S3 at the time of non-modulation with respect to the twist angle of the liquid crystal layer included in the optical element according to Example 1. FIG. 37 is a graph showing the Stokes parameter S3 during modulation with respect to the twist angle of the liquid crystal layer included in the optical element according to Example 1. As shown in FIGS. 36 and 37, it was found that the twist angle of the liquid crystal layer 300 is preferably 57° or more and 82° or less in both the first state and the second state.

In order to consider the preferred range of the azimuth angle of the slow axis of the reverse wavelength dispersion quarter-wave film, the wavelength dispersion of the Stokes parameter S3 in the non-modulated state and in the modulated state was obtained by simulation with respect to the azimuth angle of the slow axis of the reverse wavelength dispersion quarter-wave film provided in the optical element 10 of Example 1. FIG. 38 is a graph showing the Stokes parameter S3 in the non-modulated state with respect to the azimuth angle of the slow axis of the reverse wavelength dispersion quarter-wave film provided in the optical element of Example 1. FIG. 39 is a graph showing the Stokes parameter S3 in the modulated state with respect to the azimuth angle of the slow axis of the reverse wavelength dispersion quarter-wave film provided in the optical element of Example 1. As shown in FIGS. 38 and 39, it was found that the azimuth angle of the slow axis of the reverse wavelength dispersion quarter-wave film as the first quarter-wave film 12 is preferably 48° or more and 66° or less.

In order to examine the preferable range of the retardation of the 1/4 wavelength film with reverse wavelength dispersion, the retardation range of the 1/4 wavelength film with reverse wavelength dispersion included in the optical element 10 of Example 1 was measured for non-modulation and modulation. The wavelength dispersion of the Stokes parameter S3 at the time was determined by simulation. FIG. 40 is a graph showing the Stokes parameter S3 at the time of non-modulation with respect to the phase difference of the quarter-wavelength film with reverse wavelength dispersion included in the optical element according to Example 1. FIG. 41 is a graph showing the Stokes parameter S3 during modulation with respect to the phase difference of the quarter-wavelength film with reverse wavelength dispersion included in the optical element according to Example 1. Figure 40 and. As shown in FIG. 41, it was found that the retardation of the reverse wavelength dispersion 1/4 wavelength film as the first 1/4 wavelength film 12 is preferably 30 nm or more and 230 nm or less.

In order to examine the suitable range of the azimuth angle of the slow axis of the quarter-wavelength film with flat wavelength dispersion, the direction of the slow axis of the quarter-wavelength film with flat wavelength dispersion included in the optical element 10 of Example 1 was determined. The chromatic dispersion of the Stokes parameter S3 in non-modulation and modulation with respect to the angle was determined by simulation. FIG. 42 is a graph showing the Stokes parameter S3 during non-modulation with respect to the azimuth of the slow axis of the flat wavelength dispersion quarter-wave film included in the optical element according to Example 1. FIG. 43 is a graph showing the Stokes parameter S3 during modulation with respect to the azimuth of the slow axis of the quarter-wavelength film with flat wavelength dispersion included in the optical element according to Example 1. As shown in FIGS. 42 and 43, the azimuth angle of the slow axis of the flat wavelength dispersion 1/4 wavelength film as the second 1/4 wavelength film 13 is preferably 3° or more and 22° or less. That's what I found out.

In order to consider the suitable range of the phase difference of the quarter-wave film with flat wavelength dispersion, the wavelength dispersion of the Stokes parameter S3 in the non-modulated and modulated state was obtained by simulation for the phase difference of the quarter-wave film with flat wavelength dispersion provided in the optical element 10 of Example 1. FIG. 44 is a graph showing the Stokes parameter S3 in the non-modulated state for the phase difference of the quarter-wave film with flat wavelength dispersion provided in the optical element of Example 1. FIG. 45 is a graph showing the Stokes parameter S3 in the modulated state for the phase difference of the quarter-wave film with flat wavelength dispersion provided in the optical element of Example 1. As shown in FIGS. 44 and 45, it was found that the phase difference of the quarter-wave film with flat wavelength dispersion as the second quarter-wave film 13 is preferably 110 nm or more and 175 nm or less.

(Comparative Example 1)
46 is a cross-sectional schematic diagram of an optical element according to Comparative Example 1. An optical element 10R1 of Comparative Example 1 shown in FIG. 46 was produced. The optical element 10R1 of Comparative Example 1 was an optical element corresponding to the optical element of Comparative Example 1. The optical element 10R1 of Comparative Example 1 was provided with, in order from the incident side to the exit side, a quarter-wavelength film 14R having a slow axis azimuth angle of 75°, a half-wavelength film 15R having a slow axis azimuth angle of 15°, a liquid crystal cell 11R1 having a TN liquid crystal layer 300R1 twisted by 90°, a half-wavelength film 16R having a slow axis azimuth angle of -75°, and a quarter-wavelength film 17R having a slow axis azimuth angle of -15°.

(Comparative example 2)
FIG. 47 is a schematic cross-sectional view of an optical element according to Comparative Example 2. An optical element 10R2 of Comparative Example 2 shown in FIG. 47 was manufactured. The optical element 10R2 of Comparative Example 2 was an optical element corresponding to the optical element of Comparative Form 2 described above. The optical element 10R2 of Comparative Example 2 had a structure in which a 70° twisted TN liquid crystal layer 300R2 and a -70° twisted TN liquid crystal layer 300R3 were laminated in order from the incident side to the output side.

(Evaluation of Example 1, Comparative Example 1, and Comparative Example 2)
For the optical elements (sHWP) of Example 1, Comparative Example 1, and Comparative Example 2, when right-handed circularly polarized light (S3=+1) is incident, the wavelength dispersion of the Stokes parameter S3 of the emitted light is shown in FIGS. 48 and 49. Shown below. FIG. 48 is a graph showing the wavelength dispersion of the Stokes parameter S3 during modulation of the optical elements according to Example 1, Comparative Example 1, and Comparative Example 2. FIG. 49 is a graph showing the chromatic dispersion of the Stokes parameter S3 of the optical elements according to Example 1, Comparative Example 1, and Comparative Example 2 at the time of non-modulation.

As shown in Figure 48, during modulation in Example 1 (in the first state), it was found that the emitted light was close to S3 = -1 over a wide wavelength range. In other words, it was possible to modulate from S3 = +1 to S3 = -1 (in other words, from right-handed circular polarization to left-handed circular polarization).

Further, as shown in FIG. 49, it was found that when non-modulated (in the second state) in Example 1, the emitted light was close to S3=+1 over a wide wavelength band. That is, it was possible to emit S3=+1 with S3=+1 (in other words, right-handed circularly polarized light remains right-handed circularly polarized light) in an unmodulated state.

On the other hand, in the case of Comparative Example 1 (TN1 layer), it was found that although it had extremely excellent characteristics when not modulated, there was a large wavelength dependence when modulated, and only a very narrow range was appropriately modulated. In addition, in the case of Comparative Example 2 (TN 2 layers), it was found that although the broadband modulation was improved compared to Comparative Example 1, it deteriorated when not modulated.

(Example 2)
An optical element 10 of Example 2 having a configuration similar to that of Embodiment 2 was manufactured. Specifically, the optical element 10 of Example 2 was produced in the same manner as Example 1 except that the configuration of the liquid crystal cell 11 was different. Specifically, the optical element 10 of Example 2 was manufactured as follows.

A substrate to which transverse electric fields can be applied in two different directions was prepared as the first substrate 100. More specifically, a first substrate 100 including a first comb-teeth electrode 121 and a second comb-teeth electrode 122 was prepared. The extending direction 121A of the first comb-teeth electrode 121 was arranged to be perpendicular to the extending direction 122A of the second comb-teeth electrode 122. Photo spacers with a height of 7.6 μm were arranged on the first substrate 100.

A PHMA (polyhexyl methacrylate) film was formed on the first substrate 100 to form a weakly anchored horizontal alignment film 412. A vertical alignment film 422 was formed on the second substrate 200. Subsequently, a sealing material was drawn on the second substrate 200, and the first substrate 100 and the second substrate 200 were bonded to each other with the liquid crystal material sandwiched therebetween, thereby producing the liquid crystal cell 11.

Here, as the liquid crystal material, a mixture of a positive liquid crystal with positive dielectric anisotropy (Δn=0.066) and a chiral agent S-811 was used. The concentration of the chiral agent was set so that the twist angle between the upper and lower substrates in the liquid crystal cell was 106°.

After heating this liquid crystal cell 11 to an isotropic phase state, the temperature was lowered to room temperature while applying a voltage in the direction of the first electric field of the first substrate 100, thereby obtaining a liquid crystal cell 11 with uniform horizontal alignment. Furthermore, a 1/4 wavelength film with reverse wavelength dispersion as the first 1/4 wavelength film 12 and a 1/4 wavelength film with flat wavelength dispersion as the second 1/4 wavelength film 13 are added to the liquid crystal cell 11 obtained above. /4 wavelength film was attached so that the axial direction was as shown in FIG. 13, to obtain the optical element (sHWP element) 10 of Example 2. A first state (modulated state) was obtained when a voltage was applied in the direction of the first electric field, and a second state (non-modulated state) was obtained when a voltage was applied in the direction of the second electric field.

(Evaluation of Example 1, Example 2 and Comparative Example 1)
For the optical elements (sHWP) of Example 1, Example 2, and Comparative Example 1, when right-handed circularly polarized light (S3=+1) is incident, the wavelength dispersion of the Stokes parameter S3 of the emitted light is shown in FIGS. 50 and 51. Shown below. FIG. 50 is a graph showing the wavelength dispersion of the Stokes parameter S3 during modulation of the optical elements according to Example 1, Example 2, and Comparative Example 1. FIG. 51 is a graph showing the chromatic dispersion of the Stokes parameter S3 of the optical elements according to Example 1, Example 2, and Comparative Example 1 at the time of non-modulation.

As shown in Figure 50, during modulation in Example 2 (first state), it can be seen that the emitted light is close to S3 = -1 over a wide wavelength range, similar to Example 1. In other words, it was possible to modulate from S3 = +1 to S3 = -1 (in other words, from right-handed circular polarization to left-handed circular polarization).

Furthermore, as shown in FIG. 51, it can be seen that when the second embodiment is not modulated (in the second state), the emitted light is close to S3=+1 over a wide wavelength band, similarly to the first embodiment. That is, it was possible to emit S3=+1 with S3=+1 (in other words, right-handed circularly polarized light remains right-handed circularly polarized light) in an unmodulated state.

(Example 3)
An optical element 10 of Example 3 corresponding to Embodiment 3 described above was manufactured. Specifically, a first substrate 100 including a first comb-teeth electrode 121 and a second comb-teeth electrode 122, a second substrate 200 including a third comb-teeth electrode 221 and a fourth comb-teeth electrode 222; The optical element 10 of Example 3 was produced in the same manner as Example 1 except for using .

During modulation (in the first state), the optical element of Example 3 modulates from S3=+1 to S3=-1 (in other words, from right-handed circularly polarized light to left-handed circularly polarized light), as in Example 1. I was able to do that. When not modulated (in the second state), as in Example 1, it is possible to emit S3=+1 with S3=+1 (in other words, the right-handed circularly polarized light remains as the right-handed circularly polarized light) while remaining in the unmodulated state. did it.

In the optical element 10 of Example 3, two states could be created by applying an on-voltage to both the first substrate 100 and the second substrate 200 and then lowering the voltage. In Example 3, since the orientation of both the first substrate 100 and the second substrate 200 could be defined by voltage, the response speed could be increased.

(Example 4-1 and Example 4-2)
Optical elements 10 of Examples 4-1 and 4-2 corresponding to the above-mentioned Embodiment 4 were manufactured. Specifically, a first alignment film 410 provided between the first substrate 100 and the liquid crystal layer 300, and a second alignment film 420 provided between the second substrate 200 and the liquid crystal layer 300. The optical elements 10 of Examples 4-1 and 4-2 were produced in the same manner as in Example 1 except that the configuration was different. FIG. 52 is a diagram illustrating the alignment direction of the bistable alignment film included in the optical element according to Example 4-1. FIG. 53 is a diagram illustrating the alignment direction of the bistable alignment film included in the optical element according to Example 4-2. The optical element 10 of Examples 4-1 and 4-2 includes a weakly anchored horizontal alignment film (also referred to as a slippery film) 423 as a second alignment film 420 on the second substrate 200 side, and A bistable alignment film 413 was provided as a first alignment film 410 on one substrate 100 side.

A PEG film was used as the weak anchoring horizontal alignment film (slippery film) 423 provided in the optical element 10 of Example 4-1 and Example 4-2. The PEG film was formed by the following procedure. 5 wt% methoxypolyethylene glycol monoacrylate, 5 wt% polyethylene glycol diacrylate, Irgacure 2959 (0.1 wt%), and cyclopentanone (89.9 wt%) were mixed. This was applied onto the second substrate 200, irradiated with 2 J/ ^cm2 ultraviolet light of 254 nm, and then baked at 130°C for 90 minutes. As a result, a weak anchoring horizontal alignment film 423 was obtained.

The bistable alignment film 413 provided in the optical element 10 of Example 4-1 was formed by photoalignment. Specifically, as shown in FIG. 52, the bistable alignment film 413 was formed using a material in which two polymers (a first photoaligned polymer and a second photoaligned polymer) with different photofunctional wavelengths were mixed. After applying a solution in which two polymers with different photofunctional wavelengths were mixed onto a substrate, the substrate was irradiated with polarized ultraviolet light of a specific wavelength, and then irradiated with polarized ultraviolet light of a different wavelength and direction, thereby forming a bistable alignment film 413 having stable alignment directions in two directions, a first direction 413A in which the alignment is regulated by the first photoaligned polymer, and a second direction 413B in which the alignment is regulated by the second photoaligned polymer.

For the bistable alignment film 413 included in the optical element 10 of Example 4-2, a textured substrate and a rubbing treatment were used. Specifically, as shown in FIG. 53, a structure having grooves in a specific direction (first direction 413A) is formed using polymer on the first substrate 100, and a structure having grooves in a direction different from the groove direction (second direction 413A) is formed in the first substrate 100. A rubbing process was performed in the direction 413B). The liquid crystal molecules 310 had two forces, one for aligning in the groove direction and the other for aligning in the rubbing direction, and it was possible to form a bistable alignment film 413 having stable alignment directions in two directions.

The optical elements of Examples 4-1 and 4-2 change from S3=+1 to S3=-1 (in other words, from right-handed circularly polarized light to left-handed circularly polarized light), as in Example 1, during modulation (in the first state). (to circularly polarized light). When not modulated (in the second state), as in Example 1, it is possible to emit S3=+1 with S3=+1 (in other words, the right-handed circularly polarized light remains as the right-handed circularly polarized light) while remaining in the unmodulated state. did it.

(Example 5)
An optical element 10 of Example 5 corresponding to the above-mentioned Embodiment 5 was manufactured. Specifically, the optical element 10 of Example 5 was produced in the same manner as Example 1 except that the configuration of the liquid crystal cell 11 was different. The liquid crystal cell 11 included in the optical element 10 of Example 5 includes a first substrate 100 having a first electrode 131 and a second electrode 132, a first vertical alignment film 414, and a liquid crystal layer 300 containing liquid crystal molecules 310. , a second vertical alignment film 424, and a second substrate 200 having a third electrode 231 and a fourth electrode 232, in this order. As shown in FIG. 19, the azimuth angle in the extending direction 132A of the slit portion 132S provided in the second electrode 132 is 0°, and the azimuth angle in the extending direction 232A of the slit portion 232S provided in the fourth electrode 232 is 0°. It was 160°.

Figure 54 is a graph explaining the applied voltage in the first state of the optical element according to Example 5. As shown in Figure 54, in the optical element 10 of Example 5, the first state was realized by applying +/-1V to the common electrode of the first electrode 131 and the second electrode 132 on the first substrate 100 side, -/+1V to the pixel electrode, and +/-5V to both the third electrode 231 and the fourth electrode 232 on the second substrate 200 side. Also, in the optical element 10 of Example 5, the second state was realized by applying +/-1V to the common electrode of the third electrode 231 and the fourth electrode 232 on the second substrate 200 side, -/+1V to the pixel electrode, and +/-5V to both the first electrode 131 and the second electrode 132 on the first substrate 100 side.

FIG. 55 is a graph showing the wavelength dispersion of the Stokes parameter S3 during modulation of the optical elements according to Example 1, Example 2, Example 5, Comparative Example 1, and Comparative Example 2. FIG. 56 is a graph showing the chromatic dispersion of the Stokes parameter S3 of the optical elements according to Example 1, Example 2, Example 5, Comparative Example 1, and Comparative Example 2 at the time of non-modulation. FIGS. 55 and 56 show the wavelength dispersion of the Stokes parameter S3 of the emitted light when right-handed circularly polarized light (S3=+1) is incident on the optical element 10 of Example 5.

In Example 5, |S3|>0.9 was also obtained over the wavelength range of 450 nm to 650 nm, and good characteristics were obtained. That is, as shown in FIG. 55, during modulation (first state) in Example 5, it was found that the emitted light was close to S3=-1 over a wide wavelength range. That is, it was possible to modulate from S3=+1 to S3=-1 (in other words, from right-handed circularly polarized light to left-handed circularly polarized light). Also, as shown in FIG. 56, during non-modulation (second state) in Example 5, it was found that the emitted light was close to S3=+1 over a wide wavelength range. That is, it was possible to output S3=+1 as S3=+1 (in other words, right-handed circularly polarized light as right-handed circularly polarized light) in an unmodulated state.

In this embodiment, as in the other embodiments, the modulation characteristics and non-modulation characteristics can be tuned as appropriate by designing the Δnd and twist angle of the liquid crystal layer.

(Example 6)
An optical element 10 of Example 6 having a configuration similar to that of Embodiment 6 was manufactured. Specifically, the optical element 10 of Example 6 includes, in order from the incident side to the output side, a liquid crystal cell 11, a reverse wavelength dispersion 1/4 wavelength film as a first 1/4 wavelength film 12, and a reverse wavelength dispersion film 12. It was equipped with The azimuth angle of the slow axis of the quarter-wavelength film with reverse wavelength dispersion (the slow axis 12A of the first quarter-wavelength film 12) is 12.2°, and the direction in which the first comb-teeth electrode 120 extends The azimuth angle of 120A was 0°, and the azimuth angle of the extending direction 220A of the second comb-teeth electrode 220 was 220°. Specifically, the optical element 10 of Example 6 was manufactured as follows.

A first substrate 100 having a first comb-tooth electrode 120 and a second substrate 200 having a second comb-tooth electrode 220 were prepared. The electrode direction of the first substrate 100 (extension direction 120A of the first comb-tooth electrode 120) and the electrode direction of the second substrate 200 (extension direction 220A of the second comb-tooth electrode 220) were formed so as to have the angle relationship shown in FIG. 23 when bonded together. In addition, a spacer having a height of 3.4 μm was arranged on the second substrate 200.

Next, a film of PMMA (polymethyl methacrylate) was formed on both the first substrate 100 and the second substrate 200. Subsequently, a sealing material was drawn on the second substrate 200, and the first substrate 100 and the second substrate 200 were bonded to each other with the liquid crystal material sandwiched therebetween, thereby producing the liquid crystal cell 11.

Here, the liquid crystal material is a mixture of positive liquid crystal molecules with positive dielectric anisotropy (Δn=0.066), 5 wt% of dodecyl acrylate (C12A), and chiral agent S-811. Using. Note that the concentration of the chiral agent was set so that the twist angle between the upper and lower substrates in the liquid crystal cell was 64°.

After heating this liquid crystal cell 11 to an isotropic phase state, the temperature was lowered to room temperature while applying a voltage to the first substrate 100, to obtain a liquid crystal cell 11 with uniform horizontal alignment, comprising a first weakly anchored horizontal alignment film 411 and a second weakly anchored horizontal alignment film 421. Furthermore, a reverse wavelength dispersion quarter-wave film (first quarter-wave film 12) was attached to the liquid crystal cell 11 obtained above, to obtain the optical element (sHWP element) 10 of Example 6.

FIG. 57 is a graph showing the wavelength dispersion of the Stokes parameter S3 during modulation of the optical elements according to Example 1, Example 2, Example 5, Example 6, Comparative Example 1, and Comparative Example 2. FIG. 58 is a graph showing the wavelength dispersion of the Stokes parameter S3 of the optical elements according to Example 1, Example 2, Example 5, Example 6, Comparative Example 1, and Comparative Example 2 at the time of non-modulation. FIGS. 57 and 58 show the wavelength dispersion of the Stokes parameter S3 of the emitted light when right-handed circularly polarized light (S3=+1) is incident on the optical element 10 of Example 6.

In Example 6 as well, |S3|>0.9 was obtained over the wavelength range of 450 nm to 650 nm, and good characteristics were obtained. That is, as shown in FIG. 57, it was found that during modulation in Example 5 (in the first state), the emitted light was close to S3=-1 over a wide wavelength band. That is, it was possible to modulate from S3=+1 to S3=-1 (in other words, from right-handed circularly polarized light to left-handed circularly polarized light). Furthermore, as shown in FIG. 58, it was found that when non-modulated (in the second state) in Example 5, the emitted light was close to S3=+1 over a wide wavelength band. That is, it was possible to emit S3=+1 with S3=+1 (in other words, right-handed circularly polarized light remains right-handed circularly polarized light) in an unmodulated state.

In this embodiment, as in the other embodiments, the modulation characteristics and non-modulation characteristics can be tuned as appropriate by designing the Δnd and twist angle of the liquid crystal layer.

(Example 7)
FIG. 59 is a diagram showing the axial orientation of the optical element included in the variable focus element according to Example 7. A variable focus element 30 of Example 7 corresponding to Modification 1 of Embodiment 7 was manufactured. The variable focus element 30 of Example 7 includes, in order from the incident side to the output side, a flat wavelength dispersion 1/4 wavelength film as the second 1/4 wavelength film 13 and a first 1/4 wavelength film. 12, the first substrate 100, the first alignment film 410, the liquid crystal layer 300, the second alignment film 420, the PB lens 20, and the second substrate 200. It was equipped with the following. A first substrate 100, a first alignment film 410 (specifically, a first weak anchoring horizontal alignment film 411), a liquid crystal layer 300, a second alignment film 420 (specifically, a first weak anchoring horizontal alignment film 411), which constitute a liquid crystal cell 11. The second weakly anchored horizontal alignment film 421) and the second substrate 200 had the same configuration as in Example 1.

As shown in FIG. 59, the azimuth angle of the slow axis of the quarter-wavelength film with reverse wavelength dispersion (the slow axis 12A of the first quarter-wavelength film 12) is 12.2°, and the flat wavelength dispersion The azimuth angle of the slow axis of the quarter-wavelength film (the slow axis 13A of the second quarter-wavelength film 13) was 57.2°. Further, the azimuth angle of the alignment direction 311A of the liquid crystal molecules 311 on the first substrate 100 side in the first state is 0°, and the azimuth angle of the alignment direction 311B of the liquid crystal molecules 311 on the first substrate 100 side in the second state is 90°. It was °. The azimuth angle of the alignment direction 312A of the liquid crystal molecules 312 on the second substrate 200 side in the first state is 70°, and the azimuth angle of the alignment direction 312B of the liquid crystal molecules 312 on the second substrate 200 side in the second state is 160°. there were.

Specifically, the variable focus element 30 of Example 7 was manufactured as follows. A photosensitive material for forming an in-cell PB lens containing a polymer represented by the above general formula (PB-1) was applied to the second substrate 200 to form a film for forming a PB lens.

FIG. 60 is a schematic diagram illustrating the first alignment process in the manufacturing process of the variable focus element according to Example 7. FIG. 61 is a schematic diagram illustrating the second alignment process in the manufacturing process of the variable focus element according to Example 7. FIG. 62 is a schematic diagram illustrating the third alignment process in the manufacturing process of the variable focus element according to Example 7. FIG. 63 is a schematic diagram illustrating the fourth alignment process in the manufacturing process of the variable focus element according to Example 7.

Next, the PB lens forming film provided on the second substrate 200 was subjected to alignment treatment. Specifically, as shown in FIG. 60, the PB lens forming film 600 was subjected to alignment treatment with polarized light having an azimuth angle of 0° using a first photomask 510. Subsequently, as shown in FIG. 61, using a second photomask 520, the PB lens forming film 600 was subjected to alignment treatment with polarized light having an azimuth angle of 45°. Subsequently, as shown in FIG. 62, using a third photomask 530, the PB lens forming film 600 was subjected to alignment treatment with polarized light having an azimuth angle of 90°. Finally, as shown in FIG. 63, using a fourth photomask 540, the PB lens forming film 600 was subjected to alignment treatment with polarized light having an azimuth angle of 135°. Thereafter, an annealing process was performed, and the PB lens 20 could be formed on the second substrate 200.

A liquid crystal cell 11 was produced in the same manner as in Example 1 using the laminate of the second substrate 200 and the PB lens 20. After obtaining the horizontally aligned liquid crystal cell 11, a 1/4 wavelength film with reverse wavelength dispersion is attached as the first 1/4 wavelength film 12, and a 1/4 wavelength film with flat wavelength dispersion is attached as the second 1/4 wavelength film 13. A 4-wavelength film was attached to obtain the variable focus element 30 of Example 7.

Here, in this embodiment, the incident light enters the second 1/4 wavelength film 13, the first 1/4 wavelength film 12, and the liquid crystal layer 300 before the PB lens 20, and becomes right-handed circularly polarized light and left-handed circularly polarized light. In order to switch the circularly polarized light and condense or diverge the light with the PB lens 20 depending on the polarization state, the second 1/4 wavelength film 13 and the first 1/4 wavelength film 12 have a higher incidence than the liquid crystal layer 300. placed on the side. Therefore, the arrangement and axis orientation of the second quarter wavelength film 13 and the first quarter wavelength film 12 were different from those in Example 1.

The variable focus element 30 of Example 7 was able to switch between polarization modulation and non-polarization modulation over a wide band, and could be made thinner.

(Example 8)
An optical element 10 of Example 8 having a configuration similar to that of Embodiment 9 was manufactured. Specifically, the configuration of the liquid crystal cell 11, the azimuth of the slow axis of the quarter-wavelength film with reverse wavelength dispersion (the slow axis 12A of the first quarter-wavelength film 12), and the azimuth angle of the slow axis of the quarter-wavelength film with reverse wavelength dispersion (the slow axis 12A of the first quarter-wavelength film 12), and the azimuth angle of the slow axis of the quarter-wavelength film with reverse wavelength dispersion (the slow axis 12A of the first quarter-wavelength film 12) The optical element 10 of Example 8 was produced in the same manner as Example 5, except that the azimuth of the slow axis of the 1/4 wavelength film (the slow axis 13A of the second 1/4 wavelength film 13) was different. did.

As shown in FIG. 66, the liquid crystal cell 11 included in the optical element 10 of Example 8 includes a first substrate 100 (FFS substrate) having a first electrode 131 and a second electrode 132, and a weakly anchored first vertical An alignment film 414, a liquid crystal layer 300 containing liquid crystal molecules 310, a second vertical alignment film 424, and a second substrate 200 having a solid electrode 240 were provided in this order. The liquid crystal layer 300 included negative liquid crystal molecules 310 containing a chiral agent, and had a refractive index anisotropy Δn of 0.104. The chiral pitch of the liquid crystal layer 300 was 11 μm, and the thickness (cell thickness) d of the liquid crystal layer 300 was 2.75 μm.

The azimuth angle of the extending direction 132A of the slit portion 132S provided in the second electrode 132 is 90°, and the azimuth angle of the alignment direction 311X of the liquid crystal molecules 311 on the first substrate 100 side in a state where no voltage is applied is 0°. Ta. The azimuth angle of the slow axis of the quarter-wavelength film with reverse wavelength dispersion (the slow axis 12A of the first quarter-wavelength film 12) is 68.7°, and the azimuth angle of the quarter-wavelength film with flat wavelength dispersion is 68.7°. The azimuth angle of the slow axis (the slow axis 13A of the second 1/4 wavelength film 13) was 23.7°. The flat wavelength dispersion quarter-wave film (second quarter-wave film 13) was a positive A plate.

FIG. 83 is a graph explaining the applied voltage in the first state of the optical element according to Example 8. FIG. 84 is a graph explaining the applied voltage in the second state of the optical element according to Example 8. As shown in FIG. 83, in the optical element 10 of Example 8, the first state can be realized by applying +/-5V to the solid electrode 240 on the second substrate 200 side, 0V to the common electrode of the first electrode 131 and the second electrode 132 on the first substrate 100 side, and +/-0.4V to the pixel electrode. Also, as shown in FIG. 84, in the optical element 10 of Example 8, the second state can be realized by applying +/-5V to the solid electrode 240 on the second substrate 200 side, 0V to the common electrode of the first electrode 131 and the second electrode 132 on the first substrate 100 side, and +/-1V to the pixel electrode.

In this example, by applying a large vertical electric field, the negative liquid crystal molecules 310 are tilted and horizontally aligned, and between the first electrode 131 and the second electrode 132 (common electrode of the FFS substrate - pixel electrode). A weak voltage was applied to determine the in-plane orientation direction of the liquid crystal molecules 310. Since the liquid crystal molecules 310 contained in the liquid crystal layer 300 are negative-type liquid crystal molecules 310, the liquid crystal molecules 310 were aligned in the slit stretching direction (direction perpendicular to the electric field direction) in the plane. At this time, if a strong transverse electric field is applied, it will interfere with the alignment twist of the liquid crystal molecules 310 due to chiral force, so it is important that the transverse voltage be a weak voltage. Since a vertical alignment film is used, the vicinity of the substrate is vertically aligned, but horizontal alignment with approximately 70 degree twist can be achieved within the bulk of the liquid crystal layer 300. The twist angle here indicates a rotation angle within which the tilt angle of the liquid crystal molecules 310 is within 45 degrees.

(Comparative example 3)
FIG. 85 is a schematic cross-sectional view of an optical element according to Comparative Example 3. An optical element 10R1 of Comparative Example 3 shown in FIG. 85 was produced.

(Comparative example 4)
FIG. 86 is a schematic cross-sectional view of an optical element according to Comparative Example 4. An optical element 10R1 of Comparative Example 4 shown in FIG. 86 was produced.

Figure 87 is a graph showing the wavelength dispersion of the Stokes parameter S3 during modulation for the optical elements according to Example 8, Comparative Example 3, and Comparative Example 4. Figure 88 is a graph showing the wavelength dispersion of the Stokes parameter S3 during non-modulation for the optical elements according to Example 8, Comparative Example 3, and Comparative Example 4. Figures 87 and 88 show the wavelength dispersion of the Stokes parameter S3 of the emitted light when right-handed circularly polarized light (S3 = +1) is incident on the optical elements according to Example 8, Comparative Example 3, and Comparative Example 4.

As shown in Figure 87, during modulation (first state) in Example 8, it can be seen that the emitted light is close to S3 = -1 over a wide wavelength range. That is, it was possible to modulate from S3 = +1 to S3 = -1 (in other words, from right-handed circularly polarized light to left-handed circularly polarized light). Also, as shown in Figure 88, during non-modulation (second state), it can be seen that the emitted light is close to S3 = +1 over a wide wavelength range. That is, it was possible to output S3 = +1 as S3 = +1 (in other words, right-handed circularly polarized light as right-handed circularly polarized light) in an unmodulated state.

On the other hand, in the case of Comparative Example 3 (one TN liquid crystal layer), although it has extremely excellent characteristics when not modulated, there is a large wavelength dependence when modulated, indicating that only a very narrow range is properly modulated. Do you get it. In the case of Comparative Example 4 (two TN liquid crystal layers), it was found that although the broadband modulation was improved compared to Comparative Example 1, it deteriorated when no modulation was performed.

(Example 9)
An optical element 10 of Example 9 having a configuration similar to that of Embodiment 10 was manufactured. Specifically, the optical element 10 of Example 9 was produced in the same manner as Example 8 except that the configuration of the liquid crystal cell 11 was different.

As shown in FIG. 71, the liquid crystal cell 11 included in the optical element 10 of Example 9 includes a first substrate 100 (FFS substrate) having a first electrode 131 and a second electrode 132, and a first vertical alignment film 414. , a liquid crystal layer 300 containing liquid crystal molecules 310, a second vertical alignment film 424, and a second substrate 200 (FFS substrate) having a third electrode 231 and a fourth electrode 232, in this order. The liquid crystal layer 300 included negative liquid crystal molecules 310 containing a chiral agent, and had a refractive index anisotropy Δn of 0.104. The chiral pitch of the liquid crystal layer 300 was 11 μm, and the thickness (cell thickness) d of the liquid crystal layer 300 was 3 μm.

The azimuth angle of the stretching direction 132A of the slit portion 132S provided in the second electrode 132 was 0°, the azimuth angle of the alignment direction 311X of the liquid crystal molecules 311 on the first substrate 100 side in the voltage-unapplied state was 0°, the azimuth angle of the stretching direction 232A of the slit portion 232S provided in the fourth electrode 232 was 160°, and the azimuth angle of the alignment direction 312A of the liquid crystal molecules 312 on the second substrate 200 side in the voltage-unapplied state was 160°. The azimuth angle of the slow axis of the reverse wavelength dispersion quarter-wave film (slow axis 12A of the first quarter-wave film 12) was 68.7°, and the azimuth angle of the slow axis of the flat wavelength dispersion quarter-wave film (slow axis 13A of the second quarter-wave film 13) was 23.7°. The flat wavelength dispersion quarter-wave film (second quarter-wave film 13) was a positive A plate. In addition, the azimuth angle of the alignment direction 311A of the liquid crystal molecules 311 on the first substrate 100 side in the first state was 0°, and the azimuth angle of the alignment direction 311B of the liquid crystal molecules 311 on the first substrate 100 side in the second state was 90°. The azimuth angle of the alignment direction 312A of the liquid crystal molecules 312 on the second substrate 200 side in the first state was 70°, and the azimuth angle of the alignment direction 312B of the liquid crystal molecules 312 on the second substrate 200 side in the second state was 160°.

FIG. 89 is a graph illustrating the applied voltage in the first state of the optical element according to Example 9. FIG. 90 is a graph illustrating the applied voltage in the second state of the optical element according to Example 9. As shown in FIG. 89, in the optical element 10 of Example 9, +/-5.4V is applied to the common electrode among the third electrode 231 and the fourth electrode 232 on the second substrate 200 side, and +/-5.4V is applied to the pixel electrode. The first state could be achieved by applying 5V, 0V to the common electrode of the first electrode 131 and second electrode 132 on the first substrate 100 side, and +/-1V to the pixel electrode. . Further, as shown in FIG. 90, in the optical element 10 of Example 9, 0V is applied to the common electrode among the third electrode 231 and the fourth electrode 232 on the second substrate 200 side, and +/-1V is applied to the pixel electrode. However, the second state can be realized by applying +/-5.4V to the common electrode of the first electrode 131 and second electrode 132 on the first substrate 100 side and +/-5V to the pixel electrode. did it.

FIG. 91 is a graph showing the wavelength dispersion of the Stokes parameter S3 during modulation of the optical elements according to Example 8, Example 9, and Comparative Example 3. FIG. 92 is a graph showing the chromatic dispersion of the Stokes parameter S3 of the optical elements according to Example 8, Example 9, and Comparative Example 3 at the time of non-modulation. 91 and 92 show the wavelength dispersion of the Stokes parameter S3 of the emitted light when right-handed circularly polarized light (S3=+1) is incident on the optical elements of Example 8, Example 9, and Comparative Example 3.

As shown in FIG. 91, it can be seen that in Example 9 as well as in Example 8, during modulation (first state), the emitted light is close to S3=-1 over a wide wavelength band. That is, it was possible to modulate from S3=+1 to S3=-1 (in other words, from right-handed circularly polarized light to left-handed circularly polarized light). Further, as shown in FIG. 92, it can be seen that in Example 9 as well as in Example 8, when non-modulated (second state), the emitted light is close to S3=+1 over a wide wavelength band. That is, it was possible to emit S3=+1 with S3=+1 (in other words, right-handed circularly polarized light remains right-handed circularly polarized light) in an unmodulated state.

Further, since Example 9 used strong anchoring vertical alignment films on both sides, it was superior to Example 8 in response speed, reliability, and mass productivity. However, since a slightly larger voltage was required for driving, the optical characteristics were slightly inferior compared to Example 8. However, when compared with Comparative Example 3, it was found that it had excellent characteristics during modulation.

(Example 10)
An optical element 10 of Example 9 having a configuration similar to that of Embodiment 11 was manufactured. Specifically, except for the configuration of the liquid crystal cell 11 and the difference in the slow axis 12A of the first 1/4 wavelength film 12 and the slow axis 13A of the second 1/4 wavelength film 13, The optical element 10 of Example 10 was produced in the same manner as in Example 8.

As shown in FIG. 74, the liquid crystal cell 11 included in the optical element 10 of Example 10 includes a first substrate 100 (FFS substrate) having a first electrode 131 and a second electrode 132, and a first vertical alignment film 414. , a liquid crystal layer 300 containing liquid crystal molecules 310, a second vertical alignment film 424, and a second substrate 200 (FFS substrate) having a third electrode 231 and a fourth electrode 232, in this order. The liquid crystal layer 300 included negative liquid crystal molecules 310 containing a chiral agent, and had a refractive index anisotropy Δn of 0.104. The chiral pitch of the liquid crystal layer 300 was 11 μm, and the thickness (cell thickness) d of the liquid crystal layer 300 was 3 μm.

The azimuth angle of the stretching direction 132A of the slit portion 132S provided in the second electrode 132 was 45°, the azimuth angle of the alignment direction 311X of the liquid crystal molecules 311 on the first substrate 100 side in the absence of applied voltage was -45°, and the azimuth angle of the stretching direction 232A of the slit portion 232S provided in the fourth electrode 232 was -65°. The azimuth angle of the slow axis of the reverse wavelength dispersion quarter-wave film (slow axis 12A of the first quarter-wave film 12) was 68.7°, and the azimuth angle of the slow axis of the flat wavelength dispersion quarter-wave film (slow axis 13A of the second quarter-wave film 13) was 23.7°. The flat wavelength dispersion quarter-wave film (second quarter-wave film 13) was a positive A plate.

FIG. 93 is a graph for explaining the applied voltage in the first state of the optical element according to Example 10. FIG. 94 is a graph for explaining the applied voltage in the second state of the optical element according to Example 10. As shown in FIG. 93, in the optical element 10 of Example 10, the first state was realized by applying +/-5.4V to the common electrode of the third electrode 231 and the fourth electrode 232 on the second substrate 200 side and +/-5V to the pixel electrode, and applying 0V to the common electrode of the first electrode 131 and the second electrode 132 on the first substrate 100 side and +/-1V to the pixel electrode. Also, as shown in FIG. 94, in the optical element 10 of Example 10, the second state was realized by applying 0V to the common electrode of the third electrode 231 and the fourth electrode 232 on the second substrate 200 side and +/-1V to the pixel electrode, and applying +/-5.4V to the common electrode of the first electrode 131 and the second electrode 132 on the first substrate 100 side and +/-5V to the pixel electrode.

FIG. 95 is a graph showing the wavelength dispersion of the Stokes parameter S3 during modulation of the optical elements according to Examples 8 to 10 and Comparative Example 3. FIG. 96 is a graph showing the chromatic dispersion of the Stokes parameter S3 of the optical elements according to Examples 8 to 10 and Comparative Example 3 in the non-modulated state. FIG. 95 and FIG. 96.

As shown in FIG. 95, it can be seen that in Example 10 as well as in Examples 8 and 9, during modulation (first state), the emitted light is close to S3=-1 over a wide wavelength band. . That is, it was possible to modulate from S3=+1 to S3=-1 (in other words, from right-handed circularly polarized light to left-handed circularly polarized light). Further, as shown in FIG. 96, in the same way as in Examples 8 and 9, in Example 10 as well, in the non-modulated state (second state), the emitted light is close to S3=+1 over a wide wavelength band. I understand. That is, it was possible to emit S3=+1 with S3=+1 (in other words, right-handed circularly polarized light remains right-handed circularly polarized light) in an unmodulated state. That is, as in Examples 8 and 9, in Example 10 as well, |S3|≧0.9 could be achieved in the wavelength range of 450 nm to 650 nm.

(Example 11)
An optical element 10 of Example 9 having a configuration similar to that of Embodiment 12 was manufactured. Specifically, the optical element 10 of Example 11 was produced in the same manner as Example 8 except that the configuration of the liquid crystal cell 11 was different.

As shown in FIG. 77, the liquid crystal cell 11 included in the optical element 10 of Example 11 includes a first substrate 100 (FFS substrate) having a first electrode 131 and a second electrode 132, and a first vertical alignment film 414. , a liquid crystal layer 300 containing liquid crystal molecules 310, a second vertical alignment film 424, and a second substrate 200 (FFS substrate) having a third electrode 231 and a fourth electrode 232, in this order. The liquid crystal layer 300 included negative liquid crystal molecules 310 containing a chiral agent, and had a refractive index anisotropy Δn of 0.104. The chiral pitch of the liquid crystal layer 300 was 11 μm, and the thickness (cell thickness) d of the liquid crystal layer 300 was 3 μm.

The azimuth angle of the extending direction 132A of the slit portion 132S provided in the second electrode 132 is 90°, and the azimuth angle of the alignment direction 311X of the liquid crystal molecules 311 on the first substrate 100 side in a state where no voltage is applied is 0°. The azimuth angle of the extending direction 232A of the slit portion 232S provided in the fourth electrode 232 was 160°. The azimuth angle of the slow axis of the quarter-wavelength film with reverse wavelength dispersion (the slow axis 12A of the first quarter-wavelength film 12) is 68.7°, and the azimuth angle of the quarter-wavelength film with flat wavelength dispersion is 68.7°. The azimuth angle of the slow axis (the slow axis 13A of the second 1/4 wavelength film 13) was 23.7°. The flat wavelength dispersion quarter-wave film (second quarter-wave film 13) was a positive A plate.

FIG. 97 is a graph illustrating the applied voltage in the first state of the optical element according to Example 11. FIG. 98 is a graph illustrating the applied voltage in the second state of the optical element according to Example 11. As shown in FIG. 97, in the optical element 10 of Example 11, +/-5.4V is applied to the common electrode of the third electrode 231 and the fourth electrode 232 on the second substrate 200 side, and +/-5.4V is applied to the pixel electrode. The first state can be achieved by applying 5V, applying 0V to the common electrode among the first electrode 131 and second electrode 132 on the first substrate 100 side, and applying +/-0.4V to the pixel electrode. did it. Further, as shown in FIG. 98, in the optical element 10 of Example 11, +/-6V is applied to the common electrode among the third electrode 231 and the fourth electrode 232 on the second substrate 200 side, and +/-6V is applied to the pixel electrode. The second state could be achieved by applying 5V, applying 0V to the common electrode of the first electrode 131 and second electrode 132 on the first substrate 100 side, and applying +/-1V to the pixel electrode. .

The liquid crystal cell 11 of this example had the same configuration as the liquid crystal cell of Example 10, but was different from Example 10 in the way the voltage was applied. In this example as well, the same performance as in Example 10 was obtained. Specifically, as in Example 10, in Example 11 as well, during modulation (first state), the emitted light was close to S3=-1 over a wide wavelength band. That is, it was possible to modulate from S3=+1 to S3=-1 (in other words, from right-handed circularly polarized light to left-handed circularly polarized light). Further, similarly to Example 10, in Example 11 as well, in the non-modulated state (second state), the emitted light was close to S3=+1 over a wide wavelength band. That is, it was possible to emit S3=+1 with S3=+1 (in other words, right-handed circularly polarized light remains right-handed circularly polarized light) in an unmodulated state.

(Example 12)
A higher voltage than that in Example 9 was applied to the optical element 10 having the same configuration as the optical element 10 of Example 9 above. Specifically, a voltage corresponding to Modification 1 of Embodiment 10 was applied.

Figure 99 is a graph explaining the applied voltage in the first state of the optical element of Example 12. Figure 100 is a graph explaining the applied voltage in the second state of the optical element of Example 12. As shown in Figure 99, in the optical element 10 of Example 12, the first state was realized by applying +/-11V to the common electrode of the third electrode 231 and the fourth electrode 232 on the second substrate 200 side and +/-10V to the pixel electrode, and applying 0V to the common electrode of the first electrode 131 and the second electrode 132 on the first substrate 100 side and +/-1.1V to the pixel electrode. Also, as shown in FIG. 100, in the optical element 10 of Example 12, the second state was realized by applying 0V to the common electrode of the third electrode 231 and the fourth electrode 232 on the second substrate 200 side, and +/-1.1V to the pixel electrode, and applying +/-11V to the common electrode of the first electrode 131 and the second electrode 132 on the first substrate 100 side, and +/-10V to the pixel electrode.

The liquid crystal cell 11 of this example had the same configuration as the liquid crystal cell of Example 9, but was different from Example 9 in the way the voltage was applied. In this example as well, performance similar to that in Example 9 was obtained. Specifically, as in Example 9, in Example 12 as well, during modulation (first state), the emitted light was close to S3=-1 over a wide wavelength band. That is, it was possible to modulate from S3=+1 to S3=-1 (in other words, from right-handed circularly polarized light to left-handed circularly polarized light). Further, in Example 12 as well as in Example 9, in the non-modulated state (second state), the emitted light was close to S3=+1 over a wide wavelength band. That is, it was possible to emit S3=+1 with S3=+1 (in other words, right-handed circularly polarized light remains right-handed circularly polarized light) in an unmodulated state.

(Evaluation of viewing angle characteristics of Example 9, Example 12, and Comparative Example 3)
The viewing angle characteristics of the optical elements of Example 9, Example 12, and Comparative Example 3 were evaluated by simulation. The results are shown in FIGS. 101 to 106. FIG. 101 is a diagram showing simulation results of the viewing angle characteristics of the optical element of Comparative Example 3 when no modulation is performed. FIG. 102 is a diagram showing simulation results of viewing angle characteristics during modulation of the optical element of Comparative Example 3. FIG. 103 is a diagram showing the simulation results of the viewing angle characteristics of the optical element of Example 9 in the non-modulated state. FIG. 104 is a diagram showing simulation results of viewing angle characteristics during modulation of the optical element of Example 9. FIG. 105 is a diagram showing the simulation results of the viewing angle characteristics of the optical element of Example 12 in the non-modulated state. FIG. 106 is a diagram showing simulation results of viewing angle characteristics during modulation of the optical element of Example 12.

In the graphs for non-modulation in FIGS. 101 to 106, the wider the dark region is, the better the characteristics are, and in the graph for modulation, the wider the thin region is, the better the characteristic is. As shown in FIGS. 101 to 106, it was found that in Examples 9 and 12, the viewing angles were good for both non-modulation and modulation in the wavelength range of 450 nm to 650 nm. Furthermore, it was found that Example 12 had a wider viewing angle than Example 9 in both non-modulated and modulated wavelength ranges in the wavelength range of 450 nm to 650 nm.

(Example 13)
The optical element 10 of Example 13 having the same configuration as Example 12 except that the flat wavelength dispersion 1/4 wavelength film (second 1/4 wavelength film 13) was changed to a negative A plate was carried out. A voltage was applied in the same manner as in Example 12.

(Evaluation of viewing angle characteristics of Example 12 and Example 13)
The viewing angle characteristics of the optical elements of Examples 12 and 13 were evaluated by simulation. The results are shown in FIGS. 105 to 108. FIG. 107 is a diagram showing the simulation results of the viewing angle characteristics of the optical element of Example 13 in the non-modulated state. FIG. 108 is a diagram showing simulation results of viewing angle characteristics during modulation of the optical element of Example 13.

In the graphs for non-modulation in FIGS. 105 to 108, the wider the dark region is, the better the characteristics are, and in the graph for modulation, the wider the thin region is, the better the characteristic is. As shown in FIGS. 105 to 108, it was found that in Examples 12 and 13, the viewing angles were good in both non-modulated and modulated wavelengths in the wavelength range of 450 nm to 650 nm. Furthermore, in comparison with Example 12, Example 13 had better characteristics when not modulated.

(Example 14)
A variable-focus element 30 of Example 14 corresponding to a modified example of the above-mentioned embodiment 13 was produced. The variable-focus element 30 of Example 14 was provided with, in order from the incident side to the exit side, a flat-wavelength dispersion quarter-wavelength film as the second quarter-wavelength film 13, a reverse-wavelength dispersion quarter-wavelength film as the first quarter-wavelength film 12, a first substrate 100, a weakly anchored first vertical alignment film 414, a liquid crystal layer 300, a second vertical alignment film 424, a PB lens 20, and a second substrate 200. The first substrate 100, the weakly anchored first vertical alignment film 414, the liquid crystal layer 300, the second vertical alignment film 424, and the second substrate 200 constituting the liquid crystal cell 11 had the same configuration as in Example 8, except for the axial orientation. The PB lens 20 was in-celled in the same manner as in Example 7.

As shown in FIG. 80, the azimuth angle of the extending direction 132A of the slit portion 132S provided in the second electrode 132 is 90°, and the orientation direction 311X of the liquid crystal molecules 311 on the first substrate 100 side when no voltage is applied is 90°. The azimuth angle was 0°. The azimuth angle of the slow axis of the 1/4 wavelength film with reverse wavelength dispersion (the slow axis 12A of the first 1/4 wavelength film 12) is 8.1°, and the azimuth angle of the 1/4 wavelength film with flat wavelength dispersion is 8.1°. The azimuth angle of the slow axis (the slow axis 13A of the second 1/4 wavelength film 13) was 53.1°. Further, the azimuth angle of the alignment direction 311A of the liquid crystal molecules 311 on the first substrate 100 side in the first state is 0°, and the azimuth angle of the alignment direction 311B of the liquid crystal molecules 311 on the first substrate 100 side in the second state is 90°. It was °. The azimuth angle of the alignment direction 312A of the liquid crystal molecules 312 on the second substrate 200 side in the first state is 70°, and the azimuth angle of the alignment direction 312B of the liquid crystal molecules 312 on the second substrate 200 side in the second state is 160°. there were.

The variable focus element 30 of Example 14 was able to switch between polarization modulation and non-polarization modulation over a wide band, and could be made thinner.

1: Head mounted display 1P: Display panel 10, 10R1, 10R2: Optical element 11, 11R1: Liquid crystal cell 11E: Electrode 12, 13, 14R, 17R: 1/4 wavelength film 12A, 13A: Slow axis 15R, 16R: 1/2 wavelength film 20, 20A1, 20A2, 20A3: Pancharatnamberry (PB) lens 30, 30A, 30B: variable focus element 40: retardation plate 100: first substrate 110, 210: support substrate 120, 121, 122, 220: Comb tooth electrodes 120A, 121A, 122A, 132A, 220A, 221A, 222A, 232A: Stretching direction 120E1, 120E2: Electric field direction 131: First electrode 132: Second electrode 231: Third electrode 232: Fourth Electrode 240: solid electrodes 132S, 232S: slit parts 140, 141, 241: insulating layer 200: second substrate 300: liquid crystal layer 300R1, 300R2, 300R3: TN liquid crystal layer 310, 311, 312, 320: liquid crystal molecule 311A, 311 B, 311 X, 312 A, 312 B, 312 424: Vertical alignment film 510, 520, 530, 540: Photomask 600: PB lens forming film LC0, LC1, LC2: Left circularly polarized light R0, R1, R2: Region

Claims (28)

A liquid crystal cell including a first substrate, a liquid crystal layer, and a second substrate;
A 1/4 wavelength film,
The liquid crystal layer contains liquid crystal molecules twistedly aligned between the first substrate and the second substrate,
The liquid crystal cell has an electrode on at least one of the first substrate and the second substrate for applying a voltage to the liquid crystal layer,
The electrode has a first state in which the liquid crystal molecules on the first substrate side are aligned in a first alignment direction, and a state in which the liquid crystal molecules on the first substrate side are arranged in the first alignment direction in a plan view. The liquid crystal layer is arranged to be switchable between a second state in which the liquid crystal layer is aligned in a second orthogonal alignment direction, and
The switching between the first state and the second state is to control the polarization state of light incident on the liquid crystal cell, and when circularly polarized light is incident on the liquid crystal cell, in the first state, the polarization state of the light incident on the liquid crystal cell is controlled. Polarized light is converted to first linearly polarized light, and in the second state, the circularly polarized light is converted to second linearly polarized light having a polarization direction perpendicular to the polarization direction of the first linearly polarized light in plan view. is,
When linearly polarized light is incident on the liquid crystal cell, in the first state, the linearly polarized light is converted into first circularly polarized light, and in the second state, the linearly polarized light is converted into a rotation direction of the first circularly polarized light. An optical element that converts the light into second circularly polarized light that rotates in the opposite direction. The liquid crystal cell further includes a first weakly anchoring horizontal alignment film disposed between the first substrate and the liquid crystal layer, and a first weakly anchoring horizontal alignment film disposed between the liquid crystal layer and the second substrate. , a second weakly anchored horizontal alignment film;
The electrode has a first comb-teeth electrode in which a comb-teeth-shaped pixel electrode and a common electrode are provided so that their comb-teeth fit into each other on the first substrate; , the comb-shaped pixel electrode and the common electrode have a second comb-shaped electrode provided so that the comb-shaped pixel electrodes and the common electrode fit into each other;
2. The optical element according to claim 1, wherein the extending direction of the first comb-teeth electrode is provided obliquely to the extending direction of the second comb-teeth electrode in plan view. The liquid crystal cell further includes a weakly anchored horizontal alignment film disposed between the first substrate and the liquid crystal layer, and a vertical alignment film disposed between the liquid crystal layer and the second substrate;
the electrodes include a first comb-tooth electrode provided on the first substrate such that the comb teeth of a comb-tooth-shaped pixel electrode and a common electrode are fitted together, and a second comb-tooth electrode superimposed on the first comb-tooth electrode via an insulating layer and provided such that the comb teeth of a comb-tooth-shaped pixel electrode and a common electrode are fitted together,
2 . The optical element according to claim 1 , wherein, in a plan view, the extending direction of the first comb electrode is perpendicular to the extending direction of the second comb electrode. The electrode includes, on the first substrate, a first comb-shaped electrode in which a comb-shaped pixel electrode and a common electrode are provided such that their comb-shaped teeth fit into each other, and a first insulating layer. a second comb-teeth electrode overlapping the first comb-teeth electrode through which the comb-teeth-shaped pixel electrode and the common electrode are provided so that their comb-teeth fit into each other; In the second substrate, the comb-shaped pixel electrode and the common electrode are connected to the third comb-shaped electrode through a second insulating layer, and a third comb-shaped electrode provided so that the comb-shaped pixel electrode and the common electrode fit into each other. a fourth comb-teeth electrode that overlaps the third comb-teeth electrode and is provided such that the comb-teeth-shaped pixel electrode and the common electrode fit into each other;
In plan view,
The extending direction of the first comb-teeth electrode is orthogonal to the extending direction of the second comb-teeth electrode,
The extending direction of the third comb-teeth electrode is perpendicular to the extending direction of the fourth comb-teeth electrode,
2. The optical element according to claim 1, wherein the extending direction of the first comb-teeth electrode is provided obliquely to the extending direction of the third comb-teeth electrode. The liquid crystal cell further includes a bistable alignment film having stable alignment directions in two directions, disposed between the first substrate and the liquid crystal layer,
The electrode has a first comb-teeth electrode in which a comb-teeth-shaped pixel electrode and a common electrode are provided so that their comb-teeth fit into each other on the first substrate; , the comb-shaped pixel electrode and the common electrode have a second comb-shaped electrode provided so that the comb-shaped pixel electrodes and the common electrode fit into each other;
2. The optical element according to claim 1, wherein the extending direction of the first comb-teeth electrode is provided obliquely to the extending direction of the second comb-teeth electrode in plan view. The liquid crystal cell further includes a first vertical alignment film disposed between the first substrate and the liquid crystal layer, and a second vertical alignment film disposed between the liquid crystal layer and the second substrate. a vertical alignment film;
The electrode includes, on the first substrate, a planar first electrode, and a second electrode that overlaps the first electrode via a first insulating layer and is provided with a slit portion, The second substrate includes a planar third electrode, and a fourth electrode that overlaps the third electrode via a second insulating layer and is provided with a slit portion,
2. In a plan view, the extending direction of the slit section provided on the second electrode is arranged obliquely with respect to the extending direction of the slit section provided on the fourth electrode. The optical element described in . 7. The optical element according to claim 1, wherein the liquid crystal layer has a refractive index anisotropy Δn of 0.12 or less. The quarter wavelength film is a first quarter wavelength film,
7. The optical element according to claim 1, further comprising a second quarter-wavelength film on the opposite side of the first quarter-wavelength film from the liquid crystal cell. 9. The optical element according to claim 8, wherein the first quarter-wavelength film has reverse wavelength dispersion characteristics. 9. The in-plane retardation of the first quarter-wavelength film at a wavelength of 450 nm relative to the in-plane retardation at a wavelength of 550 nm is 0.7 times or more and 1 time or less. optical element. 9. The first quarter-wavelength film has an in-plane retardation at a wavelength of 650 nm that is 1 time or more and 1.3 times or less relative to an in-plane retardation at a wavelength of 550 nm. optical element. 9. The optical element according to claim 8, wherein the first quarter-wavelength film has an in-plane retardation of 30 nm or more and 230 nm or less at a wavelength of 550 nm. 9. The optical element according to claim 8, wherein the second quarter-wavelength film has flat wavelength dispersion characteristics. 9. The optical element according to claim 8, wherein the second quarter-wavelength film has an in-plane retardation of 110 nm or more and 175 nm or less at a wavelength of 550 nm. A variable focus element comprising an optical element according to any one of claims 1 to 6 and a Pancharatnam Berry lens. 16. The variable focus element of claim 15, wherein the Pancharatnam Berry lens is disposed within the optical element. A head mounted display comprising the variable focus element according to claim 15. The liquid crystal cell further includes a first vertical alignment film disposed between the first substrate and the liquid crystal layer, and a second vertical alignment film disposed between the liquid crystal layer and the second substrate. having a membrane;
The liquid crystal layer contains liquid crystal molecules having negative dielectric anisotropy,
2. The optical element according to claim 1, wherein at least one of the first vertical alignment film and the second vertical alignment film controls the tilt direction of the liquid crystal molecules in a state where no voltage is applied. The electrode includes, on at least one of the first substrate and the second substrate, a planar electrode and an electrode that overlaps the planar electrode via an insulating layer and is provided with a slit portion. The optical element according to claim 18, characterized in that: 20. The optical element according to claim 19 , wherein the pitch of the electrodes provided with the slit portions is 1 μm or more and 5 μm or less. The optical element according to claim 18 or 19, characterized in that at least one of the first vertical alignment film and the second vertical alignment film is a weak anchoring vertical alignment film. The optical element according to claim 18 or 19, characterized in that the retardation Δnd of the liquid crystal layer when a voltage is applied at a wavelength of 550 nm is 180 nm or more and 280 nm or less. 20. The optical element according to claim 18, wherein the liquid crystal layer has a refractive index anisotropy Δn of 0.12 or less. The optical element according to claim 18 or 19, wherein the light incident on the optical element is circularly polarized light. A variable focus element comprising the optical element according to claim 18 or 19 and a Pancharatnam Berry lens. 26. The variable focus element of claim 25, wherein the Pancharatnam Berry lens is disposed within the optical element. A head mounted display comprising the variable focus element according to claim 25. The optical element according to claim 1, wherein a dual-frequency driven liquid crystal is used as the liquid crystal molecule.

Images