JP7360528B2 - Optical elements, variable focus elements and head-mounted displays - 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, a variable focus optical system that combines a Pancharatnam Berry (PB) lens and an optical element such as a switchable half wave plate (sHWP) has been proposed for use in head-mounted displays. ing. sHWP is a device that can switch the polarization state of left and right circularly polarized light, and is realized by 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.

Patent Document 5 proposes an optical element having a layered liquid crystal structure that rotates the polarization of incident circularly polarized light over a wide range of wavelengths and angles of incidence for use in head-mounted displays.

Special Publication No. 2021-501361 US Patent No. 10379419 Special Publication No. 2009-524106 Special table 2014-528597 publication US Patent No. 10678057

Patent Documents 1 to 5 described above achieve a device structure that can switch 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 over a wide band and wide viewing angle. The problem is that it is difficult to

The present invention has been made in view of the above-mentioned current situation, and includes an optical element capable of switching between polarization modulation and non-polarization modulation over a wide band and wide viewing angle, a variable focus element including the above optical element, and a variable focus element including the above variable focus element. The purpose is to provide a head-mounted display.

(1) One embodiment of the present invention includes a first substrate, a first liquid crystal layer containing a first liquid crystal molecule, a second substrate, a third substrate, and a second liquid crystal molecule. a second liquid crystal layer and a fourth substrate, the first substrate, the first liquid crystal layer, and the second substrate constitute a first liquid crystal cell; The third substrate, the second liquid crystal layer, and the fourth substrate constitute a second liquid crystal cell, and the first liquid crystal cell includes at least one of the first substrate and the second substrate. One side has a first electrode for applying a voltage to the first liquid crystal layer, and the second liquid crystal cell has the second electrode on at least one of the third substrate and the fourth substrate. a second electrode for applying a voltage to the liquid crystal layer; The liquid crystal molecules are arranged so as to be switchable between a first state in which they are vertically aligned and a second state in which the first liquid crystal molecules are twistedly aligned and the second liquid crystal molecules are vertically aligned, and the liquid crystal molecules in the first state are The azimuth angle of the alignment direction of the second liquid crystal molecules on the third substrate side and the azimuth angle of the alignment direction of the second liquid crystal molecules on the fourth substrate side in the first state are respectively The azimuthal angle of the alignment direction of the first liquid crystal molecules on the first substrate side in the two states and the azimuth angle of the alignment direction of the first liquid crystal molecules on the second substrate side in the second state are the same direction. An optical element whose angle is 1/4 rotation.

(2) Further, in an embodiment of the present invention, in addition to the configuration of (1) above, an optical element further includes a negative C plate between the first liquid crystal cell and the second liquid crystal cell. .

(3) Further, in an embodiment of the present invention, in addition to the configuration of (2) above, the retardation Rth in the thickness direction of the negative C plate is −220 nm or more and 0 nm or less.

(4) Further, in an embodiment of the present invention, in addition to the configuration of (1), (2), or (3) above, retardation of the first liquid crystal layer in the second state at a wavelength of 550 nm is provided. is 200 nm or more and 260 nm or less, and the retardation of the second liquid crystal layer in the first state at a wavelength of 550 nm is 210 nm or more and 260 nm or less.

(5) Furthermore, in an embodiment of the present invention, in addition to the configuration of (1), (2), (3), or (4) above, the first liquid crystal cell has the second liquid crystal cell. An optical element that does not have the same configuration as a cell.

(6) In addition to the configurations of (1), (2), (3), (4), or (5), an embodiment of the present invention provides the first configuration in the second state. The liquid crystal molecules of the above are twistedly oriented with a twist angle of 61° or more and 75° or less, and the second liquid crystal molecules in the first state are twistedly oriented with a twist angle of 64° or more and 74° or less.

(7) In addition to the configurations of (1), (2), (3), (4), (5), or (6), an embodiment of the present invention also provides the second configuration. The azimuth angle of the alignment direction of the first liquid crystal molecules on the first substrate side in the state is −9° or more and 7° or less, and the azimuth angle of the alignment direction of the first liquid crystal molecules on the first substrate side in the first state An optical element in which the azimuth angle of the alignment direction of liquid crystal molecules is 85° or more and 96° 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 optical system further comprises a quarter-wavelength film on a side of the first liquid crystal cell opposite to the second liquid crystal cell, or on a side of the second liquid crystal cell opposite to the first liquid crystal cell. element.

(9) Further, an embodiment of the present invention is an optical element in which, in addition to the configuration described in (8) above, the 1/4 wavelength film has reverse wavelength dispersion characteristics.

(10) In addition to the configuration of (8) or (9) above, an embodiment of the present invention provides an in-plane retardation at a wavelength of 450 nm relative to an in-plane retardation at a wavelength of 550 nm of the 1/4 wavelength film. is an optical element that is 0.7 times or more and 1 times or less.

(11) Further, in an embodiment of the present invention, in addition to the configuration of (8), (9), or (10) above, the quarter wavelength film has a wavelength of 650 nm with respect to an in-plane retardation at a wavelength of 550 nm. An optical element having an in-plane retardation of 1 times or more and 1.3 times or less.

(12) In addition to the configuration of (8), (9), (10), or (11), an embodiment of the present invention provides an azimuth angle of the slow axis of the 1/4 wavelength film. is an optical element whose angle is 52° or more and 60° or less.

(13) In addition to the above (8), (9), (10), (11), or (12), an embodiment of the present invention provides a wavelength of the 1/4 wavelength film. An optical element having an in-plane retardation of 90 nm or more and 170 nm or less at 550 nm.

(14) In addition to the configurations of (8), (9), (10), (11), (12), or (13) above, an embodiment of the present invention has the following features: The 4-wavelength film is a first quarter-wavelength film, and further includes a second quarter-wavelength film on the opposite side of the first quarter-wavelength film from the first liquid crystal cell and the second liquid crystal cell. /An optical element comprising a 4-wavelength film.

(15) Further, an embodiment of the present invention is an optical element in which, in addition to the configuration described in (14) above, the second 1/4 wavelength film has flat wavelength dispersion characteristics.

(16) Further, in an embodiment of the present invention, in addition to the configuration described in (14) or (15) above, the azimuth angle of the slow axis of the second 1/4 wavelength film is 8° or more, 18 An optical element that is less than or equal to

(17) Further, in an embodiment of the present invention, in addition to the configuration of (14), (15), or (16) above, the in-plane retardation at a wavelength of 550 nm of the second 1/4 wavelength film is , 120 nm or more and 150 nm or less.

(18) 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), (9) above, (10) above, (11) above, (12) above, (13) above, (14) above, (15) above, (16) above, or (17) above. and a Pancharatnam Berry lens.

(19) In addition to the configuration of (18) above, an embodiment of the present invention is a variable focus element, wherein the Pancharatnam Berry lens is disposed within the optical element.

(20) Another embodiment of the present invention is a head mounted display comprising the variable focus element described in (18) or (19) above.

According to the present invention, it is possible to provide an optical element capable of switching between polarization modulation and non-polarization modulation over a wide band and wide viewing angle, a variable focus element including the optical element, and a head mounted display including the variable focus element. can.

1 is a schematic cross-sectional view of an optical element according to Embodiment 1. FIG. 2 is a schematic cross-sectional view of a first liquid crystal cell and a second 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. 3 is a schematic cross-sectional view of an optical element according to Comparative Form 1. FIG. FIG. 3 is a schematic cross-sectional view of an optical element according to Comparative Form 2. 3 is a graph showing the relationship between the Stokes parameter S3 during modulation and the wavelength of emitted light for optical elements according to Embodiment 1, Comparative Form 1, and Comparative Form 2. FIG. 2 is a schematic cross-sectional view illustrating a first state of the optical element according to Embodiment 1. FIG. 3 is a schematic cross-sectional view illustrating a second state of the optical element according to Embodiment 1. 3 is a schematic cross-sectional view of an optical element according to Modification 1 of Embodiment 1. FIG. 3 is a schematic cross-sectional view of an optical element according to Embodiment 2. FIG. 3 is a schematic cross-sectional view of an optical element according to Embodiment 3. FIG. FIG. 7 is a schematic cross-sectional view of a first liquid crystal cell and a second liquid crystal cell included in the optical element according to Embodiment 3. 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 3. FIG. 7 is a schematic cross-sectional view illustrating a first state of the optical element according to Embodiment 3. FIG. 7 is a schematic cross-sectional view illustrating a second state of the optical element according to Embodiment 3. FIG. 4 is a schematic cross-sectional view of an optical element according to Embodiment 4. FIG. 7 is a schematic cross-sectional view of a first liquid crystal cell and a second liquid crystal cell included in the optical element according to Embodiment 4. 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 4. FIG. 7 is a schematic cross-sectional view illustrating a first state of an optical element according to a fourth embodiment. FIG. 7 is a schematic cross-sectional view illustrating a second state of the optical element according to Embodiment 4. FIG. 7 is a schematic cross-sectional view of a variable focus element according to Embodiment 5. 12 is an example of a schematic cross-sectional view of a PB lens included in a variable focus element according to Embodiment 5. FIG. FIG. 7 is a schematic cross-sectional view of a variable focus element according to Modification 1 of Embodiment 5. FIG. 7 is an enlarged schematic cross-sectional view of a variable focus element according to Modification 1 of Embodiment 5; 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 Modification 1 of Embodiment 5. FIG. 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 5; FIG. 7 is a schematic cross-sectional view illustrating a detailed configuration of a variable focus element according to Modification 1 of Embodiment 5. 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 5. FIG. 7 is a schematic cross-sectional view of a head-mounted display according to a sixth embodiment. FIG. 7 is a schematic perspective view showing an example of the appearance of a head-mounted display according to a sixth embodiment. 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. 3 is a graph showing the relationship between the Stokes parameter S3 and the wavelength of emitted light when the optical elements according to Example 1, Comparative Example 1, and Comparative Example 2 are not modulated. 2 is a graph showing the relationship between the Stokes parameter S3 during modulation and the wavelength of emitted light for optical elements according to Example 1, Comparative Example 1, and Comparative Example 2. 7 is a graph showing the relationship between the Stokes parameter S3 and the azimuth when the optical element according to Comparative Example 1 is not modulated when the incident angle is set to 30°. 7 is a graph showing the relationship between the Stokes parameter S3 and the azimuth during modulation of the optical element according to Comparative Example 1 when the incident angle is set to 30°. 7 is a graph showing the relationship between the Stokes parameter S3 and the azimuth when the optical element according to Comparative Example 2 is not modulated when the incident angle is set to 30°. 7 is a graph showing the relationship between Stokes parameter S3 and azimuth during modulation of the optical element according to Comparative Example 2 when the incident angle is set to 30°. FIG. 3 is a graph showing the relationship between the Stokes parameter S3 and the azimuth when the optical element according to Example 1 is not modulated when the incident angle is set to 30 degrees. FIG. 7 is a graph showing the relationship between the Stokes parameter S3 and the azimuth during modulation of the optical element according to Example 1 when the incident angle is set to 30°. FIG. 3 is a diagram showing simulation results of viewing angle characteristics of the optical elements of Example 1, Comparative Example 1, and Comparative Example 2 during non-modulation and modulation. 7 is a graph showing the Stokes parameter S3 at the time of non-modulation with respect to the retardation in the first state of the second liquid crystal layer included in the optical element of Example 1. FIG. 3 is a graph showing the Stokes parameter S3 at the time of modulation with respect to the retardation in the second state of the first liquid crystal layer included in the optical element of Example 1. FIG. 3 is a graph showing the Stokes parameter S3 at the time of non-modulation with respect to the twist angle of the second liquid crystal molecule included in the optical element of Example 1. FIG. 3 is a graph showing the Stokes parameter S3 during modulation with respect to the twist angle of the first liquid crystal molecule included in the optical element of Example 1. FIG. 7 is a graph showing the Stokes parameter S3 at the time of non-modulation with respect to the pre-twist angle of the second liquid crystal molecule included in the optical element of Example 1. FIG. 3 is a graph showing the Stokes parameter S3 during modulation with respect to the pretwist angle of the first liquid crystal molecule included in the optical element of 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 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 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. 3 is a graph showing the Stokes parameter S3 during 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. FIG. 3 is a diagram showing simulation results of viewing angle characteristics of optical elements of Example 1, Example 2, and Comparative Example 1 during non-modulation and modulation. 7 is a graph showing the relationship between the Stokes parameter S3 and the azimuth when the optical element according to Example 2 is not modulated when the incident angle is set to 30°. 7 is a graph showing the relationship between Stokes parameter S3 and azimuth during modulation of the optical element according to Example 2 when the incident angle is set to 30°. It is a graph showing the relationship between the Stokes parameter S3 and the retardation Rth in the thickness direction of the negative C plate when the optical element of the example is not modulated. It is a graph showing the relationship between the Stokes parameter S3 during modulation of the optical element of the example and the retardation Rth in the thickness direction of the negative C plate. Graph showing the relationship between the Stokes parameter S3 and the wavelength of the emitted light when the optical elements according to Example 1, Example 3, Comparative Example 1, and Comparative Example 2 are not modulated when the incident angle is set to 0°. It is. A graph showing the relationship between the Stokes parameter S3 during modulation and the wavelength of the emitted light for the optical elements according to Example 1, Example 3, Comparative Example 1, and Comparative Example 2 when the incident angle is set to 0°. be. 7 is a graph showing the relationship between the Stokes parameter S3 and the azimuth when the optical element according to Example 3 is not modulated when the incident angle is set to 30°. 7 is a graph showing the relationship between the Stokes parameter S3 and the azimuth during modulation of the optical element according to Example 3 when the incident angle is set to 30°. 7 is a graph showing the relationship between the Stokes parameter S3 and the wavelength of emitted light when the optical elements according to Example 4, Comparative Example 1, and Comparative Example 2 are not modulated, when the incident angle is set to 0°. 7 is a graph showing the relationship between the Stokes parameter S3 during modulation and the wavelength of emitted light of the optical elements according to Example 4, Comparative Example 1, and Comparative Example 2 when the incident angle is set to 0°. 12 is a graph showing the relationship between the Stokes parameter S3 and the azimuth when the optical element according to Example 4 is not modulated when the incident angle is set to 30°. 7 is a graph showing the relationship between Stokes parameter S3 and azimuth during modulation of the optical element according to Example 4 when the incident angle is set to 30°. FIG. 7 is a schematic diagram illustrating a first alignment process in the manufacturing process of a variable focus element according to Example 5. FIG. 7 is a schematic diagram illustrating a second alignment process in the manufacturing process of the variable focus element according to Example 5. FIG. 7 is a schematic diagram illustrating a third alignment process in the manufacturing process of the variable focus element according to Example 5. FIG. 7 is a schematic diagram illustrating a fourth alignment process in the manufacturing process of the variable focus element according to Example 5. 7 is a graph showing the relationship between the Stokes parameter S3 and the wavelength of emitted light when the optical elements according to Example 6, Comparative Example 1, and Comparative Example 2 are not modulated, when the incident angle is set to 0°. 7 is a graph showing the relationship between the Stokes parameter S3 during modulation and the wavelength of emitted light of the optical elements according to Example 6, Comparative Example 1, and Comparative Example 2 when the incident angle is set to 0°. 12 is a graph showing the relationship between the Stokes parameter S3 and the azimuth when the optical element according to Example 6 is not modulated when the incident angle is set to 30°. 12 is a graph showing the relationship between Stokes parameter S3 and azimuth during modulation of the optical element according to Example 6 when the incident angle is set to 30°. 12 is a graph showing the Stokes parameter S3 at the time of non-modulation with respect to the retardation Rth in the thickness direction of the first positive C plate included in the optical element of Example 6. 12 is a graph showing the Stokes parameter S3 at the time of modulation with respect to the retardation Rth in the thickness direction of the first positive C plate included in the optical element of Example 6. 12 is a graph showing the Stokes parameter S3 at the time of non-modulation with respect to the retardation Rth in the thickness direction of the second positive C plate included in the optical element of Example 6. 7 is a graph showing the Stokes parameter S3 at the time of modulation with respect to the retardation Rth in the thickness direction of the second positive C plate included in the optical element of Example 6. 3 is a schematic cross-sectional view of an optical element having a first configuration according to a second modification of the first embodiment. FIG. 7 is an example of a schematic cross-sectional view of an optical element having a second configuration according to Modification 2 of Embodiment 1. FIG. 7 is an example of a schematic cross-sectional view of an optical element having a second configuration according to Modification 2 of Embodiment 1. FIG. 7 is an example of a schematic cross-sectional view of an optical element having a second configuration according to Modification 2 of Embodiment 1. FIG. 7 is an example of a schematic cross-sectional view of an optical element having a second configuration according to Modification 2 of Embodiment 1. FIG. 7 is an example of a schematic cross-sectional view of an optical element having a third configuration according to Modification 2 of Embodiment 1. FIG. 7 is an example of a schematic cross-sectional view of an optical element having a third configuration according to Modification 2 of Embodiment 1. FIG. 7 is an example of a schematic cross-sectional view of an optical element having a third configuration according to Modification 2 of Embodiment 1. FIG. 7 is an example of a schematic cross-sectional view of an optical element having a third configuration according to Modification 2 of Embodiment 1. FIG. 7 is an example of a schematic cross-sectional view of an optical element having a third configuration according to Modification 2 of Embodiment 1. FIG. 7 is an example of a schematic cross-sectional view of an optical element having a third configuration according to Modification 2 of Embodiment 1. FIG. 7 is an example of a schematic cross-sectional view of an optical element having a fourth configuration according to Modification 2 of Embodiment 1. FIG. 7 is an example of a schematic cross-sectional view of an optical element having a fourth configuration according to Modification 2 of Embodiment 1. FIG. 7 is an example of a schematic cross-sectional view of an optical element having a fourth configuration according to Modification 2 of Embodiment 1. FIG. 7 is an example of a schematic cross-sectional view of an optical element having a fourth configuration according to Modification 2 of Embodiment 1. FIG. 7 is an example of a schematic cross-sectional view of an optical element having a fifth configuration according to Modification 2 of Embodiment 1. FIG. 7 is an example of a schematic cross-sectional view of an optical element having a sixth configuration according to Modification 2 of Embodiment 1. FIG. 7 is an example of a schematic cross-sectional view of an optical element having a sixth configuration according to Modification 2 of Embodiment 1. FIG. 7 is an example of a schematic cross-sectional view of an optical element having a sixth configuration according to Modification 2 of Embodiment 1. FIG. 7 is an example of a schematic cross-sectional view of an optical element having a sixth configuration according to Modification 2 of Embodiment 1. FIG. 7 is an example of a schematic cross-sectional view of an optical element having a sixth configuration according to Modification 2 of Embodiment 1. FIG. 7 is an example of a schematic cross-sectional view of an optical element having a seventh configuration according to Modification 2 of Embodiment 1. FIG. 7 is an example of a schematic cross-sectional view of an optical element having a seventh configuration according to Modification 2 of Embodiment 1. FIG. 7 is an example of a schematic cross-sectional view of an optical element having a seventh configuration according to Modification 2 of Embodiment 1. FIG. 7 is an example of a schematic cross-sectional view of an optical element having a seventh configuration according to Modification 2 of Embodiment 1. FIG. 7 is an example of a schematic cross-sectional view of an optical element having a seventh configuration according to Modification 2 of Embodiment 1. FIG. 7 is an example of a schematic cross-sectional view of an optical element having a seventh configuration according to Modification 2 of Embodiment 1. FIG. 7 is an example of a schematic cross-sectional view of an optical element having a seventh configuration according to Modification 2 of Embodiment 1. FIG. 7 is an example of a schematic cross-sectional view of an optical element having a seventh configuration according to Modification 2 of Embodiment 1. FIG. 7 is an example of a schematic cross-sectional view of an optical element having a seventh configuration according to Modification 2 of Embodiment 1. FIG. 7 is an example of a schematic cross-sectional view of an optical element having an eighth configuration according to Modification 2 of Embodiment 1. FIG. 7 is an example of a schematic cross-sectional view of an optical element having an eighth configuration according to Modification 2 of Embodiment 1. FIG. 7 is an example of a schematic cross-sectional view of an optical element having an eighth configuration according to Modification 2 of Embodiment 1. FIG. 7 is an example of a schematic cross-sectional view of an optical element having an eighth configuration according to Modification 2 of Embodiment 1. FIG. 7 is an example of a schematic cross-sectional view of an optical element having an eighth configuration according to Modification 2 of Embodiment 1. FIG. 7 is an example of a schematic cross-sectional view of an optical element having an eighth configuration according to Modification 2 of Embodiment 1. FIG. 7 is an example of a schematic cross-sectional view of an optical element having an eighth configuration according to Modification 2 of Embodiment 1. FIG. 7 is an example of a schematic cross-sectional view of an optical element having a ninth configuration according to Modification 2 of Embodiment 1. FIG. 7 is an example of a schematic cross-sectional view of an optical element having a ninth configuration according to Modification 2 of Embodiment 1. FIG. 7 is an example of a schematic cross-sectional view of an optical element having a tenth configuration according to Modification 2 of Embodiment 1. FIG. 7 is an example of a schematic cross-sectional view of an optical element having a tenth configuration according to Modification 2 of Embodiment 1. FIG. 7 is an example of a schematic cross-sectional view of an optical element having a tenth configuration according to Modification 2 of Embodiment 1. FIG. 7 is an example of a schematic cross-sectional view of an optical element having a tenth configuration according to Modification 2 of Embodiment 1. FIG. 7 is an example of a schematic cross-sectional view of an optical element having a tenth configuration according to Modification 2 of Embodiment 1. FIG. 7 is an example of a schematic cross-sectional view of an optical element having a tenth configuration according to Modification 2 of Embodiment 1. FIG. 7 is an example of a schematic cross-sectional view of an optical element having an eleventh configuration according to Modification 2 of Embodiment 1. FIG. 7 is an example of a schematic cross-sectional view of an optical element having an eleventh configuration according to Modification 2 of Embodiment 1. FIG. 7 is an example of a schematic cross-sectional view of an optical element having an eleventh configuration according to Modification 2 of Embodiment 1. FIG. 7 is an example of a schematic cross-sectional view of an optical element having an eleventh configuration according to Modification 2 of Embodiment 1. FIG. 7 is an example of a schematic cross-sectional view of an optical element having an eleventh configuration according to Modification 2 of Embodiment 1. FIG. 7 is an example of a schematic cross-sectional view of an optical element having an eleventh configuration according to Modification 2 of Embodiment 1. FIG. 7 is an example of a schematic cross-sectional view of an optical element having an eleventh configuration according to Modification 2 of Embodiment 1. FIG. 7 is an example of a schematic cross-sectional view of an optical element having an eleventh configuration according to Modification 2 of Embodiment 1. FIG. 7 is an example of a schematic cross-sectional view of an optical element having an eleventh configuration according to Modification 2 of Embodiment 1. FIG. 7 is an example of a schematic cross-sectional view of an optical element having an eleventh configuration according to Modification 2 of Embodiment 1. FIG. 7 is an example of a schematic cross-sectional view of an optical element having an eleventh configuration according to Modification 2 of Embodiment 1. FIG. 7 is an example of a schematic cross-sectional view of an optical element having an eleventh configuration according to Modification 2 of Embodiment 1. FIG. 7 is an example of a schematic cross-sectional view of an optical element having an eleventh configuration according to Modification 2 of Embodiment 1. FIG. 7 is an example of a schematic cross-sectional view of an optical element having a twelfth configuration according to Modification 2 of Embodiment 1. FIG. 7 is an example of a schematic cross-sectional view of an optical element having a twelfth configuration according to Modification 2 of Embodiment 1. FIG. 7 is an example of a schematic cross-sectional view of an optical element having a twelfth configuration according to Modification 2 of Embodiment 1. FIG. 7 is an example of a schematic cross-sectional view of an optical element having a twelfth configuration according to Modification 2 of Embodiment 1. FIG. 7 is an example of a schematic cross-sectional view of an optical element having a twelfth configuration according to Modification 2 of Embodiment 1. FIG. 7 is an example of a schematic cross-sectional view of an optical element having a twelfth configuration according to Modification 2 of Embodiment 1. FIG. 7 is an example of a schematic cross-sectional view of an optical element having a twelfth configuration according to Modification 2 of Embodiment 1. FIG. 7 is an example of a schematic cross-sectional view of an optical element having a twelfth configuration according to Modification 2 of Embodiment 1. FIG. 7 is an example of a schematic cross-sectional view of an optical element having a twelfth configuration according to Modification 2 of Embodiment 1. FIG. 7 is an example of a schematic cross-sectional view of an optical element having a twelfth configuration according to Modification 2 of Embodiment 1. FIG. 7 is an example of a schematic cross-sectional view of an optical element having a twelfth configuration according to Modification 2 of Embodiment 1. FIG. 7 is an example of a schematic cross-sectional view of an optical element having a twelfth configuration according to Modification 2 of Embodiment 1. FIG. 7 is an example of a schematic cross-sectional view of an optical element having a thirteenth configuration according to Modification 2 of Embodiment 1. FIG. 7 is an example of a schematic cross-sectional view of an optical element having a thirteenth configuration according to Modification 2 of Embodiment 1. FIG. 7 is an example of a schematic cross-sectional view of an optical element having a thirteenth configuration according to Modification 2 of Embodiment 1. FIG. 7 is an example of a schematic cross-sectional view of an optical element having a thirteenth configuration according to Modification 2 of Embodiment 1. FIG. 7 is an example of a schematic cross-sectional view of an optical element having a fourteenth configuration according to Modification 2 of Embodiment 1. FIG. 7 is an example of a schematic cross-sectional view of an optical element having a fourteenth configuration according to Modification 2 of Embodiment 1. FIG. 7 is an example of a schematic cross-sectional view of an optical element having a fourteenth configuration according to Modification 2 of Embodiment 1. FIG. 7 is an example of a schematic cross-sectional view of an optical element having a fourteenth configuration according to Modification 2 of Embodiment 1. FIG. 7 is an example of a schematic cross-sectional view of an optical element having a fourteenth configuration according to Modification 2 of Embodiment 1. FIG. 7 is an example of a schematic cross-sectional view of an optical element having a fifteenth configuration according to Modification 2 of Embodiment 1. FIG. 7 is an example of a schematic cross-sectional view of an optical element having a fifteenth configuration according to Modification 2 of Embodiment 1. FIG. 7 is an example of a schematic cross-sectional view of an optical element having a fifteenth configuration according to Modification 2 of Embodiment 1. FIG. 7 is an example of a schematic cross-sectional view of an optical element having a fifteenth configuration according to Modification 2 of Embodiment 1. FIG. 7 is an example of a schematic cross-sectional view of an optical element having a fifteenth configuration according to Modification 2 of Embodiment 1. FIG. 7 is an example of a schematic cross-sectional view of an optical element having a fifteenth configuration according to Modification 2 of Embodiment 1. FIG. 7 is an example of a schematic cross-sectional view of an optical element having a fifteenth configuration according to Modification 2 of Embodiment 1. FIG. 7 is an example of a schematic cross-sectional view of an optical element having a fifteenth configuration according to Modification 2 of Embodiment 1. FIG. 7 is an example of a schematic cross-sectional view of an optical element having a fifteenth configuration according to Modification 2 of Embodiment 1. FIG. 7 is an example of a schematic cross-sectional view of an optical element having a sixteenth configuration according to Modification 2 of Embodiment 1. FIG. 7 is an example of a schematic cross-sectional view of an optical element having a sixteenth configuration according to Modification 2 of Embodiment 1. FIG. 7 is an example of a schematic cross-sectional view of an optical element having a sixteenth configuration according to Modification 2 of Embodiment 1. FIG. 7 is an example of a schematic cross-sectional view of an optical element having a sixteenth configuration according to Modification 2 of Embodiment 1. FIG. 7 is an example of a schematic cross-sectional view of an optical element having a sixteenth configuration according to Modification 2 of Embodiment 1. FIG. 7 is an example of a schematic cross-sectional view of an optical element having a sixteenth configuration according to Modification 2 of Embodiment 1. FIG. 7 is an example of a schematic cross-sectional view of an optical element having a sixteenth configuration according to Modification 2 of Embodiment 1. FIG. 7 is an example of a schematic cross-sectional view of an optical element having a seventeenth configuration according to Modification 2 of Embodiment 1. FIG. 7 is an example of a schematic cross-sectional view of an optical element having a seventeenth configuration according to Modification 2 of Embodiment 1. 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 Example 7. 7 is a graph showing the relationship between the Stokes parameter S3 and the wavelength of emitted light when the optical elements according to Examples 1 and 7 are not modulated. 7 is a graph showing the relationship between the Stokes parameter S3 during modulation and the wavelength of emitted light for the optical elements according to Examples 1 and 7. FIG. FIG. 3 is a graph showing the relationship between the Stokes parameter S3 and the azimuth when the optical element according to Example 1 is not modulated when the incident angle is set to 30 degrees. FIG. 7 is a graph showing the relationship between the Stokes parameter S3 and the azimuth during modulation of the optical element according to Example 1 when the incident angle is set to 30°. 12 is a graph showing the relationship between the Stokes parameter S3 and the azimuth when the optical element according to Example 7 is not modulated when the incident angle is set to 30°. 12 is a graph showing the relationship between the Stokes parameter S3 and the azimuth during modulation of the optical element according to Example 7 when the incident angle is set to 30°. 12 is a graph showing the Stokes parameter S3 at the time of non-modulation with respect to the retardation Rth in the thickness direction of the second C plate included in the optical element of Example 7. 7 is a graph showing the Stokes parameter S3 at the time of modulation with respect to the retardation Rth in the thickness direction of the second C plate included in the optical element of Example 7. 12 is a graph showing the Stokes parameter S3 at the time of non-modulation with respect to the retardation Rth in the thickness direction of the first C plate included in the optical element of Example 7. 7 is a graph showing the Stokes parameter S3 at the time of modulation with respect to the retardation Rth in the thickness direction of the first C plate included in the optical element of Example 7. 12 is a graph showing the Stokes parameter S3 at the time of non-modulation with respect to the retardation Rth in the thickness direction of the negative C plate included in the optical element of Example 7. 12 is a graph showing the Stokes parameter S3 at the time of modulation with respect to the retardation Rth in the thickness direction of the negative C plate included in the optical element of Example 7. 12 is a graph showing the Stokes parameter S3 at the time of non-modulation with respect to the in-plane phase difference Re of the second A plate included in the optical element of Example 7. 12 is a graph showing the Stokes parameter S3 during modulation with respect to the in-plane phase difference Re of the second A plate included in the optical element of Example 7. 7 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 second A plate included in the optical element of Example 7. 7 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 second A plate included in the optical element of Example 7. 12 is a graph showing the Stokes parameter S3 at the time of non-modulation with respect to the in-plane phase difference Re of the first A plate included in the optical element of Example 7. 7 is a graph showing the Stokes parameter S3 at the time of modulation with respect to the in-plane phase difference Re of the first A plate included in the optical element of Example 7. 12 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 first A plate included in the optical element of Example 7. 7 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 first A plate included in the optical element of Example 7. It is a figure explaining a polarization state. FIG. 3 is a schematic cross-sectional view of an optical element according to Modification 3 of Embodiment 1; 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 third modification of the first embodiment. 12 is a graph showing the relationship between the Stokes parameter S3 and the wavelength of emitted light when the optical elements according to Example 8, Comparative Example 1, and Comparative Example 2 are not modulated. 7 is a graph showing the relationship between the Stokes parameter S3 during modulation and the wavelength of emitted light for optical elements according to Example 8, Comparative Example 1, and Comparative Example 2. 12 is a graph showing the relationship between the Stokes parameter S3 and the azimuth when the optical element according to Example 8 is not modulated when the incident angle is set to 30°. 12 is a graph showing the relationship between Stokes parameter S3 and azimuth during modulation of the optical element according to Example 8 when the incident angle is set to 30°.

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 in the horizontal right direction of the screen of the liquid crystal panel when the optical element is viewed from the output side. For azimuth angles, counterclockwise rotation is a positive angle, and clockwise rotation is a negative angle. 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°±5°, preferably 90°±3°, more preferably This means 90°±1°, particularly preferably 90° (completely orthogonal). Two straight lines being parallel means that the angle between them is 0°±5°, preferably 0°±3°, more preferably 0°±1°, particularly preferably 0° ( completely 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 cross-sectional view of a first liquid crystal cell and a second 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.

As shown in FIGS. 1 to 3, the optical element 10 of this embodiment includes a first substrate 100, a first liquid crystal layer 500 containing first liquid crystal molecules 510, a second substrate 200, A third substrate 300, a second liquid crystal layer 600 containing second liquid crystal molecules 610, and a fourth substrate 400 are provided in this order, and the first substrate 100, the first liquid crystal layer 500, and the second The substrate 200 constitutes the first liquid crystal cell 11A, and the third substrate 300, the second liquid crystal layer 600, and the fourth substrate 400 constitute the second liquid crystal cell 11B. The first liquid crystal cell 11A has a first solid electrode 120 as the first electrode for applying voltage to the first liquid crystal layer 500 on at least one of the first substrate 100 and the second substrate 200. and a second solid electrode 220. The second liquid crystal cell 11B has a third solid electrode 320 as the second electrode for applying voltage to the second liquid crystal layer 600 on at least one of the third substrate 300 and the fourth substrate 400. and a fourth solid electrode 420. The first electrode and the second electrode have a first state in which the second liquid crystal molecules 610 are twistedly aligned and the first liquid crystal molecules 510 are vertically aligned, and a first state in which the first liquid crystal molecules 510 are twistedly aligned. and a second state in which the second liquid crystal molecules 610 are vertically aligned. The azimuth of the alignment direction 611A of the second liquid crystal molecules 611 on the third substrate 300 side in the first state and the azimuth of the alignment direction 612A of the second liquid crystal molecules 612 on the fourth substrate 400 side in the first state The angle is the azimuth angle of the orientation direction 511A of the first liquid crystal molecules 511 on the first substrate 100 side in the second state, and the azimuth angle of the first liquid crystal molecules 512 on the second substrate 200 side in the second state, respectively. This is an angle obtained by rotating the azimuth angle of the alignment direction 512A by 1/4 in the same direction. By adopting such an aspect, it becomes possible to drive the first state and the second state in the same manner except that the entire system is rotated by 1/4, and the first state and the second state can be driven in the same manner with the exception of rotating the entire system by 1/4. It becomes possible to realize polarization modulation in one of the second states and to realize polarization non-modulation in the other state. That is, it is possible to realize an optical element that can switch between polarization modulation and polarization non-modulation over a wide band and wide viewing angle, more specifically, a variable half wave plate (sHWP) element.

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 500R1 twisted by 90° as shown in FIG. 4 is considered. It will be done. More specifically, the optical element 10R1 of Comparative Form 1 includes a 1/4 wavelength film 15R whose slow axis has an azimuth angle of 75°, and a 1/2 wavelength film whose slow axis has an azimuth angle of 15°. 16R, the liquid crystal cell 11R1, the 1/2 wavelength film 17R whose slow axis has an azimuth of -75°, and the 1/4 wavelength film 18R whose slow axis has an azimuth of -15°. Be prepared. FIG. 4 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 500R2 with a 70° twist and a TN liquid crystal layer 500R3 with a -70° twist are laminated, as shown in FIG. A configuration of the element 10R2 is considered. FIG. 5 is a schematic cross-sectional view of an optical element according to Comparative Form 2.

FIG. 6 is a graph showing the relationship between the Stokes parameter S3 during modulation and the wavelength of emitted light for the optical elements according to Embodiment 1, Comparative Form 1, and Comparative Form 2. FIG. 6 shows the wavelength dependence of the polarization state of emitted light when right-handed circularly polarized light (Stokes parameter S3=+1) is incident. The closer S3 is to -1, the more the light is converted to left-handed circularly polarized light. The closer it is to -1 over a wide range of wavelengths, the more broadband it can be said to be 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. 6 due to the influence of wavelength dispersion of the 90° twisted TN liquid crystal layer 500R1. Further, in the optical element 10R2 of Comparative Form 2, it is possible to achieve a wide band by stacking liquid crystal layers twisted by about 70 degrees, but it is difficult to achieve a wide viewing angle. On the other hand, the optical element 10 of this embodiment can switch between polarization modulation and polarization non-modulation over a wide band and wide viewing angle.

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.

More specifically, in the single-layer structure disclosed in Patent Document 1, liquid crystal molecules are twisted at 90° during polarization modulation, and when polarization is not modulated, liquid crystal molecules are vertically aligned due to the application of a vertical electric field. Orient. During polarization modulation, liquid crystal molecules are oriented in a 90° twist, so there is wavelength dependence, and polarization modulation cannot be achieved over a wide band. Even if polarization modulation could be achieved over a wide band by adjusting the twist angle of the liquid crystal molecules, the cell thickness of the liquid crystal layer, etc., when the polarization is not modulated, the polarization will be unmodulated over a wide band due to the influence of residual retardation from the liquid crystal molecules near the substrate. Modulation cannot be achieved. In other words, it is not possible to simultaneously perform polarization modulation and non-modulation in a wide band.

Patent Document 5 does not disclose any modulation characteristics. Furthermore, there is no description of specific physical properties of the retardation film or the like. Furthermore, since one of the stacked liquid crystal cells in Patent Document 5 is used as a backup, it is considered that the cell design is the same as that of the other liquid crystal cell.

This embodiment will be described in detail below.

The alignment direction of the first liquid crystal molecules on the first substrate side is the alignment direction of the first liquid crystal molecules horizontally aligned in the vicinity of the first substrate. More specifically, when the alignment film provided on the first liquid crystal layer side of the first substrate is a horizontal alignment film, the alignment direction of the first liquid crystal molecules on the first substrate side is the first refers to the alignment direction of the first liquid crystal molecules located at the interface of the liquid crystal layer on the first substrate side. If the alignment film provided on the first liquid crystal layer side of the first substrate is a vertical alignment film, the liquid crystal molecules located at the interface of the first liquid crystal layer on the first substrate side are vertically aligned. , the orientation direction of the first liquid crystal molecules on the first substrate side is the orientation direction of the first liquid crystal molecules in a horizontally aligned state located inside the first liquid crystal layer from the interface on the first substrate side. means.

Similarly, the alignment direction of the first liquid crystal molecules on the second substrate side is the alignment direction of the first liquid crystal molecules horizontally aligned in the vicinity of the second substrate. More specifically, when the alignment film provided on the first liquid crystal layer side of the second substrate is a horizontal alignment film, the alignment direction of the first liquid crystal molecules on the second substrate side is the first liquid crystal layer. refers to the orientation direction of the first liquid crystal molecules located at the interface of the liquid crystal layer on the second substrate side. If the alignment film provided on the first liquid crystal layer side of the second substrate is a vertical alignment film, the liquid crystal molecules located at the interface of the first liquid crystal layer on the second substrate side are vertically aligned. , the orientation direction of the first liquid crystal molecules on the second substrate side is the orientation direction of the first liquid crystal molecules in a horizontally aligned state located inside the first liquid crystal layer from the interface on the second substrate side. means.

Similarly, the alignment direction of the second liquid crystal molecules on the third substrate side is the alignment direction of the second liquid crystal molecules horizontally aligned in the vicinity of the third substrate. More specifically, when the alignment film provided on the second liquid crystal layer side of the third substrate is a horizontal alignment film, the alignment direction of the second liquid crystal molecules on the third substrate side is the second liquid crystal layer side. refers to the alignment direction of the second liquid crystal molecules located at the interface of the liquid crystal layer on the third substrate side. If the alignment film provided on the second liquid crystal layer side of the third substrate is a vertical alignment film, the liquid crystal molecules located at the interface of the second liquid crystal layer on the third substrate side are vertically aligned. , the orientation direction of the second liquid crystal molecules on the third substrate side is the orientation direction of the second liquid crystal molecules in a horizontally aligned state located inside the second liquid crystal layer from the interface on the third substrate side. means.

Similarly, the alignment direction of the second liquid crystal molecules on the fourth substrate side is the alignment direction of the second liquid crystal molecules horizontally aligned in the vicinity of the fourth substrate. More specifically, when the alignment film provided on the second liquid crystal layer side of the fourth substrate is a horizontal alignment film, the alignment direction of the second liquid crystal molecules on the fourth substrate side is the second liquid crystal layer side. refers to the orientation direction of the second liquid crystal molecules located at the interface of the liquid crystal layer on the fourth substrate side. If the alignment film provided on the second liquid crystal layer side of the fourth substrate is a vertical alignment film, the liquid crystal molecules located at the interface of the second liquid crystal layer on the fourth substrate side are vertically aligned. , the orientation direction of the second liquid crystal molecules on the fourth substrate side is the orientation direction of the second liquid crystal molecules in a horizontally aligned state located inside the second liquid crystal layer from the interface on the fourth substrate side. means.

The azimuthal angle of the alignment direction of the second liquid crystal molecules on the third substrate side in the first state and the azimuth angle of the alignment direction of the second liquid crystal molecules on the fourth substrate side in the first state are respectively the second The azimuthal angle of the alignment direction of the first liquid crystal molecules on the first substrate side in the state and the azimuth angle of the alignment direction of the first liquid crystal molecules on the second substrate side in the second state are rotated by 1/4 in the same direction. The angle refers to the azimuth angle of the alignment direction of the second liquid crystal molecules on the third substrate side in the first state and the azimuth angle of the alignment direction of the second liquid crystal molecules on the fourth substrate side in the first state. The angle is the azimuthal angle of the alignment direction of the first liquid crystal molecules on the first substrate side in the second state, and the azimuth angle of the alignment direction of the first liquid crystal molecules on the second substrate side in the second state, respectively. or the azimuth angle of the alignment direction of the second liquid crystal molecules on the third substrate side in the first state and the second angle on the fourth substrate side in the first state. The azimuth angle of the alignment direction of the liquid crystal molecules is the azimuth angle of the alignment direction of the first liquid crystal molecules on the first substrate side in the second state and the azimuth angle of the alignment direction of the first liquid crystal molecules on the second substrate side in the second state, respectively. It is an angle obtained by rotating the azimuth angle of the alignment direction by 1/4 in the negative direction.

Here, 1/4 rotation means 80° or more and 100° or less, preferably 85° or more and 95° or less, and more preferably 87° or more and 93° or less.

The first liquid crystal cell 11A includes, in order from the incident side to the output side, a first substrate 100, a first liquid crystal layer 500 containing first liquid crystal molecules 510, and a second substrate 200. Be prepared. The first substrate 100 includes a first support substrate 110 and a first solid electrode 120, and the second substrate 200 includes a second support substrate 210 and a second solid electrode 220.

The second liquid crystal cell 11B includes, in order from the incident side to the output side, a third substrate 300, a second liquid crystal layer 600 containing second liquid crystal molecules 610, and a fourth substrate 400. Be prepared. The third substrate 300 includes a third support substrate 310 and a third solid electrode 320, and the fourth substrate 400 includes a fourth support substrate 410 and a fourth solid electrode 420.

Examples of the first support substrate 110, the second support substrate 210, the third support substrate 310, and the fourth support substrate 410 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 for the plastic substrate include plastics such as polyethylene terephthalate, polybutylene terephthalate, polyether sulfone, polycarbonate, polyimide, and alicyclic polyolefin.

The first solid electrode 120, the second solid electrode 220, the third solid electrode 320, and the fourth solid electrode 420 are made of, for example, indium tin oxide (ITO), indium zinc oxide (IZO), A transparent conductive material such as zinc (ZnO), tin oxide (SnO), or an alloy thereof is formed into a single layer or multiple layers by a sputtering method, etc., and then patterned using a photolithography method. It can be formed by In this specification, a solid electrode refers to an electrode in which a slit or opening is not provided at least in a region that overlaps with an optical aperture of a picture element in plan view.

One of the first solid electrode 120 and the second solid electrode 220 is a pixel electrode, and the other is a common electrode. One of the third solid electrode 320 and the fourth solid electrode 420 is a pixel electrode, and the other is a common electrode.

The first liquid crystal layer 500 includes a liquid crystal material, and by applying a voltage to the first liquid crystal layer 500, the alignment state of the first liquid crystal molecules 510 in the liquid crystal material is changed according to the applied voltage. By doing so, the polarization state of light passing through the first liquid crystal layer 500 can be changed.

The second liquid crystal layer 600 includes a liquid crystal material, and by applying a voltage to the second liquid crystal layer 600, the alignment state of the second liquid crystal molecules 610 in the liquid crystal material is changed according to the applied voltage. By doing so, the polarization state of light passing through the second liquid crystal layer 600 can be changed.

The first liquid crystal molecule 510 and the second liquid crystal molecule 610 may be positive type liquid crystal molecules having a positive dielectric anisotropy (Δε) defined by the following formula (L), or It may be a negative type liquid crystal molecule having a value of . Alternatively, one of the first liquid crystal molecules 510 and the second liquid crystal molecules 610 may be a positive type liquid crystal molecule, and the other may be a negative type liquid crystal molecule. This embodiment will be described using an example in which the first liquid crystal molecule 510 and the second liquid crystal molecule 610 are positive liquid crystal molecules. Note that the long axis direction of the liquid crystal molecules is the slow axis direction.
Δε = (permittivity in the long axis direction of liquid crystal molecules) - (permittivity in the short axis direction of liquid crystal molecules) (L)

The first liquid crystal layer 500 contains first liquid crystal molecules 510 that are twistedly aligned between the first substrate 100 and the second substrate 200. In the second state, the first liquid crystal molecules 510 are twisted and oriented from the first substrate 100 side to the second substrate 200 side.

The second liquid crystal layer 600 contains second liquid crystal molecules 610 that are twistedly aligned between the third substrate 300 and the fourth substrate 400. In the first state, the second liquid crystal molecules 610 are twisted and oriented from the third substrate 300 side to the fourth substrate 400 side.

The twisted orientation of the first liquid crystal molecules 510 and the second liquid crystal molecules 610 can be realized, 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.

The first liquid crystal molecule 510 and the second liquid crystal molecule 610 of this embodiment are positive-type liquid crystal molecules with twisted orientation. Therefore, when the first liquid crystal layer 500 is in a voltage applied state and the second liquid crystal layer 600 is in a non-voltage applied state, the first liquid crystal molecules 510 are vertically aligned, and the second liquid crystal molecules 610 It is possible to realize the first state in which the crystals are oriented in a twisted manner. Further, when the first liquid crystal layer 500 is in a state where no voltage is applied and the second liquid crystal layer 600 is in a state where a voltage is applied, the first liquid crystal molecules 510 are twistedly aligned, and the second liquid crystal molecules 610 It is possible to realize a second state in which the particles are vertically aligned. In this embodiment, polarization non-modulation can be achieved in the first state, and polarization modulation can be achieved in the second state.

The retardation of the first liquid crystal layer 500 in the second state at a wavelength of 550 nm is 200 nm or more and 260 nm or less, and the retardation of the second liquid crystal layer 600 in the first state at a wavelength of 550 nm is 210 nm or more and 260 nm or more. It is preferable that it is below. By adopting such an aspect, polarization modulation and polarization non-modulation can be switched over a wider band. In this specification, a voltage application state in which a voltage equal to or higher than a threshold is applied to the liquid crystal layer is also simply referred to as a "voltage application state" or "at the time of voltage application", and a voltage application state in which a voltage less than the threshold is applied to the liquid crystal layer (no voltage applied) A state in which no voltage is applied (including voltage applied) is also simply referred to as a "state in which no voltage is applied" or "when no voltage is applied."

The first liquid crystal molecules 510 in the second state are twisted oriented with a twist angle of 61° or more and 75° or less, and the second liquid crystal molecules 610 in the first state are twisted oriented with a twist angle of 64° or more and 74° or less. It is preferable to do so. By adopting such an aspect, polarization modulation and polarization non-modulation can be switched over a wider band. The twist angle of the liquid crystal molecules can be determined by measuring the Mueller matrix after exiting the liquid crystal layer using Axoscan (manufactured by Optoscience).

The twist angle of the first liquid crystal molecules 510 in the second state is the azimuth angle of the alignment direction 511A of the first liquid crystal molecules 511 on the first substrate 100 side in the second state, and the twist angle of the first liquid crystal molecules 510 on the second substrate 200 side in the second state. This refers to the angle formed by the azimuth angle of the alignment direction 512A of the liquid crystal molecules 512. The twist angle of the second liquid crystal molecules 610 in the first state is the azimuth angle of the alignment direction 611A of the second liquid crystal molecules 611 on the third substrate 300 side in the first state, and the second twist angle on the fourth substrate 400 side in the first state. This refers to the angle formed by the azimuth angle of the alignment direction 612A of the liquid crystal molecules 612.

The azimuth angle of the orientation direction 511A of the first liquid crystal molecules 511 on the first substrate 100 side in the second state is -9° or more and 7° or less, and the second The azimuth angle of the alignment direction 611A of the liquid crystal molecules 611 is preferably 85° or more and 96° or less. By adopting such an aspect, polarization modulation and polarization non-modulation can be switched over a wider band. For example, the azimuth angle of the orientation direction 511A of the first liquid crystal molecules 511 on the first substrate 100 side in the second state is 0°, and the orientation angle of the second liquid crystal molecules 611 on the third substrate 300 side in the first state is 0°. The azimuth angle of direction 611A can be set to 90°.

The first liquid crystal cell 11A includes a first alignment film 41 on the first liquid crystal layer 500 side of the first substrate 100, and a second alignment film 41 on the first liquid crystal layer 500 side of the second substrate 200. 42 is preferable. The second liquid crystal cell 11B includes a third alignment film 43 on the second liquid crystal layer 600 side of the third substrate 300, and a fourth alignment film 43 on the second liquid crystal layer 600 side of the fourth substrate 400. 44 is preferred.

The first alignment film 41 and the second alignment film 42 have a function of controlling the alignment of the first liquid crystal molecules 510 in the first liquid crystal layer 500, and the first alignment film 41 and the second alignment film 42 have a function of controlling the alignment of the first liquid crystal molecules 510 in the first liquid crystal layer 500. In some cases, the alignment of the first liquid crystal molecules 510 in the first liquid crystal layer 500 is controlled mainly by the functions of the first alignment film 41 and the second alignment film 42 .

The third alignment film 43 and the fourth alignment film 44 have a function of controlling the alignment of the second liquid crystal molecules 610 in the second liquid crystal layer 600, and when the second liquid crystal layer 600 is in a state where no voltage is applied. In some cases, the alignment of the second liquid crystal molecules 610 in the second liquid crystal layer 600 is controlled mainly by the functions of the third alignment film 43 and the fourth alignment film 44 . The first alignment film 41, the second alignment film 42, the third alignment film 43, and the fourth alignment film 44 are also simply referred to as alignment films below.

As the material for the alignment film, common materials in the field of liquid crystal display panels can be used, such as polymers having polyimide in the main chain, polymers having polyamic acid in the main chain, polymers having polysiloxane in the main chain, and the like. The alignment film can be formed by applying an alignment film material, and the coating method is not particularly limited, and for example, flexographic printing, inkjet coating, etc. can be used.

The alignment film may be a horizontal alignment film that aligns the liquid crystal molecules substantially horizontally to the film surface, or a vertical alignment film that aligns the liquid crystal molecules substantially perpendicularly to the film surface. In this embodiment, a case will be described in which the first alignment film 41, the second alignment film 42, the third alignment film 43, and the fourth alignment film 44 are horizontal alignment films.

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 in the pixel region when no voltage is applied to the liquid crystal layer. Here, the expression that 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° to 5° with respect to the surface of the horizontal alignment film, and preferably This means 0° to 2°, more preferably 0° to 1°. 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 each substrate when no voltage is applied to the liquid crystal layer.

The vertical alignment film 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 in the pixel region when no voltage is applied to the liquid crystal layer. 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° to 90° with respect to the surface of the vertical alignment film, and preferably It means 87° to 89°, more preferably 87.5° to 89°.

Further, the alignment film may be a photo-alignment film that has a photo-functional group and has been subjected to a photo-alignment treatment as an alignment treatment, or may be a rubbed alignment film that has been subjected to a rubbing treatment as an alignment treatment. good. By performing alignment treatment, pretilt can be imparted to liquid crystal molecules.

Since the orientation direction of the liquid crystal molecules is the direction of the main axis of orientation (the direction in which the long axes of molecules are aligned on average in nematic liquid crystal), the azimuth angle of the orientation direction 511A of the first liquid crystal molecules 511 on the first substrate 100 side is , coincides with the azimuth angle of the alignment treatment direction of the alignment film (first alignment film 41) provided on the first liquid crystal layer 500 side of the first substrate 100. The azimuth angle of the alignment direction 512A of the first liquid crystal molecules 512 on the second substrate 200 side is the azimuth angle of the alignment film (second alignment film 42) provided on the first liquid crystal layer 500 side of the second substrate 200. Matches the azimuth of the orientation process direction. The azimuth angle of the alignment direction 611A of the second liquid crystal molecules 611 on the third substrate 300 side is determined by the orientation angle of the alignment film (third alignment film 43) provided on the second liquid crystal layer 600 side of the third substrate 300. Matches the azimuth of the orientation process direction. The azimuth of the orientation direction 612A of the second liquid crystal molecules 612 on the fourth substrate 400 side is the orientation angle of the alignment film (fourth alignment film 44) provided on the second liquid crystal layer 600 side of the fourth substrate 400. Matches the azimuth of the orientation process direction.

FIG. 7 is a schematic cross-sectional view illustrating the first state of the optical element according to the first embodiment. FIG. 8 is a schematic cross-sectional view illustrating the second state of the optical element according to the first embodiment. It is preferable that the optical element 10 of this embodiment includes a negative C plate 12 between the first liquid crystal cell 11A and the second liquid crystal cell 11B. By adopting such an aspect, as shown in FIG. 7, in the first state, it becomes possible to cancel the phase difference when the first liquid crystal cell 11A is obliquely incident on the negative C plate 12. Further, as shown in FIG. 8, in the second state, it is possible to cancel the phase difference when the second liquid crystal cell 11B is obliquely incident with the negative C plate 12. As a result, it becomes possible to enable only the liquid crystal layer that is not driven, and it is possible to switch between polarization modulation and non-polarization modulation over a wider band and wider viewing angle.

An example of the negative C plate 12 is a stretched cycloolefin polymer film.

The retardation Rth in the thickness direction of the negative C plate 12 is preferably −220 nm or more and 0 nm or less. By adopting such an aspect, polarization modulation and polarization non-modulation can be switched over a wider band. Because the negative C plate 12 may have an in-plane retardation of several nanometers due to manufacturing reasons, the in-plane retardation of the negative C plate 12 is, for example, 0 nm or more and 5 nm or less.

As shown in FIG. 1 etc., the optical element 10 of this embodiment is arranged on the opposite side of the first liquid crystal cell 11A to the second liquid crystal cell 11B, or on the side opposite to the first liquid crystal cell 11A of the second liquid crystal cell 11B. Preferably, a first quarter wavelength film 13 is provided on the opposite side. By adopting such an aspect, polarization modulation and polarization non-modulation can be switched over a wider band.

The optical element 10 of this embodiment may include a second quarter wavelength film 14 on the opposite side of the first quarter wavelength film 13 from the first liquid crystal cell 11A and the second liquid crystal cell 11B. preferable. By adopting such an aspect, it is possible to switch between polarization modulation and polarization non-modulation in a wider band.

The 1/4 wavelength film (specifically, the first 1/4 wavelength film 13 and the second 1/4 wavelength film 14) 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 13 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 13 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 13 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 azimuth angle of the slow axis 13A of the first quarter-wavelength film 13 shown in FIG. 3 is preferably 52° or more and 60° 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 13 at a wavelength of 550 nm is preferably 90 nm or more and 170 nm or less. By adopting such an aspect, polarization modulation and polarization non-modulation can be switched over a wider band.

The second quarter-wavelength film 14 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 azimuth angle of the slow axis 14A of the second quarter-wavelength film 14 shown in FIG. 3 is preferably 8° or more and 18° 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 second quarter-wavelength film 14 at a wavelength of 550 nm is preferably 120 nm or more and 150 nm or less. By adopting such an aspect, polarization modulation and polarization non-modulation can be switched over a wider band.

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 1 of Embodiment 1)
In this modification, the optical element 10 of Embodiment 1 further includes a first positive C plate on the opposite side of the first liquid crystal cell 11A to the second liquid crystal cell 11B; An embodiment in which a second positive C plate is provided on the opposite side of the first liquid crystal cell 11A will be described.

FIG. 9 is a schematic cross-sectional view of an optical element according to Modification 1 of Embodiment 1. As shown in FIG. 9, the optical element 10 of this embodiment further includes a first positive C plate 19A on the opposite side of the first liquid crystal cell 11A to the second liquid crystal cell 11B, and the second liquid crystal cell A second positive C plate 19B is provided on the opposite side of the liquid crystal cell 11B from the first liquid crystal cell 11A. By adopting such an aspect, polarization modulation and polarization non-modulation can be realized over a wider band.

As shown in FIG. 9, the second positive C plate 19B is preferably disposed between the second liquid crystal cell 11B and the first quarter wavelength film 13. By adopting such an aspect, polarization modulation and polarization non-modulation can be realized over a wider band.

As the first positive C plate 19A and the second positive C plate 19B, for example, a film containing a material with negative intrinsic birefringence as a component is stretched vertically and horizontally, or a liquid crystal material such as nematic liquid crystal is coated. Those that have been prepared can be used as appropriate.

The retardation Rth in the thickness direction of the first positive C plate 19A is preferably 0 nm or more and 190 nm or less. By adopting such an aspect, polarization modulation and polarization non-modulation can be switched over a wider band.

The retardation Rth in the thickness direction of the second positive C plate 19B is preferably 0 nm or more and 220 nm or less. By adopting such an aspect, polarization modulation and polarization non-modulation can be switched over a wider band.

The first positive C plate 19A and the second positive C plate 19B may have an in-plane phase difference of several nanometers due to production reasons. The in-plane retardation of 19B is, for example, 0 nm or more and 5 nm or less. Note that the retardation Rth in the thickness direction of the first positive C plate 19A and the second positive C plate 19B may be the same or different from each other. Moreover, the in-plane phase difference of the first positive C plate 19A and the second positive C plate 19B may be the same or different from each other.

(Modification 2 of Embodiment 1)
In the first modification of the first embodiment, the optical element 10 includes a first positive C plate 19A on the opposite side of the first liquid crystal cell 11A to the second liquid crystal cell 11B, and Although an embodiment has been described in which the second positive C plate 19B, the first 1/4 wavelength film 13, and the second 1/4 wavelength film 14 are provided on the side opposite to the first liquid crystal cell 11A, the first liquid crystal cell The first positive C plate 19A may not be arranged on the opposite side of the second liquid crystal cell 11A from the second liquid crystal cell 11B, but is arranged on the opposite side from the first liquid crystal cell 11A of the second liquid crystal cell 11B. The retardation layer is not limited to the aspect of Modification 1 of Embodiment 1, and may have the following aspects.

<First configuration>
FIG. 81 is a schematic cross-sectional view of an optical element having a first configuration according to Modification 2 of Embodiment 1. As shown in FIG. 81, the optical element 10 having the first configuration according to the second modification of the first embodiment has a first A plate on the opposite side of the second liquid crystal cell 11B from the first liquid crystal cell 11A. 51, and a second A plate 52 disposed on the output side of the first A plate 51. That is, the optical element 10 includes, on the opposite side of the second liquid crystal cell 11B from the first liquid crystal cell 11A, a first A plate 51 and a second A plate 52 in order from the side closest to the second liquid crystal cell 11B. Equipped with. Further, the first positive C plate 19A is not arranged on the opposite side of the first liquid crystal cell 11A from the second liquid crystal cell 11B.

The A plate has a refractive index (nx, ny, nz) that satisfies the following (Formula N1) or (Formula N2). An A plate that satisfies (Formula N1) is also referred to as a positive A plate. An A plate that satisfies (Formula N2) is also referred to as a negative A plate. It is preferable that the first A plate 51 and the second A plate 52 are positive A plates. The first 1/4 wavelength film 13 and the second 1/4 wavelength film 14 in the first embodiment are positive A plates, and the first A plate 51 and the second A plate 52 are positive A plates. In some cases, the first quarter wavelength film 13 in the first embodiment above corresponds to the first A plate 51, and the second quarter wavelength film 14 corresponds to the second A plate 52. Note that due to manufacturing variations, the positive A plate may have nx>ny>nz, and the negative A plate may have nz>nx>ny or nx>nz>ny.
nx>ny=nz (Formula N1)
nz=nx>ny (Formula N2)

Here, "nx" is the refractive index in the direction in which the in-plane refractive index is maximum (i.e., the slow axis direction), and "ny" is the refractive index in the in-plane direction perpendicular to the slow axis. where "nz" is the refractive index in the thickness direction. Unless otherwise specified, the refractive index refers to a value for light at 23° C. and a wavelength of 550 nm. Further, the incident side refers to the side of the optical element where light enters, and the output side refers to the side of the optical element from which light exits.

The first A plate 51 may have reverse wavelength dispersion characteristics, flat wavelength dispersion characteristics, or positive wavelength dispersion characteristics (normal wavelength dispersion characteristics); It is preferable to have wavelength dispersion characteristics. The second A plate 52 may have reverse wavelength dispersion characteristics, flat wavelength dispersion characteristics, or positive wavelength dispersion characteristics, but may have flat wavelength dispersion characteristics or positive wavelength dispersion characteristics. Preferably, it has dispersion properties.

Based on the first configuration shown in FIG. 81, it is preferable to arrange the retardation layer so as to satisfy at least one of (condition 1) to (condition 5) shown below. Note that the C plate has a refractive index (nx, ny, nz) that satisfies the following (Formula N3) or (Formula N4). A C plate that satisfies (Formula N3) is also referred to as a positive C plate. A C plate that satisfies (Formula N4) is also referred to as a negative C plate. Note that due to manufacturing variations, the C plate may have an in-plane retardation Re of several nm.
nz>nx=ny (Formula N3)
nx=ny>nz (Formula N4)

(Condition 1) The optical element 10 has a positive polarity on at least one of the first liquid crystal cell 11A on the side opposite to the second liquid crystal cell 11B and the second liquid crystal cell 11B on the side opposite to the first liquid crystal cell 11A. Equipped with a C plate. By adopting such an aspect, the viewing angle can be improved.
(Condition 2) When at least one of the first A plate 51 and the second A plate 52 is a positive A plate, the optical element 10 has a positive C on at least one of the incident side and the exit side of the positive A plate. Equipped with a plate. By adopting such an aspect, the viewing angle can be improved.
(Condition 3) When at least one of the first A plate 51 and the second A plate 52 is a negative A plate, the optical element 10 has a negative C on at least one of the incident side and the exit side of the negative A plate. Equipped with a plate. By adopting such an aspect, the viewing angle can be improved.
(Condition 4) When at least one of the first A plate 51 and the second A plate 52 is a negative A plate, the optical element 10 is provided between the second liquid crystal cell 11B and the negative A plate. Equipped with a C plate or a negative C plate. By adopting such an aspect, the viewing angle can be improved.
(Condition 5) When one of the first A plate 51 and the second A plate 52 is a positive A plate and the other is a negative A plate, there is a positive Equipped with a C plate or a negative C plate. By adopting such an aspect, the viewing angle can be improved.

In addition to the first configuration, configurations (second configuration to seventeenth configuration) that satisfy at least one of the conditions shown in (Condition 1) to (Condition 5) above will be described below.

<Second configuration>
82 to 85 are examples of schematic cross-sectional views of an optical element having the second configuration according to the second modification of the first embodiment. As shown in FIGS. 82 to 85, in the optical element 10 of the second configuration, in the first configuration, the first A plate 51 is a positive A plate 51PA, and the second A plate 52 is a positive A plate 51PA. The plate 52PA further includes a C plate 61, and the C plate 61 is located on the side opposite to the second liquid crystal cell 11B of the first liquid crystal cell 11A, or on the side opposite to the first liquid crystal cell 11A of the second liquid crystal cell 11B. is placed on the opposite side.

When the C plate 61 is disposed on the opposite side of the first liquid crystal cell 11A to the second liquid crystal cell 11B, the C plate 61 is preferably a positive C plate 61PC. When the C plate 61 is arranged on the opposite side of the second liquid crystal cell 11B from the first liquid crystal cell 11A, and the positive A plate 52PA is arranged adjacent to the incident side of the C plate 61, the C plate 61 , a positive C plate 61PC is preferable.

<Third configuration>
86 to 91 are examples of schematic cross-sectional views of an optical element having the third configuration according to the second modification of the first embodiment. As shown in FIGS. 86 to 91, in the optical element 10 of the third configuration, in the first configuration, the first A plate 51 is a positive A plate 51PA, and the second A plate 52 is a positive A plate 51PA. The plate 52PA further includes a first C plate 61 and a second C plate 62 arranged on the output side of the first C plate 61. The first C plate 61 is disposed on the opposite side of the first liquid crystal cell 11A to the second liquid crystal cell 11B, or on the opposite side of the second liquid crystal cell 11B to the first liquid crystal cell 11A, and The C plate 62 is arranged on the side of the second liquid crystal cell 11B opposite to the first liquid crystal cell 11A.

When the first C plate 61 is disposed on the opposite side of the first liquid crystal cell 11A to the second liquid crystal cell 11B, the first C plate 61 is preferably a positive C plate 61PC. The second C plate 62 is arranged on the opposite side of the second liquid crystal cell 11B from the first liquid crystal cell 11A, and the positive A plate 52PA is arranged adjacent to the incident side of the second C plate 62. In this case, the second C plate 62 is preferably a positive C plate 62PC. Note that the configuration shown in FIG. 91 corresponds to the configuration of Embodiment 1 described above.

When a plurality of C plates are arranged on the opposite side of the first liquid crystal cell 11A of the second liquid crystal cell 11B, it is preferable that the plurality of C plates are not adjacent to each other, and specifically, the plurality of C plates Preferably, at least one A plate is arranged in between.

<Fourth configuration>
92 to 95 are examples of schematic cross-sectional views of an optical element having the fourth configuration according to the second modification of the first embodiment. As shown in FIGS. 92 to 95, in the optical element 10 of the fourth configuration, in the first configuration, the first A plate 51 is a positive A plate 51PA, and the second A plate 52 is a positive A plate 51PA. The plate 52PA further includes a first C plate 61, a second C plate 62 disposed on the output side of the first C plate 61, and a second C plate 62 disposed on the output side of the second C plate 62. A third C plate 63 is provided. The first C plate 61 is disposed on the opposite side of the first liquid crystal cell 11A to the second liquid crystal cell 11B, or on the opposite side of the second liquid crystal cell 11B to the first liquid crystal cell 11A, and The C plate 62 and the third C plate 63 are arranged on the opposite side of the second liquid crystal cell 11B from the first liquid crystal cell 11A.

When the first C plate 61 is disposed on the opposite side of the first liquid crystal cell 11A to the second liquid crystal cell 11B, the first C plate 61 is preferably a positive C plate 61PC. A third C plate 63 is arranged on the opposite side of the second liquid crystal cell 11B from the first liquid crystal cell 11A, and a positive A plate 52PA is arranged adjacent to the incident side of the third C plate 63. In this case, the third C plate 63 is preferably a positive C plate 63PC.

When a plurality of C plates are arranged on the opposite side of the first liquid crystal cell 11A of the second liquid crystal cell 11B, it is preferable that the plurality of C plates are not adjacent to each other, and specifically, the plurality of C plates Preferably, at least one A plate is arranged in between.

<Fifth configuration>
FIG. 96 is an example of a schematic cross-sectional view of an optical element having a fifth configuration according to Modification 2 of Embodiment 1. As shown in FIG. 96, in the optical element 10 of the fifth configuration, in the first configuration, the first A plate 51 is a positive A plate 51PA, and the second A plate 52 is a positive A plate 52PA. In addition, a first C plate 61, a second C plate 62 disposed on the output side of the first C plate 61, and a third C plate 62 disposed on the output side of the second C plate 62. It includes a plate 63 and a fourth C plate 64 arranged on the output side of the third C plate 63. The first C plate 61 is disposed on the opposite side of the first liquid crystal cell 11A to the second liquid crystal cell 11B, or on the opposite side of the second liquid crystal cell 11B to the first liquid crystal cell 11A, and The C plate 62, the third C plate 63, and the fourth C plate 64 are arranged on the opposite side of the second liquid crystal cell 11B from the first liquid crystal cell 11A.

When the first C plate 61 is disposed on the opposite side of the first liquid crystal cell 11A to the second liquid crystal cell 11B, the first C plate 61 is preferably a positive C plate 61PC. A fourth C plate 64 is arranged on the opposite side of the second liquid crystal cell 11B from the first liquid crystal cell 11A, and a positive A plate 52PA is arranged adjacent to the incident side of the fourth C plate 64. In this case, the fourth C plate 64 is preferably a positive C plate 64PC.

When a plurality of C plates are arranged on the opposite side of the first liquid crystal cell 11A of the second liquid crystal cell 11B, it is preferable that the plurality of C plates are not adjacent to each other, and specifically, the plurality of C plates Preferably, at least one A plate is arranged in between.

<Sixth configuration>
97 to 101 are examples of schematic cross-sectional views of an optical element having the sixth configuration according to the second modification of the first embodiment. As shown in FIGS. 97 to 101, in the optical element 10 of the sixth configuration, in the first configuration, the first A plate 51 is a positive A plate 51PA, and the second A plate 52 is a negative A plate 51PA. The plate 52NA further includes a C plate 61, and the C plate 61 is located on the side opposite to the second liquid crystal cell 11B of the first liquid crystal cell 11A, or on the side opposite to the first liquid crystal cell 11A of the second liquid crystal cell 11B. is placed on the opposite side.

When the C plate 61 is disposed on the opposite side of the first liquid crystal cell 11A to the second liquid crystal cell 11B, the C plate 61 is preferably a positive C plate 61PC. When the C plate 61 is disposed on the opposite side of the second liquid crystal cell 11B from the first liquid crystal cell 11A, and the negative A plate 52NA is disposed adjacent to the incident side of the C plate 61, the C plate 61 is , negative C plate 61NC is preferable.

<Seventh configuration>
102 to 110 are examples of schematic cross-sectional views of an optical element having the seventh configuration according to the second modification of the first embodiment. As shown in FIGS. 102 to 110, in the optical element 10 of the seventh configuration, in the first configuration, the first A plate 51 is a positive A plate 51PA, and the second A plate 52 is a negative A plate 51PA. The plate 52NA further includes a first C plate 61 and a second C plate 62 arranged on the output side of the first C plate 61. The first C plate 61 is disposed on the opposite side of the first liquid crystal cell 11A to the second liquid crystal cell 11B, or on the opposite side of the second liquid crystal cell 11B to the first liquid crystal cell 11A, and The C plate 62 is arranged on the side of the second liquid crystal cell 11B opposite to the first liquid crystal cell 11A.

When the first C plate 61 is disposed on the opposite side of the first liquid crystal cell 11A to the second liquid crystal cell 11B, the first C plate 61 is preferably a positive C plate 61PC. The second C plate 62 is arranged on the opposite side of the second liquid crystal cell 11B from the first liquid crystal cell 11A, and the negative A plate 52NA is arranged adjacent to the incident side of the second C plate 62. In this case, the second C plate 62 is preferably a negative C plate 62NC.

When a plurality of C plates are arranged on the opposite side of the first liquid crystal cell 11A of the second liquid crystal cell 11B, it is preferable that the plurality of C plates are not adjacent to each other, and specifically, the plurality of C plates Preferably, at least one A plate is arranged in between.

<Eighth configuration>
111 to 117 are examples of schematic cross-sectional views of an optical element having the eighth configuration according to the second modification of the first embodiment. As shown in FIGS. 111 to 117, in the optical element 10 of the eighth configuration, in the first configuration, the first A plate 51 is a positive A plate 51PA, and the second A plate 52 is a negative A plate 51PA. The plate 52NA further includes a first C plate 61, a second C plate 62 disposed on the output side of the first C plate 61, and a second C plate 62 disposed on the output side of the second C plate 62. A third C plate 63 is provided. The first C plate 61 is disposed on the opposite side of the first liquid crystal cell 11A to the second liquid crystal cell 11B, or on the opposite side of the second liquid crystal cell 11B to the first liquid crystal cell 11A, and The C plate 62 and the third C plate 63 are arranged on the opposite side of the second liquid crystal cell 11B from the first liquid crystal cell 11A.

When the first C plate 61 is disposed on the opposite side of the first liquid crystal cell 11A to the second liquid crystal cell 11B, the first C plate 61 is preferably a positive C plate 61PC. A third C plate 63 is arranged on the opposite side of the second liquid crystal cell 11B from the first liquid crystal cell 11A, and a negative A plate 52NA is arranged adjacent to the incident side of the third C plate 63. In this case, the third C plate 63 is preferably a negative C plate 63NC.

When a plurality of C plates are arranged on the opposite side of the first liquid crystal cell 11A of the second liquid crystal cell 11B, it is preferable that the plurality of C plates are not adjacent to each other, and specifically, the plurality of C plates Preferably, at least one A plate is arranged in between.

<Ninth configuration>
118 to 119 are examples of schematic cross-sectional views of an optical element having the ninth configuration according to the second modification of the first embodiment. As shown in FIGS. 118 and 119, in the optical element 10 of the ninth configuration, in the first configuration, the first A plate 51 is a positive A plate 51PA, and the second A plate 52 is a negative A plate 51PA. The plate 52NA further includes a first C plate 61, a second C plate 62 disposed on the output side of the first C plate 61, and a second C plate 62 disposed on the output side of the second C plate 62. The third C-plate 63 and the fourth C-plate 64 are arranged on the output side of the third C-plate 63. The first C plate 61 is disposed on the opposite side of the first liquid crystal cell 11A to the second liquid crystal cell 11B, or on the opposite side of the second liquid crystal cell 11B to the first liquid crystal cell 11A, and The C plate 62, the third C plate 63, and the fourth C plate 64 are arranged on the opposite side of the second liquid crystal cell 11B from the first liquid crystal cell 11A.

When the first C plate 61 is disposed on the opposite side of the first liquid crystal cell 11A to the second liquid crystal cell 11B, the first C plate 61 is preferably a positive C plate 61PC. A fourth C plate 64 is arranged on the opposite side of the second liquid crystal cell 11B from the first liquid crystal cell 11A, and a negative A plate 52NA is arranged adjacent to the incident side of the fourth C plate 64. In this case, the fourth C plate 64 is preferably a negative C plate 64NC.

When a plurality of C plates are arranged on the opposite side of the first liquid crystal cell 11A of the second liquid crystal cell 11B, it is preferable that the plurality of C plates are not adjacent to each other, and specifically, the plurality of C plates Preferably, at least one A plate is arranged in between.

<Tenth configuration>
120 to 125 are examples of schematic cross-sectional views of an optical element having a tenth configuration according to the second modification of the first embodiment. As shown in FIGS. 120 to 125, in the optical element 10 of the tenth configuration, in the first configuration, the first A plate 51 is a negative A plate 51NA, and the second A plate 52 is a positive A plate 51NA. The plate 52PA further includes a C plate 61, and the C plate 61 is located on the side opposite to the second liquid crystal cell 11B of the first liquid crystal cell 11A, or on the side opposite to the first liquid crystal cell 11A of the second liquid crystal cell 11B. is placed on the opposite side.

When the C plate 61 is disposed on the opposite side of the first liquid crystal cell 11A to the second liquid crystal cell 11B, the C plate 61 is preferably a positive C plate 61PC. When the C plate 61 is arranged on the opposite side of the second liquid crystal cell 11B from the first liquid crystal cell 11A, and the positive A plate 52PA is arranged adjacent to the incident side of the C plate 61, the C plate 61 , preferably 61 PCs on a positive C plate.

<Eleventh configuration>
126 to 138 are examples of schematic cross-sectional views of an optical element having the eleventh configuration according to the second modification of the first embodiment. As shown in FIGS. 126 to 138, in the optical element 10 of the eleventh configuration, in the first configuration, the first A plate 51 is a negative A plate 51NA, and the second A plate 52 is a positive plate. The A-plate 52PA further includes a first C-plate 61 and a second C-plate 62 arranged on the output side of the first C-plate 61. The first C plate 61 is disposed on the opposite side of the first liquid crystal cell 11A to the second liquid crystal cell 11B, or on the opposite side of the second liquid crystal cell 11B to the first liquid crystal cell 11A, and The C plate 62 is arranged on the side of the second liquid crystal cell 11B opposite to the first liquid crystal cell 11A.

When the first C plate 61 is disposed on the opposite side of the first liquid crystal cell 11A to the second liquid crystal cell 11B, the first C plate 61 is preferably a positive C plate 61PC. The second C plate 62 is arranged on the opposite side of the second liquid crystal cell 11B from the first liquid crystal cell 11A, and the positive A plate 52PA is arranged adjacent to the incident side of the second C plate 62. In this case, the second C plate 62 is preferably a positive C plate 62PC.

When a plurality of C plates are arranged on the opposite side of the first liquid crystal cell 11A of the second liquid crystal cell 11B, it is preferable that the plurality of C plates are not adjacent to each other, and specifically, the plurality of C plates Preferably, at least one A plate is arranged in between.

<Twelfth configuration>
139 to 150 are examples of schematic cross-sectional views of an optical element having the twelfth configuration according to the second modification of the first embodiment. As shown in FIGS. 139 to 150, in the optical element 10 of the twelfth configuration, in the first configuration, the first A plate 51 is a negative A plate 51NA, and the second A plate 52 is a positive plate. A plate 52PA, which further includes a first C plate 61, a second C plate 62 disposed on the output side of the first C plate 61, and a second C plate 62 disposed on the output side of the second C plate 62. A third C plate 63 is provided. The first C plate 61 is disposed on the opposite side of the first liquid crystal cell 11A to the second liquid crystal cell 11B, or on the opposite side of the second liquid crystal cell 11B to the first liquid crystal cell 11A, and The C plate 62 and the third C plate 63 are arranged on the opposite side of the second liquid crystal cell 11B from the first liquid crystal cell 11A.

When the first C plate 61 is disposed on the opposite side of the first liquid crystal cell 11A to the second liquid crystal cell 11B, the first C plate 61 is preferably a positive C plate 61PC. A third C plate 63 is arranged on the opposite side of the second liquid crystal cell 11B from the first liquid crystal cell 11A, and a positive A plate 52PA is arranged adjacent to the incident side of the third C plate 63. In this case, the third C plate 63 is preferably a positive C plate 63PC.

When a plurality of C plates are arranged on the opposite side of the first liquid crystal cell 11A of the second liquid crystal cell 11B, it is preferable that the plurality of C plates are not adjacent to each other, and specifically, the plurality of C plates Preferably, at least one A plate is arranged in between.

<Thirteenth configuration>
151 to 154 are examples of schematic cross-sectional views of an optical element having a thirteenth configuration according to a second modification of the first embodiment. As shown in FIGS. 151 to 154, in the optical element 10 of the thirteenth configuration, in the first configuration, the first A plate 51 is a negative A plate 51NA, and the second A plate 52 is a positive plate. A plate 52PA, furthermore, a first C plate 61, a second C plate 62 disposed on the output side of the first C plate 61, and a second C plate 62 disposed on the output side of the second C plate 62. A third C plate 63 and a fourth C plate 64 arranged on the output side of the third C plate 63 are provided. The first C plate 61 is disposed on the opposite side of the first liquid crystal cell 11A to the second liquid crystal cell 11B, or on the opposite side of the second liquid crystal cell 11B to the first liquid crystal cell 11A, and The C plate 62, the third C plate 63, and the fourth C plate 64 are arranged on the opposite side of the second liquid crystal cell 11B from the first liquid crystal cell 11A.

When the first C plate 61 is disposed on the opposite side of the first liquid crystal cell 11A to the second liquid crystal cell 11B, the first C plate 61 is preferably a positive C plate 61PC. A fourth C plate 64 is arranged on the opposite side of the second liquid crystal cell 11B from the first liquid crystal cell 11A, and a positive A plate 52PA is arranged adjacent to the incident side of the fourth C plate 64. In this case, the fourth C plate 64 is preferably a positive C plate 64PC.

When a plurality of C plates are arranged on the opposite side of the first liquid crystal cell 11A of the second liquid crystal cell 11B, it is preferable that the plurality of C plates are not adjacent to each other, and specifically, the plurality of C plates Preferably, at least one A plate is arranged in between.

<Fourteenth configuration>
155 to 159 are examples of schematic cross-sectional views of an optical element having the fourteenth configuration according to the second modification of the first embodiment. As shown in FIGS. 155 to 159, in the optical element 10 of the fourteenth configuration, in the first configuration, the first A plate 51 is a negative A plate 51NA, and the second A plate 52 is a negative The A plate 52NA further includes a C plate 61, and the C plate 61 is located on the opposite side of the first liquid crystal cell 11A to the second liquid crystal cell 11B, or on the side opposite to the second liquid crystal cell 11B, or the first liquid crystal cell of the second liquid crystal cell 11B. It is located on the opposite side from 11A.

When the C plate 61 is disposed on the opposite side of the first liquid crystal cell 11A to the second liquid crystal cell 11B, the C plate 61 is preferably a positive C plate 61PC. When the C plate 61 is disposed on the opposite side of the second liquid crystal cell 11B from the first liquid crystal cell 11A, and the negative A plate 52NA is disposed adjacent to the incident side of the C plate 61, the C plate 61 is , negative C plate 61NC is preferable.

<Fifteenth configuration>
160 to 168 are examples of schematic cross-sectional views of an optical element having a fifteenth configuration according to a second modification of the first embodiment. As shown in FIGS. 160 to 168, in the optical element 10 having the fifteenth configuration, in the first configuration, the first A plate 51 is a negative A plate 51NA, and the second A plate 52 is a negative A plate 51NA. The A-plate 52NA further includes a first C-plate 61 and a second C-plate 62 arranged on the output side of the first C-plate 61. The first C plate 61 is disposed on the opposite side of the first liquid crystal cell 11A to the second liquid crystal cell 11B, or on the opposite side of the second liquid crystal cell 11B to the first liquid crystal cell 11A, and The C plate 62 is arranged on the side of the second liquid crystal cell 11B opposite to the first liquid crystal cell 11A.

When the first C plate 61 is disposed on the opposite side of the first liquid crystal cell 11A to the second liquid crystal cell 11B, the first C plate 61 is preferably a positive C plate 61PC. The second C plate 62 is arranged on the opposite side of the second liquid crystal cell 11B from the first liquid crystal cell 11A, and the negative A plate 52NA is arranged adjacent to the incident side of the second C plate 62. In this case, the second C plate 62 is preferably a negative C plate 62NC.

When a plurality of C plates are arranged on the opposite side of the first liquid crystal cell 11A of the second liquid crystal cell 11B, it is preferable that the plurality of C plates are not adjacent to each other, and specifically, the plurality of C plates Preferably, at least one A plate is arranged in between.

<Sixteenth configuration>
169 to 176 are examples of schematic cross-sectional views of an optical element having a sixteenth configuration according to a second modification of the first embodiment. As shown in FIGS. 169 to 176, in the optical element 10 having the sixteenth configuration, in the first configuration, the first A plate 51 is a negative A plate 51NA, and the second A plate 52 is a negative A plate 51NA. A plate 52NA, which further includes a first C plate 61, a second C plate 62 disposed on the output side of the first C plate 61, and a second C plate 62 disposed on the output side of the second C plate 62. A third C plate 63 is provided. The first C plate 61 is disposed on the opposite side of the first liquid crystal cell 11A to the second liquid crystal cell 11B, or on the opposite side of the second liquid crystal cell 11B to the first liquid crystal cell 11A, and The C plate 62 and the third C plate 63 are arranged on the opposite side of the second liquid crystal cell 11B from the first liquid crystal cell 11A.

When the first C plate 61 is disposed on the opposite side of the first liquid crystal cell 11A to the second liquid crystal cell 11B, the first C plate 61 is preferably a positive C plate 61PC. A third C plate 63 is arranged on the opposite side of the second liquid crystal cell 11B from the first liquid crystal cell 11A, and a negative A plate 52NA is arranged adjacent to the incident side of the third C plate 63. In this case, the third C plate 63 is preferably a negative C plate 63NC.

When a plurality of C plates are arranged on the opposite side of the first liquid crystal cell 11A of the second liquid crystal cell 11B, it is preferable that the plurality of C plates are not adjacent to each other, and specifically, the plurality of C plates Preferably, at least one A plate is arranged in between.

<Seventeenth configuration>
176 to 177 are examples of schematic cross-sectional views of an optical element having the seventeenth configuration according to the second modification of the first embodiment. As shown in FIGS. 176 and 177, in the optical element 10 having the seventeenth configuration, in the first configuration, the first A plate 51 is a negative A plate 51NA, and the second A plate 52 is a negative A plate 51NA. A plate 52NA, furthermore, a first C plate 61, a second C plate 62 disposed on the output side of the first C plate 61, and a second C plate 62 disposed on the output side of the second C plate 62. A third C plate 63 and a fourth C plate 64 arranged on the output side of the third C plate 63 are provided. The first C plate 61 is disposed on the opposite side of the first liquid crystal cell 11A to the second liquid crystal cell 11B, or on the opposite side of the second liquid crystal cell 11B to the first liquid crystal cell 11A, and The C plate 62, the third C plate 63, and the fourth C plate 64 are arranged on the opposite side of the second liquid crystal cell 11B from the first liquid crystal cell 11A.

When the first C plate 61 is disposed on the opposite side of the first liquid crystal cell 11A to the second liquid crystal cell 11B, the first C plate 61 is preferably a positive C plate 61PC. A fourth C plate 64 is arranged on the opposite side of the second liquid crystal cell 11B from the first liquid crystal cell 11A, and a negative A plate 52NA is arranged adjacent to the incident side of the fourth C plate 64. In this case, the fourth C plate 64 is preferably a negative C plate 64NC.

When a plurality of C plates are arranged on the opposite side of the first liquid crystal cell 11A of the second liquid crystal cell 11B, it is preferable that the plurality of C plates are not adjacent to each other, and specifically, the plurality of C plates Preferably, at least one A plate is arranged in between.

(Variation 3 of Embodiment 1)
In this modification, the optical element 10 of Embodiment 1 further includes a first retardation film and a second retardation film on the opposite side of the second liquid crystal cell 11B from the first liquid crystal cell 11A. The aspect will be explained.

FIG. 200 is a schematic cross-sectional view of an optical element according to Modification 3 of Embodiment 1. As shown in FIG. 200, the optical element 10 of this modification further includes a first retardation film 71 disposed on the opposite side of the second liquid crystal cell 11B to the first liquid crystal cell 11A, and a first A second retardation film 72 is provided on the opposite side of the second liquid crystal cell 11B of the retardation film 71. By adopting such an aspect, it is possible to realize a wide viewing angle.

It is preferable that the first retardation film 71 and the second retardation film 72 are biaxial films. The biaxial film preferably has a refractive index (nx, ny, nz) that satisfies the following (Formula N5) and (Formula N6).
nx>ny (Formula N5)
nz=(nx+ny)/2 (Formula N6)

The materials of the first retardation film 71 and the second retardation film 72 are not particularly limited, and examples include a stretched polymer film, a liquid crystal material with fixed orientation, a thin plate made of an inorganic material, etc. can be used.

The method of forming the first retardation film 71 and the second retardation film 72 is not particularly limited. When formed from a polymer film, for example, a solvent casting method, a melt extrusion method, etc. can be used. As long as the desired retardation is achieved, the film may be unstretched or may be stretched. The stretching method is not particularly limited, and in addition to the inter-roll tension stretching method, the inter-roll compression stretching method, the tenter horizontal uniaxial stretching method, the diagonal stretching method, the vertical and horizontal biaxial stretching method, stretching under the action of the shrinkage force of a heat-shrinkable film can be used. A special stretching method that performs this can be used. Furthermore, in the case of forming from a liquid crystal material, for example, a method of applying the liquid crystal material onto a base film that has been subjected to an alignment treatment and fixing the alignment can be used. As long as the desired retardation is expressed, there may be a method in which no special orientation treatment is performed on the base film, or a method in which the orientation is fixed, then peeled off from the base film and transferred to another film, etc.

The in-plane retardation Re of the first retardation film 71 at a wavelength of 550 nm is preferably 90 nm or more and 170 nm or less. The in-plane retardation of the first retardation film 71 at a wavelength of 450 nm relative to the in-plane retardation at a wavelength of 550 nm is preferably 1.0 times or more and 1.1 times or less. The in-plane retardation of the first retardation film 71 at a wavelength of 650 nm relative to the in-plane retardation at a wavelength of 550 nm is preferably 0.9 times or more and less than 1.0 times.

The in-plane retardation Re of the second retardation film 72 at a wavelength of 550 nm is preferably 40 nm or more and 210 nm or less. The in-plane retardation of the second retardation film 72 at a wavelength of 450 nm relative to the in-plane retardation at a wavelength of 550 nm is preferably 1.0 times or more and 1.1 times or less. The in-plane retardation of the second retardation film 72 at a wavelength of 650 nm relative to the in-plane retardation at a wavelength of 550 nm is preferably 0.9 times or more and less than 1.0 times.

The difference between the in-plane retardation Re of the first retardation film 71 and the in-plane retardation Re of the second retardation film 72 is preferably 0 nm or more and 10 nm or less. By adopting such an aspect, it becomes possible to configure the first retardation film 71 and the second retardation film 72 with equivalent films, and it is possible to realize a wide viewing angle more easily.

FIG. 201 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 Modification 3 of Embodiment 1. The azimuth angle of the slow axis 71A of the first retardation film 71 shown in FIG. 201 is preferably 50° or more and 60° or less. By adopting such an aspect, polarization modulation and polarization non-modulation can be switched over a wider band. The azimuth angle of the slow axis 72A of the second retardation film 72 is preferably 5° or more and 24° or less. By adopting such an aspect, polarization modulation and polarization non-modulation can be switched over a wider band.

(Embodiment 2)
In this embodiment, features unique to this embodiment will be mainly described, and descriptions of contents that overlap with the first embodiment and its modifications will be omitted. This embodiment is substantially the same as Embodiment 1 except that it does not include the negative C plate 12.

FIG. 10 is a schematic cross-sectional view of the optical element according to the second embodiment. In the first embodiment, the optical element 10 includes the negative C plate 12. However, as shown in FIG. 10, the optical element 10 does not need to include the negative C plate 12. By adopting such a mode, the optical element 10 can be manufactured thinly and at low cost.

(Embodiment 3)
In this embodiment, features unique to this embodiment will be mainly explained, and explanations of the above-described first embodiment, its modifications, and contents that overlap with the second embodiment will be omitted. This embodiment is substantially the same as Embodiment 1 except that the configurations of the first liquid crystal cell 11A and the second liquid crystal cell 11B are different.

FIG. 11 is a schematic cross-sectional view of an optical element according to Embodiment 3. FIG. 12 is a schematic cross-sectional view of a first liquid crystal cell and a second liquid crystal cell included in the optical element according to Embodiment 3. FIG. 13 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. FIG. 14 is a schematic cross-sectional view illustrating the first state of the optical element according to the third embodiment. FIG. 15 is a schematic cross-sectional view illustrating the second state of the optical element according to the third embodiment.

The first liquid crystal molecule 510 and the second liquid crystal molecule 610 included in the optical element 10 of this embodiment shown in FIGS. 11 to 15 are negative-type liquid crystal molecules with twisted orientation. Therefore, as shown in FIG. 14, when the first liquid crystal layer 500 is in a state where no voltage is applied and the second liquid crystal layer 600 is in a state where a voltage is applied, the first liquid crystal molecules 510 are vertically aligned, and , the first state in which the second liquid crystal molecules 610 are twistedly aligned can be realized. In the first state, the phase difference of the first liquid crystal cell 11A can be canceled by the negative C plate 12. Further, as shown in FIG. 15, when the first liquid crystal layer 500 is in a voltage applied state and the second liquid crystal layer 600 is in a no voltage applied state, the first liquid crystal molecules 510 are twistedly aligned, and , it is possible to realize a second state in which the second liquid crystal molecules 610 are vertically aligned. In the second state, the phase difference of the second liquid crystal cell 11B can be canceled by the negative C plate 12.

It is preferable that the first alignment film 41, the second alignment film 42, the third alignment film 43, and the fourth alignment film 44 are vertical alignment films.

(Embodiment 4)
In this embodiment, features unique to this embodiment will be mainly described, and descriptions of contents that overlap with the first embodiment, its modifications, and the second and third embodiments will be omitted. This embodiment is substantially the same as Embodiment 1 except that the configuration of the second liquid crystal cell 11B is different.

FIG. 16 is a schematic cross-sectional view of an optical element according to Embodiment 4. FIG. 17 is a schematic cross-sectional view of a first liquid crystal cell and a second liquid crystal cell included in the optical element according to Embodiment 4. FIG. 18 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 4. FIG. 19 is a schematic cross-sectional view illustrating the first state of the optical element according to the fourth embodiment. FIG. 20 is a schematic cross-sectional view illustrating the second state of the optical element according to the fourth embodiment.

The first liquid crystal molecule 510 included in the optical element 10 of this embodiment shown in FIGS. 16 to 20 is a twistedly oriented positive type liquid crystal molecule, and the second liquid crystal molecule 610 is a twistedly oriented negative type liquid crystal molecule. It is a liquid crystal molecule. Therefore, as shown in FIG. 19, when both the first liquid crystal layer 500 and the second liquid crystal layer 600 are in a voltage applied state, the first liquid crystal molecules 510 are vertically aligned, and the second liquid crystal molecules A first state in which 610 has a twisted orientation can be achieved. In the first state, the phase difference of the first liquid crystal cell 11A can be canceled by the negative C plate 12. Further, as shown in FIG. 20, when both the first liquid crystal layer 500 and the second liquid crystal layer 600 are in a state where no voltage is applied, the first liquid crystal molecules 510 are twistedly aligned, and the second liquid crystal A second state in which the molecules 610 are vertically aligned can be achieved. In the second state, the phase difference of the second liquid crystal cell 11B can be canceled by the negative C plate 12.

It is preferable that the first alignment film 41 and the second alignment film 42 are horizontal alignment films, and the third alignment film 43 and the fourth alignment film 44 are vertical alignment films.

(Embodiment 5)
In this embodiment, features unique to this embodiment will be mainly explained, and explanations of the content that overlaps with the first embodiment, its modifications, and the second to fourth embodiments will be omitted. In this embodiment, a variable focus element including the optical element (sHWP) of Embodiments 1 to 4 described above will be described. FIG. 21 is a schematic cross-sectional view of a variable focus element according to Embodiment 5. A variable focus element 30 of this embodiment shown in FIG. 21 includes an optical element 10 and a Pancharatnam Berry (PB) lens 20.

As described above, the optical element 10 of Embodiments 1 to 4 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.

FIG. 22 is an example of a schematic cross-sectional view of a PB lens included in the variable focus element according to the fifth embodiment. The PB lens 20 includes an optically anisotropic layer 700, as shown in FIG. For example, the PB lens 20 refracts incident light in a predetermined direction and transmits the circularly polarized light. Note that in FIG. 22, the incident light is left-handed circularly polarized light.

In the part shown in FIG. 22, the optically anisotropic layer 700 has three regions R0, R1, and R2 from the left side in FIG. 22, 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 700, the direction of the optical axis of the liquid crystal molecules 710 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 700, 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 700, 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 700 is as shown in FIG. 22 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. 22, the torsion angle φ _R2 in the thickness direction of region R2 of the optically anisotropic layer 700 is larger than the torsion angle φ _R1 in the thickness direction of 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. 22, 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.

In this way, in the PB lens 20 of this embodiment, in the in-plane region where the optically anisotropic layer has a large refraction, the incident light is transmitted through the layer having a large twist angle in the thickness direction and is refracted. On the other hand, in an in-plane region where the optically anisotropic layer has a small refraction, the incident light is transmitted through the layer having a small twist angle in the thickness direction and is refracted. That is, in the PB lens 20, by setting the torsion angle in the in-plane thickness direction according to the magnitude of refraction by the optically anisotropic layer, it is possible to brighten the transmitted light relative to the incident light. Therefore, according to the PB lens 20, the dependence of the amount of transmitted light within the plane on the refraction angle can be reduced.

The angle of refraction of light within the plane of the optically anisotropic layer 700 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 700 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. 22, one period Λ _R2 of the liquid crystal alignment pattern in the region R2 of the optically anisotropic layer 700 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 700 on the light incident side refracts light to a greater extent.

Therefore, by setting the in-plane torsion angle φ in the thickness direction for one period Λ of the target liquid crystal alignment pattern, the transmitted light refracted at different angles in different regions in the plane can be brightened. can do.

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 an optically anisotropic layer 700 formed using a liquid crystal composition containing liquid crystal molecules 710, and the optical anisotropic layer 700 has optical axes derived from the liquid crystal molecules that are oriented in a plane. has a liquid crystal alignment pattern that continuously rotates and changes along at least one of the directions, and has a region in which the optical axis is twisted and rotated in the thickness direction of the optically anisotropic layer 700. 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 defined as the length in which the direction of the optical axis derived from the liquid crystal molecules 710 rotates 180 degrees in the plane. preferable.

In the optically anisotropic layer 700, 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 arranged in the order of the length of one period. 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 700 has a region in which the twist angle in the thickness direction is 10° to 360°.

The optically anisotropic layer 700 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 710 in the liquid crystal alignment pattern changes while continuously rotating. , is preferably short.

The liquid crystal alignment pattern of the optically anisotropic layer 700 may be a concentric pattern extending from the inside to the outside in the one direction in which the direction of the optical axis derived from the liquid crystal molecules 710 changes while continuously rotating. preferable.

The PB lens 20 shown in FIG. 22 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 including a plurality of optically anisotropic layers 700, each of which has a different twist angle in the thickness direction of the optically anisotropic layer 700. It is preferable.

The PB lens 20 is a PB lens including a plurality of optically anisotropic layers 700, which have different torsion angles in the thickness direction of the optically anisotropic layers 700. It is preferable to have.

The PB lens 20 is a PB lens including a plurality of optically anisotropic layers 700, in which the optical axes derived from the liquid crystal molecules 710 are oriented in at least one in-plane direction. It is preferable to have a liquid crystal alignment pattern in which the directions of continuous rotation along the liquid crystal alignment pattern 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.

(Modification 1 of Embodiment 5)
In this modification, a variable focus element 30 in which the PB lens 20 of the fifth embodiment is placed inside the optical element 10 and is in-cell will be described. FIG. 23 is a schematic cross-sectional view of a variable focus element according to Modification 1 of Embodiment 5. FIG. 24 is an enlarged schematic cross-sectional view of a variable focus element according to Modification 1 of Embodiment 5. FIG. 25 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 Modification 1 of Embodiment 5.

The variable focus element 30 of this modification is, as shown in FIG. 23, 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. 23, the optical element 10 and the PB lens 20 are shown separately for convenience.

As shown in FIG. 24, the varifocal element 30 of this modification includes, more specifically, a second 1/4 wavelength film 14 and a first 1/4 wavelength film 14 in order from the incident side to the exit side. The wavelength film 13, the first substrate 100, the first liquid crystal layer 500, the second substrate 200, the third substrate 300, the second liquid crystal layer 600, the PB lens 20, and the fourth A substrate 400 is provided.

The variable focus element 30 may include a first alignment film 41 between the first substrate 100 and the first liquid crystal layer 500. Further, the variable focus element 30 may include a second alignment film 42 between the second substrate 200 and the first liquid crystal layer 500. Further, the variable focus element 30 may include a third alignment film 43 between the third substrate 300 and the second liquid crystal layer 600. Further, the variable focus element 30 may include a fourth alignment film 44 between the PB lens 20 and the second liquid crystal layer 600.

In this modification, the first liquid crystal cell 11A and the second liquid crystal cell 11B have the same configuration as in the first embodiment, and include a first alignment film 41, a second alignment film 42, and a third alignment film 43. And the fourth alignment film 44 is a horizontal alignment film.

As shown in FIG. 25, in this modification, the azimuth angle of the alignment direction 512A of the first liquid crystal molecules 512 on the second substrate 200 side in the second state is -9° or more and 7° or less, and The azimuth angle of the alignment direction 612A of the second liquid crystal molecules 612 on the fourth substrate 400 side in one state is preferably 85° or more and 96° or less. By adopting such an aspect, polarization modulation and polarization non-modulation can be switched over a wider band.

In this modification, the negative C plate 12 is not arranged between the first liquid crystal cell 11A and the second liquid crystal cell 11B, but the negative C plate 12 is not arranged between the first liquid crystal cell 11A and the second liquid crystal cell 11B. A negative C plate 12 may also be provided.

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 fourth substrate 400, and a film for forming a PB lens is formed. The PB lens 20 can be formed into an in-cell by performing an orientation process on the forming 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 alignment process for the PB lens forming film is performed by a plurality of alignment processes, and the directions of polarized light irradiated in the plurality of alignment processes are different from each other. The alignment treatment for the PB lens forming film is, for example, a first alignment treatment in which the PB lens forming film is aligned with polarized light with an azimuth angle of 0°, and a first alignment process in which the PB lens forming film is aligned with polarized light with an azimuth angle of 45°. A second alignment process in which the PB lens forming film is aligned with polarized light at an azimuth angle of 90°, and a third alignment process in which the PB lens forming film is aligned with polarized light at an azimuth angle of 135°. and a fourth alignment process that performs an alignment process.

FIG. 26 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 5. As shown in FIG. 26, 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 710 at the position of 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 retardation 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 is λ/2 (i.e., 275 nm). It is particularly preferable. Since the diffraction efficiency is expressed by the following (Equation 1), it takes the maximum value 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. 27 is a schematic cross-sectional view illustrating a detailed configuration of a variable focus element according to Modification 1 of Embodiment 5. As shown in FIG. 27, 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. has. It has the property of + (condensing) when right-handed circularly polarized light is incident, and - (diverging) when left-handed circularly polarized light is incident.

Table 1 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 the first modification of the fifth embodiment.

The F0 mode will be explained using Table 1 above. In this mode, all optical elements 10 are in the first 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 second 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 second 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. 28 above. FIG. 28 is a diagram illustrating the polarization state in the F-2.5 mode of the variable focus element according to Modification 1 of Embodiment 5. As shown in Table 1 and FIG. 28, 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 second modulated state. In this modified example, only three conditions are shown.

(Modification 2 of Embodiment 5)
In Embodiment 5 and Modification 1 of Embodiment 5, the embodiments include a film-like (in-cell polymer) PB lens, but the PB lens is a fluid liquid crystal layer, that is, it can be driven by voltage. It may be a liquid crystal layer. In this modification, a case will be described in which the PB lens is a liquid crystal layer that can be driven by voltage.

As in Embodiment 5 and Modification 1 of Embodiment 5, the polymer-like PB lens itself 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 the variable focus element that combines the sHWP and the passive PB lens as in the fifth embodiment and the first modification of the fifth embodiment, there is a binary switching between condensing and divergence, whereas in the variable focus element as in the fifth modification and the first modification of the fifth embodiment A variable focus element that combines an sHWP and an active PB lens 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 6)
In this embodiment, features unique to this embodiment will be mainly explained, and descriptions of contents that overlap with the above-described Embodiment 1 and its modifications, as well as Embodiments 2 to 5 and their modifications will be omitted. In this embodiment, a head mounted display including a variable focus element 30 will be described. FIG. 29 is a schematic cross-sectional view of a head mounted display according to Embodiment 6. FIG. 30 is a schematic perspective view showing an example of the appearance of the head mounted display according to the sixth embodiment.

As shown in FIGS. 29 and 30, 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 with reference to 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 first liquid crystal cell 11A and the second liquid crystal cell 11B were stacked in two layers, and a negative C plate 12 having a retardation Rth in the thickness direction of -110 nm was stacked between them. The first liquid crystal molecule 510 and the second liquid crystal molecule 610 were positive liquid crystal molecules, and had a refractive index anisotropy Δn=0.066. The first alignment film 41, the second alignment film 42, the third alignment film 43, and the fourth alignment film 44 were horizontal alignment films.

The azimuth angle of the alignment direction 511A of the first liquid crystal molecules 511 on the first substrate 100 side in the second state is 0°, and the alignment direction of the first liquid crystal molecules 512 on the second substrate 200 side in the second state The azimuth angle of 512A was 68°. Further, the azimuth angle of the alignment direction 611A of the second liquid crystal molecules 611 on the third substrate 300 side in the first state is 90°, and the azimuth angle of the second liquid crystal molecules 612 on the fourth substrate 400 side in the first state is 90°. The azimuth angle of the orientation direction 612A was 158°. Note that the orientation direction 511A of the first liquid crystal molecules 511 on the first substrate 100 side in the second state, the orientation direction 512A of the first liquid crystal molecules 512 on the second substrate 200 side in the second state, and the orientation direction 512A of the first liquid crystal molecules 512 on the second substrate 200 side in the second state, The alignment direction 611A of the second liquid crystal molecules 611 on the third substrate 300 side and the alignment direction 612A of the second liquid crystal molecules 612 on the fourth substrate 400 side in the first state are respectively the first alignment film. 41, the alignment directions 511A, 512A, 611A and 612A are the same as the alignment directions of the second alignment film 42, the third alignment film 43 and the fourth alignment film 44, respectively. It was determined from the alignment processing directions of the alignment film 41, the second alignment film 42, the third alignment film 43, and the fourth alignment film 44.

The first 1/4 wavelength film 13 had reverse wavelength dispersion characteristics, and the second 1/4 wavelength film 14 had flat wavelength dispersion characteristics. The slow axis 13A of the first quarter wavelength film 13 was 57.2°, and the slow axis 14A of the second quarter wavelength film 14 was 12.2°.

In the first state, a voltage was applied to the first liquid crystal layer 500 to drive it. The voltage applied to the first liquid crystal layer 500 in the first state is preferably as high as possible, and in this example, 20V was applied. Since the negative C plate 12 is designed so that the phase difference between the driven liquid crystal layer (first liquid crystal layer 500) and the negative C plate 12 is canceled, only the undriven liquid crystal layer (second liquid crystal layer 600) Now valid. Therefore, it was possible to realize a wide viewing angle and broadband sHWP.

In the second state, contrary to the first state, by applying a voltage to the second liquid crystal layer 600 and driving it, the liquid crystal layer (second liquid crystal layer 600) that was effective in the first state is changed. Since the liquid crystal layer rotated by 90 degrees (first liquid crystal layer 500) becomes effective, two 1/4 wavelength films (first 1/4 wavelength film 13 and second 1/4 wavelength film 14) are After passing through, the light became circularly polarized light having a polarization state opposite to that of the light that entered the optical element 10.

(Comparative example 1)
FIG. 31 is a schematic cross-sectional view of an optical element according to Comparative Example 1. An optical element 10R1 of Comparative Example 1 shown in FIG. 31 was manufactured. The optical element 10R1 of Comparative Example 1 was an optical element corresponding to the optical element of Comparative Form 1 described above. The optical element 10R1 of Comparative Example 1 includes, in order from the incident side to the output side, a 1/4 wavelength film 15R whose slow axis has an azimuth of 75°, a 1/4 wavelength film whose slow axis has an azimuth of 15°, and a 1/4 wavelength film 15R whose slow axis has an azimuth of 15°. A two-wavelength film 16R, a liquid crystal cell 11R1 including a 90° twisted TN liquid crystal layer 500R1, a half-wavelength film 17R whose slow axis has an azimuth of -75°, and a slow axis whose azimuth is -15°. It was equipped with a quarter-wavelength film 18R.

(Comparative example 2)
FIG. 32 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. 32 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 500R2 and a -70° twisted TN liquid crystal layer 500R3 were laminated in order from the incident side to the output side.

(Evaluation of Example 1, Comparative Example 1, and Comparative Example 2)
Regarding the optical elements (sHWP) of Example 1, Comparative Example 1, and Comparative Example 2, the Stokes parameter S3 of the emitted light when right-handed circularly polarized light (S3=+1) was incident was evaluated. In the Examples and Comparative Examples of this specification, unless otherwise specified, the Stokes parameter S3 of the light emitted when right-handed circularly polarized light (S3=+1) is incident is evaluated. FIG. 33 is a graph showing the relationship between the Stokes parameter S3 and the wavelength of emitted light when the optical elements according to Example 1, Comparative Example 1, and Comparative Example 2 are not modulated. FIG. 34 is a graph showing the relationship between the Stokes parameter S3 during modulation and the wavelength of emitted light for the optical elements according to Example 1, Comparative Example 1, and Comparative Example 2. As shown in FIGS. 33 and 34, in Example 1, |S3|≧0.9 could be achieved in the wavelength range of 450 nm to 650 nm both during modulation and during non-modulation.

FIG. 35 is a graph showing the relationship between the Stokes parameter S3 and the azimuth when the optical element according to Comparative Example 1 is not modulated, when the incident angle is set to 30°. FIG. 36 is a graph showing the relationship between the Stokes parameter S3 and the azimuth during modulation of the optical element according to Comparative Example 1 when the incident angle is set to 30°. FIG. 37 is a graph showing the relationship between the Stokes parameter S3 and the azimuth when the optical element according to Comparative Example 2 is not modulated, when the incident angle is set to 30°. FIG. 38 is a graph showing the relationship between the Stokes parameter S3 and the azimuth during modulation of the optical element according to Comparative Example 2 when the incident angle is set to 30°. FIG. 39 is a graph showing the relationship between the Stokes parameter S3 and the azimuth when the optical element according to Example 1 is not modulated, when the incident angle is set to 30°. FIG. 40 is a graph showing the relationship between the Stokes parameter S3 and the azimuth during modulation of the optical element according to Example 1 when the incident angle is set to 30°. 35 to 40 show evaluation results at wavelengths of 450 nm, 550 nm, and 650 nm.

As shown in FIGS. 35 and 36, in Comparative Example 1, |S3|≧0.9 could not be achieved both during modulation and during non-modulation. As shown in FIGS. 37 and 38, in Comparative Example 2, |S3|≧0.9 was generally achieved during modulation, but |S3|≧0.9 was not achieved during non-modulation. On the other hand, as shown in FIGS. 39 and 40, in Example 1, |S3|≧0.9 could be achieved in all directions in the range of 450 nm to 650 nm both during modulation and during non-modulation.

The viewing angle characteristics of the optical elements of Example 1, Comparative Example 1, and Comparative Example 2 during non-modulation and modulation were evaluated by simulation. The results are shown in FIG. FIG. 41 is a diagram showing simulation results of the viewing angle characteristics of the optical elements of Example 1, Comparative Example 1, and Comparative Example 2 during non-modulation and modulation.

In the graph for non-modulation in FIG. 41, 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 FIG. 41, in Example 1, it was found that the viewing angle was good for both non-modulation and modulation in the wavelength range of 450 nm to 650 nm. On the other hand, it was found that Comparative Example 1 had a good viewing angle when not modulated, but had a large wavelength dependence when modulated. It was found that Comparative Example 2 had a good viewing angle during modulation, but a poor viewing angle when not modulated.

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 preferable range is determined to be a range in which modulation and non-modulation of 90% or more can be achieved at an incident angle of 30° and a wavelength of 450 nm to 650 nm. In addition, in the graphs shown below, for the sake of simplicity, only data regarding the worst direction with an incident angle of 30° at wavelengths of 450 nm, 550 nm, and 650 nm are shown.

First, in order to examine the suitable range of the retardation Δnd of the first liquid crystal layer 500 in the second state at a wavelength of 550 nm and the retardation Δnd of the second liquid crystal layer 600 in the first state at a wavelength of 550 nm, an experiment was carried out. Stokes parameter S3 at the time of non-modulation with respect to the retardation in the first state of the second liquid crystal layer 600 included in the optical element 10 of Example 1, and the second state of the first liquid crystal layer 500 included in the optical element 10 of Example 1 The Stokes parameter S3 during modulation for the retardation was determined by simulation. FIG. 42 is a graph showing the Stokes parameter S3 at the time of non-modulation with respect to the retardation in the first state of the second liquid crystal layer included in the optical element of Example 1. FIG. 43 is a graph showing the Stokes parameter S3 at the time of modulation with respect to the retardation in the second state of the first liquid crystal layer included in the optical element of Example 1.

From FIG. 42, it was found that the retardation of the second liquid crystal layer 600 in the first state at a wavelength of 550 nm is preferably 210 nm or more and 260 nm or less. Moreover, from FIG. 43, it was found that the retardation of the first liquid crystal layer 500 in the second state at a wavelength of 550 nm is preferably 200 nm or more and 260 nm or less.

In order to study the suitable range of the twist angle of the first liquid crystal molecule 510 and the second liquid crystal molecule 610, the Stokes at the time of non-modulation with respect to the twist angle of the second liquid crystal molecule 610 included in the optical element 10 of Example 1 was used. The parameter S3 and the Stokes parameter S3 during modulation with respect to the twist angle of the first liquid crystal molecule 510 included in the optical element 10 of Example 1 were determined by simulation. FIG. 44 is a graph showing the unmodulated Stokes parameter S3 with respect to the twist angle of the second liquid crystal molecule included in the optical element of Example 1. FIG. 45 is a graph showing the Stokes parameter S3 during modulation with respect to the twist angle of the first liquid crystal molecule included in the optical element of Example 1.

From FIG. 44, it was found that the second liquid crystal molecules 610 in the first state (non-modulated) are preferably twisted at a twist angle of 64° or more and 74° or less. Further, from FIG. 45, it was found that the first liquid crystal molecules 510 in the second state (during modulation) are preferably twisted at a twist angle of 61° or more and 75° or less.

In order to study the preferable range of the pre-twist angle of the first liquid crystal molecule 510 and the second liquid crystal molecule 610, when the pre-twist angle of the second liquid crystal molecule 610 included in the optical element 10 of Example 1 is not modulated, The Stokes parameter S3 and the Stokes parameter S3 at the time of modulation with respect to the pre-twist angle of the first liquid crystal molecule 510 included in the optical element 10 of Example 1 were determined by simulation. FIG. 46 is a graph showing the non-modulated Stokes parameter S3 with respect to the pretwist angle of the second liquid crystal molecule included in the optical element of Example 1. FIG. 47 is a graph showing the Stokes parameter S3 during modulation with respect to the pretwist angle of the first liquid crystal molecule included in the optical element of Example 1. Here, the pre-twist angle is the azimuth angle of the alignment direction of liquid crystal molecules on the incident side substrate of each liquid crystal cell. Specifically, the pre-twist angle of the first liquid crystal molecules 510 is the azimuth angle of the alignment direction 511A of the first liquid crystal molecules 511 on the first substrate 100 side in the second state. Further, the pre-twist angle of the second liquid crystal molecules 610 is specifically the azimuth angle of the alignment direction 611A of the second liquid crystal molecules 611 on the third substrate 300 side in the first state.

From FIG. 46, the pre-twist angle of the second liquid crystal molecules 610, that is, the azimuth angle of the alignment direction 611A of the second liquid crystal molecules 611 on the third substrate 300 side in the first state is 85° or more and 96° or less. It was found that it is suitable. Further, from FIG. 47, the pre-twist angle of the first liquid crystal molecules 510, that is, the azimuth angle of the alignment direction 511A of the first liquid crystal molecules 511 on the first substrate 100 side in the second state is −9° or more, It has been found that the angle is preferably 7° or less.

From FIGS. 42 to 47, the optimum values of the retardation Δnd, twist angle and pre-twist angle of the liquid crystal layer are different between the first liquid crystal cell 11A and the second liquid crystal cell 11B, so liquid crystal cells of the same design are not necessarily stacked. It turns out there's no need to. That is, it was found that the first liquid crystal cell 11A does not have to have the same configuration as the second liquid crystal cell 11B.

In order to examine the suitable range of the azimuth angle of the slow axis of the reverse wavelength dispersion 1/4 wavelength film (first 1/4 wavelength film 13), the reverse wavelength dispersion The Stokes parameter S3 in non-modulation and modulation with respect to the azimuth angle of the slow axis of the quarter-wavelength film was determined by simulation. FIG. 48 is a graph showing the Stokes parameter S3 during non-modulation with respect to the azimuth of the slow axis of the quarter-wavelength film with reverse wavelength dispersion included in the optical element according to Example 1. FIG. 49 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 reverse wavelength dispersion included in the optical element according to Example 1. As shown in FIGS. 48 and 49, the azimuth angle of the slow axis of the reverse wavelength dispersion 1/4 wavelength film as the first 1/4 wavelength film 13 is preferably 52° or more and 60° or less. That's what I found out.

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 was determined by simulation. FIG. 50 is a graph showing the Stokes parameter S3 during 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. 51 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. As shown in FIGS. 50 and 51, it was found that the retardation of the reverse wavelength dispersion 1/4 wavelength film as the first 1/4 wavelength film 13 is preferably 90 nm or more and 170 nm or less.

In order to examine the suitable range of the azimuth angle of the slow axis of the flat wavelength dispersion 1/4 wavelength film (second 1/4 wavelength film 14), the flat wavelength dispersion The wavelength dispersion of the Stokes parameter S3 during non-modulation and modulation with respect to the azimuth angle of the slow axis of the quarter-wavelength film was determined by simulation. FIG. 52 is a graph showing the Stokes parameter S3 during non-modulation with respect to the azimuth angle of the slow axis of the flat wavelength dispersion quarter-wave film included in the optical element according to Example 1. FIG. 53 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. 52 and 53, the azimuth angle of the slow axis of the flat wavelength dispersion 1/4 wavelength film as the second 1/4 wavelength film 14 is preferably 8° or more and 18° or less. That's what I found out.

In order to study the suitable range of the retardation of the flat wavelength dispersion 1/4 wavelength film, the retardation of the flat wavelength dispersion 1/4 wavelength film included in the optical element 10 of Example 1 was measured in the non-modulated state and in the modulated state. The wavelength dispersion of the Stokes parameter S3 was determined by simulation. FIG. 54 is a graph showing the Stokes parameter S3 during non-modulation with respect to the phase difference of the flat wavelength dispersion quarter-wave film included in the optical element according to Example 1. FIG. 55 is a graph showing the Stokes parameter S3 during modulation with respect to the phase difference of the quarter-wavelength film with flat wavelength dispersion included in the optical element according to Example 1. As shown in FIGS. 54 and 55, it has been found that the retardation of the flat wavelength dispersion 1/4 wavelength film as the second 1/4 wavelength film 14 is preferably 120 nm or more and 150 nm or less. Ta.

(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 negative C plate 12 was not disposed.

The viewing angle characteristics of the optical elements of Example 1, Example 2, and Comparative Example 1 during non-modulation and modulation were evaluated by simulation. The results are shown in FIG. FIG. 56 is a diagram showing the simulation results of the viewing angle characteristics of the optical elements of Example 1, Example 2, and Comparative Example 1 during non-modulation and modulation.

In the graph for non-modulation in FIG. 56, 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 FIG. 56, it was found that Example 2 had a good viewing angle for both non-modulation and modulation in the wavelength range of 450 nm to 650 nm, although it was not as good as Example 1. The optical element 10 of Example 2 could be manufactured at low cost since the negative C plate 12 was not disposed, and the optical element 10 could be made thinner.

Regarding the optical element (sHWP) of Example 2, the Stokes parameter S3 of the emitted light when right-handed circularly polarized light (S3=+1) was incident was evaluated. FIG. 57 is a graph showing the relationship between the Stokes parameter S3 and the azimuth when the optical element according to Example 2 is not modulated, when the incident angle is set to 30°. FIG. 58 is a graph showing the relationship between the Stokes parameter S3 and the azimuth during modulation of the optical element according to Example 2 when the incident angle is set to 30°. 57 and 58 show evaluation results at wavelengths of 450 nm, 550 nm, and 650 nm. As shown in FIGS. 57 and 58, in Example 2, |S3|≧0.9 could be achieved in all directions in the wavelength range of 450 nm to 650 nm both during modulation and during non-modulation.

Here, including Example 1, a suitable range of the retardation Rth in the thickness direction of the negative C plate 12 was investigated. Specifically, for an optical element having the same configuration as the optical element of Example 1, the Stokes parameter S3 was determined by simulation when the retardation Rth in the thickness direction of the negative C plate 12 was −300 nm to 0 nm. Here, the retardation Rth in the thickness direction of the negative C plate 12 of 0 nm indicates an aspect in which the negative C plate 12 is not laminated, that is, the configuration of Example 2. The results are shown in FIGS. 59 and 60.

FIG. 59 is a graph showing the relationship between the Stokes parameter S3 in the non-modulated state of the optical element of the example and the retardation Rth in the thickness direction of the negative C plate. FIG. 60 is a graph showing the relationship between the Stokes parameter S3 during modulation of the optical element of the example and the retardation Rth in the thickness direction of the negative C plate. In FIG. 59 and FIG. 60, only data about the worst direction with an incident angle of 30° at wavelengths of 450 nm, 550 nm, and 650 nm are shown. From FIGS. 59 and 60, it was found that the retardation Rth in the thickness direction of the negative C plate 12 is preferably −220 nm or more and 0 nm or less.

(Example 3)
An optical element 10 of Example 3 having a configuration similar to that of Embodiment 3 was manufactured. Specifically, the first liquid crystal molecule 510 and the second liquid crystal molecule 610 are twist-oriented negative liquid crystal molecules (refractive index anisotropy Δn=0.079) with a chiral pitch of 15.7 μm, and The first alignment film 41, the second alignment film 42, the third alignment film 43, and the fourth alignment film 44 are vertical alignment films, and the first liquid crystal layer 500 on the first substrate 100 side has an azimuth angle of 0. (that is, the azimuth angle of the alignment direction 511A of the first liquid crystal molecules 511 on the first substrate 100 side in the second state is set to 90 degrees), and Except that a pretilt of 90° in the azimuth was given to the 300 side (that is, the azimuth angle of the alignment direction 611A of the second liquid crystal molecules 611 on the third substrate 300 side in the first state was set to 90°). The optical element 10 of Example 3 was produced in the same manner as Example 1.

In the first state, a voltage was applied to the second liquid crystal layer 600 to drive it. The voltage applied to the second liquid crystal layer 600 in the first state is preferably as high as possible, and in this example, 20V was applied. Since the negative C plate 12 is designed so that the phase difference between the liquid crystal layer that is not being driven (the first liquid crystal layer 500) and the negative C plate 12 is canceled, only the liquid crystal layer that is being driven (the second liquid crystal layer 600) is has become effective. Therefore, it was possible to realize a wide viewing angle and broadband sHWP.

In the second state, contrary to the first state, by applying a voltage to the first liquid crystal layer 500 and driving it, the liquid crystal layer (second liquid crystal layer 600) that was effective in the first state is changed. Since the liquid crystal layer rotated by 90 degrees (first liquid crystal layer 500) becomes effective, two 1/4 wavelength films (first 1/4 wavelength film 13 and second 1/4 wavelength film 14) are After passing through, the light became circularly polarized light having a polarization state opposite to that of the light that entered the optical element 10.

Regarding the optical element (sHWP) of Example 3, the Stokes parameter S3 of the emitted light when right-handed circularly polarized light (S3=+1) was incident was evaluated. FIG. 61 shows the Stokes parameter S3 and the wavelength of the emitted light in the non-modulated state of the optical elements according to Example 1, Example 3, Comparative Example 1, and Comparative Example 2 when the incident angle is set to 0°. It is a graph showing a relationship. FIG. 62 shows the relationship between the Stokes parameter S3 during modulation and the wavelength of the emitted light of the optical elements according to Example 1, Example 3, Comparative Example 1, and Comparative Example 2 when the incident angle is set to 0°. This is a graph showing. FIGS. 61 and 62 show modulation and non-modulation characteristics in the visible light region when the incident angle is set to 0°. As shown in FIGS. 61 and 62, in Example 3, |S3|≧0.9 could be achieved in the wavelength range of 450 nm to 650 nm both during modulation and during non-modulation.

FIG. 63 is a graph showing the relationship between the Stokes parameter S3 and the azimuth when the optical element according to Example 3 is not modulated, when the incident angle is set to 30°. FIG. 64 is a graph showing the relationship between the Stokes parameter S3 and the azimuth during modulation of the optical element according to Example 3 when the incident angle is set to 30°. FIGS. 63 and 64 show modulation and non-modulation characteristics at wavelengths of 450 nm, 550 nm, and 650 nm when the incident angle is set to 30°. As shown in FIGS. 63 and 64, in Example 3, |S3|≧0.9 could be achieved in all directions in the wavelength range of 450 nm to 650 nm both during modulation and during non-modulation.

(Example 4)
An optical element 10 of Example 4 having a configuration similar to that of Embodiment 4 was manufactured. Specifically, the optical element 10 of Example 4 was produced in the same manner as Example 1 except that the second liquid crystal cell 11B of Example 3 was used as the second liquid crystal cell 11B.

In the first state, voltage was applied to both the first liquid crystal layer 500 and the second liquid crystal layer 600 to drive them. The voltage applied to the first liquid crystal layer 500 and the second liquid crystal layer 600 in the first state is preferably as high as possible, and in this example, 20V was applied. Since the negative C plate 12 was designed so that the phase difference between the driven first liquid crystal layer 500 and the negative C plate 12 was canceled, only the driven second liquid crystal layer 600 became effective. Therefore, it was possible to realize a wide viewing angle and broadband sHWP.

Contrary to the first state, in the second state, by applying no voltage to either the first liquid crystal layer 500 or the second liquid crystal layer 600, the liquid crystal layer (the The second liquid crystal layer 600) is a liquid crystal layer rotated by 90 degrees (the first liquid crystal layer 500), so two 1/4 wavelength films (the first 1/4 wavelength film 13 and the second The light after passing through the 1/4 wavelength film 14) became circularly polarized light having a polarization state opposite to that of the light incident on the optical element 10.

Regarding the optical element (sHWP) of Example 4, the Stokes parameter S3 of the emitted light when right-handed circularly polarized light (S3=+1) was incident was evaluated. FIG. 65 is a graph showing the relationship between the Stokes parameter S3 and the wavelength of the emitted light when the optical elements according to Example 4, Comparative Example 1, and Comparative Example 2 are not modulated when the incident angle is set to 0°. It is. FIG. 66 is a graph showing the relationship between the Stokes parameter S3 during modulation and the wavelength of the emitted light for the optical elements according to Example 4, Comparative Example 1, and Comparative Example 2 when the incident angle is set to 0°. be. FIGS. 65 and 66 show modulation and non-modulation characteristics in the visible light region when the incident angle is set to 0°. As shown in FIGS. 65 and 66, in Example 4, |S3|≧0.9 could be achieved in the wavelength range of 450 nm to 650 nm both during modulation and during non-modulation.

FIG. 67 is a graph showing the relationship between the Stokes parameter S3 and the azimuth when the optical element according to Example 4 is not modulated when the incident angle is set to 30°. FIG. 68 is a graph showing the relationship between the Stokes parameter S3 and the azimuth during modulation of the optical element according to Example 4 when the incident angle is set to 30°. FIGS. 67 and 68 show modulation and non-modulation characteristics at wavelengths of 450 nm, 550 nm, and 650 nm when the incident angle is set to 30°. As shown in FIGS. 67 and 68, in Example 4, |S3|≧0.9 could be achieved in all directions in the wavelength range of 450 nm to 650 nm both during modulation and during non-modulation.

(Example 5)
A variable focus element 30 of Example 5 corresponding to Modification 1 of Embodiment 5 was manufactured. The first liquid crystal molecule 510 and the second liquid crystal molecule 610 were positive liquid crystal molecules, and had a refractive index anisotropy Δn=0.066. The first alignment film 41, the second alignment film 42, the third alignment film 43, and the fourth alignment film 44 were horizontal alignment films.

The azimuth angle of the alignment direction 512A of the first liquid crystal molecules 512 on the second substrate 200 side in the second state is 0°, and the alignment direction of the first liquid crystal molecules 511 on the first substrate 100 side in the second state The azimuth angle of 511A was 68°. Further, the azimuth angle of the alignment direction 612A of the second liquid crystal molecules 612 on the fourth substrate 400 side in the first state is 90°, and The azimuth angle of the orientation direction 611A was 158°.

The first 1/4 wavelength film 13 had reverse wavelength dispersion characteristics, and the second 1/4 wavelength film 14 had flat wavelength dispersion characteristics. The slow axis 13A of the first quarter wavelength film 13 was 57.2°, and the slow axis 14A of the second quarter wavelength film 14 was 12.2°.

Specifically, the variable focus element 30 of Example 5 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) is applied to the fourth substrate 400 of the second liquid crystal cell 11B to form a film for forming a PB lens. It was filmed.

FIG. 69 is a schematic diagram illustrating the first alignment process in the manufacturing process of the variable focus element according to Example 5. FIG. 70 is a schematic diagram illustrating the second alignment process in the manufacturing process of the variable focus element according to Example 5. FIG. 71 is a schematic diagram illustrating the third alignment process in the manufacturing process of the variable focus element according to Example 5. FIG. 72 is a schematic diagram illustrating the fourth alignment process in the manufacturing process of the variable focus element according to Example 5.

Next, the PB lens forming film provided on the fourth substrate 400 was subjected to alignment treatment. Specifically, as shown in FIG. 69, the PB lens forming film 900 was subjected to alignment treatment using a first photomask 810 with polarized light having an azimuth angle of 0°. Subsequently, as shown in FIG. 70, using a second photomask 820, the PB lens forming film 900 was subjected to alignment treatment with polarized light having an azimuth angle of 45°. Subsequently, as shown in FIG. 71, using a third photomask 830, the PB lens forming film 900 was subjected to alignment treatment with polarized light having an azimuth angle of 90°. Finally, as shown in FIG. 72, using a fourth photomask 840, the PB lens forming film 900 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 fourth substrate 400.

Using the laminate of the fourth substrate 400 and the PB lens 20, a second liquid crystal cell 11B was produced in the same manner as in Example 2, and a horizontally oriented first liquid crystal cell 11A and a horizontally oriented second liquid crystal cell 11B were fabricated in the same manner as in Example 2. Liquid crystal cells 11B were stacked. Thereafter, a 1/4 wavelength film with reverse wavelength dispersion is attached as the first 1/4 wavelength film 13 to the side of the first liquid crystal cell 11A opposite to the second liquid crystal cell 11B, and the second 1/4 wavelength film A 1/4 wavelength film with flat wavelength dispersion was attached as the wavelength film 14 to the side of the first 1/4 wavelength film 13 opposite to the first liquid crystal cell 11A to obtain the variable focus element 30 of Example 5. .

Here, in this embodiment, the incident light enters the sHWP before the PB lens 20 and switches between right-handed circularly polarized light and left-handed circularly polarized light, and the PB lens 20 condenses or diverges the light depending on the polarization state. Therefore, the second 1/4 wavelength film 14 and the first 1/4 wavelength film 13 were arranged closer to the incident side than the first liquid crystal layer 500 and the second liquid crystal layer 600. Therefore, the arrangement and axial orientation of each layer were different from those in Example 2.

The variable focus element 30 of Example 5 was able to switch between polarization modulation and non-polarization modulation over a wide band and wide viewing angle.

(Example 6)
An optical element 10 of Example 6 having the same configuration as Modification Example 1 of Embodiment 1 was manufactured. Specifically, a first positive C plate 19A having a retardation Rth in the thickness direction of 70 nm is placed on the opposite side of the first liquid crystal cell 11A to the second liquid crystal cell 11B, and the second liquid crystal cell 11B and A second positive C plate 19B having a retardation Rth in the thickness direction of 70 nm is arranged between the first 1/4 wavelength film 13, and the retardation Rth in the thickness direction of the negative C plate 12 is changed to -140 nm. The optical element 10 of Example 6 was produced in the same manner as Example 1 except for the above. The method of driving the optical element 10 was also the same as in Example 1.

Regarding the optical element (sHWP) of Example 6, the Stokes parameter S3 of the emitted light when right-handed circularly polarized light (S3=+1) was incident was evaluated. FIG. 73 is a graph showing the relationship between the Stokes parameter S3 and the wavelength of emitted light when the optical elements according to Example 6, Comparative Example 1, and Comparative Example 2 are not modulated when the incident angle is set to 0°. It is. FIG. 74 is a graph showing the relationship between the Stokes parameter S3 during modulation and the wavelength of the emitted light for the optical elements according to Example 6, Comparative Example 1, and Comparative Example 2 when the incident angle is set to 0°. be. FIGS. 73 and 74 show modulation and non-modulation characteristics in the visible light region when the incident angle is set to 0°. As shown in FIGS. 73 and 74, in Example 6, |S3|≧0.9 could be achieved in the wavelength range of 450 nm to 650 nm both during modulation and during non-modulation.

FIG. 75 is a graph showing the relationship between the Stokes parameter S3 and the azimuth when the optical element according to Example 6 is not modulated, when the incident angle is set to 30°. FIG. 76 is a graph showing the relationship between the Stokes parameter S3 and the azimuth during modulation of the optical element according to Example 6 when the incident angle is set to 30°. FIGS. 75 and 76 show modulation and non-modulation characteristics at wavelengths of 450 nm, 550 nm, and 650 nm when the incident angle is set to 30°. As shown in FIGS. 75 and 76, in Example 6, |S3|≧0.9 could be achieved in all directions in the wavelength range of 450 nm to 650 nm both during modulation and during non-modulation. Further, in Example 6, better characteristics than in Example 1 were obtained.

In order to examine the suitable range of the retardation Rth in the thickness direction of the first positive C plate 19A and the second positive C plate 19B, the optical element 10 of Example 6 was measured using an LCD-MASTER 1D manufactured by Shintech. Optical calculations were performed. In the following, based on the results obtained by simulation, a preferable range is determined to be a range in which modulation and non-modulation of 90% or more can be achieved at an incident angle of 30° and a wavelength of 450 nm to 650 nm. In addition, in the graphs shown below, for the sake of simplicity, only data regarding the worst direction with an incident angle of 30° at wavelengths of 450 nm, 550 nm, and 650 nm are shown.

FIG. 77 is a graph showing the Stokes parameter S3 during non-modulation with respect to the retardation Rth in the thickness direction of the first positive C plate included in the optical element of Example 6. FIG. 78 is a graph showing the Stokes parameter S3 during modulation with respect to the retardation Rth in the thickness direction of the first positive C plate included in the optical element of Example 6. From FIGS. 77 and 78, it was found that the retardation Rth in the thickness direction of the first positive C plate 19A is preferably 0 nm or more and 190 nm or less.

FIG. 79 is a graph showing the Stokes parameter S3 during non-modulation with respect to the retardation Rth in the thickness direction of the second positive C plate included in the optical element of Example 6. FIG. 80 is a graph showing the Stokes parameter S3 during modulation with respect to the retardation Rth in the thickness direction of the second positive C plate included in the optical element of Example 6. From FIGS. 79 and 80, it was found that the retardation Rth in the thickness direction of the second positive C plate 19B is preferably 0 nm or more and 220 nm or less.

(Example 7)
FIG. 178 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 Example 7. Among the optical elements 10 having the seventh configuration according to Modification Example 2 of Embodiment 1, an optical element 10 corresponding to FIG. 104 was manufactured. In the optical element of this example, the azimuth angle of the slow axis 51A of the first A plate 51 (positive A plate) shown in FIG. ) The azimuth angle of the slow axis 52A was 10.2°.

Re at a wavelength of 550 nm of the first A plate 51 was 140 nm, Re at a wavelength of 450 nm with respect to Re at a wavelength of 550 nm was 1.01, and Re at a wavelength of 650 nm with respect to Re at a wavelength of 550 nm was 0.99. Here, Re means in-plane phase difference (Rp).

Re at a wavelength of 550 nm of the second A plate 52 was 120 nm, Re at a wavelength of 450 nm with respect to Re at a wavelength of 550 nm was 1.08, and Re at a wavelength of 650 nm with respect to Re at a wavelength of 550 nm was 0.96.

The Rth of the first C plate 61 (positive C plate) at a wavelength of 550 nm is 75 nm, Re at a wavelength of 450 nm with respect to Re at a wavelength of 550 nm is 1.07, and Re at a wavelength of 650 nm with respect to Re at a wavelength of 550 nm is 0.97. Met.

The Rth of the second C plate 62 (negative C plate) at a wavelength of 550 nm is -12.5 nm, the Re at a wavelength of 450 nm with respect to Re at a wavelength of 550 nm is 1.01, and the Re at a wavelength of 650 nm with respect to Re at a wavelength of 550 nm is It was 0.99.

The Rth of the negative C plate 12 at a wavelength of 550 nm was 160 nm, Re at a wavelength of 450 nm with respect to Re at a wavelength of 550 nm was 1.01, and Re at a wavelength of 650 nm with respect to Re at a wavelength of 550 nm was 0.99.

The first liquid crystal cell 11A and the second liquid crystal cell 11B were manufactured as follows. A first solid electrode 120, a second solid electrode 220, and a third solid electrode 320 are provided on the first substrate 100, the second substrate 200, the third substrate 300, and the fourth substrate 400, respectively. And a fourth solid electrode 420 was formed. Furthermore, a horizontal alignment film was provided on each of the first substrate 100, second substrate 200, third substrate 300, and fourth substrate 400 on which solid electrodes were formed. Note that a pretilt may be imparted to these horizontal alignment films by subjecting them to a rubbing treatment or the like.

A first liquid crystal cell 11A was manufactured by providing a first liquid crystal layer 500 between a first substrate 100 and a second substrate 200, each provided with a solid electrode and a horizontal alignment film. A second liquid crystal cell 11B was manufactured by providing a second liquid crystal layer 600 between a third substrate 300 and a fourth substrate 400, each provided with a solid electrode and a horizontal alignment film. The first liquid crystal molecules 510 contained in the first liquid crystal layer 500 and the second liquid crystal molecules 610 contained in the second liquid crystal layer 600 were both positive liquid crystal molecules (Δn=0.070). . The thicknesses of the first liquid crystal layer 500 and the second liquid crystal layer 600 were both 3.4 μm.

In the second state, the azimuth angle of the alignment direction 511A of the first liquid crystal molecules 511 on the first substrate 100 side is 0°, and the azimuth of the alignment direction 512A of the first liquid crystal molecules 512 on the second substrate 200 side The angle was 68°. In the first state, the orientation angle 611A of the second liquid crystal molecules 611 on the third substrate 300 side is 90°, and the orientation angle 612A of the second liquid crystal molecules 612 on the fourth substrate 400 side is 158 degrees. It was °.

Regarding the optical element (sHWP) of Example 7, the Stokes parameter S3 of the emitted light when right-handed circularly polarized light (S3=+1) was incident was evaluated. FIG. 179 is a graph showing the relationship between the Stokes parameter S3 and the wavelength of the emitted light when the optical elements according to Examples 1 and 7 are not modulated. FIG. 180 is a graph showing the relationship between the Stokes parameter S3 during modulation and the wavelength of emitted light for the optical elements according to Examples 1 and 7. FIGS. 179 and 180 show modulation and non-modulation characteristics in the visible light region when the incident angle is set to 0°. As shown in FIGS. 179 and 180, in Example 7, as in Example 1, |S3|≧0.9 can be achieved in the wavelength range of 450 nm to 650 nm both during modulation and during non-modulation. Ta.

FIG. 181 is a graph showing the relationship between the Stokes parameter S3 and the azimuth when the optical element according to Example 1 is not modulated when the incident angle is set to 30°. FIG. 182 is a graph showing the relationship between the Stokes parameter S3 and the azimuth during modulation of the optical element according to Example 1 when the incident angle is set to 30°. FIG. 183 is a graph showing the relationship between the Stokes parameter S3 and the azimuth when the optical element according to Example 7 is not modulated when the incident angle is set to 30°. FIG. 184 is a graph showing the relationship between the Stokes parameter S3 and the azimuth during modulation of the optical element according to Example 7 when the incident angle is set to 30°. 181 to 184 show evaluation results at wavelengths of 450 nm, 550 nm, and 650 nm. Note that the range hatched in gray in the figure is a suitable range where |S3|≧0.9.

As shown in FIGS. 181 to 184, in Example 7 as well, |S3|≧0.9 could be achieved in all directions in the range of 450 nm to 650 nm both during modulation and during non-modulation. The characteristics of Example 7 were better than those of Example 1.

In order to consider the design of a suitable liquid crystal cell, optical calculations were performed on the optical element 10 of Example 7 using LCD-MASTER 1D manufactured by Shintech. In the following, based on the results obtained by simulation, a preferable range is determined to be a range in which modulation and non-modulation of 90% or more can be achieved at an incident angle of 30° and a wavelength of 450 nm to 650 nm. In addition, in the graphs shown below, for the sake of simplicity, only data regarding the worst direction with an incident angle of 30° at wavelengths of 450 nm, 550 nm, and 650 nm are shown.

First, in order to examine a suitable range of the retardation Rth in the thickness direction of the second C plate 62 (negative C plate), The Stokes parameter S3 during non-modulation with respect to the retardation Rth and the Stokes parameter S3 during modulation with respect to the retardation Rth in the thickness direction of the second C plate 62 included in the optical element 10 of Example 7 were determined by simulation. FIG. 185 is a graph showing the Stokes parameter S3 at the time of non-modulation with respect to the retardation Rth in the thickness direction of the second C plate included in the optical element of Example 7. FIG. 186 is a graph showing the Stokes parameter S3 during modulation with respect to the retardation Rth in the thickness direction of the second C plate included in the optical element of Example 7. As shown in FIGS. 185 and 186, it was found that the retardation Rth in the thickness direction of the second C plate 62 is preferably −170 nm or more and 0 nm or less.

In order to examine a suitable range of the retardation Rth in the thickness direction of the first C plate 61 (positive C plate), the retardation Rth in the thickness direction of the first C plate 61 included in the optical element 10 of Example 7 The Stokes parameter S3 at the time of non-modulation for , and the Stokes parameter S3 at the time of modulation for the retardation Rth in the thickness direction of the first C plate 61 included in the optical element 10 of Example 7 were determined by simulation. FIG. 187 is a graph showing the Stokes parameter S3 in the non-modulated state with respect to the retardation Rth in the thickness direction of the first C plate included in the optical element of Example 7. FIG. 188 is a graph showing the Stokes parameter S3 during modulation with respect to the retardation Rth in the thickness direction of the first C plate included in the optical element of Example 7. As shown in FIGS. 187 and 188, it was found that the retardation Rth in the thickness direction of the first C plate 61 is preferably 0 nm or more and 230 nm or less.

In order to examine a suitable range of the retardation Rth in the thickness direction of the negative C plate 12, the Stokes parameter S3 at the time of non-modulation for the negative C plate 12 included in the optical element 10 of Example 7 and the optical The Stokes parameter S3 during modulation with respect to the retardation Rth in the thickness direction of the negative C plate 12 included in the element 10 was determined by simulation. FIG. 189 is a graph showing the Stokes parameter S3 during non-modulation with respect to the retardation Rth in the thickness direction of the negative C plate included in the optical element of Example 7. FIG. 190 is a graph showing the Stokes parameter S3 during modulation with respect to the retardation Rth in the thickness direction of the negative C plate included in the optical element of Example 7. As shown in FIGS. 189 and 190, it was found that the retardation Rth in the thickness direction of the negative C plate 12 is preferably −350 nm or more and 0 nm or less.

In order to examine a suitable range of the in-plane retardation Re of the second A-plate 52 (negative A-plate), The Stokes parameter S3 during modulation and the Stokes parameter S3 during modulation with respect to the in-plane phase difference Re of the second A plate 52 included in the optical element 10 of Example 7 were determined by simulation. FIG. 191 is a graph showing the Stokes parameter S3 during non-modulation with respect to the in-plane phase difference Re of the second A plate included in the optical element of Example 7. FIG. 192 is a graph showing the Stokes parameter S3 during modulation with respect to the in-plane phase difference Re of the second A plate included in the optical element of Example 7. As shown in FIGS. 191 and 192, it was found that the in-plane retardation Re of the second A plate 52 is preferably 92 nm or more and 140 nm or less.

In order to consider a suitable range of the azimuth angle of the slow axis 52A of the second A plate 52, non-modulation with respect to the azimuth angle of the slow axis 52A of the second A plate 52 included in the optical element 10 of Example 7. The Stokes parameter S3 at the time of modulation and the Stokes parameter S3 at the time of modulation with respect to the azimuth of the slow axis 52A of the second A plate 52 included in the optical element 10 of Example 7 were determined by simulation. FIG. 193 is a graph showing the Stokes parameter S3 during non-modulation with respect to the azimuth angle of the slow axis of the second A plate included in the optical element of Example 7. FIG. 194 is a graph showing the Stokes parameter S3 during modulation with respect to the azimuth of the slow axis of the second A plate included in the optical element of Example 7. As shown in FIGS. 193 and 194, it was found that the azimuth angle of the slow axis 52A of the second A plate 52 is preferably 4° or more and 17° or less.

In order to examine a suitable range of the in-plane retardation Re of the first A plate 51 (positive A plate), The Stokes parameter S3 during modulation and the Stokes parameter S3 during modulation with respect to the in-plane phase difference Re of the first A plate 51 included in the optical element 10 of Example 7 were determined by simulation. FIG. 195 is a graph showing the Stokes parameter S3 during non-modulation with respect to the in-plane phase difference Re of the first A plate included in the optical element of Example 7. FIG. 196 is a graph showing the Stokes parameter S3 during modulation with respect to the in-plane phase difference Re of the first A plate included in the optical element of Example 7. As shown in FIGS. 195 and 196, it was found that the in-plane retardation Re of the first A plate 51 is preferably 70 nm or more and 220 nm or less.

In order to examine a suitable range of the azimuth angle of the slow axis 51A of the first A plate 51, non-modulation with respect to the azimuth angle of the slow axis 51A of the first A plate 51 included in the optical element 10 of Example 7. The Stokes parameter S3 at the time of modulation and the Stokes parameter S3 at the time of modulation with respect to the azimuth of the slow axis 51A of the first A plate 51 included in the optical element 10 of Example 7 were determined by simulation. FIG. 197 is a graph showing the Stokes parameter S3 during non-modulation with respect to the azimuth of the slow axis of the first A plate included in the optical element of Example 7. FIG. 198 is a graph showing the Stokes parameter S3 during modulation with respect to the azimuth of the slow axis of the first A plate included in the optical element of Example 7. As shown in FIGS. 197 and 198, it was found that the azimuth angle of the slow axis 51A of the first A plate 51 is preferably 47° or more and 52° or less.

FIG. 199 is a diagram explaining the polarization state. The horizontal axis of a graph such as FIG. 185 represents the phase difference or angle, and the vertical axis represents the value of "S3" among numerical values representing polarization called Stokes parameters. As shown on the Poincare sphere in FIG. 199, S3=+1 corresponds to the north pole on the Poincare sphere representing the polarization state, and represents right-handed circularly polarized light. S3=-1 corresponds to the south pole on the Poincaré sphere and represents left-handed circularly polarized light. That is, in this specification, the closer S3 is to ±1, the better the characteristics are.

Furthermore, since this specification describes the optical element 10 that switches between right-handed circularly polarized light and left-handed circularly polarized light, when right-handed circularly polarized light with S3=+1 enters as incident light, the incident light is There are two values: the light is emitted as right-handed circularly polarized light, or it is converted to left-handed circularly polarized light with S3=-1 and then emitted. Therefore, in this specification, a suitable range is discussed using two graphs, one for non-modulation and one for modulation.

Further, this specification aims at optical elements having a wide band and a wide viewing angle. Therefore, in order to examine whether it is possible to modulate all circularly polarized light (right-handed circularly polarized light in this specification) of RGB (red light, green light, and blue light) even in an oblique direction, the incident angle is set to 30°, S3 was plotted for wavelengths of 450 nm, 550 nm and 650 nm.

(Example 8)
An optical element of Example 8 having the same configuration as Modification Example 3 of Embodiment 1 was manufactured. The same first retardation film 71 and second retardation film 72 were used.

In the optical element of this example, the azimuth angle of the slow axis 71A of the first retardation film 71 (biaxial film) shown in FIG. The azimuth angle of the slow axis 72A of the film) was 15.8 degrees.

The in-plane retardation Re of the first retardation film 71 at a wavelength of 550 nm and the in-plane retardation Re of the second retardation film 72 at a wavelength of 550 nm were both 140 nm. The in-plane retardation at a wavelength of 450 nm relative to the in-plane retardation at a wavelength of 550 nm of the first retardation film 71 and the in-plane position at a wavelength of 450 nm relative to the in-plane retardation at a wavelength of 550 nm of the second retardation film 72 The phase difference was 1.01 in all cases. The in-plane retardation at a wavelength of 650 nm relative to the in-plane retardation at a wavelength of 550 nm of the first retardation film 71 and the in-plane position at a wavelength of 650 nm relative to the in-plane retardation at a wavelength of 550 nm of the second retardation film 72 The phase differences were all 0.99.

The first retardation film 71 and the second retardation film 72 satisfied the above (Formula N5) and (Formula N6).

The first liquid crystal cell 11A and the second liquid crystal cell 11B were manufactured as follows. A first solid electrode 120, a second solid electrode 220, and a third solid electrode 320 are provided on the first substrate 100, the second substrate 200, the third substrate 300, and the fourth substrate 400, respectively. And a fourth solid electrode 420 was formed. Furthermore, a horizontal alignment film was provided on each of the first substrate 100, second substrate 200, third substrate 300, and fourth substrate 400 on which solid electrodes were formed. Note that a pretilt may be imparted to these horizontal alignment films by subjecting them to a rubbing treatment or the like.

A first liquid crystal cell 11A was manufactured by providing a first liquid crystal layer 500 between a first substrate 100 and a second substrate 200, each provided with a solid electrode and a horizontal alignment film. A second liquid crystal cell 11B was manufactured by providing a second liquid crystal layer 600 between a third substrate 300 and a fourth substrate 400, each provided with a solid electrode and a horizontal alignment film. The first liquid crystal molecules 510 contained in the first liquid crystal layer 500 and the second liquid crystal molecules 610 contained in the second liquid crystal layer 600 were both positive liquid crystal molecules (Δn=0.070). . The thicknesses of the first liquid crystal layer 500 and the second liquid crystal layer 600 were both 3.4 μm.

In the second state, the azimuth angle of the alignment direction 511A of the first liquid crystal molecules 511 on the first substrate 100 side is 0°, and the azimuth of the alignment direction 512A of the first liquid crystal molecules 512 on the second substrate 200 side The angle was 68°. In the first state, the orientation angle 611A of the second liquid crystal molecules 611 on the third substrate 300 side is 90°, and the orientation angle 612A of the second liquid crystal molecules 612 on the fourth substrate 400 side is 158 degrees. It was °.

Regarding the optical element (sHWP) of Example 8, the Stokes parameter S3 of the emitted light when right-handed circularly polarized light (S3=+1) was incident was evaluated. FIG. 202 is a graph showing the relationship between the Stokes parameter S3 and the wavelength of the emitted light in the non-modulated state of the optical elements according to Example 8, Comparative Example 1, and Comparative Example 2. FIG. 203 is a graph showing the relationship between the Stokes parameter S3 during modulation and the wavelength of emitted light for the optical elements according to Example 8, Comparative Example 1, and Comparative Example 2. FIGS. 202 and 203 show modulation and non-modulation characteristics in the visible light region when the incident angle is set to 0°. As shown in FIGS. 202 and 203, in Example 8 as well, |S3|≧0.9 could be achieved in the wavelength range of 450 nm to 650 nm both during modulation and during non-modulation.

FIG. 204 is a graph showing the relationship between the Stokes parameter S3 and the azimuth when the optical element according to Example 8 is not modulated, when the incident angle is set to 30°. FIG. 205 is a graph showing the relationship between the Stokes parameter S3 and the azimuth during modulation of the optical element according to Example 8 when the incident angle is set to 30°. 204 and 205 show evaluation results at wavelengths of 450 nm, 550 nm, and 650 nm. Note that the range hatched in gray in the figure is a suitable range where |S3|≧0.9.

As shown in FIGS. 204 and 205, in Example 8 as well, |S3|≧0.9 could be achieved in all directions in the range of 450 nm to 650 nm both during modulation and during non-modulation.

In the optical element 10 of Example 8, a wide viewing angle could be achieved by using the same biaxial film as the first retardation film 71 and the second retardation film 72. Such optical elements can be manufactured at low cost. In addition, since the number of films can be reduced, it is considered to be advantageous in making the film thinner.

1: Head mounted display 1P: Display panel 10, 10R1, 10R2: Optical elements 11A, 11B, 11R1: Liquid crystal cell 12, 61NC, 62NC, 63NC, 64NC: Negative C plate 13, 14, 15R, 18R: 1/4 wavelength Films 13A, 14A, 51A, 52A, 71A, 72A: Slow axis 16R, 17R: 1/2 wavelength film 19A, 19B, 61PC, 62PC, 63PC, 64PC: Positive C plate 20, 20A1, 20A2, 20A3: Panchala Tonamberry (PB) lenses 30, 30A, 30B: Variable focus element 40: Retardation plates 41, 42, 43, 44: Alignment films 51, 52: A plates 51NA, 52NA: Negative A plates 51PA, 52PA: Positive A plates 61, 62, 63, 64: C plate 71, 72: Retardation film 100, 200, 300, 400: Substrate 110, 210, 310, 410: Support substrate 120, 220, 320, 420: Solid electrode 500, 600 : Liquid crystal layers 500R1, 500R2, 500R3: TN liquid crystal layers 510, 511, 512, 610, 611, 612, 710: Liquid crystal molecules 511A, 512A, 611A, 612A: Orientation direction 700: Optical anisotropic layers 810, 820, 830 , 840: Photomask 900: PB lens forming film LC0, LC1, LC2: Left circularly polarized light R0, R1, R2: Region U: User

Claims (20)

a first substrate, a first liquid crystal layer containing a first liquid crystal molecule, a second substrate, a third substrate, a second liquid crystal layer containing a second liquid crystal molecule, and a fourth substrate. and a substrate, in order,
The first substrate, the first liquid crystal layer, and the second substrate constitute a first liquid crystal cell,
The third substrate, the second liquid crystal layer, and the fourth substrate constitute a second liquid crystal cell,
The first liquid crystal cell has a first electrode for applying a voltage to the first liquid crystal layer on at least one of the first substrate and the second substrate,
The second liquid crystal cell has a second electrode for applying a voltage to the second liquid crystal layer on at least one of the third substrate and the fourth substrate,
The first electrode and the second electrode are
a first state in which the second liquid crystal molecules are twistedly aligned and the first liquid crystal molecules are vertically aligned; and a first state in which the first liquid crystal molecules are twistedly aligned and the second liquid crystal molecules are vertically aligned. It is arranged so that it can be switched between the second state and
The azimuth angle of the alignment direction of the second liquid crystal molecules on the third substrate side in the first state and the azimuth angle of the alignment direction of the second liquid crystal molecules on the fourth substrate side in the first state are , respectively, the azimuthal angle of the alignment direction of the first liquid crystal molecules on the first substrate side in the second state and the alignment direction of the first liquid crystal molecules on the second substrate side in the second state, respectively. An optical element characterized in that the azimuth angle is a quarter turn in the same direction. The optical element according to claim 1, further comprising a negative C plate between the first liquid crystal cell and the second liquid crystal cell. 3. The optical element according to claim 2, wherein the retardation Rth in the thickness direction of the negative C plate is -220 nm or more and 0 nm or less. The retardation of the first liquid crystal layer in the second state at a wavelength of 550 nm is 200 nm or more and 260 nm or less,
4. The optical element according to claim 1, wherein the retardation of the second liquid crystal layer in the first state at a wavelength of 550 nm is 210 nm or more and 260 nm or less. 4. The optical element according to claim 1, wherein the first liquid crystal cell does not have the same configuration as the second liquid crystal cell. The first liquid crystal molecules in the second state are twisted oriented at a twist angle of 61° or more and 75° or less,
4. The optical element according to claim 1, wherein the second liquid crystal molecules in the first state are twisted at a twist angle of 64° or more and 74° or less. The azimuth angle of the alignment direction of the first liquid crystal molecules on the first substrate side in the second state is −9° or more and 7° or less,
4. An azimuth angle of the alignment direction of the second liquid crystal molecules on the third substrate side in the first state is 85° or more and 96° or less. optical element. Further, a quarter-wavelength film is provided on a side of the first liquid crystal cell opposite to the second liquid crystal cell, or on a side of the second liquid crystal cell opposite to the first liquid crystal cell. The optical element according to any one of claims 1 to 3. 9. The optical element according to claim 8, wherein the quarter wavelength film has reverse wavelength dispersion characteristics. 9. The optical element according to claim 8, wherein the in-plane retardation at a wavelength of 450 nm of the quarter-wavelength film is 0.7 times or more and 1 time or less relative to the in-plane retardation at a wavelength of 550 nm. 9. The optical element according to claim 8, wherein the quarter-wavelength film has an in-plane retardation at a wavelength of 650 nm that is 1 to 1.3 times the in-plane retardation at a wavelength of 550 nm. The optical element according to claim 8, wherein the azimuth angle of the slow axis of the quarter-wavelength film is 52° or more and 60° or less. 9. The optical element according to claim 8, wherein the quarter-wavelength film has an in-plane retardation of 90 nm or more and 170 nm or less at a wavelength of 550 nm. The quarter wavelength film is a first quarter wavelength film,
9. A second quarter-wavelength film is further provided on a side of the first quarter-wavelength film opposite to the first liquid crystal cell and the second liquid crystal cell. optical element. 15. The optical element according to claim 14, wherein the second quarter-wavelength film has flat wavelength dispersion characteristics. 15. The optical element according to claim 14, wherein the azimuth angle of the slow axis of the second quarter-wavelength film is 8 degrees or more and 18 degrees or less. 15. The optical element according to claim 14, wherein the second quarter-wavelength film has an in-plane retardation of 120 nm or more and 150 nm or less at a wavelength of 550 nm. A variable focus element comprising the optical element according to any one of claims 1 to 3 and a Pancharatnam Berry lens. 19. The variable focus element of claim 18, wherein the Pancharatnam Berry lens is disposed within the optical element. A head mounted display comprising the variable focus element according to claim 18.

Images