JP2000066024A - Optical element and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to selectively scatter polarized light in an optical axis direction by dispersing grains which are isotropic in refractive index and are transparent into a transparent medium having double refractiveness. SOLUTION: The isotropic grains 12 which are isotropic in the refractive index and are transparent are dispersed into the transparent double refractive medium 11 having the double refractiveness. The double refractive medium 11 is a double refractive resin or double refractive thin film, etc., and is composed by polymerizing a high-polymer material or liquid crystals. The isotropic grains 12 are solid particles of a one component system, such as, for example, glass beads, and are the liquid drops of an isotropic liquid, such as, for example, glycerol, the liquid drops of the liquid crystals, etc. The structure formed by dispersing the isotropic particles 12 into the double refractive medium 11 is obtd. in the manner described above, by which the operation to scatter the specific polarized light component without electric fields is made possible. The diameter of the grains 12 to be dispersed is preferably set at about a fraction of 1 to about 10 times the wavelength of the light; for example, the diameter is set from 0.1 micron to about several microns and is more adequately set at 0.5 micron.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical element capable of scattering a specific polarization component without an electric field and a method for manufacturing the same, and is suitable for use as a scattering plate having polarization selectivity.

[0002]

2. Description of the Related Art A conventional method for producing an optical element using a polymerizable liquid crystal is constituted by mixing a small amount of a photopolymerizable liquid crystal in a liquid crystal and irradiating the mixture with light. Rumiko, Yutaka Wake, Susumu Sato (Akita University Mine):
“Characteristics of Reverse Mode in UV-Carryable Liquid Crystal Matrix / Nematic Liquid Crystal Composite Cell” IDY96
-50 pp. 137 to 142]. In this method, a dilute net composed of a polymer liquid crystal is formed in a liquid crystal, and scattering depending on polarization can be obtained by applying an electric field.

[0003]

However, in the conventional technique of providing a dilute net made of a polymer liquid crystal in a liquid crystal and applying an electric field to the net to obtain polarization-dependent scattering, the following problems arise. is there. Since the liquid crystal region is continuous, the scattering region and the non-scattering region cannot be separated with high resolution. Without applying an electric field, a scattering plate having polarization dependence could not be realized. It was difficult to control the direction of the scattered light.

[0004]

In order to solve the above-mentioned problems, the invention of an optical element according to claim 1 disperses transparent particles having an isotropic refractive index in a transparent medium having birefringence. It is characterized by having made it.

[0005] The invention of an optical element according to claim 2 is to disperse particles having a refractive index anisotropy in a transparent medium having a birefringence and to adjust the optical axis direction of the refractive index to the optical axis of the medium. A birefringent particle or a birefringent droplet in a direction different from the axis is dispersed.

According to a third aspect of the invention, there is provided the optical element according to the first or second aspect, wherein the transparent particles having an isotropic refractive index are made of one of solid particles, fluid, and liquid crystal. It is characterized by becoming.

The invention of an optical element according to claim 4 is characterized in that liquid crystal droplets are dispersed in a transparent medium having orientation.

According to a fifth aspect of the present invention, in the optical element according to the first or second aspect, the birefringent medium is a polymer liquid crystal.

According to a sixth aspect of the present invention, in the optical element according to the fourth aspect, the alignment medium is a polymer liquid crystal.

The invention of an optical element according to claim 7 is the optical element according to claims 1 to 6, wherein the diameter of the dispersed particles is:
It is characterized in that it is about one-seventh to ten times the wavelength of light.

The invention of an optical element according to claim 8 is the optical element according to claim 1 or 2, wherein the orientation axis of the medium is inclined at a finite angle from the medium surface.

According to a ninth aspect of the present invention, in the optical element according to the fourth aspect, the optical axis of the medium is inclined at a finite angle from the medium surface.

The invention of an optical element according to claim 10 is the optical element according to any one of claims 1 to 9, wherein when the main refractive index of the medium and the main refractive index of the dispersed particles are compared, one or two sets are obtained. It is characterized by being equal or close to a value that does not cause light scattering by vibrating dipoles in the main refractive index direction.

[0014] The invention of an optical element according to claim 11 is characterized in that the optical element according to claims 1 to 10 is sandwiched between electrodes, and at least one of the electrodes is transparent.

According to a twelfth aspect of the invention, there is provided a method for manufacturing an optical element, wherein a mixture of a photopolymerizable liquid crystal and a non-polymerizable liquid is irradiated with speckle light of a laser beam.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below, but the present invention is not limited to these embodiments.

FIG. 1 is a schematic diagram for explaining the operation of the device of the present invention. As shown in FIG. 1, the optical element of the present invention
This is a transparent birefringent medium 11 having a birefringent transparent birefringent medium 11 in which transparent isotropic particles 12 having an isotropic refractive index are dispersed. Here, the birefringent medium 11 is a birefringent resin, a birefringent thin film, or the like, and is formed by polymerizing a polymer material or a liquid crystal. The isotropic particles 12 are, for example, one-component solid particles such as glass beads, droplets of an isotropic liquid such as glycerin, or liquid crystal droplets.
Therefore, like the optical element of the present invention, the birefringent medium 11
By taking a structure in which the isotropic particles 12 are dispersed therein, an operation of scattering a specific polarization component without an electric field becomes possible. It is preferable that the diameter of the dispersed particles 12 is set to a fraction of the wavelength of light to about 10 times.
It is preferably from 0.1 micron to several microns, more preferably 0.5 micron.

Hereinafter, the operation of the optical element of the present invention will be described.
This will be described with reference to FIG. For convenience, dispersed particles 1
Reference numeral 1 denotes an isotropic particle, and the number is one.

As shown in FIG. 1, when light generally enters a birefringent medium 11 which is a transparent object, the electric field induces an oscillating dipole 13.
Since the vibration dipoles 13 are uniformly induced therein, scattering by the individual vibration dipoles 13 does not occur. Next, as shown in FIG. 1, when there is one isotropic particle 12, for example, when the ordinary refractive index of the birefringent medium 11 is equal to the refractive index of the isotropic particle 12, An index difference occurs between the birefringent medium 11 and the isotropic particles 12 in the optical axis direction X.

Here, similarly induced vibration dipole 13
In consideration of the above, the size of the vibration dipole 14 in the optical axis direction X differs only in the portion of the isotropic particle 12. That is, when viewed relatively, this is equivalent to the presence of the vibrating dipole 14 corresponding to the difference in the refractive index at the place where the particles exist. The scattering cross section of the relatively induced vibration dipole 14 exists only for polarized light in the optical axis direction X, and the scattered light mainly occurs in a direction perpendicular to the dipole. Accordingly, a scattering member that can selectively scatter polarized light in the optical axis direction X can be realized. Since the polarization of the scattered light is parallel to the optical axis direction X and the main component of the scattering is perpendicular to the optical axis, the scattering direction can be controlled by arbitrarily tilting the optical axis direction X.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below.
The present invention is not limited to this.

Embodiment 1 FIG. 2 is a schematic view showing an optical element according to Embodiment 1 of the present invention. As shown in FIG.
The optical element 20 according to the first embodiment includes an isotropic particle 2 having a particle diameter of several microns and an isotropic refractive index in a birefringent medium 21.
2 is dispersed. That is, the optical element according to the present embodiment uses a polymer liquid crystal as the birefringent medium 21 and, as the isotropic particles 22, disperses isotropic spheres such as glass beads, for example. For example, it can be realized by sandwiching between substrates having an orientation, such as a rubbed glass plate 24 having an orientation film 23 such as polyimide.

At this time, if the orientation direction of the glass plate 24 as a substrate is oriented so as to constitute an anti-parallel cell, good characteristics can be obtained. This is because, when the anti-parallel alignment is used, the liquid crystal molecules of the high-molecular liquid crystal used as the birefringent medium 21 are uniformly aligned. This is because such characteristics can be obtained.

Although the polymer liquid crystal is not particularly limited in the present invention, for example, “UCL-00”
1 "(trade name: manufactured by Roddick Co., Ltd.) by using a polymerizable photopolymerizable liquid crystal, sandwiching it between substrates such as a glass plate 24 and the like, and then polymerizing to obtain a polymer liquid crystal. A stronger structure can be realized.

A stable structure can be realized by using a highly viscous liquid crystal (viscosity: several Pa · s) such as a smectic liquid crystal as a polymer liquid crystal.

For example, a birefringent medium 21 can be obtained by using a material such as an optical glass (for example, “BK7”) having substantially the same refractive index in the uniaxial direction of the polymerizable liquid crystal as glass beads as the isotropic particles 22. By scattering light in the direction of the optical axis and transmitting a polarization component perpendicular to the light, a polarization diffusion plate was realized.

Second Embodiment FIG. 3 is a schematic view showing an optical element according to a second embodiment. FIG. 4 is a schematic view illustrating a method for manufacturing an optical element. FIG. 5 is a schematic view showing an element sandwiched between electrodes. As shown in FIG. 3, the optical element 30 of the second embodiment
Is constituted by dispersing a birefringent liquid droplet such as a liquid crystal as a particle 32 in a birefringent medium 31.

The optical element 30 according to the second embodiment can be manufactured by the following method as an example. FIG. 4 is a schematic view showing a method for producing the optical element of the present invention. A rubbed glass plate 3 having an alignment film 32 such as polyimide, for example, is prepared by mixing a liquid mixture 35, which is a fluid prepared by mixing and dissolving a photopolymerizable liquid crystal A and a non-polymerizable liquid B.
It is sandwiched between oriented substrates such as 4. In this state, at a temperature at which the liquid mixture 35 exhibits liquid crystallinity, the object 3 having a rough surface
6 is irradiated with speckle light 39 obtained by irradiating a laser light 38 from a laser light source 37. Then, polymerization of the photopolymerizable liquid crystal A occurs in a region where the light intensity in the speckle light 39 due to the scattered light is high, and the non-polymerizable liquid B concentrates in a region where the light intensity is low. By directly polymerizing, as shown in FIG. 3, the non-polymerizable liquid crystal B was concentrated and the isotropic particles 32 were dispersed in the medium 31 composed of the polymer liquid crystal formed by polymerizing the polymerizable liquid crystal A. The structure was realized.

At this time, if the rubbing direction of the glass plate 34 is set to an anti-parallel positional relationship, good polarization characteristics can be obtained. This is because when the anti-parallel alignment is used, the liquid crystal molecules are uniformly aligned, so that the polarization on the transmission side is not scattered due to the disorder of the alignment direction, so that good characteristics can be obtained.

Since the speckle size changes by appropriately controlling the roughness of the rough surface of the object 36 having a rough surface, the particle size of the formed isotropic particles 32 can be arbitrarily controlled. It is.

This manufacturing method can be applied to a general method of producing a polymer-dispersed liquid crystal by a photo-induced phase separation method, and a polymer liquid crystal having a controlled droplet diameter can be produced.

As shown in FIG. 5, FIG.
Is applied between the electrodes 41, 41 inserted between the alignment film 33 and the glass plate 34 to apply an electric field to change the alignment direction of the non-polymerizable liquid crystal B in the droplets as the particles 32. By doing so, the refractive index of the droplet as the granule 32 is made different from the refractive index in the optical axis direction of the birefringent medium 31 which is a film made of the polymerizable liquid crystal (UV cured liquid crystal) A. Can be. As a result, the birefringent medium 31
The optical element 40 capable of strongly scattering the polarized light component in the optical axis direction of the optical element in comparison with other polarized light components can be realized.

That is, as in the present embodiment, high resolution is realized by forming each of the particles 32 composed of the region of the non-polymerizable liquid crystal B into an independent discontinuous capsule structure.

Further, by using a liquid crystal having a different refractive index, for example, having an extraordinary refractive index larger than that of the medium 32, as the non-polymerizable liquid crystal B of the liquid droplets serving as the particles 32, the polarized light can be obtained without applying an electric field or the like. An element that operates as a diffusion plate can be realized.

The optical element 21 of the first embodiment can be formed by heating this optical element and causing the non-polymerizable liquid crystal B in the droplets as the particles 32 to transition to the isotropic phase.

Third Embodiment FIG. 6 is a schematic view showing an optical element according to a third embodiment of the present invention. The optical element 50 of this embodiment has a structure in which liquid crystals are dispersed as particles 52 in a medium 51 having an orientation such as a stretched film. In the present optical element 50, the medium 51 itself has almost no birefringence, but orientation occurs because the fibers of the film are aligned in one direction by stretching. When the liquid crystal as the particles 52 is dispersed in this film, a state in which the orientation directions of the dispersed liquid crystal are uniform is obtained. Here, for example, when the refractive index of the liquid crystal in the uniaxial direction is made to match the refractive index of the film, an element that scatters polarized light in the optical axis direction and transmits perpendicular polarized light can be realized.

In general, the liquid crystal as the particles 52 may be dispersed in the thin film as the medium 51 and then stretched.
For example, in the case where the thin film as the medium 51 is a porous body, it can be produced by stretching and then impregnating the liquid crystal as the granules 52 in the pores.

Embodiment 4 FIG. 7 is a schematic view showing an optical element according to Embodiment 4 of the present invention. As shown in FIG. 7, the optical element 60 according to the present embodiment is composed of a film 61 made of polymerized liquid crystal A, which is a polymerizable birefringent medium.
Is tilted with respect to the glass plate 34 with respect to the optical axis direction X.
Are dispersed. Here, the non-polymerizable fluid as the particles 62 in the present embodiment may be, for example, glycerin, but is not limited thereto. For example, assuming that the refractive index of the fluid that is the particle 62 is substantially equal to the refractive index in the direction perpendicular to the optical axis of the thin film that is the medium 61, the direction of the dipole induced by the incident light serving as the source of scattered light Is parallel to the optical axis, the direction of the scattered light is limited to the direction perpendicular to the optical axis. In this element,
Because the optical axis X is inclined, the glass plate 3
4 can generate scattered light in a specific direction that is not perpendicular.

In the present invention, scattered light is generated in a specific direction by tilting the optical axis of the recording medium 61 from the medium surface at a finite angle (for example, about 45 ° in the vertical direction when the surface of the glass plate 34 is set as a reference plane). Can be done.

Embodiment 5 FIG. 8 is a schematic view showing an optical element according to Embodiment 5 of the present invention. As shown in FIG. 8, the optical axis X direction of the birefringent thin film of the polymerizable liquid crystal A as the birefringent medium 71 is inclined with respect to the glass plate 34, and the non-polymerizable It has a structure in which liquid crystal B is dispersed. That is, the configuration of the optical element 70 of this embodiment is the same as that of the optical element of FIG. 5, but the direction of the optical axis X is oblique. For example, the extraordinary refractive index of the non-polymerizable liquid crystal B is larger than that of the thin film as the medium 71,
Assuming that the ordinary refractive indices are substantially equal to each other, the direction of the dipole induced by the incident light, which is the source of the scattered light, changes following the alignment direction of the liquid crystal. It changes with the change of. That is, the electrode 4
A scattering plate whose scattering direction changes due to the electric field generated by 1 can be realized. By making the optical anisotropy of the polymerizable liquid crystal A of the medium smaller than that of the non-polymerizable liquid crystal B in the thin film droplets, it is possible to suppress a change in intensity during polarization.

Further, instead of the thin film which is the birefringent medium 62 as in this embodiment, an isotropically oriented thin film whose orientation is inclined may be used.

[0042]

According to the present invention, transparent particles having an isotropic refractive index are dispersed in a transparent medium having birefringence to selectively scatter polarized light in the optical axis direction. A scattering member which can be realized can be realized.

Since the polarization of the scattered light is parallel to the optical axis direction and the main component of the scattering is perpendicular to the optical axis, the scattering direction can be controlled by arbitrarily tilting the optical axis direction.

Further, high resolution can be realized by making the liquid crystal region discontinuous.

Further, by dispersing liquid crystal droplets in an oriented medium, it becomes possible to provide a polarizing diffuser in a scattering state without an electric field.

Further, the degree of scattering is improved by controlling the diameter of the particles / droplets.

The scattering direction can be controlled by tilting the orientation axis or the optical axis. In particular, by performing this with an element in which liquid crystal droplets are dispersed, an element whose scattering direction can be changed by applying an electric field can be realized.

Further, by making one or more principal refractive indices match between the medium and the dispersed particles, the difference in the degree of scattering by polarized light can be increased.

Further, by irradiating speckle light having a spatial intensity distribution, polymerization of the photopolymerizable liquid crystal occurs in a region where the light intensity in the speckle light is large, and in a region where the light intensity is small. Since the non-polymerizable liquid is concentrated, the polymer liquid crystal is polymerized in a medium made of polymer liquid crystal,
A structure in which non-polymerizable liquid crystals are concentrated and isotropic particles are dispersed can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing the operation of an optical element according to the present invention.

FIG. 2 is a schematic diagram of an optical element of Example 1.

FIG. 3 is a schematic view of an optical element according to a second embodiment.

FIG. 4 is a view illustrating a method for manufacturing an optical element of Example 2.

FIG. 5 is a schematic diagram of an optical element sandwiched between electrodes of Example 2.

FIG. 6 is a drawing illustrating a method for manufacturing the optical element of Example 3.

FIG. 7 is a drawing illustrating a method for manufacturing the optical element of Example 4.

FIG. 8 is a view illustrating a method for manufacturing the optical element of Example 5.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Birefringent medium 12 Isotropic particle 13 Vibrating dipole X Optical axis direction 14 Vibrating dipole 20 Optical element 21 Birefringent medium 22 Isotropic particle 23 Orientation film 24 Glass plate 30 Optical element 31 Birefringence Medium 32 Particles 35 Mixed liquid 36 Object with rough surface 37 Laser light source 38 Laser light 39 Speckle light 40 Optical element 41 Electrode 50 Optical element 51 Medium 52 Particle 60 Optical element 61 Medium 62 Particle 70 Optical element 71 Medium 72 grains

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Katojo Uehira 3-19-2 Nishishinjuku, Shinjuku-ku, Tokyo F-term in Japan Telegraph and Telephone Corporation 2H042 BA02 BA20 2H049 BA25 BA42 BA44 BA47 BC04 BC06 2H079 AA02 AA12 BA02 CA24 DA08 2H089 HA02 HA03 JA03 QA16 TA04 TA17 UA09

Claims (12)

[Claims] 1. An optical element characterized in that transparent particles having an isotropic refractive index are dispersed in a transparent medium having birefringence. 2. A birefringent transparent medium having a refractive index anisotropy dispersed therein and a birefringent optical axis having a refractive index in a direction different from the optical axis of the medium. An optical element characterized by dispersing particles. 3. The optical element according to claim 1, wherein the transparent particles having an isotropic refractive index are made of one of solid particles, fluid, and liquid crystal. 4. An optical element comprising liquid crystal droplets dispersed in a transparent medium having an orientation. 5. The optical element according to claim 1, wherein the birefringent medium is a polymer liquid crystal. 6. The optical element according to claim 3, wherein the orientation medium is a polymer liquid crystal. 7. The optical element according to claim 1, wherein the diameter of the dispersed particles is about several tenths to ten times the wavelength of light. 8. The optical element according to claim 1, wherein an orientation axis of the medium is inclined at a finite angle from a medium surface. 9. The optical element according to claim 4, wherein an optical axis of the medium is inclined at a finite angle from a medium surface. 10. The optical element according to claim 1, wherein when the main refractive index of the medium and the main refractive index of the dispersed droplets or particles are compared, one or two sets of equal values are obtained. An optical element having a value close to a value that does not cause scattering of light by vibrating dipoles in a refractive index direction. 11. An optical element, wherein the optical element according to claim 1 is sandwiched between electrodes, and at least one of the electrodes is transparent. 12. A method for manufacturing an optical element, comprising irradiating a mixture of a photopolymerizable liquid crystal and a non-polymerizable liquid with speckle light of laser light.