JP3329565B2 - Liquid crystal light modulator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal light modulator for modulating light intensity by using a liquid crystal, and more particularly to a liquid crystal light modulator for a display requiring a memory property and a high speed. .

[0002]

2. Description of the Related Art An optical modulator can be realized by applying an electro-optic effect of a liquid crystal, which changes an alignment state of liquid crystal molecules by applying an electric field to the liquid crystal. Liquid crystal light modulators operate at a lower voltage than crystals that exhibit other electro-optic effects and can be made relatively inexpensively at a relatively large area. .

As one of such liquid crystal optical modulators, a ferroelectric liquid crystal having a spontaneous polarization and exhibiting a chiral smectic C phase is filled in a narrow gap (usually 3 μm or less) to change the alignment state of liquid crystal molecules. There is a stabilized surface stabilized ferroelectric liquid crystal. In this case, the liquid crystal molecules have two stable alignment states inclining from the alignment processing direction of the alignment film by a tilt angle inherent to the liquid crystal material (preferably about 22.5 °) while keeping the liquid crystal molecule horizontal. This liquid crystal light modulator is useful for displays because it has a memory function (binary) that is indispensable for improving luminance and a high-speed response. However, since this liquid crystal light modulator has a bistable operation, it is difficult to display a halftone. As a method of overcoming this, there is an area gradation method for dividing a binary liquid crystal region and realizing halftones according to the area ratio. So far, the following elements have been proposed as methods for obtaining the area gradation method.

Conventional Example 1 As shown in FIG. 6, a synthetic resin 3 in which spheroidal ferroelectric liquid crystal droplets 1 are dispersed is sandwiched between transparent electrodes 4A and 4B. Devices whose light transmittance is controlled by size (Reference: HS Kitzerow, H. Molsen
and G. Hepple, Applied Physics Letters, Vol. 60, N
o.25, pp.3093-3095). Conventional Example 2 As shown in FIG. 7, microspheres (TiO ₂ )
Is dispersed in the SiO alignment films 2A and 2A.
An element whose light transmittance is controlled by the magnitude of the voltage of the drive power supply 15 and is sandwiched between the transparent electrodes 4A and 4B to which B is attached (references: A. Yasuda, K. Nito, YY Bao, H. Takanis)
hi and NAClark, 4th International Conference on
Ferroelectric Liquid Crystals (FLC-93) Digest, N
oP-137, pp.351-352). Conventional Example 3 As shown in FIG. 8, a ferroelectric liquid crystal 1 is interposed between transparent electrodes 4A and 4B to which ultra-thin alignment films 17A and 17B (polyimide, about 2 nm thick) formed by the Langmuir-Blodgett method are attached. , A drive power supply 15 is connected via a diode 18 and a variable electric resistor 19, and the light transmittance is controlled by the resistance value of the electric resistor 19 (documents: Munehiro Kimura, Hiromi Maeda, CM. Gomez, Shunsuke Kobayashi,
IEICE Electronics Display Research Group, No.EID 89-
43, pp.13-18).

[0005]

PROBLEMS TO BE SOLVED BY THE INVENTION
And 3 each divide the ferroelectric liquid crystal 1,
Although halftone can be obtained by domaining, it has the following problems. In the device of Conventional Example 1, the ferroelectric liquid crystal 1 is deformed from a spherical shape to a spheroidal shape by shifting the two substrates 5A and 5B, and the liquid crystal 1 is aligned. A decrease in transmittance due to a decrease in contrast and light scattering is inevitable. In the device of Conventional Example 2, the microspheres 16 tend to agglomerate, making it difficult to produce a uniform device that is uniformly dispersed. In addition, the microspheres 16 floating in the ferroelectric liquid crystal 1 move with time, Stability due to change becomes a problem. In the device of Conventional Example 3, since the size of the liquid crystal domain cannot be freely controlled, it is difficult to improve the resolution by miniaturizing the domain.

Accordingly, an object of the present invention is to solve the above-mentioned problems and to provide a liquid crystal light having a halftone memory function and excellent in contrast, light transmittance, resolution, in-plane uniformity and stability. A modulator is not provided.

[0007]

In order to achieve this object, a liquid crystal optical modulator according to the present invention comprises a ferroelectric liquid crystal having spontaneous polarization and exhibiting a chiral smectic C phase and a fine liquid crystal having a thickness smaller than the wavelength of incident light. Liquid crystal-resin composite made of a synthetic resin having a three-dimensional network shape, the alignment film sandwiching the liquid crystal-resin composite, and aligning liquid crystal molecules in the alignment treatment direction of the alignment film; A transparent electrode sandwiching the alignment film, and a polarizing plate in which the polarization directions substantially sandwiching the liquid crystal / resin composite, the alignment film and the transparent electrode are orthogonal to each other,
A voltage application means for applying a voltage to the transparent electrode, and by changing the polarity and level of the voltage applied to the transparent electrode, a liquid crystal domain showing a transparent alignment and a liquid crystal domain showing an opaque alignment. Can be arbitrarily changed to perform light modulation with an arbitrary desired intensity.

Further, in an embodiment of the present invention, a fine mesh-like synthetic resin having a shape elongated in the alignment treatment direction of the alignment film is provided.
Since the ferroelectric liquid crystal is dispersed in the ferroelectric liquid crystal, the orientation of the ferroelectric liquid crystal is not disturbed, and a high contrast is obtained.
To solve the problem of the element). In addition, since the thickness of the resin fibers forming the mesh is extremely fine below the wavelength of the incident light, light scattering does not occur and light transmittance does not decrease (the problem of the element of Conventional Example 1 is solved). Further, the synthetic resin is bonded in a mesh form, does not change with time, and has high stability (Conventional Example 2).
To solve the problem of the element). Since the network-like synthetic resin is formed uniformly, high in-plane uniformity is obtained (the problem of the element of Conventional Example 2 is solved). Further, the size of the mesh of the synthetic resin can be easily controlled by controlling the speed of resin formation, so that a high-resolution element can be manufactured (Conventional Example 3).
To solve the problem of the element).

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the accompanying drawings. Configuration of the Embodiment FIG. 1 shows a cross-sectional view of a schematic configuration of an embodiment of a liquid crystal light modulator according to the present invention. In the liquid crystal light modulator of the present embodiment, the ferroelectric liquid crystal 1 showing a chiral smectic C phase is used.
, A network-like synthetic resin 3 extending in the alignment direction of the alignment film 2A is dispersed therein, and the liquid crystal 1 and the resin 3 are sandwiched between the alignment films 2A and 2B attached on the transparent electrodes 4A and 4B. Arrange. Further, two transparent electrodes 4A and 4B are attached on glass substrates 5A and 5B, and are connected via lead wire 6 and switch 7 to three driving DC voltage sources 8A, 8B and 8C.
Connected to either The incident light 9 is polarized in the major axis direction of the liquid crystal molecules by the polarizing plate 10A, and then enters from one glass substrate 5A, and the polarization state is controlled by the liquid crystal / resin composite 11 composed of the liquid crystal 1 and the synthetic resin 3. After being transmitted through the polarizing plate 10B on the emission side, the light becomes the emission light 12. The polarization directions of the two polarizing plates 10A and 10B are orthogonal to each other, and the alignment directions of the two alignment films 2A and 2B are parallel. Furthermore, the polarization direction of the polarizing plate 10A is inclined by the tilt angle of the liquid crystal molecules with respect to the alignment processing directions of the alignment films 2A and 2B. The periphery of the two glass substrates 5A and 5B is firmly fixed by a sealing resin 13.

The liquid crystal 1 is finely divided by the network synthetic resin 3 to form fine domains. In addition, synthetic resin 3
Are connected in a network and have high stability without causing aging. The liquid crystal / resin composite 11 composed of the liquid crystal 1 and the synthetic resin 3 is prepared by mixing the constituent materials of the liquid crystal 1 and the synthetic resin 3 into a homogeneous solvent while heating, and then performing photo-curing, heat-curing, and reaction curing. Is used to cure only the three components of the synthetic resin to precipitate and aggregate the liquid crystal 1.
At this time, the content of the resin 3 in the liquid crystal / resin composite was reduced to 10%.
In the following, the molecules (monomer) of the resin material are arranged together with the liquid crystal molecules in the alignment processing direction of the alignment films 2A and 2B at a high temperature at which the liquid crystal 1 exhibits a nematic phase in which the spontaneous polarization is lost, and the resin material is cured Thus, it is possible to form the mesh resin 3 having a shape extending in the alignment processing direction of the alignment films 2A and 2B. Even when the liquid crystal 1 returns to room temperature at which the liquid crystal 1 exhibits the chiral smectic C phase, the network resin 3 does not disturb the alignment of the liquid crystal 1 and can maintain a high contrast ratio. In addition, the thickness of the synthetic resin fiber 3 forming the mesh is smaller than the wavelength, so that a high light transmittance is exhibited without causing light scattering. The size of the mesh of the synthetic resin 3 can be easily controlled by the curing speed of the synthetic resin 3. Further, the resolution of the liquid crystal light modulator can be increased by forming the fine network synthetic resin 3. Further, if the forming speed of the synthetic resin 3 is controlled uniformly, the in-plane uniformity can be obtained because the mesh resin 3 is formed uniformly.

In order to largely control the polarization state of the incident light, the refractive index anisotropy Δn of the liquid crystal 1 (= the extraordinary light refractive index ne−
A higher ordinary light refractive index no) is advantageous. for that reason,
The liquid crystal 1 includes a Schiff base ferroelectric liquid crystal having a large refractive index anisotropy, an azo ferroelectric liquid crystal, an azoxy ferroelectric liquid crystal, a biphenyl ferroelectric liquid crystal, an ester ferroelectric liquid crystal, and phenylpyrimidine. A system ferroelectric liquid crystal or the like is suitable. Further, when the ferroelectric liquid crystal 1 having a large spontaneous polarization is used, high-speed response and low-voltage driving can be performed.

As the synthetic resin 3, a transparent acrylic resin, epoxy resin, urethane resin, or a copolymer thereof is most suitable. The alignment film 2A is rubbing alignment treated polyimide resin, polyvinyl alcohol film, oblique vapor deposited SiO, SiO ₂ or, are suitable, such as polyimide film of ultra-thin film formed by the Langmuir-Blodgett method . Note that it is also possible to configure the composite 11 by slightly tilting (pretilt angle) the liquid crystal molecules from the surfaces of the alignment films 2A and 2B. In addition, the liquid crystal molecules are
In the case of a structure (chevron structure) in which the molecules are slightly inclined in the opposite direction on the planes A and 2B and the molecular orientation is bent inside the liquid crystal,
This method is effective.

In this example, which was produced as an example, CS-1014 (refractive index anisotropy Δn = 0.15) was used as the ferroelectric liquid crystal 1 having a chiral smectic C phase. Further, as the synthetic resin 3, an ultraviolet-curable acrylic / urethane copolymer (NOA-65 manufactured by Norland Products)
, Refractive index ne = 1.524).

The manufacturing method is as follows. First, a polyimide film 2A (50 nm thick) is spin-coated on a glass substrate 5 with a transparent electrode 4A (In ₂ O ₃ : Sn, thickness 72 nm).
A (3 mm thick blue plate glass). Further, as an alignment treatment, the polyimide film 2A is rubbed in one direction (rubbing direction) with a fine rayon brush (rubbing treatment). The peripheral portions of the two glass substrates 5A and 5B provided with the alignment films 2A and 2B manufactured by such a method are bonded together with a sealing adhesive 13 containing a 2 μm spherical spacer.
In this case, the rubbing directions of the two alignment films 2A and 2B are as follows.
Parallel.

Next, the liquid crystal 1 and the synthetic resin 3 are heated to 100 ° C. and mixed to form a homogeneous solution. This homogeneous solution is filled with a gap (about 2 μm) between the alignment films 2A and 2B.
While maintaining the temperature at 100 ° C. Further, it is cooled to 75 ° C. showing a nematic phase, and irradiated with ultraviolet light (wavelength 365 nm) having an intensity of 40 mW / cm ² through a glass substrate 5A.
The network resin 3 is formed. Then, it is cooled slowly to room temperature.

The effective area of the liquid crystal light modulator according to the present embodiment, which is experimentally manufactured by such a method, is 20 × 20 mm ² . In order to obtain a practical contrast ratio, 1 to 10
A composite 11 having a thickness of μm is required. Next, the operation of the liquid crystal light modulator of the present embodiment shown in FIG. 1 will be described with reference to the drawings.

When the negative voltage of the power supply 8A is applied to the upper transparent electrode 4A by the switch 7 in FIG. 1, the spontaneous polarization of the liquid crystal molecules is increased (toward the transparent electrode 4A).
Turn to. Along with this, the liquid crystal molecules 14A are tilted and arranged by a tilt angle from the rubbing direction of the alignment films 2A, 2B while maintaining the horizontal direction on the substrate surface, as shown in the operation diagram of FIG. At this time, since the polarization direction of the light transmitted through the polarizing plate 10A coincides with the long axis of the liquid crystal molecules 14A, the birefringence effect does not appear, and the polarization state of the light does not change. Therefore, the complex 11
Is transmitted through the polarizing plate 10B on the emission side and cannot be transmitted (opaque state).

Next, the switch 8 shown in FIG.
Is applied to the upper transparent electrode 4A. In this case, the liquid crystal domains divided by the mesh-shaped synthetic resin 3 have different threshold voltages, so that in some liquid crystal domains, the spontaneous polarization of the liquid crystal molecules 14B is downward (toward the transparent electrode 4B). Turn around. As shown in FIG. 3, the liquid crystal molecules 14B in the liquid crystal domain are arranged in a tilt direction opposite to the direction of the alignment treatment of the alignment films 2A and 2B by a tilt angle. In this liquid crystal domain, with respect to the polarization axis of the incident light,
Since the major axis of the molecule 14B is tilted twice as large as the tilt angle, a phase difference occurs between the two orthogonal polarization components of the light, so that the polarization state of the emitted light changes. By adjusting the film thickness of the liquid crystal / resin composite 11 and the refractive index anisotropy of the liquid crystal 1 in advance so that a phase difference of 180 ° occurs, light emitted from the liquid crystal / resin composite 11 can be adjusted. The light can be converted to linearly polarized light parallel to the exit-side polarizing plate 10B. Therefore, the light transmitted through the liquid crystal domain can be transmitted without being absorbed by the polarizing plate 10B on the emission side. At this time, a liquid crystal domain showing a transparent alignment and a liquid crystal domain showing an opaque alignment are mixed, and a halftone can be obtained by the area ratio of these.

Further, the switch 8 in FIG.
When a positive DC voltage having a large C is applied to the upper transparent electrode 4A, as shown in FIG.
The orientation indicates a transparent state. In this case, most of the incident light is emitted without being absorbed by the polarizing plate 10B, and becomes a transparent state. Such opaque, half-tone, and transparent states are:
Even when the applied voltage is set to zero, the orientation of the liquid crystal molecules is maintained because it exhibits a memory property. Thereby, a memory operation having halftone can be realized.

A positive voltage pulse having a different level was temporarily applied to the above-mentioned liquid crystal light modulator produced as an example of this embodiment, and monochromatic incident light 9 (helium neon laser light having a wavelength of 633 nm) was incident. FIG. 5 shows a change in the intensity of the emitted light in this case. It can be confirmed that the halftone transmittance is maintained even when the applied voltage becomes zero, according to the intensity of the voltage pulse. Further, a reset operation in which the intensity of the emitted light becomes low due to the negative voltage pulse is obtained. The response time of this device was as fast as 200 μs when 20 V was applied. By using the liquid crystal 1 having a large spontaneous polarization,
Further speedup is possible.

[0021]

As described above, according to the present invention,
By dispersing in the ferroelectric liquid crystal 1 a fine network synthetic resin 3 having a shape elongated in the alignment processing direction of the alignment films 2A and 2B, a halftone memory function based on area gradation is obtained.
Moreover, it is possible to provide a liquid crystal light modulator excellent in contrast, light transmittance, resolution, in-plane uniformity, and stability. Therefore, the liquid crystal light modulator of the present invention can be suitably applied to a display, and when the present invention is used, a halftone memory operation can be performed using a ferroelectric liquid crystal, and contrast, light transmittance, A display with excellent resolution, in-plane uniformity, and stability can be realized.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing one embodiment of a liquid crystal light modulator of the present invention;

FIG. 2 is an operation diagram showing an opaque state of the liquid crystal light modulator shown in FIG. 1;

FIG. 3 is an operation diagram showing a halftone state of the liquid crystal light modulator shown in FIG. 1;

FIG. 4 is an operation diagram showing a transparent state of the liquid crystal light modulator shown in FIG. 1,

FIG. 5 is a diagram showing waveforms of a pulse voltage intensity and an emission light intensity of the liquid crystal light modulator shown in FIG. 1;

FIG. 6 is a diagram showing a configuration of a conventional example 1 of a liquid crystal light modulator;

FIG. 7 is a diagram showing a configuration of a second conventional example of the liquid crystal light modulator;

FIG. 8 is a diagram showing a configuration of a conventional example 3 of a liquid crystal optical modulator;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Ferroelectric liquid crystal 2A, 2B Alignment film 3 Synthetic resin 4A, 4B Transparent electrode 5A, 5B Glass substrate 6 Lead wire 7 Switch 8A, 8B, 8C DC voltage source 9 Incident light 10A, 10B Polarizer 11 Liquid crystal / resin composite DESCRIPTION OF SYMBOLS 12 Outgoing light 13 Seal resin 14A, 14B Liquid crystal molecule 15 Power supply 16 Microsphere 17A, 17B Ultra-thin alignment film 18 Diode 19 Variable electric resistance

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-5-88150 (JP, A) JP-A-5-150229 (JP, A) JP-A-4-119320 (JP, A) JP-A-4-119 250427 (JP, A) JP-A-4-318812 (JP, A) JP-A-4-318518 (JP, A) JP-A-5-264953 (JP, A) JP-A-4-281425 (JP, A) (58) Field surveyed (Int.Cl. ⁷ , DB name) G02F 1/1337 510 G02F 1/1334 G02F 1/141

Claims (7)

(57) [Claims] 1. A liquid crystal / resin composite comprising a ferroelectric liquid crystal having a spontaneous polarization and exhibiting a chiral smectic C phase and a fine three-dimensional network-like synthetic resin having a thickness equal to or less than the wavelength of incident light. If, distribution of the orientation film of the liquid crystal molecules sandwiched between the liquid crystal-polymer composite material
And the alignment layer to be arranged in the direction the process direction, and transparent electrodes sandwiching said orientation films and said liquid crystal-polymer composite material, the liquid crystal-resin
The bias that substantially sandwiches the composite, the alignment film, and the transparent electrode
A polarizing plate whose light directions are orthogonal to each other, and the transparent electrode
And voltage applying means for applying a voltage to
The polarity and level of the voltage applied to the transparent electrode
Liquid crystal domains that exhibit transparent alignment by changing
Arbitrary ratio between liquid crystal domain and opaque alignment
So that light modulation of any desired intensity can be performed.
Liquid crystal light modulator, characterized in that the. 2. The liquid crystal optical modulator according to claim 1, wherein the content of the synthetic resin is not more than 10% by weight of the liquid crystal / resin composite. 3. The liquid crystal light modulator according to claim 1, wherein the mesh of the synthetic resin has a shape extending in the alignment processing direction of the alignment film. 4. The liquid crystal optical modulator according to claim 1, wherein the synthetic resin is formed at a temperature at which the liquid crystal exhibits a nematic phase. 5. The method according to claim 1, wherein the synthetic resin is an acrylic resin, an epoxy resin, a urethane resin, or a copolymer thereof formed by light curing, heat curing, or reaction curing. 2. The liquid crystal light modulator according to claim 1. 6. The method according to claim 1, wherein the alignment film is any one of a rubbed alignment-treated polyimide resin, a polyvinyl alcohol resin, obliquely deposited SiO, SiO ₂ , and a polyimide resin formed by a Langmuir-Blodgett method. The liquid crystal light modulator according to any one of claims 1 to 5, characterized in that: 7. The liquid crystal is a Schiff base ferroelectric liquid crystal, an azo ferroelectric liquid crystal, an azoxy ferroelectric liquid crystal, a biphenyl ferroelectric liquid crystal, an ester ferroelectric liquid crystal, or a phenylpyrimidine ferroelectric liquid crystal. 7. The liquid crystal optical modulator according to claim 1, wherein the modulator is a dielectric liquid crystal.