JPH07248489A - Liquid crystal light modulator - Google Patents

Abstract

PURPOSE:To obtain a half tone memory function based on an area gradation and to improve contrast, light transmissivity, resolution, intra-surface uniformity and stability by dispersing finely meshed synthetic resins of a shape extending in the orientation treatment direction of oriented films within a ferroelectric liquid crystal. CONSTITUTION:The spontaneous polarization of liquid crystal molecules face downward in the liquid crystal domains divided by the meshed synthetic resins 3 when the small positive voltage of a power source 8B is impressed to an upper transparent electrode 4A by a switch 7. The major axes of the molecules incline two-times of the tilt angle with respect to the polarization axis of incident light and, therefore, a phase difference arises in the two orthogonal polarization components of light and the polarization state of the exit light changes. The light emitted from a liquid crystal/resin composite 11 is made into linearly polarized light parallel with a polarizing plate 10B if the film thickness of the liquid crystal/resin composite 11 and the refractive index anisotropy of the liquid crystal 1 are previously adjusted. The transmitted light is, therefore, not absorbed in the polarizing plate 10B and opaque domains coexist. The half tone is thus obtd.

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 which is required to have a memory property and a high speed. .

[0002]

2. Description of the Related Art An optical modulator can be realized by applying an electric field to a liquid crystal to change the alignment state of liquid crystal molecules and applying the electro-optical effect of the liquid crystal. Liquid crystal light modulators have been attracting attention in recent years as electro-optical elements for displays because they operate at a lower voltage than other crystals that exhibit an electro-optical effect and can make relatively large areas at low cost. .

As one of such liquid crystal light modulators, a narrow gap (usually 3 μm or less) is filled with a ferroelectric liquid crystal having spontaneous polarization and exhibiting a chiral smectic C phase so that the alignment state of liquid crystal molecules is changed to a twin state. There are stabilized surface-stabilized ferroelectric liquid crystals. In this case, the liquid crystal molecules have two stable alignment states that are tilted by the tilt angle (preferably about 22.5 °) peculiar to the liquid crystal material from the alignment treatment direction of the alignment film while keeping the liquid crystal molecules horizontal to the surface of the alignment film. This liquid crystal light modulator has a memory function (binary) indispensable for improving brightness and a high-speed response, and is useful for display. However, since this liquid crystal light modulator has a bistable operation, halftone display is difficult. As a method for overcoming this, there is an area gradation method in which a binary liquid crystal region is divided and halftones are realized according to the area ratio. Until now, the following devices have been proposed as a method for obtaining the area gradation method.

Conventional Example 1 As shown in FIG. 6, the synthetic resin 3 in which the spheroidal ferroelectric liquid crystal droplets 1 are dispersed is sandwiched between the transparent electrodes 4A and 4B, and the voltage of the driving power source 15 is changed. Device 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 ) 16 having a diameter of several nm are used.
The ferroelectric liquid crystal 1 having dispersed therein is the SiO alignment film 2A, 2
An element whose light transmittance is controlled by the magnitude of the voltage of the driving power supply 15 sandwiched between the transparent electrodes 4A and 4B to which B is attached (Reference: A. Yasuda, K. Nito, YY Bao, H. Takanis).
hi and NAClark, 4th International Conference on
Ferroelectric Liquid Crystals (FLC-93) Digest, N
oP -137, P.351-352). Conventional Example 3 As shown in FIG. 8, the ferroelectric liquid crystal 1 is provided between the transparent electrodes 4A and 4B to which the ultrathin alignment films 17A and 17B (polyimide, film thickness of about 2 nm) formed by the Langmuir-Blodgett method are attached. And a drive power source 15 is further connected via a diode 18 and a variable electric resistance 19, and the light transmittance is controlled by the resistance value of the electric resistance 19 (reference: Munehiro Kimura, Hiroki Maeda, CM. Gomez, Shunsuke Kobayashi,
IEICE Technical Committee on Electronic Display, No.EID 89-
43, pp.13-18).

[0005]

[Problems to be Solved by the Invention]
The elements of 3 and 3 both divide the ferroelectric liquid crystal 1.
Although halftone can be obtained by domainization, it has the following problems. In the element 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 contrast and a decrease in transmittance due to light scattering cannot be avoided. In the device of Conventional Example 2, the microspheres 16 are easily aggregated, and it is difficult to form a uniformly dispersed uniform device. Further, due to the movement of the microspheres 16 floating in the ferroelectric liquid crystal 1, 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.

Therefore, an object of the present invention is to solve the above-mentioned problems, to provide a liquid crystal light having a halftone memory function and excellent in contrast, light transmittance, resolution, in-plane uniformity, and stability. It is intended to provide a modulator.

[0007]

In order to achieve this object, the liquid crystal light modulator of the present invention comprises a ferroelectric liquid crystal having spontaneous polarization and exhibiting a chiral smectic C phase and a fine three-dimensional network composite. Liquid crystal / resin composite consisting of resin
It is characterized by comprising: an alignment film for arranging liquid crystal molecules sandwiching a resin composite, a transparent electrode sandwiching the liquid crystal / resin composite and the alignment film, and a voltage source for applying a bipolar voltage to the transparent electrode. It is a thing.

Further, in the embodiment of the present invention, the fine mesh-like synthetic resin having a shape elongated in the alignment treatment direction of the alignment film is
Since it is dispersed in the ferroelectric liquid crystal, the orientation of the ferroelectric liquid crystal is not disturbed and high contrast is obtained (conventional example 1
The problem of the element of is solved). Further, since the thickness of the resin fiber forming the mesh is extremely fine at the wavelength of the incident light or less, light scattering does not occur and the 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 shape, does not change with time, and has high stability (conventional example 2
The problem of the element of is solved). Since the mesh-like synthetic resin is uniformly formed, high in-plane uniformity can be obtained (the problem of the element of Conventional Example 2 is solved). Further, since the size of the mesh of the synthetic resin can be easily controlled by controlling the speed of resin formation, a device with high resolution can be manufactured (conventional example 3).
The problem of the element of is solved).

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the accompanying drawings. Configuration of Embodiment FIG. 1 is a sectional view of a schematic configuration of an embodiment of a liquid crystal light modulator to which the present invention is applied. In the liquid crystal light modulator of this embodiment, the ferroelectric liquid crystal 1 exhibiting the chiral smectic C phase is used.
In the inside, a synthetic resin 3 having a mesh shape extended in the alignment treatment direction of the alignment film 2A is dispersed, 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, the two transparent electrodes 4A, 4B are attached on the glass substrates 5A, 5B, and the three driving DC voltage sources 8A, 8B, 8C are provided via the lead wire 6 and the switch 7.
Connected to any of. The incident light 9 is polarized in the long axis direction of the liquid crystal molecules by the polarizing plate 10A, then enters from one glass substrate 5A, and the polarization state is controlled by the liquid crystal / resin composite 11 including the liquid crystal 1 and the synthetic resin 3. After passing through the polarizing plate 10B on the emission side, it becomes emission light 12. The polarization directions of the two polarizing plates 10A and 10B are orthogonal to each other, and the alignment treatment directions of the two alignment films 2A and 2B are parallel to each other. Further, the polarization direction of the polarizing plate 10A is inclined by the tilt angle of the liquid crystal molecules with respect to the alignment treatment direction of the alignment films 2A and 2B. The two glass substrates 5A and 5B are securely fixed around the periphery by the sealing resin 13.

The liquid crystal 1 is finely divided by the mesh synthetic resin 3 to form fine domains. Also, synthetic resin 3
Are connected in a mesh shape and have high stability without changing over time. 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 methods. It can be obtained by curing only the three components of the synthetic resin by using, and precipitating and aggregating the liquid crystal 1.
At this time, the content ratio of the resin 3 in the liquid crystal / resin composite is 10%.
By arranging the molecules of the resin material (monomer) together with the liquid crystal molecules in the alignment treatment directions of the alignment films 2A and 2B at a high temperature at which the liquid crystal 1 exhibits a nematic phase in which the liquid crystal 1 loses spontaneous polarization, and curing the resin material, It is possible to form the mesh resin 3 having a shape that extends in the alignment treatment direction of the alignment films 2A and 2B. Even when the liquid crystal 1 returns to room temperature where the liquid crystal 1 exhibits a 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. Further, since the thickness of the synthetic resin fiber 3 forming the mesh is smaller than the wavelength, it does not cause light scattering and exhibits a high light transmittance. 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 mesh-like synthetic resin 3. Further, if the formation rate of the synthetic resin 3 is controlled uniformly, the mesh resin 3 is formed uniformly, so that high in-plane uniformity can be obtained.

In order to largely control the polarization state of incident light, the refractive index anisotropy Δn (= extraordinary light refractive index ne-
It is advantageous that the ordinary light refractive index no) is large. 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. Ferroelectric liquid crystals are suitable. Furthermore, when the ferroelectric liquid crystal 1 having a large spontaneous polarization is used, high speed response and low voltage driving are possible.

For the synthetic resin 3, a transparent acrylic resin, an epoxy resin, a urethane resin, or a copolymer thereof is most suitable. Further, as the alignment film 2A, a polyimide resin subjected to rubbing alignment treatment, a polyvinyl alcohol film, obliquely vapor-deposited SiO, SiO _2, or an ultra-thin polyimide film formed by the Langmuir-Blodgett method is suitable. . It is also possible to form the composite 11 by slightly inclining the liquid crystal molecules from the surfaces of the alignment films 2A and 2B (pretilt angle). In addition, the liquid crystal molecules are aligned film 2
Even in the case of a structure (chevron structure) in which liquid crystal molecules are slightly tilted in the opposite directions on the planes A and 2B and the molecular orientation is bent inside the liquid crystal,
This method is effective.

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

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

Next, the liquid crystal 1 and the synthetic resin 3 material are heated to 100 ° C. and mixed to prepare a homogeneous solution. This homogeneous solution is applied to the gap (about 2 μm) between the alignment films 2A and 2B described above.
Then, inject while maintaining at 100 ℃. Further, it was cooled to 75 ° C. showing a nematic phase, and irradiated with ultraviolet rays (wavelength 365 nm) having an intensity of 40 mW / cm ² through the glass substrate 5A,
The mesh resin 3 is formed. After that, it is gradually cooled to room temperature.

The effective area of the liquid crystal light modulator of this embodiment produced by the above method is 20 × 20 mm ² . In order to obtain a practical contrast ratio, 1 to 10
A composite 11 with a thickness of μm is required. Operation of the Embodiment Next, the operation of the liquid crystal light modulator of this embodiment shown in FIG. 1 will be described with reference to the drawings.

When the negative voltage of the power source 8A is applied to the transparent electrode 4A on the upper surface by the switch 7 of FIG. 1, the spontaneous polarization of the liquid crystal molecules is upward (direction of the transparent electrode 4A).
Turn to. Along with this, the liquid crystal molecules 14A are inclined and arranged from the rubbing direction of the alignment films 2A and 2B by a tilt angle 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 molecule 14A, the birefringence effect does not appear and the polarization state of the light does not change. Therefore, the complex 11
The light transmitted through is absorbed by the polarizing plate 10B on the emission side and cannot be transmitted (opaque state).

Then, the switch 7 shown in FIG.
A relatively small positive voltage is applied to the upper transparent electrode 4A. In this case, since the liquid crystal domains divided by the mesh synthetic resin 3 have different threshold voltages, the spontaneous polarization of the liquid crystal molecules 14B is downward (in the direction of the transparent electrode 4B) in some liquid crystal domains. Turn to. As shown in FIG. 3, the liquid crystal molecules 14B of the liquid crystal domain are tilted and aligned in the opposite direction by the tilt angle with respect to the alignment processing direction of the alignment films 2A and 2B. In this liquid crystal domain, with respect to the polarization axis of the incident light,
Since the long axis of the molecule 14B is tilted by twice the tilt angle, a phase difference occurs between the two orthogonal polarization components of the light, and 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 ° is generated, the light emitted from the liquid crystal / resin composite 11 is It is possible to make linearly polarized light parallel to the polarizing plate 10B on the emitting side. 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 having a transparent alignment and a liquid crystal domain having an opaque alignment are mixed, and a halftone is obtained by the area ratio thereof.

Further, the switch 7 shown in FIG.
When a positive DC voltage with a large C is applied to the upper transparent electrode 4A, as shown in FIG.
The orientation is transparent. In this case, most of the incident light is emitted without being absorbed by the polarizing plate 10B and becomes in a transparent state. Such an opaque state, a halftone state, and a transparent state are
Even when the applied voltage is zero, the orientation of the liquid crystal molecules is retained because it exhibits a memory property. As a result, a memory operation having halftone can be realized.

Positive voltage pulses of different levels were temporarily applied to the above-described liquid crystal light modulator manufactured as an example of this embodiment, and monochromatic incident light 9 (helium neon laser light of wavelength 633 nm) was made incident. The change in the intensity of the emitted light in this case is shown in FIG. It can be confirmed that the halftone transmittance is maintained even when the applied voltage becomes zero, depending on the intensity of the voltage pulse. Furthermore, a reset operation has been obtained in which the intensity of emitted light is at a low level due to the negative voltage pulse. The response time of this device was as high as 200 μs when 20 V was applied. By using the liquid crystal 1 with large spontaneous polarization,
Further speedup is possible.

[0021]

As described above, according to the present invention,
By dispersing in the ferroelectric liquid crystal 1 the fine mesh-like synthetic resin 3 having a shape elongated in the alignment treatment direction of the alignment films 2A and 2B, a halftone memory function based on area gradation can be 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 by using a ferroelectric liquid crystal, and the contrast, light transmittance, A display with excellent resolution, in-plane uniformity, and stability can be realized.

[Brief description of drawings]

FIG. 1 is a block diagram showing an 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.

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

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

FIG. 5 is a diagram showing waveforms of pulse voltage intensity and emitted light intensity of the liquid crystal optical modulator shown in FIG.

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 a liquid crystal light modulator,

FIG. 8 is a diagram showing a configuration of a conventional example 3 of a liquid crystal light 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 Polarizing plate 11 Liquid crystal / resin composite 12 Emitted 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

Claims (8)

[Claims] 1. A liquid crystal / resin composite comprising a ferroelectric liquid crystal having spontaneous polarization and exhibiting a chiral smectic C phase and a fine three-dimensional mesh-like synthetic resin, and liquid crystal molecules arranged with the liquid crystal / resin composite sandwiched therebetween. A liquid crystal light modulator, comprising: an alignment film, a transparent electrode sandwiching the liquid crystal / resin composite and the alignment film, and a voltage source for applying a bipolar voltage to the transparent electrode. 2. The liquid crystal light modulator according to claim 1, wherein the content of the synthetic resin is 10% by weight or less 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 elongated in the alignment treatment direction of the alignment film. 4. The liquid crystal light modulator according to claim 1, wherein the thickness of the fiber of the synthetic resin is not more than the wavelength of incident light. 5. The liquid crystal light modulator according to claim 1, wherein the synthetic resin is formed at a temperature at which the liquid crystal exhibits a nematic phase. 6. The synthetic resin is an acrylic resin, an epoxy resin, a urethane resin formed by photo-curing, heat-curing or reaction-curing, or a copolymer thereof, according to any one of claims 1 to 5. 2. A liquid crystal light modulator according to item 1. 7. The alignment film is one of a rubbing-aligned polyimide resin, a polyvinyl alcohol resin, obliquely vapor-deposited SiO, SiO ₂ , and a polyimide resin formed by the Langmuir-Blodgett method. The liquid crystal light modulator according to claim 1, wherein the liquid crystal light modulator is a liquid crystal light modulator. 8. The Schiff base type ferroelectric liquid crystal, azo type ferroelectric liquid crystal, azoxy type ferroelectric liquid crystal, biphenyl type ferroelectric liquid crystal, ester type ferroelectric liquid crystal, or phenylpyrimidine type ferroelectric liquid crystal. The liquid crystal light modulator according to any one of claims 1 to 7, which is a dielectric liquid crystal.