JP3073657B2 - Liquid crystal light valve and projection type liquid crystal display device using the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projection type liquid crystal display,
The present invention relates to an optical writing type liquid crystal light valve used for an optical arithmetic unit, a wavelength converter, and the like, and a projection type liquid crystal display device using the same.

[0002]

2. Description of the Related Art In recent years, conferences and the like using a large screen display have been actively performed. Conventionally, a slide projector or an overhead projector has been used as a large-screen display. However, in general, since the screen brightness of the projector is very low, it is necessary to darken the entire room while using the projector in order to view the screen. . For this reason, in order to view the screen of the projector at normal brightness, that is, at a brightness at which objects can be written or read in a room, the screen must have high brightness.

As one method for solving such a problem, reference 1 (US Pat. No. 4,019,807)
Applicant Donald D. Boswell, Jan
Grinberg, Alexander D.S. Jaco
bson, Gary D. Myer Hughes
Aircraft Company) discloses a projection type liquid crystal display device using an optical writing type liquid crystal light valve.

The above-mentioned optical writing type liquid crystal light valve (hereinafter, referred to as “light valve”)
FIG. 7 shows a general configuration example of a liquid crystal light valve). As shown in FIG. 7, the liquid crystal light valve 110
A liquid crystal layer 106 that modulates read light by a voltage change;
Light reflection layer 1 made of a dielectric that reflects read light
05, a light-shielding layer 104 made of CdTe (cadmium telluride) for blocking transmitted light from the light reflection layer, and a light made of CdS (cadmium sulfide) for changing the impedance depending on the intensity of the incident light and controlling the voltage applied to the liquid crystal layer 106 The conductive layer 103 has a sandwich structure in which these are sandwiched between light-transmitting substrates 101 such as glass on which a transparent conductive film 102 is formed. Although not shown, the transparent conductive film 102 and the light reflection layer 105 close to the liquid crystal layer 106 include:
An alignment layer for aligning liquid crystal is provided.

FIG. 8 shows an example of a projection type liquid crystal display device using the optical writing type liquid crystal light valve having the above configuration. In this projection type liquid crystal display device, light from the light source 120 is transmitted through the lens system 1.
22b, passing through the polarizing beam splitter 121,
The light enters the liquid crystal light valve 110. The liquid crystal light valve is connected to a CRT 125 as a writing light source 126 via an optic fiber plate 124. Accordingly, an image to be projected is written into the liquid crystal light valve 110 by the writing light source 126, and is output as light modulated according to image information in the liquid crystal light valve 110.
21, through a lens system 122 a, a screen 123
Projected above.

As one of the display modes used for the liquid crystal light valve, reference 2 (William.
Bleha, Jan Grinberg, Alexan
der D. Jacobson and Gary
D. Meyr HughesAircraft Lab
oratories, Malibu, CA: SID'7
7 Digest P.S. 104) etc. (hereinafter, HFE)
Mode and abbreviation) are known.

In the HFE mode, a nematic liquid crystal having a positive dielectric anisotropy is in an alignment state twisted by 45 °, and when a voltage is applied to the liquid crystal layer, the liquid crystal molecules respond to an electric field and the substrate responds to an electric field. The incident light is tilted in the normal direction, and the incident light rotates in the polarization direction due to the birefringence effect and reflection caused by the tilt and twist of the liquid crystal molecules. The rotated light passes through the polarizing beam splitter, and the screen is in a bright state. On the other hand, when no voltage is applied, the light incident on the liquid crystal layer is not reflected through the polarizing beam splitter because the polarization direction at the time of incidence is maintained even if reflected, so that no image is projected. Then, the screen becomes dark.

Reference 3 (Rodney D. Stee)
ling, Robert D.S. Te Kolste,
Joseph M. Maggerty, Thomas
C. Borah, William P.M. Bleha H
ughes Aircraft Company, Ca
rlsbad, CA: SID '90 Digest
P. In the projection type liquid crystal display device disclosed in 327), a CRT is used as a device for writing an image to a liquid crystal light valve. For this reason, in this projection type liquid crystal display device, since the writing light source is a CRT, an image is written with weak writing light, and the projected image is read with strong reading light.

[0009]

By the way, in recent years, the resolution of images has been increased by next-generation media media represented by high-definition televisions, and the resolution of projection type liquid crystal display devices has also been enhanced. To increase the resolution of the liquid crystal light valve, it is necessary to increase the resistance of each layer constituting the liquid crystal light valve. However, if the impedance ZM of an intermediate layer (hereinafter, simply referred to as an intermediate layer) between transparent substrates such as a dielectric mirror layer and a light-shielding layer is increased, the intermediate state in the photo state where the writing light is incident is increased. The divided voltage at the layer increases and the divided voltage at the liquid crystal layer decreases. Therefore, the liquid crystal light valve in which the impedance of the intermediate layer is increased in resistance becomes a state in which the liquid crystal cannot be efficiently driven by weak writing light, that is, a state in which light sensitivity is poor. Therefore, when the resistance of the intermediate layer is increased, there is a fatal problem that the sensitivity of the liquid crystal light valve is reduced.

For this reason, in order to improve the light sensitivity of the liquid crystal light valve, it is conceivable to increase the amount of light of the CRT which is a writing light source. However, if the amount of light of the CRT is increased, bleeding of picture elements occurs. There is a problem that the resolution of the image is reduced.

CdS used as a photoconductor layer in Document 1 has excellent photoconductivity, but contains cadmium which is a harmful substance, and thus is not preferable in terms of environmental problems. For this reason, hydrogenated amorphous silicon (hereinafter referred to as a-Si: H) is used as a photoconductive substance. Since a-Si: H has a higher dielectric constant than CdS, a-Si: H which is a photoconductor layer is required to obtain a dark state impedance in which writing light is not incident, which is the same as when CdS is used. Need to be thicker. However, when the thickness of the photoconductor layer is increased, a portion where writing light is not absorbed at the time of photo is increased, so that a voltage loss portion is increased, which may cause a problem of deterioration in photosensitivity of the liquid crystal light valve.

Further, when the resistance of the intermediate layer or the like is increased, the ratio of the divided voltage applied to the liquid crystal layer in the dark state and the photo state becomes smaller. When the divided voltage ratio is small, it is necessary to drive the liquid crystal light valve using a liquid crystal display mode having good steepness. As such a liquid crystal display mode having good steepness, for example, DAP (tilt vertical alignment: Deformation) described in the above-mentioned reference 3 is described.
for Aligned Phase (ECB) -type ECB (Electrically Controlled Birefringence)
lled Birefringence) (hereinafter DA)
(Referred to as P-type ECB) mode.

As a method of aligning a liquid crystal in the DAP type ECB mode, reference 4 (US Pat.
5,011,267 Applicant Hughes Airc
Raft Company)
The oblique deposition method of performing a surface treatment with a long-chain alcohol after the two-step oblique deposition is used.

However, this method has the following disadvantages. In the oblique deposition method, the pretilt angle of the liquid crystal greatly changes when the deposition conditions such as the deposition angle, the deposition rate, the degree of vacuum, the substrate temperature, and the film thickness, the liquid crystal material, and the deposition material are different. In addition, when the substrate is large, the above conditions such as the deposition angle cannot be made equal in the plane, and it is difficult to obtain a large area and uniform inclined vertical alignment with good reproducibility.

Therefore, in the DAP type ECB mode,
A liquid crystal light valve with a large panel size cannot be created. In addition, since production can be performed only with a substrate having a small area, it is extremely difficult to increase productivity.

[0016]

According to a first aspect of the present invention, there is provided a liquid crystal light valve having an electrode, a transparent substrate having at least a photoconductor layer and a light reflecting layer on the electrode, and an electrode. a transparent substrate constituting the transparent substrate and the pair are respectively <br/> formed on both the transparent substrate, an alignment film for aligning liquid crystal molecules, and a liquid crystal layer which is formed by sealing liquid crystal between the two alignment films In a light-writing type liquid crystal light valve, a pretilt angle θp of liquid crystal molecules near a contact portion between each of the alignment films and the liquid crystal layer.
Are both in the range of 3 ° <θp <10 °.

The liquid crystal light valve of the second aspect is the first aspect of the invention.
In the above described liquid crystal light valve, the photoconductor layer is formed of an amorphous semiconductor containing silicon as a main component.

The liquid crystal light valve according to the third aspect is the second aspect of the invention.
Or the liquid crystal light valve according to 3, wherein the liquid crystal display mode of the liquid crystal layer is a hybrid electric field effect mode.

According to a fourth aspect of the present invention, there is provided a projection type liquid crystal display device, wherein three writing image generating means for generating writing images corresponding to red, blue and green, and three primary color images are emitted in response to the incidence of the writing image. A projection type liquid crystal display device comprising three optical writing type liquid crystal light valves and projection means for respectively entering the three primary color reading lights of red, blue and green into the liquid crystal light valve and synthesizing and projecting the reflected lights. The liquid crystal light valve is characterized in that the liquid crystal light valve according to claim 1, 2 or 3 is used.

[0020]

According to the claim 1 configured [act], together pretilt angle θp of the liquid crystal molecules in contact near the site of the alignment films and the liquid crystal layer
In the range of 3 ° <θp <10 °, the relative permittivity in a dark state where light from the writing light source does not enter can be increased, and as a result, the impedance of the liquid crystal layer in the dark state can be reduced. can do.

As a result, the resolution and the light sensitivity which are originally in a trade-off relationship can be made compatible, so that the liquid crystal can be driven by weak writing light while maintaining the high resolution. As a result, an optical writing type liquid crystal light valve with high resolution and high light sensitivity can be realized.

Further, since a liquid crystal light valve having high photosensitivity can be realized as described above, the writing light source can be made compact, and therefore, any application system using the liquid crystal light valve can be made compact.

According to the second aspect of the present invention, the dielectric constant of the photoconductor layer is made similar to that of the liquid crystal layer by using an amorphous semiconductor containing silicon as a main component as the photoconductor layer. Therefore, it is possible to more effectively realize an optical writing type liquid crystal light valve having high resolution and high light sensitivity.

According to the third aspect of the present invention, since the hybrid field effect mode in which the parallel alignment is twisted by 45 ° is adopted as the liquid crystal display mode, the conventional TN mode can be used without increasing a special process when forming the liquid crystal layer. Can be used as it is. Thereby, the time and cost for manufacturing the liquid crystal light valve can be reduced.

According to the structure of the fourth aspect, by using the liquid crystal light valve according to the first, second or third aspect, a projection type liquid crystal display device having high resolution and high contrast can be provided.

[0026]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIGS.

As shown in FIG. 1, a liquid crystal light valve LVA according to the present embodiment has a glass substrate (transparent substrate) 1 having a transparent electrode 4 formed on the surface and a surface facing the transparent electrode (electrode) 4. A glass substrate (transparent substrate) on which an electrode (electrode) 5 is formed and an antireflection film 3 is formed on the other surface
2, a sandwich structure in which a photoconductor layer 6, a light shielding layer 7, a dielectric mirror (light reflection layer) 12, an alignment film 9, a liquid crystal layer 11, and an alignment film 8 are formed in this order from the glass substrate 1 side. A spacer 1 is provided between the transparent electrode 4 and the counter electrode 5 to keep the distance between the transparent electrode 4 and the counter electrode 5 constant.
0.10 is provided.

That is, the liquid crystal light valve LVA having the above structure
Then, the writing light 14 is incident on the photoconductor layer 6 via the glass substrate 1, the impedance of the photoconductor layer 6 is changed by the intensity of the incident light, the voltage applied to the liquid crystal layer 11 is controlled, and the While changing the alignment state and modulating the incident light, the reading light 13 is transmitted through the glass substrate 2 to the liquid crystal layer 1.
1, the incident light is reflected by the dielectric mirror 12, modulated by the liquid crystal layer 11, and emitted from the glass substrate 2.

This liquid crystal light valve LVA is manufactured as follows. First, a transparent conductive film made of indium oxide (ITO) doped with tin is formed on the entire surface of the glass substrate 1 by sputtering, and the transparent electrode 4 is formed on the glass substrate 1.

Next, an amorphous silicon hydride (a-Si: amorphous semiconductor) is formed on the transparent electrode 4 as the photoconductor layer 6.
H) Form a film. This a-Si: H film is made of silane (S
An iH ₄ ) gas and a hydrogen (H ₂ ) gas are used as raw materials and formed by plasma CVD (chemical vapor deposition). At this time, the gas pressure is 0.3 Torr, and the substrate temperature is 280 ° C. The thickness of the a-Si: H film is about 8 μm.

The photoconductor layer 106 has a-S
In addition to i: H, amorphous hydrogenated silicon carbide (a-SiC:
H) and amorphous silicon germanium hydride (a-SiG
e: H) can also be used.

When an a-SiC: H film is used as the photoconductor layer, SiH ₄ gas, H ₂ gas and CH ₄ gas are mixed at a ratio of 10: 1 to 20 as raw materials, and plasma CVD is used. Formed. The gas pressure at this time is 0.2
Torr, the substrate temperature is 300 ° C. This a-Si
The thickness of the C: H film is about 7.5 μm.

Further, a-SiGe: H is used as the photoconductor layer.
When a film is used, SiH ₄ gas, H ₂ gas, and germane gas (GeH ₄ ) are mixed as raw materials at a ratio of 10: 1 to 50, and formed by plasma CVD. At this time, the gas pressure is 0.3 Torr, and the substrate temperature is 250 ° C.
The thickness of the a-SiGe: H film is about 9 μm.

Next, a light-shielding layer 7 for blocking light incident on the photoconductor layer 6 from the liquid crystal layer 11 described later is formed on the photoconductor layer 6. The light-shielding layer 7 is formed so as to have a thickness of about 1 μm by thinning a carbon-dispersed acrylic resin by spin coating and baking it at 250 ° C.

Thereafter, a dielectric mirror 12 for reflecting light incident on the photoconductor layer 6 from the liquid crystal layer 11 side is formed on the light shielding layer 7. The dielectric mirror 12 forms a multilayer film made of titanium oxide (TiO ₂ ) and silicon oxide (SiO ₂ ) by an electron beam evaporation method.

It is also possible to use a fiber plate for the glass substrate 1.

On the other hand, a transparent conductive film made of ITO is deposited on the glass substrate 2 facing the glass substrate 1 by sputtering to form the counter electrode 5. Further, an antireflection film 3 for preventing surface reflection of glass is formed on the glass substrate 2 on the side where the readout light 13 is incident.

Next, the counter electrode 5 and the dielectric mirror 12
An alignment film (described in Table 1 below) (manufactured by Nippon Synthetic Rubber Co.)
Are thinned by spin coating and baked at 180 ° C. to form alignment films 8 and 9 having a thickness of about 500 °. After that, the alignment films 8 and 9 are subjected to an alignment treatment by rubbing. The rubbing direction at this time was a direction in which the alignment state of the liquid crystal molecules was twisted by 45 °. That is, the liquid crystal layer 11 has a hybrid electric field effect (Hybrid
It is driven in a Field Effect (HFE) mode.

In the HFE mode, when a voltage is applied to the liquid crystal layer 11, the liquid crystal molecules respond to an electric field and tilt in the normal direction of the substrate, and the incident light comes from the tilt and twist of the liquid crystal molecules. The polarization direction is rotated by the birefringence effect and reflection. On the other hand, when no voltage is applied, the light incident on the liquid crystal layer 11 retains the polarization direction at the time of incidence even if it is reflected due to the optical rotation of the liquid crystal.

Further, the above glass substrates 1 and 2 are bonded via spacers 10 and 10 which also serve as a seal, and a liquid crystal A (described in Table 2 below) is vacuum-injected between the substrates. Subsequently, the liquid crystal layer 11 is formed by sealing to form the liquid crystal light valve LVA of the present embodiment.

Further, the liquid crystal light valve LVA having the above structure
, Four types of liquid crystal light valves L using four types of alignment films having different pretilt angles as the alignment films 8 and 9.
VAa to liquid crystal light valve LVAd were prepared.

Table 1 shows the relationship between the alignment films used for the alignment films 8 and 9 and the pretilt angles. In Table 1, the pretilt angle θp (°) is the pretilt angle of the liquid crystal molecules near the alignment films 8.9.

[0043]

[Table 1]

Further, the liquid crystal light valves LVaa-
In the liquid crystal light valve LVAd, three types of liquid crystals having a dielectric constant ε as shown in Table 2 below are used as the liquid crystal used for the liquid crystal layer 11, and the liquid crystal light valves LVBa to LVBa are used.
Liquid crystal light valve LVBd, liquid crystal light valve LVCa
-Liquid crystal light valve LVCd was prepared.

[0045]

[Table 2]

However, the above liquid crystals were all nematic liquid crystals manufactured by Merck & Co.

Here, in the alignment films and the liquid crystal shown in Tables 1 and 2, when the pretilt angle θp and the reflectance of the liquid crystal molecules near the contact portion between the alignment films 8.9 and the liquid crystal layer 11 are minimized. Measure the relationship with the relative permittivity ε _LCRmin of the liquid crystal,
It is shown in Table 3 below. FIG. 2 shows the relationship between the pretilt angle θp and the relative permittivity ε _LCRmin .

[0048]

[Table 3]

As a result, as shown in Table 3 and FIG. 2, as the pretilt angle θp increases, the relative permittivity ε _LCRmin of all the liquid crystals increases. In particular, it can be seen that the relative permittivity ε _LCRmin sharply increases from the point where the pretilt angle θp is 3 °.

The liquid crystal light valve LVA is driven by first applying an AC voltage to the liquid crystal light valve LVA and controlling the voltage applied to the liquid crystal layer 11 by impedance switching of the photoconductor layer 6. .

Generally, in order to increase the resolution of the liquid crystal light valve, it is necessary to increase the resistance of each layer constituting the liquid crystal light valve. However, for example, the dielectric mirror 1
2. Impedance ZM of an intermediate layer (hereinafter simply referred to as an intermediate layer) between the glass substrates 1 and 2, such as the light shielding layer 7.
When the resistance of the liquid crystal layer 11 is increased, the divided voltage in the intermediate layer increases and the divided voltage to the liquid crystal layer 11 decreases in the photo state where the writing light is incident. Therefore, the liquid crystal light valve in which the impedance of the intermediate layer is increased in resistance becomes a state in which the liquid crystal cannot be efficiently driven by weak writing light, that is, a state in which light sensitivity is poor. Therefore, when the resistance of the intermediate layer is increased, there is a fatal problem that the sensitivity of the liquid crystal light valve is reduced.

Further, in order to improve the light sensitivity of the liquid crystal light valve, it is conceivable to increase the light amount of the writing light source. However, if the light amount is increased, generally, the bleeding of picture elements of the image occurs, and There is a problem of lowering the resolution.

Therefore, generally, in a liquid crystal light valve, there is a trade-off between high resolution and high light sensitivity.

That is, in order to make the liquid crystal light valve LVA have high luminance and high resolution, in a dark state where writing light does not enter the liquid crystal layer 11, in a photo state where writing light enters the photoconductor layer 6, for example, 200 μw / cm ²
A voltage must be applied to the liquid crystal layer 11 with the weak writing light. It is assumed that the liquid crystal layer 11 has a minimum reflectance in a dark state and a maximum reflectance in a photo state in an applied voltage.

Therefore, in order to make the liquid crystal light valve LVA have high brightness and high resolution, the impedance of the photoconductor layer 6 in the dark state is Z _PCdark , the impedance of the photoconductor layer 6 in the photo state is Z _PCphoto , When the impedance of the liquid crystal layer 11 in the dark state is Z _LCRmin and the impedance of the liquid crystal layer 11 in the photo state is Z _LCRmax ,

[0056]

(Equation 1)

[0057]

(Equation 2)

Must be obtained.

Each layer constituting the liquid crystal light valve LVA such as the liquid crystal layer 11 can be replaced with a parallel circuit of a resistance component R and a capacitance component C. The combined impedance Z of the parallel circuit is

[0060]

(Equation 3)

Is expressed as follows. The electrode area is S, the film thickness is d, the vacuum dielectric constant is ε ₀ , the relative dielectric constant is ε _r , and the resistivity is ρ
Then, the resistance component R and the capacitance component C are respectively

[0062]

(Equation 4)

## EQU10 ## Therefore, when substituting into equation (3),

[0064]

(Equation 5)

Is expressed as follows.

In order to achieve both high resolution and high light sensitivity in the liquid crystal light valve, the impedances of the liquid crystal layer 11 and the photoconductor layer 6 are set to predetermined values according to the above equations (1) and (2). It is thought that it is necessary to balance. In particular, glass substrates 1 and 2
The photoconductor layer 6 other than the liquid crystal layer 11 existing therebetween, and the light shielding layer 7
It is conceivable that the divided voltage of the liquid crystal layer 11 is reduced by increasing the resistance of the intermediate layer.

As a method of increasing the divided voltage to the liquid crystal layer 11, the following three methods can be considered.

To increase the impedance of the photoconductor layer 6 in the dark state, the thickness of the photoconductor layer 6 is increased.

The photoconductivity of the photoconductor layer 6 is increased in order to lower the impedance of the photoconductor layer 6 at the time of photo.

A liquid crystal having a large relative dielectric constant ⊥ (the relative dielectric constant of the liquid crystal before voltage application) and a small ΔΔ is used.

However, there is a problem in terms of process and cost. Also, since a-Si: H is used, there is an upper limit in photoconductivity.

From the above, it can be seen that it is desirable to employ the above method.

Therefore, as the liquid crystal having a large relative dielectric constant ε⊥ and a small Δε, the liquid crystals (1) and (2)
It is considered that the liquid crystal obtained from the equation (3), for example, the liquid crystal shown in Table 2 above is optimal at the present stage.

Further, as the optimum liquid crystal conditions determined from the equations (1), (2) and (3), the impedance Z _LCRmin of the liquid crystal layer 11 in the dark state is small, and the impedance Z _LCRmin of the liquid crystal layer 11 in the photo state is small. _{Large LCRmax} is required. Further, by simulation and the like, at this stage, the dielectric constant ε _LCmin when the reflectance of the liquid crystal is the minimum is 7 to 8 and the reflectance when the reflectance of the liquid crystal is the maximum is It has been found that a dielectric constant ε _LCmax of 10-11 is required.

Further, in order to examine the pretilt angle dependency of the light sensitivity of the liquid crystal light valve LVA prepared by the above method, the writing light amount-reflectance (PR) characteristic was measured.
The results are described below. In this measurement, the liquid crystal light valve LVAa and the liquid crystal light valve LVAc, that is, the liquid crystal A shown in Table 2 was used for the liquid crystal layer 11, and the alignment film 8 ·
In No. 9, 2 using the alignment films a and c shown in Table 1 was used.
Light quantity-reflectivity (P
-R) The properties were measured.

The results of the above measurement are shown in FIGS.
Here, the PR characteristic expresses how the reflectance is changed by applying a voltage or a threshold voltage at which the reflectance obtained by the VR characteristic is minimized, and changing the writing light amount. . Further, the writing light amount is increased, and the writing light amount necessary for the reflectance to reach 95% of saturation is defined as the switching light amount.

As shown in FIG. 3, in the liquid crystal light valve LVAa in which the pretilt angle θp is 1 °, it can be seen that the reflectance gradually increases as the writing light amount is increased. The switching light amount at this time is about 1
000 μW / cm ² . On the other hand, as shown in FIG. 4, in the liquid crystal light valve LVAc in which the pretilt angle θp is 5 °, it can be seen that as the writing light amount is increased, the reflectance sharply increases with a small writing light amount. The switching light amount at this time is about 300 μW /
cm ² .

Therefore, in order to obtain a so-called high-sensitivity liquid crystal light valve that can be driven by weak writing light, it is understood that the pretilt angle θp is more preferably 5 ° than 1 °.

The resolution of the liquid crystal light valve LVAa and the liquid crystal light valve LVAc was measured. still,
The writing light amount is a switching light amount.

As a result, the resolution of the liquid crystal light valve LVAa was 35 linepair / mm, and the liquid crystal light valve LVAc
Has a resolution of 40 linepair / mm. Therefore, it was found that the pretilt angle θp of 5 ° was higher than that of 1 ° and the resolution was higher while maintaining high light sensitivity.

From the above results, the switching light amounts of the liquid crystal light valves LVAa to LVAd using the liquid crystal A, the liquid crystal light valves LVBa to LVBa using the liquid crystal B, and the liquid crystal light valves LVCa to dCa using the liquid crystal C are shown. Is shown in FIG.

FIG. 5 shows that the switching light amount decreases as the pretilt angle θp increases. Further, the switching light amount decreases sharply from the pretilt angle θp of 3 ° to 5 °. As a result, in order to realize a highly sensitive liquid crystal light valve,
It is understood that the pretilt angle θp is desirably 3 ° or more. When a polyimide film is used as the alignment film, the upper limit of the pretilt angle θp is about 10 ° from the stability of the pretilt angle.

Therefore, in order to realize a liquid crystal light valve with high sensitivity, the pretilt angle θp should be 3 ° <θp <1.
0 °, preferably 5 ° <θp <10 °.

According to the present invention, the alignment film 8 has a pretilt angle of 5 ° to 10 °, which is a high pretilt angle, of the liquid crystal molecules in the vicinity of the contact portion between the liquid crystal layer 11 and the alignment films 8 and 9 of the liquid crystal light valve LVA. The use of 9 makes it possible to achieve both resolution and light sensitivity, which are originally in a trade-off relationship. As a result, an optical writing type liquid crystal light valve with high resolution and high light sensitivity can be realized.

Further, according to the present invention, a liquid crystal light valve with high light sensitivity can be realized, so that the writing light source can be made compact, and therefore, any application system using the liquid crystal light valve of the present invention can be made compact.

The liquid crystal display mode has a parallel orientation of 4.
Since the HFE mode twisted at 5 ° is employed, the process for producing a conventional TN mode liquid crystal device can be used as it is without increasing the process for producing the liquid crystal layer 11, and the production is easy. Also, no new capital investment is required. Therefore, it is possible to reduce the cost for manufacturing the liquid crystal light valve.

FIG. 6 shows an example of a projection system as a projection type liquid crystal display device constituted by the liquid crystal light valve LVAc produced according to this embodiment.

The above-mentioned projection system is shown in FIG.
As shown in the figure, the liquid crystal light valve LVAc is provided with TFT liquid crystal panels 22r, 22g, and 22b as image generating means.
Lamps 21r, 21g, 21b as writing light sources for displaying red, green, and blue images through
It is configured to be connected to The above-described TFT liquid crystal panels 22r, 22g, and 22b apply respective color signals (R.
G, B), whereby an image formed by the TFT liquid crystal panel is written into the liquid crystal light valve LVAc by light emitted from the writing lamps 21r, 21g, 21b. It has become.

On the other hand, the projection system described above is provided with a reading lamp 26 as a reading light source. Light emitted from the reading lamp 26 passes through filters 28 and 29 and a mirror 30 via a lens system 27. Are input to the polarization beam splitter 23 provided for each color signal. The light incident on the polarizing beam splitter 23 is individually modulated according to the light / dark level of the writing light, and each read image obtained by this is used as projection means such as the polarizing beam splitter 23 and the lens system 24. The screen 25 by the optical system 31
Is synthesized and projected.

The image projected by the projection system having the above-described structure was excellent in high resolution, high contrast, and high resolution. Therefore, by using the liquid crystal light valve having the above-described configuration, it is possible to provide a projection-type liquid crystal display device that can easily realize high-brightness, high-resolution, and high-contrast projection display.

The present invention is not limited to a projection type liquid crystal display device, but can be applied to various applications within a range that does not impair the effects of the present invention.

[0092]

The liquid crystal light valve according to the first aspect of the present invention
As described above, a transparent substrate having an electrode and at least a photoconductor layer and a light reflecting layer on the electrode, a transparent substrate having an electrode and forming a pair with the transparent substrate, and both transparent substrates To
Are formed respectively, and an alignment film for aligning liquid crystal molecules, the optical writing liquid crystal light valve comprising a liquid crystal layer which is formed by sealing liquid crystal between the two alignment films, each distribution <br/> alignment film pretilt angle theta] p of the liquid crystal molecules in contact near the site of the liquid crystal layer and is, together, a structure in the range of 3 ° <θp <10 °.

As a result, it is possible to achieve both the resolution and the light sensitivity which are originally in a trade-off relationship, so that it is possible to drive with a weak writing light while maintaining a high resolution. As a result, an optical writing type liquid crystal light valve with high resolution and high light sensitivity can be realized.

Further, since a liquid crystal light valve having high light sensitivity can be realized, a writing light source can be made compact, and therefore, there is an effect that any application system using the liquid crystal light valve of the present invention can be made compact.

A liquid crystal light valve according to a second aspect of the present invention is configured such that the photoconductor layer is formed of an amorphous semiconductor containing silicon as a main component.

As a result, the dielectric constant of the photoconductor layer can be made substantially equal to that of the liquid crystal layer, so that an optical writing type liquid crystal light valve having high resolution and high light sensitivity can be realized more effectively. It has the effect of being able to.

As described above, the liquid crystal light valve according to the third aspect of the invention has a configuration in which the liquid crystal display mode of the liquid crystal layer adopts the hybrid field effect mode.

Thus, the conventional process for producing a TN mode liquid crystal device can be used as it is without increasing the number of processes when producing a liquid crystal layer.

Therefore, an effect is obtained that the cost for manufacturing the liquid crystal light valve can be reduced.

A projection type liquid crystal display device according to a fourth aspect of the present invention comprises:
As described above, three writing image generating means for generating writing images corresponding to red, blue and green, and three optical writing liquid crystal lights for emitting three primary color images in response to the incidence of the writing image In a projection type liquid crystal display device comprising: a bulb; and projection means for respectively entering three primary color readout lights of red, blue, and green into the liquid crystal light valve and combining and projecting these reflected lights. A configuration using the liquid crystal light valve described in 1, 2, or 3.

As a result, there is an effect that a projection type liquid crystal display device having high resolution and high contrast can be provided.

[Brief description of the drawings]

FIG. 1 is a sectional view of a liquid crystal light valve according to an embodiment of the present invention.

FIG. 2 is a graph showing the relationship between the relative dielectric constant of liquid crystal and the pretilt angle of an alignment film.

FIG. 3 is a graph showing a relationship between a writing light amount and a reflectance in the liquid crystal light valve according to the present invention.

FIG. 4 is a graph showing a relationship between a writing light amount and a reflectance in the liquid crystal light valve according to the present invention.

FIG. 5 is a graph showing a pretilt angle dependency of a switching light amount of a liquid crystal light valve.

FIG. 6 is a schematic configuration diagram of a projection type liquid crystal display device using the liquid crystal light valve of the present invention.

FIG. 7 is a sectional view of a conventional liquid crystal light valve.

8 is a schematic configuration diagram of a projection type liquid crystal display device using the liquid crystal light valve shown in FIG.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 glass substrate (transparent substrate) 2 glass substrate (transparent substrate) 4 transparent electrode (electrode) 5 counter electrode (electrode) 6 photoconductor layer 8 alignment film 9 alignment film 11 liquid crystal layer 12 dielectric mirror (light reflection layer)

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Akitetsu Hatano 22-22, Nagaikecho, Abeno-ku, Osaka-shi, Osaka Inside (72) Inventor Hiroshi Morimoto 22-22 Nagaikecho, Abeno-ku, Osaka-shi, Sharp (56) References JP-A-6-160890 (JP, A) JP-A-6-59273 (JP, A) JP-A-3-279925 (JP, A) (58) Fields investigated (Int. ⁷ , DB name) G02F 1/1337

Claims (4)

(57) [Claims] A transparent substrate having an electrode, at least a photoconductor layer and a light reflecting layer on the electrode, and an electrode;
A transparent substrate having the above-described transparent substrate and pair it both transparent substrate
Each is formed, an alignment film for aligning liquid crystal molecules, the optical writing liquid crystal light valve comprising a liquid crystal layer which is formed by sealing liquid crystal between the two <br/> alignment layer, each alignment film liquid crystal light valves pretilt angle theta] p of the liquid crystal molecules in contact near the site of the liquid crystal layer, both, characterized in that in the range of 3 ° <θp <10 ° and. 2. The liquid crystal light valve according to claim 1, wherein said photoconductor layer is formed of an amorphous semiconductor containing silicon as a main component. 3. The liquid crystal light valve according to claim 1, wherein the liquid crystal display mode of the liquid crystal layer is a hybrid electric field effect mode. 4. A writing image generating means for generating writing images corresponding to red, blue and green, and three optical writing liquid crystal lights for emitting three primary color images in response to the incidence of the writing image. Red on the bulb and the liquid crystal light valve above,
4. A liquid crystal light valve according to claim 1, further comprising: projection means for respectively entering blue and green primary color readout lights and projecting the reflected lights. A projection type liquid crystal display device comprising: