JPS6257016B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for driving an electro-optical device that converts an input optical image into a projected image using the photoelectric effect.

Conventionally, a liquid crystal light valve has been known as this type of electro-optical device. As an example, JP-A-56-43681 discloses a thin film multilayer structure consisting of a liquid crystal layer, a dielectric mirror, and a photoelectric sensitive layer (photoconductive layer) sandwiched between two transparent electrodes. A liquid crystal light valve is disclosed.
In such a liquid crystal light valve, the dielectric mirror is a necessary element for reflecting the projection light incident from the liquid crystal layer side in advance so that it does not reach the photoconductive layer.

Such dielectric mirrors include, for example, ZnS,
A multilayer film consisting of Na ₃ AlF ₆ , MgF ₂ , TiO ₂ , SiO ₂ , etc. is used. At this time, in order to obtain a dielectric mirror that reflects light of wavelengths throughout the visible range, it is necessary to create a laminate of approximately 15 or more layers while precisely controlling the thickness of each layer, which requires considerably advanced manufacturing technology. It takes.
Furthermore, even if a dielectric mirror is made for the above purpose, in reality it cannot completely reflect the projected light, and a separate light absorption layer is required between the photoconductive layer and the dielectric mirror. It was necessary to establish a system to supplement its functions.

Therefore, such conventional liquid crystal light valves do not fully exhibit their intended functions, have a complicated structure, are time-consuming to manufacture, and are expensive to manufacture.

Furthermore, it has been difficult to drive such a conventional liquid crystal light valve with a direct current voltage.

Therefore, the present invention eliminates the various drawbacks of the conventional art, and also enables direct current driving, thereby facilitating the display of moving images. The object of the present invention is to provide a method for driving an electro-optical device generally called a liquid crystal light valve.

The present invention, which achieves these objects, provides an electro-optical device that includes a liquid crystal layer and a photoconductive layer having rectifying properties, and converts an input image of light into a projected image using the photoelectric effect. A process of forming a projected image based on the liquid crystal layer by applying a DC voltage in a direction opposite to the rectifying property and projecting a writing optical signal onto the photoconductive layer, and a process of forming a projected image based on the liquid crystal layer, and A method of driving an electro-optical device is characterized in that the method includes the step of erasing the projected image by applying a voltage to the projected image.

Hereinafter, the present invention will be explained in detail by way of specific examples using the drawings.

FIG. 1 is a schematic sectional view of an example of a light valve device, and in the figure, 10 is a polarizer (plate). Both 1a and 1b are transparent substrates made of glass plates or resin plates. In addition, both 2a _and 2b are transparent electrodes, such _as thin films ( _thickness ,
(approximately 500 to 3000 Å). 3 is a liquid crystal layer, and
4 is a spacer for sealing the liquid crystal layer 3 and adjusting the layer thickness. As the spacer 4, a resin adhesive mixed with alumina powder or glass fiber powder is usually used. Changes in the liquid crystal structure in the liquid crystal layer 3 include the current effect as in DSM, the TN method (twisted nematic effect), and DAP.
There are methods based on electric field effects such as (field-controlled birefringence effect) method, phase transition method, and GH (guest-host effect) method, but in this illustrated example, the GH method is adopted as the preferred method. specifically,
There are no particular restrictions on the liquid crystal used for this GH (guest host) liquid crystal layer 3, but one with a clearing temperature of 50°C or higher, preferably 60°C or higher is selected in consideration of the temperature rise during driving. . Also, although the orientation of the liquid crystal is homogeneous, even if it is twisted, the GH
Of course, there is no problem with other orientations used in the method. As the dye to be mixed into the liquid crystal as a guest, for example, an anthraquinone dye having good light resistance is preferably used. At this time, the content of the dye in the liquid crystal depends on the type of liquid crystal, but is usually 0.05 to 10% by weight, preferably 0.1 to 5% by weight. Furthermore, the thickness of this liquid crystal layer 3 is generally 1 to 20 μm.
An appropriate thickness is set depending on the performance, response speed, driving voltage, etc. of the liquid crystal. 5 is a light shielding layer, which is made with a thickness of 500 Å or more by depositing carbon or metal.
The film was formed to a thickness of about 2 μm. This light-shielding layer 5 has a planar shape as shown in FIG. 2, which is a cutaway plan view taken along lines A and A' in FIG. 1, and a large number of through holes 6 are arranged in this light-shielding layer 5. There is.
Note that one of the through holes 6 corresponds to one pixel in the projected image. Incidentally, the shape of these through holes 6 is not limited to the square shown in the illustrated example, but can be any shape. Furthermore, 7 in FIG. 1 is a light-transmitting insulating layer, which desirably has a volume resistivity of 10 ¹² Ω·cm or more. This includes, for example, SiC and Si ₃ N ₄ films formed by glow discharge decomposition, SiO ₂ films and PbTiO ₃ films formed by sputter deposition, etc.
It consists of a ferroelectric film such as PLZT or polyparaxylylene. The thickness of this transparent insulating layer 7 is
The thickness is preferably in the range of 1000 Å to 5 μm.

Reference numeral 8 denotes a reflecting mirror, which is made of a deposited film of metal such as Al forming a mirror surface with a thickness of about 500 Å to 1 μm. A large number of mirrors 8 are arranged so as to face all of the through holes 6 through the insulating layer 7, and each mirror 8 is shown in FIG. They are arranged as follows. In addition, this mirror 8-1
The holes are formed to have an area (width) at least larger than the area of the through holes 6 for the purpose of preventing light leaking from the gaps 8H between the mirrors.

Reference numeral 9 denotes a photoconductive layer exhibiting rectifying properties, and the so-called rectifying properties here are different from the rectifying properties of ordinary diodes and are a broader concept, as will be described later.

By the way, in the configuration example shown in FIG. 1, a light absorbing member such as a carbon layer is provided on the surface of the light shielding layer 5 on the side of the transparent insulating layer 7 to absorb the reflected light of the projected light by the mirror 8. This is desirable in order to increase the contrast of the projected image.

Further, the reflecting mirror 8 must be made entirely of a conductive material and must be separated, but its shape does not matter. The reason why all of the reflecting mirrors 8 are separated is that if they were continuous, they would be at the same potential and no potential difference would occur, making it impossible to form an image.

Here, the operation of the optical writing type liquid crystal light valve shown in FIG. 1 will be explained in detail using other drawings, and the concept of "rectification" in the present invention will be clarified. FIG. 4 is a schematic diagram illustrating the operating principle of the light valve device of FIG. 1.

In FIG. 4, a predetermined DC electric field is applied by a power source 20 between transparent electrodes 2a and 2b. At this time, in the region onto which the signal beam is projected, generated carriers (electrons indicated by marks in the figure) are moved to the reflecting mirror 8 by the electric field. As a result, the voltage between the transparent electrode 2a and the reflective mirror 8 increases through the through hole 6 and exceeds the threshold value, and in the liquid crystal layer 3, the liquid crystal molecules 3α with positive dielectric anisotropy and the dye 3β become homogeneous. Changes from the genius orientation state to the homeotropic orientation state. When projection light is projected here through the polarizing plate 10, the polarized light passes through the through hole 6 and reaches the reflecting mirror 8, where it is reflected and the reflected light is
RL ₂ is obtained. On the other hand, in the region where the signal beam is not incident, no photocarrier is generated, so the carrier remains on the transparent electrode 2b and does not move to the reflection mirror 8. Therefore, in this case, the voltage applied to the liquid crystal layer 3 does not exceed the threshold value and the liquid crystal molecules 3
α and dye 3β are kept in a homogeneous orientation. Therefore, the projection light (polarized light) incident here is absorbed by the dichroic dye 3β in the liquid crystal layer 3, and the amount of light reflected by the reflection mirror 8 RL ₁ is smaller than that of the reflected light RL ₂ . There is.

In this way, a projected image (an image to be projected) is formed based on the difference in the amount of reflected light, and the image generated in the liquid crystal layer 3 is enlarged and projected onto a screen (not shown) or the like.

In the above process, the light shielding layer 5 and the mirror 8 prevent the signal light from leaking to the liquid crystal layer 3 side and conversely prevent the projection light from entering the photoconductive layer 9. has been done.

In addition, in the above operation example, unless the projected image formed in the liquid crystal layer 3 is extremely fine, the projected image can be visually observed under indoor light without using special projection light. You can also do that.

Next, a specific configuration example will be explained using FIG. 5.

In the first configuration example, as shown in FIG. 5, Pt, Pd, Au or
The base layer 9a is formed by depositing Mo to a thickness of 20 to 500 Å, preferably 30 to 200 Å. Next, a gas mainly composed of SiH ₄ is decomposed by discharge to form a-
A Si-H layer 9b is formed. This a-Si-H layer 9b
becomes a weak n-type semiconductor and forms a Schottky barrier layer between it and the base layer 9a. Note that the a-Si-H layer 9b is usually called an i-layer. The thickness of this layer 9b is determined depending on the relationship with other layers, especially the liquid crystal layer 3, but is usually in the range of 5000 Å to 20 μm.

Further, on this a-Si-H layer 9b, 100 to 20,000 ppm, preferably 1,000 to 10,000 ppm of PH ₃ is mixed into a gas mainly composed of SiH ₄ and discharge decomposition is performed to form a layer with a thickness of 100 to 3,000 Å, preferably. A rectifying photoconductive layer 9 is formed by forming an n layer 9c with a thickness of 500 to 2000 Å.

Next, as in the embodiment shown in FIG. 1, a reflective mirror 8 made of Al, a transparent insulating layer 7, and a light shielding layer 5
After forming the above, a polarizing plate 10 and a transparent electrode 2a are provided on both sides of another transparent substrate 1a, and a GH liquid crystal layer 3 is sealed between the light shielding layer 5 and the transparent electrode 2a, thereby forming an example of a light valve device. is completed. A band diagram of the photoconductive layer 9 in the light valve device thus obtained is shown in FIG. 6a. As can be seen from this band diagram, when a projected image is obtained by the above device, the voltage applied between the transparent electrodes 2a and 2b is applied such that the voltage on the 2b side is negative.
At this time, it is assumed that the a-Si-H layer (i layer) 9b is directly applied to the transparent electrode 2b without forming a Schottky barrier layer.
When a carrier (...i
The dark resistance of the photoconductive layer 9 is 10 ⁸ because the layer is of weak n-type and causes injection (in this case, electrons).
If it is between Ωcm and 10 ⁹ Ωcm, the result will be unexpected. On the other hand, when a Schottky barrier layer is formed as in this example, carrier injection into the photoconductive layer 9 is prevented, and the dark resistance of the photoconductive layer 9 is reduced.
Since it is 10 ¹² Ω・cm or more, it is possible to form a projected image as expected.

In addition, the n-layer 9c in this example has the function of easily and stably sweeping the photo carrier from the reflecting mirror 8 receiving the photo carrier to the transparent electrode 2b when erasing the projected image. . however,
Since this n-layer 9c has low electrical resistance, it is necessary to divide it into a plurality of parts and electrically isolate them in the same way as the mirror 8 for image forming purposes. It is formed into a pattern substantially similar to that of the mirror 8 using photolithography.

In this case, when the projection light incident as parallel light is reflected as parallel light by reflection mirror 8, it is necessary to make the area of each n layer 9c equal to or slightly larger than that of mirror 8. Therefore, individual n
When the area of the layer 9c is smaller than that of the mirror 8, unevenness is formed on the surface of the mirror 8, scattering the incident light, and thus exhibiting an effect as a diffuser plate.

Furthermore, if this n-layer 9c is not provided and the reflection mirror 8 is formed in direct contact with the a-Si-H layer 9b, a barrier may be formed at the interface between the two, and the photo carrier sweep Inconveniences such as uneven placement and incompleteness are often observed.
However, if the barrier is not formed, the n-layer 9
c can also be omitted.

By the way, as long as the voltage applied to the liquid crystal layer 3 does not exceed the threshold value, the voltage applied to the device of this example when sweeping the photo carrier may be a forward DC voltage such that the transparent electrode 2b is positive with respect to the transparent electrode 2a, or Either AC voltage is fine.

Next, a second configuration example will be explained. In this example, on the transparent electrode 2b, a gas containing mainly SiH ₄ is placed.
_B2H6 50~ _20000ppm , preferably 200~
After mixing 10,000ppm and performing glow discharge decomposition, the thickness
P deposited between 30 and 1000 Å, preferably between 50 and 300 Å
Form layer 9a. The appropriate thickness of the P layer 9a depends on the amount of absorption of the signal beam and the formation of a depletion layer between the P layer 9a and the a-Si-H layer (i layer) 9b provided thereon. It can be decided.

Next, in the same manner as in the first configuration example, a
- After sequentially laminating the Si-H layer 9b, the n-layer 9c, the reflective mirror 8, the translucent insulating layer 7, and the light-shielding layer 5, a liquid crystal layer 3 is sealed between the other transparent electrode 2a and the light valve is turned off. Completed the device. A band diagram of the photoconductive layer 9 in this device is shown in FIG. 6b.
As can be seen, the polarity of the applied voltage when forming the projected image is the same as in the first example above, and
A similar effect can be obtained.

Also in this example, the photo carrier can be swept from the reflective mirror 8 to the transparent electrode 2b in the same manner as in the first example.

In addition to the above-mentioned materials, SiH _4
Deposited film (P-type a-
A heterojunction obtained by forming an a-Si-H layer 9b on a Si-C-H film) may also be used, and exactly the same effect can be obtained.

Furthermore, in the third example of the structure, the liquid crystal light valve device is completed in the same manner as in the above two examples except for the structure of the photoconductive layer 9. In this example, the photoconductive layer 9 is created as follows. That is, an a-Si-N-H film, a SiO ₂ film, or a polyparaxylylene film is formed on the transparent electrode 2b to a thickness of 50 to 10,000 Å, preferably 100 to 100 Å.
After forming the transparent insulating layer 9a to a thickness of 3000 Å,
Just like in the above two examples, the a-Si-H layer 9b,
The n-layers 9c are sequentially stacked.

A band diagram of the photoconductive layer 9 in this third example is shown in FIG. 6c.

In this example, from the transparent electrode 2b to the a-Si-H layer (i
The carrier injection to the layer) 9b is prevented by the insulating layer 9a, and the a-Si-H layer 9b is
Since it is a type semiconductor, the voltage polarity applied when forming a projection image is exactly the same as in the above two examples, and the same effect can be obtained. Furthermore, the photo carrier sweep operation can be performed in the same manner as above.

In the above three examples of liquid crystal light valve devices,
P by discharge decomposition of gas mainly composed of _SiH4
In addition, photoconductive layers such as the a-Si-H layer ( _i -layer), the n-layer, etc. P layer (B ₂ H ₆ etc. is used as a doping gas),
An a-Si-F-H layer (i-layer) and an n-layer (PH ₃ or the like is used as a doping gas) can be formed.

Incidentally, a-Si (a-Si-H, a-Si-F-H)
The preparation method, its properties, doping effects, etc. are described in detail in "Collection of Technologies for Utilizing Amorphous Electronic Materials" (Science Forum Publishing, 1981) and other documents, which can be referred to.

In addition, as it is easily recalled, the rectifying photoconductive layer according to the present invention includes, in addition to the above,
A laminate of SeTe, AS ₂ Se ₃ , CdS, CdTe, etc. and a transparent insulating layer, a heterojunction of CdS (n type) and CdTe (p type), etc. can also be applied.

Furthermore, the present invention will now be described in detail based on specific examples.

Example 1 On Corning 7059 slide glass 1b
In ₂ (Sn) O ₃ (manufactured by Matsuzaki Vacuum) is used as the transparent electrode 2b, and Pt is applied to it using an electron beam (PB (base pressure)) = 1 × 10 ^-6 Torr evaporation rate (R) =
The Pt layer 9a was deposited to a thickness of 40 Å at a temperature of 1 Å/S and a substrate temperature (Ts) of 80°C. Next, the a-Si-H layer 9b is formed by a capacitive coupling type glow discharge decomposition method.
was deposited to a thickness of 10 μm as follows. 20 SCCM of SiH ₄ /H ₂ = 50% gas was introduced into a reactor with anode and cathode of 200φ and a distance of 50 mm between them, and P _B
= 1 × 10 ^-6 Torr Under gas pressure = 0.05 Torr, Ts = 250°C, RF = 13.56 MHz, RF power = 15 W, glow discharge decomposition was performed, and the a-Si-H layer was placed on a slide glass for 10 hours. Deposited. The slide glass was set on the anode side. a-Si-H obtained in this way
The layer exhibits excellent photoconductivity, and when measured with a Surf-S type using a comb-shaped electrode, ρo (dark resistivity) = 10 ¹⁰ Ω cm, ρ _L (He-Ne laser, 1 m
Resistivity in W/cm ² )=10 ⁵ Ω·cm.

Next, Al was deposited to a thickness of 2000 Å on this a-Si-H layer 9b by electron beam evaporation. At this time, P _B =1×10 ^-5 Torr, Ts=60℃, R=10Å/
It was s.

Next, one piece is 90μm x 90mm by photolithography.
A reflecting mirror 8 (having a pattern as shown in FIG. 3) with an area of 100 μm and a pitch of 100 μm was formed. Furthermore,
On this reflecting mirror 8, the following a-Si-N-H
A transparent insulating layer 7 with a thickness of 3000 Å was deposited. At this time,
Using the same equipment used to fabricate a-Si-H, set the substrate that underwent the above fabrication process on the anode side, and
Under _B = 1×10 ^-6 Torr, SiH ₄ /H ₂ = 10%
5SCCM, introduce 20SCCM of pure NH ₃ and increase the gas pressure
Deposition was carried out for 5 hours under the conditions of 0.15 Torr, Ts = 250°C, and RF power = 5W. The thus obtained a-Si-
The volume resistivity of the NH layer is 10 ¹⁴ Ω·cm or more.
Next, Al is deposited on this a-Si-N-H transparent insulating layer 7.
A light shielding layer 5 of 2000 Å is deposited and has a pattern as shown in the second figure.
The overlap width with the reflecting mirror 8 in Fig. 3 is 5μ.
Patterning was carried out by photolithography to obtain m. Therefore, the area of the opening 6 is 80 μm×80 μm. Next, polyparaxylylene is applied on the light shielding layer 5.
It was deposited to a thickness of 2000 Å by vapor phase pyrolysis. The polyparaxylylene was rubbed with a cotton cloth to align the liquid crystal. Epoxy resin in which Al ₂ O ₃ powder is dispersed is applied to a thickness of 5 μm around the light-shielding layer 5 (the polyparaxylylene in that area has been removed) so as to have the openings necessary for the next step. A 7059 slide glass 1a having a transparent electrode 2a having an oriented polyparaxylylene layer (2000 Å thick) was pressure-bonded thereon. After sufficiently curing the epoxy resin, it was placed in a vacuum chamber together with a guest host liquid crystal, and heated to ~1×10 ^-2 Torr using a rotary pump.
I exhausted it so that it was. Next, the guest-host liquid crystal is used to close the opening prepared in advance, and the vacuum chamber is brought to normal pressure while leaking gradually, and the space between the light-shielding layer 5 and the transparent electrode 2a is filled with the guest-host liquid crystal, and then the opening is closed with epoxy resin. Sealed. Note that the alignment of this liquid crystal is homogeneous alignment. The guest host liquid crystal is nematic phase 1291 manufactured by Merck & Co.
Anthraquinone blue dye manufactured by BDH Chemical Co., Ltd.
A material in which D5 was dispersed at 0.5% by weight was used. The clearing point of the above liquid crystal is 107℃,
The threshold voltage is 2.2V. A polarizing film NPF-Q12 (neutral gray) manufactured by Nitto Denko was mounted on the transparent substrate 1a to complete the guest-host liquid crystal light valve device shown in FIG. FIG. 7 shows a schematic diagram of a projection device incorporating this liquid crystal light valve device. 101 is a screen with a white diffusion surface, 1
02 is a halogen lamp for projection light; 103 is a lens for condensing the projection light onto mirror 104; 10
5 is a guest host liquid crystal light valve device 106
This lens magnifies the projected image formed on the screen 101 by 20 times. A polygon mirror 107 projects the He--Ne laser emitted from the writing light source 109 and focused by the condenser lens 108 onto a predetermined position on the surface of the photoconductive layer with a spot of 100 .mu.m.phi.

Here, the formation and erasure of a projected image in this embodiment and the results of projection on the screen will be briefly described. A DC voltage of 4.2 V was applied to the transparent electrodes 2a and 2b with the 2b side serving as the negative electrode. While driving the polygon mirror 107, a writing He--Ne laser was projected onto the photoconductive layer 9 through the transparent substrate 1b. A projected image was formed on the guest-host liquid crystal using a voltage application time of 20 msec and a laser writing intensity of 200 μW/cm ² , and the projected image was projected onto the screen using projection light from a 100 mW/cm ² halogen lamp. The contrast of the resulting image on the screen was 6:1 at maximum in terms of reflected light intensity in bright and dark areas.
The projected image is erased by 1K between the transparent electrodes 2a and 2b.
This was done by applying an AC voltage of 2V at Hz for 20msec. At this time, the reverse dark resistivity of the photoconductive layer 9 is 10 ¹³ Ω・cm
With the above, the forward dark resistivity is (although there are some uneven locations)
It was 10 ⁸ to ^{10 9} Ω·cm.

Moreover, the polyparaxylylene blocked ion implantation from the transparent electrode 2a or the light shielding layer 5, and effectively acted to increase the life of the liquid crystal.

Example 2 Pt was vapor-deposited on the surface of the transparent electrode 2b on the transparent substrate 1b in the same manner as in Example 1, and then a-Si-H layer 9b was deposited.
was deposited. On this a-Si-H layer 9b, an n-layer 9c was deposited to a thickness of 1000 Å under the following conditions.

<Deposition conditions> SiH ₄ /H ₂ = 10% gas at 2SCCM, PH ₃ /H ₂ = 100PPM gas under P _B = 1×10 ^-6 Torr.
Introducing 10SCCM and setting the gas pressure to 0.1Torr, Ts=
Deposit for 16 minutes at 200°C and RF power = 8W.

The n-layer thus obtained was processed into a third layer by photolithography.
It was patterned to have the same shape as the illustrated reflecting mirror. Incidentally, the band diagram of the photoconductive layer 9 at this time is as shown in FIG. 6a.

Next, a reflective mirror 8, a transparent absolute layer 7, and a light shielding layer 5 are formed on the obtained n-layer 9c in the same manner as in Example 1, and a light shielding layer 5 having an oriented polyparaxylylene layer is formed. After sealing the guest-host liquid crystal between the transparent electrode 2a and the transparent electrode 2a, the polarizing plate 10 was mounted on the transparent substrate 1a to complete the liquid crystal light valve device of this example. Using the apparatus shown in FIG. 7 incorporating this ride valve device, an image corresponding to the write light signal was reproduced on the screen 101 in the same manner as in Example 1. However, when forming a projected image, the transparent electrode 2
The voltage applied to a and 2b was 4.3V.
Furthermore, the operation of erasing the projected image was performed using the same wire as in Example 1, but the forward direction dark resistivity of the photoconductive layer 9 was 10 ⁸ Ω・
cm, and there was little unevenness in location.

Example 3 A P layer 9a was deposited to a thickness of 100 Å on a transparent electrode (In ₂ (Sn) O ₃ ) 2a on a transparent substrate (7059 slide glass) 1a under the following conditions.

<Deposition conditions> SiH ₄ /H ₂ = 10% gas at 4SCCM, B ₂ H ₆ /H ₂ = 100PPM gas under P _B = 1×10 ^-6 Torr.
Introducing 10SCCM and setting the gas pressure to 0.1Torr, Ts=
Deposition was carried out at 250°C and RF power = 10W for 100 seconds. On the thus obtained P layer 9a, an a-Si-H layer 9b was deposited in the same manner as in Example 1, and then an N layer 9c was deposited and patterned under the same conditions as in Example 2. Similarly, a reflective mirror 8, a transparent insulating layer 7, and a light shielding layer 5 are formed, and a guest host liquid crystal is sealed between the light shielding layer 5 having an aligned polyparaxylylene layer and the transparent electrode 2a, and polarized light is generated. The liquid crystal light valve device of this example was completed by mounting the plate 10 on the transparent substrate 1a. The band diagram of the photoconductive layer 9 in this example is as shown in FIG. 6b, and the reverse dark resistivity is 10 ¹³ Ω·cm or more, the forward dark resistivity is 10 ⁸ Ω·cm, and there is little unevenness in places. Nakatsuta. An image corresponding to the write light signal was reproduced on the screen 101 in the same manner as in Example 1. The driving applied voltage for projection image formation at that time was the same as in Example 2.
It is 4.3V. The operation of erasing the projected image could also be performed under the same conditions as in Example 1.

Example 4 In Example 1, a transparent insulating film 9a made of a-Si-N-H was placed on a transparent electrode (In ₂ (Sn) O ₃ ) 2a on a transparent substrate (7059 slide glass) 1a. It was formed to a thickness of 2000 Å under the same conditions as those for forming the photosensitive insulating layer 7. Then, in the same manner as in Example 1, a-
After depositing the Si--H layer 9b, an n-layer 9c is formed and patterned under the same conditions as in Example 2. Next, a reflective mirror 8, a transparent insulating layer 7, and a light shielding layer 5 were formed in the same manner as in Example 1, and a guest host liquid crystal was placed between the light shielding layer 5 having an aligned polyparaxylylene film and the transparent electrode 2a. was sealed, and the polarizing plate 10 was mounted on the transparent substrate 1a to complete the liquid crystal light valve device 5 of this example. The band diagram of the photoconductive layer 9 in this example is as ^shown in FIG. is 10 ⁸
Ω・cm, and there was little unevenness in location. Using the device shown in FIG. 7 incorporating this liquid crystal light valve device, an image corresponding to the write light signal was reproduced on the screen 101 in the same manner as in Example 1. However, the driving voltage during projection image formation was 4.4V. Furthermore, the operation of erasing the projected image could be performed under the same conditions as in the other embodiments.

In the present invention described in detail above, 1. Display using the electro-optic effect is possible by direct current voltage driving, and in this case, moving images can be easily displayed.

2. The voltage range is wide, making it easy to control the driving voltage.

3. When a projected image is formed, the image quality is stable across the entire display surface.

4. The equipment has a longer lifespan.

5. The structure of the device components, especially the reflecting mirror, is simple, and the device can be made compact.

6. The reflection mirror element allows the reception of photo carriers in direct current voltage and drive.

Various effects such as this can be obtained.

[Brief explanation of the drawing]

1 to 3 are schematic diagrams illustrating a configuration example of the device according to the present invention, FIG. 4 is a schematic diagram illustrating an example of the operation of the device according to the present invention, and FIG. 5 is a schematic diagram illustrating an example of the operation of the device according to the present invention. 6A, B, and C are all schematic diagrams showing band diagrams. FIG. 7 is a schematic layout diagram of a projection optical system including a liquid crystal light valve device. It is. In the figure, 2a and 2b are transparent electrodes, 3 is a liquid crystal layer, 3α is a liquid crystal molecule, 3β is a dye, 5 is a light shielding layer,
7 is a transparent insulating layer, 8 is a reflective mirror, 9 is a photoconductive layer, 9a is a base layer, or a P layer or a transparent insulating layer, 9
b is an i layer, 9c is an n layer, 10 is a polarizing plate, 101 is a screen, 102 is a halogen lamp, 103,
108 is a condensing lens, 104 is a projection light reflecting mirror, 105 is a projected image magnifying lens, 106 is a light valve device, 107 is a polygon mirror, and 109 is a laser oscillation source.

Claims (1)

[Scope of Claims] 1. A photoconductive layer having a rectifying property is arranged between the substrate and the liquid crystal layer, and a DC voltage is applied in a direction opposite to the rectifying property of the photoconductive layer. means for forming a projection image based on the liquid crystal layer by projecting a writing optical signal onto the photoconductive layer under applied conditions; and a means for erasing the projected image, wherein the photoconductive layer is formed of an n layer and an i layer, and a reflecting mirror is provided on the n layer.