JPH09197432A - Optical writing type liquid crystal light valve - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the thickness of a photoconductive layer and to make production simpler, efficiency higher, mass productivity higher, cost lower and thickness and weight smaller by arranging intermediate electrodes across the photoconductive layer so as to face first transparent electrodes. SOLUTION: First transparent substrates 1, 9 deposited and formed respectively with the transparent electrodes 2, 8 on the one-side surfaces are disposed to face each other in such a manner that the respective transparent electrodes 2, 8 exist on the inner side. The photoconductive part 20 and liquid crystal part 21 are laminated and arranged therebetween. The photoconductive part 20 is constituted by laminating the photoconductive layers 3 deposited and formed on the transparent electrodes 2 formed on the first substrate 1 and the intermediate electrodes 4 formed on these photoconductive layers 3. The patterns of the intermediate electrodes 4 are formed as the patterns divided by, for example, each of respective pixels of the optical writing type liquid crystal light valve to be finally constituted. The patterns arranged with island-shaped dividing parts of a square shape on, for example, rows and columns intersecting orthogonally with each other are formed. In such a case, the respective stripe parts of the transparent electrodes 2 are formed in the island-shaped dividing parts on the respective columns of the intermediate electrodes 4 along their central parts.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a photo-writing type liquid crystal light valve.

[0002]

2. Description of the Related Art The basic theory of light valve technology is described in US Pat. No. 3,824,002 and US Pat.
Which is disclosed in the specification of No. 9,807,
The basic construction of an AC light valve is disclosed in the former patent specification.

As shown in FIG. 5, a liquid crystal light valve has two transparent first electrodes made of, for example, glass and having first and second transparent electrodes 31 and 38 formed on the inner surfaces thereof.
A thin film multi-layer structure including a liquid crystal layer 37, a dielectric reflection film 36, a light absorption layer 35, and a photoconductive layer 32 is sandwiched between the second substrates 30 and 39.

This liquid crystal light valve is an element for writing, displaying, and erasing two-dimensional information such as an image and patterned data in real time by spatially modulating the intensity, phase or traveling direction of light. .

Then, xenon laser is applied from the second substrate 39 side.
Light L from a light source such as a pump_RIntroduced the dielectric
It is reflected by the reflective film 36 and is forwarded from the second substrate 39 side.
It is made to go toward. On the other hand, the first substrate 30 side
Writing light L for input video, etc. _WAre introduced into the photoconductive layer 32.
And the input image, etc. that is incident on each part of the photoconductive layer 32.
Of the photoconductive layer 32 generated according to the light intensity of the imprint pattern.
Both transparent electrodes 31 are formed on the liquid crystal layer 37 with a conductive pattern.
And 38 apply a voltage, which causes the liquid
The so-called optical switch operation of the crystal layer 37 is performed, and reading is performed.
Light L_RThe polarization is modulated and read according to the input image
Light L_RThe output light from the reflected light of
Enlarge through a required optical system on a screen (not shown)
It is designed to be projected.

By the way, in this type of liquid crystal light valve, each of the liquid crystal layer 37, the dielectric reflection film 36, the light absorption layer 35, and the photoconductive layer 32 described above has a relatively high surface resistance. These do not employ a structure in which they are separated in the plane direction, that is, a structure in which they are divided for each pixel unit, for example.

In this liquid crystal light valve, the photoconductive layer 32 is made of, for example, amorphous silicon, and the photoconductive layer 32 is formed to be considerably thick. This is to increase the impedance associated with the photoconductive layer 32.

This will be described. FIG. 4 is an equivalent circuit of the liquid crystal light valve. That is, each layer including the photoconductive layer and the liquid crystal layer forming the liquid crystal light valve has an impedance Z including a resistance component R and a capacitance component C, respectively. However, it is the photoconductive layer and the liquid crystal layer that have a great influence on the driving of the liquid crystal, and the other layers can be ignored.

In FIG. 4, Z₁Is the impedance of the photoconductive layer
Dance, R₁And C₁Is the resistance component and
And capacity component. Also, Z_Two Is the impedance of the liquid crystal layer
Su, R_Two And C_Two Is the resistance component and
It is a quantitative component. And when there is no writing light,
In the dark state, the resistance component R of the photoconductive layer₁High in
Peedance Z₁Is large, the voltage applied to the liquid crystal layer is
Pressure V_TwoControl this voltage V_Two But photoconductive layer and liquid
V with respect to the voltage V applied to both ends of the crystal layer_Two << V
The threshold voltage for switching on the liquid crystal layer
Lower voltage V _Two Are applied to the liquid crystal layer. So
Then, in the state where the writing light is introduced, the R of the photoconductive layer is
₁Is small, the impedance Z₁Decreases
The voltage V applied to the liquid crystal layer_TwoApproaches the voltage V,
This is the ON state. Therefore, this place
Impedance Z in darkness₁Must be large
For this reason, the photoconductivity in the liquid crystal light valve described above
In order to increase the dark resistance in the thickness direction of the layer 32, this
For example, an amorphous silicon film forming the photoconductive layer 32
Is quite thick, for example, 10μm or more
ing.

[0010]

However, increasing the film thickness of the photoconductive layer 32, for example, the film thickness of the amorphous silicon layer, in fact, makes the film forming time extremely long, which leads to mass productivity. This hinders the production cost.

Further, when the film thickness of the photoconductive layer 32 is set to, for example, 10 μm or more, there is a problem that the panel of the liquid crystal light valve is warped. Accordingly, the first and second substrates 30
And 39 need to be considered.
For this reason, the thickness and weight of the entire liquid crystal light valve are increased, which hinders reduction in size and weight.

By the way, it is known that in a light valve using a ferroelectric liquid crystal, the film thickness of the photoconductive layer 32 can be made small and the spatial resolution is improved, but analog gradation and high reliability are realized. Those that can be used to display images have not been put to practical use.

In order to solve the above-mentioned problems, the present invention aims to reduce the thickness of the photoconductive layer in a photo-writing type liquid crystal light valve to simplify the manufacturing, improve the efficiency, improve the mass productivity, and reduce the cost. It is possible to reduce the thickness of the substrate and the thickness of the substrate, and to realize the reduction in thickness and weight.

[0014]

A photo-writing type liquid crystal light valve according to the present invention comprises a photoconductive layer disposed between a first transparent electrode and a second transparent electrode in contact with the first transparent electrode. A layer, an intermediate electrode arranged to face the first transparent electrode with the photoconductive layer sandwiched therebetween, a dielectric reflection film, and a liquid crystal layer are interposed.

In the present invention, by providing the intermediate electrode as described above, it becomes possible to divide the surface direction, so to speak, as will be described later, so that the drawing of each part is substantially achieved. The capacitance component C ₁ in the equivalent circuit shown in FIG. 4 can be reduced so that the impedance Z _{1 of the} photoconductive layer can be sufficiently maintained even if the resistance component R ₁ is reduced. The thickness of the photoconductive layer can be reduced to 1/10 of the conventional one.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of a photo-writing type liquid crystal light valve according to the present invention will be described. An example of the optically writable liquid crystal light valve according to the present invention will be described with reference to FIG. FIG.
[Fig. 3] is a schematic perspective view of a main part disclosed by cutting out a part thereof as a cross section.

The optically writable liquid crystal light valve is made of, for example, a glass substrate or the like, and has first and second transparent electrodes 2 and 8 formed on one surface of the first and second substrates 1, respectively. And 9, that is, the respective substrates face each other with their respective transparent electrodes facing inward, and the photoconductive portion 20 and the liquid crystal portion 21 are laminated and arranged between the first and second substrates 1 and 9.

The photoconductive portion 20 is a photoconductive layer 3 formed by deposition on the first transparent electrode 2 formed on the first substrate 1.
And the intermediate electrode 4 formed on the photoconductive layer 3 are laminated.

The first transparent electrode 2 has, for example, a pattern in which a plurality of stripe portions 2s are arranged in parallel on the effective screen portion.
It is formed. The first transparent electrode 2 has, for example, an indium tin oxide film, which is a so-called ITO film, having a thickness of 200 nm formed on the entire surface of the substrate 1, and has a predetermined width and a predetermined space by pattern etching by photolithography. It is assumed that the stripe portions 2s are arranged and formed.

The photoconductive layer 3 is formed by depositing, for example, amorphous silicon on the first transparent electrode 2 by plasma CV to a required thickness.
It is formed by a D (Chemical Vapor Deposition) method or the like.

For the intermediate electrode 4, a mask layer having a predetermined pattern corresponding to the pattern of the intermediate electrode 4 to be finally formed is formed on the photoconductive layer 3, and Al is deposited thereon, for example, 0.1 μm.
A layer having a thickness of about m is vapor-deposited on the entire surface, and the mask layer is removed by the solvent to form a predetermined pattern by a so-called lift-off method. The pattern of the intermediate electrode 4 is, for example, a pattern divided for each pixel in the photo-writing liquid crystal light valve that is finally formed. The intermediate layer 4 has, for example, a pattern in which a plurality of, for example, rectangular island-shaped divided portions are arranged on a plurality of rows and columns that are orthogonal to each other. Each island-shaped divided portion of the intermediate electrode 4 has, for example, each side having a size of, for example, about 32 μm, and an interval between adjacent island-shaped divided portions is selected to be 3 μm.

In this case, the stripe portions of the first transparent electrode 2 described above are arranged, for example, in common columns of the intermediate electrodes 4 in islands arranged on these columns, as shown in FIG. The photoconductive layer 3 is formed so as to face each other along the central portion of the divided portion. The stripes of the first transparent electrode 2 are connected to each other at both ends thereof.

The width of each stripe portion of the first transparent electrode 2 is, for example, 4 μm, which is smaller than the width of the island-shaped divided portion of the intermediate electrode 4, for example, 4 μm.
For example, it is selected to be 35 μm. In this way, the transparent electrode 2 is configured to face the area of each part of each island-shaped divided portion of the intermediate electrode 4.

On the photoconductive portion 20, the above-mentioned liquid crystal portion 21 is provided.
Are laminated. The liquid crystal part 21 includes a light absorption layer 5 formed on the intermediate electrode 4, a dielectric reflection film 6 formed on the light absorption layer 5, and a liquid crystal layer 7 arranged on the dielectric reflection film 6. , The liquid crystal layer 7 is the second transparent electrode 8 of the second substrate 9.
It is arranged so that it may contact. That is, the photoconductive portion 20
The light absorption layer 5 and the dielectric reflection film 6 are laminated on the intermediate electrode 4.

The dielectric reflection film 6 may be constructed by alternately laminating two or more high refractive index material layers and low refractive index material layers.

Each of the light absorbing layer 5 and the dielectric reflecting film 6 can be formed by, for example, electron beam evaporation.

A liquid crystal alignment layer (not shown) is formed on the dielectric reflection film 6 thus formed on the first substrate 1 side, and the other second substrate 9 is required for this. A liquid-tight flat space is formed between the two while facing each other with a space therebetween, and liquid crystal is injected into the space to form the liquid crystal layer 7.

The liquid crystal forming the liquid crystal layer 7 can be composed of, for example, nematic liquid crystal or ferroelectric liquid crystal.

In the photo-writing type liquid crystal light valve having this structure, the liquid crystal part 2 is provided between the first and second transparent electrodes 2 and 8.
1 and a photoconductive portion 20 to provide a voltage signal that produces an alternating current. The writing light L _W is made incident from the first substrate 1 side, and the reading light L _R is made incident from the second substrate 9 side. In this case, an optical address is made by the writing light L _W , and the electric resistance of the photoconductive layer 3 is changed by this, so that a voltage pattern corresponding to this pattern can be obtained. In this case, since the intermediate electrode 3 is provided and each pixel is divided into islands and segmented, the segment is divided between the first transparent electrode 2 and the second transparent electrode 8, that is, in the liquid crystal layer. , The liquid crystal layer 7 is controlled by a potential pattern corresponding to the pattern of the input write light L _W by applying a required potential, and the read light L _R incident on this is polarized and modulated. Therefore, by this modulation, according to the writing light pattern,
A readout light pattern is obtained, which is magnified and projected on a screen, for example.

In the above-mentioned photo-writing type liquid crystal light valve according to the present invention, the first transparent electrode 2 with the photoconductive layer 4 interposed therebetween.
Since the intermediate electrode 4 is provided on the side opposite to, and the transparent electrode 2 is divided for each pixel, and the transparent electrode 2 is made to face the divided portion of each pixel with a smaller area than that, The capacity in each division can be made small.
That is, since it is possible to reduce the substantial impedance related to each divided portion in the equivalent circuit shown in FIG. 4, in order to obtain the same impedance, the resistance component R ₁
Can be reduced. That is, in the above-mentioned structure, the thickness of the photoconductive layer 3 is set to, for example, 1/10 of the conventional thickness.
Can be

Further, by providing the segmented (divided) intermediate electrode 4, the photoconductive portion 20 is improved and the light absorption layer 5 can be simplified. That is, when the intermediate electrode 4 is made of, for example, an aluminum film, the aluminum film has a reflectance of 85% or more in the visible light region, and therefore the thickness of the light absorption layer 5 is reduced or the film structure is simplified. Can be changed.

In the above example, the intermediate electrode 4 is divided, that is, segmented for each pixel. However, when the surface resistance of the intermediate electrode 4 is sufficiently large, it is divided. It may be omitted, or common to a plurality of pixels.

Further, in the above structure, the first transparent electrode 2
Is segmented into stripes in the effective screen portion, but other patterns can be used.

In the above-mentioned photo-writing type liquid crystal light valve, the photoconductive layer 3 is formed entirely on the surface of the first substrate 1, but the present invention is not limited to this example. , A first transparent electrode 2 segmented with a photoconductive layer 3
It is also possible to adopt a configuration that exists only above.

FIG. 3 shows a schematic sectional view of a liquid crystal light valve having this structure. In this case, the photoconductive layer 3 is provided only on the segmented first transparent electrode 2, and the insulating layer 13 is provided on the other portion. Then, similarly to the example described in FIG. 1, an aluminum film, for example, which becomes the grid-shaped segmented intermediate electrode 14 is laminated thereon,
The photoconductive portion 20 is formed.

In this device, first, an insulating layer 13 is vapor-deposited on a first substrate 1 made of, for example, glass, patterned by a stripe-shaped mask, and a predetermined pattern is formed by dry etching or wet etching.

Next, by the same steps as in the above-mentioned example, the first
Indium tin oxide as the transparent electrode 2 and amorphous silicon as the photoconductive layer 3 are laminated in stripes.

Finally, after a lift-off process, the photoconductive layer 3
Is completed. The following steps can be performed in the same manner as described above. By taking this structure,
It is possible to further reduce the size of the device. FIG.
In FIG. 5, the same reference numerals are given to the portions corresponding to those in FIG.

[0039]

By incorporating the above-described structure in the photoconductive portion 20, the reproducibility of the input image can be achieved, and the lateral drift of the signal charge and the deterioration of the resolution due to the diffusion can be prevented. It was Further, since the thickness of the photoconductive layer 3 can be reduced, it is not necessary to have a structure for preventing the warpage of the entire device. Further, it is possible to reduce the time for stacking, for example, amorphous silicon that constitutes the photoconductive layer 3 and the cost of materials. Also,
By providing the intermediate electrode 4, the structure of the light absorption layer 5 can be simplified. As described above, the cost for manufacturing the liquid crystal light valve can be reduced, and the size and weight of the entire device can be reduced. Further, in the liquid crystal valve using the ferroelectric liquid crystal, the film thickness of the photoconductive layer was reduced, and the spatial resolution could be improved.

[Brief description of drawings]

FIG. 1 is a schematic perspective view of an optical writing type optical liquid crystal valve according to the present invention.

FIG. 2 is a view showing the alignment between the segmented first transparent electrode and the aluminum film constituting the intermediate electrode in the photoconductive portion of the photo-writing optical liquid crystal valve according to the present invention.

FIG. 3 is a schematic sectional view of an optical writing type optical liquid crystal valve of another embodiment of the present invention.

FIG. 4 is a diagram showing an equivalent circuit of the present invention and the conventional optical writing type optical liquid crystal valve.

FIG. 5 is a schematic cross-sectional view of a conventional photo-writing optical liquid crystal valve.

[Explanation of symbols]

1 First Substrate 2 First Transparent Electrode 3 Photoconductive Layer 4 Intermediate Electrode 5 Light Absorbing Layer 6 Dielectric Reflective Film 7 Liquid Crystal Layer 8 Second Transparent Electrode 9 Second Substrate 13 Insulating Layer 20 Photoconductive Part 21 Liquid Crystal Part V ₁ Voltage applied to photoconductive layer V ₂ Voltage applied to liquid crystal layer Z ₁ Impedance of photoconductive layer Z ₂ Impedance of liquid crystal layer R ₁ Resistance component of impedance Z ₁ R ₂ Impedance component of impedance Z ₂ C ₁ Impedance Z ₁ Capacitor component of C ₂ Impedance Z ₂ capacitor component

Claims (4)

[Claims] 1. A photoconductive layer disposed between the first transparent electrode and a second transparent electrode so as to be in contact with the first transparent electrode, and the first conductive layer sandwiching the photoconductive layer. An optical writing type liquid crystal light valve, characterized in that an intermediate electrode arranged to face the transparent electrode, a dielectric reflection film, and a liquid crystal layer are interposed. 2. The photo-writing type liquid crystal light valve according to claim 1, wherein the intermediate electrode is divided for each pixel. 3. The photo-writing liquid crystal according to claim 2, wherein the first transparent electrode is patterned so as to face each part of each of the divided electrodes of the intermediate electrode. Light bulb. 4. The photo-writing type liquid crystal light valve according to claim 1, wherein the photoconductive layer is divided into a plurality of parts.