JPH05119342A - Liquid crystal light valve - Google Patents

Abstract

PURPOSE:To provide a liquid crystal light valve which can form a high-contrast image by increasing the on-off voltage ratio of a liquid crystal layer in a bright state and a dark state. CONSTITUTION:This liquid crystal light valve has glass substrates 11a and 11b, transparent electrodes 12a and 12b consisting of lamination of transparent conductive films of ITO and transparent conductive films of SnO2, a photoconductor layer 13, an insulator layer 13a, a light shielding layer 14, a dielectric mirror 15, oriented films 16a and 16b, a sealing material 17, and the liquid crystal layer 18. The photoconductor layer 13 and the insulator layer 13a are formed alternately to the surfaces of the glass substrates 11a and 11b. The photoconductor layer 13 consisting of amorphous hydrogenated silicon oxide enclosed by the insulator layer 13a consisting of amorphous hydrogenated silicon oxide and the oriented film 16a are formed on the transparent electrode 12a. The glass substrates 11a and 11b are stuck to each other via a sealing material 17 and a liquid crystal is injected therebetween, thereafter, the substrates are sealed, by which the liquid crystal layer 18 is formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical writing type liquid crystal light valve.

[0002]

2. Description of the Related Art FIG. 5 is a sectional view showing the structure of a conventional photo-writing type liquid crystal light valve.

As shown in FIG. 1, a conventional optical writing type liquid crystal light valve has transparent glass substrates 71a and 71b.
The transparent electrodes 72a and 72b, the photoconductor layer 73, the light shielding layer 74, the dielectric mirror 75, the alignment films 76a and 76b, the seal member 77 including a spacer, and the liquid crystal layer 78 are provided, and are formed as follows. To be done.

First, ITO is formed on the glass substrates 71a and 71b.
(Indium tin oxide) Transparent conductive film and SnO ₂ (tin oxide)
Transparent electrodes 72a and 72b, each of which is formed by stacking with a transparent conductive film, are formed respectively, and then a photoconductor layer 73 of amorphous silicon hydride (a-Si: H) is formed on one transparent electrode 72a. .. The photoconductor layer 73 made of a-Si: H is formed by using a hydrogen (H ₂ ) gas and a silane (SiH ₄ ) gas as raw materials and using a plasma CVD method (chemical vapor deposition method).

Next, a light shielding layer 74 is formed on the photoconductor layer 73, and a dielectric mirror 75 made of a multilayer film of silicon and silicon oxide is further formed on the light shielding layer 74 by a sputtering method.

Next, the dielectric mirror 75 and the other transparent electrode
72b and a polyimide film is applied by spin coating and baked to form alignment films 76a and 76b, respectively, and after the alignment films 76a and 76b are subjected to a molecular alignment treatment by rubbing, the glass substrates 71a and 71b. Are pasted together via the seal member 77.

A liquid crystal layer is formed by injecting and sealing a mixed nematic liquid crystal containing a chiral material between the glass substrates 71a and 71b bonded together via a seal member 77.
78 is formed, and an optical writing type liquid crystal light valve is formed.

A voltage is applied by an AC power supply 79 between the transparent electrodes 72a and 72b of the liquid crystal light valve having such a structure. Writing light 80a such as a laser beam is scanned from the glass substrate 71a side to write an image. That is, when the writing light 80a is incident, the impedance of the photoconductor layer 73 decreases in the light-exposed region (bright state), and the voltage applied by the AC power supply 79 is applied to the liquid crystal layer 78.
On the other hand, in areas not exposed to light (dark state), the photoconductor layer
The impedance of 73 is not reduced, and a sufficient voltage is not applied to the liquid crystal layer 78 to drive the liquid crystal. Therefore, an image can be formed by changing the impedance of the photoconductor layer 73 in the bright state and the dark state.

When the reading light 80b enters the liquid crystal light valve on which the image is formed from the glass substrate 71b side, the polarization state of the incident light is modulated by the change in the orientation of the liquid crystal layer 78 at the portion corresponding to the image, and the reflection thereof is reflected. An image formed on the liquid crystal light valve can be displayed based on the light.

The operation modes of the liquid crystal light valve are twisted nematic (TN) mode, hybrid electric field effect (HFE) mode and guest host (GH).
Modes and phase transition modes can be used.

[0011]

In such a conventional photo-writing type liquid crystal light valve, the impedance of the photoconductor layer made of a-Si: H in the dark state is similar to that of the liquid crystal layer. Alternatively, it is formed to be smaller than the liquid crystal layer.

Therefore, in order to match the impedance of the photoconductor layer with the impedance of the liquid crystal layer and increase the on-off voltage ratio of the liquid crystal layer in the bright state and the dark state, the photoconductor in the dark state is required. The impedance of the layer should be higher than that of the liquid crystal layer, and the impedance of the photoconductor layer in the bright state should be lower than that of the liquid crystal layer. There is a problem that the thickness of the conductor layer must be increased.

Therefore, the present invention enables a high contrast ratio by increasing the on-off voltage ratio of the liquid crystal layer in the bright state and the dark state without increasing the thickness of the photoconductor layer. A liquid crystal light valve capable of forming an image is provided.

[0014]

A liquid crystal layer provided between two substrates each having an electrode, and an amorphous silicon hydride provided between the liquid crystal layer and one of the two substrates. A photoconductor layer whose impedance changes according to incident light from one side of the two substrates, the photoconductor layer being an insulator formed from amorphous hydrogenated silicon oxide. It is surrounded by.

[0015]

When the light from one side of the two substrates enters,
This incident light changes the impedance of the photoconductor layer. When a voltage is applied between the electrodes of the two substrates, the voltage applied to the liquid crystal layer provided between the two substrates changes due to the change in the impedance of the photoconductor layer, and the alignment state of the liquid crystal changes. An image that changes and is formed according to the incident light is formed. Since the photoconductor layer formed of amorphous silicon hydride is surrounded by the insulator formed of amorphous hydrogenated silicon oxide, the capacitance component of the impedance of the photoconductor layer is therefore reduced. It is possible to reduce the on-off voltage ratio of the liquid crystal layer in the bright state and the dark state, and it is possible to form a high-contrast image.

[0016]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view showing the construction of an embodiment of a photo-writing type liquid crystal light valve according to the present invention.

As shown in the figure, the optical writing type liquid crystal light valve of this embodiment has a transparent glass substrate 11a and a transparent glass substrate 11a.
11b, transparent electrodes 12a and 12b, photoconductor layer 13, insulator layer
13a, light shielding layer 14, dielectric mirror 15, alignment films 16a and 16b
A seal material 17 including a spacer and a liquid crystal layer 18 are provided.

The photoconductor layers 13 and the insulator layers 13a are alternately formed on the surfaces of the glass substrates 11a and 11b.
The photoconductor layer 13 is formed so as to be sandwiched and surrounded by the insulator layer 13a.

This liquid crystal light valve is formed as follows.

First, a transparent electrode 12a formed by stacking an ITO transparent conductive film and a SnO ₂ transparent conductive film on a glass substrate 11a.
Are formed by a sputtering method.

Next, on one transparent electrode 12a, an insulator layer made of amorphous hydrogenated silicon oxide (a-SiO: H).
Amorphous silicon hydride surrounded by 13a (a-S
A photoconductor layer 13 of i: H) is formed. Photoconductor layer
The light shielding layer 14 and the dielectric mirror 15 are provided on the insulating layer 13 and the insulating layer 13a.
And the alignment film 16a is formed.

On the other hand, a transparent electrode 12b formed by stacking an ITO transparent conductive film and a SnO ₂ transparent conductive film on a glass substrate 11b.
Are formed by a sputtering method.

After forming the alignment film 16b on the transparent electrode 12b, the glass substrates 11a and 11b are bonded together via the sealing material 17, and a liquid crystal is injected between the glass substrates 11a and 11b to seal them. A liquid crystal layer 18 is formed.

Next, on the glass substrate 11a on which the transparent electrode 12a is formed, the photoconductor layer 13, the insulator layer 13a, the light shielding layer 14,
A manufacturing method for forming the dielectric mirror 15 and the alignment film 16a will be described.

FIG. 2 is a cross-sectional view of each layer formed on the glass substrate 11a. FIGS. 2 (A) to 2 (E) show the photoconductor layer on the glass substrate 11a having the transparent electrode 12a formed thereon. FIG. 13 is a cross-sectional view of each layer in each step of forming 13, the insulating layer 13a, the light shielding layer 14, the dielectric mirror 15, and the alignment film 16a.

As shown in FIG. 2A, first, the transparent electrode 12
Plasma C is formed on one glass substrate 11a on which a is formed.
The thickness of the photoconductor layer 13 made of a-Si: H was measured by the VD method.
Deposit 3 μm to 10 μm.

Next, as shown in FIG. 2 (B), a resist 21 is applied on the photoconductor layer 13, exposed and patterned. In this embodiment, the resist 21 is patterned to have a size of 4 μm, but the patterning size is 1 μm.
It is preferably m to 20 μm square, and the patterning shape is not limited to a square shape, and may be a rectangular shape, a round shape, or a rhombic shape.

Then, as shown in FIG.
A substrate in which 21 is patterned on the photoconductor layer 13 is doped with oxygen ions (O ⁺ ) by an ion implanter,
Of the a-Si: H portion forming the photoconductor layer 13, the portion without the resist 21 thereon is made into an insulating a-SiO: H to form an insulator layer 13a.

As a result, the insulating layer 13a made of insulating a-SiO: H is selectively formed by ion doping based on the pattern of the resist 21, and the insulating layer 13a is also formed.
By being surrounded by 13a, the photoconductor layer 13 is formed in an island shape.

Then, as shown in FIG.
After stripping 21, the carbon-dispersed organic resin is spin-coated as the light-shielding layer 14, and a multilayer film in which dielectric films of SiO ₂ and TiO ₂ are alternately laminated is formed by electron beam evaporation as the dielectric mirror 15.

Next, as shown in FIG. 2 (E), a polyimide film is applied as an alignment film 16a on the formed dielectric mirror 15 by spin coating, baked, and subjected to an alignment treatment such as rubbing. Forming a substrate.

The other substrate facing this is, as shown in FIG. 1, the other glass substrate 11 on which the transparent electrode 12b is formed.
On b, a polyimide film as an alignment film 16b is applied by a spin coating method, baked, and rubbed, and then a sealing material 17 is formed, which is bonded to one of the above substrates, and then liquid crystal is vacuum-injected and sealed. By doing so, the liquid crystal layer 18 is formed. In this way, an optical writing type liquid crystal light valve is formed.

A voltage is applied by an AC power supply 19 between the transparent electrodes 12a and 12b of the liquid crystal light valve having such a structure. Writing light 20a such as a laser beam is scanned from the glass substrate 11a side to write an image. That is, when the writing light 20a is incident, the impedance of the photoconductor layer 13 decreases in the light-exposed region (bright state), and the voltage applied by the AC power supply 19 is applied to the liquid crystal layer 18.
On the other hand, in areas not exposed to light (dark state), the photoconductor layer
The impedance of 13 is not reduced, and a sufficient voltage to drive the liquid crystal is not applied to the liquid crystal layer 18. Therefore, an image can be formed by changing the impedance of the photoconductor layer 13 between the bright state and the dark state.

When the readout light 20b enters the liquid crystal light valve on which the image is formed in this way from the glass substrate 11b side, the polarization state of the incident light is modulated by the change in the orientation of the liquid crystal layer 18 at the portion corresponding to the image, and the reflection thereof is reflected. An image formed on the liquid crystal light valve can be displayed based on the light.

As the operation mode of this liquid crystal light valve, a TN mode, an HFE mode, a GH mode, a phase transition mode and the like can be used.

In the conventional photo-writing type liquid crystal light valve, since the photoconductor layer is laminated on the entire surface of the transparent electrode, the impedance of the photoconductor layer in the dark state (parallel circuit of capacitance and resistance) is It does not become large enough for the liquid crystal layer. However, in the above-described embodiment, by forming the photoconductor layer in an island shape and surrounding it with an insulator layer,
Since the capacitance component of the impedance of the photoconductor layer can be reduced, the impedance of the photoconductor layer can be made sufficiently larger than the impedance of the liquid crystal layer in the dark state.

Therefore, by providing the insulator layer around the photoconductor layer, the capacitance component of the impedance of the photoconductor layer can be reduced, and the impedance of the photoconductor layer and the impedance of the liquid crystal layer can be easily matched. Become. That is, since it becomes possible to apply a voltage having a sufficiently large on-off voltage ratio to the liquid crystal layer, a high-contrast image can be formed. Also, since it is not necessary to increase the thickness of the photoconductor layer in order to form a high-contrast image,
The manufacturing margin can be increased.

Next, another embodiment of the photo-writing type liquid crystal light valve according to the present invention will be described.

FIG. 3 is a sectional view showing the construction of another embodiment of the optically writable liquid crystal light valve according to the present invention.

As shown in the figure, the optical writing type liquid crystal light valve of this embodiment has a transparent glass substrate 31a and a transparent glass substrate 31a.
31b, transparent electrodes 32a and 32b, photoconductor layer 33, insulator layer
33a, a metal electrode 34a, alignment films 35a and 35b, a sealant 36 including a spacer, and a liquid crystal layer 37.

The photoconductor layers 33 and the insulator layers 33a are alternately formed on the surfaces of the glass substrates 31a and 31b.
The photoconductor layer 33 is formed so as to be sandwiched and surrounded by the insulator layers 33a.

This liquid crystal light valve is formed as follows.

First, a transparent electrode 32a formed by laminating an ITO transparent conductive film and a SnO ₂ transparent conductive film on a glass substrate 31a.
Are formed by a sputtering method.

Next, a-Si is formed on one transparent electrode 32a.
A-S surrounded by an insulator layer 33a composed of O: H
A photoconductor layer 33 of i: H is formed. Photoconductor layer 33
A metal electrode 34a, which also functions as a light-shielding layer and a dielectric mirror, is formed in the shape of an island on the upper side, and the metal electrode 34a is formed on the insulator layer 33a.
An alignment film 35a is formed so as to surround 34a.

On the other hand, a transparent electrode 32b formed by stacking an ITO transparent conductive film and a SnO ₂ transparent conductive film on a glass substrate 31b.
Are formed by a sputtering method.

After the alignment film 35b is formed on the transparent electrode 32b, the glass substrates 31a and 31b are bonded together via the sealing material 36, and liquid crystal is injected between the glass substrates 31a and 31b to seal them. A liquid crystal layer 37 is formed.

Next, on the glass substrate 31a on which the transparent electrode 32a is formed, the photoconductor layer 33, the insulator layer 33a and the metal electrode are formed.
A manufacturing method for forming 34a will be described.

FIG. 4 is a cross-sectional view of each layer formed on the glass substrate 31a. FIGS. 4 (A) to 4 (F) show the photoconductor layer on the glass substrate 31a on which the transparent electrode 32a is formed. FIG. 6B is a cross-sectional view of each layer in each step of forming 33, the insulator layer 33a, and the metal electrode 34a.

As shown in FIG. 4A, first, the transparent electrode 32
Plasma C is formed on one glass substrate 31a on which a is formed.
The thickness of the photoconductor layer 33 made of a-Si: H is determined by the VD method.
Deposit 3 μm to 10 μm.

Next, as shown in FIG. 4B, a metal layer 34 made of aluminum (Al) is vapor-deposited on the photoconductor layer 33 by an electron beam vapor deposition method.

Next, as shown in FIG. 4C, the metal layer 34
A resist 42 is applied on the surface and exposed to form a rectangular pattern. In this embodiment, Al is used as the metal layer 34, but other metals (for example, Mo (molybdenum) and Ta are used.
(Tantalum) and the like) may be used.

Then, as shown in FIG. 4D, the metal layer 34
Is peeled off with an aluminum etchant and patterned to form an island-shaped metal electrode 34a and an island-shaped resist 42.

Next, as shown in FIG. 4 (E), the substrate on which the metal electrode 34a and the resist 42 are formed on the photoconductor layer 33 is doped with oxygen ions (O ⁺ ) by an ion implanter, Of the a-Si: H forming the photoconductor layer 33, a portion without the island-shaped metal electrode 34a and the island-shaped resist 42 thereon is made into an insulating a-SiO: H, whereby the insulator layer is formed. Forming 33a.

As a result, an insulating a-SiO: H insulating layer 33a is selectively formed by ion doping based on the pattern of the metal electrode 34a and the resist 42, and is surrounded by the insulating layer 33a. Photoconductive layer
It means that 33 are formed like islands.

Then, as shown in FIG. 4 (F), the metal electrode
After removing the resist 42 formed on the 34a, the alignment film
One substrate is formed by applying a polyimide film as 35a by a spin coating method, baking it, and rubbing it.

The other substrate facing this is, as shown in FIG. 3, the other glass substrate 31 on which the transparent electrode 32b is formed.
On b, a polyimide film is applied as an alignment film 35b by a spin coating method, baked, and rubbed, and then a sealing material 36 is formed, which is bonded to one of the above substrates, and then liquid crystal is vacuum injected and sealed. By doing so, the liquid crystal layer 37 is formed. In this way, an optical writing type liquid crystal light valve is formed.

A voltage is applied by the AC power source 38 between the transparent electrodes 32a and 32b of the liquid crystal light valve having such a structure. Writing light 40a such as a laser beam is scanned from the glass substrate 31b side to write an image. That is, when the writing light 40a is incident, the impedance of the photoconductor layer 33 decreases in the light-exposed region (bright state), and the voltage applied by the AC power supply 38 is applied to the liquid crystal layer 37.
On the other hand, in areas not exposed to light (dark state), the photoconductor layer
The impedance of 33 does not decrease and the liquid crystal layer 37 does not receive sufficient voltage to drive the liquid crystal. Therefore, an image can be formed by changing the impedance of the photoconductor layer 33 between the bright state and the dark state.

When the read light 40b enters the liquid crystal light valve on which the image is formed from the glass substrate 31b side, the polarization state of the incident light is modulated by the change in the orientation of the liquid crystal layer 37 at the portion corresponding to the image, and the reflection thereof is reflected. An image formed on the liquid crystal light valve can be displayed based on the light.

As the operation mode of this liquid crystal light valve, TN mode, HFE mode, GH mode, phase transition mode and the like can be used.

In the conventional photo-writing type liquid crystal light valve, since the photoconductor layer is laminated on the entire surface of the transparent electrode, the impedance (parallel circuit of capacitance and resistance) of the photoconductor layer in the dark state is It does not become large enough for the liquid crystal layer. However, in the above-described embodiment, the photoconductor layer is formed in an island shape and the surroundings are surrounded by the insulator, so that the capacitance component of the impedance of the photoconductor layer can be reduced, and thus the photoconductor layer in the dark state. Can be made sufficiently higher than the impedance of the liquid crystal layer.

Therefore, since the photoconductor layer made of a-Si: H is surrounded by the insulator layer made of a-SiO: H, the capacitance component of the impedance of the photoconductor layer can be reduced and the liquid crystal layer. It is possible to apply a voltage having a sufficiently large on-off voltage ratio. Therefore, an optical change in the liquid crystal layer can be sufficiently caused, and a high-contrast image can be formed. Further, since it is not necessary to increase the thickness of the photoconductor layer in order to form a high-contrast image, it is possible to increase the manufacturing margin.

Although oxygen ions are doped in the above embodiments, the insulator layer may be formed by doping nitrogen ions.

[0064]

As described above, according to the present invention, a liquid crystal layer provided between two substrates each having an electrode and a liquid crystal layer provided between the liquid crystal layer and one of the two substrates are provided. A photoconductor layer formed of amorphous silicon hydride, the impedance of which is changed by incident light from one side of the two substrates; It is surrounded by the formed insulator. Therefore, the capacitance component of the impedance of the photoconductor layer can be reduced, the on-off voltage ratio of the liquid crystal layer in the bright state and the dark state can be increased, and a high-contrast image can be formed.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing the configuration of an embodiment of a photo-writing type liquid crystal light valve according to the present invention.

FIG. 2 is a cross-sectional view of each layer formed on a glass substrate.

FIG. 3 is a cross-sectional view showing the configuration of another embodiment of the optically writable liquid crystal light valve according to the present invention.

FIG. 4 is a cross-sectional view of each layer formed on a glass substrate.

FIG. 5 is a cross-sectional view showing a configuration of a conventional optical writing type liquid crystal light valve.

[Explanation of symbols]

 11a, 11b, 31a, 31b Glass substrate 12a, 12b, 32a, 32b Transparent electrode 13, 33 Photoconductor layer 13a, 33a Insulator layer 14 Light-shielding layer 15 Dielectric mirror 16a, 16b, 35a, 35b Alignment film 18, 37 Liquid crystal layer 34a Metal electrode

Claims (2)

[Claims] 1. A liquid crystal layer provided between two substrates each having an electrode, formed from amorphous silicon hydride and provided between the liquid crystal layer and one of the two substrates. And a photoconductor layer whose impedance is changed by incident light from one side of the two substrates, the photoconductor layer being formed of amorphous silicon hydrooxide. Liquid crystal light valve characterized by being surrounded by. 2. The liquid crystal light valve according to claim 1, wherein the insulator is formed by selectively ion-doping the photoconductor layer.