JPH03200934A - Optical writing type liquid crystal display element - Google Patents

Abstract

PURPOSE:To obtain a good resolving power by incorporating films consisting of an amorphous silicon system into at least either of light absorptive layers and dielectric layers. CONSTITUTION:The films of the amorphous silicon system are incorporated into at least either of the light absorptive layers 5 and dielectric layers 6 formed on a photoconductor layer 4 on a 1st transparent electrode layer 3. Layers l1 consisting of amorphous hydrogenated silicon carbide (a-Si1-xCx:H) and layers l2 consisting of the amorphous hydrogenated silicon carbide (a-Si1-x'Cx': H) of the compsn. varying from the compsn. of the layers l1 are alternately laminated as the dielectric layers 6. The resolving power of the optical writing type liquid crystal display element 1 is improved in this way and the process is simplified.

Description

[Detailed description of the invention] [Industrial application fields] The present invention relates to an optical writing type liquid crystal display element.

[Prior Art] A conventional optical writing type liquid crystal display element is formed on one transparent electrode, and is made of amorphous hydrogenated silicon (a-Si:
a photoconductor layer formed on the photoconductor layer and formed on the photoconductor layer and patterned with a thin film of metal such as carbon or silver; A stacked layer including a dielectric mirror made of a multilayer film of silicon dioxide, zinc sulfide/magnesium fluoride, etc. is provided between one glass substrate and one alignment film.

[Problems to be Solved by the Invention] In conventional optical writing type liquid crystal display elements, the light absorption layer is made of a metal film such as carbon or silver, or the dielectric mirror layer is made of titanium dioxide/silicon dioxide, zinc sulfide/fluoride, etc. Since it is made of a multilayer film made of magnesium chloride or the like, the resolution of the optical writing type liquid crystal display element is not good.

In addition, conventional optical writing type liquid crystal display elements have the following problems.

Because the adhesion between the metal film such as carbon or silver that constitutes the light absorption layer and the amorphous hydrogenated silicon (a-5i: +1) that constitutes the photoconductor layer is not good, the light absorption layer and the Peeling from the conductor layer is likely to occur.

Furthermore, for example, when forming a dielectric mirror layer by alternately stacking a large number of zinc sulfide films and magnesium fluoride films, the steps of forming a zinc sulfide film and a stage of forming a magnesium fluoride film are sequentially repeated. , it is necessary to change the raw material of the film at each formation step, which considerably complicates the fabrication process of the dielectric mirror layer.

An object of the present invention is to provide an optical writing type liquid crystal display element that can provide good resolution.

[Means for Solving the Problems] According to the present invention, the above-mentioned object includes a first transparent substrate, a first transparent electrode layer formed on the first transparent substrate, and a first transparent electrode layer formed on the first transparent substrate.
a photoconductor layer formed on the transparent electrode layer; a light absorption layer formed on the photoconductor layer; a dielectric layer formed on the light absorption layer; a second transparent substrate; a second transparent electrode layer formed on the second transparent substrate; and a liquid crystal layer inserted between the second transparent electrode layer and the dielectric layer, and at least one of the light absorption layer and the dielectric layer. This is achieved by an optically writable liquid crystal display element characterized by including an amorphous silicon-based film.

[Function] According to the present invention, since at least one of the light absorption layer and the dielectric layer includes an amorphous silicon film, the resolution of the optical writing type liquid crystal display element can be improved.

[Embodiments] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.

The optical writing type liquid crystal display element l which is the first embodiment of the present invention shown in FIG. A transparent electrode 3 constituting a first transparent electrode layer made of a stack of SnO2 transparent conductive films, and a transparent electrode 3 formed on the electrode 3,
Film thickness 3 made of amorphous hydrogenated silicon (a-3i:H)
a photoconductor layer 4 with a thickness of 0.2 μm and a light absorption layer 5 formed on the photoconductor layer 4 and made of amorphous silicon hydride (a-3iSn:H); Formed on the light absorption 85 is a layer j! of amorphous hydrogenated silicon carbide (a-8i C:H), as shown in FIG. l and layer 11-1! Amorphous hydrogenated silicon carbide F-3114 with a different composition from 1
The dielectric layer 6 has a multilayer structure (FIG. 3) with a total thickness of 1.3 μm, in which 17 layers of layers 12 consisting of +Cy, -・H) are stacked alternately, and the dielectric layer 6 is formed on the dielectric layer 6. one alignment film 7, a glass substrate 8 as a second transparent substrate, and a substrate 8.
A transparent electrode 9 is formed on the top and constitutes a second transparent electrode layer consisting of a laminated layer of an ITO transparent conductive film and a Sn02 transparent conductive film, the other alignment film 10 formed on the electrode 9, and the alignment film means for sealing the substrate 2 and the substrate 8 via the spacer II so that the substrate 7 and the alignment film 10 face each other with an interval of about 6 μm; , and a liquid crystal layer 12 made of mixed nematic liquid crystal or ferroelectric liquid crystal to which a chiral material is added. A voltage is applied between electrode 3 and electrode 9 by AC power supply 13 .

The light absorption layer 5 prevents the laser light L1 used for writing from being reflected by the dielectric layer 6 and entering the photoconductor layer 4 again.

The light absorption layer 5 is made of amorphous silicon hydride (a-3iSn
:H), the resolution of the optical writing type liquid crystal display element 1 can be improved. It has excellent adhesion and is resistant to peeling.

The dielectric layer 6 reflects the read light R1 incident on the dielectric layer 6 with a high reflectance and sends it back as reflected read light R2 in a direction opposite to the direction of incidence.

The dielectric layer 6 is made of amorphous hydrogenated silicon carbide (a-5i,
C, :H) and a layer j consisting of amorphous hydrogenated silicon carbide (a-5i + Cr +H), which has a different composition from layer Jl! 2 and 1-! ! Since it is layered, the resolution of the optically writable liquid crystal display element 1 can be improved, and in addition, the manufacturing process of the dielectric M6 can be simplified. A detailed explanation of the structure of the dielectric layer 6 will be given later.

FIG. 2 shows an example of a projection type display device using the liquid crystal display element 1 of the first embodiment configured as described above as a liquid crystal light valve. The operation of the projection type display device and the operation of the first embodiment will be explained with reference to FIGS. 1 and 2.

When the laser beam L1 enters from the substrate 2 side, the photoconductor layer 4
The impedance decreases in the area of the photoconductor 714 that is hit by the light, and the voltage applied to the electrode 3.9 by the AC power supply 13 is applied to the area of the liquid crystal Mi12 that corresponds to the area of the photoconductor 714 that is hit by the light. The added region of the liquid crystal layer 12 changes its alignment state and becomes bright. On the other hand, the areas of the photoconductor layer 4 that are not hit by light do not cause any change in impedance, and no voltage is applied to the areas of the liquid crystal layer 12 that correspond to the areas that are not hit by the light. The initial orientation state is maintained and the state becomes dark. An image is formed on the liquid crystal layer 12 due to the difference between the bright state and the dark state.

When the reading light from the lamp 20 enters the polarizing beam splitter 23 through the lens 21 on the optical writing type liquid crystal display element 1 on which an image has been formed in this way, this incident reading light is transmitted to the liquid crystal display element 1 by the splitter 23. reflected towards. This incident reading light (R1) is reflected by the dielectric layer 6, and this reflected reading light (R2
), the reflected reading light that passes through the portion where the orientation state of the liquid crystal layer 12 is changed (bright state) by the laser light 25 passing through the lens 24 is transmitted through the polarizing beam splitter 23 because the polarization direction changes due to the electro-optic effect. do.

The reflected reading light (R2) transmitted in this way is magnified by the lens 26 and projected onto the screen 27. However, the reflected reading light (R2) that has passed through the portion (dark state) where the alignment state of the liquid crystal layer 12 is maintained does not pass through the splitter 23 because its polarization direction does not change. In this way, the image formed on the liquid crystal layer 12 of the optical writing type liquid crystal display element l by the laser beam 25 is projected onto the screen 27.

The manufacturing method of the first embodiment will be explained below with reference to FIG.

A transparent electrode 3.9 consisting of a laminated layer of an ITO transparent conductive film and a Sn02 transparent conductive film is formed on a glass substrate 2.9 using a sputtering method.
Formed on 8.

The photoconductor layer 4 made of an amorphous hydrogenated silicon (a-3i:H) layer is made of silane gas (SiH4), hydrogen gas (H2
) is used as a raw material and is formed on the transparent electrode 3 using a plasma CVD method. The layer thickness is approximately 3 μm.

The light absorption layer 5 made of amorphous silicon tin hydride (a-3iSn.H) is formed using a mixed gas of silane gas (S+H4) and tetramethyltin (Sn (CH3) 4).
It is formed on the photoconductor layer 4 by plasma CVD method. In this case, the flow rate ratio of (the sum of silane gas and tetramethyltin to tetramethyltin) Sn (CH) / (S+H+Sn (CH3)
4) can be varied in the range of 2.834 4 mol% to 4.9 mol%, but it is desirable to select this flow rate ratio to be about 4 mol%.

The thickness of the light absorption layer 5 is approximately 0.2 μm.

The dielectric layer 6 is formed on the light-Xx absorption layer 5 using two types of amorphous hydrogenated silicon carbide (a-5i C:H) having different compositions. That is, as shown in FIG. 3, a layer 11 made of amorphous hydrogenated silicon carbide, and a layer f12 made of amorphous hydrogenated silicon carbide having a composition different from that of layer 11.
A dielectric layer 6 having a multilayer structure in which 17 layers are alternately stacked is formed on the light absorption layer 5. Layer 1 and layer 1 are each created by plasma CVD using silane gas (SiH4), 2 hydrogen (H), and methane gas (CH4) as raw materials.

As can be seen from Fig. 4, amorphous hydrogenated silicon carbide a −
3i,, The molar composition X of carbon in Cx:H is the flow rate ratio
CH/ (S+H4+ CH4) (capacity ratio or molar ratio)
increases monotonically as . Therefore, the molar composition or flow rate ratio of carbon in amorphous hydrogenated silicon carbide CH/ (
Sin 4 + CH4).

Figure 5 shows the molar composition Y of silicon in amorphous hydrogenated silicon carbide a-5i C:H and the silicon F
FIG. 3 is a diagram showing the relationship between the molar composition Y of +-y and the refractive index n of amorphous hydrogenated silicon carbide. As can be seen from this figure, as the molar composition Y of silicon in the amorphous hydrogenated silicon carbide increases, the refractive index n of the amorphous hydrogenated silicon carbide also increases. For example, when the molar composition Y of silicon is 0.33, the refractive index n of amorphous hydrogenated silicon carbide having this composition is 1.8, and when the molar composition Y of silicon is 0.78, it has this composition. The refractive index n of amorphous hydrogenated silicon carbide is 2.7. Third
As shown in the figure, the compositions of the layer 11 and layer l constituting the dielectric layer 6 are a-SiC:H and 2, respectively.
0.33 0.67”'0.78C
O, 22; H, and the thicknesses of layers 1 and 12 are each formed in a range of 50 m to 100 nm, and 17 layers of layers 1, 1 and 12 are laminated alternately. The thickness of the dielectric layer 6 is approximately 1.3 μm.

Alignment film made of polyimide film 7. The IO is formed on the dielectric layer 6 and the electrode 9 by a spin code, and these alignment films 7. Molecular orientation treatment by rubbing is performed on each of the lO.

A set consisting of a glass substrate 8, a transparent electrode 9, and an alignment film 10, and another set consisting of a glass substrate 2, a transparent electrode 3, a photoconductor layer 4, a light absorption layer 5, and a dielectric layer 6 are shown in FIG. As shown, they are bonded together with two spacers 11 interposed therebetween. Alignment film 7.
The thickness of the space between 10 is approximately 6 μm. Chiral material (S 811: manufactured by MERCK) as the liquid crystal layer 12
A mixed nematic liquid crystal obtained by adding about 10% by weight of phenylcyclohexane-based nematic liquid crystal is used as the alignment film 7. It is injected into the space between the IOs and sealed. Note that a phase transition mode is used as the operation mode of the optical writing type liquid crystal display element of this example.

In the optical writing type liquid crystal display element of this example, when an AC voltage is applied between the transparent electrodes 3 and 9 and the laser beam L1 is incident from the glass substrate 2 side, the liquid crystal jI... A bright state and a dark state occur. An image is formed by the difference between a bright state and a dark state in the liquid crystal layer 12.

In this example, the composition of the amorphous hydrogenated silicon carbide constituting the dielectric layer 6 is controlled by changing the flow rate ratio CH4/(SiH4+CH4) of the raw material gas during production of the amorphous hydrogenated silicon carbide. Ru. As a result, when layer l and layer 12 are alternately laminated, the same raw material gas is used in the formation stage of layer j21 and the formation stage of layer I12, and the raw material gas flow rate ratio ClI is simply changed.
By changing 4/(SiH4,000Cll4),
The compositions of layer l and layer 12 can be controlled to desired compositions.

Therefore, according to this embodiment, as in the case where the dielectric layer 6 is formed by alternately laminating layers of zinc sulfide and layers of magnesium fluoride, it is not necessary to change the raw material at each layer formation stage. Therefore, the manufacturing process of the dielectric layer 6 can be simplified.

In this embodiment, methane is used as the carbon raw material gas for the amorphous hydrogenated silicon carbide (a-5iC:H) constituting the dielectric layer 6, but other than methane can be used as the carbon raw material gas.
Hydrocarbons such as ethane, propane, butane, acetylene, etc. can also be used. A layer of amorphous hydrogenated silicon carbide! ,
, It2 may be formed by a method other than the plasma CVD method, such as a sputtering method, a thermal CVD method, a vacuum evaporation method, or the like.

a-5i The silicon composition Y of C:H is as follows:
ty 0.1≦Y≦0.9(
a-5i C:H carbon composition X is 0.1≦
-X
Although it is possible to determine the value of Y or
At 0.1≦Y≦0.5.0.7≦Y≦0.9
(For X, 0.1; X≦0.3, 0.5≦X
≦0.9). In addition, the number of laminated layers is not limited to 17 layers, but may be 10 or more layers,
The number of layers is preferably 15 or more.

When using a nematic liquid crystal, liquid crystal display modes include, in addition to the phase transition mode shown in this example, twisted nematic mode, electric field-induced birefringence mode, dynamic scattering mode, guest-host mode, and hybrid field effect mode. mode is available.

Furthermore, when using smectic liquid crystal, guest-host mode and light scattering mode can be used, and ferroelectric liquid crystal can also be used.

Next, a second embodiment of the present invention will be described with reference to FIG.

In the second embodiment shown in the figure, three liquid crystal light valves 41a s 41b % 41c are used for R (red), G (green), and B (blue), respectively, using three liquid crystal display elements similar to those in the first embodiment.
It is used as a projection type color display device. In this case, as shown in the figure, the light from the light source 45 is separated into three colors, RSG and B, by the prism 43 and the glaucroic mirrors 42a s 42b s 42c, and the liquid crystal light pulp 41
After passing through the a s 41b s 41e, they are combined again by the prism 43 and projected onto the screen 46.

The manufacturing method of the liquid crystal light pulp 41a z 41b s 41c is as shown in the first example, but R, G, B
Each liquid crystal light valve R cell, G corresponds to the illumination light of
The wavelength distribution of the reflectance of the dielectric layer of the cell and the B cell has different characteristics for each cell, and is characterized in that the spectrum is approximately equal to the spectrum of the illumination light.

As a result, the wavelength range in which the dielectric layer has a high reflectance required for it can be narrowed, so that the thickness of the dielectric layer can be reduced. For example, high reflectance can be applied to the entire visible light range (400 nm).
m ~ 700 nm), a layer thickness of about 1.3 μm is required as shown in the first example, but 50Q
If limited to the wavelength range from ++al to 6'60 nm, approximately 0
．． A layer thickness of 5 μm to 0.8 μm is sufficient. Therefore, it is possible to increase the reflectance without reducing the voltage applied to the liquid crystal layer.

In the projection type color display device configured in this manner, light from the light source 45 enters the prism 43. The light is transmitted through a prism 43 and a guichroic mirror 42a,
Liquid crystal light pulps 41a and 41b are separated into R, G, and B by 42b and 42c, and images are formed thereon.

41c respectively. This incident light is reflected by the dielectric layer in each liquid crystal light pulp 41a N 41b% 41c, combined by a prism 43, and further magnified by a lens 44. The image thus formed on the liquid crystal light pulp 41a N 41b N 41c is projected onto the screen 46 as one color image.

Next, a third embodiment of the present invention will be described in which a scattering type liquid crystal composite film is used as the liquid crystal display mode.

The manufacturing method of the third embodiment is similar to that of the first embodiment up to the formation of the dielectric layer.
is the same as In the third example, after forming the dielectric layer in this way, 30 w% of bifunctional acrylate (manufactured by Nippon Kayaku Co., Ltd. 'HX-620'') which is a UV polymerizable compound and nematic liquid crystal (manufactured by Merck Company '2LI- 3201-0
00') A homogeneous solution was prepared by mixing 70 w% of the polymerization initiator (Darocurel 173' manufactured by Merck) and filtered.

This solution was applied onto the formed dielectric layer using a spinner to a thickness of 10 μm and exposed to ultraviolet light. After this, a transparent substrate with a counter electrode ITO is assembled.

A voltage is applied between the transparent electrodes of a liquid crystal display element having such a structure by an AC power source during operation. When light is incident in this state, the impedance of the photoconductive layer decreases in the region hit by the light (bright state), and the voltage applied by the AC power source is applied to the liquid crystal layer. On the other hand, in a region not exposed to light (dark state), the impedance of the photoconductor layer does not change and no voltage is applied to the liquid crystal. An image is formed based on the difference between the bright state and the dark state.

When the liquid crystal display element of the third embodiment in which an image is formed in this manner is used as a liquid crystal light pulp in a projection type display device as shown in FIG. 2, when light from a light source is incident on the liquid crystal light pulp, In areas where the state of the liquid crystal layer has not changed, this incident light is scattered and does not reach the projection lens, resulting in a dark state on the screen. On the other hand, in areas where the alignment state of the liquid crystal layer has changed in such liquid crystal light pulp, the liquid crystal layer becomes transparent, so the incident light is reflected by the dielectric layer and magnified by the projection lens, thereby forming liquid crystal light pulp. The captured image is projected onto the screen.

[Effects of the Invention] According to the present invention, since at least one of the light absorption layer and the dielectric layer includes an amorphous silicon film, it is possible to improve the resolution of the optical writing type liquid crystal display element.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing the structure of an embodiment of the present invention, FIG. 2 is an explanatory view showing the structure of a projection type display device using the liquid crystal display element of FIG. 1, and FIG. FIG. 4 is a cross-sectional view showing the structure of the dielectric layer of the liquid crystal display element shown in FIG. :H) and Figure 5 show the relationship between the composition of amorphous hydrogenated silicon carbide (a-3i C:H) and the composition of amorphous hydrogenated silicon carbide
FIG. 6 is an explanatory diagram showing the structure of a projection type color liquid crystal display device using a liquid crystal display element according to another embodiment of the present invention. 1... Optical writing type liquid crystal display element, 28...
...Glass substrate, 3.9...Transparent electrode, 4
...Photoconductor layer, 5...Light absorption layer, 6...Dielectric layer, 7.10...
・Alignment film, 11...Spacer, 12...
・LCD, 13...Power supply, 20...
...Light source, 2124...Lens, 23...
Polarized beam splitter, 25...Writing light,
26...Illumination lens, 27...Screen, Ll...Writing light, R1 R2...Reflected reading light, 41a 41b 41c... Liquid crystal light valve, 42a 42b 42c... Dichroic mirror 43... Prism, 44...
...Lens, 45...Light source, 4
6...Screen.・・・・・・Incoming reading light, Fig. 3 Fig. 5

Claims (1)

[Claims] a first transparent substrate, a first transparent electrode layer formed on the first transparent substrate, a photoconductor layer formed on the first transparent electrode layer, and a photoconductor layer formed on the photoconductor layer. a light absorption layer formed on the light absorption layer, a dielectric layer formed on the light absorption layer, a second transparent substrate, a second transparent electrode layer formed on the second transparent substrate, It has a second transparent electrode layer and a liquid crystal layer inserted between the dielectric layers, and at least one of the light absorption layer and the dielectric layer includes an amorphous silicon-based film. An optical writing type liquid crystal display element.