JP2698756B2 - Manufacturing method of liquid crystal display element - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device used as a large optical shutter, a large display, a projection display or the like.

[0002]

2. Description of the Related Art Ferroelectric liquid crystals have characteristics such as high-speed response, a wide viewing angle, bistability, and memory characteristics, and are expected as next-generation display devices. Above all, the surface stabilized display mode (hereinafter, referred to as SSFLC) invented by Clark et al. Is important in producing a large-area display element (see the related article Applied Physics Letter, Volume 3).
6, 899, 1980). The method of controlling the alignment of the smectic phase of the ferroelectric liquid crystal includes an external field application method, a temperature gradient method, a rubbing method, an oblique evaporation method, and the like, and the rubbing method and the oblique evaporation method are provided with a uniaxial alignment control ability. . In general, the ferroelectric liquid crystal changes its layer structure in the course of temperature change from the smectic A phase to the smectic C phase, so that the orientation direction is tilted from the normal direction of the layer against the uniaxially controlled direction. Therefore, it is necessary to rotate the display element in the system to adjust the polarization direction.

Further, zigzag defects, streak defects, and the like peculiar to the ferroelectric liquid crystal grow perpendicularly to the uniaxially controlled direction, that is, parallel to the smectic phase layer. These defects became remarkable when the liquid crystal was filled in the liquid crystal cell when the liquid crystal was filled in parallel to the direction in which the uniaxial alignment treatment was performed.

On the other hand, a display device using an antiferroelectric liquid crystal instead of a ferroelectric liquid crystal has been developed, and a Japanese journal of applied physics 27 (198) has been developed.
8 years) p. 729 (Jpn. J. Appl. Phys., 27, L729 (1988))
It has been announced. This device is a display device utilizing switching between the above three states of a stable antiferroelectric phase and two ferroelectric phases which are developed by electric field induction. The phase transition between the antiferroelectric phase and the ferroelectric phase has a sharp threshold with respect to the magnitude of the applied voltage. The optical characteristics of the element with respect to the applied voltage have a hysteresis characteristic, and have a memory function for holding each of the three states. This antiferroelectric liquid crystal is expected as a liquid crystal display material that realizes high-speed response and multi-value display in the future.

[0005]

In order to realize a high-contrast display device, it is necessary to control the alignment of the liquid crystal in the order of a few μm in film thickness and to optimally design the optical element. In the case of projecting onto a screen or the like using a conventional display element which has been subjected to an alignment treatment, there is a problem that the polarization direction must be matched by installing the display element at an angle to the screen. Further, the conventional method of forming a liquid crystal cell has a problem that a streak defect tends to grow when the direction of the alignment treatment and the direction of filling the liquid crystal coincide.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method of manufacturing a liquid crystal display device capable of achieving stable alignment with uniform quality as a whole and realizing a high contrast ratio in order to solve the conventional problems. .

[0007]

To achieve the above object, according to an aspect of manufacturing method of liquid crystal display device according to the present invention, a pair of base
An electrode is formed on each surface of the plate, and the surface of the electrode is
Orientation film is formed, the distribution between the alignment film ferroelectric liquid crystal or antiferroelectric
A method for manufacturing a liquid crystal display element filled with a ferroelectric liquid crystal.
The orientation axis of the ferroelectric liquid crystal or antiferroelectric liquid crystal,
The longitudinal direction of one of the pair of opposed substrates
Or tilt in the range of 20 degrees or more and 30 degrees or less to the horizontal
Between 45 degrees and 90 degrees with respect to the liquid crystal filling direction.
It is characterized in that it is inclined in a range.

[0008]

According to the method of manufacturing a liquid crystal display device of the present invention, the orientation axes of the ferroelectric liquid crystal or the antiferroelectric liquid crystal are set to be opposite to each other.
Vertical or horizontal of one of the pair of substrates
In the range of 20 ° to 30 ° with respect to the direction
By doing, the liquid crystal in the smectic C phase,
One parallel to one side (vertical or horizontal) of the substrate
Liquid crystal display elements,
It can be manufactured efficiently and reasonably. Also ferroelectric
The orientation axis of the liquid crystal or antiferroelectric liquid crystal is
And tilt it between 45 degrees and 90 degrees.
And the smecticity of ferroelectric and antiferroelectric liquid crystals
Zigzag defects, streak defects, etc.
Or liquid that suppresses growth, including contrast
The display quality of the crystal display element can be improved. This is because the zigzag defect, which is a defect peculiar to the smectic phase of ferroelectric liquid crystal and antiferroelectric liquid crystal, is formed by liquid crystal.
Based on a newly discovered experimental fact that a large number of streak defects occur when the liquid crystal is filled in the liquid crystal cell parallel to the alignment processing direction. Things.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1A is a plan view of one embodiment of the display element of the present invention, and FIG. 1B is a cross-sectional view taken along the line AB. In the display element 10, alignment films 6 and 7 are applied and formed on the glass substrate 1 on which the pixel electrode 5 is formed after forming the transparent electrode 3 on the surface and the glass substrate 2 on which the transparent electrode 4 is formed on the surface. The dielectric liquid crystal 8 is interposed.

As the alignment film, for example, a film represented by the general formula (Formula 1) is used.

[0011]

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As the low-molecular liquid crystal material, for example, a material represented by the general formula (Formula 2) is preferable.

[0013]

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Example 1 The display element 10 shown in FIG. 1 was manufactured by the following method. 6
A transparent electrode of indium tin oxide (ITO) was formed to a thickness of 1000 angstroms on a 5 mm × 55 mm optically polished glass substrate 1 or 2 by sputtering. On one glass substrate 1, Al is further formed as a pixel electrode 5 with a thickness of 1000 angstroms by using a vacuum evaporation method, and a 200 μm pitch of 28 μm and a pixel of 26 μm are formed.
0x2000 matrix pixels were patterned.
On each substrate, an organic alignment film 6 represented by the following formula (Formula 1)
7 was applied with a spinner to a thickness of 500 angstroms. The weight average molecular weight (M) of the organic alignment film of the following formula (Formula 3)
w) was 4.3 × 10 ⁵ .

[0015]

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Other methods for forming the organic alignment films 6 and 7 of the formula (Formula 3) include a vacuum deposition polymerization method, an electrolytic polymerization method, and a catalyst polymerization method. After spinner coating, the surfaces of the organic alignment films 6 and 7 of the coating film were rubbed using rayon cloth. The rubbing direction at this time was set so as to be inclined with respect to one side of the substrate and parallel when the glass substrates 1 and 2 were combined. Glass beads having a diameter of 1 μm are dispersed on a substrate, and a pair of glass substrates 1 and 2 are adhered to each other with a sealant to form a liquid crystal cell. The liquid crystal cell is placed in a vacuum container, and the heating temperature of the liquid crystal cell is set to be equal to or higher than the melting point of the ferroelectric liquid crystal 8 under vacuum, and then the ferroelectric liquid crystal 8 is filled into the liquid crystal cell by a capillary phenomenon. The ferroelectric liquid crystal 8 used for the prototype is
It was shown to.

[0017]

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The liquid crystal filling direction is defined as a direction perpendicular to a straight line connecting the seal opening ends, as shown in FIG. The liquid crystal placed on the glass substrate fills the portion surrounded by the sealing resin in the order of broken lines a, b, and c as the substrate is heated.

A display system using the display element 10 as shown in FIG. 3 was made and image evaluation was performed. The system comprises a light source 30, a polarizer 31, a beam splitter 32, an analyzer 3
3. It is composed of a drive system 34.

The number of defects when the angle between the liquid crystal filling direction and the rubbing direction shown in FIG. 2 was θ was observed using the display system of FIG. 3, and is shown in the graph of FIG. Defects frequently occur near 0 degrees, that is, when the filling direction of the liquid crystal and the orientation direction of the liquid crystal by rubbing are nearly parallel, but from 45 to 90 degrees, little or no defects are generated, and a uniform and good image is obtained. .

(Embodiment 2) FIG. 5 is a sectional view of an embodiment of the optical writing type spatial light modulator 11. The spatial light modulator 11 was manufactured by the following method. 15 cm × 15 cm optically polished glass substrates 1 and 2
An ITO film of 1000 Å was formed thereon by sputtering. On one glass substrate 1, p / i /
An amorphous silicon layer 9 having an n-diode structure was stacked by 1.5 μm using a chemical vapor deposition method (CVD method). Further, the reflective pixel electrodes 5 for reading are arranged on the photoconductive layer 9 in a matrix. Then, the same organic alignment films 6 and 7 as in Example 1 were applied and formed on the respective substrates, and the same ferroelectric liquid crystal 8 as in Example 1 was injected. As the rubbing direction at this time, a tilt angle of 25 degrees at room temperature of the used liquid crystal was applied.

The pixel electrode 5 was formed by patterning 3000 × 3000 pixels of a 38 μm square aluminum reflective electrode at a pitch of 40 μm by using a photolithographic technique. A display screen having an aperture ratio of 90.25% is obtained.

FIG. 6 shows a projection television system using the optical writing type spatial light modulator 11. Reading light source 60, lens 61, polarization beam splitter 6
2. It is composed of an optical writing type spatial light modulator 11, a self-focus lens array 63, a CRT 64 for writing an image, a projection lens 65, and a screen 66. The moving image displayed on the CRT is magnified on the screen, a very bright and clear image of 500 lx is obtained, and the contrast ratio is 2
00: 1 or more. Further, one side of the light-writing type spatial light modulator 11 projected on the screen was parallel to the vertical line, and the image was very easy to see.

The material used for the photoconductive layer 9 operates as a dielectric in the dark, and loses the characteristics of the dielectric due to photoconductivity when irradiated with light. For example, CdS, CdTe,
CdSe, ZnS, ZnSe, GaAs, GaN, Ga
Compound semiconductors such as P, GaAlAs, InP, Se, S
amorphous semiconductor such as eTe, AsSe, Si, Ge, S
i _1-x C _x , Si _1-x Ge _x , Ge _1-x C _x (0 <x <1) polycrystalline or amorphous semiconductor, and (1) phthalocyanine pigment (abbreviated as Pc) Metal-free Pc, XPc (X
= Cu, Ni, Co, TiO, Mg, Si (OH) ₂ etc.), AlClPcCl, TiOClPcCl, InC
lPcCl, InClPc, InBrPcBr, etc.
(2) azo dyes such as monoazo dyes and bisazo dyes,
(3) penylene pigments such as penylene anhydride and penimide, (4) indigoid dyes, (5) quinacridone pigments, (6) polycyclic quinones such as anthraquinones and pyrenequinones, (7) cyanine dyes, (8)
Organic semiconductors such as a xanthene dye, (9) a charge transfer complex such as PVK / TNF, (10) a eutectic complex formed from a beryllium salt dye and a polycarbonate resin, and (11) an azurenium salt compound.

Further, amorphous Si (hereinafter a-Si),
Amorphous Ge (hereinafter a-Ge), amorphous Si _1-x C
_x (hereinafter a-Si _1-x C _x ), amorphous Si _1-x Ge
_x (hereinafter a-Si _1-x Ge _x ), amorphous Ge _1-x C
_{When x} (hereinafter a-Ge _1-x C _x ) is used for the photoconductive layer 9, hydrogen or a halogen element may be included, and oxygen or nitrogen is added to reduce the dielectric constant or increase the resistivity. May be included. For controlling the resistivity, an element such as B, Al, or Ga which is a p-type impurity or an element such as P, As, or Sb which is an n-type impurity may be added. The amorphous material to which the impurities are added as described above is stacked to form p / n, p /
The dielectric constant, dark resistance or operating voltage polarity may be controlled by forming a junction such as i, i / n, p / i / n and forming a depletion layer in the photoconductive layer 9.

In addition to such an amorphous material, a depletion layer may be formed in the photoconductive layer 9 by forming a heterojunction by laminating two or more of the above materials. (Example 3) FIG. 2 shows a case where the liquid crystal filling direction of the optical writing type spatial light modulator 11 is parallel to one side of the substrate as shown in FIG. 2 and the angle of the rubbing direction to this direction is θ. Table 1 shows the mounting angle x of the panel to the projection television system shown in FIG. The mounting angle x of the panel is the optical writing type spatial light modulator 1 projected on the screen 66.
The angle between one side and the vertical line was measured. When rubbing is performed by tilting the liquid crystal at an angle of 25 degrees with respect to one side of the substrate, the liquid crystal is mounted in parallel with the system. Furthermore, no defect was observed except when θ was 0 degrees.

[0027]

[Table 1]

When the display is performed by using the switching between the bistable states in the SSFLC mode, the switching angle at which the maximum contrast is obtained is 45 degrees.
Since the ferroelectric liquid crystal is molecularly designed to take an angle in the vicinity of this, θ is 20 to 30 degrees or 60 degrees to 60 degrees.
70 degrees is preferred.

Embodiment 4 FIG. 5 shows an embodiment in which a liquid crystal layer having at least a rectifying photoconductor and an antiferroelectric phase as a phase state is sandwiched between a pair of transparent electrodes to form a spatial light modulator.

FIG. 7 shows an example of a structure having a plurality of fine metal thin films 707 and 708 electrically independent from each other between a photoconductor and a liquid crystal layer. A typical example of a photoconductor having a rectifying property is amorphous silicon (hereinafter a-Si: H). In this embodiment, the p-type layer 704 (500 angstrom thickness), i
Three layers of a mold layer 705 (film thickness of 1.7 μm) and an n-type layer 706 (film thickness of 3000 Å) are successively laminated;
A photoconductor having a diode structure was formed. The photoconductor is divided into pixels, and each metal thin film 708 functions as a reflective film that reflects read light simultaneously with the pixel electrodes. An output light-shielding film 709 made of a metal thin film is provided at the bottom between the pixels,
Further, it has a groove structure filled with a polymer film 710 in which carbon is dispersed. This groove structure prevents the charge from diffusing between the pixels, and also prevents the reading light applied between the pixels from leaking to the photoconductor and causing a malfunction. Below the photoconductor is an input light-shielding film 703 for separating optical input information into each pixel. Polymer films 711 and 7 that have been subjected to an alignment treatment in the same direction by a rubbing method in order to align the antiferroelectric liquid crystal.
13 sandwiches the liquid crystal layer. The rubbing direction at this time was set so as to have an inclination of 25 degrees with respect to one side of the substrate, and also to have an inclination of 25 degrees with respect to the filling direction of the liquid crystal.
Considering that the optimal thickness of the liquid crystal layer is the reflection mode,
The optical path length is determined to be half of the optical path length obtained from the condition for obtaining the maximum modulation rate from the refractive index of the liquid crystal. By dispersing spacers 712 having the same particle size as this optimum film thickness, the liquid crystal film thickness is ensured. The direction in which the liquid crystal was filled was set so as to have an inclination of 25 degrees with the rubbing direction. Glass substrate 70
A pair of transparent electrodes 702 provided on each of
A voltage 716 is applied to 714 to drive the element 700.

FIG. 8 shows the time response characteristics of the reflected light when the intensity of the optical writing light applied to the photoconductor of the spatial light modulator 700 is changed. Driving was performed with a forward voltage of +10 V for erasing, a second application time of 0.1 msec, a reverse voltage of -20 V for optical writing, and a first application time of 1.1 m.
sec. Therefore, the driving frequency is 833 Hz.
When the polarizer is set so that the deflection direction of the polarizer coincides with the rubbing direction, black display is performed in an antiferroelectric phase state. When the optical writing light intensity is changed from 0 to 0.8 mW / cm ² , the reflected light intensity increases as the intensity increases. When the output light is defined by the time average of the reflected light intensity, the change of the output light with respect to the optical writing light intensity is as shown in FIG. This is a halftone display in which the reflectance is controlled from 0% to 80% when the light writing light intensity changes from 0 to 0.8 mW / cm ² . The maximum reflectance is 80% because the applied voltage at the time of optical writing is 20 V at maximum and the time required for phase transition at this electric field intensity is 0.3 msec. 1.1
During the msec period, this transition time is a loss for white display. The contrast ratio secured a maximum of 200 or more.

[0032]

As described in detail above, according to the method of manufacturing a liquid crystal display device of the present invention, a ferroelectric liquid crystal or an antiferroelectric
The alignment axis of the liquid crystal is adjusted to one of the pair of substrates
20 degrees or more and 30 degrees or less with respect to the vertical or horizontal direction of the board
Smectic by tilting in the range of
The liquid crystal in the C phase is applied to one side of the substrate (vertically or horizontally).
Direction) can be arranged evenly in a direction parallel to
As a result, liquid crystal display elements can be efficiently and rationally manufactured.
Wear. In addition, the orientation axis of the ferroelectric liquid crystal or antiferroelectric liquid crystal
In the range of 45 ° to 90 ° with respect to the liquid crystal filling direction
By tilting the ferroelectric liquid crystal and anti-
Zigzag defects unique to the smectic phase of dielectric liquid crystals,
By suppressing the occurrence or growth of streak defects,
Improve the display quality of liquid crystal display elements, including
Can be

Therefore, a direct-view television and a projection large-screen television using the liquid crystal display device of the present invention can provide a stable image with high display quality.

[Brief description of the drawings]

FIG. 1A is a plan view of one embodiment of a display element of the present invention, and FIG. 1B is a cross-sectional view taken along a line AB.

FIG. 2 defines a liquid crystal filling direction of the present invention.

FIG. 3 is an example of a display system using the display element 10 according to one embodiment of the present invention.

FIG. 4 is a graph showing the angle θ between the liquid crystal filling direction and the rubbing direction and the number of generated defects according to one embodiment of the present invention.

FIG. 5 is a cross-sectional view of one embodiment of the optical writing type spatial light modulator 11 of one embodiment of the present invention.

FIG. 6 is an example of a projection television system using the optical writing type spatial light modulator 11 of one embodiment of the present invention.

FIG. 7 shows an embodiment of the present invention in which a spatial light modulating element 700 is formed by sandwiching a liquid crystal layer having at least a rectifying photoconductor and an antiferroelectric phase as a phase state between a pair of transparent electrodes.

FIG. 8 is a time response characteristic of reflected light when the intensity of the optical writing light applied to the photoconductor of the spatial light modulator 700 according to one embodiment of the present invention is changed.

FIG. 9 shows a change in output light with respect to the light writing light intensity when the output light is defined by the time average of the reflected light intensity according to one embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Glass substrate 2 Glass substrate 3 Transparent electrode 4 Transparent electrode 5 Pixel electrode 6 Organic alignment film 7 Organic alignment film 8 Ferroelectric liquid crystal 9 Photoconductive layer 10 Display element 11 Optical writing type spatial light modulation element a, b, c Liquid crystal filling direction

Claims (1)

(57) [Claims] An electrode is formed on each surface of a pair of substrates.
Forming an alignment film on the surface of the electrode,
Liquid crystal table filled with ferroelectric liquid crystal or antiferroelectric liquid crystal
A method of manufacturing a display device, comprising:
The orientation axis of the dielectric liquid crystal is adjusted by any of the pair of substrates facing each other.
At least 20 degrees to the vertical or horizontal direction of either substrate
Tilt within a range of 30 degrees or less and 4
In particular, it should be tilted in the range of 5 to 90 degrees.
A method for manufacturing a liquid crystal display element.