JPH0784263A - Liquid crystal display element and its production - Google Patents

Abstract

PURPOSE:To realize orientation uniform and stable in quality over the entire part by having ferroelectric liquid crystal polymer layers on transparent substrate surfaces and encapsulating low molecule ferroelectric liquid crystals to the inner side thereof. CONSTITUTION:This display element is produced by applying and forming the high polymer ferroelectric liquid crystals 5, 6 on a pair of the glass substrates 1, 2 formed with transparent electrodes 3, 4 on their surfaces and holding the low molecule ferroelectric liquid crystals 7 therebetween. The ferroelectric liquid crystals are uniaxially oriented and controlled in a stretching direction by orienting if ferroelectric liquid crystal polymers formed as films are used. The film surfaces of the high polymer ferroelectric liquid crystals lined up with the high polymer chains in one direction are formed and the low polymer ferroelectric liquid crystal is inserted between a pair of the films, by which the low polymer ferroelectric liquid crystals are uniformly lined up in their axial direction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a display device used for a large optical shutter, a large display, a projection type display, a projection screen and the like.

[0002]

2. Description of the Related Art A low-molecular ferroelectric liquid crystal has characteristics such as high-speed response, wide viewing angle, bistability, and memory characteristics, and is expected as a next-generation display device. Among them, the surface-stabilized display mode proposed by Clark et al. (Hereinafter referred to as SSFLC) is important for making a large-area display device (related article Applied Physics Letter, Volume 36, page 899, 1980). However, it is difficult to increase the size of a low-molecular ferroelectric liquid crystal because it is difficult to control the alignment and a display element using the liquid crystal has a drawback of being weak against mechanical shock. On the other hand, polymer ferroelectric liquid crystals have been synthesized by adding a known ferroelectric liquid crystal as a pendant to a polymer side chain. This is intended for large-sized display devices by facilitating thinning and device formation while maintaining the wide viewing angle, bistability, and memory characteristics of low-molecular ferroelectric liquid crystals. In the conventional alignment film, the alignment in the vicinity of the alignment film has been controlled by a physical method such as rubbing treatment or oblique deposition of silicon oxide or the like by the surface shape.

[0003]

However, in order to increase the size of a display device using a low-molecular ferroelectric liquid crystal, it is necessary to control the film thickness on the order of several μm and to achieve stable orientation. Conventional low-molecular-weight ferroelectric liquid crystals have extremely weak liquid crystal alignment against mechanical shock, so new development of alignment materials and alignment methods is required. Further, it has been difficult to maintain uniform quality by conventional rubbing treatment of the surface of the alignment film or oblique vapor deposition of silicon oxide or the like. Furthermore, although it is easy to make thin and large-sized display devices using polymer ferroelectric liquid crystal, the response speed to an electric field decreases due to the high viscosity of the polymer, and the ferroelectric property of high-speed response There was a problem that the characteristics of liquid crystal could not be obtained.

In order to solve the above-mentioned conventional problems, the present invention aims to provide a liquid crystal display device having a uniform quality and stable alignment as a whole, and a relatively easy manufacturing process, and a manufacturing method thereof. And

[0005]

In order to achieve the above object, a liquid crystal display device of the present invention is a liquid crystal display device which operates by molecular inversion by application of a voltage, and a ferroelectric liquid crystal polymer is formed on a transparent substrate surface. It is characterized in that it has a layer and a low-molecular ferroelectric liquid crystal is enclosed inside the layer.

In the above structure, it is preferable that the low molecular weight ferroelectric liquid crystal layer is sandwiched between the first ferroelectric liquid crystal polymer layer and the second ferroelectric liquid crystal polymer layer. Further, in the above structure, it is preferable that a layer composed of a low-molecular ferroelectric liquid crystal and a ferroelectric liquid crystal polymer is included between the pair of transparent substrates.

In the above structure, it is preferable that a photoconductive layer and a layer composed of a low-molecular ferroelectric liquid crystal and a ferroelectric liquid crystal polymer are included between the pair of transparent substrates. Further, in the above-mentioned constitution, it is preferable that the side chain organic group constituting the ferroelectric liquid crystal polymer and the chemical structure of the low molecular weight ferroelectric liquid crystal are substantially the same.

Next, the method for producing a display element of the present invention is characterized in that the ferroelectric liquid crystal polymer is stretched, the ferroelectric liquid crystal polymer layer is formed on the surface of the transparent substrate, and then the display element is assembled. To do.

[0009]

According to the above-described structure of the present invention, since the ferroelectric liquid crystal polymer layer is provided on the surface of the transparent substrate and the low-molecular-weight ferroelectric liquid crystal is enclosed inside the layer, the quality is uniform throughout. A stable orientation can be realized. That is, the surface-stabilized display mode (SSFLC) of the ferroelectric liquid crystal that performs display operation by molecular inversion by applying a voltage is determined by the alignment characteristics of the low molecular ferroelectric liquid crystal near the alignment film. Also,
By using a polymer ferroelectric liquid crystal having the same or similar ferroelectricity as the low molecular ferroelectric liquid crystal as an alignment film,
Not only shape but also electrostatically strong bond can be created at the interface. By forcibly controlling the orientation at the interface, a stable orientation can be realized as a whole. Since the ferroelectric liquid crystal polymer layer is formed on the surface of the transparent substrate, this polymer layer can be easily thinned into a film.

Further, according to the preferable constitution of the present invention, the low-molecular-weight ferroelectric liquid crystal layer is sandwiched between the first ferroelectric liquid crystal polymer layer and the second ferroelectric liquid crystal polymer layer. The size can be increased by sandwiching a low-molecular ferroelectric liquid crystal that can respond at high speed by using a controllable polymer ferroelectric liquid crystal.

Further, according to the preferable constitution of the present invention in which the layer composed of the low molecular weight ferroelectric liquid crystal and the ferroelectric liquid crystal polymer is included between the pair of transparent substrates, the structure is further simplified.

A photoconductive layer is provided between the pair of transparent substrates,
According to the preferable constitution of the present invention including the layer composed of the low-molecular ferroelectric liquid crystal and the ferroelectric liquid crystal polymer, for example, an optical writing type spatial light modulator can be realized.

Further, according to the preferred constitution of the present invention, the organic group of the side chain constituting the ferroelectric liquid crystal polymer and the chemical structure of the low molecular weight ferroelectric liquid crystal are substantially the same.
The affinity of the interface between the ferroelectric liquid crystal polymer layer and the low-molecular ferroelectric liquid crystal layer is improved, and a display element with more uniform quality can be obtained.

According to the structure of the method for manufacturing a display device of the present invention, the ferroelectric liquid crystal polymer is stretched, the ferroelectric liquid crystal polymer layer is formed on the surface of the transparent substrate, and then the display device is assembled. As a result, the display element can be efficiently and reasonably manufactured. That is, the film-formed ferroelectric liquid crystal polymer is uniaxially controlled in the stretching direction by stretching. Therefore, by creating a film surface of a polymer ferroelectric liquid crystal in which polymer chains are arranged in one direction and sandwiching a low molecular ferroelectric liquid crystal between a pair of films,
The low-molecular-weight ferroelectric liquid crystal can be uniformly arranged in the axial direction.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1A is a plan view of an embodiment of the display element of the present invention, and FIG. 1B is a sectional view taken along the line AA '.
The display element 10 comprises a pair of glass substrates 1 and 2 having transparent electrodes 3 and 4 formed on the surfaces thereof, and high-molecular ferroelectric liquid crystals 5 and 6 formed by coating and sandwiching a low-molecular ferroelectric liquid crystal 7. .

As the liquid crystal material polymer, for example, one represented by the general formula (Formula 1) is used.

[0017]

[Chemical 1]

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

[0019]

[Chemical 2]

Example 1 The display element 10 shown in FIG. 1 was manufactured by the following method. A transparent electrode, indium tin oxide (ITO), having a thickness of 1000 angstroms is formed on a glass substrate 1 or 2 which is 5 cm in length × 5 cm in width and optically polished by a sputtering method. 3 and 4 were patterned. By using this pair of substrates 1 and 2, 1000 × 1000 matrix pixels were formed. Ferroelectric liquid crystal polymers 5 and 6 represented by the following formula (Formula 3) were coated on each substrate by a spinner to a thickness of 1000 angstrom. The following formula (Formula 3)
The weight average molecular weight (Mw) of the above ferroelectric liquid crystal polymer was 4.3 × 10 ⁵ .

[0021]

[Chemical 3]

Besides the above, the ferroelectric liquid crystal polymers 5 and 6 of the formula (Formula 3) may be formed by vacuum vapor deposition polymerization, electrolytic polymerization, catalytic polymerization, or the like. Further, it is also possible to use a method in which the polymeric ferroelectric liquid crystals 5 and 6 are formed into a film and then adhered to the substrate surface. In this case, the polymer ferroelectric liquid crystals 5 and 6 whose uniaxial orientation is controlled can be produced by stretching the film, and the orientation of the low molecular ferroelectric liquid crystal 7 can be controlled without the rubbing step. . After applying the spinner, the surfaces of the ferroelectric liquid crystal polymers 5 and 6 of the coating film were rubbed with rayon cloth. 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 was placed in a vacuum container, and the heating temperature of the liquid crystal cell was set to be equal to or higher than the melting point of the low molecular weight ferroelectric liquid crystal 7 under vacuum, and then the low molecular weight ferroelectric liquid crystal 7 was injected into the liquid crystal cell by a capillary phenomenon. The low-molecular-weight ferroelectric liquid crystal 7 used for trial manufacture is shown in the following (Chemical formula 4).

[0023]

[Chemical 4]

A display system using the display element 10 as shown in FIG. 2 was made and image evaluation was performed. The system includes a backlight 20, a polarizer 21, an analyzer 22, and a drive system 23. When a moving image is displayed on 1000 × 1000 pixels, the orientation ratio is 100% and the contrast ratio is 200:
It was good at 1 or more.

The response speed when the layer thickness ratio of the ferroelectric liquid crystal polymers 5 and 6 and the low molecular weight ferroelectric liquid crystal 7 is changed is shown in (Table 1). The layer thickness of each of the ferroelectric liquid crystal polymers 5 and 6 is x (μm) and the layer thickness of the low molecular weight ferroelectric liquid crystal 7 is y (μm), and the total layer thickness is 2x + y = 2 (μm).
Is. It was confirmed that the larger the ratio of the layer thickness of the low-molecular ferroelectric liquid crystal 7 was, the faster the response speed was. Also,
From the result of the microscopic observation, it was confirmed that the presence of the ferroelectric liquid crystal polymers 5 and 6 makes the alignment state very good.

[0026]

[Table 1]

(Embodiment 2) FIG. 4 is a sectional view of an embodiment of the optical writing type spatial light modulator 12. The spatial light modulator 12 was manufactured by the following method. ITO was formed into a film of 1000 angstrom on the optically polished glass substrates 1 and 2 having a length of 15 cm and a width of 15 cm by a sputtering method. An amorphous silicon layer 8 having a p / i / n structure was laminated on one glass substrate 1 by a CVD method to a thickness of 1.5 μm. Further, the reflective pixel electrodes 9 for reading are arranged in a matrix on the photoconductive layer 8. Then, the ferroelectric liquid crystal polymers 5 and 6 similar to those in Example 1 were applied and formed on the respective substrates, and the low molecular ferroelectric liquid crystal 7 similar to that in Example 1 was formed.
Injected.

The pixel electrode 9 was formed by patterning 3000 × 3000 pixel aluminum reflective electrodes of 38 μm square at a pitch of 40 μm by using the photolithography technique. A display screen with an aperture ratio of 90.25% is obtained.

A projection television system using this optical writing type spatial light modulator 12 is shown in FIG. Light source 50 for reading, lens 51, polarization beam splitter 5
2. The spatial light modulator 12 of the optical writing type, the self-focus lens array 53, the CRT 54 for image writing, the projection lens 55, and the screen 56. The moving image displayed on the CRT is magnified on the screen to give a very bright and clear image of 500 lux and a contrast ratio of 20.
It was 0: 1 or more.

The material used for the photoconductive layer 8 acts as a dielectric in the dark and loses the characteristics of the dielectric due to photoconductivity during light irradiation. For example, CdS, CdTe,
CdSe, ZnS, ZnSe, GaAs, GaN, Ga
Compound semiconductors such as P, GaAlAs, InP, Se, S
Amorphous semiconductors such as eTe and AsSe, Si, Ge and 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), for example, metal-free Pc, XP
c (X = Cu, Ni, Co, TiO, Mg, Si (O
H) ₂ etc.), AlClPcCl, TiOClPcC
l, InClPcCl, InClPc, InBrPcB
r and the like, (2) azo dyes such as monoazo dyes and bisazo dyes, (3) penylene pigments such as penylene anhydride and penylene acid imide, (4) indigoid dyes,
(5) quinacridone pigment, (6) polycyclic quinones such as anthraquinones and pyrenequinones, (7) cyanine dyes, (8) xanthene dyes, (9) charge transfer complexes such as PVK / TNF, and (10) pyrylium salts. There are organic semiconductors such as a eutectic complex formed from a dye and a polycarbonate resin and (11) azurenium salt compound.

Amorphous Si, Ge, Si
_1-xC_x, Si_1-xGe_x, Ge_1-xC_x0 <x <1)
(Hereinafter, a-Si, a-Ge, a-Si_1-xC_x, A-
Si_1-xGe _x, A-Ge_1-xC_xAbbreviated as) light
When used for the conductive layer 8, it does not contain hydrogen or halogen elements.
You can reduce the dielectric constant or increase the resistivity.
Oxygen or nitrogen may be included for this purpose. For controlling the resistivity
Are p-type impurities such as boron, aluminum and gallium.
Which element or n-type impurities such as phosphorus, arsenic, and an
You may add elements, such as Zimon. Impurities like this
P-n, p / i, i /
n, p / i / n, etc. are formed, and a space is left in the photoconductive layer 8.
Dielectric constant and dark resistance or
The operating voltage polarity may be controlled.

Not only such an amorphous material, but also two or more kinds of the above materials may be laminated to form a heterojunction to form a depletion layer in the photoconductive layer 8. (Embodiment 3) FIG. 3 shows an optical writing type spatial light modulator 11.
It is sectional drawing of one Example. The spatial light modulator 11 has a photoconductive layer 8 formed on one glass substrate 1 having a transparent electrode 3 formed on the surface thereof. Ferroelectric liquid crystal polymers 5 and 6 are formed on each substrate by coating to form low molecular ferroelectric liquid crystal 7.
Is sandwiched between.

Optical writing type spatial light modulator 1 shown in FIG.
An organic photoconductive material was used for the photoconductive layer 8 of No. 1. As the organic photoconductive material, a material having a high transmittance for light in the visible region, absorbing light in the ultraviolet region and lowering electric resistance is used. For example, polyparaphenylene sulfide (PPS).
A device having a length of 1 m and a width of 1 m was manufactured and used for the screen 56 of the projection system shown in FIG.

Example 4 A display device 10 was manufactured by using a stretching device to stretch the ferroelectric liquid crystal polymer to a stretching ratio of 1 to 100%. The display system shown in FIG. 2 was used to evaluate the characteristics with respect to the stretching ratio. The results are shown in (Table 2). The contrast ratio dramatically increases as the stretching ratio increases.

[0035]

[Table 2]

[0036]

As described in detail above, according to the display element of the present invention, a uniform and stable alignment can be obtained by having a layer composed of a low molecular weight ferroelectric liquid crystal and a ferroelectric liquid crystal polymer as at least a constituent element. The obtained display device capable of high-speed response can be upsized. Further, by stretching the ferroelectric liquid crystal polymer and then installing it on the surface of the substrate, it is possible to easily obtain an ideal orientation and provide a display element which gives a high contrast ratio.

Therefore, the direct-view television, the projection large-screen television, and the projection screen using the display device of the present invention provide stable images with high display quality.

[Brief description of drawings]

FIG. 1A is a plan view of an embodiment of a display element of the present invention, and FIG. 1B is a sectional view taken along line AA ′ of FIG.

FIG. 2 is an example of a display system using the display element of one embodiment of the present invention.

FIG. 3 is a cross-sectional view of one embodiment of the optical writing type spatial light modulator of the present invention, which is a transmission type.

FIG. 4 is a cross-sectional view of an embodiment of the optical writing type spatial light modulator of the present invention, which is a reflection type.

FIG. 5 is an example of a projection television system using the optical writing type spatial light modulator of one embodiment of the present invention.

[Explanation of symbols]

 1 Glass Substrate 2 Glass Substrate 3 Transparent Electrode 4 Transparent Electrode 5 Ferroelectric Liquid Crystal Polymer 6 Ferroelectric Liquid Crystal Polymer 7 Low-Molecular Ferroelectric Liquid Crystal 8 Photoconductive Layer 9 Reflective Pixel Electrode 10 Display Element 11 Photo-Writable Spatial Light Modulation Element 12 Optical writing type spatial light modulator

Claims (6)

[Claims] 1. A liquid crystal display device that performs display operation by molecular inversion by applying a voltage, and has a ferroelectric liquid crystal polymer layer on the surface of a transparent substrate, and a low molecular ferroelectric liquid crystal is sealed inside the layer. A display element characterized by the above. 2. The display device according to claim 1, wherein the low-molecular-weight ferroelectric liquid crystal layer is sandwiched between a first ferroelectric liquid crystal polymer layer and a second ferroelectric liquid crystal polymer layer. 3. The display device according to claim 1, further comprising a layer composed of a low molecular weight ferroelectric liquid crystal and a ferroelectric liquid crystal polymer between a pair of transparent substrates. 4. The display device according to claim 1, comprising a photoconductive layer and a layer composed of a low-molecular-weight ferroelectric liquid crystal and a ferroelectric liquid crystal polymer between a pair of transparent substrates. 5. The display element according to claim 1, wherein the organic group of the side chain constituting the ferroelectric liquid crystal polymer and the chemical structure of the low molecular weight ferroelectric liquid crystal are substantially the same. 6. A method of manufacturing a display element, which comprises stretching the ferroelectric liquid crystal polymer, forming the ferroelectric liquid crystal polymer layer on the surface of the transparent substrate, and then assembling the display element.