JPH0392824A - Liquid crystal display element - Google Patents

Abstract

PURPOSE:To obtain a ferroelectric liquid crystal display element which can easily be manufactured and is improved in bistability by dispersing and incorporating conductive particulates at least one orienting film. CONSTITUTION:Transparent electrode substrates 5 and 6 are arranged having orienting films 3a and 3b opposite each other and ferroelectric liquid crystal 4 is charged between them. The orienting films 3a and 3b are formed by coating the transparent electrodes with coating liquid for orientating film formation wherein conductive particulates 7a and 7b are dispersed and incorporated by a normal method and drying the liquid, so the element can be manufactured in a process which is much easier than the formation of a vapor-deposited film and an LB film. Further, charges accumulated on border surfaces between the orienting films 3a and 3b, and liquid crystal 4 are discharged to an external circuit from transparent electrodes 2a and 2b, so the bistability is never disordered with interfacial charges. Consequently, the ferroelectric liquid crystal display element which can easily be manufactured and is improved in bistability is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of the Invention 1] The present invention relates to a liquid crystal display element. More specifically, the present invention relates to a ferroelectric liquid crystal display element with improved bistability.

[Technical Background of the Invention and Prior Art] Liquid crystal display elements conventionally used in watches, computers, word processors, etc. have, as their basic structure, two transparent electrode substrates with an alignment film provided on the transparent electrodes. Usually, the structure is such that the alignment film is placed on the inside and the liquid crystal is sealed between them. Generally, in a liquid crystal display element, it is necessary to align the fatigued crystals in a certain direction, that is, to align them. Orients crystal molecules.

The mainstream of such liquid crystal display elements is a twisted nematic (TN) mode display in which nematic liquid crystal has a twisted structure. However, this TN type liquid crystal display element has a slow response speed, currently limited to 20 milliseconds, which is a major problem when used in television panels etc. that require high-speed response. It has become.

In contrast, recently, ferroelectric liquid crystals with high-speed response are expected to open up a new field of displays.
being researched.

Ferroelectric liquid crystals not only respond quickly to changes in electric field, but also respond to changes in the applied electric field by taking either the first optically stable state or the second optically stable state, and by changing the voltage It also has the property of maintaining its state when no voltage is applied, that is, it has bistability (also called memory property). Therefore, in a liquid crystal display element using ferroelectric liquid crystal, it is only necessary to apply a pulsed voltage when switching between two states, so it is necessary to apply a pulsed voltage only when switching between two states.
There is no need for a power source or electronic circuit, and power consumption is reduced compared to conventional liquid crystal display elements.

In other words, a liquid crystal display element using ferroelectric liquid crystal can be said to be a liquid crystal display element that has a simple structure and achieves high-speed response.

The bistability of the above ferroelectric liquid crystal display element can be evaluated as follows. That is, a liquid crystal display element is placed under crossed nicols, a pulse is applied to bring it into a bright state, and the transmittance (■") is measured immediately after that. Furthermore, the transmittance after unit time (several milliseconds) has elapsed is A. After measuring (It,''), a pulse with the polarity reversed from the previous one is applied to create a dark state, and the transmittance (I-) immediately thereafter is measured. next,
The transmittance (■1) after a unit of time has passed is measured, and the following formula (
1) The memory property M (%) is calculated.

The above bistability in ferroelectric liquid crystal display elements is caused by the alignment state of the liquid crystal (initial alignment state) before applying the cantering voltage.
In the conventional liquid crystal display element, in which ferroelectric liquid crystal is sealed between alignment films made of rubbed polyimide, the memory performance is about 40 to 50%.
I couldn't say it was completely satisfying.

Several proposals have been made to solve these problems. For example, Japanese Unexamined Patent Publication No. 63-97917 discloses a liquid crystal display element in which the orientation of ferroelectric liquid crystal is controlled by obliquely depositing silicon dioxide to improve bistability. Although the bistability of this liquid crystal display element was certainly improved to some extent, the alignment film was formed by oblique evaporation, which required careful control in the manufacturing process, and compared to conventional coating methods. There is a problem in that it takes more time and effort than forming an alignment film.

JP-A No. 63-106626 discloses a strong 'r? , an electronic liquid crystal display element is disclosed. In addition, the Proceedings of the 14th LCD Symposium, p. Il2~p. 1. 3 describes a method for improving bistability by applying an alternating current electric field to a cell in which an alignment film is made of an amino-based silane coupling agent, polyvinyl alcohol, and polyimide.

The above-mentioned liquid crystal display element is a liquid crystal display element in which an alignment film is formed by coating, and the bistability has been improved to some extent, but in addition to the normal process, an electric field application process is performed. Therefore, the number of steps is increased, and there is a fear that the orientation may be disturbed by this electric field application process. Moreover,
Durability issues include problems with stability over time, such as bistability decreasing over time, and problems with heat and humidity resistance, such as orientation becoming disordered if left at temperatures of around 40°C and humidity of around 80% for several days. I was worried about sex.

Recently, charges due to impurity ions contained in liquid crystals accumulate at the interface between the alignment film and the liquid crystal during voltage reversal, and the charges accumulated at this interface (hereinafter referred to as interface burden) affect the bistability of ferroelectric liquid crystal display elements. It was found that this may cause the leakage. Based on this knowledge, an LB film (Lang
A liquid crystal display element with improved bistability has also been proposed (IEICE technical research report EID88-38, 1988, p. 25) using BIodget L115i). That is, the LB film can quickly release interfacial charges to an external circuit through tunneling or hopping conduction, so that the bistability of the liquid crystal display element can be improved. In addition, the LB film is conductive in the film thickness direction due to tunneling or hopping conduction, but it is insulating in the direction perpendicular to the film thickness (in-plane direction of the film), so it can be used as an electrode in stripes. Even when a matrix type display is created using electrodes, it has the advantage of not causing crosstalk.

A liquid crystal display element using an LB film as an alignment film has excellent properties as described above, but in order to manufacture such a liquid crystal display element, the complicated and highly sophisticated process of forming an LB film is required. It requires advanced technology and is extremely difficult to put into practical use industrially.

[Summary of the Invention] An object of the present invention is to provide a ferroelectric liquid crystal display element that can be easily manufactured and has improved bistability.

The above object is to provide a crystalline display element of the present invention in which two transparent electrode substrates each having an alignment film provided on a transparent electrode are arranged with the alignment film inside, and a ferroelectric liquid crystal is sealed between them. This can be achieved by a liquid crystal display element characterized in that conductive fine particles are dispersed and contained in at least one of the alignment films.

The alignment film of the liquid crystal display element of the present invention is formed by applying a coating liquid for forming an alignment film containing conductive fine particles dispersed thereon onto a transparent electrode by a conventional method and drying. LB. It can be manufactured through a much simpler process than forming a , and it is also easy to implement industrially.

The alignment film in which conductive particles are dispersed contains the above-mentioned LB[
Similarly, the film is conductive in the thickness direction, and the charge accumulated at the interface between the alignment film and the liquid crystal escapes from the transparent electrode to the external circuit through the alignment film, so the interfacial charge causes bistability. Never be left out. Further, like the above-mentioned LB film, the alignment film of the liquid crystal display element of the present invention is conductive in the thickness direction of the film, but insulating in the direction perpendicular to the film thickness (in-plane direction of the film). Therefore, even when a matrix type display is constructed using striped electrodes as electrodes, crosstalk does not occur.

Furthermore, the present inventors have discovered that the liquid crystal display element of the present invention is also excellent in durability.

That is, the liquid crystal display element of the present invention is a liquid crystal display element that has performance similar to that of an LB film, has an alignment film that can be produced more easily than an LB film, and has excellent durability.

Preferred embodiments of the present invention are listed below.

(1) Is the conductive particle on both sides of the two alignment films? A liquid crystal display element characterized in that the liquid crystal display element is dispersed in.

(2) The particle size of the conductive fine particles is 0.01 μm to 0.3 μm.
A liquid crystal display element characterized in that the size is μm.

(3> The particle size of the conductive fine particles is 0.03 μm to 0.2 μm.
A liquid crystal display element characterized in that the size is μm.

(4) A liquid crystal display element characterized in that the content of the tetraelectric particles is 1/2 to 1/300 in volume ratio to the entire alignment film.

(5) A liquid crystal display element, wherein the content of the conductive fine particles is 1/5 to 1/200 by volume of the entire alignment film.

(6) The conductive fine particles contain 0.00% antimony. 1~
20% doped tin oxide, aluminum 0.05~
A liquid crystal display element comprising at least one conductive inorganic oxide selected from the group consisting of 10% doped zinc oxide and non-stoichiometric titanium oxide.

(7) A liquid crystal display element, wherein the conductive particles are polymer beads represented by the following general formula [1] or [II].

Formula: However, in the above formula, each letter is A: a polymerizable monomer containing at least two ethylenically unsaturated groups B: a monomer containing a copolymerizable ethylenically unsaturated group M anion x: 1 to 20 Mol% Y: 0-96 Mol% Z: 10-
99 mol% Q: N or P , 0≦m≦6 R3:-Gol+2,. , O≦n≦6.

DESCRIPTION OF THE PREFERRED EMBODIMENTS [Structure of the Invention] The structure of the liquid crystal display element of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a sectional view showing an example of the liquid crystal display element of the present invention. Transparent electrodes g 2 a, 2 are placed on the transparent substrates 1a, 1b.
b, alignment films 3a and 3b are layered in this order to constitute transparent electrode substrates 5 and 6, respectively. Transparent electrode substrate 5
, 6 are arranged so that the alignment films 3a and 3b face each other, and a ferroelectric liquid crystal 4 is sealed between them. Conductive fine particles 7a, 7b, which are a characteristic feature of the present invention, are dispersed and contained in the alignment films 3a, 3b.

In the liquid crystal display element of the present invention, conductive fine particles do not necessarily have to be dispersed in both the upper and lower alignment films as shown in FIG. You can. However, it is preferable that it is dispersed and contained in both alignment films.

The liquid crystal display element of the present invention is not limited to the one shown in FIG.
All the embodiments used for ordinary liquid crystal display elements, such as providing a polarizing plate, are possible. In particular, it is preferable to use a spacer to ensure a gap between both alignment films (ie, the thickness of the liquid crystal layer). Glass fibers, glass beads, plastic beads, and metal oxide particles such as alumina and silica are used as the baser. The particle size of the baser varies depending on the liquid crystal used, the alignment film material, the setting of the cell gap, the particles used as the baser, etc., but is generally from 1.2 μm to 6 μm.

The alignment film, which is a feature of the liquid crystal display element of the present invention, will be described in detail below.

The liquid crystal display element of the present invention is characterized in that conductive fine particles are dispersed and contained in at least one of the two alignment films. Such an alignment film is made by, for example, containing conductive fine particles as described below dispersed in a polymeric material such as polyimide, polyamide, polyimide amide, or polyvinyl alcohol, which has been conventionally used as an alignment film material. It is what was done. The particle size of the conductive fine particles is 0.010.
3 μm is common, and preferably 0. o3・0.2 μm. In addition, the content is 1/2 by volume of the entire alignment film.
- 1/100 is common, 5, preferably 1/5 - 1/
It is 200.

As the conductive fine particles used in the present invention, O. Conductive inorganic oxides such as tin oxide doped with 1 to 20%, zinc oxide doped with 0.05 to 10% aluminum, and non-stoichiometric titanium oxide, or the following general formula [I]! or cationic or a:ionic polymer beads represented by [11].

The following formula 2A: Polymerizable monomer containing at least two ethylenically unsaturated groups B: Monomer M containing a copolymerizable ethylenically unsaturated group: Anion x: 1 to 20 mol% y: 0 to 96 Monore%Z: 10
~99 mol% Q: N or P X: cation y: -so3, -COO R': -Ck82klIO≦k≦6R
2:-CeaH2B+1 0≦m≦6R':
-Go+{2n. , 0≦n≦6.

The thickness of the alignment film varies depending on the liquid crystal used, but is preferably 200 to 2000.

Portions other than the alignment film used in the liquid crystal display element of the present invention,
In other words, transparent substrates, transparent electrodes, ferroelectric liquid crystals, etc.
All known materials that have been conventionally used in ferroelectric liquid crystal display elements can be used.

For example, as a transparent substrate, in addition to glass such as float glass with good smoothness, polyester such as polyethylene terephthalate and polybutylene terephthalate, epoxy resin, phenol resin, polyimide, polycarbonate, borisulfone, polyethersulfone, polyetherimide, acetyl cellulose, polyamino acid ester,
Made from heat-resistant resins such as aromatic polyamides, vinyl thread polymers such as polystyrene, polyacrylic esters, polymethacrylic esters, polyacrylamide, polyethylene, and polypropylene, fluorine-containing resins such as polyvinylidene fluoride, and modified products thereof. Plastic films may be mentioned.

Examples of the transparent electrode include indium oxide (In203), tin oxide (SnO2), and ITO (-1'ndium tin oxide).

Further, as the ferroelectric liquid crystal used in the present invention, conventionally known ferroelectric liquid crystals can be used.

Specifically, the liquid crystal having ferromagnetic cage properties is a chiral smectic C phase (SmC'). H phase (SmH'), I phase (SmH')
ml”).J phase (SmJ”). K phase (SmK”)
．． It is a liquid crystal having a G phase (SmG") or an F phase (SmF").

Examples of ferroelectric liquid crystals that can be used in the present invention are shown below.

Examples of ship base-based ferroelectric liquid crystals include the following ferroelectric liquid crystals: 85C2 (n=5 to 10, 12, 14) (n=7 to 10, 14) C113 (When x = ell3, xzC is necessary, when X = CN, n = 6 to 1 2, 14 n = 6, 8, 1 0, 14 n = 7 to 10, 14) (When i20, n = 7 when i=1, n=8).

In addition, examples of ship base liquid crystals into which hydroxyl groups have been introduced include the following.

(n=6, l　O1 1 4, 1 8) C2U5 (When m=1 When m=2 n=7 ~ 1 0 n=4~io).

Examples of Ship base-based ferroelectric liquid crystals using a secondary alcohol as an asymmetric source include the following.

(When m=1 When m=2 When m=3 When m=4 n=6, 8, 1 0, 1 4, 18n=8, 1
0, 14, 18 n = 1 0 n = 1 0) , CI13 Furthermore, examples of ferrolytic liquid crystals in which a halogen is directly bonded to an asymmetric carbon include the following.

The following margins (X=H, X=OH, X=H, , 9, 1 4 n = 1 O n = 10) 1 4 1 0, when X = OH n = 5, 6, 10, l4, 18)
.

Furthermore, in addition to the above, the following can be mentioned, for example.

CIl. CN ell3 C++3-C++-C++. CN In addition to the above, for example, "High Speed Liquid Crystal Technology J (published by CMC) 9. All known ferroelectric liquid crystals, such as those described in 127-161, can be used in the present invention.

In addition, as a specific liquid crystal composition, CS manufactured by Chisso ■
-1011, CS-1013, CS-1015, CS-
1022, CS-1023, CS-1026, ZLI-3488Zlr-3489, ZLI-40 manufactured by Merck & Co.
00, ZLI4237-000, ZLI-4237-1
00, FLEX-00 manufactured by Hoechst 1, FLEX-
005/1, FLEX-006/1, Roddick D
OF-004, DOF-006, H manufactured by Teikoku Kagaku Sangyo ■
Examples include S-98P and HS-78P (all product names), but are not limited thereto. There is no problem in adding dichroic dyes, viscosity reducers, etc. that dissolve in liquid crystals to these liquid crystals.

In the following, an example of manufacturing the liquid crystal display element of the present invention will be described in order.

Polymer materials conventionally known as alignment film materials, such as polyimide and its precursor polyamic acid, polyamide, polyvinyl alcohol, and polyimide amide, are applied onto a transparent electrode provided on a transparent substrate by a conventional method. Methyl-2-pyrrolidone, dioxane, THF,
A coating solution for forming an alignment film, in which conductive particles such as those described above are dispersed in a solution dissolved in a suitable solvent such as a glycol derivative, is applied using a spin coater or the like.

In addition to the above-mentioned components, this coating solution may contain other subcomponents such as high molecular weight polymers and organic metals for the purpose of increasing adhesion to the substrate or adjusting the viscosity of the coating solution. good. The coating may be performed directly on the transparent electrode, or an insulating layer may be provided on the transparent electrode and the coating may be applied thereon.

The coating film provided on the transparent electrode substrate has a temperature of 120°C to 30°C.
After heat treatment at 0° C., it is rubbed with synthetic fibers such as nylon, polyester, and polyacrylonitrile, and natural fibers such as cotton and wool.

A pair of transparent electrode substrates each having a transparent electrode substrate made of a transparent substrate, a transparent electrode, and an alignment film on at least one side, manufactured as described above, are placed facing each other with a gap between them, with the alignment film facing inside, and a cell is formed. shall be. The size of this gap,
That is, the cell gap is generally about 0.5 μm to 5 μm.

Next, ferroelectric liquid crystal is injected into this cell, sealed, and then slowly cooled.

In the manner described above, the liquid crystal display element of the present invention can be manufactured.

Of course, the liquid crystal display element of the present invention can be provided with structures provided in conventional liquid crystal display elements, such as a polarizing plate, an electrical insulating layer, and a color filter, depending on the purpose of use.

Next, examples of the present invention and comparative examples will be described. However, the present invention is not limited to this example.

[Example 1] Transparent electrodes made of indium-tin oxide (ITO) were formed in stripes (width of electrode: 300 μm, gap between electrodes: 30 μm) on each of two glass plates with a thickness of 1.1 mm. . A coating solution having the following composition was applied to both of the glass plates with the l-1-Q i electrode using a sinter.

Coating liquid: Antimony 10% dove tin oxide/water dispersion [25wt
．． %] (Mitsubishi Metals ■ Transparent Conductive Powder-1 was dispersed in water and coarse particles were removed by centrifugal sedimentation. Average particle size: 0.15μ
m) ...2.2 parts by weight polyvinyl alcohol (GL-OS manufactured by Japan Synthetic Rubber ■) ...3 parts by weight water
・ ・ ・ ・ ・ ・ The conditions for 100 parts by weight Schiner are: rotation speed 2500 r. p. m. , time 30
It was seconds. After coating, a film was formed by heating at 170° C. for 1 hour. The content of tin oxide was approximately 32% by volume relative to the entire alignment film.

Both coats were coated with a nylon roller.
A cell having a cell gap of 2 .mu.m was prepared by overlapping two glass plates with the rubbed surfaces facing inward and the rubbing direction being the same. In this cell, Merck Co., Ltd. (7) ZLI-3654 is installed.
The liquid crystal display device of the present invention was obtained by injecting the solution at 0.03 m and slowly cooling it to room temperature.

[Implementation @ 2 pieces] The liquid crystal display element of the present invention was prepared in the same manner as in Example 1, except that the coating liquid was as follows and the ferroelectric liquid crystal was ZLI-4237-100 manufactured by Merck & Co. I got it. Note that the content of the cationic polymer beads was approximately 12% by volume with respect to the entire alignment film.

Coating liquid: Cationic Bori 7-beads/water dispersion [20w
t. %] (However, this polymer has the following general formula [1]: A: Divinylbenzene B: None R+, R2, R3: All methyl x: 5
z:95 Q:N M:C [Average particle size: 0.1 μm]. )... 2 parts by weight polyvinyl alcohol (GL-05 manufactured by Nippon Gosei Rubber ■) ... 3 parts by weight organosol (70 wt.% liquid) (OS manufactured by Nikki Shokubai Kagaku ■ (:ALl232)...
1 part by weight Water 100 parts by weight [Example 3] The same procedure as in Example 1 was carried out except that the coating liquid was as follows and the ferroelectric liquid crystal was CS-1022 manufactured by Chisso ■. A liquid crystal display element of the present invention was obtained in the same manner as in Example 1. The content of the cationic polymer beads was approximately 5% by volume of the entire alignment film.

Coating liquid: Cationic polymer beads/methanol dispersion [17wt. %] (However, in the above general formula [1], A: ethylene glycol dimethacrylate B: None Rr, R2, Ry: All methyl x: 7
z:93 Q:NM:C angle [average particle size: 0.1 μm]. )...0.6 parts by weight polyimide/N-methylpyrrolidone solution [4.5 wt.
%] (Sunever 130 manufactured by Nissan Chemical ■) 44 parts by weight N-methylpyrrolidone 100 parts by weight [Comparative Example 1] In Example 3, cationic polymer beads were added to the coating solution. A fatigued crystal display element was obtained in the same manner as in Example 3 except that .

H 6.1 Examples 1 to 3 and Comparative Example 1 manufactured as above
The liquid crystal display element of
Memory performance was measured using a pulse of z. The results are shown in Table 1.

Table 1 Memory property (%) Example 1 Example 2 Example 3 9 5 8 5 85 Comparative example 1 4 0 It is also possible that the liquid crystal display element of the example has better durability than that of the comparative example. confirmed.

-l:. As is clear from the Examples and the measurement of memory properties, the liquid crystal display element of the present invention is a ferroelectric liquid crystal display element that can be easily manufactured and has improved bistability.

[Brief explanation of drawings]

FIG. 7g1 is a cross-sectional view schematically showing a configuration example of the liquid crystal display element of the present invention. 1 a, 1 b = 2a, 2b: 3a, 3b: 4: 5, 6: 7a, 7b: Transparent substrate, transparent electrode alignment film, liquid crystal transparent electrode substrate, conductive fine particles

Claims (1)

[Claims] 1. In a liquid crystal display element in which two transparent electrode substrates each having an alignment film provided on a transparent electrode are arranged with the alignment film inside, and a ferroelectric liquid crystal is sealed between them; at least one of the alignment films is , a liquid crystal display element characterized by containing conductive fine particles dispersed therein.