JP2000066212A - Spacer for liquid crystal display and liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide spacers for liquid crystal display which suppresses the occurrence of light escape around the spacers and the degradation in the contract of the panel in a liquid crystal display device using an IPS (transverse electric field drive) system. SOLUTION: The spacers are used for the liquid crystal display device of the transverse electric field drive system formed by holding liquid crystals between two sheets of substrates, which are arranged in a pair in parallel with each other via the spacers and at least, one of which are transparent, and in which the directions of the electric fields to be impressed on the liquid crystals are nearly parallel to the substrate boundaries. At this time, such spacers for liquid crystal display which are >=30 to <=85 deg. in the angle between the contact boundaries and the directors in the major axis direction of the liquid crystal molecules at the contact boundaries of the spacers and the liquid crystals and the liquid crystal display device using such spacers are provided.

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 of a type in which the direction of an electric field applied to a liquid crystal is substantially parallel to a substrate interface (lateral electric field driving type; hereinafter abbreviated as IPS type) and a spacer used therefor. The present invention relates to a spacer and a liquid crystal display device which can improve light leakage around a spacer when light of a liquid crystal panel is cut off, and can improve contrast of panel display.

[0002]

2. Description of the Related Art In a conventional liquid crystal display device, liquid crystal is switched by applying a direction of an electric field in a direction perpendicular to a substrate interface. On the other hand, in order to eliminate the viewing angle dependency, which is a drawback of the conventional liquid crystal display device, a liquid crystal is switched by applying a direction of an electric field in a direction parallel to a substrate interface.
S-mode liquid crystal display devices have been used.

Currently, a liquid crystal display device using the IPS system uses a TFT (thin film transistor) system. In the TFT liquid crystal panel using the IPS system, light leakage around the spacer, which did not occur in the conventional vertical electric field TFT panel, occurred, and there was a problem that the contrast of the panel was significantly reduced.

Heretofore, light leakage around the spacer has been remarkably generated in a conventional vertical electric field liquid crystal display device, particularly in the STN (super twist) mode, and liquid crystal molecules are vertically aligned on the spacer surface. Has been prevented. However, when a spacer for vertically aligning liquid crystal molecules on the spacer surface is used in an IPS type liquid crystal panel,
Although the surrounding light passage area is reduced, light passage cannot be completely prevented, resulting in a decrease in contrast.

[0005]

Means for Solving the Problems In the IPS mode liquid crystal display device, the state of light leakage around the spacer changes depending on the alignment state of the liquid crystal at the contact interface between the spacer and the liquid crystal, and the specific alignment It has been found that the above problem can be solved by using a spacer that shows a state.

That is, according to the present invention, the liquid crystal is sandwiched between two transparent substrates, at least one of which is arranged in parallel via a spacer, and the direction of the electric field applied to the liquid crystal is A spacer used in a liquid crystal display device of a lateral electric field driving system in a direction substantially parallel to a substrate interface. At a contact interface between the spacer and the liquid crystal, an angle between the contact interface and a director in a major axis direction of the liquid crystal molecule. Is 30 ° or more
Provided is a liquid crystal display spacer having an angle of 85 ° or less, and a liquid crystal display device using the same.

At the contact interface between the spacer and the liquid crystal, the angle between the contact interface and the director in the major axis direction of the liquid crystal molecules (hereinafter referred to as the tilt angle) is a value that can be measured by the following method. . <Method of Measuring Tilt Angle> On a glass substrate of a liquid crystal display device, two films having the same composition as the surface of the spacer are formed, and rubbing is performed by a usual method. The two substrates are bonded together via a spacer so that the rubbing directions of the two substrates are the same in a cell thickness of 10 μm. Subsequently, liquid crystal is injected to complete the liquid crystal panel. Using this cell, the "Journal of Applied Physic
s, Vol. 48, No. 5 (1977) "
The tilt angle of the liquid crystal is measured by NullMethod.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, by setting the tilt angle measured by the above method to 30 ° or more and 85 ° or less, light leakage around the spacer can be reduced and the contrast ratio of the panel can be improved. Preferably, the tilt angle is 40 ° or more and 80 ° or less, more preferably 50 ° or more and 75 ° or less, so that light leakage from around the spacer can be further reduced, and the contrast ratio of the panel can be further reduced. Can be improved.

The manufacturing method, composition and the like of the liquid crystal display spacer of the present invention are not particularly limited as long as the tilt angle measured by the above method is 30 ° or more and 85 ° or less. It is manufactured by a method of copolymerizing a monomer having a structure (functional group or the like) that develops a tilt angle, a method of coating the spacer surface with an alignment agent that develops the tilt angle, a method of forming irregularities on the spacer surface, or the like. be able to.

Examples of the monomer having a structure that exhibits the tilt angle include alkyl (meth) acrylates having 2 to 30 carbon atoms in the alkyl group, (poly) ethylene glycol (meth) acrylate, and (poly) ) Propylene glycol (meth) acrylate, (poly)
Modified ethylene glycol (meth) acrylate in which the ethylene glycol end is modified with a hydrophobic group such as an alkyl group or an acyl group having 1 to 30 carbon atoms, and the modified propylene glycol end of (poly) propylene glycol (meth) acrylate is Modified products modified with a hydrophobic group such as an alkyl group or an acyl group having 1 to 30 carbon atoms are exemplified.

Examples of the aligning agent for developing the tilt angle include an organic silane coupling agent, a titanium coupling agent, an organic metal complex such as a chromium carboxylate complex, an organic acid such as stearic acid, and hexadecyltrimethylammonium bromide. And quaternary ammonium salts.

The method of forming irregularities on the spacer surface may be a general method. For example, when polymer fine particles are used as the spacer, a method in which a solvent is allowed to coexist with a monomer to polymerize to obtain porous polymer fine particles may be used. Can be

However, since the tilt angle greatly differs depending on the type of the liquid crystal material used in the IPS type liquid crystal display device, it is necessary to set the composition of the spacer and the like in accordance with the liquid crystal material used. The structure to be made cannot be limited. Therefore, when synthesizing the spacer of the present invention, it is necessary to previously measure the tilt angles of various kinds of materials in the liquid crystal to be used, and to determine a structure which expresses the tilt angles satisfying the present invention.

The spacer used in the present invention is not particularly limited as long as it can be used as a spacer, and polymer beads, silica beads and the like can be used.

In the liquid crystal display device of the present invention, the above-described spacer is used, and the liquid crystal is sandwiched between two at least one transparent substrates arranged in a pair in parallel via the spacer. The substrate has an alignment film, pixel electrodes,
There are provided signal wiring electrodes, scanning wiring electrodes, common electrodes, thin transistors, and the like. When an electric field is applied, a so-called IPS method is applied between the pixel electrode and the common electrode so as to be substantially parallel to the substrate interface.

[0016]

EXAMPLES In the following examples, parts are by weight.

Example 1 (Measurement of tilt angle) 50 parts of divinylbenzene (purity 81%, DVB-810 manufactured by Nippon Steel Chemical Co., Ltd.), styrene 20
, A mixture of n-octyl acrylate 30 parts and benzoyl peroxide 5 parts was coated on a glass substrate and heated at 80 ° C.
Heating was performed for 15 hours to prepare two substrates on which films were formed. Using these two substrates, a cell for tilt angle measurement was manufactured using MLC-2027 manufactured by Merck as a liquid crystal. Using this, the tilt angle was measured in accordance with the above-mentioned “method for measuring the tilt angle”. As a result, it was 72 °.

(Synthesis of Spacer) Divinylbenzene 50
Part of styrene, 20 parts of styrene, 30 parts of n-octyl acrylate, and 5 parts of benzoyl peroxide in a mixture of polyvinyl alcohol (GH-17, manufactured by Nippon Synthetic Chemical Industry Co., Ltd .; saponification degree: 86.5 to 89 mol%). % Aqueous solution was added and finely dispersed, suspension polymerization was carried out at 80 ° C. for 15 hours under a nitrogen stream, and classification was performed to obtain crosslinked polymer fine particles having an average particle size of 6.01 μm and a standard deviation of 0.27 μm. The obtained crosslinked polymer fine particles were washed with ion-exchanged water and a solvent, and then isolated and dried to obtain a liquid crystal display spacer.

(Preparation of Panel and Measurement of Contrast Ratio) Using the spacers obtained above, a liquid crystal panel of the IPS system as shown in FIG. 1 was prepared. In FIG.
1 is a substrate, 2 is a transparent electrode, 3 is a polyimide alignment film, 4 is a sealing material, 5 is a spacer, 6 is a liquid crystal layer, and 7 is a polarizing plate. The rubbing directions of the polyimide alignment films 3 of the upper and lower substrates 1 are the same as each other, the angle between the rubbing direction and the direction of the applied electric field is 85 °, and the polarization transmission axis of one polarizing plate 7 is the same as the rubbing direction. The other was placed perpendicular to this. The liquid crystal used was MLC-2027 manufactured by Merck. When the periphery of the spacer of this panel was observed with a microscope, almost no light leakage around the spacer was observed, and the contrast ratio of the panel was 100 as measured by the following method.

A method for measuring the contrast ratio of the panel: A method in which He-Ne laser light is incident on the panel, and a transmittance-applied voltage curve is obtained by a method of detecting with a photodiode,
The contrast ratio was calculated therefrom.

Example 2 Measurement of tilt angle and liquid crystal display were performed in the same manner as in Example 1 except that 70 parts of divinylbenzene, 20 parts of 2-ethylhexyl methacrylate, 10 parts of methyl methacrylate, and 1 part of benzoyl peroxide were used. Of liquid crystal panel and synthesis of liquid crystal panel. As a result, the tilt angle is 55 °,
A liquid crystal display spacer having an average particle size of 4.5 μm and a standard deviation of 0.23 μm was obtained. Example 1 of the obtained liquid crystal panel
Observation with a microscope in the same manner as in Example 1 showed that almost no light leakage around the spacer was observed, and the contrast ratio of the panel was 95.

Example 3 70 parts of divinylbenzene, 20 parts of stearyl methacrylate,
Methyl methacrylate 10 parts, benzoyl peroxide 3
A tilt angle was measured, a liquid crystal display spacer was synthesized, and a liquid crystal panel was prepared in the same manner as in Example 1 except that the portion was used. As a result, the tilt angle was 78 ° and the average particle size was
A liquid crystal display spacer having a size of 5.9 μm and a standard deviation of 0.27 μm was obtained. When the obtained liquid crystal panel was observed with a microscope in the same manner as in Example 1, almost no light leakage around the spacer was observed, and the contrast ratio of the panel was 90.

Example 4 The tilt angle was measured in the same manner as in Example 1 except that 75 parts of divinylbenzene and 25 parts of lauryl methacrylate were used.
We synthesized liquid crystal display spacers and made liquid crystal panels. As a result, the tilt angle was 82 ° and the average particle size was 5.5.
As a result, a liquid crystal display spacer having a standard deviation of 0.23 μm was obtained. When the obtained liquid crystal panel was observed with a microscope in the same manner as in Example 1, almost no light leakage around the spacer was observed, and the contrast ratio of the panel was 85%.
Met.

Example 5 A tilt angle was measured, a spacer for liquid crystal display was synthesized, and a liquid crystal panel was prepared in the same manner as in Example 1 except that 75 parts of divinylbenzene and 25 parts of butyl methacrylate were used.
As a result, the tilt angle was 35 ° and the average particle size was 5.5 μ
Thus, a liquid crystal display spacer having a standard deviation of 0.23 μm was obtained. When the obtained liquid crystal panel was observed by a microscope in the same manner as in Example 1, almost no light leakage around the spacer was observed, and the contrast ratio of the panel was 80%.
Met.

Example 6 (Measurement of tilt angle) After polycondensation of tetraethoxysilane on a glass substrate, dodecyltriethoxysilane 5
This was immersed in 500 parts of dissolved hexane and heated at 50 ° C. for 3 hours. The obtained substrate was dried at 150 ° C. for 6 hours. Using this substrate, as a liquid crystal, MLC manufactured by Merck
A cell for tilt angle measurement was prepared using -2027. Using this, the tilt angle was measured in accordance with the above-mentioned “method for measuring the tilt angle”. The result was 45 °.

(Synthesis of spacer) An average particle diameter obtained by polycondensation of tetraethoxysilane is 4.15 μm, and a standard deviation is 0.21 μm.
100 parts of silica particles were immersed in 500 parts of hexane in which 5 parts of dodecyltriethoxysilane had been previously dissolved,
Heated for hours. The obtained particles were dried at 150 ° C. for 6 hours, washed with a solvent and dried again to obtain a spacer for liquid crystal display.

(Preparation of Panel and Measurement of Contrast Ratio) A panel was prepared using the obtained liquid crystal display spacer. The procedure was the same as in Example 1, except that ZLI-4792 manufactured by Merck was used as the liquid crystal. When this panel was observed with a microscope in the same manner as in Example 1, almost no light leakage around the spacer was observed, and the contrast ratio of the panel was 85.

Comparative Example 1 A tilt angle measurement and a spacer for liquid crystal display were performed in the same manner as in Example 1 except that 50 parts of divinylbenzene, 50 parts of styrene, and 1 part of 2,2-azobisisobutyronitrile were used. And the creation of a liquid crystal panel. As a result, the tilt angle was 21 °, the average particle size was 5.2 μm, and the standard deviation was 0.21 μm.
Was obtained. When this panel was observed with a microscope in the same manner as in Example 1, light leakage was observed from the entire periphery of the spacer, and the contrast ratio of the panel was 45.

Comparative Example 2 60 parts of divinylbenzene, 40 parts of stearyl methacrylate,
The measurement of the tilt angle, the synthesis of a liquid crystal display spacer, and the preparation of a liquid crystal panel were performed in the same manner as in Example 1 except that 3 parts of benzoyl peroxide were used. As a result, the tilt angle was 87 °, the average particle size was 5.8 μm, and the standard deviation was 0.24.
A μm liquid crystal display spacer was obtained. When this panel was observed with a microscope in the same manner as in Example 1,
Light leakage from around the spacer was observed, and the contrast ratio of the panel was 58.

[0030]

According to the present invention, in the IPS mode liquid crystal display device, light leakage around the spacer when light is blocked can be improved, and the contrast ratio can be increased.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a liquid crystal panel prepared in an example.

[Explanation of symbols]

 Reference Signs List 1 substrate 2 transparent electrode 3 polyimide alignment film 4 sealing material 5 spacer 6 liquid crystal layer 7 polarizing plate

Continued on the front page (72) Inventor Tetsuo Takano 1334 Minato, Wakayama-shi, Wakayama Prefecture F-term (reference) 2H089 LA07 LA19 LA19 MA04X PA05 QA05 SA10 TA02 TA07

Claims (2)

[Claims] 1. A liquid crystal is sandwiched between two transparent substrates at least one of which is arranged in parallel via a spacer, and a direction of an electric field applied to the liquid crystal is substantially at a substrate interface. A spacer used for a liquid crystal display device of a horizontal electric field driving method in which the direction is parallel, wherein at the contact interface between the spacer and the liquid crystal, the angle between the contact interface and the director in the major axis direction of the liquid crystal molecule is 30 ° or more. Liquid crystal display spacers that are less than 85 °. 2. A liquid crystal display device using the liquid crystal display spacer according to claim 1.