JP3048506B2 - Liquid crystal display element spacer and 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 spacer for a liquid crystal display device having excellent water dispersibility and a liquid crystal display device.

[0002]

2. Description of the Related Art A liquid crystal display device is manufactured by opposing two transparent substrates with electrodes with a predetermined gap therebetween via a spacer, and sealing liquid crystal in the gap. As the spacer, polymer particles and polymer fibers, glass particles and glass fibers are used.

[0003] This type of spacer is usually uniformly dispersed in a single particle form on one substrate, and the above liquid crystal display device is manufactured using the substrate to which the spacer is attached. The dispersion of the spacers is usually performed by dispersing the spacers in a dispersion medium made of freon, applying this dispersion on a substrate, drying the dispersion, and evaporating the freon (see, for example, JP-A-1-293316). .

[0004]

However, freon has environmental problems such as depletion of the ozone layer, and in recent years regulations on freon have become strict, and attempts have been made to use harmless water as a dispersion medium. However, the conventional spacer for a liquid crystal display element has low hydrophilicity, and when water is used as a dispersion medium, it cannot be uniformly dispersed on a substrate. There is a problem that the display quality of the display element is deteriorated.

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems. It is an object of the present invention to provide a spacer for a liquid crystal display element which has excellent water dispersibility and can be uniformly dispersed on a substrate using water as a dispersion medium. It is to provide a liquid crystal display device using the same.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a spacer for a liquid crystal display element having a negative zeta (ζ) potential, an average particle diameter of 1 to 100 μm, and a coefficient of variation of the particle diameter of 5% or less. It can be achieved by using.

As the spacer for the liquid crystal display element according to the first aspect of the present invention, polymer particles are generally used. Examples of the spacer include a vinyl polymer, a polyester resin, an alkyd resin, a silicon resin, and a fluorine resin. And the like. These polymer particles may be of a non-crosslinked type, but a crosslinked type having good heat resistance is preferred.

The above-mentioned vinyl polymer particles are obtained by polymerization of a vinyl monomer. To obtain non-crosslinked vinyl polymer particles, for example, styrene, vinyl toluene,
Acrylonitrile, alkyl (meth) acrylate, vinyl acetate, (meth) acrylic acid, hydroxyalkyl (meth) acrylate, (meth) acrylamide,
Vinyl monomers such as N-methylol (meth) acrylamide and N, N-dimethylaminoalkylacrylamide are used.

In order to obtain crosslinked vinyl polymer particles, the following vinyl monomers (1) to (4) are mainly used.

(1) Y methylolalkyl Z (meth) acrylate (where Y and Z are integers satisfying the condition of Y ≧ Z ≧ 2), for example, tetramethylolmethanetetra (meth) acrylate, tetramethylolmethanetriacrylate (Meth) acrylate, tetramethylolmethane di (meth) acrylate, trimethylolpropane tri (meth) acrylate, dipentaerythritol hexa (meth) acrylate, dipentaerythritol penta (meth) acrylate, glycerol tri (meth) acrylate, glycerol di (Meth) acrylate and the like.

(2) Polyoxyalkylene glycol di (meth) acrylates such as polyethylene glycol di (meth) acrylate and polypropylene glycol di (meth) acrylate. Also,
(3) Triallyl (iso) cyanurate, triallyl trimellitate and the like, (4) divinylbenzene, diallyl phthalate, diallyl acrylamide and the like.

These non-crosslinked and crosslinked vinyl monomers may be used alone or in combination of two or more. Further, a non-crosslinked vinyl monomer and a crosslinked vinyl monomer may be used in combination. When two or more vinyl monomers are used as a mixture, a copolymer is obtained.

The liquid crystal display element spacer according to the first aspect of the present invention must have a negative zeta potential (ζ). A spacer having a positive zeta potential (ζ), such as a conventional spacer, has low hydrophilicity and cannot be uniformly dispersed on a substrate when water is used as a dispersion medium.

In particular, the water dispersibility of the spacer particles is increased,
In order to improve uniform distribution and adhesion on the substrate,
A spacer having a zeta potential (ζ) of 10 mV or less is preferable, and a spacer having a zeta potential (ζ) of -20 mV or less, further preferably -40 mV or less is used.

The zeta (ζ) potential of the spacer particles is as follows:
When a solid and a liquid that are in contact with each other make relative movement, the potential difference is generated at the interface between the two.For example, using a streaming potential measuring device ZP-10B manufactured by Shimadzu Corporation, spacer particles were filled on filter paper. When an electrolyte solution is flushed through the layer under a constant pressure, a potential difference generated at both ends of the layer, that is, a streaming potential is measured, and ζ = 4πηκE /
It can be calculated by the formula of PD. Here, ζ is the zeta potential, E is the streaming potential, P is the pressure applied to the solution, η is the viscosity of the solution, κ is the electrical conductivity of the solution, and D is the dielectric constant.

Such a spacer particle is a vinyl monomer having a carboxyl group or a hydroxyl group, particularly a vinyl monomer containing a vinyl monomer having a carboxyl group among the above-mentioned monomers. By polymerizing, the zeta potential (ζ) of the particles can be largely changed in the negative direction. When a vinyl monomer containing a nitrogen-containing vinyl monomer is used, the zeta potential (ζ) fluctuates in a positive direction. Therefore, use of a large amount of the zeta potential (ζ) should be avoided.

Incidentally, even a spacer particle having no negative zeta potential (ζ) can be given a negative zeta potential (ζ) by performing a surface treatment. As a surface treatment method, for example, a method of using a silane coupling agent or the like and forming a thin film derived from the silane coupling agent or the like on the surface of the spacer particles to have a negative zeta potential (ζ) or the like. No.

Further, the spacer for a liquid crystal display element according to the present invention has an average particle diameter of 1 to 100 μm and a coefficient of variation of the particle diameter of 5% or less. Here, the coefficient of variation of the particle size is a ratio of standard deviation / average particle size expressed as a percentage.

The particle size of the spacer determines the gap between the two substrates constituting the liquid crystal display element.
When spacer particles having a size of more than 00 μm are used, the gap becomes too thin or too thick, so that a clear display cannot be obtained, and the display quality of the liquid crystal display element is deteriorated. Further, when spacer particles having a variation coefficient of particle size exceeding 5% are used,
It becomes difficult to adjust the gap to a constant value, and color unevenness occurs during display, and the display quality of the liquid crystal display element deteriorates.

The spacer for a liquid crystal display element according to the first aspect of the present invention is configured as described above, but the spacer may be colored as required. As the coloring agent, carbon black, disperse dye, acid dye, basic dye, metal oxide and the like are used.

The spacer for a liquid crystal display element according to the first aspect of the present invention is manufactured, for example, by the following method. First, the vinyl monomer is suspended in fine particles in an aqueous medium. Water is generally used as the aqueous medium. In this aqueous medium, an appropriate amount of a water-soluble suspension stabilizer is usually dissolved or an appropriate amount of a poorly water-soluble suspension stabilizer is dispersed and used.

Examples of water-soluble suspension stabilizers include polyvinyl alcohol, polyacrylic acid, polymethacrylic acid, gelatin, methylcellulose, polymethacrylamide, polyethylene glycol, polyethylene oxide monostearate, sorbitan tetraoleate, and glycerin monooleate. And a water-soluble organic compound such as dodecylbenzenesulfonic acid.

Barium sulfate, calcium sulfate, barium carbonate, calcium carbonate, magnesium carbonate, calcium phosphate, magnesium phosphate colloid (a mixture of sodium diphosphate and sodium chloride), colloidal Insoluble inorganic compounds such as silica and aluminum oxide are used.

In order to suspend the vinyl monomer in the form of fine particles in the aqueous medium, for example, 200 to 1000 parts by weight of the aqueous medium is mixed with 100 parts by weight of the vinyl monomer.
This is stirred with a stirring blade. By changing the stirring speed of the stirring blade and the viscosity of the aqueous medium, it is possible to adjust the particle size and the particle size distribution of the suspended particles of the vinyl monomer.

To carry out suspension polymerization of a vinyl monomer, a radical polymerization initiator is added to the above suspension in advance, or
Alternatively, the radical polymerization initiator is added just before heating and heated to decompose the radical polymerization initiator and polymerize the vinyl monomer.

As the radical polymerization initiator, an ordinary oil-soluble radical polymerization initiator comprising an azonitrile compound or an organic peroxide is used. Examples of the polymerization initiator comprising an azonitrile compound include 2,2'-azobisisobutyronitrile, 2,2'-azobis-2,4'-dimethylvaleronitrile, and 2,2'-azobis-methylbutyronitrile. , 2,2'-azobis-methylheptonitrile and the like.

Examples of the radical polymerization initiator composed of an organic peroxide include acetyl peroxide, decanoyl peroxide, lauroyl peroxide, benzoyl peroxide, p-chlorobenzoyl peroxide, 2,4-dichlorobenzoyl peroxide, and peroxide. Diisopropyl carbonate, di-2-ethylhexyl peroxide carbonate, acetylcyclohexylsulfonyl peroxide, t-butyl isobutyrate, t-butyl peribarate,
T-butyl 2-ethylhexanoate, di-t-peroxide
Butyl, t-butyl cumyl peroxide, dicumyl peroxide and the like.

These radical polymerization initiators are generally used in the range of 0.5 to 15 parts by weight based on 100 parts by weight of the vinyl monomer. When the amount of the radical polymerization initiator is less than 0.5 part by weight, the polymerization rate is remarkably reduced, and the amount of the radical polymerization initiator exceeding 15 parts by weight is not required. The polymerization temperature varies depending on the type of radical polymerization initiator used, but is generally about 40 to 150 ° C. Further, the polymerization time is generally about 30 minutes to 15 hours.

In this way, polymer particles are formed, and the polymer particles are separated by means such as filtration or centrifugation, washed with water or the like, and then dried by heating or decompression. Is done. When it is necessary to adjust the average particle diameter and the coefficient of variation, the average particle diameter and the coefficient of variation are adjusted by means such as classification to obtain a spacer for a liquid crystal display element.

The liquid crystal display element according to the second aspect is the first aspect.
A liquid crystal display device using the spacer for a liquid crystal display device as described above, and is manufactured by a conventionally known method.

[0031]

The particle surface of a conventional spacer for a liquid crystal display element is generally negatively charged. However, since the degree of the charge is weak, the repulsive force between the negative charges is weak, so that the aggregation of fine particles in water is prevented. I do not reach. The zeta potential (ζ) of the particles shows a positive value even when measured.

As in the present invention, when the negative charges on the surface of the particles are increased so that the zeta potential (ζ) of the particles shows a negative value, the repulsive force between the negative charges becomes sufficient, and the fine particles are formed in water. No aggregation occurs, and the water dispersibility is significantly improved.

Further, since the variation coefficient of the particle diameter of the spacer particles of the present invention is controlled to 5% or less, the gap between the substrates is adjusted to be constant in the liquid crystal display device manufactured using the spacer particles. In this case, the color unevenness is eliminated and the display quality is improved.

[0034]

Next, the present invention will be described with reference to examples and comparative examples. Example 1 Production of spacer for liquid crystal display element Into a 5-liter separable flask equipped with a stirrer and a reflux condenser, 2.5 liter of a 5% aqueous solution of polyvinyl alcohol was placed, and 625 g of divinylbenzene (50 g) was added thereto.
Parts by weight), 625 g of dipentaerythritol hexaacrylate (50 parts by weight), benzoyl peroxide 1
A monomer solution in which 8.8 g was uniformly dissolved and mixed was charged, and the temperature was raised to 80 ° C. with stirring to carry out a polymerization reaction for 10 hours. Next, the mother liquor was separated and washed to obtain polymer particles of 6 to 15 μm. The polymer particles were classified into a desired particle size to obtain a spacer for a liquid crystal display element.

Measurement of Characteristics of Spacer for Liquid Crystal Display Element (1) Measurement of Average Particle Size and Coefficient of Variation The average particle size of the spacer for liquid crystal display element was measured using a particle size distribution analyzer (Coulter counter, manufactured by Coulter Electronics, UK). The diameter and the coefficient of variation were measured.

(2) Measurement of zeta (ζ) potential With respect to the spacer for the liquid crystal display element, the streaming potential was measured using a streaming potential measuring device (ZP-10B: Shimadzu Corporation), and the above-mentioned ζ = 4πηκE / It was calculated by the formula of PD.

(3) Measurement of water dispersibility The above-mentioned spacer for a liquid crystal display element was dispersed in pure water to prepare an aqueous dispersion (spacer concentration: 1% by weight). ^On a glass substrate having a surface area of 450 cm ² at a spray density of 120 particles / mm ² and dried, and the spacer particles are adhered on the glass substrate,
The number of lumps in which 5 or more particles aggregated per 6.3 mm ² and the number of lumps in which two or more particles aggregated were examined. Table 1 summarizes the above results.

Examples 2 to 5 and Comparative Examples 1 to 3 In Example 1, the vinyl monomers were changed as shown in Table 1. Other than that, it carried out similarly to Example 1. The results are summarized in Table 1.

[0039]

[Table 1]

Example 6 A solution prepared by dissolving 0.3 g of 2-acetoxyethyltrichlorosilane in 50 ml of toluene was composed of 50 parts by weight of dipentaerythritol hexaacrylate and 50 parts by weight of divinylbenzene, and had an average particle size of 6.48 μm and a coefficient of variation. 10 g of 5.56% crosslinked polymer spacer was immersed. The mixture was heated in a 55 ° C. water bath with stirring for 1 hour, and then filtered. The obtained filtration residue was heated in a dryer at 120 ° C. for 1 hour to obtain a spacer for a liquid crystal display element surface-treated with a silane coupling agent. When the zeta potential of the obtained spacer for a liquid crystal display element was measured, it was -45 mV.

Example 7 : Instead of 2-acetoxyethyltrichlorosilane, 3-
A liquid crystal display element spacer surface-treated with a silane coupling agent was obtained in the same manner as in Example 6 except that cyanopropyltrichlorosilane was used. When the zeta potential of the obtained spacer for a liquid crystal display element was measured, it was -50 mV.

Example 8 A liquid crystal display element surface-treated with a silane coupling agent in the same manner as in Example 6 except that triethoxysilylpropyl-p-nitrobenzamide was used instead of 2-acetoxyethyltrichlorosilane. A spacer was obtained. When the zeta potential of the obtained spacer for a liquid crystal display element was measured, it was -40 mV.

Table 2 shows the results obtained in Examples 6 to 8 above.

[0044]

[Table 2]

[0045]

As described above, the spacer for a liquid crystal display element according to the first aspect of the present invention has a negative zeta (ζ) potential, an average particle diameter of 1 to 100 μm, and a variation coefficient of the particle diameter of 5%.
The following is such a liquid crystal display element spacer having excellent water dispersibility, and in producing a liquid crystal display element, water is used as a dispersion medium of the liquid crystal display element spacer to uniformly form a single particle on an electrode substrate. Can be sprayed.

Therefore, according to the spacer for a liquid crystal display element of the first aspect of the present invention, environmental problems such as ozone layer destruction and the like are reduced as compared with a conventional liquid crystal display element spacer using Freon as a dispersion medium of the liquid crystal display element spacer. Does not occur.

Further, the spacer for a liquid crystal display element according to the first aspect of the present invention is manufactured using the spacer because the coefficient of variation of the particle diameter is controlled to 5% or less. The display element has a very high gap system between the substrates,
Color unevenness during display is eliminated and display quality is excellent.

Claims (2)

(57) [Claims] 1. A spacer for a liquid crystal display device having a negative zeta (ζ) potential, an average particle size of 1 to 100 μm, and a coefficient of variation of the particle size of 5% or less. 2. A spacer for a liquid crystal display element according to claim 1.
The liquid crystal display element characterized by chromatography is used.