JPH0469645B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a spacer used to define a gap of about 0.1 to 100 μm.

In particular, the present invention relates to a spacer suitable for defining the distance between electrodes in a liquid crystal display device.

[Prior Art] In general, a liquid crystal display device consists of a liquid crystal sealed between two electrodes, at least one of which is made of a transparent material, and the electrodes are spaced apart from each other in order to maintain a uniform thickness of the liquid crystal layer. It is constructed by interposing a spacer between the electrodes to define a distance. Conventionally, such a spacer is a spherical substance made of glass fiber or a resin such as glass, silica, or polystyrene and having a diameter corresponding to the thickness of the liquid crystal layer.

However, when glass fibers are used as spacers, it is difficult to prevent some of the fibers from becoming entangled or overlapping each other, making it difficult to define a predetermined gap with high precision. Further, when the above-mentioned spherical substances are used as spacers, it is difficult to make the particle diameters of these spherical substances uniform, and therefore it is also difficult to define a predetermined gap with high precision.

In a liquid crystal display device, if the thickness of the liquid crystal layer is non-uniform, (a) interference colors may differ locally, so-called color unevenness, and (b) the electric field strength applied to the liquid crystal layer may become uneven. As a result, the contrast ratio is not uniform, and (c) the response speed is proportional to the square of the thickness of the liquid crystal layer, so the response speed is not uniform. is required to have high first accuracy.

The second necessary condition for spacers in liquid crystal display devices is that the spacers should not cohere with each other.

Spacers are generally produced by blowing them away with an air current and dispersing them in the form of dust, as shown in USP4458988.
This is received on the inner surface of the display board and distributed evenly.
It is manufactured by assembling and sealing the opposing sides of other display boards together.

At this time, if the spacer has cohesive properties, it will scatter as several to several dozen secondary agglomerates, and even if the spacer particles have a uniform diameter, the accuracy of defining the gap will be poor.

Up until now, ordinary polymer particles have had a high aggregation property, especially in fields where the particle size is small, such as 4 μm.
This problem became more serious below m.

[Problems to be Solved by the Invention] The present invention has been made against the above-mentioned background, and its purpose is to have a spherical shape, a uniform particle size, and even a small particle size. An object of the present invention is to provide spacer particles for a liquid crystal display device that exhibit less particle agglomeration.

[Means for Solving the Problems] The method for manufacturing a spacer for a liquid crystal device (hereinafter simply referred to as a spacer) of the present invention is characterized by the following:
After absorbing a radically polymerizable monomer containing a fluorine-based monomer with a fluorine content of 15% or more into seed polymer particles, polymerization is performed in an aqueous dispersion to obtain particles with a particle diameter of 0.1 to 100 μm and a standard deviation value of the particle diameter. The object of the present invention is to obtain fluoropolymer particles having a fluorine content of 7% or more, which is 10% or less of the average particle diameter. The spacer of the present invention is suitably used after being dispersed in a fluorine-based solvent. This is useful for preventing agglomeration when the spacer is a small particle, especially when it is 4 μm or less.

The spacer of the present invention is manufactured by the following method.
That is, after a lipophilic substance is absorbed into seed polymer particles dispersed in an aqueous dispersion medium, a monomer containing a fluorine-based monomer is finely dispersed, preferably smaller than the seed polymer particles, and absorbed into the seed polymer particles. By polymerizing with an oil-soluble initiator, the particle size
Fluoropolymer particles having a uniform particle diameter of 0.1 to 100 μm, a standard deviation value of the particle diameter of 10% or less of the average particle diameter, and a fluorine content of 7% by weight or more are produced.

The present invention will be explained in detail below.

The method for manufacturing the spacer of the present invention is preferably as follows. In an aqueous dispersion in which seed polymer particles having a highly uniform particle system are dispersed in water in advance, a monomer containing a fluorine-based monomer having a fluorine content of 15% or more is absorbed into the seed polymer particles, and then It is obtained by polymerization using an oil-soluble initiator at a temperature of 40 to 100°C, preferably 50 to 80°C.

Here, the oil-soluble initiator is added to the seed polymer particles,
Preferably, it is pre-impregnated or absorbed into the seed polymer particles.

The average particle diameter of the fluorine-based polymer particles thus obtained can be estimated by the following formula.

Average particle diameter Average particle diameter (μm) = Polymerization yield (%) / 100 × [total weight of monomer / total weight of seed polymer particles] ^1/3 × (average particle diameter of seed polymer particles (μm)) The particle size of the base polymer particles can be controlled by selecting the particle size of the seed polymer particles, and furthermore, using the fluorine-based polymer particles obtained by the above process as the seed polymer particles, By repeating the process, large-diameter fluorine-based polymer particles can be formed.
A spacer having a desired particle size can be obtained within the range of 0.1 to 100 μm, preferably 0.5 to 30 μm. Furthermore, since the fluorine-based polymer particles have a particle size distribution corresponding to the particle size distribution of the seed polymer particles, in order to obtain spacers with uniform particle sizes, particles with a narrow particle size distribution are used as the seed polymer particles. There is a need.

The seed polymer particles used in the production of the spacer are not particularly limited as long as they can be swollen with the monomer used in the present invention, and may be ordinary polymer latex, polymer emulsion or polymer dispersion. Specifically, polystyrene made by emulsion polymerization, styrene-butadiene copolymer, carboxyl-modified styrene-butadiene copolymer, acrylic polymer, acrylic copolymer, polybutadiene, vinyl acetate polymer, vinyl chloride polymer Examples include merging.

As mentioned above, it is necessary to use seed polymer particles having a uniform particle size, and in order to obtain such seed polymer particles, for example, AR Goodalletal,
J.Polym.Sci.Polm Chem Editionvol 15,
The technique disclosed in P.2193 (1977) can be used.

What is the fluorine-based monomer used for polymerization of fluorine-based polymer particles?The content of fluorine element in the molecule
It is a monomer capable of radical polymerization in an amount of 15% by weight or more, preferably 33% by weight or more.

Specifically, 2,2,2-trifluoroethyl acrylate, 2,2,3,3-tetrafluoropropyl acrylate, 2,2,3,3,4,4,
5,5-octafluoroimyl acrylate,
Fluoroalkyl acrylates or methacrylates such as 1H, 1H, 2H, 2H-heptadecafluorodecyl acrylate are preferred.

In addition, trifluorochloroethylene, vinylidene fluoride, trifluoroethylene, tetrafluoroethylene, trifluoropropylene, hexafluoropropene, hexafluoropropylene, and the like can be used. There are no particular restrictions on the non-fluorinated monomers used in combination with these fluorinated monomers as long as they can be copolymerized with the above-mentioned fluorinated monomers. Specific examples include styrene, α-methylstyrene, p-methylstyrene, halogenated styrene, divinylbenzene, aromatic vinyl monomers such as 4-vinylpyridine, vinyl esters such as vinyl acetate and vinyl propionate, and acrylonitrile. Unsaturated nitriles such as methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, butyl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, lauryl acrylate, lauryl methacrylate, ethylene glycol diacrylate, ethylene glycol dimethacrylate , N,N-dimethylaminoethyl methacrylate and other ethylenically unsaturated carboxylic acid alkyl esters.

Conjugated diolefins such as butadiene and isoprene can also be used.

In addition, acrylamide, methacrylamide, glycidyl acrylate, glycidyl methacrylate, N-methylol acrylamide, N-
Diallyl phthalate, allyl acrylate, allyl methacrylate, etc., such as methylol methacrylamide, 2-hydroxyethyl acrylate, and 2-hydroxyethyl methacrylate, can also be used depending on the purpose. Furthermore, acrylic acid, methacrylic acid, itaconic acid, fumaric acid, and the like can be used as necessary in a proportion that does not inhibit swelling polymerization.

In addition, polyfunctional vinyl monomers such as divinylbenzene, ethylene glycol diacrylate, and ethylene glycol dimethacrylate are contained in an amount of 0.5% by weight or more, preferably 1 to 40% by weight based on the total monomers.
When used in combination, it prevents the fusion of soft polymer particles and increases the hardness and stiffness of the particles, making them preferable as spacers.

However, the amount of fluorine-based monomer used based on the total monomers is such that the fluorine content of the polymer after polymerization is 7.
The content is determined to be at least 10% by weight, preferably at least 10% by weight, and more preferably at least 20% by weight. If the fluorine content in the polymer is less than 7% by weight, the effect of improving particle cohesion is insufficient.

In order to absorb these monomers into the aforementioned seed polymer particles, finely dispersing these monomers in water together with a small amount of surfactant will ensure that the monomers are absorbed quickly and no unabsorbed monomer remains, resulting in a uniform particle size of the resulting polymer. It is preferable.

As a means of fine dispersion, ultrasonic homogenizer,
Examples include high-pressure piston type homogenizers.

Further, it is preferable to absorb a highly lipophilic substance in advance into the seed polymer particles before absorbing the monomer, since this facilitates the absorption of the monomer.

Highly lipophilic substances are substances with a solubility in water of 0.02% by weight or less, and specifically include 1-chlordodecane, octanoyl peroxide, lauroyl peroxide, 3,5,5-trimethylhexanoyl peroxide, and dioctyl adipate. , isoparaffin, etc.

In the polymerization of fluorine-based polymer particles, it is preferable to add a suspension protectant in order to increase the stability of the polymer particles during and after polymerization.

Suspension protectants include polyvinyl alcohol, carboxymethyl cellulose, polyacrylates, and finely powdered inorganic compounds. In addition, it is possible to use a small amount of surfactant to improve stability, but if it is too large, small-sized polymer particles will be generated during polymerization, making it difficult to obtain homogeneous polymer particles. .

The polymerization initiator used in the production of the polymer particles is an oil-soluble polymerization initiator, such as azobisisobutylnitrile, benzoyl peroxide,
Examples include 2,4-dichlorobenzoyl peroxide, dioctanoyl peroxide, di-3,5,5-trimethylhexanoyl peroxide, and lauroyl peroxide, which may be used alone or in combination. The oil-soluble polymerization initiator is usually dissolved in the monomer or solvent beforehand and added to the polymerization system.

Note that if the seed polymer particles are made to absorb a lipophilic substance before adding the monomer, or if an organic peroxide such as octanoyl peroxide or lauroyl peroxide is used as the lipophilic substance, no additional initiator is required. good.

In the polymerization of polymer particles, if a water-soluble polymerization initiator such as hydrogen peroxide or potassium persulfate is used, a large amount of small-sized polymer particles are generated, making it impossible to obtain homogeneous polymer particles.

Further, during polymerization, a polymerization regulator such as carbon tetrachloride and t-dodecylmercaptan, and a water-soluble polymerization inhibitor such as sodium nitrite, hydroquinone, and N,N-diethylhydroxylamine may be added.
The presence of a water-soluble polymerization inhibitor is effective in suppressing the generation of small-sized polymer particles.

In the present invention, the particle size of the spacer is 0.1 to 100 μm, preferably 0.5 to 30 μm, and more preferably 0.7 to 10 μm.
It is m. If it is smaller than 0.1 μm, even if the spacer is made of fluorine-based polymer particles, agglomeration of particles will occur, and the effect of improving fluidity will be small.

Incidentally, it is also possible to improve the powder flowability by mixing fine particle silica which has been subjected to a lipophilic treatment to the fluorine-based polymer particles.

By adsorbing or adhering a dye or pigment to the surface of the spacer obtained by the present invention, it is also possible to make the presence of the spacer visible or invisible in the liquid crystal display device.

Furthermore, although the spacers obtained in the present invention are distributed on the liquid crystal display panel by a dry method, it goes without saying that they can also be uniformly distributed by spraying a liquid dispersed in a solvent.

At this time, it is preferable to use a fluorine-based solvent as the solvent because it is compatible with the fluorine-based polymer particles.
As a fluorine-based solvent, the fluorine content in the molecule is
The amount of solvent is 15 wt% or more, preferably 25 wt% or more. Specific examples include perfluoropropane, benzotrifluoride, perfluorobenzene, Freon 113, and Freon gas RC318.

The method of using the spacer obtained in the present invention as a dispersion in a solvent is preferable for distributing small-sized particles on a liquid crystal display panel with good reproducibility without particle agglomeration, and the method is preferable for distributing small-sized particles on a liquid crystal display panel with good reproducibility, and the particle size is 4 μm or less, particularly 0.5 to 3 μm. in the case of,
Its effectiveness is high.

Note that the spacer obtained in the present invention can also be used by being mixed with a resin such as epoxy resin used as a sealing material for the edge of a liquid crystal display device.

Examples of the present invention will be described below.

In the following description, "parts" and "%" represent parts by weight and % by weight, respectively.

Example 1 2 parts of lauroyl poroxide (“Perloyl L” manufactured by NOF Corporation), sodium lauryl sulfate
0.15 parts and 20 parts of water were emulsified using an ultrasonic homogenizer and finely dispersed so that the maximum diameter of oil droplets was 0.4 μm or less.

The particle size of this dispersion as a seed polymer particle is
The dispersed oil droplets were added to a mixture consisting of 5 parts of 0.75 μm monofractional polystyrene latex (10% solids concentration) and 6 parts of acetone, and the system was gently stirred at 25°C for 4 hours to form dispersed oil droplets into seed polymer particles. I let it absorb.

Next, 60 parts of 2,2,3,3,4,4,5,5-octafluoroamyl methacrylate (“Viscoat 8FM” manufactured by Osaka Organic Chemical Industry Co., Ltd.), 10 parts of divinylbenzene, 30 parts of styrene, lauryl 2 parts of sodium sulfate and 300 parts of water were finely dispersed using a high-pressure piston homogenizer (Manton Gaulin type 15M) to a maximum droplet diameter of 0.4 μm or less, and added to the seed polymer particle dispersion. After gentle stirring at 25° C. for 1 hour, the monomer was completely absorbed into the seed polymer particles.

Add 200 ml of 5% aqueous solution of polyvinyl alcohol to this.
The polymerization was carried out at 80℃ for 4 hours, thoroughly washed with water, and dried to obtain uniform particle size bodies with a yield of 98% and a particle size of 4.4 μm and a particle size standard deviation value of 2.5% of the average particle size. Raw polymer particles were obtained.

The fluorine content of this polymer was determined by elemental analysis.
It was 30.1% by weight.

Next, in order to examine the non-agglomeration properties of these particles, the following test was conducted.

Approximately 10 mg of the smooth powder obtained by washing and drying the particles of Example 1 was placed on one end of a 20 cm x 20 cm glass plate, and when a blower with a brush for cleaning camera lenses was blown, the particles formed into a mist and danced around the glass. It spread evenly inside and outside the board.

When the particles on the glass plate were observed with an optical microscope, they were found to be uniformly dispersed, with approximately one particle present each.

Examples 2 and 3 8 0.5 μm single fraction polystyrene latex (solid content concentration 10%) was used as the seed polymer particles.
Fluorine-based polymer particles (Example 2) having a particle size of 2.5 μm and a particle size standard deviation value of 2.5% of the average particle size were prepared in the same manner as in Example 1 except that the parts were 320 parts and 320 parts. Fluoropolymer particles (Example 3) having a particle size standard deviation value of 3.0% of the average particle size were obtained.

When the free-flowing powder obtained by washing and drying the particles was subjected to the above-mentioned lens blower test, it was found that it spread uniformly inside and outside the glass plate and was in a good dispersion state.

However, when observed with an optical microscope, in Example 2, 2 to 3 aggregated particles were observed, about 1 in every few tens of particles, and in Example 3, 2 to 3 aggregated particles were observed, about 1 in every few particles. Ta.

When a liquid crystal display panel was formed using these powder particles, the agglomerated particles seemed to have been loosened by the pressure during the assembly of the display panel, and the display panels formed in both Examples 2 and 3 had no Newton rings and were uniform. It was found that the thickness was ensured.

Next, 10 g of each of the particles of Examples 2 and 3 and 200 g of a fluorine-based solvent (Daikin Corporation Daiflon S-3) were added.
g were mixed and irradiated with ultrasonic waves for 5 minutes to uniformly disperse the mixture.

The state of dispersion was good in both cases.

When this was sprayed onto a liquid crystal display panel using an air sprayer to volatilize the fluorine-based solvent and observed under a microscope, it was found that in both Examples 2 and 3, approximately one particle each was present on the display panel.

Comparative Example 1 Uniform particles with a particle size of 4.2 μm and a standard deviation value of particle size of 3% of the average particle size were prepared in the same manner as in Example 1 except that 90 parts of styrene and 10 parts of divinylbenzene were used as monomers. Polymer particles of the same diameter were obtained.

When the above test using the lens blower was performed, the particles were scattered on the glass plate in the form of agglomerates in several places, and the distribution was not uniform.

Next, in order to examine the performance of the spacers of Examples 1 to 3, three types of liquid crystal display devices having the configurations shown in FIG. 1 were formed. In the liquid crystal display device, indium oxide was used as the transparent conductive film, and biphenyl nematic liquid crystal was used as the liquid crystal material.

It was confirmed that in all such liquid crystal display devices, the interference color was uniform, and the liquid crystal layer was defined to have a uniform thickness with high precision.

For reference, when a liquid crystal display device was similarly formed using the polystyrene particles (4.2 μm) obtained in Comparative Example 1 as spacers, the interference colors were partially different and color unevenness occurred.

In addition, (a) polystyrene particles obtained by normal suspension polymerization with an average particle diameter of 5.2 μm and a standard deviation of particle diameter of 2.1 μm are used as spacers, and (b) diameter
When a liquid crystal display device was similarly formed using a columnar body formed by cutting 7 μm glass fiber to a length of 50 μm as a spacer, the interference colors were partially different, resulting in color unevenness.

[Effects of the Invention] According to the method of the present invention, it is possible to provide a spacer for a liquid crystal device that is perfectly spherical, has a uniform particle diameter, and has extremely low particle aggregation.

As a result, a liquid crystal display device having a spacer having a smaller gap than conventional ones, especially 4 μm or less when dispersed in a fluorine-based solvent, can be easily put into practical use.

The spacer according to the present invention is suitably used not only for ordinary liquid crystal displays, but also as a liquid crystal spacer for ferroelectric liquid crystals, wide viewing angle liquid crystals, liquid crystals for wall-mounted color televisions, and the like.

[Brief explanation of drawings]

FIG. 1 is an explanatory cross-sectional view schematically showing a liquid crystal display device. 11, 12... Non-conductive transparent plate, 21, 22...
...Transparent conductive film, E1, E2... Electrode plate, 3... Spacer, 4... Seal material, 5... Liquid crystal layer.

Claims (1)

[Claims] Type 1 polymer particles have a particle diameter of 0.1 to 100 μm and are characterized by being polymerized in an aqueous dispersion after absorbing a radically polymerizable monomer containing a fluorine-based monomer having a fluorine content of 15% or more. A method for producing spacer particles for a liquid crystal display device comprising fluoropolymer particles having a standard deviation value of 10% or less of the average particle diameter and a fluorine content of 7% or more.