JPH0496902A - Preparation of crosslinked polymer fine particle - Google Patents

Abstract

PURPOSE:To prepare the subject fine particles having excellent adhesivity and dispersibility and useful as spacers for liquid crystal displays, etc., by subjecting a crosslinking monomer and a non-crosslinking monomer to an aqueous suspension polymerization reaction in the presence of a polymerization initiator. CONSTITUTION:When a crosslinkable monomer such as divinyl benzene (in an amount of 5-70wt.% based on all monomers) and a non-crosslinking monomer are subjected to an aqueous suspension polymerization reaction in the presence of a radical polymerization initiator, a hydrophilic monomer such as hydroxyethyl (meth)acrylate (preferably in an amount of 5-500 pts.wt. per 50 pts.wt. of the sum of the crosslinking and non-crosslinking monomers) is added to the polymerization reaction system at a time when the polymerization degree is <90% after the start of the polymerization, and polymerized to provide the objective fine particles.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for producing crosslinked polymer fine particles, and more particularly to a method for producing novel crosslinked polymer fine particles useful as spacers for liquid crystal displays and the like.

[Problems to be solved by conventional techniques and inventions] Conventionally,
In liquid crystal display panels, inorganic or organic particles having a predetermined particle size are used as spacers for liquid crystal display in order to maintain the parallelism of the panel.

The required performance as a spacer for liquid crystal display panels is as follows:
1) Narrow particle size distribution, 2) Sufficient strength,
3) Good adhesion to the liquid crystal panel surface. The reason why good adhesion to the liquid crystal panel surface is required in 3) is that if the spacer moves in the liquid crystal during panel fabrication, it will damage the polyimide alignment film on the electrode panel surface and inhibit the liquid crystal alignment in that area. An example of this is that it is done.

Among these properties, various methods have been tried with respect to particle size distribution and strength, and almost satisfactory levels have been reached, but no satisfactory performance has been obtained in terms of adhesion to the liquid crystal panel surface. There wasn't.

[Means to solve the problem]

The present inventors have conducted extensive studies on crosslinked polymer fine particles for use in liquid crystal display spacers that solve the above-mentioned drawbacks of the prior art and have excellent adhesion to electrode panel surfaces.
By providing a hydrophilic polymer layer on a relatively outer layer of crosslinked polymer fine particles to form a so-called core-shell structure, adhesion to polyimide membranes is significantly improved, and furthermore, dispersibility in water is significantly improved. They discovered this and completed the present invention.

That is, in the present invention, when a crosslinkable monomer and a non-crosslinkable monomer are subjected to aqueous suspension polymerization in the presence of a radical polymerization initiator, hydrophilic A method for producing crosslinked polymer fine particles, characterized in that polymerization is carried out by adding a monomer or by adding a hydrophilic monomer and a crosslinkable monomer, and a crosslinkable monomer and a non-crosslinkable monomer. When monomers are subjected to aqueous suspension polymerization in the presence of a radical polymerization initiator, nonionic hydrophilic monomers (and crosslinkable monomers) are added when the polymerization rate is less than 90% after the initiation of polymerization. The present invention provides a method for manufacturing a spacer for a liquid crystal display, characterized in that the spacer is added and polymerized.

In the present invention, when carrying out aqueous suspension polymerization of crosslinking monomers and non-crosslinking monomers in the presence of a radical polymerization initiator, the combination of crosslinking monomers and non-crosslinking monomers used is is styrene/divinylbenzene, styrene/
Combinations of styrenic monomers such as ethylene glycol dimethacrylate, styrene/diethylene glycol dimethacrylate, styrene/butadiene and crosslinking monomers; methyl (meth)acrylate/divinylbenzene,
Combining (meth)acrylic acid ester monomers such as methyl (meth)acrylate/ethylene glycol dimethacrylate, methyl (meth)acrylate/diethylene glycol dimethacrylate, and methyl (meth)acrylate/methylene bisacrylamide with crosslinkable monomers Combinations: Combinations such as combinations of vinyl monomers and crosslinkable monomers such as ethylene/butadiene, methyl vinyl ether/divinyloxybutane, vinyl acetate/divinyloxybutane, and vinyl chloride/divinylbenzene may be used. Yes, but not limited to these.

In the above combination, the amount of crosslinkable monomer used in the total monomers can be appropriately selected depending on the desired use and physical properties of the polymer fine particles, but when used as a spacer for liquid crystal display, 5% by weight or more in the monomer, especially 5-7
Preferably, it is 0%. If the amount of the crosslinkable monomer is less than the above amount, the strength of the resulting polymer fine particles will not be sufficient, which will cause color unevenness when incorporated into a liquid crystal display panel.

In the present invention, the polymerization rate of the above aqueous suspension polymerization is 90
%, a hydrophilic monomer and, if necessary, a crosslinking monomer and a polymerization initiator are added to carry out further polymerization. If this addition is made at a time when the polymerization rate is 90% or more, it is difficult to obtain the effects of the present invention, and depending on the amount added, irregularly shaped particles may be produced, which is not preferable.

On the other hand, the lower limit of the polymerization rate at the time of adding the hydrophilic monomer etc. depends on the type of hydrophilic monomer used and the combination of crosslinkable monomer/non-crosslinkable monomer. Therefore, an appropriate polymerization rate may be determined through experiments depending on the intended use of the resulting crosslinked polymer fine particles.

In addition, in this invention, the polymerization rate was calculated|required by the following gravimetric method.

That is, a certain weight of a dispersion liquid is sampled from a polymerization tank in which crosslinked polymer fine particles are being synthesized, and dispersed in a large amount of methanol (containing 1000 pps+ of hydroquinone methyl ether). The resulting precipitate is isolated by a method such as filtration or centrifugation, dried under reduced pressure, weighed, and calculated using the following formula.

The monomer weight (g) in the polymerization dispersion is the weight of the sampled dispersion (g) x the monomer concentration (%).

In the present invention, the hydrophilic monomer may be added by adding the monomer mixture as it is, or by adding an emulsion dispersed in an aqueous solution of a surfactant such as sodium lauryl sulfate using a homomixer or the like. .

In the present invention, as the hydrophilic monomer, a hydrophilic monomer soluble in water or an alcoholic organic solvent may be used. For example, hydroxyethyl (meth)acrylate, diethylene glycol mono (meth)acrylate, polyethylene glycol mono (meth)acrylate, glycerol mono (meth)acrylate, polyethylene glycol polypropylene glycol mono (meth)acrylate, butanediol mono (meth)acrylate, etc. (Meth)acrylic acid ester-based monomers; Examples include nonionic monomers such as N-vinylpyrrolidone and N-vinyloxazolidone.

In addition, anionic monomers such as sodium p-styrenesulfonate, 2-acrylamido-2-methylpropanesulfonic acid, acrylic acid, methacrylic acid, methallylsulfonic acid, methacryloxyethyl phosphate, N,
Cationic monomers such as N-dimethylaminoethyl methacrylate, N,N-dimethylaminopropylacrylamide, quaternary salt monomers thereof, N-(3-sulfopropyl)-N-methacryloxyethyl N,N-dimethyl Ammoniumhetaine, N(3-sulfopropyl)-
N-methacryloylamidopropyl-N,N-dimethylammoniumhetaine, ■-(3-sulfopropyl)-
Amphoteric monomers such as 2-vinylpyridinium betaine can also be used.

Next, as the crosslinking monomer added together with the hydrophilic monomer, ethylene glycol di(meth)acrylate,
Examples include polyfunctional heptamers such as diethylene glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, dipentaerythritol hexa(meth)acrylate, and divinyloxybutane, but are limited to the above heptamers. isn't it.

The above monomers can be used alone or in combination of two or more.

The amount of the hydrophilic monomers added depends on the solubility of these monomers in water, but generally the amount of crosslinkable monomers and non-crosslinkable monomers used in the initial suspension polymerization is Total amount of body 50
It is preferably about 5 to 500 parts by weight. If the amount is less than 5 parts by weight, the surface of the crosslinked polymer fine particles will not be made sufficiently hydrophilic, and if it is added more than 500 parts by weight, problems such as agglomeration of the polymerization system tend to occur, which is not preferable.

Further, the amount of the crosslinkable monomer added together with the hydrophilic monomer is preferably in the range of 0 to 50% by weight based on the total amount of the hydrophilic monomer and the crosslinkable monomer.

The fact that the crosslinked polymer fine particles obtained in the present invention has a core-shell structure is confirmed by the content of elements such as carbon, hydrogen, nitrogen, and oxygen obtained by ordinary elemental analysis methods and by XPS (
This can be easily confirmed by the difference in element content (increase in the content of elements derived from hydrophilic monomers such as oxygen and nitrogen) obtained by surface analysis using the X-ray photospectroscopy method.

When using the crosslinked polymer fine particles obtained by the method of the present invention as a spacer for a liquid crystal display, the above-mentioned hydrophilic monomer is preferably nonionic from the viewpoint of liquid crystal contamination, such as cationic or anionic monomer. When using quantifiers,
It is easy to contaminate the liquid crystal, and as a result, the transition temperature (solid phase → liquid crystal phase) is likely to decrease.

On the other hand, as the initiator used for polymerization, commonly used oil-soluble polymerization initiators can be used. For example, peroxide initiators such as hendyl peroxide, lauroyl peroxide, 0-chloro hendyl peroxide, 0-methoxy hendyl peroxide, 2,2 azobisisobutyronitrile, 2,2-azobis(2, Ab-based initiators such as 4-dimethylvaleronitrile) can be used. Although these initiators are essential in the first step of synthesizing crosslinked polymer fine particles, they do not need to be used when polymerization is carried out by adding a hydrophilic monomer.

The particle size of the crosslinked polymer fine particles obtained in the present invention can be appropriately designed depending on the intended use. Further, the obtained crosslinked polymer fine particles may be used as they are, or may be subjected to a classification operation to narrow the particle size distribution. The average particle diameter when used as a spacer for liquid crystal display varies depending on the purpose and type of liquid crystal display panel, but is usually 5 to 1.
It is about 〇-. When crosslinkable polymer fine particles with a wide particle size distribution are incorporated into a liquid crystal display panel, two
The standard deviation of the particle size distribution is preferably 20% or less of the particle size because it is not possible to maintain a constant interval between the sheets of transparent electrodes, which causes color unevenness during display.

The fine polymer particles after polymerization can be filtered to remove the aqueous layer, washed with water and/or a solvent, and then isolated as a powder by conventional means such as spray drying and vacuum drying.

[Examples] Hereinafter, the present invention will be explained in detail with reference to Examples, but the present invention is not limited to these Examples. In addition, in the examples, parts indicate parts by weight.

Example 1 Styrene 40 parts, divinylbenzene (M degree ss%) 60
3% aqueous solution of polyvinyl alcohol (Gl (-17, manufactured by Nippon Gosei Kagaku Kogyo ■; degree of saponification 86.5 to 89 mo1%) to a mixed solution of 1.0 parts of 2,2-azobisisobutyronitrile Add 800 parts, and add 800 parts under a nitrogen stream while stirring.
Polymerization was carried out at 0°C for 2 hours. The polymerization rate at this time was determined by gravimetric method and was 32.7%.

Add 1.2,2-azobisisobutyronitrile to this polymerization system.
0 parts, 1-10 parts of ethylene glycol dimethacrylate,
An emulsion obtained by sonicating a mixture of 40 parts of polyethylene glycol monomethacrylate (manufactured by NOF ■, Blenmar PE350), 1.5 parts of sodium lauryl sulfate, and 200 parts of ion-exchanged water was added, and the mixture was stirred and heated under a nitrogen stream. Polymerization was further carried out at 80"C for 12 hours. The obtained fine particles were washed with ion-exchanged water and a solvent, subjected to a classification operation, and further isolated and dried until the average particle size was 9.5 and the standard deviation was 1.
．． 8p crosslinked polymer fine particles were obtained.

This crosslinked polymer fine particle was used as a spacer for a liquid crystal display, and its adhesion to a liquid crystal panel was evaluated by the following method.

That is, 0.5 g of a liquid crystal display spacer that had been previously dried under reduced pressure (60″c/24 hours) was weighed out, and Freon S3-E (manufactured by Daikin Industries, Ltd.) / Isopropanol (manufactured by Wako Pure Chemical Industries, Ltd.) -3/ 2 (V/V) Disperse in 50m/ of mixed solvent.Into it, polyimide film-glass (manufactured by Nichikagaku@, Sunever 150 was coated on a 10×5 glass plate with a thickness of 100μ, and then sintered at 200°C for 30 minutes). was immersed for 10 seconds, and the dispersion medium was evaporated at room temperature for 5 minutes.After measuring the number of liquid crystal spacers within a predetermined field of view using an optical microscope, air was evaporated using an air gun (1 kg/cm2, diameter 11, distance 9 mm). was sprayed on the glass plate for 15 seconds, and the number of liquid crystal spacers within a predetermined field of view was remeasured.The remaining rate was calculated from the change in the number before and after spraying, and the adhesion was evaluated. showed a residual rate of

Examples 2-9. Comparative Examples 1 to 4 Suspension polymerization was carried out using various monomer compositions shown in Table 1.
Various hydrophilic monomers and crosslinkable monomers shown in Table 1 were added and copolymerized in the same manner as in Example 1 at the addition timing shown in . Furthermore, the adhesion of the liquid crystal display spacer made of each of the obtained crosslinked polymer fine particles was evaluated in the same manner as in Example 1, and the results are shown in Table 1.

For comparison, adhesion was also evaluated for crosslinked polymer fine particles to which no hydrophilic monomer was added. Table 1 shows the results.
Shown accordingly.

Note] Book I Rate 2 S: Styrene DVB Nidynylhenzen MM8: Methyl methacrylate EGDMA: Ethylene glycol dimethacrylate M8AA: Methylene bisacrylamide DED Niethylene glycol dimethacrylate HEMA: Hydroxyethyl methacrylate GMMA
: To glycerol monomethacrylate PGM: Polyethylene glycol polybrobylene glycol monomethacrylate BGMA Nibutanediol methacrylate PEG? I
A: Polyethylene glycol methacrylate (7 to 9 moles of EO added) EGDMA: Ethylene glycol dimethacrylate trimethylolpropane triacrylate TMPTA: DPEHA Nidipentaerythritol hexaacrylate DED Nidiethylene glycol dimethacrylate 3 AIBN: 2,2'-azobisiso Butyronitol IJle ν-65: 2,2'-Azobis(2,4-
dimethylvaleronitrile) BPO: benzoyl peroxide As is clear from the examples, the spacers for liquid crystal displays produced by the method of the present invention have a residual rate of 72.5 to 95% and have good adhesion, but are not hydrophilic. It was found that the liquid crystal display spacer of the comparative example in which no monomer was added showed almost no adhesion.

〔Effect of the invention〕

As is clear from the results of the above examples, when the crosslinked polymer fine particles obtained by the present invention are used as a spacer for a liquid crystal display, they have excellent adhesion to the electrode panel surface. Therefore,
It can prevent damage to the polyimide alignment film and is suitable as a spacer for liquid crystal displays.

Moreover, it can be used for various purposes as crosslinked polymer fine particles imparted with hydrophilicity.

Claims (1)

[Scope of Claims] 1. When carrying out aqueous suspension polymerization of a crosslinkable monomer and a non-crosslinkable monomer in the presence of a radical polymerization initiator, after the initiation of polymerization, when the polymerization rate is less than 90%, hydrophilic 1. A method for producing crosslinked polymer fine particles, which comprises performing polymerization by adding a polymeric monomer. 2. When carrying out aqueous suspension polymerization of crosslinking monomers and non-crosslinking monomers in the presence of a radical polymerization initiator, hydrophilic monomers and crosslinking are carried out at a point when the polymerization rate is less than 90% after the initiation of polymerization. 1. A method for producing crosslinked polymer fine particles, which comprises performing polymerization by adding a polymeric monomer. 3. When carrying out aqueous suspension polymerization of a crosslinkable monomer and a non-crosslinkable monomer in the presence of a radical polymerization initiator, a nonionic hydrophilic monomer is added when the polymerization rate is less than 90% after the start of polymerization. 1. A method for producing a spacer for a liquid crystal display, which comprises adding a polymer and polymerizing the spacer. 4. When carrying out aqueous suspension polymerization of a crosslinkable monomer and a non-crosslinkable monomer in the presence of a radical polymerization initiator, a nonionic hydrophilic monomer is added when the polymerization rate is less than 90% after the start of polymerization. 1. A method for producing a spacer for a liquid crystal display, which comprises performing polymerization by adding a polymer and a crosslinking monomer.