JP5452978B2 - Method for producing light diffusing organic fine particles and light diffusing film or molded body - Google Patents

Description

  The present invention relates to a method for producing light diffusing organic fine particles exhibiting excellent dispersibility in an organic solvent solution of a binder, and the light diffusing organic fine particles produced by the method are dispersed in a binder solution to form a film or molded article. The present invention relates to a coated light diffusion film or a light diffusion molded body.

  The light diffusing agent is applied in layers with a binder resin on a transparent synthetic resin film such as a polyester film or a polyimide film, or a transparent acrylic resin, MS resin, polycarbonate resin or cyclopolyolefin polymer. Combined with thermoplastic resin, fluorescent or white light lighting cover, backlight translucent signboard, display, lighting, interior translucent partition, liquid crystal display, light diffusion sheet and plate of LCD TV, projector, These are fine particles used to produce light diffusing films such as projection television screens and light diffusive moldings, and their demand has been increasing in recent years.

  Early light diffusing agents were inorganic materials such as titanium dioxide, barium sulfate, and powdered glass, but now organic light with uniform light diffusing performance, high total light transmittance, and excellent mechanical strength. Diffusing agents are known. Examples thereof include crosslinked polymethyl methacrylate, crosslinked polystyrene, crosslinked methyl methacrylate / styrene copolymer, and organic polymer fine particles such as silicon.

  Among them, in particular, a crosslinked polyvinyl polymer such as crosslinked polymethyl methacrylate, crosslinked polystyrene, and crosslinked methyl methacrylate / styrene copolymer is relatively inexpensive in addition to the above-mentioned performance, and has a degree of freedom in controlling the particle diameter and shape. Since it is expensive, it is now one of the materials that are frequently used as light diffusing organic fine particles, and various production methods have been studied so far.

  For example, Patent Document 1 describes the use of a water-soluble polymer or a salt that is insoluble in water as a dispersion stabilizer in suspension polymerization of a vinyl monomer.

However, since the water-soluble polymer is graft-polymerized on the target particle surface, it is difficult to remove the water-soluble polymer after the polymerization. In addition, when using a water-insoluble salt, the water-insoluble salt can be decomposed by adding an acid, but actually it is difficult to completely remove the salt from the target product.
Thus, if water-soluble polymer or inorganic salt remains on the surface of the light diffusing particles, the dispersion of the fine particles into the binder solution is inhibited, and the fine particles are aggregated, and as a result, applied to a film or sheet. When it does, it becomes a cause which a defect produces in the light dispersibility of a film or a sheet.

Japanese Patent Laid-Open No. 2002-207107

  An object of the present invention is to provide organic fine particles that can be easily and uniformly dispersed in an organic solvent solution of a binder and can impart excellent light diffusion performance to a film or a molded body.

As a result of diligent investigations to solve the above problems, the present inventors have made it easy to use an intermediate saponified polyvinyl alcohol having a specific saponification degree, that is, poval, as a dispersion stabilizer for suspension polymerization in an organic solvent solution of a binder. Thus, light diffusible organic fine particles, that is, light diffusible crosslinked polyvinyl resin fine particles capable of producing a film or a molded article having excellent light diffusing performance, can be obtained.
That is, the present invention
(1) (meth) acrylic acid or (meth) acrylic as a monofunctional vinylic monomer using poval having a saponification degree of 90 to 97% as a dispersant in the presence of a polyfunctional vinyl monomer as a crosslinking agent A process for producing light diffusing organic fine particles by suspension polymerization of an acid ester ,
(2) The method for producing light diffusing organic fine particles according to (1), wherein 1 to 15% by weight of poval having a saponification degree of 90 to 97% is used relative to the total amount of the crosslinking agent and the monofunctional vinyl monomer
(3) In suspension polymerization, a plasticizer, a polymerization stabilizer, a colorant, an antioxidant, an optical brightener, a magnetic powder, an ultraviolet absorber, an antistatic agent, or a flame retardant additive is blended (1) or (2) A process for producing the light diffusing organic fine particles as described above,
(4) A light diffusing film or a light diffusing molded article obtained by dispersing the light diffusing organic fine particles produced by the production method according to any one of (1) to (3) in a binder solution and coating the film or the molded article. ,
It is.

The poval having a saponification degree of 90 to 97% used in the present invention is generally called an intermediate saponification poval, but preferably has a saponification degree of 90 to 96%, more preferably 91 to 94%.
In POVAL with a saponification degree of less than 91%, when the monofunctional vinyl monomer and the polyfunctional vinyl monomer as a cross-linking agent are dispersed in water, the monomer droplets maintain good stability. During the polymerization reaction, the poval is graft-polymerized on the surface of the generated organic particles, and it becomes difficult to remove the poval from the particle surface after the polymerization reaction. As a result, the dispersibility in the binder organic solvent solution decreases, and problems such as aggregation of fine particles occur when the dispersion is applied to a film or the like. If the degree of saponification of Poval exceeds 96%, suspension polymerization itself becomes difficult because the droplets of the vinyl monomer are unstable when dispersed in water.

The intermediate saponified poval used can be used in an amount of 1 to 15% by weight, preferably 2 to 10% by weight, based on the total amount of the crosslinking agent and the monofunctional vinyl monomer. In order to improve the dispersion stability, a surfactant can be used in combination, and the amount used is usually 0.1 to 5% by weight, preferably based on the total amount of the crosslinking agent and the monofunctional vinyl monomer. Is 0.1 to 2% by weight.
Surfactants that can be used include anionic surfactants such as polyoxystyrenated phenyl ether ammonium sulfate, cationic surfactants such as lauryltrimethylammonium chloride, and nonionic surfactants such as polyoxyethylene alkyl ether phosphoric acid. Agents, amphoteric surfactants such as lauryl betaine, and reactive surfactants such as polyoxyethylene nonylpropenyl phenyl ether ammonium sulfate, among which anionic surfactants and nonionic surfactants are preferred.

As the monofunctional vinyl monomer for producing the present polyvinyl resin fine particles, polymerizable vinyl monomers such as (meth) acrylic acid ester, (meth) acrylic acid, styrene, vinyl acetate, acrylonitrile and the like can be used.
The crosslinking agent is used to improve the solvent resistance of the organic fine particles, and examples thereof include polyfunctional vinyl monomers such as ethylene glycol dimethacrylate, trimethylolpropane trimethacrylate, and divinylbenzene. Is usually 0.5 to 40% by weight, preferably 5 to 30% by weight, based on the monofunctional vinylic monomer.

  Further, in the polymerization, an appropriate amount of a coloring agent such as a pigment or a dye, or other additives may be added or added to the polymerizable monomer or the aqueous phase as necessary. Examples of the pigment include inorganic pigments such as lead white, red lead, yellow lead, carbon black, ultramarine, zinc oxide, cobalt oxide, titanium dioxide, iron oxide, silica, titanium yellow, and titanium black, isoindolinone, quinacridone, Organic pigments such as dioxane violet, phthalocyanine blue, perinone pigment, perylene pigment, insoluble azo pigment, soluble azo pigment, and dye lake are used. Examples of the dye include nitroso dye, nitro dye, azo dye, stilbene azo dye, diphenylmethane dye, triphenylmethane dye, xanthene dye, acridine dye, quinoline dye, methine dye, polymethine dye, thiazole dye, indamine dye, india Phenol dyes, azine dyes, oxazine dyes, thiazine dyes, sulfur dyes and the like are used. Examples of other additives include plasticizers, polymerization stabilizers, antioxidants, fluorescent brighteners, magnetic powders, ultraviolet absorbers, antistatic agents, flame retardants, and the like.

  In this polymerization reaction, oil-soluble polymerization initiators such as peroxide initiators such as benzoyl peroxide and lauroyl peroxide, and azobis initiators such as azobisbutyronitrile can be used as the polymerization initiator. . The amount used is 0.1 to 2% by weight based on the total amount of the crosslinking agent and the monofunctional vinyl monomer.

  After dissolving the polymerization initiator in the cross-linking agent and the monofunctional vinyl monomer, this is added to an intermediate saponified poval or an aqueous solution containing an intermediate saponified poval and a surfactant, and adjusted to the desired droplet size by adjusting the stirring conditions. adjust. This mixed solution is subjected to suspension polymerization under a nitrogen atmosphere, stirring and heating according to a conventional method to obtain desired light diffusing agent particles. The average particle diameter of the fine particles is usually 2 to 100 μm, preferably 2 to 50 μm, more preferably 2 to 30 μm. The shape of the fine particles is not particularly limited, but a spherical shape, a spheroid and the like are preferable.

  The polyvinyl polymer fine particles obtained by the polymerization are taken out from the polymerization reaction solution as a powder and used. That is, after aggregating by salting out or freezing, a method by centrifugation or a method by spray drying can be employed.

After dispersing the fine particles of the present invention in an organic solvent containing a binder, a light diffusing film or a molded body can be produced by uniformly applying and fixing on a substrate such as a film or a molded body.
The material of the film or molded body substrate to which this dispersion is applied and fixed is preferably optically transparent and excellent in heat resistance and light resistance. For example, polyethylene terephthalate resin, polycarbonate resin, polyimide resin, polyvinyl chloride Examples thereof include resins, polyester resins, styrene-acrylonitrile copolymer resins, cyclopolyolefin polymer resins, and polyethylene terephthalate resins are preferably used.
The thickness of these substrate films is usually selected from 10 to 1000 μm depending on the size of the display, and the film in the present invention includes the concept of a sheet. A molded object is a normal plate-shaped molded object obtained by injection molding of raw material resin, extrusion molding, compression molding, etc., for example.
The thickness of the bead layer provided on the plate of these films and molded bodies is usually about 10 to 150 μm, preferably about 15 to 50 μm.
Moreover, as said binder, transparent resin, for example, an acrylic resin, a polyester resin, etc. are used, and you may fix with a urethane type crosslinking agent etc. at the time of drying. Examples of the organic solvent used as the solvent for the binder include butyl acetate, methyl ethyl ketone, and toluene. The ratio of the organic fine particles to the transparent resin is not particularly limited, but is 30 to 500 parts by weight, preferably 50 to 300 parts by weight with respect to 100 parts by weight of the transparent resin as a binder in consideration of light diffusion performance. .
Various methods such as a roll coating method, a dipping method, a spray coating method, a spin coating method, a laminating method, and a pouring method are performed as a method for applying organic fine particles to the substrate surface, but is not particularly limited.

  The organic fine particles produced by the production method of the present invention are easily dispersed in a binder organic solvent solution by using poval having a saponification degree of 90 to 97% as a dispersing agent, and excellent light can be obtained by applying the dispersion. Films and molded articles having diffusion performance can be obtained.

  The present invention will be specifically described below with reference to examples, comparative examples, and test examples. In addition, unless otherwise indicated, a part is a weight part.

In a dispersion vessel, 300 parts of deionized water and 5 parts of intermediate saponified poval (AL-06R manufactured by Nihon Gosei Co., Ltd.) having a saponification degree of 91 to 94% were placed and completely dissolved. Separately, a monomer solution was prepared from 80 parts of methyl methacrylate, 20 parts of ethylene glycol dimethacrylate and 0.5 part of benzoyl peroxide as a reaction initiator, and added to the dispersion container. The obtained mixed liquid was subjected to a dispersion treatment using a homomixer to obtain a dispersion liquid having an adjusted droplet diameter. This dispersion was poured into a polymerization reactor equipped with a stirrer, thermometer, reflux condenser and nitrogen inlet, stirred at 70 ° C. under a nitrogen stream, and then subjected to a polymerization reaction at 80 to 90 ° C. for 3 hours. .
The obtained dispersion of polymer particles was filtered, washed, and dried to obtain spherical organic fine particles having an average particle diameter of 12.4 μm.

In a dispersion container, put 300 parts of deionized water, 5 parts of intermediate saponified poval (AL-06R manufactured by Nihon Gosei Co., Ltd.) with a degree of saponification of 91-94%, and 1 part of polyoxystyrenated phenyl ether ammonium sulfate. I let you. Separately from this, a monomer solution was prepared from 80 parts of methyl methacrylate, 20 parts of ethylene glycol dimethacrylate and 0.5 part of benzoyl peroxide, and added to the dispersion container. The obtained mixed liquid was subjected to a dispersion treatment using a homomixer to obtain a dispersion liquid having an adjusted droplet diameter. This dispersion was poured into a polymerization reactor equipped with a stirrer, thermometer, reflux condenser and nitrogen inlet, stirred at 70 ° C. under a nitrogen stream, and then subjected to a polymerization reaction at 80 to 90 ° C. for 3 hours. .
The obtained dispersion of polymer particles was filtered, washed, and dried to obtain spherical organic fine particles having an average particle diameter of 12.0 μm.

In a dispersion vessel, put 300 parts of deionized water, 5 parts of intermediate saponification poval with a saponification degree of 95-97% (P-610, manufactured by Nihon Gosei Co., Ltd.) and 2 parts of polyoxystyrenated phenyl ether ammonium sulfate. I let you. Separately from this, a monomer solution was prepared from 80 parts of methyl methacrylate, 20 parts of ethylene glycol dimethacrylate and 0.5 part of benzoyl peroxide, and added to the dispersion container. The obtained mixed liquid was subjected to a dispersion treatment using a homomixer to obtain a dispersion liquid having an adjusted droplet diameter. This dispersion was poured into a polymerization reactor equipped with a stirrer, thermometer, reflux condenser and nitrogen inlet, stirred at 70 ° C. under a nitrogen stream, and then subjected to a polymerization reaction at 80 to 90 ° C. for 3 hours. .
Although the obtained polymer particles were easily aggregated, spherical organic fine particles having an average particle diameter of 12.6 μm were obtained by filtering, washing and drying the dispersion.

In a dispersion vessel, put 300 parts of deionized water, 7 parts of intermediate saponified poval (AL-06R manufactured by Nihon Gosei Co., Ltd.) with a saponification degree of 91-94%, and 1 part of polyoxystyrenated phenyl ether ammonium sulfate. I let you. Separately, a monomer solution was prepared from 60 parts of butyl methacrylate, 20 parts of butyl acrylate, 20 parts of ethylene glycol dimethacrylate and 0.5 part of azobisisobutyronitrile, and added to the dispersion container. . The obtained mixed liquid was subjected to a dispersion treatment using a homomixer to obtain a dispersion liquid having an adjusted droplet diameter. This dispersion was poured into a polymerization reactor equipped with a stirrer, thermometer, reflux condenser and nitrogen inlet, stirred at 70 ° C. under a nitrogen stream, and then subjected to a polymerization reaction at 80 to 90 ° C. for 3 hours. .
The obtained dispersion of polymer particles was filtered, washed, and dried to obtain spherical organic fine particles having an average particle size of 12.7 μm.
[Comparative Example 1]

In a dispersion vessel, 300 parts of deionized water and 5 parts of partially saponified poval (B-05 manufactured by Denka Co., Ltd.) having a saponification degree of 86.5 to 89.5% were completely dissolved. Separately from this, a monomer solution was prepared from 80 parts of methyl methacrylate, 20 parts of ethylene glycol dimethacrylate and 0.5 part of benzoyl peroxide, and added to the dispersion container. The obtained mixed liquid was subjected to a dispersion treatment using a homomixer to obtain a dispersion liquid having an adjusted droplet diameter. This dispersion was poured into a polymerization reactor equipped with a stirrer, thermometer, reflux condenser and nitrogen inlet, stirred at 70 ° C. under a nitrogen stream, and then subjected to a polymerization reaction at 80 to 90 ° C. for 3 hours.
The obtained dispersion of polymer particles was filtered, washed and dried to obtain spherical organic fine particles having an average particle size of 12.2 μm.
[Comparative Example 2]

In a dispersion vessel, put 300 parts of deionized water, 5 parts of partially saponified poval (B-05 manufactured by Denka Co., Ltd.) having a saponification degree of 86.5-89.5%, and 1 part of polyoxystyrenated phenyl ether ammonium sulfate. It was completely dissolved. Separately from this, a monomer solution was prepared from 80 parts of methyl methacrylate, 20 parts of ethylene glycol dimethacrylate and 0.5 part of benzoyl peroxide, and added to the dispersion container. The obtained mixed liquid was subjected to a dispersion treatment using a homomixer to obtain a dispersion liquid having an adjusted droplet diameter. This dispersion was poured into a polymerization reactor equipped with a stirrer, thermometer, reflux condenser and nitrogen inlet, stirred at 70 ° C. under a nitrogen stream, and then subjected to a polymerization reaction at 80 to 90 ° C. for 3 hours.
The obtained dispersion of polymer particles was filtered, washed, and dried to obtain spherical organic fine particles having an average particle diameter of 12.0 μm.
[Comparative Example 3]

In a dispersion container, 300 parts of deionized water, 10 parts of tricalcium phosphate as a dispersion stabilizer, and 0.2 part of polyoxyethylene alkyl ether phosphoric acid were added. Separately from this, a monomer solution was prepared from 80 parts of methyl methacrylate, 20 parts of ethylene glycol dimethacrylate and 0.5 part of benzoyl peroxide, and added to the dispersion container. The obtained mixed liquid was subjected to a dispersion treatment using a homomixer to obtain a dispersion liquid having an adjusted droplet diameter. This dispersion was poured into a polymerization reactor equipped with a stirrer, thermometer, reflux condenser and nitrogen inlet, stirred at 70 ° C. under a nitrogen stream, and then subjected to a polymerization reaction at 80 to 90 ° C. for 3 hours.
The obtained dispersion of polymer particles was filtered, washed and dried to obtain spherical organic fine particles having an average particle size of 11.9 μm.
[Comparative Example 4]

In a dispersion vessel, put 300 parts of deionized water, 5 parts of completely saponified poval (K-05 manufactured by Denka Co., Ltd.) having a degree of saponification of 97.5-98.5%, and 1 part of polyoxystyrenated phenyl ether ammonium sulfate. It was completely dissolved. Separately from this, a monomer solution was prepared from 80 parts of methyl methacrylate, 20 parts of ethylene glycol dimethacrylate and 0.5 part of benzoyl peroxide, and added to the dispersion container. The obtained mixed liquid was subjected to a dispersion treatment using a homomixer to obtain a dispersion liquid having an adjusted droplet diameter. This dispersion was poured into a polymerization reactor equipped with a stirrer, thermometer, reflux condenser and nitrogen inlet, stirred at 70 ° C. under a nitrogen stream, and then subjected to a polymerization reaction at 80 to 90 ° C. for 3 hours.
During the reaction, the dispersed monomer aggregated, and polymer particles could not be obtained.
[Test Example 1]

Preparation of coating material A for light diffusion layer Methyl ethyl ketone 100 parts Toluene 100 parts Fine particles of Example 1 100 parts Acrylic resin solution “Dianar LR-1532” 100 parts [Mitsubishi Rayon Co., Ltd.]
The above components were stirred and mixed at room temperature for 16 hours with a three-one motor, then 10 parts of polyisocyanate “Coronate HL” (manufactured by Nippon Polyurethane Industry) was added, and the mixture was stirred and mixed at room temperature for 20 minutes, thereby coating light diffusion layer A Got.

As a substrate, a polyethylene terephthalate (PET) film having a thickness of 100 μm is used, and the light diffusion layer coating material A is applied to one surface of the film so that the dry film thickness is about 20 μm, and dried by hot air to light. A dry coating film of the diffusion layer was obtained.
Similarly, using the fine particles shown in Examples 2 to 3 and Comparative Examples 1 to 3, a coating operation was performed in the same manner as in the preparation of the light diffusing layer coating material A to prepare a light diffusing film.

Evaluation of optical characteristics Using haze guard II (manufactured by Toyo Seiki Co., Ltd.), the total light transmittance and haze of the light diffusion film were measured. The evaluation results are shown in Table 1.
The luminance was measured using SL-110 manufactured by Minolta, and each sample was expressed by relative evaluation with Comparative Example 1 being 100%.

Evaluation of surface state The surface state of the prepared light diffusion film was observed visually and with a microscope (× 100), the degree of aggregation of the light diffusion layer was evaluated, and the evaluation results are shown in Table 1.
The evaluation was performed according to the following criteria.
○: Aggregation was not confirmed in the light diffusion layer, and the particles were uniformly applied.
Δ: Aggregation is not confirmed in the light diffusion layer, but there are places where particles are not present in the layers.
X: Aggregation is confirmed in the light diffusion layer.

  Since the light diffusing resin composition of the present invention has excellent light diffusibility and total light transmittance, in particular, a light diffusing sheet of a liquid crystal television, a fluorescent or white light illumination cover, a backlight type translucent signboard, It can be used in various fields such as displays, electrical decorations, interior translucent partitions, liquid crystal displays, projectors and projection TV screens.

Claims (4)

(Meth) acrylic acid or (meth) acrylic acid ester as monofunctional vinylic monomer using poval having a saponification degree of 90 to 97% as a dispersing agent in the presence of a polyfunctional vinylic monomer as a crosslinking agent For producing light diffusing organic fine particles by suspension polymerization. The method for producing light diffusing organic fine particles according to claim 1, wherein 1 to 15% by weight of poval having a saponification degree of 90 to 97% is used based on the total amount of the crosslinking agent and the monofunctional vinyl monomer. The plasticizer, polymerization stabilizer, colorant, antioxidant, fluorescent brightening agent, magnetic powder, ultraviolet absorber, antistatic agent or flame retardant additive is blended in suspension polymerization. Method for producing light diffusing organic fine particles. The light-diffusion film or light-diffusion molded object which disperse | distributed the light diffusable organic fine particle manufactured by the manufacturing method in any one of Claims 1-3 in the binder solution, and apply | coated to the film or the molded object.