JP2007204695A - Light diffusing agent and light diffusing resin composition using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light diffusing member having a high optical transmission and a high light diffusing performance by solving problems of the light diffusing materials originated from conventional light diffusing resin compositions that in raising the light diffusing properties a large amount of the light diffusing resin composition have to be added but the large amount addition of the light diffusing resin composition causes reduction of the light transmission and luminescence face luminosity. <P>SOLUTION: The light diffusing agent is produced in the following steps, a first step forming a dispersion of fine particles of cross linked vinyl copolymers obtained by radically polymerizing (a) 50-99.8 wt.%. of isobutyl acrylate, (b) 0.1-20 wt.%. of a polyfunctional monomer having two or more vinyl groups in the molecule and (c) 0.1-49.9 wt.%. of the other polymerizable vinyl monomer, and a second step (d) adding a copolymerizable vinyl monomer which forms a polymer having ≥50°C of glass transition temperature, to the reaction liquid of the first step to absorb or adhere the monomer onto the particles of the first step and then carry out the polymerization, wherein the fine particles have 0.5-30 μm of average particle diameter. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a light diffusing agent exhibiting excellent light diffusibility without lowering light transmittance and light emitting surface luminance, and a light diffusing resin composition using the same.

  The light diffusing agent is applied in layers with a binder resin on a transparent polyester film or polyimide film, or is blended with a thermoplastic resin such as a transparent acrylic resin, MS resin, polycarbonate resin or cyclopolyolefin polymer. The This light diffusing agent can be used for fluorescent or white light lighting covers, backlit translucent signs, displays, lighting, interior translucent partitions, as well as liquid crystal displays, light diffusion sheets and plates for liquid crystal televisions, projectors and projection televisions. It is used in many fields such as screens.

  The initial light diffusing agent used was inorganic titanium dioxide, barium sulfate, glass, etc., but now it has uniform light diffusing performance, good total light transmittance, and excellent mechanical strength. Fine particles are known. Examples thereof include crosslinked polymethyl methacrylate, crosslinked polystyrene, crosslinked methyl methacrylate / styrene copolymer, and organic polymer powders such as silicon.

  Until now, in order to obtain a light diffusing agent of organic polymer powder having excellent light diffusivity and high total light transmittance, the average particle diameter and distribution of organic polymer particles or the refractive index with respect to the matrix resin are set. Various ideas have been devised, such as devising, further changing the shape of the particles from a spherical shape to an irregular shape, or particles having a structural refractive index difference inside the particles. For example, as a method for providing a condition for the refractive index difference between the transparent resin and the light diffusing agent, 0.02 ≦ | Ns−Np | ≦ 0.1 and 10 ≦ d in a transparent plastic (refractive index Ns). A light diffusing plastic (Patent Document 1) in which transparent fine particles of ≦ 50 μ are dispersed at a concentration of a maximum bending angle of 2 to 10 °, and transparent fine particles having a mixing rate of particles of 3 μm or less being 5% or less is the maximum. A light diffusing plastic (Patent Document 2) dispersed at a concentration at which the bending angle is 4 to 10 ° is disclosed. However, a light diffusing material molded using the light diffusing resin composition described in the above publication requires a large amount of the light diffusing resin composition to increase its light diffusibility. When a large amount of is added, there arises a problem that the light transmittance and the light emitting surface brightness are lowered. Therefore, the light diffusing resin composition described in the above literature cannot provide a light diffusing member having high light permeability and high light diffusibility.

Furthermore, a method of obtaining light diffusing organic fine particles having a low refractive index by copolymerizing a fluorine-containing alkyl (meth) acrylate with a vinyl monomer is known (Patent Document 3). However, fluorine-containing alkyl (meth) acrylates are expensive, and there is a strong demand for the development of alternative materials for dehalogenation from the environmental aspect.
JP-A-60-139758 JP-A-60-184559 JP 2000-169658 A

  An object of the present invention is to find a light diffusing agent that has light diffusibility and light transmittance comparable to those of a fluorine-containing alkyl (meth) acrylate copolymer and can be provided at low cost.

  As a result of various studies to solve the above problems, the present inventors have used isobutyl acrylate (hereinafter referred to as i-butyl acrylate), which can be obtained at a low cost, as a monomer and a polymer having two or more vinyl groups in the molecule. A functional monomer and, if necessary, other copolymerizable vinyl monomers are radically polymerized to form a polymer having a glass point transfer of 50 ° C. or higher in the resulting crosslinked vinyl copolymer fine particle suspension. Light diffusion performance is such that the fine particles produced by the reaction of polymerizing by adsorbing or adhering the copolymerizable vinyl monomer can replace the fluorine-containing alkyl (meth) acrylate copolymer, The inventors have found that the light diffusing agent has high transmittance and excellent light emitting surface luminance, and has completed the present invention.

That is, the present invention
(1)
(A) 50-99.8% by weight of isobutyl acrylate, (b) 0.1-20% by weight of a polyfunctional monomer having two or more vinyl groups in the molecule, and (c) other copolymerizable vinyls First-stage reaction in which 0 to 49.9 wt% of monomers are radically polymerized to form a crosslinked vinyl copolymer fine particle suspension, and (d) copolymerization to form a polymer having a glass point transfer of 50 ° C. or higher. A light diffusing agent comprising fine particles having an average particle size of 0.5 to 30 μm produced by a second-stage reaction in which a polymerizable vinyl monomer is added to the first-stage reaction liquid and absorbed or adhered to the first-stage particles to perform polymerization;
(2)
The light diffusing agent according to (1), wherein the weight ratio of the monomer used for the first stage reaction and the monomer used for the second stage reaction is 95/5 to 30/70,
(3)
In the polymerization, at least one additive selected from the group consisting of pigments, dyes, plasticizers, polymerization stabilizers, antioxidants, fluorescent brighteners, magnetic powders, ultraviolet absorbers, antistatic agents and flame retardants is blended. The light diffusing agent according to any one of (1) and (2),
(4)
(1)-(3) The light-diffusion film or light-diffusion sheet which apply | coated the light-diffusion agent in any one of description to a film or sheet-like resin with a binder, and (5)
(1) to (3) a light diffusing resin molded article obtained by kneading the light diffusing agent according to any one of (3) into a matrix resin;
It is.

  The light diffusing agent (beads) of the present invention comprises (a) 50 to 99.8% by weight of isobutyl acrylate, and (b) 0.1 to 20% by weight of a polyfunctional monomer having two or more vinyl groups in the molecule. % And (c) 0 to 49.9% by weight of other copolymerizable vinyl monomers by suspension polymerization to form a crosslinked vinyl copolymer fine particle suspension, followed by (d) 50 ° C. Average particle diameter produced by the second-stage reaction in which the copolymerizable vinyl monomer that forms the polymer having the above glass point transfer is added to the first-stage reaction liquid and absorbed or adhered to the first-stage particles for polymerization. It is a light diffusing agent that is a multiphase structured fine particle of 0.5 to 30 μm.

In this first stage reaction, a polyfunctional monomer (b) having two or more vinyl groups in the molecule is reacted with isobutyl acrylate (a) and, if necessary, another copolymerizable vinyl monomer (c). This makes it possible to impart solvent resistance, heat resistance, and the like to the resin.
Examples of the polyfunctional monomer (b) having two or more vinyl groups in the molecule include aromatic divinyl monomers such as divinylbenzene, ethylene glycol di (meth) acrylate, butylene glycol di (meth) acrylate, hexanediol di ( Alkane polyol polyacrylate or alkane polyol polymethacrylate such as meth) acrylate, oligoethylene glycol di (meth) acrylate, trimethylolpropane di (meth) acrylate, trimethylolpropane tri (meth) acrylate, etc., and different reactive vinyl groups Examples of the monomer having allyl acrylate, allyl methacrylate, diallyl malate, diallyl fumarate, diallyl itaconate, urethane di (meth) acrylate, epoxy It can also be mentioned di (meth) acrylate, in particular ethylene glycol dimethacrylate, butylene glycol diacrylate, allyl methacrylate is preferably used.
Such a polyfunctional monomer (b) having two or more vinyl groups in the molecule is usually 0.1 to 20% by weight, preferably 0.1 to 10% by weight in the monomer used in the first stage reaction. % Range.

In the present invention, other vinyl monomers (c) copolymerized with an i-butyl acrylate monomer as required include (meth) acrylic acid ester, (meth) acrylic acid, styrene, vinyl acetate, acrylonitrile, etc. Mention may be made of monovinyl monomers other than i-butyl acrylate monomers.
Examples of (meth) acrylic acid esters include ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, cyclohexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isononyl (meth) acrylate, lauroyl ( Examples thereof include alkyl (meth) acrylates having 2 to 20 carbon atoms in the alkyl group such as (meth) acrylate and stearyl (meth) acrylate. Among these, those having 2 to 10 carbon atoms in the alkyl group such as ethyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate and isononyl (meth) acrylate are preferable, and ethyl acrylate and butyl acrylate are particularly preferable. preferable.
Furthermore, for example, aromatic vinyl such as styrene, vinyl toluene, and α-methylstyrene, vinyl cyanide such as aromatic vinylidene, acrylonitrile, and methacrylonitrile, vinylidene cyanide, urethane acrylate, urethane methacrylate, and the like can be given.

These copolymerizable monomers (c) are generally used in the range of 0 to 49.9% by weight, preferably 0 to 29.9% by weight, based on all monomers in the first stage reaction.
In this first-stage reaction, a polymerizable monomer, a dispersion stabilizer, an oil-soluble radical polymerization initiator and ion-exchanged water are charged into a polymerization vessel, and radical polymerization, preferably suspension polymerization, is performed with stirring.
Examples of the dispersion stabilizer include gelatin, methyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, carboxymethyl cellulose, polyethylene glycol, polyoxyethylene-polyoxypropylene block copolymer, polyacrylamide, polyacrylic acid, polyacrylate, and sodium alginate. Examples thereof include water-soluble polymers such as partially saponified polyvinyl alcohol, inorganic substances such as tricalcium phosphate, titanium oxide, calcium carbonate, and silicon dioxide. Among these dispersion stabilizers, polyvinyl alcohol partially saponified product, hydroxypropyl cellulose, and tricalcium phosphate are particularly preferably used. These dispersion stabilizers can be used alone or in combination of two or more. The amount of the dispersion stabilizer used is, for example, about 0.1 to 60 parts by weight, preferably about 0.2 to 30 parts by weight with respect to 100 parts by weight of the polymerizable monomer for the first stage reaction.

The oil-soluble radical polymerization initiator is preferably dissolved in advance in the polymerizable monomer. Examples of the oil-soluble radical initiator include organic peroxides such as benzoyl peroxide, o-methoxybenzoyl peroxide, o-chlorobenzoyl peroxide, lauroyl peroxide, cumene hydroperoxide, and 2,2′-azobis. Examples thereof include azo compounds such as isobutyronitrile and 2,2′-azobis-2,4-dimethylvaleronitrile. Of these radical polymerization initiators, benzoyl peroxide, lauroyl peroxide, 2,2′-azobisisobutyronitrile and the like are preferably used. These radical polymerization initiators can be used alone or in combination of two or more. The amount of the radical polymerization initiator used is, for example, about 0.1 to 5 parts by weight, preferably about 0.1 to 2 parts by weight, based on 100 parts by weight of the polymerizable monomer for the first stage reaction.
Further, if necessary, a surfactant such as sodium dodecylbenzenesulfonate, sodium dialkylsulfosuccinate, sodium lauryl sulfate, or a surfactant such as polyethylene glycol nonylphenyl ether is used to stabilize the dispersion of the monomer droplets. A nonionic surfactant or the like may be added. These surfactants can be used alone or in combination of two or more.

  The amount of the surfactant used is, for example, about 0.05 to 2 parts by weight with respect to 100 parts by weight of the polymerizable monomer for the first stage reaction. If necessary, an aqueous phase polymerization inhibitor such as sodium nitrite may be added.

  In the first stage reaction, in the step of producing polymer particles by suspension polymerization, a mixture of a polymerizable monomer, a dispersion stabilizer, an oil-soluble radical polymerization initiator and ion-exchanged water prior to the start of the reaction. The monomer droplets are preferably adjusted to a desired size by a shearing force by stirring. In this case, in order to form fine monomer droplets of 30 μm or less, it is preferable to use various dispersing means such as a homomixer, a homodisper, a homogenizer, and a line mixer. The size of the monomer droplet can be controlled by adjusting the shearing force according to the rotational speed of the dispersing means. The polymerizable monomer dispersion thus prepared is heated to the 10-hour half-life temperature of a radical polymerization initiator and a polymerization reaction is carried out to obtain a polymer particle suspension for the first stage reaction. For example, when lauroyl peroxide is used, the temperature is raised to 55 ° C. or higher, and when 2,2′-azobisisobutyronitrile is used, the temperature is raised to 65 ° C. or higher to carry out radical polymerization, whereby polymer particle suspension in the first stage reaction is performed. A turbid liquid is obtained.

  Next, in the second-stage reaction, a monomer that forms a polymer having a glass transition point of 50 ° C. or higher is added to the first-stage reaction in the presence of the polymer particle suspension obtained in the first-stage reaction described above. A glassy polymer having a glass transition temperature of 50 ° C. or higher is formed by a second-stage reaction in which the fine particles obtained in the above are absorbed or adhered to the surface and polymerized. When this glass transition temperature is lower than 50 ° C., when particles are aggregated, fused, coalesced, etc. in the synthesis stage during the production by suspension polymerization, or heated during dehydration or drying after the synthesis is completed. As a result, the polymer particles are aggregated and fused, so that it may not be possible to take out the product while maintaining the shape as the particles. Therefore, the glass transition temperature of the glassy polymer is usually 50 ° C. or higher, preferably 50 to 140 ° C., more preferably 60 to 130 ° C.

A polymerizable monomer (d) that forms a polymer having a glass transition point of 50 ° C. or higher is preferably at least one monomer selected from alkyl (meth) acrylates and aromatic vinyl monomers.
As the alkyl (meth) acrylate, those mentioned above as (c) are used, and examples thereof include alkyl (meth) acrylates having 1 to 4 carbon atoms such as methyl acrylate, methyl methacrylate, ethyl acrylate and ethyl methacrylate. . Examples of the aromatic vinyl monomer include styrene, vinyl toluene, α-methyl styrene and the like.
By using a polyfunctional monomer having two or more vinyl groups in the molecule in the second-stage reaction, the dispersibility of the polymer particles may be further improved. As the polyfunctional monomer having two or more vinyl groups in the molecule, those mentioned in the above-mentioned (b) can be used, and usually 0 to 50% by weight, preferably 0, in the polymerizable monomer of the second stage reaction. It can be used in the range of ˜40% by weight.

A polymerization initiator can be further added in the second-stage reaction, but in the case of an oil-soluble radical polymerization initiator, it is dissolved in the polymerizable monomer of the second-stage reaction and added, and a water-soluble radical polymerization initiator is used. In this case, it can be added separately in the form of an aqueous solution.
As the polymerization initiator usable in the second stage reaction, the oil-soluble radical polymerization initiator described above can be used, and as the water-soluble radical polymerization initiator, persulfate-based polymerization such as sodium persulfate and potassium persulfate is used. Initiators, azo polymerization initiators such as 2,2′-azobis (2-amidinopropane) dihydrochloride, 2,2′-azobis [2-methyl-N- (2-hydroxyethyl) -propionamide], etc. Can be used. These radical polymerization initiators can be used alone or in combination of two or more.
The amount of the radical polymerization initiator used is, for example, about 0.1 to 10 parts by weight, preferably about 0.05 to 2 parts by weight, based on 100 parts by weight of the polymerizable monomer for the second-stage reaction. If the amount added is too large, it may be difficult to generate new particles or irregularly shaped particles and take a multiphase structure.
The weight ratio of the monomer used for the first stage reaction to the monomer used for the second stage reaction is 95/5 to 30/70, preferably 90/10 to 40/60, more preferably 80/20 to 55 /. 45.

Further, in the polymerization, in the polymerizable monomer or the aqueous phase in the first stage or second stage reaction, a pigment, a dye, a plasticizer, a polymerization stabilizer, an antioxidant, a fluorescent whitening, if necessary. The additives, magnetic powders, ultraviolet absorbers, antistatic agents and flame retardants can be blended or added with other additives.
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. Other additives include plasticizers, polymerization stabilizers, antioxidants, fluorescent brighteners, magnetic powders, UV absorbers, antistatic agents, flame retardants, etc. The method of use and the like may follow a conventionally known method.

  In addition, these colorants and other additives may be surface-treated by various methods for the purpose of improving dispersibility in the polymerizable monomer. Surface treatment methods include treatment with long-chain hydrocarbons such as stearic acid and oleic acid, treatment with polymerizable monomers having polar groups such as acrylic acid and methacrylic acid, and various methods such as trimethylolpropane. A method of treating with a monohydric alcohol, a method of treating with an amine such as triethanolamine, a method of treating with various coupling agents, or an aziridine group capable of reacting with a colorant or other additive with a functional group on these surfaces , A polymer having a reactive group such as an oxazoline group, an N-hydroxyalkylamide group, an epoxy group, a thioepoxy group, an isocyanate group, a vinyl group, a silicon hydrolyzable group, and an amino group at a temperature of 20 to 350 ° C., Examples thereof include a method of grafting a polymer on the surface of a colorant or other additive.

The organic 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.
The average particle diameter of the fine particles is usually 0.5 to 30 μm, preferably 1 to 20 μm. The shape of the fine particles is not particularly limited, but a spherical shape, a spheroid and the like are preferable.

After the beads of the present invention are dispersed in a solvent containing a binder, a light diffusion film or sheet can be produced by uniformly applying and fixing the beads on a substrate such as a film or sheet.
The material of the film or sheet base material is preferably optically transparent and excellent in heat resistance and light resistance, such as polyethylene terephthalate resin, polycarbonate resin, polyimide resin, polyvinyl chloride resin, polyester resin, styrene-acrylonitrile. Examples of the resin include a copolymer resin and a cyclopolyolefin polymer resin, and a polyethylene terephthalate resin is preferably used.
The thickness of these substrate films and sheets is usually selected from 10 to 200 μm depending on the size of the display.
The thickness of the bead layer provided on the substrate is usually about 15 to 150 μm, preferably about 20 to 100 μm.
Moreover, as said binder, a transparent solvent type acrylic resin and a polyester resin are used, and it adheres with a urethane type crosslinking agent etc. at the time of drying. The ratio of the beads to the transparent resin is not particularly limited, but considering light diffusion performance, it 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.
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 the beads to the substrate surface, but is not particularly limited.

A light diffusion resin molded article can be produced by kneading the beads of the present invention into a thermoplastic or thermosetting matrix resin.
These matrix resins include polycarbonate resin, poly (meth) alkyl acrylate resin such as poly (meth) acrylate methyl resin, polystyrene resin, poly (meth) acrylate alkyl-polystyrene copolymer resin, polyester resin, etc. It is preferable to use a resin that is excellent in light resistance, light resistance, and rigidity.
The resin and beads are mixed with a mixer, kneaded with a melt kneader, and then extruded onto a sheet to obtain a light diffusion resin molded product. Moreover, after melt-kneading, it can take out as a pellet and the light-diffusion resin molding can be obtained by carrying out injection molding after melting this pellet.
The amount of the beads kneaded into the matrix resin is selected depending on the intended use and the required light diffusion capacity, but is usually 0.5 to 10 parts by weight.
Furthermore, when producing a coating type light diffusing film, a sheet, or a kneaded type light diffusing resin molding using these beads, two or more kinds of particles having different particle size distributions and average particle diameters can be blended and used. .

  According to the present invention, a light diffusing agent having a low refractive index, light transmittance, and light diffusivity comparable to that of a fluorine-containing alkyl (meth) acrylate copolymer can be obtained at a low cost.

  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 container, 190 parts of deionized water and 2 parts of polyvinyl alcohol were added. Separately, a monomer solution was prepared from 63 parts of i-butyl acrylate, 1 part of butanediol diacrylate, and 1 part of lauryl 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 1 hour. Next, the polymer particle suspension is cooled to 60 ° C., and a monomer emulsification comprising 12 parts of deionized water, 0.1 part of dioctyl sulfosuccinate sodium salt, 34 parts of methyl methacrylate, and 2 parts of ethylene glycol dimethacrylate. The liquid was added continuously over 10 minutes. The mixture was stirred at 70 ° C. in a nitrogen stream, and then aged 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 8.3 μm. Yield 93%.

In a dispersion container, 190 parts of deionized water and 2 parts of polyvinyl alcohol were added. Separately, a monomer solution was prepared from 50 parts of i-butyl acrylate, 13 parts of ethyl acrylate, 1 part of butanediol diacrylate and 1 part of lauryl 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 1 hour. Next, the polymer particle suspension is cooled to 60 ° C., and a monomer emulsification comprising 12 parts of deionized water, 0.1 part of dioctyl sulfosuccinate sodium salt, 34 parts of methyl methacrylate, and 2 parts of ethylene glycol dimethacrylate. The liquid was added continuously over 10 minutes. The mixture was stirred at 70 ° C. in a nitrogen stream, and then aged 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 8.5 μm. Yield 92%.
[Comparative Example 1]

In a dispersion container, 300 parts of deionized water and 2 parts of polyvinyl alcohol were added. Separately, a monomer solution was prepared from 55 parts of methyl methacrylate, 40 parts of trifluoroethyl methacrylate, 5 parts of ethylene glycol dimethacrylate, and 1 part of lauryl 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 8.2 μm. Yield 94%.
[Comparative Example 2]

In a dispersion container, 300 parts of deionized water and 2 parts of polyvinyl alcohol were added. Separately, a monomer solution was prepared from 95 parts of methyl methacrylate, 5 parts of ethylene glycol dimethacrylate and 1 part of lauryl 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 8.2 μm. Yield 95%.

Production of light diffusing plate (1) A biaxial extruder (PCM-30 manufactured by Ikegai Steel Co., Ltd.) with 99 parts of polycarbonate resin (polydioxydiphenylmethane carbonate, refractive index 1.589) and 1 part of beads of Example 1 was used. The mixture was kneaded and extruded at about 300 ° C. to obtain pellets. This pellet was injection molded by an injection molding machine to obtain a 2 mm thick plate.
(2) A light diffusing plate in which the same amount of polymer particles of Example 2, Comparative Example 1, and Comparative Example 2 were kneaded instead of the beads of Example 1 was prepared.
(3) Table 1 shows the measurement results of the optical properties of each light diffusion plate.

表１から明らかなように、ｉ-ブチルアクリレートを用いた多相構造を有するビーズ（実施例１及び２）はフッ素含有ビーズに全く遜色のない光拡散能を示した。

As is apparent from Table 1, beads having a multiphase structure using i-butyl acrylate (Examples 1 and 2) exhibited a light diffusing ability that was completely comparable to fluorine-containing beads.

Since the light diffusing resin composition of the present invention has excellent light diffusibility and total light transmittance, it is particularly a light diffusing sheet or plate for liquid crystal televisions, other fluorescent or white light illumination covers, and backlight-type translucent. It can be used in various fields such as billboards, displays, electrical decorations, interior translucent partitions, liquid crystal displays, projectors and projection TV screens.

Claims (5)

  (A) 50-99.8% by weight of isobutyl acrylate, (b) 0.1-20% by weight of a polyfunctional monomer having two or more vinyl groups in the molecule, and (c) other copolymerizable vinyls First-stage reaction in which 0 to 49.9 wt% of monomers are radically polymerized to form a crosslinked vinyl copolymer fine particle suspension, and (d) copolymerization to form a polymer having a glass point transfer of 50 ° C. or higher. A light diffusing agent comprising fine particles having an average particle diameter of 0.5 to 30 μm produced by a second-stage reaction in which a polymerizable vinyl monomer is added to the first-stage reaction liquid and absorbed or adhered to the first-stage particles to perform polymerization.   2. The light diffusing agent according to claim 1, wherein the weight ratio of the total amount of monomers used in the first-stage reaction and the monomers used in the second-stage reaction is 95/5 to 30/70.   In the polymerization, at least one additive selected from the group consisting of pigments, dyes, plasticizers, polymerization stabilizers, antioxidants, fluorescent brighteners, magnetic powders, ultraviolet absorbers, antistatic agents and flame retardants is blended. The light diffusing agent according to claim 1.   The light-diffusion film or light-diffusion sheet which apply | coated the light-diffusion agent in any one of Claims 1-3 to the film or sheet-like resin with the binder. A light diffusing resin molded article obtained by kneading the light diffusing agent according to claim 1 into a matrix resin.