JP2002212245A - Production method for light-diffusing particle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a particle which can inhibit the backward scattering of light by the control of refractive index distribution in the particle, have sufficient light diffusion properties, and are excellent in productivity. SOLUTION: The light-diffusing particles are polymer particles obtained from at least a first monomer group and a second monomer group combined so that the refractive index of a polymer obtained from the first monomer group is substantially higher than that of a polymer obtained from the second monomer group. The particles are produced by mixing a polymer obtained by the polymerization of a corresponding monomer selected from the first or second monomer group into at least a monomer which is selected from the first or second monomer group and contains a polymerization initiator, dispersing the resultant mixture in a medium, and subjecting the resultant dispersion to polymerization to form polymer particles provided that the polymerization is conducted while the monomer selected from the second or first monomer group is being further added before the completion of the polymerization so as to form polymer particles having an average particle size of 0.5-20 μm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing light-diffusing particles, and more particularly to a simple method for producing polymer particles having a desired refractive index distribution in the particles. In addition, it has characteristics such as low back scattering of light, high light diffusivity, and depolarization does not occur, and is suitable as a light diffusing material useful for applications such as improvement of viewing angle characteristics such as liquid crystal displays. The present invention relates to a method for producing light diffusing particles that can be used.

[0002]

2. Description of the Related Art Light diffusing materials are used in various fields such as light control materials, optical elements and display elements. In recent years, utilization of display materials such as liquid crystal displays for improving display quality and improving viewing angle characteristics has been advanced. As a configuration of the light diffusing material, for example, a method of forming fine irregularities on the surface, such as frosted glass, or a method of dispersing particles of several μm to about 10 μm in a resin film has been generally used.
However, although these methods can certainly scatter light, the scatter of light in the backward direction also increases, so that the amount of transmitted light decreases. In addition, since depolarization occurs, it is difficult to use such a liquid crystal display for a liquid crystal display which has been strongly demanded in recent years. In addition, since the amount of transmitted light is small for display materials, the load on the light source increases. Therefore, there is a demand for a light diffusing material which has little backscattering, has high light diffusing properties, and does not cause depolarization.

As a means for solving such a problem, for example, there is known a method of designing a concave and convex shape into a lens shape and utilizing light refraction. However, in this method, the formation of fine unevenness is complicated and the productivity is inferior, and the diffusion material is weak to contamination and impact, and when it is used in a liquid crystal display cell due to having unevenness, alignment disorder occurs, Since the display quality is remarkably deteriorated, it cannot be used for this purpose.

[0004] A method using fine particles is also known. In particular, the distribution of particles inside is not uniform because of the use of refraction instead of light scattering by simple particles, and light diffusing materials using fine particles in which the refractive index in the particles has been changed between the inside and the surface have been developed. Are known. In these methods, light diffusion is ensured while back scattering of light is suppressed to some extent.

[0005] By the way, as a method of forming particles comprising two or more components and having uneven distribution in the particles, a method of forming a core-shell latex by usual emulsion polymerization is generally used. However, the particle size of fine particles obtained by ordinary emulsion polymerization is about 0.1. 1 μm, which cannot exhibit the light diffusion property which is the object of the present invention.
A particle size of m is required. Therefore, in order to form such particles, various kinds of particles and a method for producing the same are actually proposed.

For example, Japanese Patent Application Laid-Open No. 9-127315 discloses a light diffusing plate in which the refractive index of fine particles is changed between the inside and the surface of the fine particles so that the refractive index difference between the fine particles and the transparent resin is reduced. In this case, as a method of forming such a particle, a method of coating a substance having a different refractive index on the surface of the fine particle (sputter deposition, CVD method, vacuum deposition method, etc.), or a modification by causing a cross-linking reaction or the like on the surface. (Electron beam irradiation, radiation irradiation, ion beam irradiation, etc.) are shown. In particular, silicon oxide,
Metal oxides such as zinc oxide and titanium oxide and thin films such as Mg ₂ F are formed.

[0007] However, these methods require special equipment, and very expensive equipment is required for mass production of particles. In addition, it is difficult to produce a mixture of organic components, and the combination of organic and inorganic components tends to cause deterioration of transparency due to low compatibility between the two components.

Further, for example, Japanese Patent Publication No. 11-109113
Japanese Patent Application Laid-Open Publication No. Hei 11 (1999) discloses a light diffusion film using core-shell structured particles composed of a core having a high refractive index and a shell having a low refractive index. However, in this method, since there is an interface having a different refractive index between the core and the shell, light is reflected and scattered at the interface, and as a result, the light diffusion property is improved,
The amount of transmitted light is reduced or depolarization occurs due to backscattering.

Japanese Patent Publication No. Hei 6-347617 discloses that the refractive index of fine particles is a particle having a refractive index distribution in which the refractive index difference between the inside and the surface is different from each other by 0.005 or more. A light diffusing plate using fine particles having a refractive index difference of 0.01 or less is shown. In this case, a method is described in which a polymerizable compound is impregnated into base particles by so-called seed emulsion polymerization to polymerize the particles. According to this method, it is possible to form fine particles between organic polymers and having no clear interface. However, in this method, since seed emulsion polymerization is used, steps such as formation, impregnation, and polymerization of seed particles are required, so that the steps are complicated, and there is a problem in production suitability. Alternatively, since the seed particles are formed once and then impregnated with the next monomer, there is a limitation that the kind and amount of the monomer that can be used are limited due to compatibility with the polymer already formed.

On the other hand, a monomer Ml giving a high refractive index polymer is added to an aqueous PVA solution, and polymerization is carried out while dropping a monomer M2 giving a low refractive index polymer with a short delay while performing suspension polymerization. A method of adding a monomer Ml to give a polymer to an aqueous PVA solution, performing suspension polymerization to form particles, and then adding a monomer M2 to give a low refractive index polymer and an initiator to carry out polymerization again, etc. There is known a method of forming particles in which the internal refractive index is continuously changed. (Yasuhiro Koike et al. A
pll. Opt. 33 (16) 3394 (1994))
However, in this method, since the usual suspension polymerization is used, the particle diameter is about 0.5 to 1. 1 mm, which is a so-called Grin lens application, which is different from the application of the present invention.

As a method for forming micron-sized particles having non-uniform particles, a method using microsuspension polymerization is also known. (Michael F et al., J. Polym.
Sci. Part A 38 345 (2000)) In this method, the monomer Ml is first polymerized to about 20%, the reaction liquid is micro-suspended in an aqueous phase, and the polymerization is further advanced. is there.

However, in this method, the first step involves a complicated and difficult-to-control step in which a chain reaction called a polymerization reaction is advanced halfway, and the reaction solution is used in the next step. There is. Further, the concept of controlling the refractive index distribution and arranging a component having a high refractive index on the center side of the particle is not shown at all in this, which is completely different from the field of the present invention. As described above, there is no known method for producing particles which suppresses back scattering of light, has sufficient light diffusing properties, and is excellent in production suitability.

[0013]

In view of these circumstances,
The present invention provides a method for producing particles having sufficient light diffusivity and excellent production suitability by suppressing the backscattering of light by controlling the refractive index distribution in the particles.

[0014]

Means for Solving the Problems As a result of our intensive studies to solve these problems, we have arrived at the present invention. That is, the present invention relates to <1> polymer particles obtained from at least a first monomer group and a second monomer group, wherein the polymer obtained from the first monomer group has a refractive index from the second monomer group. A combination which is substantially higher than the refractive index of the obtained union, and which is at least a monomer selected from the first or second monomer group and a first or second monomer corresponding to the polymerization initiator, respectively. After mixing the polymer obtained by polymerization of the monomers selected from the group, the mixture is dispersed in a medium, and then, before the polymerization is terminated in the process of forming the polymer particles by the polymerization reaction, each further The polymerization is performed while post-adding a monomer selected from the second or first monomer group so that the average particle size is 0.5 to
A method for producing light-diffusing particles, which comprises forming polymer particles of 20 μm. <2> The method for producing light diffusing particles according to <1>, wherein a chain transfer agent is further used in the polymerization step. <3> a compound in which the first monomer group has at least one kind of an aromatic ring or a bromine atom, a chlorine atom, and a sulfur atom in a molecule and has at least one ethylenic double bond, and the second monomer <1> or the above, wherein the group is a combination of compounds having neither an aromatic ring or a bromine atom, a chlorine atom, and a sulfur atom in the molecule, and having at least one ethylenic double bond. <2
> The method for producing light-diffusing particles described in (1). <4> The method according to any one of <1> to <3>, wherein the medium is water or an aqueous medium.

[0015]

Embodiments of the present invention will be described below in detail. For the formation of the polymer particles, at least one monomer is selected from at least the first monomer group and the second monomer group and used. The first monomer group and the second monomer group are combinations in which the refractive index of the polymer obtained from the first monomer group is substantially higher than the refractive index of the polymer obtained from the second monomer group. If so, the type of the monomer is not particularly limited. In practice, the difference in refractive index is preferably 0.01 or more, more preferably 0.05 or more, and particularly preferably 0.1 or more. In addition, about the refractive index of the polymer obtained from each monomer, for example,
POLYMER HANDBOOK (JOHN WIL
EY & Sons).

In order to produce such a difference in the refractive index, the first monomer group has at least one of an aromatic ring or a bromine atom, a chlorine atom and a sulfur atom in the molecule and has a property of ethylenic acid. Compounds having at least one heavy bond are exemplified. More specifically, styrene, vinylnaphthalene, chlorostyrene, bromostyrene, chloromethylstyrene, methoxystyrene, methylstyrene, divinylbenzene, phenyl (meth) acrylate, benzyl (meth) acrylate, benzyl (meth) acrylamide, 2-phenyl Ethyl (meth) acrylate, 2-
(Tribromophenyl) ethyl (meth) acrylate,
2- (tribromophenyloxy) ethyl (meth) acrylate, 3- (m-methylbromophenoxy) -2-
Hydroxypropyl (meth) acrylate, 2,2-bis (4- (meth) acryloyloxyethoxy-3,5
-Dibromophenyl) propane, 3- (m-methylchlorophenoxy) -2-hydroxypropyl (meth) acrylate, bis (4-methacryloylthiophenenyl) sulfide, bis (4-vinylthiophenyl) sulfide, bis (β- (Meth) acryloyloxyethylthio) xylylene, diallyl phthalate, vinyl chloride, vinylidene chloride, vinyl benzoate, vinyl chlorobenzoate, vinyl bromobenzoate, allyl benzoate,
Allyl chlorobenzoate, allyl bromobenzoate and the like can be mentioned. The monomers used may be one of these or a combination of two or more thereof.

On the other hand, as the second monomer group,
Any of aromatic ring or bromine atom, chlorine atom and sulfur atom
Not having and having at least 1 ethylenic double bond
Compounds. More specifically, alkyl (meth
(T) acrylate (where the alkyl group is methyl,
, N-propyl, i-propyl, n-butyl, i-butyl
Chill, t-butyl, hexyl, cyclohexyl, 2-e
Tylhexyl), alkyl (meth) acryle fluoride
(As the fluorinated alkyl group, (CH_Two)_mC _nF
_{2n + 1}(M represents 0 to 3, n represents 1 to 10), hexaflo
Isopropyl, trifluoroisopropyl, etc.),
TA) Acrylic acid, vinyl acetate, alkyl vinyl ether
(As the alkyl group, methyl, ethyl, n-propyl
, I-propyl, n-butyl, i-butyl, t-butyl
Hexyl, cyclohexyl, 2-ethylhexyl
Etc.).

Among the combinations of these monomer groups,
The monomers selected from the first monomer group are styrene, substituted styrene, benzyl (meth) acrylate, and 2-phenylethyl (meth), particularly from the viewpoints of their polymerizability, solubility, supply properties, and differences in refractive index. Acrylate, 2-
(Tribromophenyl) ethyl (meth) acrylate,
2- (tribromophenyloxy) ethyl (meth) acrylate, bis (4-methacryloylthiophenyl) sulfide, bis (4-vinylthiophenyl) sulfide, diallyl phthalate, a monomer selected from the second monomer group Are preferably alkyl (meth) acrylates and fluorinated alkyl (meth) acrylates.

As the polymerization initiator, known thermal polymerization initiators and photopolymerization initiators can be used. For example, as a thermal polymerization initiator, 2,2′-azobisisobutyronitrile,
Examples include azo initiators such as 2,2′-azobis (2,4-dimethylvaleronitrile) and peroxide initiators such as benzoyl peroxide.

As the photopolymerization initiator, US Pat.
No. 7660, vicinal polyketaldonyl compound, U.S. Pat. No. 2,448,828, acyloin ether compound, U.S. Pat. No. 2,722,512, .alpha.-hydrocarbon substituted aromatic Acyloin compounds, polynuclear quinone compounds described in U.S. Pat. Nos. 3,046,127 and 2,951,758, combinations of triarylimidazole dimers and p-aminoketones described in U.S. Pat. No. 3,549,367, JP-B-51 Benzothiazole compound and trihalomethyl-s-triazine compound described in U.S. Patent No. 48516, trihalomethyl-s-triazine compound described in U.S. Patent No. 4,239,850.
Examples thereof include s-triazine compounds and trihalomethyloxadiazole compounds described in U.S. Pat. No. 4,221,976.

Further, as the photopolymerization initiator, benzophenone, camphorquinone, 4,4-bis (dimethylamino) benzophenone, 4-methoxy-4'-dimethylaminobenzophenone, 4,4'-dimethoxybenzophenone, 4-dimethyl Aminobenzophenone, 4-dimethylaminoacetophenone, benzylanthraquinone,
Bis such as 2-tert-butylanthraquinone, 2-methylanthraquinone, xanthone, thioxanthone, 2-chlorothioxanthone, 2,4-diethylthioxanthone, fluorenone, acridone, bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide Acylphosphine oxides, Lucirin T
Aromatic ketones such as acylphosphine oxides such as PO, α-hydroxy or α-aminoacetophenones, α-hydroxycycloalkylphenyl ketones, and dialkoxyacetophenones;

Benzoin and benzoin ethers such as benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether and benzoin phenyl ether; 2- (o-chlorophenyl) -4,5-diphenylimidazole dimer, 2- (o-chlorophenyl) ) -4,5-di (m-methoxyphenyl) imidazole dimer, 2- (o-fluorophenyl) -4,5-diphenylimidazole dimer, 2- (o-methoxyphenyl) -4,5- Diphenylimidazole dimer, 2-
2,4,6-triarylimidazole dimers such as (p-methoxyphenyl) -4,5-diphenylimidazole dimer, and other U.S. Patent Nos. 3,784,557 and 42.
Nos. 52887, 4311783, 4459349
Nos. 4,410,621 and 4,622,286;

Polyhalogen compounds such as carbon tetrabromide, phenyltribromomethylsulfone and phenyltrichloromethylketone; JP-A-59-133428, JP-B-57
No.-1819, JP-B-57-6096, U.S. Pat.
A compound described in 615455;

2,4,6-tris (trichloromethyl)
-S-triazine, 2-methoxy-4,6-bis (trichloromethyl) -s-triazine, 2-amino-4,6
-Bis (trichloromethyl) -s-triazine, 2-
JP-A-58-29803 such as (p-methoxystyryl) -4,6-bis (trichloromethyl) -s-triazine
An s-triazine derivative having a trihalogen-substituted methyl group described in (1);

Methyl ethyl ketone peroxide, cyclohexanone peroxide, 3,3,5-trimethylcyclohexanone peroxide, benzoyl peroxide, di-tert-butyldiperoxyisophthalate, 2,5-dimethyl-2,5-di (benzoylperoxy) ) Hexane, tert-butylperoxybenzoate, a, a'-bis (tert-butylperoxyisopropyl) benzene, dicumyl peroxide, 3,3 ', 4,4'-tetra- (tert-butylperoxycarbonyl) ) Japanese Patent Application Laid-Open No.
Organic peroxides described in No. 9-189340;

Azinium salts described in US Pat. No. 4,743,530; organic boron compounds; phenylglyoxalic esters such as methyl phenylglyoxalate; bis (η ^{5, 2} -cyclopentadien-1-yl) ) -Bis (2,6-difluoro-3- (1H-pyrrol-1-yl) -phenyl) titanium and the like; η ⁵ -cyclopentadienyl-η ⁶ -cumenyl-iron (1 +)-hexafluoro Iron allene complexes such as phosphate (1-); diaryliodonium salts such as diphenyliodonium salt; and triarylsulfonium salts such as triphenylsulfonium salt.

More detailed examples of the above photopolymerization initiators,
Examples of other types of photopolymerization initiators include paragraphs [0067] to [01] of JP-A-10-45816.
32].

As the photopolymerization initiator, a material composed of a combination of two or more compounds can be used. For example, a combination of 2,4,5-triarylimidazole dimer and mercaptobenzoxazole or the like,
4,4'- described in U.S. Pat. No. 3,427,161.
Combination of bis (dimethylamino) benzophenone, benzophenone and benzoin methyl ether, benzoyl-N-methylnaphthothiazoline and 2,4-bis (trichloromethyl) -6- (4'-) described in U.S. Pat. No. 4,239,850. Methoxyphenyl) -triazole, a combination of a dialkylaminobenzoic acid ester described in JP-A-57-23602 and dimethylthioxanthone, and a 4,4′-bis (JP-A-59-78339) described in JP-A-59-78339. Dimethylamino) benzophenone, benzophenone, and a polymethyl halide compound.

In the case of a photopolymerization initiator comprising two or more kinds, a combination of 4,4'-bis (diethylamino) benzophenone and benzophenone, a combination of 2,4-diethylthioxanthone and ethyl 4-dimethylaminobenzoate Or a combination of 4,4'-bis (diethylamino) benzophenone and 2,4,5-triarylimidazole dimer.

Further, a chain transfer agent can be used in combination. Examples of chain transfer agents, for example, dodecyl mercaptan, octyl mercaptan, mercaptans such as mercaptoacetic acid, dibutyl sulfide, sulfides such as dibutyl disulfide, carbon tetrachloride, chloroform, carbon tetrabromide, butyl bromide and the like Halogen,
Examples thereof include amines such as triethylamine and butylamine. The chain transfer agent is used by mixing with a mixture of a monomer selected from the first or second monomer group, a polymerization initiator, and a polymer obtained by polymerization of the corresponding first or second monomer group. Or a mixture with a monomer selected from the second or first monomer group to be added later, or both. The amount of addition is not particularly limited, but is preferably 0.01 to 30 mol% based on the total amount of the monomers,
5-20 mol% is more preferable, and 0.1-15 mol%
% Is particularly preferred. In addition, these monomer liquids, or
These solvents can be added to the monomer / polymer mixture as needed.

As a medium for dispersing and polymerizing these monomers, polymers, initiators and the like, water or an aqueous medium is preferable. The aqueous medium is mainly composed of water, for example, methanol, ethanol, acetone, TH
A water-soluble solvent such as F, or polyvinyl alcohol,
An aqueous solution containing at least one or more of a water-soluble polymer such as poly (sodium acrylate), gelatin, methylhydroxycellulose, and polyethylene glycols, and a surfactant such as dodecylbenzenesulfonic acid is shown. These can be appropriately selected and used from the combination with the monomer to be used, particularly for imparting dispersion stability of particles and adjusting the particle diameter.

In the present invention, in the formation of particles, a polymer obtained from the monomer group 1 or 2 is synthesized in advance, and this is used in combination with a monomer and a polymerization initiator selected from the monomer group 1 or 2 respectively. Used. Weight average molecular weight of the polymer, the polymer / monomer 1 group or monomer 2
The desired average particle size can be easily adjusted by the combined amount ratio of the groups and the dispersion conditions (apparatus, rotation speed, dispersion time, etc.). That is, the particle size is determined by a combination of these conditions, and the conditions cannot be specified unconditionally, but the weight average molecular weight of the polymer is approximately 2%.
000 to 400,000, preferably 2,000 to 100,000, and the combined amount ratio of the polymer / monomer 1 group or 2 group is 5 to 80/9.
It is 5 to 20 mass ratio, preferably 5 to 50/95 to 50 mass ratio. As the dispersing device, various types of known dispersing devices such as the present modifier and a bead mill can be used, and appropriate dispersing conditions can be selected and used for each device.

In this way, a polymer obtained by previously synthesizing at least a monomer selected from the monomer group 1 or the second group, a monomer selected from the monomer group,
A dispersion of the mixture comprising the polymerization initiator is obtained. Since the average particle size of the dispersed particles at the time of this dispersion affects the particle size of the finally obtained light diffuser particles, it is preferably 0.3 to 20 μm,
More preferably, it is 0.4 to 15 μm.

Next, the polymerization of this dispersion is started. The polymerization is carried out by heating when a thermal polymerization initiator is used, and by light irradiation when a photopolymerization initiator is used. In this case, it is desirable to carry out the polymerization under a nitrogen stream in order to suppress the termination of the polymerization. In the course of this polymerization, a monomer selected from the other monomer group (if the monomer used in the first step is the first monomer group, the second monomer group, and conversely, the monomer used in the first step is the monomer Second
Group, the first group of monomers) is added to the polymerization system.
The monomer may be added all at once, may be added in several portions, or may be continuously dropped, but a continuous dropping method is preferred.

The start of the dropping of the monomer may be started at the same time as the start of the polymerization of the first-stage monomer, or may be started after a certain period of time. It is preferable to start earlier than the time that ends. Whether or not the polymerization of the monomer is substantially terminated can be determined by the state of the dispersion, the viscosity, the amount of the residual monomer, and the like in addition to the polymerization time, but the polymerization time depends on the polymerization conditions. But about 2
６6 hours, preferably about 2-5 hours. Further, the speed of dropping the monomer is not particularly limited, but is preferably about 10 minutes to 3 hours, more preferably 20 minutes to 2 hours. By such an operation, the refractive index substantially differs between the central part and the outer peripheral part of the particles, and the average particle diameter is 0.5 to 20 μm, preferably 0.8 to 20 μm, more preferably 1.5 to 15 μm. can get.
When the average particle size of the polymer particles is smaller than 0.5 μm, the light diffusion property is insufficient, and when the average particle diameter is larger than 20 μm, the back diffusion increases, and the film forming property of a uniform light diffusion film becomes poor. However, it is not preferable as light diffusing particles.

When the particles thus obtained are used as a light-diffusing material, they may be dispersed in a binder having a refractive index substantially equal to the outermost part of the particles, or the particles may be used together. It is preferable to use a fused film. Such binder is not particularly limited as long as it has a refractive index substantially equal to the outermost,
An aqueous latex or aqueous solvent solution of a water-soluble polymer such as polyvinyl alcohol, gelatin, methylhydroxycellulose, or polyethylene glycol, or a vinyl polymer such as poly (meth) acrylate is preferable. For the purpose of making the refractive index substantially equal to the outermost part of the particles, the monomer 1 used as an outer component of the particles may be used.
A polymer obtained by polymerization of a component mainly composed of the same component as the monomer selected from the group or the group 2 is particularly preferable.

For use as a light diffusing material, an aqueous solution of these binders, a latex dispersion or the like is mixed with the particles of the present invention, for example, glass, tricellulose acetate film, polyethylene terephthalate film, polymethyl methacrylate, norbornene. For example, a method such as coating and drying or dry laminating on a transparent substrate such as a polycarbonate substrate can be used. When an optically isotropic substrate is used as these substrates, it can be disposed inside the polarizing plate of the liquid crystal display device, and a display device with high resolution can be obtained. The thickness of the coating film is preferably from 0.5 to 50 μm, particularly preferably from 2 to 20 μm.

These coatings can be performed by a usual coating method, that is, by appropriately selecting a wire bar, extrusion, doctor blade, spin coating, slit die, or the like. Further, it is also possible to apply and dry on a temporary support in advance and then dry-laminate the desired substrate by a dry lamination method. One or both surfaces of these light diffusers may be provided with a hard coat layer, an antifouling layer, an antireflection layer, an antiglare layer, a flattening layer, an adhesive layer, an antistatic layer, and the like.

[0039]

EXAMPLES Examples of the present invention will be described below, but the present invention is not limited to these examples. Unless otherwise specified, “parts” means “parts by mass”. [Evaluation Method] The light diffusers obtained in Examples and Comparative Examples were evaluated according to the following three points based on the following items. The higher the score, the better. (Backscattering): Black paper is laid under the light diffuser and visually observed from above. Black is better. (Light diffusivity): The light diffuser is attached to an aluminum vapor-deposited film and visually observed from above. The better the metallic luster of the aluminum disappears and looks white. (Depolarization): A light diffuser is attached to an aluminum vapor-deposited film, and a １ ／ λ plate and a linear polarizer are attached on the light diffuser in such a direction as to completely cut off specular reflected light, and visually observed from above. The better the reflected light is cut and looks black.

[Synthesis Example 1] 1.0 part of a polystyrene oligomer (weight average molecular weight 5000) and styrene 9.
0 part, 0.35 part of dodecyl mercaptan, 0.21 part of 2,2′-azobis (2,4-dimethylvaleronitrile) (V-65, manufactured by Wako Pure Chemical Industries, Ltd.) were uniformly dissolved, and this was dissolved in P.
The mixture is poured into 40.0 parts of a 1.25% by mass aqueous solution of VA (PVA is PVA-205 manufactured by Kuraray Co., Ltd.), and subjected to a dispersion treatment at 10,000 rpm for 5 minutes using a homogenizer. While stirring the obtained dispersion liquid under a nitrogen stream at 400 rpm, the internal temperature is raised to 60 ° C. to initiate polymerization. 30 minutes after the temperature was raised, 10.0 parts of ethyl methacrylate was added dropwise over 1 hour, and the polymerization reaction was continued for another 4 hours. The resulting reaction solution was filtered through a 100-mesh filter cloth to obtain a dispersion of polymer particles. The average particle size of the particles was 2.4 μm.

Synthesis Example 2 In Synthesis Example 1, 10.0 parts of ethyl methacrylate were changed to 4.75 parts of ethyl methacrylate and 0.25 part of methacrylic acid, and the dropping time was changed from 1 hour to 30 minutes. Otherwise in the same manner as in Synthesis Example-1, a dispersion of polymer particles was obtained. The average particle size of the particles is 4. 1 μm.

[Synthesis Example-3] 1.0 part of polybenzyl methacrylate (mass average molecular weight 10,000), 9.0 parts of benzyl methacrylate, 0.2 parts of dodecyl mercaptan
0 parts, 2,2′-azobis (2,4-dimethylvaleronitrile) (V-65, manufactured by Wako Pure Chemical Industries, Ltd.) 13 parts were uniformly dissolved, and this was mixed with a 1.25% by mass aqueous solution of PVA (P
VA is poured into 40.0 parts of PVA-205 (manufactured by Kuraray Co., Ltd.) and subjected to a dispersion treatment at 10,000 rpm for 5 minutes using a homogenizer. The obtained dispersion is subjected to 400 rpm under a nitrogen stream.
While stirring at m, the temperature is raised to an internal temperature of 60 ° C. to initiate polymerization. 30 minutes after the temperature was raised, 5.0 parts of ethyl methacrylate was added dropwise over 30 minutes, and the polymerization reaction was continued for another 4 hours. The resulting reaction solution was filtered through a 100-mesh filter cloth to obtain a dispersion of polymer particles. The average particle size of the particles is 3. 1 μm.

[Synthesis Example-4] In Synthesis Example-3, a step of dropping 5.0 parts of ethyl methacrylate over 30 minutes 30 minutes after the temperature was raised, and adding 5.0 parts of ethyl methacrylate 30 minutes immediately after the temperature was raised. A dispersion liquid of polymer particles was obtained by performing the same treatment as in Synthesis Example-3 except that the composition was changed so as to be added dropwise over minutes. The average particle size of the particles was 2.7 μm.

[Comparative Synthesis Example-1] 10.0 parts of styrene,
0.35 parts of dodecyl mercaptan (2,2'-azobis (2,4-dimethylvaleronitrile) (manufactured by Wako Pure Chemical Industries, Ltd.)
V-65) 0.21 part was uniformly dissolved, and this was dissolved in a 1.25% by weight aqueous solution of PVA (PVA was PVA manufactured by Kuraray Co., Ltd.).
-205) Pour into 40.0 parts and add 100 with homogenizer.
Perform dispersion treatment at 00 rpm for 5 minutes. While stirring the obtained dispersion at 400 rpm under a nitrogen stream, an internal temperature of 60 ° C.
The temperature is raised to start polymerization. 30 minutes after the temperature was raised, 10.0 parts of ethyl methacrylate was added dropwise over 1 hour, and the polymerization reaction was continued for another 4 hours. The resulting reaction solution was filtered through a 100-mesh filter cloth to obtain a dispersion of polymer particles. The average particle size of the particles was 0.10 μm.

[Comparative Synthesis Example 2] 1.0 part of a polystyrene oligomer (weight average molecular weight 5000), 9.0 parts of styrene, 0.35 part of dodecyl mercaptan, 2,2 '
0.21 part of azobis (2,4-dimethylvaleronitrile) (V-65 manufactured by Wako Pure Chemical Industries) was uniformly dissolved, and this was dissolved in a 1.25% by mass aqueous solution of PVA (PVA was PVA manufactured by Kuraray Co., Ltd.) -205) Pour the mixture into 40.0 parts, and perform a dispersion treatment with a homogenizer at 10,000 rpm for 5 minutes.
The resulting dispersion was heated to an internal temperature of 60 ° C. while stirring at 400 rpm under a nitrogen stream, and heated and stirred for 6 hours to obtain a dispersion of polymer particles. The average particle size of the particles is 3.2
μm.

[Comparative Synthesis Example-3] 1.0 part of a polystyrene oligomer (weight average molecular weight 5000), 9.0 parts of styrene, 10.0 parts of ethyl methacrylate, 0.35 part of dodecyl mercaptan, 2,2'-azobis ( 2,4
-Dimethylvaleronitrile) (V-6 manufactured by Wako Pure Chemical Industries, Ltd.)
5) Dissolve 0.21 part uniformly and mix it with PVA 1.2
5% by weight aqueous solution (PVA is PVA-2 manufactured by Kuraray Co., Ltd.)
05) Pour into 80.0 parts and use a homogenizer to 10,000
Disperse for 5 minutes at rpm. The obtained dispersion was heated to an internal temperature of 60 ° C. while stirring at 400 rpm under a nitrogen stream, and heated and stirred for 6 hours to polymerize. The resulting reaction solution was filtered through a 100-mesh filter cloth to obtain a dispersion of polymer particles. The average particle size of the particles was 3.7 μm.

[Comparative Synthesis Example-4] 1.0 part of polybenzyl methacrylate (weight average molecular weight 10,000), 9.0 parts of benzyl methacrylate, 0.20 part of dodecyl mercaptan, 2,2'-azobis (2,4- 0.13 parts of dimethylvaleronitrile (V-65 manufactured by Wako Pure Chemical Industries) was uniformly dissolved, and this was dissolved in a 1.25% by weight aqueous solution of PVA (PVA was PVA-205 manufactured by Kuraray Co., Ltd.) 40.0
Pour the mixture into a homogenizer and perform a dispersion treatment at 10,000 rpm for 5 minutes. The resulting dispersion is placed under a nitrogen stream at 400
While stirring at rpm, the internal temperature was raised to 60 ° C., and the mixture was heated and stirred for 6 hours to obtain a dispersion of polymer particles. The average particle size of the particles was 2.8 μm.

[Comparative Synthesis Example-5] 1.0 part of polybenzyl methacrylate (weight average molecular weight 10,000), 9.0 parts of benzyl methacrylate, 5.0 parts of ethyl methacrylate, 0.20 parts of dodecyl mercaptan, 2,2 '
0.13 parts of azobis (2,4-dimethylvaleronitrile) (V-65, manufactured by Wako Pure Chemical Industries) is uniformly dissolved, and this is dissolved in a 1.25% by weight aqueous solution of PVA (PVA is Kuraray Co., Ltd.)
Of PVA-205), and subjected to a dispersion treatment at 10,000 rpm for 5 minutes with a homogenizer. While stirring the obtained dispersion at 400 rpm under a nitrogen stream,
The internal temperature was raised to 60 ° C., and the mixture was heated and stirred for 6 hours to polymerize.
The resulting reaction solution was filtered through a 100-mesh filter cloth to obtain a dispersion of polymer particles. The average particle size of the particles is 2.5
μm.

[Comparative Synthesis Example-6] 1.0 part of polybenzyl methacrylate (weight average molecular weight 10,000), 9.0 parts of benzyl methacrylate, 0.20 part of dodecyl mercaptan, 2,2'-azobis (2,4-dimethyl) 0.13 parts of valeronitrile) (V-65 manufactured by Wako Pure Chemical Industries) was uniformly dissolved, and this was dissolved in a 1.25% by weight aqueous solution of PVA (PVA was PVA-205 manufactured by Kuraray Co., Ltd.) 60.0%
Of the mixture, and subjected to a dispersion treatment at 10,000 rpm for 5 minutes using a homogenizer. The resulting dispersion is placed under a nitrogen stream at 400
While stirring at rpm, the internal temperature was raised to 60 ° C., and the mixture was heated and stirred for 6 hours to polymerize. 5.0 parts of ethyl methacrylate and 0.1 part of dodecyl mercaptan were added to the obtained reaction solution.
A solution prepared by uniformly dissolving 7 parts of 0.12 parts of 2,2-azobis (2,4-dimethylvaleronitrile) (V-65 manufactured by Wako Pure Chemical Industries, Ltd.) is added dropwise and stirred at room temperature for 2 hours. While stirring at 400 rpm under a nitrogen stream, the internal temperature was raised to 60 ° C., and the mixture was heated and stirred for 6 hours to polymerize. The resulting reaction solution was filtered through a 100-mesh filter cloth to obtain a dispersion of polymer particles. The average particle size of the particles was 2.7 μm.

Example 1 The particle dispersion of Synthesis Example 1 and a separately synthesized latex of polyethyl methacrylate (particle diameter: 0.1 μm) were mixed at a solid content weight ratio of 1: 1, and triacetyl was added. It is applied on a cellulose film with a wire bar so as to have a solid content of 10 g / m ^2.
The light diffuser was obtained by drying at ℃. Table 1 shows the results.

(Projection Example 2) A copolymer latex of 47.5 parts of ethyl methacrylate and 2.5 parts of methacrylic acid (particle size: 0.08 μm) separately prepared from the particle dispersion of Synthesis Example 2
m) The liquid was mixed to a solid content weight ratio of 1 to 1, applied to a triacetyl cellulose film with a wire bar at a solid content of 15 g / m ² , dried at 120 ° C., and the light diffuser was dried. Obtained. Table 1 shows the results.

Example 3 A light diffuser was obtained in exactly the same manner as in Example 1 except that the particle dispersion of Example 1 was changed to the particles of Synthesis Example 3. Table 1 shows the results.

Example 4 A light diffuser was obtained in exactly the same manner as in Example 1 except that the particle dispersion of Example 1 was changed to the particles of Synthesis Example 4. Table 1 shows the results.

Example 5 The particle dispersion of Synthesis Example 3 was applied onto a film of triacetyl cellulose at a solid content of 10 g / m ^2.
And dried at 120 ° C. to obtain a light diffuser. Table 1 shows the results.

Comparative Example 1 The particle dispersion of Comparative Synthesis Example 1 and a separately synthesized latex of polyethyl methacrylate (particle diameter: 0.1 μm) were mixed at a solid content overlap ratio of 1: 1. It was applied on an acetylcellulose film with a wire bar so as to have a solid content of 10 g / m ² and dried at 120 ° C. to obtain a light diffuser for comparison. Table 1 shows the results.

(Comparative Example 2) A light diffuser for comparison was obtained in exactly the same manner as in Comparative Example 1, except that the particle dispersion was changed to Comparative Synthesis Example 2. Table 1 shows the results.

Comparative Example 3 A light diffuser for comparison was obtained in exactly the same manner as in Comparative Example 1, except that the particle dispersion was changed to Comparative Synthesis Example 3. Table 1 shows the results.

(Comparative Example 4) A light diffuser for comparison was obtained in exactly the same manner as in Comparative Example 1 except that the particle dispersion was changed to Comparative Synthesis Example 4. Table 1 shows the results.

(Comparative Example 5) A light diffuser for comparison was obtained in exactly the same manner as in Comparative Example 1, except that the particle dispersion was changed to Comparative Synthesis Example 5. Table 1 shows the results.

(Comparative Example 6) A light diffuser for comparison was obtained in exactly the same manner as in Comparative Example 1, except that the particle dispersion was changed to Comparative Synthesis Example 6. Table 1 shows the results.

Comparative Example 7 The particle dispersion of Comparative Synthetic Example 3 and the latex liquid of Comparative Synthetic Example 1 were mixed at a solid content weight ratio of 1: 1. It was applied so as to have a solid content of 10 g / m ² and dried at 120 ° C. to obtain a light diffuser for comparison. Table 1 shows the results.

[0062]

[Table 1]

As shown in Table 1, the light diffuser obtained according to the present example shows good characteristics for all three necessary items, but at least one item is practical in the comparative example. It shows the usefulness of the present invention by showing characteristics that do not withstand the above.

[0064]

According to the method for forming particles of the present invention, it is possible to suppress the back scattering of light, to form particles having sufficient light diffusivity and excellent in suitability for production. By using this, it is possible to provide a light-diffusing material which has little backscattering and high light-diffusing properties and does not cause depolarization. These light diffusion materials are dimming materials, optical elements,
It is useful in various fields such as display elements and screens, and is particularly useful for improving the display quality of display materials such as liquid crystal displays.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H042 BA02 BA15 BA20 4J011 NA13 NA25 NA26 NA28 NB04 PA65 PA66 PA67 PA68 PA69 PA70 PB06 PB40 PC02 4J026 AA17 AA18 AA21 AA30 AA31 AA37 AA38 AA45 BA25 BA27 DB04 FA02 GA06

Claims (4)

[Claims] 1. A polymer particle obtained from at least a first monomer group and a second monomer group, wherein the polymer obtained from the first monomer group has a refractive index of a polymer obtained from the second monomer group. A combination substantially higher than the refractive index of the coalesced, selected from at least a monomer selected from the first or second monomer group and a first or second monomer group corresponding to the polymerization initiator, respectively. After the polymer obtained by the polymerization of the obtained monomers is mixed, the mixture is dispersed in a medium, and then, before the polymerization is terminated in the process of forming the polymer particles by the polymerization reaction, a second liquid is further added. Alternatively, the light-diffusing particles are characterized in that they are polymerized while post-adding a monomer selected from the first monomer group to form polymer particles having an average particle size of 0.5 to 20 μm. Production method. 2. The method for producing light-diffusing particles according to claim 1, wherein a chain transfer agent is further used in the polymerization step. 3. The method according to claim 1, wherein the first monomer group has at least one of an aromatic ring, bromine atom, chlorine atom and sulfur atom in the molecule.
A compound having a species and having at least one ethylenic double bond, wherein the second monomer group does not have an aromatic ring or a bromine atom, a chlorine atom, or a sulfur atom in the molecule;
The method according to claim 1 or 2, wherein the combination is a combination of compounds having at least one ethylenic double bond. 4. The method for producing light diffusing particles according to claim 1, wherein the medium is water or an aqueous medium.