JP5401553B2 - Single hollow particle for light diffusion - Google Patents

Description

  The present invention relates to a single hollow particle for light diffusion. More specifically, the present invention relates to a single hollow particle for light diffusion having excellent light diffusibility. The single hollow particle for light diffusion of the present invention is suitable as a raw material for a light diffusing plate or a light guide plate used for TV screens, lighting covers, liquid crystal backlights, or the like, or a paint. The present invention also relates to a lighting cover in which single hollow particles for light diffusion are blended in a transparent resin. Since the illumination cover of the present invention is excellent in light diffusibility, it can be suitably used as an illumination cover using various light sources such as fluorescent lamps and LEDs.

  Conventionally, polymer particles produced by suspension polymerization are used as light diffusing agents such as light reflecting materials such as paints and cosmetics, and light diffusing plates for liquid crystal backlights. That is, in paints and cosmetics, the light diffusing agent imparts whiteness by refracting and reflecting light. In the light diffusing plate, the light diffusing agent scatters the incident light so that light incident from the side of the light diffusing plate by a cold cathode tube or the like can be emitted from the surface of the light diffusing plate with uniform brightness. Yes. As such polymer particles, for example, acrylic polymer particles and styrene polymer particles are used. Here, it is known that the acrylic polymer particles have a slightly low refractive index although they have excellent weather resistance. On the other hand, styrene polymer particles are known to have a high refractive index but poor weather resistance. Therefore, acrylic-styrene polymer particles having both characteristics are also used. Furthermore, polymer particles are also known which have an effect of reflecting or scattering light by having pores inside.

As a method for producing polymer particles having pores therein, JP-A-59-193901 (Patent Document 1), JP-A-4217515 (Patent Document 2) and JP-A-2006-117920 (Patent Document) The method described in 3) is known.
In JP-A-59-193901, when a hydrophobic monomer is polymerized in an aqueous medium, an ionic surfactant is added to the aqueous medium, and a nonionic surfactant is added to the hydrophobic monomer. It is said that hollow polymer particles can be obtained by the addition.

According to Japanese Patent No. 4217515, hollow polymer particles are obtained by polymerizing a hydrophobic monomer and a (meth) acrylic hydrophilic monomer in an aqueous medium. .
In JP 2006-117920 A, polymer particles having a plurality of pores are obtained by polymerizing a (meth) acrylate monomer in an aqueous medium containing a surfactant having a specific structure. It is supposed to be

JP 59-193901 A Japanese Patent No. 4217515 JP 2006-117920 A

However, Japanese Patent Application Laid-Open No. 59-193901 and Japanese Patent No. 4217515 disclose examples in which single hollow particles are obtained when an acrylic monomer is used as a crosslinkable vinyl monomer. There has been no report of a technique for obtaining single hollow particles when a group-based crosslinkable vinyl monomer is used. The inventor of the present invention has confirmed that it is difficult to obtain single hollow particles when an aromatic crosslinkable vinyl monomer is used.
Japanese Patent Application Laid-Open No. 2006-117920 describes a plurality of hollow particles, but a technique for obtaining single hollow particles when an aromatic crosslinkable vinyl monomer is used is reported. It wasn't.

  Thus, according to the present invention, the hydrophilic (meth) acrylic monomer 40 to 10% by weight and the aromatic monomer 60 to 90% by weight containing at least the crosslinkable styrene monomer, A single hollow particle for light diffusion is provided which is derived from a monomer mixture containing 10% by weight or more of a crosslinkable styrene monomer and has a porosity of 30% or more and an average particle diameter of 3 to 100 μm.

  According to the present invention, single hollow particles having excellent light diffusibility can be provided even when an aromatic crosslinkable vinyl monomer is used. In addition, since the single hollow particles of the present invention are derived from the hydrophilic (meth) acrylic monomer and the aromatic monomer, the excellent weather resistance derived from the (meth) acrylic monomer and the aromatic In addition to having a high refractive index derived from a group vinyl monomer, it has a high light diffusibility derived from being a single hollow. This single hollow particle for light diffusion can be suitably used as a raw material for a TV screen, a lighting cover, a light diffusion plate or a light guide plate of a backlight type liquid crystal display panel, and a paint.

  Further, the hydrophilic (meth) acrylic monomer is methyl acrylate and the following formula 1

(In the formula, R ₁ is H or CH ₃ , R ₂ and R ₃ are different and have ₂ to 5 carbon atoms selected from C ₂ H ₄ , C ₃ H ₆ , C ₄ H ₈ and C ₅ H _10. And m is 0 to 50, n is 0 to 50 (provided that m and n are not 0 at the same time, and R ₄ is H or CH ₃ ).
When it is selected from (meth) acrylic acid esters having an alkylene oxide group represented by the formula (1), it is possible to provide single hollow particles for light diffusion having better light diffusibility.

Furthermore, when the crosslinkable styrene monomer is divinylbenzene or divinylnaphthalene, it is possible to provide single hollow particles for light diffusion having a more excellent light diffusibility.
In addition, when the aromatic monomer contains an aromatic monofunctional vinyl monomer selected from styrene, α-methylstyrene, vinyltoluene and chlorostyrene, a single hollow for light diffusion having better light diffusibility Particles can be provided.

It is a schematic explanatory drawing of the measuring method of a porosity. 2 is an electron micrograph of a cross section of a single hollow particle of Example 1. FIG. 2 is an electron micrograph of a cross section of a single hollow particle of Example 2. FIG. 4 is an electron micrograph of a cross section of a particle of Comparative Example 1. 4 is an electron micrograph of a cross section of a particle of Comparative Example 2.

In the present invention, the “single hollow particle for light diffusion” (hereinafter, also referred to as “single hollow particle”) refers to a substantially spherical particle having a single pore inside. Moreover, the single hollow particle of this invention is equipped with the void | hole a and the polymer layer b, as shown in FIG. In FIG. 1, reference numeral 1 means a single hollow particle.
The single hollow particles are derived from a monomer mixture containing 40 to 10% by weight of a hydrophilic (meth) acrylic monomer and 60 to 90% by weight of an aromatic monomer. Here, the aromatic monomer includes at least a cross-linkable styrene monomer. Further, the crosslinkable styrene monomer is contained in an amount of 10% by weight or more based on the monomer mixture. This single hollow particle is obtained, for example, by subjecting the monomer mixture to suspension polymerization in an aqueous medium in the presence of a surfactant composed of a comb polymer having a hydrophilic part and a hydrophobic part in the molecule. be able to. Here, (meth) acryl means acryl or methacryl.

(Monomer mixture)
(1) Hydrophilic (meth) acrylic monomer As the hydrophilic (meth) acrylic monomer contained in the monomer mixture, a hydrophilic substituent such as an alkyl acrylate, a carboxyl group or a hydroxyl group is used. Examples thereof include (meth) acrylic monomers. For example, methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, t-butyl acrylate, n-octyl acrylate, dodecyl acrylate, 2-acrylate Ethylhexyl, stearyl acrylate, 2-chloroethyl acrylate, phenyl acrylate, methyl α-chloroacrylate, diethylaminoethyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxyethyl methacrylate, methacryl (Meth) acrylic acid derivatives such as acid 2-hydroxypropyl, (meth) acrylic acid esters having acrylic acid, alkylene oxide groups, and the like. Among these, (meth) acrylic acid ester having an alkyl acrylate and / or an alkylene oxide group is particularly preferable. These monomers may be used alone or in combination of two or more.

Compared with alkyl methacrylate, alkyl acrylate has an advantage of relatively high hydrophilicity and easy to obtain single hollow particles. As the alkyl acrylate, methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, t-butyl acrylate and the like are preferable.
Examples of the (meth) acrylic acid ester having an alkylene oxide group include a compound of the following formula 1.

In the formula, R ₁ is H or CH ₃ , and R ₂ and R ₃ are different and have ₂ to 5 carbon atoms selected from C ₂ H ₄ , C ₃ H ₆ , C ₄ H ₈ and C ₅ H ₁₀ . An alkylene group, m is 0 to 50, n is 0 to 50 (where m and n are not 0 at the same time), and R ₄ is H or CH ₃ .
In addition, in the monomer of Formula 1, when m is larger than 50 and when n is larger than 50, the polymerization stability may be lowered and coalescence particles may be generated. A preferable range of m and n is 0 to 30, and a more preferable range of m and n is 0 to 15.

A commercially available product can be used as the (meth) acrylic acid ester having an alkylene oxide group. Examples of commercially available products include the Bremer series manufactured by NOF Corporation. Further, in the Blemmer series, Blemmer 50 PEP-300 (R ₁ is CH ₃ , R ₂ is C ₂ H ₄ , R ₃ is C ₃ H ₆ , m and n are on average m = 3.5 and n = 2.5, R ₄ is H), Blemmer 70PEP-350 (R ₁ is CH ₃ , R ₂ is C ₂ H ₄ , R ₃ is C ₃ H ₆ , m and n are averages A mixture of m = 3.5 and n = 2.5, R ₄ is H), Blemmer PP-1000 (R ₁ is CH ₃ , R ₃ is C ₃ H ₆ , m is 0, n Is a mixture of 4 to 6 on average, R ₄ is H), Blemmer PME-400 (R ₁ is CH ₃ , R ₂ is C ₂ H ₄ , m is a mixture of 9 on average, n is 0 and R ₄ are CH ₃ ).

  The hydrophilic (meth) acrylic monomer is contained in an amount of 40 to 10% by weight based on the total of the hydrophilic (meth) acrylic monomer and the aromatic monomer. When the content is more than 40% by weight, the refractive index of the obtained particles tends to be low. Also, the weather resistance of the single hollow particles tends to be low. When the amount is less than 10% by weight, it is difficult to form a single hollow and tends to be solid particles. A more preferable content of the hydrophilic (meth) acrylic monomer is 10 to 35% by weight.

(2) Aromatic monomer It is preferable that 60-90 weight% of aromatic monomers are contained in a monomer mixture. When it is less than 60% by weight, the refractive index of the obtained single hollow particles tends to be low. When it is more than 90% by weight, it is difficult to form a single hollow, and the weather resistance of the obtained particles tends to be insufficient. The aromatic monomer contains at least a crosslinkable styrene monomer.

The crosslinkable styrenic monomer is contained in an amount of 10% by weight or more based on the monomer mixture. When the content is less than 10% by weight, the porosity of a single hollow tends to be low and multi-hollow particles tend to be mixed. The upper limit of the content of the crosslinkable styrene monomer is 90% by weight which is the upper limit of the content of the aromatic monomer.
As the crosslinkable styrene monomer, one having two or more polymerizable double bonds can be used. For example, divinylbenzene, divinylnaphthalene and derivatives thereof can be mentioned. These monomers may be used alone or in combination of two or more.

The aromatic monomer preferably further contains an aromatic monofunctional vinyl monomer. Examples of the aromatic monofunctional vinyl monomer include styrene, α-methylstyrene, vinyl toluene, and chlorostyrene.
The aromatic monofunctional vinyl monomer is preferably contained in an amount of 30 to 60% by weight based on the monomer mixture. When the aromatic monofunctional vinyl monomer is contained within this range, single hollow particles having a high porosity tend to be obtained.

(3) Other monomers Further, trimethylolpropane triacrylate, ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, decaethylene glycol dimethacrylate, pentadecaethylene glycol dimethacrylate, Pentamethaethylene glycol dimethacrylate, 1,3-butylene dimethacrylate, allyl methacrylate, trimethylolpropane trimethacrylate, pentaerythritol tetramethacrylate, diethylene glycol dimethacrylate, triethylene glycol triacrylate, N , N-divinylaniline, divinyl ether, divinyl sulfite, and other divinyl compounds and trivinyl compounds may be included.

(4) Other Additives The monomer mixture preferably contains a polymerization initiator that accelerates the polymerization of the contained monomers. As the polymerization initiator, a polymerization initiator generally used for suspension polymerization can be used. For example, benzoyl peroxide, lauroyl peroxide, octanoyl peroxide, orthochlorobenzoyl peroxide, orthomethoxybenzoyl peroxide, methyl ethyl ketone peroxide, diisopropyl peroxydicarbonate, cumene hydroperoxide, cyclohexanone peroxide, t-butyl hydroperoxide , Peroxide-based polymerization initiators such as diisopropylbenzene hydroperoxide, 2,2′-azobisisobutyronitrile, 2,2′-azobis (2,4-dimethylvaleronitrile), 2,2′-azobis (2-methylbutyronitrile), 2,2′-azobis (2,3,3-trimethylbutyronitrile), 2,2′-azobis (2-isopropylbutyronitrile), 1,1′-azobis ( Cyclohexane-1-carbonitri ), 2,2′-azobis (4-methoxy-2,4-dimethylvaleronitrile), 2- (carbamoylazo) isobutyronitrile, 4,4′-azobis (4-cyanovaleric acid), dimethyl-2, 2′-Azobisisobutyrate or the like can be used alone or in combination. In addition, benzoyl peroxide, lauroyl peroxide, 2,2′-azobisisobutyronitrile, and 2,2′-azobis (2,4-dimethylvaleronitrile) are easily dissolved in monomers and easy to handle. It is preferable in a certain point. Moreover, although the compounding quantity of the said polymerization initiator is based also on the kind of monomer to be used, it is 0.01-1 weight part with respect to 100 weight part of monomer mixtures normally.

(Surfactant)
The surfactant is a comb polymer having a hydrophilic part and a hydrophobic part in the molecule. Here, the comb polymer means a polymer having a large number of trident branch points in which a linear side chain is bonded to a linear main chain. For example, a shape in which two or more hydrophobic portions are combined in a comb shape on a main chain composed of a hydrophilic portion, or a shape in which two or more hydrophilic portions are combined in a comb shape on a main chain composed of the opposite hydrophobic portion. Can be used. Among these, the polymer having the former shape is preferable from the viewpoint that the aqueous medium for forming a single hollow dispersed in the monomer mixture can be stably held in a granular form. The bond form between the main chain and the side chain is not particularly limited, but is usually a graft bond form.

As a specific comb polymer,
The side chain is two or more carbonyl-C3 to C6 alkyleneoxy chains containing 3 to 80 alkyleneoxy groups and is bonded to the main chain by an amide or salt bridging group;
Examples thereof include a polymer in which the main chain is a chain derived from a reaction product of poly (lower alkylene imine) and polyester having a free carboxylic acid group. Examples of lower alkylene include ethylene, triethylene, and tetraethylene.

Examples of such comb polymers include commercially available comb polymers from the UK company Lubrizol as “Solsperse” series. Specific examples include product numbers 11200, 13240, 13650, 13940, 24000SC, 24000GR, 26000, 28000, 32000, 32500, 32550, 32600, 33000, 34750, 35100, 35200, 36000, 36600, 37500, and the like.
As the comb polymer, one having a weight average molecular weight of 2000 to 100,000 can be used. A more preferred weight average molecular weight is 20000-30000. The weight average molecular weight is a value measured by gel permeation chromatography.

Furthermore, the comb polymer may have a functional group composed of an acid group and / or a functional group composed of a base. A plurality of acid groups and / or bases may be present. Specifically, the acid group may be present so as to give an acid value of 20 to 80. On the other hand, the base may be present so as to give a basicity of 1000 to 2000.
Here, when the acid value is less than 20, it is difficult to form a single hollow and tends to be a multi-hollow particle. When it exceeds 80, polymerization may become unstable, and a granular polymer may not be obtained. The acid value can be measured based on JIS K 0070 as the number of mg of KOH required to neutralize the free carboxylic acid contained in 1 g of the comb polymer.

  On the other hand, when the base number is less than 1000, hollow formation may be difficult. If it exceeds 2000, hollow formation may be difficult. The base number can be measured as the number of mg of potassium hydroxide equivalent to hydrochloric acid required for neutralizing the basic component contained in 1 g of the comb polymer.

  The compounding amount of the comb polymer material is 0.01 to 4 parts by weight with respect to 100 parts by weight of the monomer mixture. When the blending amount is less than 0.01 part by weight, there is a tendency that the polymer particles do not have a single pore inside. Even if the amount exceeds 4 parts by weight, not only the pore formation effect (ease of forming pores) commensurate with the amount is obtained, but also the purity of the polymer derived from the monomer mixture in the polymer particles As a result, the characteristics of the polymer particles may be impaired. A preferable compounding amount is 0.01 to 3 parts by weight.

(Aqueous medium)
The aqueous medium is not particularly limited, and examples thereof include water and a mixture of water and a water-soluble organic solvent (for example, lower alcohols such as methanol and ethanol).
The aqueous medium is usually used in an amount of 150 to 1000 parts by weight with respect to 100 parts by weight of the monomer mixture.
In the aqueous medium, a dispersion stabilizer and a surfactant for the aqueous medium can be blended to stabilize the monomer mixture in an emulsion state in the aqueous medium.

  As the dispersion stabilizer, a dispersion stabilizer generally used for suspension polymerization of monomers can be used. For example, water-soluble polymers such as methyl cellulose, hydroxyethyl cellulose, and polyvinyl alcohol, and poorly water-soluble inorganic salts such as tricalcium phosphate, magnesium hydroxide, magnesium pyrophosphate, barium sulfate, calcium carbonate, and silica can be used.

Among the above dispersion stabilizers, it can be easily removed from the single hollow particles, and the solubility in water at room temperature is high in that the single hollow particles can be polymerized with a narrow particle size distribution as compared with the case of using other dispersion stabilizers. A poorly water-soluble inorganic salt of about 3 mg or less is preferred. In particular, tricalcium phosphate having a solubility of 2.5 mg is suitable.
A dispersion stabilizer can be normally mix | blended with an aqueous medium in the ratio of 0.1-20 weight part with respect to 100 weight part of monomer mixtures.
As the aqueous medium surfactant, an aqueous medium surfactant generally used for suspension polymerization of monomers can be used. Anionic surfactants are preferred in that single hollow particles can be polymerized with a narrow particle size distribution compared to other surfactants.

Examples of the anionic surfactant include sodium dodecyl sulfate, sodium dodecyl benzene sulfonate, sodium polyoxyethylene lauryl ether sulfate, sodium diethyl sulfosuccinate and the like.
The surfactant for an aqueous medium is usually blended in the aqueous medium so as to have a concentration of 0.005 to 0.3% by weight.

(Suspension polymerization)
Single hollow particles are obtained by subjecting the monomer mixture to suspension polymerization in an aqueous medium in the presence of a surfactant composed of the above comb polymer. The monomer mixture constitutes an oil phase and a surfactant composed of comb polymers, and is polymerized in an aqueous medium.
In suspension polymerization, first, an oil phase and an aqueous medium are prepared in a predetermined composition in separate containers.
The oil phase is composed of a monomer mixture containing a hydrophilic (meth) acrylic monomer and a crosslinkable styrene monomer, optionally an aromatic monofunctional vinyl monomer and a polymerization initiator, and a comb polymer. Is obtained by mixing and stirring at a predetermined ratio. The mixing and stirring means used at this time is preferably a mixing and stirring means that is uniform as a whole, and examples thereof include a general mixer and a homogenizer.

A dispersion stabilizer and a surfactant for an aqueous medium are optionally added to the aqueous medium at a predetermined ratio and mixed and stirred. The mixing and stirring means used at this time is preferably a mixing and stirring means that is uniform as a whole, and examples thereof include a general mixer and a homogenizer.
After the preparation of the oil phase and the aqueous medium, the oil phase is added to the aqueous medium, mixed and stirred to obtain a suspension (water phase / oil phase / water phase emulsion). The oil phase constitutes oil droplets, and the water phase emulsion exists in the oil droplets. At this time, by using a homogenizer as the stirring means, the stirring conditions such as the stirring time and the number of revolutions can be changed, and the oil droplet size and other stirring means can be easily prepared. The ability to adjust the oil droplet size means that the size of single hollow particles obtained from the oil droplets can be adjusted.

  Next, while stirring the suspension, heating is performed to polymerize the oil phase to obtain single hollow particles. The suspension may be heated with a heating device such as an autoclave. The obtained single hollow particles may be filtered if necessary, and the filtrated product may be taken out of the aqueous medium by washing with water and drying. Further, if necessary, the dispersion stabilizer may be removed before washing with water.

(Shape of single hollow particles)
The porosity (hollow ratio) of the single hollow particles is 30% or more. The upper limit of the porosity is about 50%. The porosity is preferably 35% or more.
A single hollow particle has an average particle diameter of 3-100 micrometers. Within this range, sufficient light diffusibility can be ensured without using a large amount of single hollow particles. A more preferable average particle diameter is 4 to 50 μm, and a further preferable average particle diameter is 5 to 30 μm.

  The outer shape of the single hollow particle is spherical. Here, the spherical shape does not mean a strictly spherical shape (true spherical shape), but is a term having an extent acceptable in the field. An inner shape (also referred to as a hollow outer shape) where the single hollow particle is in contact with the hollow located inside has a shape along the outer shape of the single hollow particle. The center of the hollow is at the same position as the center of the single hollow particle, but both centers may be positioned somewhat vertically and horizontally.

(Use of single hollow particles)
The single hollow particles of the present invention can be used as raw materials for molding materials and paints, for example.
(1) Molding material Examples of the molding material include molding materials such as a TV screen, a lighting cover, and a light diffusion plate or a light guide plate of a backlight type liquid crystal display panel. Such a molding material can be obtained, for example, by containing single hollow particles in a transparent base resin in a room temperature solid state. As the transparent base resin, polymethyl methacrylate, polystyrene, methyl methacrylate-styrene copolymer, polycarbonate, polyvinyl chloride, norbornene polymer, vinyl alicyclic hydrocarbon polymer and the like are suitable.

Here, when the single hollow particles are obtained using a surfactant made of a comb polymer, bleeding of the surfactant or the like can be suppressed. Bleeding substances usually have a low molecular weight and are easily degraded by heat and light. Therefore, for example, in a molded product obtained by dispersing single hollow particles in a thermoplastic resin and then heat-molding, the bleed material may be yellowed due to deterioration due to heat during molding. . On the other hand, the single hollow particles of the present invention are excellent in that yellowing that occurs in the molded body can be suppressed.
In addition, you may make a molding material contain various compounding agents in the range which does not impair the effect (light diffusibility by a single hollow particle) of this invention. For example, in the case where the light transmission property, diffusivity, etc. are not strongly required, a colorant such as a pigment may be added to the base resin.

The molding material preferably contains 0.1 to 10% by weight of single hollow particles. Within this range, both excellent light diffusion performance and prevention of discoloration such as yellowing can be achieved.
Moreover, when forming a light diffusing plate using the said molding material, content of the single hollow particle with respect to a molding material shall be 0.5 to 7 weight% from the relationship between light-diffusion performance and light transmission performance. It is preferable. When the content of the single hollow particles is less than 0.5% by weight, sufficient light diffusion performance may not be obtained. Even if the content exceeds 7% by weight, it is not only difficult to improve the light diffusion performance but also the light transmission performance may be lowered.

Moreover, when forming a light-guide plate, it is preferable that content of the single hollow particle with respect to a shaping | molding material shall be 0.05 to 0.5 weight% from the relationship between light-diffusion performance and light transmission performance. . When the content of the single hollow particles is less than 0.05% by weight, the light transmittance may be too high and the light diffusion performance required for the light guide plate may not be provided. If the content exceeds 0.5% by weight, the light diffusion performance may become too high and the light guide distance may be shortened.
As a method of obtaining a molded body from a molding material, a base resin and single hollow particles are kneaded using a general resin kneading means such as a uniaxial extruder, a biaxial extruder, etc. Examples thereof include a method of forming into a plate shape via a roll unit, and a method of forming the kneaded product using an injection molding machine, a press molding machine or the like.

(2) Paint The paint containing the single hollow particles of the present invention can be suitably used for a light diffusing paint, a matte paint, and the like. For example, a mixture of single hollow particles having a particle diameter of 3 to 50 μm and a binder can be used for the light diffusing paint and the matte paint. This mixture may contain a solvent. In the light diffusing paint, it is preferable to use a transparent binder. In the matte paint, the binder resin may be transparent or colored. The content of the single hollow particles in the solid component (binder + single hollow particles) in the paint is preferably 5 to 70% by weight in the light diffusing paint, and 10 to 30% by weight in the matte paint. Is preferred.

A paint having a viscosity of 5 to 300 mPa · s is preferable in that the workability of coating can be improved. The viscosity can be measured using a B-type viscometer. For example, a paint kept at 25 ± 2 ° C. It can be determined by measuring at 100 rpm using 4 rotors.
The binder preferably includes, for example, a base resin having adhesiveness, adhesiveness, binding property, and the like that can prevent single hollow particles from falling off the coating film when the coating film is formed. In addition to the base resin, the binder may contain a dispersant that improves the dispersibility of the single hollow particles, a curing agent for the binder resin, a dye, a pigment, and the like.

  As the base resin, for example, thermosetting resins such as phenol resin, resorcin resin, furan resin, melamine resin, polyester resin, polyurethane resin, epoxy resin, silicone resin, polyvinyl acetate, polyvinyl alcohol, polyvinyl chloride, Examples thereof include thermoplastic resins such as polyvinyl butyral, polyacrylic acid ester and nitrocellulose, and elastomers such as butadiene acrylonitrile rubber and chloroprene rubber.

EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not restrict | limited by these Examples. In addition, the average particle diameter of a single hollow particle, the porosity, and the weight average molecular weight of a comb-type polymer are measured with the following method.
(Measurement method of average particle size)
The electrolyte solution is filled in pores having a pore diameter of 50 to 280 μm, the volume is obtained from the change in conductivity of the electrolyte solution when the particles pass through the electrolyte solution, and the average particle diameter is calculated. Specifically, the measured average particle diameter is a volume average particle diameter measured by a Coulter Multisizer II manufactured by Beckman Coulter. In the measurement, calibration is performed using an aperture suitable for the particle diameter of the particle to be measured according to REFERENCE MANUAL FOR THE COULTER MULTISIZER (1987) issued by Coulter Electronics Limited.

  Specifically, 0.1 g of particles and 10 ml of a 0.1% nonionic surfactant solution are put into a commercially available glass test tube, and mixed for 2 seconds with a touch mixer TOUCHMIXER MT-31 manufactured by Yamato Kagaku. Thereafter, the test tube is predispersed for 10 seconds using a ULTRASONIC CLEANER VS-150 manufactured by VervoCrea, a commercially available ultrasonic cleaner. In a beaker filled with ISOTON 2 (manufactured by Beckman Coulter, Inc .: electrolyte for measurement) equipped with the dispersion, drop it with a dropper while gently stirring, and adjust the concentration meter reading on the screen to around 10%. . Next, the aperture size, Current, Gain, and Polarity are input to the Multisizer II body according to REFERENCE MANUAL FOR THE MULTILIZER (1987) issued by Coulter Electronics Limited and measured manually. During the measurement, the beaker is stirred gently to the extent that bubbles do not enter, and the measurement is terminated when 100,000 particles are measured.

(Measurement method of porosity)
The porosity (%) of the single hollow particles is measured as follows. First, a cross section of a single hollow particle is photographed with a 1000 × electron microscope. From the obtained photograph, 10 single hollow particles cut near the center are arbitrarily selected. The outer diameter r1 and inner diameter r2 of each selected single hollow particle are calculated as follows.
Specifically, the major axis L1 of the single hollow particles is measured on the electron micrograph as shown in FIG. Next, a straight line along the major axis is drawn. A perpendicular is drawn from the midpoint A of this straight line, and the length L2 between two intersections where the perpendicular intersects the outer shell of the single hollow particle is measured. The outer diameter r1 of each single hollow particle is an average value of L1 and L2. The inner diameter r2 of each single hollow particle is also measured in the same manner as r1 except that the long diameter of the single hollow particle is the long diameter of the hole and the outer shell of the single hollow particle is the inner wall of the hole. .
From the obtained r1 and r2, the porosity of each single hollow particle is calculated by the following formula. The porosity is an average value of 10 individual porosity.
Porosity (%) = (r2 / r1) ² × 100

(Weight average molecular weight of comb polymer)
The weight average molecular weight (Mw) is measured using GPC (gel permeation chromatography). The measuring method is as follows. In addition, a weight average molecular weight (Mw) means a polystyrene (PS) conversion weight average molecular weight.
A 50 mg sample is dissolved in 10 ml of tetrahydrofuran (THF), filtered through a non-aqueous 0.45 μm chromatographic disk, and measured using a chromatograph. The chromatographic conditions are as follows.

Liquid chromatograph: manufactured by Tosoh Corporation, trade name “Gel Permeation Chromatograph HLC-8020”
Column: manufactured by Tosoh Corporation, trade name “TSKgel GMH-XL-L” φ7.8 mm × 30 cm × 3 series connection Column temperature: 40 ° C.
Carrier gas: Tetrahydrofuran (THF)
Carrier gas flow rate: 0.8ml / min Injection / pump temperature: 35 ℃
Detection: RI
Injection amount: 100 microliters Standard polystyrene for calibration curve: manufactured by Showa Denko KK, trade name “shodex” weight average molecular weight: 1030000 and manufactured by Tosoh Corporation, weight average molecular weight: 5480000, 3840000, 355000, 102000, 37900, 9100, 2630, 870

Example 1
60 parts by weight of styrene as an aromatic monofunctional vinyl monomer, 30 parts by weight of divinylbenzene as a crosslinkable styrene monomer, 10 parts by weight of methyl acrylate as a hydrophilic (meth) acrylic monomer, polymerization A monomer mixture was obtained by mixing 0.4 parts by weight of azobisvaleronitrile as an initiator. By adding 1 part by weight of a surfactant made of comb polymer (Solsperse 26000, weight average molecular weight 26000, acid value 50 ± 4, basicity 1500 ± 150, manufactured by Lubrizol) to this monomer mixture, Obtained.

An aqueous phase was obtained by adding 10 parts by weight of tricalcium phosphate as a dispersion stabilizer and 0.02 part by weight of sodium dodecylbenzenesulfonate as a surfactant to 150 parts by weight of ion-exchanged water.
The mixture obtained by adding the oil phase to the aqueous phase was stirred with a homogenizer at 4000 rpm for 10 minutes. Thereafter, the monomer was polymerized at 60 ° C. for 12 hours to obtain single hollow particles. FIG. 2 shows an electron micrograph of a cross section of a single hollow particle.
5 g of the obtained single hollow particles and 95 g of polymethyl methacrylate resin (Sumitex MG-5, refractive index 1.490) manufactured by Sumitomo Chemical Co., Ltd. were mixed. The resulting mixture is molded at 240 ° C. by an injection molding machine to produce a molded product (illumination cover) having a thickness of 1 mm and a half cylinder shape (φ25 mm × height 520 mm cylinder vertically divided in half). did.
Luminance was measured by replacing the illumination cover of a commercially available fluorescent lamp type LED illumination (CREE, 40W equivalent type) with the illumination cover produced above. The luminance was measured using a luminance meter (CA-1000, manufactured by Konica Minolta) installed 50 cm away from the lighting cover. The measured luminance was 10600 cd / cm ² . Moreover, the LED light source during LED illumination could not be confirmed through the illumination cover, and the illumination cover was able to sufficiently diffuse the light from the LED light source.

Example 2
Single hollow particles were obtained in the same manner as in Example 1 except that 35 parts by weight of styrene and 35 parts by weight of methyl acrylate were used. FIG. 3 shows an electron micrograph of a cross section of a single hollow particle.
The luminance was measured in the same manner as in Example 1 except that the obtained single hollow particles were used. The luminance was 11000 cd / cm ² . Moreover, the LED light source during LED illumination could not be confirmed through the illumination cover, and the illumination cover was able to sufficiently diffuse the light from the LED light source.
Example 3
Example 10 except that 10 parts by weight of methyl acrylate and 60 parts by weight of styrene are 35 parts by weight of (meth) acrylic acid ester (Blenmer 50PEP300 manufactured by NOF Corporation) and 35 parts by weight of styrene having an alkylene oxide group. Single hollow particles were obtained by this method.
The luminance was measured in the same manner as in Example 1 except that the obtained single hollow particles were used. The luminance was 11900 cd / cm ² . Moreover, the LED light source during LED illumination could not be confirmed through the illumination cover, and the illumination cover was able to sufficiently diffuse the light from the LED light source.
Example 4
Single hollow particles were obtained in the same manner as in Example 1 except that 90 parts by weight of divinylbenzene and 10 parts by weight of methyl acrylate were added and styrene was not added.
The luminance was measured in the same manner as in Example 1 except that the obtained single hollow particles were used. The luminance was 12200 cd / cm ² . Moreover, the LED light source during LED illumination could not be confirmed through the illumination cover, and the illumination cover was able to sufficiently diffuse the light from the LED light source.

Comparative Example 1
Particles were obtained in the same manner as in Example 1 except that 70 parts by weight of styrene and 30 parts by weight of divinylbenzene were added, and methyl acrylate was not added. FIG. 4 shows an electron micrograph of the cross section of the particle.
Comparative Example 2
Particles were produced in the same manner as in Example 1 except that 65 parts by weight of styrene, 5 parts by weight of (meth) acrylic acid ester having an alkylene oxide group (Blenmer 50PEP300 manufactured by NOF Corporation) and 30 parts by weight of divinylbenzene were used. Got. FIG. 5 shows an electron micrograph of the cross section of the particle.
Comparative Example 3
Particles were obtained in the same manner as in Example 1 except that 85 parts by weight of styrene, 10 parts by weight of methyl acrylate, and 5 parts by weight of divinylbenzene were used.
Table 1 shows the amount of the surfactant (numerical values are parts by weight), the shape, the porosity, and the average particle size used in the above Examples and Comparative Examples.

Table 1 shows the following.
From the examples and comparative examples, it is understood that single hollow particles having a porosity of 30% can be obtained by adjusting the monomer amount. Single hollow particles are superior in light diffusibility compared to solid particles having no hollow or multi-hollow particles.
From Examples 1-3 and Example 4, it turns out that a single hollow particle with a higher porosity is obtained by including an aromatic monofunctional vinyl monomer.

a hole b polymer layer 1 single hollow particle A midpoint L1 major axis L2 length between intersections

Claims (6)

  40 to 10% by weight of a hydrophilic (meth) acrylic monomer and 60 to 90% by weight of an aromatic monomer containing at least a crosslinkable styrene monomer, and the crosslinkable styrene monomer A single hollow particle for light diffusion having a porosity of 30% or more and an average particle diameter of 3 to 100 μm, derived from a monomer mixture containing 10% by weight or more. The hydrophilic (meth) acrylic monomer is methyl acrylate and the following formula 1
(In the formula, R ₁ is H or CH ₃ , R ₂ and R ₃ are different and have ₂ to 5 carbon atoms selected from C ₂ H ₄ , C ₃ H ₆ , C ₄ H ₈ and C ₅ H _10. And m is 0 to 50, n is 0 to 50 (provided that m and n are not 0 at the same time, and R ₄ is H or CH ₃ ).
The single hollow particle for light diffusion of Claim 1 selected from the (meth) acrylic acid ester which has the alkylene oxide group represented by these. The single hollow particle for light diffusion according to claim 1 or 2 , wherein the crosslinkable styrene monomer is divinylbenzene or divinylnaphthalene. The aromatic monomer is styrene, alpha-methyl styrene, the light diffusion according to any one of claims 1 to 3 comprising an aromatic monofunctional vinyl monomer is selected from vinyl toluene and chlorostyrene Single hollow particle. The light diffusion according to any one of claims 1 to 4, wherein the single hollow particle for light diffusion is used as a raw material for an illumination cover, a light diffusion plate or a light guide plate of a backlight type liquid crystal display panel, or a paint. Single hollow particle. An illumination cover comprising a single hollow particle for light diffusion according to any one of claims 1 to 5 blended in a transparent resin.