WO2008010552A1

WO2008010552A1 - Styrene resin composition and molded body

Info

Publication number: WO2008010552A1
Application number: PCT/JP2007/064267
Authority: WO
Inventors: Shintaro Watanabe; Takeshi Yamada; Jun Takahashi
Original assignee: Denki Kagaku Kogyo Kabushiki Kaisha
Priority date: 2006-07-19
Filing date: 2007-07-19
Publication date: 2008-01-24
Also published as: TW200819295A; TWI391244B; CN101489785A; KR20090031426A; JPWO2008010552A1

Abstract

Disclosed is a light diffusing sheet excellent in dimensional stability, light resistance, optical characteristics and antistatic properties. Specifically disclosed is a multilayer sheet excellent in dimensional stability, light resistance, light diffusion and antistatic properties, wherein an intermediate layer is composed of a resin composition containing a copolymer mainly composed of 50-100% by mass of a styrene monomer unit and 50-0% by mass of a (meth)acrylic acid monomer unit, and a specific unmelted compound, and front and back layers are composed of a resin composition containing a copolymer mainly composed of 20-50% by mass of a styrene monomer unit and 80-50% by mass of a (meth)acrylate ester monomer unit, a specific unmelted compound and a specific light resistant agent.

Description

Specification

Styrenic resin composition and molded body

Technical field

The present invention relates to a multilayer sheet excellent in light diffusibility, dimensional stability, light resistance, and antistatic properties. In particular, the present invention relates to a light diffusing sheet used as a light diffusing plate for a transmissive screen of a screen such as a projection television or a liquid crystal television.

Background art

[0002] A screen lens such as a transmissive screen used in projection televisions projects an image on the screen and displays the image. Since this screen lens is desired to be bright and have a wide viewing angle for the observer, it generally has a configuration in which a lens molding such as a lenticular lens or a Fresnel lens is combined! For these lens molded bodies, methacrylic resins having excellent transparency, light resistance, scratch resistance, molding processability, etc. are widely used. These molded bodies are produced by press molding, extrusion molding, cast molding, injection molding, etc. Generally molded.

[0003] Since the methacrylic resin used in such a screen lens has a high water absorption rate, the dimensional change of the molded body for the screen lens occurs, the screen warps and floats, the optical properties are impaired, and the frame body There was a problem that the screen lens would fall off. In addition, there has been a problem that the screen lens is deformed when the temperature at the time of transportation or the environment temperature of use becomes high.

[0004] In order to solve these problems, Patent Document 1 describes a mixture of an aromatic butyl monomer, a (meth) acrylic acid ester monomer, and a polyfunctional unsaturated monomer. A method for obtaining a Fresnel lens by dissolving and polymerizing a styrene-gen copolymer is disclosed. However, this technique is insufficient to obtain a molded article for a screen lens having an excellent light diffusibility.

In addition, methacrylic resin used as a base material for the light diffusing plate of liquid crystal televisions has a high water absorption rate, which causes a change in the dimensions of the light diffusing plate molding, warping of the light diffusing plate, It had a problem that its characteristics were impaired. Also, if the image or lamp light is irradiated for a long time, Discoloration occurred due to deterioration of the resin used for the lean lens and the light diffusion plate, and the image was discolored.

Patent Document 1: Japanese Patent Laid-Open No. 5-341101

Disclosure of the invention

Problems to be solved by the invention

[0006] An object of the present invention is to use a multilayer sheet excellent in dimensional stability, light resistance, light diffusibility and antistatic property, particularly as a light diffusion sheet such as a molded product for a screen lens or a molded product for a light diffusion plate. Is to provide a multilayer sheet.

Means for solving the problem

[0007] As a result of intensive studies to solve the above problems, the present inventors have found that a copolymer mainly composed of a styrene monomer unit and a (meth) acrylate monomer unit and a specific unmelted unit. A resin composition containing a compound as an intermediate layer, a copolymer mainly composed of a styrene monomer unit and a (meth) acrylate ester monomer unit, a specific unmelted compound and a specific compound It has been found that a multilayer sheet excellent in dimensional stability, light resistance, light diffusibility, and antistatic property can be obtained by using a resin composition containing a light resistance agent as a front layer and a back layer, and the present invention has been achieved. It is a thing.

That is, the present invention has the following gist.

(1) A light diffusing sheet having a multilayer structure, wherein the surface layer a and the back layer c are composed of the following component (A), and the intermediate layer b is composed of the component (B).

Component (A): 20 to 50% by mass of a styrene monomer unit and 80 to 50% by mass of a (meth) acrylate monomer unit and 100 parts by mass of a styrene copolymer. The difference in refractive index from the copolymer is within 0.005, the average particle size is 5 to; 15 m of unmelted compound;! To 10 parts by mass, and the hindered amine compound is 0.; A styrene-based resin composition containing 0.;! To 2 parts by mass of a benzotriazole compound and 0.; to 3 parts by mass of an amine surfactant.

Component (B): Styrenic monomer unit 50 to 100% by mass and (meth) acrylic acid ester monomer unit 50 to 0% by mass of styrene copolymer 100 parts by mass Undissolved with a refractive index difference of 0.55-0.15 and an average particle size of 2-10111 A styrenic resin composition comprising a melt compound;! -10 mass parts.

(2) The above (1), wherein the unmelted compound contained in component (A) is a cross-linked copolymer containing a styrene monomer and a (meth) acrylate monomer as monomer units. A multilayer sheet as described in 1.

(3) The unmelted compound contained in the component (B) is a cross-linked polymer containing a (meth) acrylic acid ester monomer as a monomer unit, as described in (1) or (2) above Multi-layer sheet.

(4) The multilayer sheet according to any one of the above (1) to (3), which is hindered amine compound strength S and bis (2, 2, 6, 6 tetramethyl-4-piperidyl) sebacate.

(5) Benzotriazole-based compound strength 2- (2H benzotriazole-2-yl) 4 (1, 1, 3, 3-tetramethylbutyl) Any of the above (1) to (4) which is phenol The multilayer sheet described in 1.

(6) The multilayer sheet according to any one of the above (1) to (5), wherein the amine surfactant is N hydroxyethyl-N— (2 hydroxyalkyl) amine.

(7) The above, wherein at least one of the component (A) and the component (B) further contains 0.0005 to 0.5 parts by mass of a benzoxazole compound with respect to 100 parts by mass of the styrene copolymer. (1) to (6)! / A multilayer sheet according to any one of the above.

(8) The multilayer sheet according to the above (7), which is benzoxazole-based compound strength S, 2,5 thiophendinole (5-t butynole 1,3-benzoxazole).

(9) In the multi-layer structure, the thickness of the surface layer a and the back layer c is 0.005 to 0.5 mm, and the thickness of the intermediate layer is !! to 7 mm. The multilayer sheet as described.

(10) The multilayer sheet according to any one of the above (1) to (9) obtained by simultaneously extruding the surface layer a, the intermediate layer b, and the back layer c.

(11) A light diffusion sheet using the multilayer sheet according to any one of (1) to (; 10) above.

The invention's effect

[0009] The light diffusion sheet obtained by the present invention is excellent in optical properties, dimensional stability, light resistance, and antistatic properties, and therefore can be suitably used for optical display applications.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the present invention will be described in detail. Examples of the styrenic monomer used in the present invention include styrene, α-methylstyrene, ρ-methylstyrene, p-t-butylstyrene, and the like, and preferably styrene.

[0011] Examples of the (meth) acrylic acid ester monomer in the present invention include methyl methacrylate, ethyl methacrylate, methyl acrylate, ethyl acrylate, n-butyl acrylate, 2-methyl hexyl. Examples include attalylate, 2-ethylhexyl acrylate, octinore acrylate. These may be used alone or in combination of two or more. Preference is given to methyl methacrylate, ethyl acetate or n-butyl methacrylate, or mixtures thereof.

[0012] The styrene copolymer in the component (A) used for the surface layer and the back layer of the present invention is 20 to 50% by mass, preferably 35 to 50% by mass, and a styrene monomer unit. meth) acrylic acid ester monomer units 80-50 mass ^_0/0, preferably from 65 to 50 weight ^_0/0, consists. If the styrene monomer unit is less than 20% by mass, the resulting light diffusion sheet may be warped due to moisture absorption, and if it exceeds 50% by mass, the light resistance may be lowered and the light may be discolored by light irradiation.

[0013] The styrene copolymer in the component (B) used in the intermediate layer of the present invention is a styrene monomer unit of 50 to; 100% by mass, preferably 70 to 100% by mass, and (meth) acrylic acid ester ether-based monomer unit 50 to 0 mass ^_0/0, preferably from 30 to 0 mass ^_0/0, consists. If the styrene monomer unit is less than 50% by mass, it may be deformed by moisture absorption.

[0014] The styrene copolymer in the component (B) used in the intermediate layer of the present invention can be copolymerized with these in addition to the styrene monomer and the (meth) acrylate monomer. The amount of the bulle monomer that may be copolymerized is preferably 10 parts by mass or less with respect to 100 parts by mass of the total amount of the styrene monomer and the (meth) acrylate monomer. Examples of the copolymerizable bur monomer include cyanated butyl monomers such as acrylonitrile and methacrylonitrile; methacrylic acid, acrylic acid, maleic anhydride, maleic acid, itaconic acid, hydrous itaconic acid Unsaturated carboxylic acid monomers such as maleimide, maleimide monomers such as N-methylmaleimide, N-phenylmaleimide and the like. These may be used alone or in combination of two or more.

[0015] The unmelted compound in component (A) has a melting point or softness above 200 ° C under an atmosphere of 1 atm. Compounds having a conversion point are preferred. When the melting point and softening point are less than 200 ° C, when the compound is melted and kneaded with a styrenic copolymer or when a styrenic resin composition is formed into a sheet, the compound does not readily retain excellent optical properties. There is. The refractive index difference between the styrene copolymer and the unmelted compound in the component (A) is within 0.005, preferably within 0.003. When the difference in refractive index exceeds 0.005, the total light transmittance and light diffusivity decrease. In addition, the average particle size of the unmelted compound is !!-15 m, preferably 5-14 m. When the average particle diameter is less than 1 μm, the haze and diffusivity decrease and the light diffusivity decreases. When the average particle diameter exceeds 15 m, the total light transmittance decreases. The average particle size of the unmelted compound is a value obtained by measurement using a Coulter Multisizer (manufactured by Beckman Coulter). The measurement is performed by the laser diffraction light scattering method, water is used as the solvent, the sample is dispersed for 1 minute using a homogenizer with an output of 200 W, and the concentration of PIDS (Polarization Intensity Differential Scattering) is 45-55%. The water refractive index was measured at 1.33, and the average particle diameter was calculated from the volume distribution.

It is necessary that the unmelted compound is contained in an amount of! To 10 parts by mass, preferably 2 to 9 parts by mass with respect to 100 parts by mass of the styrene copolymer in the component (A). If the content of the unmelted compound is less than 1 part by mass, the haze and diffusivity become small and the light diffusibility decreases, and if it exceeds 10 parts by mass, the total light transmittance tends to decrease. The unmelted compound in component (A) is not particularly limited, but a cross-linked copolymer containing a styrene monomer and a (meth) acrylic acid ester monomer as monomer units is used. preferable.

The styrene monomer is, for example, styrene, α-methylstyrene, ρ-methylstyrene, p-t-butylstyrene, or the like, and preferably styrene. The (meth) acrylic acid ester-based monomer is, for example, methyl methacrylate, ethyl methacrylate, methyl acrylate, or the like, preferably methyl methacrylate.

In component (A), hindered amine compound 0.;! ~ 2 parts by mass, preferably 0.2 ~; 1.2 parts by mass and benzotriazole based on 100 parts by mass of styrene copolymer ! ~ 2 parts by weight, preferably 0.2 ~; 1. It is necessary to contain 2 parts by weight.

The hindered amine compound and the benzotriazole compound strength are each less than 0.1 parts by mass, the light resistance is lowered, and when more than 2 parts by mass, the yellowness of the obtained light diffusion sheet is reduced. There is a tendency to become stronger.

Hindered amine compounds are amamine-based photostabilizers such as bis (2, 2, 6, 6-tetramethyl-1 (octyloxy) 4-piperidinyl) ester, bis (1, 2, 2) decanoate. , 6, 6 Pentamethylolyl 4-piperidyl) [[3,5 Bis (1,1-dimethylolethyl) -4-hydroxyphenenole] methinole] butyl malonate, bis (1,2,2,6,6-pentamethyl-4-piperidyl ) Sebacate, methyl 1, 2, 2, 6, 6 pentamethyl-4-piperidyl sebacate, bis (2, 2, 6, 6 tetramethyl-4-piperidyl) sebacate, etc. These may be used alone or in combination of two or more. Benzotriazole compounds are ultraviolet absorbers such as 2- (2H-benzotriazole-2-yl) p cresol, 2- (2H-benzotriazole-2-yl). 4-6 Bis (1-methyl 1-phenoletinole) phenol, 2- [5 Black (2H) monobenzotriazole-2-yl] -4 Methyl] -6- (tbutinole) phenol, 2 , 4-di-tert-butyl-6- (5 benzophenazol-2-inole) phenol, 2 1 (2H benzotriazole-2-yl) 4, 6 di-pentylphenol, 2- (2H Benzotriazole 2yl) 4- (1,1,3,3 tetramethylbutynole) phenol and the like. These may be used alone or in combination of two or more.

In the present invention, component (A) contains 0.0;! To 3 parts by mass, preferably 0.;! To 2.5 parts by mass, with respect to 100 parts by mass of the styrene copolymer. It is necessary to contain an amine surfactant. If the amount of the amine-based surfactant is less than 0.01 parts by mass, the antistatic property may not be sufficient. If the amount exceeds 3 parts by mass, the resulting resin composition or molded article may be discolored.

Examples of amine surfactants include alkyl diethanolamine, polyoxyethylene alkylamine, alkyldiethanolamide, polyoxyethylene alkylamide, N hydroxyethyl N- (2-hydroxyalkyl) amine, and the like. Can be used alone or in combination of two or more.

In the present invention, at least one of the component (A) and the component (B) is preferably a benzoxazole-based compound which is a colorant and is a so-called optical brightener. Five It is desirable to contain part by mass, more preferably 0.0008-0. When the content of the benzoxazole-based compound in at least one component is 0.0005 parts by mass or more, the yellowness of the resulting multilayer sheet is reduced and the appearance is improved as compared to less than 0.005 parts by mass. At the same time, the total light transmittance of the resulting multilayer sheet tends to increase, which is preferable. The amount of 0.5 parts by mass or less is preferable because the light resistance of the resulting multilayer sheet is improved as compared with the case of exceeding 0.5 parts by mass.

Examples of the benzoxazole-based compounds include 2,5-thiophenzyl (5-tert chinoleyl 1,3-benzoxazonole, 2,5-thiophenzinore (5-tert-butynole 1,5-benzoxazole 10 % And dicyclohexyl phthalate 90%, 4,4'-bis (benzoxazol 2-yl) stilbene, etc., which may be used alone or in combination. .

The unmelted compound used for component (B) is preferably a compound having a melting point or softening point at 200 ° C. or higher under an atmosphere of 1 atm. When the melting point and softening point are less than 200 ° C, the unmelted compound melts at the time of melt-kneading with the styrene-based copolymer or when the styrene-based resin composition is formed into a sheet, so that excellent optical characteristics can be maintained immediately. There are cases where it is not possible. The difference in refractive index between the styrene copolymer and the unmelted compound in component (B) is 0.05 to 0.15, preferably 0.07 to 0.13. If the difference in refractive index is less than 0.05, the haze and diffusivity of the resulting light diffusion sheet will be small and the light diffusivity will be reduced, and if it exceeds 0.15, the total light transmittance and light diffusivity will be reduced. Further, the average particle diameter of the unmelted compound is 2 to 10111, preferably 3 to 9. When the average particle size of the unmelted compound is less than 2 in, the resulting light diffusion sheet has a low haze and light diffusibility, and when it exceeds 10 m, the total light transmittance decreases. The average particle size of the unmelted compound is a value obtained by measurement using a Coulter Multisizer (Beckman Coulter, Inc.). The measurement is performed by the laser diffraction light scattering method. Water is used as the solvent, and the sample is dispersed for 1 minute using a homogenizer with an output of 200 W, and the PIDS (Polarization Intensity Differential Scattering) concentration is adjusted to 45-55%. Adjustment, measurement was made with a water refractive index of 1.33, and the average particle diameter was calculated from the volumetric cloth.

The unmelted compound is based on 100 parts by mass of the styrene copolymer in the component (B); It is necessary to contain 10 parts by mass, preferably 2 to 9 parts by mass. When the content of unmelted compound is less than part by mass, the resulting light diffusion sheet has a low haze and light diffusibility, and when it exceeds 10 parts by mass, the total light transmittance decreases. The unmelted compound in the component (B) is not particularly limited, but a cross-linked copolymer mainly composed of a (meth) acrylic acid ester monomer is preferable. The (meth) acrylic acid ester-based monomer is, for example, methyl methacrylate, ethyl methacrylate, methyl acrylate, or the like, preferably methyl methacrylate.

[0020] The method for producing the styrene copolymer in component (A) and the styrene copolymer in component (B) is not particularly limited, but bulk polymerization, suspension polymerization, solution polymerization, emulsification A polymerization method can be suitably employed.

[0021] There are no particular restrictions on the blending method of each material of component (A) and component (B), a method of blending each styrene copolymer before, during, and immediately after polymerization, and a separated styrene copolymer. Examples include a method of blending with a polymer by melt mixing.

[0022] Even when each styrene copolymer is pelletized and then melted and mixed with an unmelted compound, the mixing method is not particularly limited. For example, a known mixing apparatus such as a Henschel mixer or a tumbler mixer may be used. After the preliminary mixing, the mixture can be uniformly mixed by melt kneading using an extruder such as a single screw extruder or a twin screw extruder. In addition, a high-concentration mixture in which an unmelted compound is mixed at a high concentration with a styrenic copolymer is prepared, and this high-concentration mixture and a styrene-based copolymer are dry blended during the manufacture of a light diffusion sheet. A material in which the content of the unmelted compound becomes a specified concentration may be used as a raw material.

[0023] An additive may be blended with the styrenic copolymer in the component (A) and the styrenic copolymer in the component (B), if necessary. For example, plasticizers, lubricants, silicone oils and the like can be blended to improve fluidity and releasability. In addition, a heat stabilizer can be blended in order to impart further heat stability. In addition, a colorant can be added.

[0024] The light diffusing sheet of the present invention has a multilayer structure, and the thickness of each layer is such that the surface layer a and the back layer c comprising the component (A) are 0.005 to 0.5 mm, preferably 0.03. 0.2mm, (B) component The intermediate layer b, which is also a force, is preferably! To 7 mm, more preferably 1.2 to 2.5 mm. If the surface layer a and the back layer c are less than 0.005 mm, the resulting light diffusion sheet may be discolored by light irradiation, and if it exceeds 0.5 mm, it may be deformed by moisture absorption. Also, if the intermediate layer b is less than lmm or more than 7mm, excellent optical characteristics may not be obtained.

[0025] The light diffusing sheet may be a sheet obtained by extruding the surface layer a, the intermediate layer b, and the back layer c separately by heat fusion or the like, and a T-die using a feed block. Alternatively, extrusion may be performed simultaneously using a multi-hold die. The power of the latter method is not only economically advantageous, but it is also advantageous in terms of quality, if it is easy to prevent scratches and foreign matter from entering the sheet surface during lamination.

Example

[0026] Hereinafter, the present invention will be specifically described by way of examples. However, the present invention should not be construed as being limited to these examples.

[0027] Method for producing styrene-based copolymer

The tanks used for the production were the first and second devolatilization tanks, each of which has a first complete mixing tank with a capacity of about 5L and a second complete mixing tank with a capacity of about 15L connected directly to IJ and equipped with a preheater. Two units were connected in series.

Further, styrene 10 parts by mass ^_0/0, with respect to the monomer solution 10 0 parts by mass composed of methyl methacrylate Tari rate 90 mass%, Echirubenzen 15 parts by weight, t-butyl peroxide O carboxymethyl isopropyl monocarbonate 0.01 parts by weight of 2 , 4 Diphenyl nitro 4 Methyl-1-pentene 0.2 parts by mass was mixed to prepare a raw material solution. This raw material solution was supplied to the first complete mixing tank controlled at 135 ° C at 6. Okg per hour. The conversion rate at the outlet of the first complete mixing tank was 28% by mass. Next, it was continuously extracted from the first complete mixing tank and supplied to the second complete mixing tank controlled at 135 ° C. The conversion rate at the outlet of the second complete mixing tank was 63%. Next, it was continuously extracted from the second complete mixing tank, heated by a preheater, and introduced into the first devolatilization tank controlled at 67 kPa and 160 ° C. Furthermore, it was continuously extracted from the first devolatilization tank, heated with a preheater, and introduced into the second devolatilization tank controlled at 1.3 kPa and 230 ° C to remove the monomer. This was extruded and cut into strands to obtain pellet-shaped styrene copolymer (A-1). [0028] Styrene 40 wt ^_0/0, except for using a monomer solution composed of methyl methacrylate Tari rate 60 mass ^_0/0, (A- 1) and was conducted in the same manner, a styrene-based copolymer (A -2) was obtained.

[0029] Styrene 80 wt ^_0/0, except for using a monomer solution composed of methyl methacrylate Tari rate 20 mass%, was carried out in the same manner as (A- 1), a styrene-based copolymer (A-3 )

[0030] Styrene 100 mass ^_0/0, except for using a monomer solution composed of 0% by weight of methyl meth Tari rate, (A- 1) carried out in the same manner as with styrene copolymer (A- 4) Got.

[0031] Polyorganosiloxane cross-linked beads which are unmelted compounds (B)

As an unmelted compound, polyorganosiloxane cross-linked beads (average particle diameter 6 m, refractive index 1.420, Toshiba Silicone Tospearl 2000B) were used.

[0032] Manufacturing method of unmelted MMA—nBA copolymer crosslinked beads (C)

In an autoclave equipped with a stirrer, 20 parts by mass of methyl methacrylate, 80 parts by mass of n-butyl acrylate, 5 parts by mass of dibutene benzene as a crosslinking agent, 0.2 part by mass of benzoyl peroxide as a polymerization initiator, and dodecyl as a suspension stabilizer Sodium benzenesulfonate (0.001 part by mass), tribasic calcium phosphate (0.5 part by mass) and pure water (200 parts by mass) were charged and polymerized at a temperature of 95 ° C for 6 hours and further at a temperature of 130 ° C for 2 hours. After completion of the reaction, washing, dehydration and drying were performed to obtain crosslinked beads (C). The average particle size of the crosslinked beads (C) of the unmelted compound (C) was 4 mm, and the refractive index was 1.460.

[0033] Method for producing unmelted styrene MMA crosslinked beads (D)

In an autoclave equipped with a stirrer, 40 parts by mass of styrene, 60 parts by mass of methyl methacrylate, 5 parts by mass of dibutenebenzene as a crosslinking agent, 0.2 part by mass of benzoyl peroxide as a polymerization initiator, and dodecylbenzenesulfone as a suspension stabilizer Sodium oxalate (0.001 parts by mass), tribasic calcium phosphate (0.5 parts by mass) and pure water (200 parts by mass) were charged, and polymerization was carried out at a temperature of 95 ° C for 6 hours and further at a temperature of 130 ° C for 2 hours. After completion of the reaction, washing, dehydration and drying were performed to obtain crosslinked beads (D-1). The average particle diameter of (D-1) was 8111, and the refractive index was 1.535.

A crosslinked bead (D-2) having an average particle diameter of 3111 and a refractive index of 1.535 was obtained by the same production method as (D-1) except that 1.0 part by mass of tribasic calcium phosphate was used.

In addition, according to the same production method as (D-1) except that 0.2 parts by mass of tricalcium phosphate was used. Crosslinked beads (D-3) having an average particle diameter of 13 m and a refractive index of 1.535 were obtained.

Further, a crosslinked bead (D-4) having an average particle diameter of 18 m and a refractive index of 1.535 was obtained by the same production method as (D-1) except that 0.1 part by mass of tricalcium phosphate was used.

[0034] Method for producing unmelted PMMA cross-linked beads (E)

100 parts by weight of methyl methacrylate in an autoclave equipped with a stirrer, 5 parts by weight of dibule benzene as a crosslinking agent, 0.2 part by weight of benzoyl peroxide as a polymerization initiator, 0.001 part by weight of sodium dodecylbenzenesulfonate as a suspension stabilizer And 0.5 parts by mass of tertiary phosphate power and 200 parts by mass of pure water were polymerized at a temperature of 95 ° C for 6 hours and further at a temperature of 130 ° C for 2 hours. After completion of the reaction, washing, dehydration and drying were performed to obtain crosslinked beads (E-1). The average particle size of (£ -1) was 8111, and the refractive index was 1.494.

A crosslinked bead (E-2) having an average particle diameter of 1111, and a refractive index of 1.494 was obtained by the same production method as (E-1) except that 1.5 parts by mass of tribasic calcium phosphate was used.

Further, a crosslinked bead (E-3) having an average particle diameter of 3111 and a refractive index of 1.494 was obtained by the same production method as (E-1) except that 1.0 part by mass of tricalcium phosphate was used.

Further, a crosslinked bead (E-4) having an average particle diameter of 13 m and a refractive index of 1.494 was obtained by the same production method as (E-1) except that 0.2 part by mass of tricalcium phosphate was used.

[0035] Colorant (F)

As a colorant, fluorescent whitening agent 2, 5-thiophenzyl (5-tert-butyl-1,3-benzoxazole) (Ciba Specialty Chemicals' Ubitex OB) (F-l), resin colorant Mitsubishi Chemical Dairesin BLUE J (F-2) manufactured by Daikin was used.

[0036] Styrene copolymers (A— ;!) to (A-4), crosslinked beads B, C, (D— ;!) to (D-4), (E— ;!) to (E— 4) Bis (2, 2, 6, 6-tetramethyl-4-piperidyl) sebacate as a hindered amine compound, 2- (2H-Benzotriazole-2-yl) -4, 6-di- as a benzotriazole compound t-Pentylphenol, N-hydroxyethyl-N- (2-hydroxyalkyl) amine as amine surfactant, (F-l) and (F-2) as colorants, the mixing ratio shown in Tables 2 and 3 And mixed. The obtained mixture was kneaded with a 40 mm diameter single screw extruder at a temperature of 240 ° C. and a screw rotation speed of lOO rpm, pelletized, and styrene resin compositions 1 to 36 shown in Tables 2 and 3 were used. Pellets were obtained. [0037] Examples;! To 13, Comparative examples;! To 26

Using the styrenic resin compositions 1 to 36, a light diffusion sheet having a three-layer structure shown in Tables 4 to 8 was prepared using a T-die type multilayer extruder having a feed block. The multi-layer extruder consists of a single 65mmφ full flight screw single screw extruder for the intermediate layer and a single 30mm mφ full flight screw single screw extruder for the front and back layers. A test extruder was used in which the feed blocks were joined and multilayered. Each cylinder temperature for sheeting was operated and molded at 230 ° C.

The optical properties, light resistance, water absorption warpage and antistatic properties of the obtained light diffusion sheet were evaluated, and the data are shown in Tables 4-8.

If the haze is 99% or more, the total light transmittance is 65% or more, the diffusivity is 17% or more, the b value indicating yellowness is less than ^, and the light resistance is less than the color difference ΔΕvalue, it can be judged that the optical characteristics are good. . In order to achieve excellent dimensional stability, the water absorption warpage must be less than 1 mm, and in order to exhibit excellent antistatic properties, the surface resistivity must be 10 ¹² Ω or less.

[0038] [Table 1]

table 1

[0039] [Table 2]

table

Table 3

Table 4

Table 5

聖 [Holy

丽 D¾ Table 6

Table 7

Each measuring method of the obtained light diffusion sheet is as follows.

(1) Total light transmittance and haze: Measured according to ASTM D-1003 using a HAZE meter (NDH-2000) manufactured by Nippon Denshoku Industries Co., Ltd.

(2) Diffusivity: Using a variable angle photometer (GC5000L) manufactured by Nippon Denshoku Industries Co., Ltd., measure light transmittance I at a light receiving angle of 0 ° and light transmittance I at a light receiving angle of 70 °, and calculate using the following formula. did.

0 70

Diffusion rate (%) = (1 70 Λ 0) x ioo

(3) Light resistance: The color difference ΔΕ after 400Hr irradiation was measured using a Xenon Weatherometer manufactured by Toyo Seiki Seisakusho, Atlas CI65A. (4) Dimensional stability (water absorption warpage): A light diffusion sheet cut to a size of 180mm x 180mm is left in an atmosphere of 50 ° C and 80% humidity for 7 days, and the amount of deformation at the four corners before and after leaving is measured with calipers. The average value was taken as the value of water absorption warpage, and this value was taken as a measure of dimensional stability.

(5) Yellowness and color difference: L, a, and b were measured using a color difference meter (∑-80) manufactured by Nippon Denshoku Industries Co., Ltd., and b value was shown as a measure of yellowness. Further, the color difference ΔΕ in light resistance evaluation was obtained by the following equation.

AE = ((LL ') ² + (aa') ² + (bb ') ² ) ^1/2

However, L, a, b are hues before light resistance evaluation, and L ′, a ′, b ′ are hues after light resistance evaluation (after 400Hr irradiation).

(6) Antistatic property: The surface resistivity of the molded product, which was conditioned for 24 hours at a temperature of 23 ° C and humidity of 50% RH in accordance with JIS K-6911, was measured using a surface resistivity measuring machine manufactured by KAWAGUCHI (R503 ) And this value was taken as a measure of antistatic properties.

[0047] Evaluations other than the light diffusion sheet were performed as follows.

(7) Refractive index: The unmelted compound was measured with an Abbe refractometer in an atmosphere having a wavelength of 589 nm and 23 ° C. The styrene copolymer was measured at a temperature of 25 ° C. using a digital refractometer (RX-2000, manufactured by ATAGO) using a saturated aqueous solution of potassium iodide as a contact liquid.

(8) Resin composition of styrene copolymer: Dissolve styrene copolymer in deuterated form to prepare 2% solution and use FT-NMR (FX-90Q type, manufactured by JEOL Ltd.) as measurement data. Was measured using C and calculated from the peak areas of styrene and methyl methacrylate.

Industrial applicability

[0048] The multilayer sheet of the present invention is excellent in dimensional stability, light resistance, light diffusibility, and antistatic properties, and is particularly useful as a transmissive screen for screens such as projection televisions and a light diffusing plate for liquid crystal televisions. It should be noted that the entire contents of the specification, claims, and abstract of Japanese Patent Application No. 2006-196541 filed on July 19, 2006 are cited herein as the disclosure of the specification of the present invention. Incorporate.

Claims

The scope of the claims

[1] A multi-layered light diffusion sheet, wherein the surface layer a and the back layer c are composed of the following component (A), and the intermediate layer is composed of the component (B).

Component (B): Styrenic monomer unit 50 to 100% by mass and (meth) acrylic acid ester monomer unit 50 to 0% by mass of styrene copolymer 100 parts by mass A styrenic resin composition comprising:! To 10 parts by mass of an insoluble compound having a refractive index difference of 0.05 to 0.15 and an average particle size of 2 to 10 111 with respect to a tylene copolymer.

[2] The unmelted compound contained in the component (A) is a cross-linked copolymer containing a styrene monomer and a (meth) acrylate monomer as monomer units. Multilayer sheet.

[3] The unmelted compound contained in the component (B) is a cross-linked polymer containing a (meth) acrylic acid ester monomer as a monomer unit. Multi-layer sheet.

[4] The multilayer sheet according to any one of claims 1 to 3, wherein the hindered amine compound strength is bis (2, 2, 6, 6 tetramethyl-4-piperidyl) sebacate.

[5] Strength of benzotriazole compounds 2— (2H—Benzotriazole-2-yl) -4 (1

, 1, 3, 3-tetramethylbutyl) phenol. The multilayer sheet according to any one of claims 1 to 4.

[6] The multilayer sheet according to any one of [1] to [5], wherein the amine surfactant is N-hydroxyethyl-N- (2 hydroxyalkyl) amine.

[7] At least one of the component (A) and the component (B) is added to 100 parts by mass of the styrene copolymer.

And further containing 0.0005 to 0.5 parts by mass of a benzoxazole-based compound;

6! /, A multilayer sheet according to one of the slippages.

[8] The multilayer sheet according to claim 7, which is benzoxazole-based compound strength S, 2,5-thiophenzyl (5-t-butyl-1,3-benzoxazole).

[9] In the multilayer structure, the thickness of the surface layer a and the back layer c is 0.005-0.5 mm, and the thickness of the intermediate layer b is !!-7 mm. Multilayer sheet.

[10] The multilayer sheet according to any one of claims 1 to 9, obtained by simultaneously extruding the surface layer a, the intermediate layer b, and the back layer c.

[11] A light diffusing sheet using the multilayer sheet according to any one of claims 10 to 10.