TWI391244B - Styrene-based resin composition and molded body - Google Patents

Description

Styrene resin composition and formed body

The present invention relates to a multilayer sheet having good light diffusibility, dimensional stability, and light resistance. In particular, it relates to a light-diffusing sheet of a light-transmitting plate of a transmissive screen type or a liquid crystal television which is suitable for use in projection screens and the like.

A screen lens for a transmissive screen or the like for projecting a television such that an image is projected behind and an image is displayed. This screen lens is generally composed of a lens molded body such as a lenticular lens or a Fresnel lens, since it is desired for a viewer to be bright and has a wide viewing angle. A methacrylic resin which has excellent transparency, light resistance, damage resistance, and moldability is widely used in these lens molded bodies, and these molded articles are generally formed by press molding, extrusion molding, casting molding, and injection molding. Forming, etc. are formed.

The methacrylic resin used in the screen lens has a high water absorption rate, so that the size of the molded body for the screen lens is changed, the screen is warped, floated, and the optical property is impaired, or the screen lens has a frame. The problem of body shedding. Further, the temperature at the time of transport of the screen lens or the temperature of the use environment becomes high, causing a problem of deformation.

In order to solve such problems, Patent Document 1 discloses that a mixture of an aromatic vinyl monomer, a (meth) acrylate monomer, and a polyfunctional unsaturated monomer is dissolved in a styrene-diene copolymer. Polymerization, a method of obtaining a Fresnel lens. However, a molded article for a screen lens having good light diffusibility obtained in this technique is not preferable.

Further, since the methacrylic resin used as the light-diffusing sheet substrate of the liquid crystal television has a high water absorption rate, there is a problem that the dimensional change of the light-diffusing sheet molded body occurs, and the light-diffusing sheet is warped to impair the optical characteristics. . In addition, after the surface of the image or the light is irradiated, the resin used in the screen lens or the light diffusing plate is discolored by deterioration and the image is discolored.

Patent Document 1: Japanese Patent Publication No. 5-341101

An object of the present invention is to provide a multilayer sheet which has excellent dimensional stability, light resistance, light diffusibility and antistatic property, and is particularly suitable for a light diffusion sheet such as a molded body for a screen lens or a molded body for a light diffusing sheet. Multi-layer sheet.

In order to solve this problem, the inventors of the present invention have found that a copolymer containing a styrene monomer unit and a (meth) acrylate monomer unit as a main component and a specific unmelted compound are found. The resin composition is an intermediate layer, a copolymer containing a styrene monomer unit and a (meth) acrylate monomer unit as a main component, and a resin composition containing a specific unmelted compound and a specific light stabilizer as a surface layer. After the inner layer, a multilayer sheet having good dimensional stability, light resistance, light diffusibility, and antistatic property can be obtained, and the present invention is completed.

That is, the present invention has the following main points.

(1) A light-diffusing sheet composed of a plurality of layers, wherein the surface layer a and the inner layer c are formed of the following (A) component, and the intermediate layer b is a multilayer sheet formed of the component (B).

(A) Component: 100 parts by mass of a styrene-based copolymer composed of 20 to 50% by mass of a styrene monomer unit and 80 to 50% by mass of a (meth) acrylate monomer unit The styrene copolymer has a refractive index difference of 0.005 or less, and 1 to 10 parts by mass of an unmelted compound having an average particle diameter of 5 to 15 μm, 0.1 to 2 parts by mass of a hindered amine compound, and 0.1 to 2 parts by mass. A styrene resin composition composed of a benzotriazole-based compound and 0.1 to 3 parts by mass of an amine-based surfactant.

(B) Component: For 100 parts by mass of a styrene copolymer composed of 50 to 100% by mass of a styrene monomer unit and 50 to 0% by mass of a (meth) acrylate monomer unit, A styrene-based resin composition comprising an unmelted compound having a refractive index difference of 0.05 to 0.15 with respect to the styrene-based copolymer and having an average particle diameter of 2 to 10 μm in an amount of 1 to 10 parts by mass.

(2) The unmelted compound contained in the component (A) is a multilayer which is contained in the above (1), which contains a styrene monomer as a monomer unit and a crosslinked copolymer of a (meth) acrylate monomer. Sheet.

(3) The unmelted compound contained in the component (B) is a multilayer sheet as described in the above (1) or (2), which comprises a crosslinked polymer of a (meth) acrylate monomer as a monomer unit.

(4) A multilayer sheet according to any one of the above (1) to (3), wherein the hindered amine compound is bis(2,2,6,6-tetramethyl-4-piperidyl)sebacate.

(5) The benzotriazole-based compound is the above (1)~(2-(2H-benzobisazol-2-yl)-4-(1,1,3,3-tetramethylbutyl)phenol. 4) A multilayer sheet of any of the following.

(6) The amine-based surfactant is a multilayer sheet of any one of the above (1) to (5) which is an N-hydroxyethyl-N-(2-hydroxyalkyl)amine.

(7) at least one of the components (A) and (B), and more preferably 0.0005 to 0.5 parts by mass of the benzoxazole-based compound per 100 parts by mass of the styrene-based copolymer (1) The multilayer sheet of any of (6).

(8) The benzoxazole-based compound is a multilayer sheet as described in the above (7) of 2,5-thiophenediyl (5-t-butyl-1,3-benzoxazole).

(9) A multilayer sheet according to any one of the above (1) to (8), wherein the thickness of the surface layer a and the inner layer c is 0.005 to 0.5 mm, and the thickness of the intermediate layer b is 1 to 7 mm.

(10) A multilayer sheet according to any one of the above (1) to (9), which is obtained by simultaneously processing the surface layer a, the intermediate layer b, and the inner layer c.

(11) A light-diffusing sheet using the multilayer sheet of any one of the above (1) to (10).

The light-diffusing sheet obtained by the present invention is suitable for optical display applications because of its excellent optical properties, size, stability, light resistance, and antistatic property.

[Best form of implementation of the invention]

Hereinafter, the detailed description of the present invention will be made.

As the styrene monomer used in the present invention, for example, styrene, α-methylstyrene, p-methylstyrene, p-t-butylstyrene, etc., and preferably benzene Ethylene.

In the present invention, examples of the (meth) acrylate type monomer include methyl methacrylate, ethyl methacrylate, methacrylate, ethyl acrylate, n-butyl acrylate, and 2-methyl. Examples of hexyl acrylate, 2-ethylhexyl acrylate, octyl acrylate, and the like. These may be used alone or in combination of two or more. Preferred are methyl methacrylate, ethyl acrylate, or n-butyl acrylate, or mixtures thereof.

The styrene copolymer in the component (A) used in the surface layer and the inner layer of the present invention is 20 to 50% by mass of a styrene monomer unit, preferably 35 to 50% by mass, and 80 to 50% by mass. The (meth) acrylate monomer unit is preferably 65 to 50% by mass. When the styrene monomer unit is less than 20% by mass, the light-diffusing sheet is warped after moisture absorption, whereas when it exceeds 50% by mass, the light resistance is lowered, and discoloration occurs by light irradiation.

The styrene-based copolymer of the component (B) used in the intermediate layer of the present invention is composed of 50 to 100% by mass of a styrene monomer unit, preferably 70 to 100% by mass, and 50 to 0% by mass. The (meth) acrylate monomer unit is preferably 30 to 0% by mass. When the styrene monomer unit is less than 50% by mass, deformation is caused by moisture absorption.

The styrene-based copolymer of the component (B) used in the intermediate layer of the present invention may be subjected to a copolymerizable vinyl monomer in addition to the styrene monomer and the (meth) acrylate monomer. The copolymerization is preferably 10 parts by mass or less based on 100 parts by mass of the total of the styrene monomer and the (meth) acrylate monomer. Examples of the ethylene monomer which can be copolymerized are, for example, a vinyl cyanide monomer such as acrylonitrile or methacrylonitrile; methacrylic acid, acrylic acid, maleic anhydride, maleic acid, itaconic acid, itaconic anhydride, etc. Examples of the unsaturated carboxylic acid monomer; a maleic anhydride imide imine such as maleic anhydride imide, N-methyl maleic anhydride imide, or N-phenylmaleic anhydride imide. These may be used alone or in combination of two or more.

The unmelted compound in the component (A) is preferably a compound having a melting point or a softening point at 200 ° C or higher in a 1 atmosphere atmosphere. When the melting point and the softening point are less than 200 ° C, when the styrene copolymer is melt-kneaded, or when the styrene resin composition is flaky, the compound is easily melted and the optical properties are not maintained. . The difference in refractive index between the styrene-based copolymer and the unmelted compound in the component (A) is preferably 0.005 or less, preferably 0.003 or less. When the refractive index difference exceeds 0.005, the total light transmittance and the light diffusivity are lowered. Further, the average particle diameter of the unmelted compound is preferably from 1 to 15 μm, preferably from 5 to 14 μm. When the average particle diameter is less than 1 μm, the haze and the diffusivity become small, and the light diffusibility is lowered. On the other hand, when the average particle diameter exceeds 15 μm, the total light transmittance is lowered. In addition, the average particle size of the unmelted compound utilizes Kurt. The value obtained by the composite classifier (manufactured by Kerman Coulter Co., Ltd.). The measurement method is carried out by laser reflection light scattering method, water is used in the solvent, and the output power of 200 W is added in a homogenizer for 1 minute to disperse the sample, and the concentration of PIDS (differential scattering polarization) is adjusted to 45~ 55%, the water refractive index was measured as 1.33, and the volume distribution was calculated as the average particle diameter.

The unmelted compound must be contained in an amount of 1 to 10 parts by mass, preferably 2 to 9 parts by mass, per 100 parts by mass of the styrene-based copolymer in the component (A). When the content of the unmelted compound is less than 1 part by mass, the haze and the diffusivity become small, and the light diffusibility is lowered. On the other hand, if the amount exceeds 10 parts by mass, the total light transmittance is lowered. The unmelted compound in the component (A) is not particularly limited, and it is generally preferred to use a crosslinked copolymer of a styrene monomer and a (meth)propionate monomer having a monomer unit.

Further, the styrene-based single system is exemplified by styrene, α-methylstyrene, p-methylstyrene, p-t-butylstyrene, and the like, and styrene is preferable. Further, the (meth) acrylate-based single system is exemplified by methyl methacrylate, ethyl methacrylate, methyl acrylate, etc., and preferably methyl methacrylate.

For 100 parts by mass of the styrene-based copolymer, the component (A) must contain 0.1 to 2 parts by mass of the hindered amine compound, preferably 0.2 to 1.2 parts by mass, and 0.1 to 2 parts by mass of the benzoic acid. The triazole compound is preferably 0.2 to 1.2 parts by mass.

When the hindered amine compound and the benzotriazole compound are each less than 0.1 part by mass, the light resistance is lowered, and if it exceeds 2 parts by mass, the yellowness of the obtained light-diffusing sheet tends to be strong.

The hindered amine compound is a light amine stabilizer, such as: bis(2,2,6,6-tetramethyl-1(octyloxy)-4-piperazinyl) sebacate, double ( 1,2,2,6,6-pentamethyl-4-piperidinyl)[[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]methyl]butyl Malonate, bis(1,2,2,6,6-pentamethyl-4-piperidyl)sebacate, methyl 1,2,2,6,6-pentamethyl-4- Piperidinyl sebacate, bis(2,2,6,6-tetramethyl-4-piperidyl) sebacate, and the like. These may be used singly or in combination of two or more.

Further, the benzotriazole-based compound is an ultraviolet absorber such as 2-(2H-benzotriazol-2-yl)-p-cresol or 2-(2H-benzotriazol-2-yl)- 4-6-bis(1-methyl-1-phenylethyl)phenol, 2-[5-chloro(2H)-benzotriazol-2-yl]-4-methyl]-6-(t -butyl)phenol, 2,4-di-t-butyl-6-(5-chlorobenzotriazol-2-yl)phenol, 2-(2H-benzotriazol-2-yl)-4 , 6-di-t-pentylphenol, 2-(2H-benzotriazol-2-yl)-4-(1,1,3,3-tetramethylbutyl)phenol, and the like. These may be used singly or in combination of two or more.

In the component (A) of the present invention, it is necessary to contain 0.01 to 3 parts by mass of the amine-based surfactant, preferably 0.1 to 2.5 parts by mass, per 100 parts by mass of the styrene-based copolymer. When the amine-based surfactant is less than 0.01 parts by mass, the antistatic property will be insufficient, and if it exceeds 3 parts by mass, the resulting resin composition or molded article may be discolored.

Amine surfactants such as alkyl diethanolamine, polyethylene oxide alkylamine, alkyl diethanol amine, polyethylene oxide alkylamine, N-hydroxyethyl-N-(2-hydroxyalkyl) In the case of an amine or the like, these may be used singly or in combination of two or more.

The at least one of the component (A) and the component (B) of the present invention contains 0.0005 to 0.5 part by mass, more preferably 0.0008 to 0.2 part by mass of a coloring agent, a benzoxazole compound of a fluorescent whitening agent. Suitable. When the content of the benzoxazole-based compound in at least one of the components is 0.0005 parts by mass or more and less than 0.0005 parts by mass, the yellowness of the obtained multilayer sheet is lowered to improve the appearance, and the result is obtained as a multilayer sheet. The light transmission rate tends to increase. When the amount is 0.5 parts by mass or less, the light resistance of the obtained multilayer sheet is improved as compared with those exceeding 0.5 parts by mass.

Examples of benzoxazole compounds are: 2,5-thiophenediyl (5-t-butyl-1,3-benzoxazole, 2,5-thiophenediyl (5-t-butyl-1) , a mixture of 10-benzoxazole 10% and dicyclohexyl phthalate 90%, 4,4'-bis(benzoxazol-2-yl)anthracene, etc., which can be used alone. They can also be combined for use.

The unmelted compound used for the component (B) is preferably a compound having a melting point or a softening point at 200 ° C or higher in an atmosphere of 1 atm. When the melting point and the softening point are less than 200 ° C, the unmelted compound is easily melted during the melt-kneading with the styrene-based copolymer or during the flaking of the styrene-based resin composition, and good optical characteristics cannot be maintained. Further, the difference in refractive index between the styrene-based copolymer and the unmelted compound in the component (B) is preferably 0.05 to 0.15, preferably 0.07 to 0.13. When the refractive index difference is less than 0.05, the haze and diffusivity of the obtained light-diffusing sheet become small, and the light diffusibility is lowered. On the other hand, if the refractive index exceeds 0.15, the total light transmittance and the light diffusivity are lowered. Further, the average particle diameter of the unmelted compound is 2 to 10 μm, preferably 3 to 9 μm. When the average particle diameter of the unmelted compound is less than 2 μm, the haze of the obtained light-diffusing sheet becomes small and the light diffusibility is lowered, whereas if it exceeds 10 μm, the total light transmittance is lowered. Moreover, the average particle size of the unmelted compound utilizes Kurt. The value obtained by the composite classifier (manufactured by Beckman Coulter). The measurement method is carried out by laser reflection light scattering method, water is used in the solvent, and the output power of 200 W is added by a homogenizer for 1 minute to disperse the sample, and the concentration of PIDS (differential scattering polarization) is adjusted to 45 to 55. %, the refractive index of water was 1.33, and after the measurement, the average particle diameter was calculated from the volume distribution.

Further, the 100 parts by mass of the styrene-based copolymer in the component (B) must contain 1 to 10 parts by mass, preferably 2 to 9 parts by mass, of the unmelted compound. When the content of the unmelted compound is less than 1 part by mass, the haze of the obtained light-diffusing sheet becomes small and the light diffusibility is lowered, whereas if it exceeds 10 parts by mass, the total light transmittance is lowered. The unmelted compound in the component (B) is not particularly limited, and a crosslinked copolymer mainly composed of a (meth) acrylate monomer is preferred. The (meth) acrylate system is exemplified by methyl methacrylate, ethyl methacrylate, methyl acrylate, etc., and preferably methyl methacrylate.

The method for producing the styrene copolymer in the component (A) and the styrene copolymer in the component (B) is not particularly limited, and a bulk polymerization method, a suspension polymerization method, a solution polymerization method, or an emulsion polymerization method can be generally used. .

The method of blending the components of the component (A) and the component (B) is not particularly limited, and generally, the styrene-based copolymer is blended before, during, and after the polymerization, and the styrene is separated. Examples of the method of blending the copolymer after melt mixing.

When the styrene-based copolymer is granulated and then melt-mixed with the unmelted compound, the mixing method is not particularly limited, and is usually a known mixing such as a high-speed agitating mixer or a tumble mixer. After the apparatus is premixed, it can be uniformly mixed by melt-kneading using an extruder such as a uniaxial extruder or a twin-screw extruder.

Further, a high-concentration mixture in which the unmelted compound is mixed at a high concentration is prepared in the styrene-based copolymer, and after standing, the high-concentration mixture and the styrene-based copolymer are dry-blended at the time of production of the light-diffusing sheet. If the content of the unmelted compound is made to a predetermined concentration, it can also be used as a raw material.

The styrene copolymer in the component (A) and the styrene copolymer in the component (B) may be blended with an additive if necessary. For example, in order to improve fluidity and mold release, it can be blended with plasticizers, lubricants, and polyoxygenated oils. Further, in order to impart thermal stability, a heat stabilizer can be blended. Others can also be used with colorants.

The light-diffusing sheet of the present invention has a multi-layered structure, and the thickness of each layer is formed by the composition of the layer (a) and the inner layer c of 0.005 to 0.5 mm, preferably 0.03 to 0.2 mm, and (B). The intermediate layer b is 1 to 7 mm, preferably 1.2 to 2.5 mm. When the surface layer a and the inner layer c are less than 0.005 mm, the obtained light-diffusing sheet is discolored by light irradiation, and if it exceeds 0.5 mm, deformation is caused by moisture absorption. Moreover, when the intermediate layer b is less than 1 mm and exceeds 7 mm, good optical characteristics cannot be obtained.

The light-diffusing sheet may be bonded by heat-melting or the like obtained by extrusion processing the surface layer a, the intermediate layer b, and the inner layer c, respectively, or may be simultaneously extruded by a double joint using a T-die of the feeding device. In addition to being more advantageous to the economical side, the latter means that the surface of the sheet is more likely to prevent damage, foreign matter, etc., which is beneficial to the quality surface.

[Examples]

Hereinafter, the detailed description of the present invention will be made by way of examples, but the invention is not limited to the embodiments.

[Method for Producing Styrene Copolymer]

The tank used for the production is such that the first complete mixing tank having a volume of about 5 L and the second complete mixing tank having a volume of about 15 L are connected in series, and the first devolatilization tank and the second devolatilization tank of the preheater are two bases. It is formed by in-line connection.

Further, for 100 parts by mass of the monomer solution composed of 10% by mass of styrene and 90% by mass of methacrylate, 15 parts by mass of ethylbenzene, t-butylperoxyisopropylmonocarbonate 0.01 parts by mass of 0.2 parts by mass of 2,4-diphenyl-4-methyl-1-pentene was mixed to prepare a raw material solution. This raw material solution was supplied at 6.0 kg per hour to the first complete mixing tank controlled at 135 °C. The conversion rate at the outlet of the first complete mixing tank was 28% by mass. Then, it was continuously taken out from the first full 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%. Further, the mixture was continuously taken out from the second full mixing tank, and after heating in the preheater, the first devolatilization tank controlled at 67 kPa and 160 ° C was introduced. Further, the mixture was taken out continuously from the first devolatilization tank, and after heating in a preheater, the second devolatilization tank controlled at 1.3 kPa and 230 ° C was introduced, and then the monomer was removed. This was cut into a strand by extrusion, and a pellet-shaped styrene-based copolymer (A-1) was obtained.

A styrene-based copolymer (A-2) was obtained in the same manner as in (A-1) except that a monomer solution composed of 40% by mass of styrene and 60% by mass of methyl methacrylate was used.

A styrene-based copolymer (A-3) was obtained in the same manner as in (A-1) except that a monomer solution composed of 80% by mass of styrene and 20% by mass of methyl methacrylate was used.

A styrene-based copolymer (A-4) was obtained by the same operation as (A-1) except that a monomer solution composed of 100% by weight of styrene and 0% by mass of methyl methacrylate was used.

[Polyorganosiloxane cross-linking ball (B) of unmelted compound]

A polyorganosiloxane was used to crosslink the ball (average particle diameter: 6 μm, refractive index: 1.420, tospearl 2000B manufactured by Toshiba Polymer Co., Ltd.) as an unmelted compound.

[Method for Producing MMA-nBA Copolymer Crosslinked Ball (C) of Unmelted Compound]

20 parts by mass of methyl methacrylate, 80 parts by mass of n-butyl acrylate, 5 parts by mass of divinylbenzene crosslinker, and 0.2 parts by mass of benzamidine peroxide were placed in an autoclave equipped with a stirrer a polymerization initiator, 0.001 parts by mass of sodium laurylbenzene sulfonate suspension stabilizer, 0.5 parts by mass of calcium triphosphate, 200 parts by mass of pure water, polymerization at a temperature of 95 ° C for 6 hours, and polymerization at a temperature of 130 ° C 2 hours. After completion of the reaction, washing, dehydration, and drying were carried out to obtain a crosslinked ball (C). The crosslinked sphere (C) of the unmelted compound had an average particle diameter of 4 μm and a refractive index of 1.460.

[Method for Producing Styrene-MMA Crosslinked Ball (D) of Unmelted Compound]

40 parts by mass of styrene, 60 parts by mass of methyl methacrylate, 5 parts by mass of a cross-linking agent of divinylbenzene, and 0.2 parts by mass of a benzamidine peroxide polymerization initiator, 0.001 were placed in a pressure cooker equipped with a stirrer The mass fraction of sodium laurylbenzene sulfonate suspension stabilizer and 0.5 parts by mass of calcium triphosphate 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 carried out to obtain a crosslinked ball (D-1). (D-1) had an average particle diameter of 8 μm and a refractive index of 1.535.

A crosslinked sphere (D-2) having an average particle diameter of 3 μm and a refractive index of 1.535 was obtained in the same manner as in (D-1) except that 1.0 part by mass of the third calcium phosphate was used.

Further, a crosslinked ball (D-3) having an average particle diameter of 13 μm and a refractive index of 1.535 was obtained in the same manner as in (D-1) except that 0.2 parts by mass of the third calcium phosphate was used.

Further, a crosslinked ball (D-4) having an average particle diameter of 18 μm and a refractive index of 1.535 was obtained in the same manner as in (D-1) except that 0.1 parts by mass of the third calcium phosphate was used.

[Method for Producing PMMA Crosslinked Ball (E) of Unmelted Compound]

100 parts by mass of methyl methacrylate, 5 parts by mass of a divinylbenzene crosslinking agent, 0.2 parts by mass of a benzamidine peroxide polymerization initiator, and 0.001 parts by mass of lauric benzene are placed in an autoclave equipped with a stirrer The sodium sulfonate suspension stabilizer and 0.5 parts by mass of the third calcium phosphate and 200 parts by mass of pure water were subjected to polymerization 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 carried out to obtain a crosslinked ball (E-1). (E-1) had an average particle diameter of 8 μm and a refractive index of 1.494.

A crosslinked sphere (E-2) having an average particle diameter of 1 μm and a refractive index of 1.494 was obtained in the same manner as in (E-1) except that 1.5 parts by mass of the third calcium phosphate was used.

Further, a crosslinked ball (E-3) having an average particle diameter of 3 μm and a refractive index of 1.494 was obtained in the same manner as in (E-1) except that 1.0 part by mass of the third calcium phosphate was used.

Further, a crosslinked ball (E-4) having an average particle diameter of 13 μm and a refractive index of 1.494 was obtained in the same manner as in (E-1) except that 0.2 parts by mass of the third calcium phosphate was used.

[Colorant (F)]

As a coloring agent, a fluorescent whitening agent 2,5-thiophenediyl (5-t-butyl-1,3-benzoxazole) (Ubitex OB manufactured by Ciba Speciality Chemicals Co., Ltd.) (F-1), a resin coloring agent is used. Diarezin BLUE J (F-2) by Mitsubishi Chemical Corporation.

The styrene copolymers (A-1) to (A-4), crosslinked spheres B, C, (D-1) to (D-4), (E-1) according to the mixing ratios shown in Tables 2 and 3. )~(E-4), bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate of a hindered amine compound, 2-(2H- of a benzotriazole compound) Benzotriazol-2-yl)-4,6-di-t-pentanol, amine-based surfactant N-hydroxyethyl-N-(2-hydroxyalkyl)amine, colorant (F- 1) and (F-2) are mixed. The mixture was kneaded by a uniaxial extruder having a diameter of 40 mm at a temperature of 240 ° C and a number of spiral rotations of 100 rpm. After granulation, pellets of styrene resin compositions 1 to 36 as shown in Tables 2 and 3 were obtained. .

[Examples 1 to 13 and Comparative Examples 1 to 26]

Using the styrene resin compositions 1 to 36, a three-layered light-diffusing sheet as shown in Tables 4 to 8 was produced in a T-die type multi-layer extruder having a feeding device. In addition, the middle layer of the multi-layer extruder is used for one single-axis extruder with a full-scraper spiral of 65 mm φ, and one single-axis extruder with a full-scraper spiral of 30 mm φ is used for the inner layer of the multi-layer extruder. The test melter in which the molten resin is combined into a multi-layered feeding device. The temperature of each of the flaking cylinders was operated and formed at 230 °C.

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

The haze is 99% or more, the total light transmittance is 65% or more, the diffusivity is 17% or more, the value of the yellowness is less than 1, and the color difference ΔE value of the light resistance is less than 1, and good optical characteristics can be determined. . Moreover, when good dimensional stability occurs, the water absorption warpage must be less than 1 mm, and the surface specific resistance value must be 10 ¹² Ω or less when good antistatic property occurs.

The respective measurement methods of the obtained light-diffusing sheet were as follows.

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

(2) the diffusion rate: using Nippon Denshoku Industries Co., Ltd. goniophotometer (GC5000L), measured light-receiving angle of 0 ° light transmittance I _0, the light receiving angle of 70 ° light transmittance I _70, according to the following equation.

Diffusion rate (%) = (I ₇₀ /I ₀ ) × 100

(3) Light resistance: The aging tester manufactured by Toyo Seiki Co., Ltd. and A-tras CI 65A were used, and the color difference ΔE after irradiation for 400 hours was measured.

(4) Dimensional stability (absorbent warpage): The light-diffusing sheet cut into 180 mm × 180 mm is placed in an atmosphere of 50 ° C and 80% humidity for 7 days, and the amount of deformation of the front and rear four corners is measured by a cursor, and the average value is obtained. The value of the water absorption warp is the scale of dimensional stability.

(5) Yellowness and color difference: L, a, b were measured by a color difference meter (Σ-80) manufactured by Nippon Denshoku Industries Co., Ltd., and the scale of the yellowness represents the b value. Further, the light resistance evaluation color difference ΔE is obtained by the following formula.

△E=(L-L') ² +(a-a') ² +(b-b') ² ) ^1/2

Here, L, a, b are the hue before the light resistance evaluation, and L', a', b' are the hue after the light resistance evaluation (after 400 hours of irradiation).

(6) Antistatic property: The surface resistivity of the molded body was measured for 24 hours at a temperature of 23 ° C and a humidity of 50% RH using a surface specific resistance measuring machine (R503) manufactured by KAWAGUCHI Co., Ltd. based on JIS K-6911. Use this value as a measure of antistatic properties.

The evaluation other than the light diffusion sheet is as follows.

(7) Refractive index: The unmelted compound was measured in an atmosphere of a wavelength of 598 nm and 23 ° C in an Abbe refractometer. Further, the styrene-based copolymer was measured using a data refractometer (RX-2000, manufactured by ATAGO Co., Ltd.) using a saturated aqueous solution of potassium iodide as a contact liquid, and then measuring at a temperature of 25 °C.

(8) Resin composition of a styrene-based copolymer: A styrene-based copolymer was dissolved in heavy chloroform to prepare a 2% solution, and measurement data was carried out by FT-NMR (FX=90Q type manufactured by JEOL Ltd.). The 13C measurement was calculated from the peak area of styrene and methyl methacrylate.

[Industrial availability]

The multilayer sheet of the present invention has good dimensional stability, light resistance, light diffusibility and antistatic property, and is particularly suitable for a transmissive screen of a projection television or the like, and a light diffusing panel of a liquid crystal television.

In addition, the publication of the Japanese Patent Application No. 2006-196541, filed on Jul. 19, 2006, the entire contents of the patent application, and the entire contents of the abstract are incorporated herein by reference.

Claims (11)

A multi-layered sheet which is a light-diffusing sheet composed of a plurality of layers, characterized in that the surface layer a and the inner layer c are formed of the following (A) component, and the intermediate layer b is a multilayer sheet formed of the component (B), (A) Ingredients: 100 parts by mass of a styrene-based copolymer composed of 20 to 50% by mass of a styrene monomer unit and 80 to 50% by mass of a (meth) acrylate monomer unit, and the benzene The ethylene-based copolymer has a refractive index difference of 0.005 or less, and 1 to 10 parts by mass of an unmelted compound having an average particle diameter of 5 to 15 μm, 0.1 to 2 parts by mass of a hindered amine compound, and 0.1 to 2 parts by mass of benzophenone. a styrene resin composition composed of a triazole compound and 0.1 to 3 parts by mass of an amine-based surfactant, and (B) a component: 50 to 100% by mass of a styrene monomer unit and 50 to 0% by mass 100 parts by mass of the styrene-based copolymer formed of the (meth) acrylate monomer unit, the refractive index difference from the styrene-based copolymer is 0.05 to 0.15, and is 1 to 10 parts by mass. A styrene resin composition composed of an unmelted compound having an average particle diameter of 2 to 10 μm. The multilayer sheet according to claim 1, wherein the unmelted compound contained in the component (A) is a crosslinked copolymer containing a styrene monomer and a (meth) acrylate monomer as a monomer unit. . A multilayer sheet according to claim 1 or 2, wherein the unmelted compound contained in the component (B) is contained as a monomer unit (methyl) a crosslinked polymer of an acrylate monomer. A multilayer sheet according to claim 1 or 2, wherein the hindered amine compound is bis(2,2,6,6-tetramethyl-4-piperidyl)sebacate. A multilayer sheet according to claim 1 or 2, wherein the benzotriazole compound is 2-(2H-benzotriazol-2-yl)-4-(1,1,3,3-tetra Methyl butyl) phenol. A multilayer sheet according to claim 1 or 2, wherein the amine-based surfactant is N-hydroxyethyl-N-(2-hydroxyalkyl)amine. The multi-layer sheet of claim 1 or 2, which is at least one of the components (A) and (B), and further contains 0.0005 to 0.5 mass for 100 parts by mass of the styrene copolymer. a benzoxazole compound. A multilayer sheet according to item 7 of the patent application, wherein the benzoxazole compound is 2,5-thiophenediyl (5-t-butyl-1,3-benzoxazole). In the multilayer structure of the first or second aspect of the patent application, the thickness of the surface layer a and the inner layer c is 0.005 to 0.5 mm, and the thickness of the intermediate layer b is 1 to 7 mm. For example, the multi-layer sheet of the first or second aspect of the patent application is obtained by simultaneously extruding the surface layer a, the intermediate layer b and the inner layer c. A light-diffusing sheet characterized by using the multilayer sheet according to any one of claims 1 to 10.