JPWO2008013143A1 - Light diffusion resin composition and light diffusion plate - Google Patents

Abstract

The present invention relates to a resin composition for a light diffusing plate widely used for light diffusing applications such as lighting covers and displays, and a light diffusing plate having high luminance and high light diffusibility. This resin composition for a light diffusing plate is a dispersion that forms a dispersed phase comprising a thermoplastic resin (A) that forms a matrix phase and a completely incompatible thermoplastic resin that does not dissolve in the thermoplastic resin (A). A light diffusing plate obtained by molding a resin composition obtained by mixing one or more types of phase resins (B), wherein the shear shear viscosity ratio of the dispersed phase resin (B) has a frequency of 0.1 Hz and a frequency of 1 Hz. As a ratio (shear viscosity at 0.1 Hz / shear viscosity at 1 Hz), it is in the range of 3 to 6. And a light diffusing plate is a light diffusing plate which has a light diffusibility obtained by shape | molding this resin composition in plate shape.

Description

  The present invention relates to a resin composition for a light diffusing plate and a light diffusing plate that are widely used for light diffusing applications such as lighting covers and displays.

  Transparent resin such as polycarbonate resin and acrylic resin can be obtained by adding a light diffusing agent and processing it into a sheet or plate shape to obtain a uniform luminance surface. Widely used in applications such as mold displays. In particular, in recent years, the demand for light diffusing applications as a surface light source body for a direct backlight of a liquid crystal display or a liquid crystal television has greatly increased.

  In order to make the above light diffusing function appear appropriately, it is required to scatter the light ray without making it travel as straight as possible and to suppress the light transmission loss as much as possible.

  In order to express such required characteristics, the light diffusing plate has conventionally used inorganic particles such as calcium carbonate, barium sulfate, titanium oxide, silicon oxide, talc, mica, aluminum hydroxide, and magnesium oxide in a transparent resin. A method of adding is proposed. In addition, there is a method of scattering light by adding partially crosslinked polymer fine particles such as styrene polymer particles, acrylic polymer particles, siloxane polymer particles, etc. as organic beads, or by using these in combination. It has been proposed (Patent Document 1).

  In addition, in order to produce a light diffusion sheet that has a diffusibility that achieves uniform brightness, excellent transparency, and provides bright diffused light, a transparent resin such as an acrylic resin or styrene resin that forms the matrix phase In addition, a polymer such as a methacrylic ester resin or amorphous cyclic olefin resin as a dispersed phase having a good affinity with the matrix phase resin is once dissolved at a high temperature and a high pressure, and then at a normal temperature and a normal pressure. A method for forming a fine sea-island structure on the order of submicron by phase separation has been proposed (Patent Documents 2, 3, 4, 5).

  Furthermore, there has been proposed a method for efficiently improving light diffusivity by stretching a film using a combination of polymers having different refractive indexes and increasing an aspect ratio (Patent Document 6).

Japanese Patent No. 3195543 JP 2005-181825 A JP-A-10-111402 JP 2001-31774 A JP 2002-228806 A Japanese Patent Laid-Open No. 11-002706

  In recent years, liquid crystal displays or liquid crystal televisions have become larger in screen size, and accordingly, a backlight diffusion plate is also enlarged. For this reason, when inorganic particles having a large specific gravity are used, the weight increases, the performance is inferior compared to organic beads, and the processing equipment wears due to the hardness specific to inorganic materials during processing. Due to the problems, they are now being replaced by materials using organic beads.

  In addition, organic beads synthesize fine particles by a cross-linking reaction such as suspension polymerization, so they have a relatively uniform particle size distribution and a wide range of particle sizes, so they are the mainstream additive for light diffusing materials. It has become. However, in order to achieve higher brightness, it is necessary to add a large amount of beads having a particle diameter of 8 μm or more, resulting in a problem of a decrease in mechanical strength due to secondary aggregation of dispersed particles and a significant increase in cost. There's a problem.

  In addition, although a method for forming dispersed particles of around 5 μm due to a difference in melt viscosity in a thin film application of 5 to 200 μm has been proposed, this method inevitably generates fine particles of 0.1 μm to 0.5 μm, Absorption of light having a wavelength in the vicinity of ultraviolet rays in this particle size range is large, and the total light transmittance is greatly reduced, with the result that the diffusion performance is greatly reduced.

  Furthermore, a technique has been proposed in which fine particles are produced by a combination of polymers that are compatible at high temperature and high pressure, and incompatible polymers at normal temperature and normal pressure. Since the following fine particles are generated, the light transmittance is greatly reduced, and the light diffusion performance is insufficient.

  In addition, a technique has been proposed in which polymer compositions having different refractive indexes are stretched by an extruded sheet to increase the diffusion efficiency by increasing the aspect ratio. Since the ratio of 0.5 μm or less on the diameter side increases and the light transmittance is remarkably lowered, the light diffusion performance is insufficient.

  Furthermore, polymethyl methacrylate and polycarbonate-based materials have a problem of moisture absorption, and the problem of warpage increases as the size increases. Further, the polycarbonate resin has a problem that it is more expensive than an acrylic resin or a styrene resin.

  The present invention has been made in view of the above problems, and has a high brightness, high light diffusibility, light weight, high strength light diffusibility, and low moisture absorption and hardly causes warping, and a light diffusion plate used therefor An object of the present invention is to provide a resin composition.

  As a result of diligent study, the present inventor has suppressed the generation of a dispersed phase having a low particle diameter of 0.5 μm or less and stable particle diameter by melt-mixing a specific resin not mixed with the matrix resin phase as a dispersed phase. The present inventors have found that a diffuser plate having excellent light diffusion performance can be obtained by forming a dispersed phase having the above, and the present invention has been completed.

  The present invention relates to a dispersed phase resin (B) 1 that forms a dispersed phase comprising a thermoplastic resin (A) that forms a matrix phase and a completely incompatible thermoplastic resin that does not dissolve in the thermoplastic resin (A). A resin composition obtained by melt-mixing at least two types, wherein the shear ratio of shear shear viscosity of the dispersed phase resin (B) (shear viscosity at 0.1 Hz / shear viscosity at 1 Hz) is 3 to 6 It is the resin composition for light diffusing plates characterized by being in the range.

  Further, the present invention, the thermoplastic resin (A) comprises an aromatic vinyl resin or a copolymer resin obtained by copolymerizing an aromatic vinyl compound and an unsaturated carboxylic acid ester compound, the unsaturated carboxylic acid ester compound unit Is a resin composition for a light diffusing plate having a weight average molecular weight of 100,000 to 400,000. Here, as the thermoplastic resin (A), polystyrene or styrene-methyl methacrylate copolymer resin is preferable, and as the dispersed phase resin (B), at least a part of the thermoplastic resin (B) has a high weight average molecular weight of 100,000 or more. Preferred examples include high-density polyethylene having a molecular weight or low-density polyethylene having a weight average molecular weight of 80,000 or more.

  Furthermore, according to the present invention, in the light diffusion plate obtained by molding the above resin composition, the proportion of the dispersed phase resin (B) having a particle size of 0.5 μm or less is 5. The light diffusing plate has a thickness of 0 to 5% and a plate thickness of 0.5 to 5 mm. Here, when the light diffusing plate satisfies any one or more of the following, better performance is provided. 1) The water absorption is 0.3% or less, 2) The haze is 70% or more when the total light transmittance at 2 mm thickness is 80%, or 3) The above resin composition One or more organic cross-linked beads or inorganic beads having an average particle diameter of 1.0 to 100 μm are blended with 0.001 to 10 parts by weight of 100 parts by weight of resin in the product.

  The resin composition for a light diffusing plate of the present invention is obtained by dispersing a dispersed phase resin (B) forming a dispersed phase in a thermoplastic resin (A) forming a matrix phase.

  The thermoplastic resin (A) forming the matrix phase is not particularly limited as long as it is a thermoplastic resin, but examples thereof include olefin resins such as polyethylene and polypropylene, polyvinyl chloride, and vinyl chloride-vinyl acetate copolymers. Vinyl chloride resins, polyvinyl acetate, vinyl acetate resins such as ethylene-vinyl acetate copolymer, polyvinyl alcohol resins such as polyvinyl alcohol, ethylene-vinyl alcohol copolymer, polymethyl methacrylate, methyl methacrylate- Acrylic resins such as acrylic acid ester copolymers, homopolymers or copolymers such as polystyrene, styrene-methyl methacrylate copolymers, styrene-maleic anhydride copolymers, and styrene such as rubber-modified styrene resins Resin, polyalkylene terephthalate Polyester resins such as nylon 6, polyamide resins such as nylon 66, and the like polycarbonate resin. The thermoplastic resin (A) may be composed of a plurality of resins as long as they are completely compatible with each other.

  The thermoplastic resin (A) is an aromatic vinyl compound polymer or a copolymer obtained by copolymerizing an unsaturated carboxylic acid ester and an aromatic vinyl compound from the viewpoint of light transmittance and hygroscopicity (hereinafter referred to as MS copolymer). (Also called coalescence) is preferred.

  Examples of aromatic vinyl compounds that give aromatic vinyl compound polymers include styrene, α-methylstyrene, p-methylstyrene, m-methylstyrene, o-methylstyrene, p-methoxystyrene, o-methoxystyrene, and p-chloro. Examples include styrene, o-chlorostyrene, 4-vinylpyridine, 2-vinylpyridine and the like. Of these, styrene and α-methylstyrene are preferably used.

  As the aromatic vinyl compound used in the MS copolymer, one or more of the above aromatic vinyl compounds can be used.

  The unsaturated carboxylic acid ester used in the MS copolymer is methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, butyl methacrylate, isobutyl methacrylate, t-butyl methacrylate, methyl acrylate, ethyl acrylate, acrylic acid Examples include isopropyl, butyl acrylate, isobutyl acrylate, t-butyl acrylate, and 2-ethylhexyl acrylate. Of these, methyl methacrylate, ethyl methacrylate, butyl methacrylate, and t-butyl methacrylate are preferable, and methyl methacrylate is particularly preferable. These unsaturated carboxylic acid ester compounds can be used alone or in combination of two or more.

  Examples of the MS copolymer include a resin obtained by copolymerizing the above aromatic vinyl compound and an unsaturated carboxylic acid ester compound, and a styrene-methyl methacrylate copolymer resin is preferable. Further, the content of units derived from the unsaturated carboxylic acid ester compound in the MS copolymer is preferably 60% by weight or less from the viewpoint of hygroscopicity.

  The thermoplastic resin (A) can be produced by polymerization by a known method. The weight average molecular weight (Mw) of the resin is preferably 100,000 to 400,000. If it is less than 100,000, the fluidity becomes high and becomes brittle, so that cracking or the like is likely to occur during processing.

The dispersed phase resin (B) that forms the dispersed phase is a thermoplastic resin (A) that forms the matrix phase and is completely incompatible with the thermoplastic resin (A), and the preferred combination of the thermoplastic resins (A) varies. The dispersed phase resin (B) has a viscosity ratio of shear viscosity (hereinafter referred to as shear viscosity ratio) in the range of 3-6. Here, since the shear viscosity shear shear viscosity and the shear viscosity ratio have the same meaning as the shear ratio, the shear viscosity is also referred to as shear shear viscosity or shear shear viscosity ratio. This shear viscosity ratio refers to the ratio (V _0.1 / V ₁ ) between the shear viscosity V _0.1 measured at a frequency of 0.1 Hz and the shear viscosity V ₁ measured at a frequency of 1 Hz for the dispersed phase resin (B) alone. That is, the ratio calculated by (shear viscosity at 0.1 Hz / 1 shear viscosity at 1 Hz).
If the shear viscosity ratio is less than 3, the dispersed particle diameter becomes too fine, and the total light transmittance is reduced by absorbing light, which is not preferable. If it is more than 6, the dispersed particle diameter becomes too large, and the mechanical strength such as material strength is increased. This is not preferable because the characteristics are impaired. Specifically, a dispersed phase having a shear viscosity ratio of less than 3 inevitably generates particles of 0.5 μm or less, and the diffusion performance is lowered.

  The dispersed phase resin (B) is a thermoplastic resin different from the thermoplastic resin (A) that is completely incompatible with the thermoplastic resin (A), and shear shear measured by measuring the dispersed phase resin (B) alone. The viscosity ratio is in the range of 3-6. As the dispersed phase resin (B), from the viewpoint of refractive index difference, water absorption, and incompatibility, for example, when the thermoplastic resin (A) is an aromatic vinyl compound or an MS copolymer, a polyolefin resin is preferable.

  As the polyolefin-based resin, polyethylene that can easily be increased in molecular weight is preferable. In the case of high-density polyethylene (HDPE), which is a linear polyethylene, the molecular weight (Mw) is preferably 100,000 or more, and in the case of low-density polyethylene (LDPE) having a large number of side chain branches, the molecular weight is preferably 80,000 or more. When the molecular weight of HDPE and LDPE is smaller than the above, the shear shear viscosity ratio is 3 or less, and it is not preferable because sufficient light diffusion performance cannot be exhibited due to generation of fine particles when a composition is formed during melt mixing.

  The dispersed phase resin (B) may be composed of a plurality of resins, for example, a resin obtained by blending two or more types of HDPE or LDPE. In this case, as long as the resins are completely compatible with each other, the properties of the dispersed phase resin (B) may be provided in a compatible state. If they are not compatible, it is necessary that each of them has the characteristics of the above dispersed phase resin (B) or that the arithmetic average is in the above numerical range.

  Other polymers such as polypropylene and linear low density polyethylene can be used, but the commercially available polypropylene with the highest molecular weight has a shear viscosity ratio of 3 or less, and the linear chain with the highest molecular weight available on the market. Another problem is that it is difficult to obtain a resin having a desired shear viscosity ratio because the shear viscosity ratio of low-density polyethylene is 3 or less.

  The blending ratio of the thermoplastic resin (A) and the dispersed phase resin (B) forming the matrix phase varies depending on the desired plate thickness and total light transmittance. For example, the resin composition of the present invention is a 2 mm thick plate. In the case where the total light transmittance is determined to be 78 to 82%, the dispersed phase resin (B) is generally 0.2 to 100 parts by weight of the thermoplastic resin (A). The amount is 10 parts by weight, preferably 0.5 to 5 parts by weight.

  When the arithmetic average particle size of the dispersed phase in the light diffusion plate made of the resin composition of the present invention is lower than 0.8 μm, the formation of fine particles of 0.5 μm or less is unavoidable, and the diffusion performance is greatly reduced. . Moreover, when the average particle diameter exceeds 500 μm, it is not preferable because mechanical properties such as material strength are hindered. Furthermore, the proportion of the dispersed phase resin (B) having an average particle size of 0.5 μm or less is preferably 5.0% or less in terms of the particle size distribution of the dispersed phase, more preferably 3.0% or less. preferable.

  The light diffusing plate of the present invention is adjusted so that the total light transmittance is 78 to 82%, preferably 79 to 81% when processed into a 2 mm thick plate-like test piece, and 80%. The haze is 70% or more, preferably 80% or more. When the haze is less than 70%, unevenness tends to occur in the transmitted light emitted from the backlight source when the desired total light transmittance is finally adjusted. The total light transmittance varies depending on the amount of the dispersed phase resin (B) added to the resin composition, its refractive index and the dispersed particle diameter, and is controlled by adjusting these. Further, when the total light transmittance required for the diffusion plate is different, the amount of the dispersed phase resin (B) and the like change accordingly.

  The light diffusing plate of the present invention has a low moisture absorption because the temperature of the diffusing plate itself increases due to light irradiation from the light source, and the diffusing plate tends to warp due to the difference in water absorption between the light irradiation side and the transmission side of the back surface. It is preferable that it is material. The water absorption required for the light diffusing plate varies depending on the size of the light diffusing plate. For example, if it is a medium or large light diffusing plate of 15 inches or more, the water absorption is preferably 0.3% or less, more preferably It is 0.25% or less.

Even if the resin composition of the present invention is composed only of the thermoplastic resin (A) and the dispersed phase resin (B), the light diffusion plate obtained by molding the resin is high brightness and high diffusibility alone. Can have. However, the resin composition of the present invention may contain an organic diffusing agent or an inorganic resin comprising a polyamide resin, a polyester resin, a polyolefin resin, an unsaturated carboxylic acid ester compound resin, etc. A diffusing agent may be contained.
Moreover, it is also preferable to mix 0.001 to 10 parts by weight of one or more organic crosslinked beads or inorganic beads having an average particle diameter of 1.0 to 100 μm with 100 parts by weight of the resin in the resin composition.

  Furthermore, the resin composition may include an ultraviolet absorber, an antioxidant, a heat stabilizer, a colorant, a plasticizer, a release agent, an antistatic agent, a weather resistance, as long as the object of the present invention is not impaired. You may contain 1 type (s) or 2 or more types of additives, such as an adjuvant, an internal lubricant, an external lubricant, an antistatic agent, a flame retardant, a light stabilizer, and a fluorescent brightening agent.

  In addition, when the dispersed phase particles contain particles of 1 μm or less, the transmitted light may be yellowish and reddish. You may contain 1 type, or 2 or more types of a pigment, dye, an ultraviolet absorber, and an infrared absorber as a light regulator.

  There is no restriction | limiting in particular in the processing method in particular to the light-diffusion board of the light diffusable resin composition of this invention, It can shape | mold to a predetermined shape by injection molding, extrusion molding, blow molding, etc.

  The thickness of the light diffusing plate of the present invention is 0.5 mm or more, which is less affected by stretching because the dispersed particle diameter tends to be small in applications such as films produced by stretching. However, this is not the case when a diffusion sheet having a thickness of 0.5 mm or less is formed without stretching, ignoring productivity and the like.

EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited to these Examples.
The physical properties of the light diffusing plate were evaluated by the following methods.

(1) Total light transmittance, parallel light transmittance, haze It was performed in accordance with method B of JIS K7105. However, the test piece was 40 mm × 40 mm × thickness 2 mm.

(2) Particle size distribution 2 g of a sample obtained by melt-mixing a specific dispersed phase resin (B) that does not mix with the thermoplastic resin phase (A) is dissolved in 20 ml of a solvent capable of dissolving only the matrix phase. The particle size distribution of the dispersed phase was measured using a laser diffraction / scattering particle size distribution analyzer LA-910 manufactured by Horiba, Ltd. As the solvent used, cyclohexane was used in the system in which the dispersed phase resin (B) was added with PMMA and acrylic beads, and in other cases, only the matrix phase was dissolved using methyl ethyl ketone. Thereafter, the particle size distribution of the dispersed phase was measured by the volume average diameter, and the arithmetic average particle diameter and the arithmetic standard deviation of the dispersed phase resin (B) were calculated. Further, as an abundance ratio of particles of 0.5 μm or less, an integrated value of the existence frequency of particles detected by a laser meter was used.

(3) Measurement of shear shear viscosity Using DAR-50, a rotational dynamic viscoelasticity measuring device, DAR-50, made by Rheologicala Instruments, a test piece having a diameter of 25 mm and a thickness of 2 mm is sandwiched between a parallel plate jig having a diameter of 25 mm and a heating plate. The shear shear viscosity is measured in the range of 01 to 100 Hz and at a temperature of 240 ° C., and the shear viscosity ratio at the frequency of 0.1 Hz and the shear viscosity ratio at 1 Hz (that is, the slope is calculated by calculating the slope thereof). , Non-Newtonian fluidity can be compared).

(1) Preparation of resin composition The resin used is shown below.
Styrene-methyl methacrylate copolymer resin (MS): Nippon Steel Chemical Co., Ltd. MS-200
Polystyrene (GPPS): G-15L manufactured by Toyo Styrene Co., Ltd.
High density polyethylene: Nippon Polyethylene Corporation HB315R Mw 200000
High density polyethylene: Nippon Polyethylene Co., Ltd. HB111R Mw 180000
High density polyethylene: Nippon Polyethylene Corporation HF313 Mw 100000
High density polyethylene: Nippon Polyethylene Corporation HF560 Mw 40000
Linear low density polyethylene: Nippon Polyethylene Corporation NF375 Mw 100000
Low density polyethylene: Nippon Polyethylene Corporation LF128 Mw 120000
Low density polyethylene: Tosoh Corporation Petersen 340
Polypropylene (high molecular weight PP): Nippon Polypro Co., Ltd. Novatec EA9
Polymethylmethacrylate (PMMA): Acrypet VH-001 manufactured by Mitsubishi Rayon Co., Ltd.
Cross-linked acrylic beads: MBX-8 manufactured by Sekisui Plastics Co., Ltd.

  Adjust the compounding amount so that the total light transmittance is 80% in terms of 2mm thickness, and the resin used as the dispersed phase in the matrix phase resin, using a Tanabe Plastic Machine Co., Ltd. 40mmΦ single screw extruder, Melt-kneading was performed under a temperature condition of 190 to 240 ° C. and pelletized to obtain a thermoplastic resin composition.

(2) Preparation of test piece for evaluation Using a small injection molding machine HM-7 (69 kN, cylinder temperature 240 ° C.) manufactured by Nissei Plastic Industry Co., Ltd., a test piece of 40 mm × 40 mm × 2 mm was prepared.

Example 1
100 parts by weight of MS-200 and 2.0 parts by weight of HB315R were blended, and a plate-like test piece was obtained in accordance with the preparation of the resin composition and the production of the test piece for evaluation. Table 1 shows the measurement results of various physical properties.

Example 2
A test piece was obtained using 100 parts by weight of MS-200 and 1.7 parts by weight of HB111R.

Example 3
Test pieces were obtained using 100 parts by weight of MS-200 and 1.6 parts by weight of HF313.

Example 4
Test pieces were obtained using 100 parts by weight of MS-200 and 1.7 parts by weight of LF128.

Example 5
A test piece was obtained using 100 parts by weight of GPPS and 2.0 parts by weight of HB315R.

Example 6
Using 100 parts by weight of MS-200 and 1.0 part by weight of HB315R, and further blending 0.8 parts by weight of 8 μm cross-linked acrylic beads, a resin composition was obtained in the same manner as in Example 1. Next, a test piece was obtained.

Comparative Example 1
Using 100 parts by weight of MS-200 and 0.5 part by weight of HF560, a resin composition was obtained in the same manner as in Example 1, and then a test piece was obtained.

Comparative Example 2
Test pieces were obtained using 100 parts by weight of MS-200 and 1.6 parts by weight of NF375.

Comparative Example 3
Test pieces were obtained using 100 parts by weight of MS-200 and 0.18 parts by weight of Novatec EA9.

Comparative Example 4
Test pieces were obtained using 100 parts by weight of MS-200 and 0.36 parts by weight of VH-001.

Reference example 1
Using 100 parts by weight of MS-200 and 1.55 parts by weight of 8 μm crosslinked acrylic beads, a resin composition was obtained in the same manner as in Example 1, and then a test piece was obtained.

  The measurement results are summarized in Tables 1 and 2. The shear viscosity ratio is a numerical value of the resin to be a dispersed phase (excluding beads when beads are used). Moreover, 0.5 micrometer or less particle | grains (%) is the numerical value calculated | required by the particle size distribution conversion of the dispersed phase. In the table, N.D. indicates non-detection.

  From Tables 1 and 2, the test piece of the example has a haze of about 90% when the total light transmittance is about 80%, extremely high diffusibility, and the number of dispersed particles of 0.5 μm or less is not detected (ND ). Moreover, the test piece of a comparative example shows that the haze is very low as 10 to 50%, and the number of dispersed particles of 0.5 μm or less is 5% or more.

Industrial applicability

  The light diffusing resin composition according to the present invention uses the specific dispersed phase resin (B) that does not mix with the thermoplastic resin phase (A), so that the generation of fine particles of 0.5 μm or less is extremely small. A stable dispersed phase particle can be formed, and a material that efficiently expresses a light diffusing function can be provided.

Claims (8)

  Melt one or more types of dispersed phase resin (B) that forms a dispersed phase consisting of a thermoplastic resin (A) that forms a matrix phase and a completely incompatible thermoplastic resin that does not dissolve in the thermoplastic resin (A). A resin composition obtained by mixing, wherein the viscosity ratio of the shear viscosity of the dispersed phase resin (B) expressed by the shear viscosity at 0.1 Hz / 1 the shear viscosity at 1 Hz is in the range of 3-6. A resin composition for a light diffusion plate.   The thermoplastic resin (A) comprises an aromatic vinyl resin or a copolymer resin obtained by copolymerizing an aromatic vinyl compound and an unsaturated carboxylic acid ester compound, and the content of the unsaturated carboxylic acid ester compound unit is 0 to 0. 2. The resin composition for a light diffusing plate according to claim 1, which is 60% by weight and has a weight average molecular weight of 100,000 to 400,000.   The resin composition for a light diffusing plate according to claim 1, wherein the thermoplastic resin (A) is polystyrene or a styrene-methyl methacrylate copolymer resin.   The light diffusion according to claim 1, wherein at least a part of the dispersed phase resin (B) comprises a high-density polyethylene having a weight average molecular weight of 100,000 or more or a low-density polyethylene having a weight average molecular weight of 80,000 or more. Resin composition for board.   In the light diffusing plate obtained by molding the resin composition according to any one of claims 1 to 4, the proportion of the dispersed phase resin (B) having a particle size of 0.5 µm or less is converted to the particle size distribution of the dispersed phase. And 5.0% or less, and the thickness of the plate is 0.5 to 5 mm.   The light diffusing plate according to claim 5, wherein the water absorption is 0.3% or less.   The light diffusing plate according to claim 5, wherein the haze is 70% or more when the total light transmittance at 2 mm thickness is 80%.   One or more organic crosslinked beads or inorganic beads having an average particle diameter of 1.0 to 100 µm are added to 100 parts by weight of the resin in the resin composition according to any one of claims 1 to 4, 0.001 to A resin composition for a light diffusing plate, comprising 10 parts by weight.