KR100725828B1 - Light-diffusion plate - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light diffusing plate used for a backlight unit or lighting device of a liquid crystal display, and more particularly, at least one first base resin and light diffusion selected from acrylic resins, styrene-acrylic copolymer resins and styrene resins. A base layer comprising an agent; A light diffusion plate comprising a surface layer comprising at least one second base resin selected from an acrylic resin, a styrene-acrylic copolymer resin, and a styrene resin and a glass bead. As a result, warpage does not occur even in a high temperature and high humidity environment, and it provides a light diffusion plate having excellent optical properties and luminance including total light transmittance and low yellowing even when exposed to a light source for a long time.

Liquid crystal display, acrylic resin, methyl acrylate, glass beads, light diffuser, light diffuser, light stabilizer

Description

Light-diffusion plate

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light diffusion plate used for a backlight unit, an illumination device, or the like of a liquid crystal display.

Conventionally used light diffusing plates include (1) a light diffusing plate (Japanese Patent Application Laid-Open No. 4-275501) obtained by performing a process of imparting physical concavities and convexities to a surface, and (2) a transparent material containing fine particles on a transparent substrate such as a polyester resin. Optical diffuser plate obtained by coating a light diffusing layer made of resin (Japanese Patent Application Laid-Open No. 6-59108), and a light diffusing plate obtained by melt-mixing beads in a transparent resin and extruding them (Japan, Patent Application Laid-Open Patent No. 6-59108). 123802) and (4) disclose a light diffusion plate (Japanese Patent Application Laid-open No. 9-311205) having a sea island structure formed by melt kneading two or more kinds of transparent thermoplastic resins.

The light diffusing plates 1 and 2 are surface diffusing plates, that is, light diffusing effects are obtained by the uneven or coated light diffusing layer formed on the surface. On the other hand, the light diffusing plates 3 and 4 are light diffusing plates having a light diffusing component at least inside the substrate.

Among them, a light diffuser plate obtained by coating a light diffusing layer on the transparent substrate film of ② is currently widely used.

The light diffusion plate made of the existing methyl methacrylate resin, which is mainly used as the light diffusion plate, has excellent optical properties such as total light transmittance, but has low dimensional stability, so it is used together with cold cathode fluorescent lamps and light sources such as LEDs to light and The temperature is changed by the extinguishing, and in such an environment, the water absorption rate of the light diffusion plate can be easily changed, so there are problems such as warpage, wrinkles, deformations such as cracking, and the like. That is, there is a problem that deformation such as bending phenomenon occurs in a high temperature and high humidity environment (Japanese Patent Application Laid-Open No. 07-100985, Japanese Patent Application Laid-open No. 08-198976).

In order to solve this problem, a multilayer sheet to which methyl methacrylate-styrene resin is applied (Japanese Patent Application Laid-Open No. 2004-37483, Korean Patent Publication No. 2003-95262) has been proposed. Inherently, the light resistance is not sufficient, and depending on the use conditions, there may be a problem of deterioration such as coloring.

One of the known methods for improving the light resistance of the resin is the addition of an ultraviolet absorber, but the effect is not sufficient in some cases where the light resistance of the resin is low.

In order to solve the above problems, the present inventors show a low reflection property with high light transmittance, concealability, and matte surface, but also high dimensional stability due to low absorption in high temperature and humid conditions, and yellowing phenomenon even after long exposure to a light source. Experiments confirmed that it can provide a light diffusion plate that does not occur and came to complete the present invention.

Accordingly, the present invention provides a light diffusion plate having excellent optical properties and no yellowing phenomenon without warping in high temperature and high humidity conditions with high dimensional stability, and also having low reflection properties on a matt surface. The purpose is to provide a version.

The present invention for achieving the above object is a base layer containing at least one first base resin and a light diffusing agent selected from acrylic resin, styrene-acrylic copolymer resin and styrene resin; It is formed on at least one surface of the base layer, and provides a light diffusion plate comprising a surface layer containing at least one second base resin and glass beads selected from acrylic resin, styrene-acrylic copolymer resin and styrene resin.

The glass beads of the surface layer are characterized in that the average particle diameter of 10 ~ 70 ㎛, the refractive index is 1.8 ~ 2.5.

Glass beads of the surface layer is characterized in that it comprises 0.5 to 50 parts by weight based on 100 parts by weight of the second base resin.

The surface layer has an embossed shape by the protrusion of the glass beads, characterized in that the surface roughness is 0.1 ~ 50㎛.

Acrylic resin of the 1st base resin of the said base material layer, or the 2nd base resin of the said surface layer is a methacrylic acid alkyl ester, an acrylic acid alkyl ester, methacrylic acid cycloalkyl ester, acrylic acid cycloalkyl ester, methacrylic acid aryl ester, and acrylic acid At least one member selected from homopolymers and copolymers obtained from monomers selected from aryl esters.

The styrene-acrylic copolymer resin of the first base resin of the base material layer or the second base resin of the surface layer may be alkyl methacrylate, alkyl acrylate, cycloalkyl ester of methacrylic acid, cycloalkyl ester of acrylic acid, or aryl methacrylate. A copolymer of at least one acrylic monomer selected from esters and aryl esters with at least one styrene monomer selected from styrene, α-methylstyrene, m-methylstyrene, p-methylstyrene, and p-methoxystyrene It features.

The styrene resin of the first base resin of the base layer or the second base resin of the surface layer is a homopolymer obtained from a monomer selected from styrene, α-methylstyrene, m-methylstyrene, p-methylstyrene, and p-methoxystyrene. And at least one selected from copolymers.

The light diffusing agent of the base layer is characterized in that 0.01 to 50 parts by weight based on 100 parts by weight of the first base resin.

The surface layer is characterized in that it further comprises 0.01 to 50 parts by weight of the light diffusing agent based on 100 parts by weight of the second base resin of the surface layer.

The light diffusing agent of the substrate layer or the surface layer is characterized in that the particle diameter is 0.2 ~ 50㎛.

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Hereinafter, the present invention will be described in more detail.

As the 1st or 2nd base resin of the base material layer or the surface layer of this invention, it is 1 or more types chosen from acrylic resin, styrene-acrylic copolymer resin, and styrene resin which show the outstanding characteristic in light transmittance, light resistance, etc., The first base resin and the second base resin of the surface layer may be the same resin as needed, or may be different resins.

In particular, the acrylic resin used as the first base resin or the second base resin in the present invention is an alkyl methacrylate such as methyl methacrylate, ethyl methacrylate, butyl methacrylate, 2-ethylhexyl methacrylate; Alkyl acrylates such as methyl acrylate, ethyl acrylate and butyl acrylate; Methacrylic acid cycloalkyl esters such as cyclohexyl methacrylate, 2-methylcyclohexyl methacrylate and dicyclopentanyl methacrylate; Acrylic acid cycloalkyl esters such as cyclohexyl acrylate and 2-methylcyclohexyl acrylate; Methacrylic acid aryl esters such as phenyl methacrylate and benzyl methacrylate; It is preferable that it is at least 1 sort (s) chosen from the homopolymer and copolymer obtained from the monomer chosen from acrylic acid aryl ester, such as phenyl acrylate and benzyl acrylate.

Moreover, the styrene-acrylic copolymer resin used as a 1st base resin or a 2nd base resin is a methacrylic acid alkyl ester, an acrylic acid alkyl ester, methacrylic acid cycloalkyl ester, acrylic acid cycloalkyl ester, methacrylic acid aryl ester, and acrylic acid. It is preferable that it is a copolymer of 1 or more types of acryl-type monomer chosen from an aryl ester, and 1 or more types of styrene-type monomers chosen from styrene, (alpha) -methylstyrene, m-methylstyrene, p-methylstyrene, and p-methoxy styrene.

On the other hand, the surface layer of the present invention contains glass beads in addition to the at least one second base resin selected from acrylic resin, styrene-acrylic copolymer resin and styrene resin.

The glass beads are resins having excellent thermal stability and excellent chemical durability and weather resistance. Therefore, it has been applied to thermos, heat disinfecting medical devices, chemical containers with high heat resistance.

Since the glass beads have a rounded bead shape, the flow and separation properties in the resin can be improved, and the strength and durability of the surface of the light diffusion plate can be increased due to the dimensional stabilization and high filling of the composition. It can be applied to the surface layer of the diffusion plate to increase the brightness.

On the other hand, the glass beads protrude to the surface of the surface layer to have an embossed shape can achieve the effect of having a matte surface and low reflectance. At this time, the surface roughness of the surface layer is suitably about 0.1 ~ 50㎛, if the roughness is more than 50㎛ surface impact strength is insufficient, if the roughness is less than 0.1㎛ the matt effect.

The glass beads used in the present invention are inorganic particles (Na2O, K2O, CaO, TiO2, BaO Fe2O3) in oxide glass such as silica (SiO2), borate glass, silicate glass containing alkali or alkaline earth metal. , High refractive index glass beads containing TiO2). It is also possible to use hollow glass beads having a large refractive index.

The content of the glass beads contained in the surface layer is 0.5 to 50 parts by weight with respect to 100 parts by weight of the second base resin, preferably 5 to 30 parts by weight. If the amount of glass beads is less than 0.5 parts by weight, sufficient retroreflective properties of the light diffusing plate exit layer cannot be obtained, and if it is more than 50 parts by weight, it is disadvantageous in light transmittance.

The size of the glass bead particles in the present invention can be used 10 ~ 70 um, it is preferable to use the 20 ~ 40 um particles. When the glass beads have a particle diameter of less than 10 μm, the surface roughness is lowered to reduce the matte effect. When the glass beads are larger than 70 μm, the surface roughness is too large and the surface impact strength is reduced.

The difference between the refractive index of the second base resin and the glass beads is about 0.3 to 1.0, and the refractive index of the glass beads between 1.8 and 2.5 can be used. The application of such glass beads has a light diffusing function and excellent water repellency.

The light diffusing agent included in the base layer is usually the same refractive index as the base resin, and is used to increase the light diffusion rate, and various organic and inorganic particles are used. In this case, the light diffusing agent exhibits a light diffusing effect even in a small amount when the refractive index with the base resin is large, and a relatively large amount when the refractive index difference is small.

Representative organic particles include methyl methacrylate, ethyl methacrylate, isobutyl methacrylate, normal butyl methacrylate, normal butyl methyl methacrylate, acrylic acid, methacrylic acid and hydroxyethyl methacrylate. , Hydroxypropyl methacrylate, hydroxy ethyl acrylate, acrylamide, metyrol acrylamide, glycidyl methacrylate, ethyl acrylate, isobutyl acrylate, normal butyl acrylate, 2-ethylhexyl acrylate polymer Or acrylic polymer particles such as copolymers or terpolymers thereof; Olefin polymer particles such as polyethylene and polypropylene; Acrylic and olefin copolymer particles, polystyrene polymer particles, homopolymer particles, and multi-layered multi-component particles made by covering the layer with other monomers on the layer, and siloxane polymer particles.

On the other hand, examples of the inorganic light diffusing particles include calcium carbonate, barium sulfate, silicon oxide, aluminum hydroxide, titanium oxide, zirconium oxide, magnesium fluoride, talc, glass, mica and the like. Normally, the organic particles have excellent light diffusivity compared to the inorganic particles, and if necessary, two or more kinds of light diffusing particles can be used in combination.

In addition, the light diffusing agent included in the base layer may be further included in the surface layer. Further comprising a light diffusing agent and a glass bead in the surface layer to further increase the light diffusion results, as well as the glass diffusing particles protrude to the surface of the surface layer like the glass beads to have an embossed shape, thereby providing a matte surface and low reflectance Can have the effect of having. At this time, the surface roughness of the surface layer is suitably about 0.1 ~ 50㎛, if the roughness is more than 50㎛ surface impact strength is insufficient, if the roughness is less than 0.1㎛ the matt effect.

The content of the light diffusing agent used in the substrate layer or the surface layer of the present invention is 0.01 to 50 parts by weight, preferably 0.5 to 20 parts by weight, based on 100 parts by weight of the first base resin or the second base resin of the surface layer. Parts by weight. If the amount of the light diffusing agent is less than 0.01 part by weight, it is difficult to expect sufficient light diffusing effect and concealability, and if it is more than 50 parts by weight, light transmittance is not good. At this time, the content of the light diffusing agent may be determined according to the difference in refractive index with the base resin.

On the other hand, in the present invention, a light stabilizer may be added to the base layer or the surface layer, the light stabilizer that can be added as a UV absorber and a radical scavenger having a maximum absorption wavelength in the range 250nm ~ 380nm can maximize the light stabilizer effect Ultraviolet stabilizers of hindered amines are preferred. They must be effective for a long time, must not be evaporated or extracted to be freed or removed from the sheet, and an absorbent with good compatibility with the substrate should be selected.

Examples of the ultraviolet absorber include cyanoacrylic, salicylate, malonic ester, oxalanilide, diketone, hydroxy benzophenone, hydroxy benzotriazole, organometallic, and the like. The above combination can be used.

Examples of ultraviolet stabilizers include piperidinyl esters, oxazolidines and piperidino oxazolidines, piperidisspiroacetals, diazacycloalkanones, and the like, and two or more selected from these may be used in combination.

The content of the light stabilizer is 0.01 parts by weight to 5 parts by weight, preferably 0.1 parts by weight to 2 parts by weight based on 100 parts by weight of the base resin of the base layer or the surface layer. In particular, by including them in the surface layer, it is possible to obtain the expected light stability effect without lowering the total light transmittance and physical properties of the substrate layer, and also bring about the effect of cost reduction. In addition, since the surface layer contains glass beads, even if the light stabilizer content is lowered, an excellent light stabilizer effect can be obtained.

The light diffusing plate of the present invention can be produced by a method such as co-extrusion molding, lamination, heat bonding, surface coating, etc., which are known techniques.

The light diffusion plate of the present invention can be used for various applications indoors and outdoors. That is, it can be used for signage, lighting signage, lighting cover, glass showcase, and preferably used as a light diffusion plate for display. Representative examples of display light diffusers include light diffusers for liquid crystal display backlights or edge light type backlights.

Hereinafter, examples of the present invention will be described in more detail, but the scope of the present invention is not limited to these examples.

Compositions and composition ratios of Examples 1 to 20 and Comparative Examples 1 to 12 are as shown in Table 1 below, and Examples 1 to 10 and Comparative Examples 1 to 6 form surface layers on one surface of the substrate layer. 11-20 and Comparative Examples 7-12 are surface layers formed on both surfaces of a base material layer.

At this time, the molding was coextruded at a screw diameter of 135 mm and 60 mm, respectively, and the molding temperature was performed at 250 ° C., and Examples 1 to 10 and Comparative Examples 1 and 2 each had a thickness of the substrate layer of 1.9 mm and a surface layer. The thickness of was 0.1 mm, and in Examples 11 to 20 and Comparative Examples 3 and 4, the thickness of the base material layer was 1.8 mm, the thickness of the surface layer was both 0.1 mm.

Substrate layer Surface layer 1st base resin Light diffusing agent 2nd base resin Glass beads Light diffusing agent Light stabilizer Example 1 and Example 11 MM resin 100 parts by weight 2 parts by weight of silicon beads MM resin 100 parts by weight UB-12M 10 parts by weight - 0.2 part by weight of ultraviolet absorbers Example 2, Example 12 MM resin 100 parts by weight 2 parts by weight of silicon beads MM resin 100 parts by weight UB-12M 10 parts by weight MM resin bead 5 parts by weight 0.2 part by weight of ultraviolet absorbers Example 3, Example 13 MM resin 100 parts by weight 2 parts by weight of silicon beads MM resin 100 parts by weight UB-12M 30 parts by weight - 0.2 part by weight of ultraviolet absorbers Example 4, Example 14 MM resin 100 parts by weight 2 parts by weight of silicon beads MM resin 100 parts by weight UB-12M 30 parts by weight MM resin bead 5 parts by weight 0.2 part by weight of ultraviolet absorbers Example 5, Example 15 MM resin 100 parts by weight 2 parts by weight of silicon beads MM resin 100 parts by weight UB-12M 50 parts by weight - 0.2 part by weight of ultraviolet absorbers Example 6, Example 16 MM resin 100 parts by weight 2 parts by weight of silicon beads MM resin 100 parts by weight UB-12M 50 parts by weight MM resin bead 5 parts by weight 0.2 part by weight of ultraviolet absorbers Example 7 and Example 17 100 parts by weight of MS resin 2 parts by weight of silicon beads 100 parts by weight of MS resin UB-12M 30 parts by weight - 0.2 part by weight of ultraviolet absorbers Example 8, Example 18 100 parts by weight of MS resin 2 parts by weight of silicon beads 100 parts by weight of MS resin UB-12M 30 parts by weight MM resin bead 5 parts by weight 0.2 part by weight of ultraviolet absorbers Example 9, Example 19 100 parts by weight of PS resin 2 parts by weight of silicon beads 100 parts by weight of PS resin UB-12M 30 parts by weight - 0.2 part by weight of ultraviolet absorbers Example 10, Example 20 100 parts by weight of PS resin 2 parts by weight of silicon beads 100 parts by weight of PS resin UB-12M 30 parts by weight MM resin bead 5 parts by weight 0.2 part by weight of ultraviolet absorbers Comparative Example 1, Comparative Example 7 MM resin 100 parts by weight 2 parts by weight of silicon beads MM resin 100 parts by weight - - 0.2 part by weight of ultraviolet absorbers Comparative Example 2, Comparative Example 8 MM resin 100 parts by weight 2 parts by weight of silicon beads MM resin 100 parts by weight - MM resin bead 5 parts by weight 0.2 part by weight of ultraviolet absorbers Comparative Example 3, Comparative Example 9 100 parts by weight of MS resin 2 parts by weight of silicon beads 100 parts by weight of MS resin - - 0.2 part by weight of ultraviolet absorbers Comparative Example 4, Comparative Example 10 100 parts by weight of MS resin 2 parts by weight of silicon beads 100 parts by weight of MS resin - MM resin bead 5 parts by weight 0.2 part by weight of ultraviolet absorbers Comparative Example 5, Comparative Example 11 100 parts by weight of PS resin 2 parts by weight of silicon beads 100 parts by weight of PS resin - - 0.2 part by weight of ultraviolet absorbers Comparative Example 6, Comparative Example 12 100 parts by weight of PS resin 2 parts by weight of silicon beads 100 parts by weight of PS resin - MM resin bead 5 parts by weight 0.2 part by weight of ultraviolet absorbers * MM resin: Methyl methacrylate resin * MS resin: Methyl methacrylate-styrene copolymer resin * PS resin: Styrene resin * Silicone beads: Silicone resin beads, particle size 2㎛ * MM resin beads: Methyl methacrylate beads, Particle size 10 ~ 30㎛ * UV absorber: 2- (2'-Hydroxy-5'-methyl-phenyl) benzotriazole, TINUVIN P * Glass beads: UB-12M (Glass bead, Unibeads Co. Ltd.), refractive index 1.93

As a result of measuring the water absorption rate, the warpage, the total light transmittance, the haze, and the yellowness after exposure, the light diffusing plates manufactured in the above Examples and Comparative Examples are shown in Table 2 below.

Here, the water absorption rate was measured by cutting the light diffusion plate into 10 × 10 ㎝ and left in water at 25 ° C. for 24 hours, and then measuring the water absorption from the weight change. After 96 hours at 75% relative humidity, the four corners were measured from the bottom.

Total light transmittance and haze were measured by ASTM D1003 method.

The yellowing degree after exposure was measured by ASTM D1003 method after performing lamp at 40 degreeC and 240 hours in the Q-UV tester equipped with FS-40313 / 280 according to ASTM D1925 standard.

For luminance measurement, 32-inch BLU for LCD TV was used, and a diffuser film, prism sheet, and DBEF film were placed on the light diffusion plate, and then the luminance meter BM-7 was used. The luminance was measured by measuring 9 points in total.

division Water absorption (%) Deflection (mm) Total light transmittance (%) Haze (%) Yellowness after exposure (△ YI) Average luminance (cd / m ² ) Surface layer formation on one side of the base layer Example 1 0.252 0.33 66.0 99.2 0.8 7300 Example 2 0.263 0.34 66.0 99.4 0.8 7400 Example 3 0.221 0.30 65.0 99.2 0.9 7600 Example 4 0.210 0.29 65.0 99.4 0.9 7800 Example 5 0.188 0.26 63.0 99.2 1.0 7500 Example 6 0.198 0.27 63.0 99.4 1.0 7600 Example 7 0.152 0.33 64.0 99.2 4.57 7600 Example 8 0.154 0.34 64.0 99.4 4.60 7700 Example 9 0.112 0.32 64.0 99.2 6.63 7700 Example 10 0.114 0.31 64.0 99.4 6.58 7700 Comparative Example 1 0.320 0.53 65.0 99.2 1.0 7300 Comparative Example 2 0.325 0.53 65.0 99.4 0.93 7300 Comparative Example 3 0.160 0.38 64.0 99.2 4.52 7200 Comparative Example 4 0.165 0.39 63.0 99.4 4.48 7200 Comparative Example 5 0.120 0.36 63.0 99.2 6.63 7100 Comparative Example 6 0.125 0.37 62.0 99.4 6.58 7150 Surface layer formation on both sides of the base layer Example 11 0.222 0.32 66.0 99.2 0.9 7200 Example 12 0.253 0.33 66.0 99.4 0.9 7300 Example 13 0.201 0.31 65.0 99.2 1.0 7500 Example 14 0.210 0.28 65.0 99.4 1.0 7700 Example 15 0.176 0.25 63.0 99.2 1.1 7400 Example 16 0.194 0.26 63.0 99.4 1.3 7500 Example 17 0.150 0.32 64.0 99.2 4.37 7500 Example 18 0.144 0.32 64.0 99.4 4.63 7600 Example 19 0.102 0.32 64.0 99.2 6.23 7600 Example 20 0.104 0.33 64.0 99.4 6.28 7600 Comparative Example 7 0.310 0.52 65.0 99.2 1.2 7200 Comparative Example 8 0.315 0.51 65.0 99.4 0.92 7200 Comparative Example 9 0.105 0.32 64.0 99.2 2.61 7100 Comparative Example 10 0.115 0.36 63.0 99.4 2.41 7100 Comparative Example 11 0.080 0.36 63.0 99.2 4.16 7050 Comparative Example 12 0.072 0.34 62.0 99.4 3.68 7050

As a result of the physical property evaluation, it can be seen that in the case of Examples 1-12 which do not contain glass beads in the surface layer, the water absorption rate is lower than that of Comparative Examples 1-20, resulting in less warpage. On the other hand, MM resin, MS resin, PS resin in the case of the MM resin has the lowest yellowness, in the case of Example 4, it can be seen that the average brightness is increased by the influence of retroreflective glass beads. Generally, glass beads having low refractive index have high water absorption rate, but high refractive glass beads coated with a surface have low water absorption rate and thus have less influence on the bending characteristics of the light diffusion plate.

Therefore, the light diffusing plate of the present invention is excellent in total light transmittance and light diffusivity, low water absorption rate, and thus is resistant to deformation due to moisture such as warpage phenomenon. It can be seen that the improvement.

As described above, the light diffusing plate of the present invention has low absorbency and high dimensional stability, so that warpage does not occur even in an environment of high temperature and high humidity, excellent optical properties including total light transmittance, and yellowing even when exposed to a light source for a long time. Gave a low light diffusion plate.

Claims (12)

A base layer containing at least one first base resin selected from acrylic resin, styrene-acrylic copolymer resin and styrene resin and a light diffusing agent; A light diffusion plate formed on at least one surface of the substrate layer and including a surface layer containing at least one second base resin and glass beads selected from acrylic resins, styrene-acrylic copolymer resins and styrene resins. The method of claim 1, The glass bead of the surface layer is a light diffusion plate, characterized in that the average particle diameter of 10 ~ 70 ㎛, the refractive index is 1.8 ~ 2.5. The method of claim 1, The glass bead of the surface layer is a light diffusion plate comprising 0.5 to 50 parts by weight based on 100 parts by weight of the second base resin. The method of claim 1, The surface layer has an embossed shape due to the protrusion of the glass beads, the light diffusion plate, characterized in that the surface roughness is 0.1 ~ 50㎛. The method of claim 1, Acrylic resin of the 1st base resin of the said base material layer, or the 2nd base resin of the said surface layer is a methacrylic acid alkyl ester, an acrylic acid alkyl ester, methacrylic acid cycloalkyl ester, acrylic acid cycloalkyl ester, methacrylic acid aryl ester, and acrylic acid A light diffusion plate, characterized in that at least one selected from homopolymers and copolymers obtained from monomers selected from aryl esters. The method of claim 1, The styrene-acrylic copolymer resin of the first base resin of the base material layer or the second base resin of the surface layer may be alkyl methacrylate, alkyl acrylate, cycloalkyl ester of methacrylic acid, cycloalkyl ester of acrylic acid, or aryl methacrylate. A copolymer of at least one acrylic monomer selected from esters and aryl esters with at least one styrene monomer selected from styrene, α-methylstyrene, m-methylstyrene, p-methylstyrene, and p-methoxystyrene Light diffusion plate characterized in that.        The method of claim 1,        The styrene resin of the first base resin of the base layer or the second base resin of the surface layer is a homopolymer obtained from a monomer selected from styrene, α-methylstyrene, m-methylstyrene, p-methylstyrene, and p-methoxystyrene. And at least one member selected from copolymers. The method of claim 1, The light diffusing agent of the base layer is a light diffusion plate, characterized in that 0.01 to 50 parts by weight based on 100 parts by weight of the first base resin. The method of claim 1, And the surface layer further comprises 0.01 to 50 parts by weight of a light diffusing agent based on 100 parts by weight of the second base resin of the surface layer. The method according to claim 1 or 9, The light diffusing agent of the substrate layer or the surface layer is a light diffusion plate, characterized in that the particle diameter is 0.2 ~ 50㎛. delete delete