JP4857286B2 - Light diffusion plate - Google Patents

Description

  The present invention relates to a light diffusing plate used in a backlight unit of a liquid crystal display (LCD), an illumination device, or the like.

  Conventional light diffusing plates include (1) a light diffusing plate obtained by physically roughening the surface (Patent Document 1), and (2) a fine particle-containing transparent resin on a transparent substrate such as a polyester resin. A light diffusing plate obtained by coating a light diffusing layer comprising (Patent Document 2), (3) a light diffusing plate obtained by melting and kneading beads in a transparent resin and extruding the beads (Patent Document 3) And (4) a light diffusing plate having a sea-island structure (Patent Document 4) formed by melting and kneading two or more transparent thermoplastic resins.

  The light diffusing plates of the above (1) and (2) are surface light diffusing plates that obtain a light diffusing effect by unevenness formed on the surface or a coated light diffusing layer. On the other hand, the light diffusing plates of the above (3) and (4) are light diffusing plates having a light diffusing component also inside the substrate.

  Usually, a light diffusing plate manufactured mainly using a methyl methacrylate resin has an advantage of being excellent in optical characteristics such as total light transmittance. However, since such a light diffusing plate has low dimensional stability, it is used with a light source such as a cold cathode fluorescent lamp or an LED, and the moisture absorption rate of the light diffusing plate easily fluctuates when a temperature change occurs due to turning on and off. As a result, there is a problem of deformation that leads to bending, wrinkling, or cracking. That is, there is a problem that deformation such as a bending phenomenon occurs under high temperature and humidity conditions (Patent Documents 5 and 6).

In order to solve such a problem, a multilayer sheet using a methyl methacrylate-styrene resin capable of reducing the absorption capacity has been proposed (Patent Documents 7 and 8). However, the resin used here is essentially insufficient in light resistance, and deterioration such as coloring may occur depending on the use conditions. One known method for improving the light resistance of a resin is the addition of an ultraviolet absorber, but the effect is not sufficient for some resins with low light resistance.
JP-A-4-275501 JP-A-6-59108 JP-A-6-123802 JP-A-9-311205 Japanese Patent Application Laid-Open No. 7-100985 Japanese Patent Laid-Open No. 8-198976 JP 2004-37483 A Republic of Korea Patent Application Publication No. 2003-95262

  In order to solve the above-described conventional problems, the present inventors have made extensive studies on the light diffusion plate. As a result, a light diffusion plate that exhibits high dimensional stability even under conditions of high temperature and humidity due to high heat resistance and low absorbency, and that does not cause yellowing even when exposed to a light source for a long time due to light resistance of the surface layer. Developed and completed the present invention.

  Therefore, an object of the present invention is to provide a light diffusing plate that has high dimensional stability and hardly causes a bending phenomenon even under high temperature and high humidity conditions.

  Another object of the present invention is to provide a light diffusing plate that can be manufactured at a lower price while having high dimensional stability.

  Another object of the present invention is to provide a light diffusing plate that hardly causes yellowing.

  In order to achieve the above object, the present invention provides a light diffusing plate having a base material layer containing a mixture of a polycarbonate resin and a polystyrene resin as a base resin.

  The polycarbonate resin can be selected from the group consisting of homopolymers of linear and branched aromatic polycarbonates prepared by reaction of dihydroxyphenol and phosgene or reaction of dihydroxyphenol and carbonate precursor. .

  The base resin may include a mixture of a polycarbonate resin and a polystyrene resin in a weight ratio of 1: 9 to 9: 1.

  The polycarbonate resin may have a melt index (MI) of 8 to 30 g / 10 min at 300 ° C. and 1.2 kg load in accordance with ASTM D1238.

  The polystyrene resin may have a melt index (MI) of 0.5 to 3 g / 10 min at 200 ° C. under a load of 5 kg in accordance with ASTM D1238.

  The light diffusion plate may further include a surface layer that is formed on one or both sides of the base material layer and includes an acrylic resin or a styrene-acrylic copolymer resin as a base resin.

  The acrylic resin is made of at least one monomer selected from the group consisting of alkyl methacrylate, methacrylate alkyl, cycloalkyl methacrylate, cycloalkyl acrylate, aryl methacrylate, and aryl methacrylate. The resulting homopolymer, copolymer, or mixture thereof can be used.

  The styrene-acrylic copolymer resin is at least one selected from the group consisting of methacrylic acid alkyl ester, acrylic acid alkyl ester, methacrylic acid cycloalkyl ester, acrylic acid cycloalkyl ester, methacrylic acid aryl ester, and acrylic acid aryl ester. It can be a copolymer of one acrylic monomer and at least one styrenic monomer selected from the group consisting of styrene, α-methylstyrene, m-methylstyrene, p-methylstyrene, and p-methoxystyrene.

  The styrene-acrylic copolymer resin can be obtained by reacting an acrylic monomer and a styrene monomer at a weight ratio of 9: 1 to 1: 9.

  The styrene-acrylic copolymer resin can be obtained by reacting an acrylic monomer and a styrene monomer at a weight ratio of 6: 4 to 2: 8.

  The surface layer may further include a fluorine resin or fluorine resin particles.

  The base material layer or surface layer may further contain 0.1 to 35% by weight of a light diffusing agent based on the total weight of the composition of the base material layer or surface layer.

  The light diffusing agent may have a particle size of 0.2 to 50 μm.

  The surface layer may have an embossed shape due to protrusion of the light diffusing agent, and the surface roughness may be 1 to 50 μm.

  The base material layer or surface layer may further contain 0.01 to 5% by weight of a light stabilizer based on the total weight of the composition of the base material layer or surface layer.

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

  In the present invention, the light diffusing plate has a base material layer containing a mixture of a polycarbonate resin and a polystyrene resin as a base resin.

  Polycarbonate resin has excellent impact resistance, light transmittance, cold resistance, and electrical characteristics, and also has particularly high heat resistance and absorption resistance. Wide range. Therefore, this resin is mainly used for optical lenses, optical disk materials, helmets, protective equipment, covers and the like.

  The polycarbonate resin used in the present invention is a commonly used aromatic polycarbonate resin, which is produced by a reaction between dihydroxyphenol and phosgene or a reaction between dihydroxyphenol and a carbonate precursor. Carbonate homopolymers, polyester copolymers, or mixtures thereof. Examples of the dihydroxyphenol include 2,2-bis (4-hydroxyphenyl) propane (ie, bisphenol A), bis (4-hydroxyphenyl) methane, 2,2-bis (4-hydroxy-3,5- Dimethylphenyl) propane, and 1,1-bis (4-hydroxyphenyl) cyclohexane, and examples of the carbonate precursor include diphenyl carbonate, carbonyl halide, and diallyl carbonate.

  The polycarbonate resin preferably has a melt index (MI) in the range of 7 to 30 g / 10 min at 300 ° C. and 1.2 kg load according to ASTM D1238.

  Polycarbonate resin is excellent in impact resistance, absorption resistance, and light transmittance, but has a disadvantage that it is somewhat expensive. Therefore, this polycarbonate resin can also be mixed with polystyrene resin with the same refractive index and relatively low price, thereby reinforcing the rigidity of the polycarbonate resin, reducing the raw material cost in the manufacturing cost, and optical Properties and mechanical properties can be maintained and improved.

  The polystyrene resin used to manufacture the base resin is hard and colorless and transparent, has good electrical characteristics, and is inexpensive due to mass production. Used in electrical appliances such as television cabinets.

  The polystyrene resin used in the present invention preferably has a melt index (MI) of 0.5 to 3 g / 10 min at 200 ° C. and 5 kg load in accordance with ASTM D1238.

  In order to mix polycarbonate resin and polystyrene resin, these resins are melt-kneaded using a twin screw extruder with a screw diameter of 30 mm at a temperature of 200 to 300 ° C., preferably 250 ° C. and a motor speed of 250 rpm. Can do.

  At this time, the polycarbonate resin and the polystyrene resin are mixed at a ratio of 1: 9 to 9: 1. In order to take advantage of the flexibility and dimensional stability of polycarbonate and take advantage of the high absorption resistance and strength of polystyrene, the respective contents should be at least 10% or more.

  The light diffusing plate of the present invention may be a single-layer light diffusing plate comprising only a base material layer containing a base resin, and a multilayer light diffusing plate in which a surface layer is further formed on one or both surfaces of the base material layer. It may be.

  In the case of a multilayer light diffusing plate, in addition to the base material layer described above, a surface layer is formed on one or both surfaces of the base material layer. Although it does not specifically limit as base resin of a surface layer, An acrylic resin or a styrene-acrylic copolymer resin can be used.

  The acrylic resin is composed of methacrylic acid alkyl esters such as methyl methacrylate, ethyl methacrylate, butyl methacrylate, and 2-ethylhexyl methacrylate; acrylic acid alkyl esters such as methyl acrylate, ethyl acrylate, and butyl acrylate; cyclohexyl methacrylate, 2-methylcyclohexyl methacrylate, Methacrylic acid cycloalkyl esters such as 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; Acrylic acids such as phenyl acrylate and benzyl acrylate Selected from among aryl esters It is preferable that a homopolymer or copolymer obtained from at least one monomer.

  The styrene-acrylic copolymer resin can be produced using the above-described resin as an acrylic monomer and using styrene or substituted styrene as a styrene monomer. Examples of the substituted styrene include alkyl styrene such as α-methyl styrene, halogenated styrene such as chlorostyrene, and vinyl styrene. If necessary, two or more styrenic monomers may be used in combination.

  Particularly, in the styrene-acrylic copolymer resin used in the present invention, the acrylic monomer and the styrene monomer are copolymerized at a ratio of 9: 1 to 1: 9, more preferably at a ratio of 6: 4 to 2: 8. Polymerized. Considering the bonding strength with the base material layer, it is preferably used in the above ratio.

  Moreover, the surface layer of the present invention may further contain a fluorine-based resin or fluorine-based resin particles.

  Fluorocarbon resin is excellent in thermal stability, electrical characteristics, chemical durability, weather resistance, light resistance, oxygen resistance, etc., has almost no moisture absorption rate, and has a temperature range of 250 to 300 ° C. due to high heat resistance. And high. Further, since this resin is excellent in surface friction, it is currently applied to various valves, pumps, tanks, filters, pipes, cables, computers, space industries, and the like.

  In particular, the fluororesin or fluororesin particles used in the present invention are tetrafluoroethylene (TFE) homopolymer, copolymer of tetrafluoroethylene and perfluoropropyl ether (PFA), tetrafluoroethylene (TFE) and hexafluoroethylene. Including at least one selected from a copolymer of fluoropropylene (HFP), a copolymer of tetrafluoroethylene and ethylene (ETFE), and a child polymer of vinylidene fluoride (VDF) and tetrafluoroethylene (TFE) . By using this fluorine resin or fluorine resin particles, excellent water repellency can be obtained. Therefore, by including the fluorine-based resin in the surface layer, the dimensional stability is further improved, and the bending phenomenon does not occur even under high temperature and high humidity conditions.

  The content of the fluororesin contained in the surface layer is preferably in the range of 0.5 to 35% by weight, preferably 5 to 15% by weight with respect to the total composition of the surface layer, in consideration of dimensional stability and permeability. A range is more preferred.

  The base material layer or the surface layer may further contain a light diffusing agent. This light diffusing agent usually has a refractive index different from that of the base resin, and is used for increasing the light diffusivity. Various organic and inorganic particles can be used for this purpose. When the refractive index of the light diffusing agent is greatly different from the refractive index of the base resin, a desired light diffusion effect can be obtained even with a small amount. On the other hand, when the difference in refractive index is small, it is necessary to use a relatively large amount of light diffusing agent.

  Representative examples of organic particles include methyl methacrylate, ethyl methacrylate, isobutyl methacrylate, n-butyl methacrylate, n-butyl methyl methacrylate, acrylic acid, methacrylic acid, hydroxyethyl methacrylate, hydroxypropyl methacrylate, hydroxyethyl acrylate, acrylamide, Acrylic polymer particles such as methylol acrylamide, glycidyl methacrylate, ethyl acrylate, isobutyl acrylate, n-butyl acrylate, 2-ethylhexyl acrylate, or copolymers or terpolymers thereof; olefin polymer particles such as polyethylene and polypropylene; acrylic Olefin copolymer particles, homopolymers, copolymers, or After forming the particles over the polymer, other types of obtained over the monomer multilayer multicomponent particles onto the polymer particles layer, a siloxane-based polymer particles, such as tetrafluoroethylene-based particles.

  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. Usually, organic particles are more excellent in light diffusibility than inorganic particles. If necessary, two or more kinds of light diffusing particles may be used in combination.

  When the surface layer further contains a light diffusing agent, the light diffusing effect can be further improved. Further, the light diffusing particles protrude from the surface layer to form an embossed shape, whereby a matte and low reflectance surface can be obtained. At this time, the surface roughness of the surface layer is preferably about 0.1 to 50 μm. When the surface roughness exceeds 50 μm, the surface impact strength becomes insufficient, and when the roughness is less than 0.1 μm, the matte effect is lowered.

  The content of the light diffusing agent used in the substrate layer or surface layer of the present invention is preferably in the range of 0.01 to 35% by weight with respect to the total weight of the composition of the base resin in the substrate layer or surface layer. The range of 0.5 to 15% by weight is more preferable. If the amount of the light diffusing agent is less than 0.01% by weight, it is difficult to expect a sufficient light diffusion effect and mask effect. On the other hand, when the amount of the light diffusing agent exceeds 35% by weight, the light transmittance is deteriorated. The content of the light diffusing agent can be determined by the difference in refractive index from the base resin.

  Moreover, the base material layer or the surface layer of the present invention may contain a light stabilizer. Examples of the light stabilizer include an ultraviolet absorber having an absorption maximum wavelength in the range of 250 nm to 380 nm, or a radical scavenger, for example, a hindered amine UV stabilizer capable of maximizing the light stabilization effect. They must be able to take effect for a long time and must not be separated or removed from the sheet by evaporation or extraction. Moreover, you should select the absorber excellent in compatibility with a base material.

  The UV absorber is selected from the group consisting of cyanoacrylic, salicylate, malonic ester, oxalanilide, diketone, hydroxybenzophenone, hydroxybenzotriazole, organometallic, and mixtures thereof. be able to.

  The UV stabilizer can be selected from the group consisting of piperidinyl esters, oxazolidine and piperidinooxazolidines, piperidyl spiroacetals, diazacycloalkanones, and mixtures thereof.

  The content of the light stabilizer is preferably in the range of 0.01 to 5% by weight and more preferably in the range of 0.1 to 2% by weight with respect to the total weight of the resin composition of the base layer or the surface layer. In particular, when these are contained in the surface layer, a desired light stabilizing effect can be obtained without lowering the total light transmittance and physical properties of the base material layer, and the cost can be reduced.

  The light diffusion plate of the present invention can be used for various uses indoors and outdoors. That is, it can be used for a signboard, a lighting signboard, a lighting cover, and a glass display case, and can be preferably used as a light diffusion plate for a display. As a typical example of the light diffusing plate for a display, a light diffusing plate for a liquid crystal display backlight or an edge light type backlight can be mentioned.

  EXAMPLES Hereinafter, although this invention is demonstrated in detail using an Example, this invention is not limited to these Examples.

  In the examples, polycarbonate resin (PC) and polystyrene resin (PS) are used as the base resin for the base material layer, and are uniformly charged at the composition ratios shown in Tables 1 to 3, and 250 ° C. using a twin screw extruder. Melt kneaded at temperature.

  In this case, the polycarbonate resin has a melt index (MI) of 22 g / 10 min at 300 ° C. and 1.2 kg load according to ASTM D1238, and the polystyrene resin is melted at 200 ° C. and 5 kg load according to ASTM D1238. The index (MI) was 1.5 g / 10 min.

  As the base resin for the surface layer, polymethyl methacrylate, polystyrene, or a styrene-acrylic copolymer resin produced by copolymerizing an acrylic monomer and a styrene monomer according to a conventional method was used.

The light diffusion plate was formed at 250 ° C. by coextrusion using an extruder having a screw diameter of 135 mm and 60 mm. In the light diffusing plate consisting only of the base material layer, the thickness of the base material layer was set to 2.0 mm. In the light diffusion plate including the surface layer, the surface layer was formed only on one side of the base material layer . At this time, the thickness of the base material layer was 1.0 mm, and the thickness of the surface layer was 0.1 mm.

  In the composition of the light diffusing plate in Examples and Comparative Examples, the base material layer is composed of a base resin with 0.2 parts by weight of silicon resin beads (average particle size 2 μm) as a light diffusing agent and an ultraviolet absorber B as a light stabilizer. -Cap (Tetra-ethyl-2,2 '-(1,4-phenylene-dimethylene) -bismalonate) 0.05 parts by weight. The surface layer is composed of a base resin alone or a fluorine-based resin or fluorine-based resin particles according to the composition in the surface layer, 2 parts by weight of silicon resin particles (average particle size 2 μm) as a light diffusing agent, and a light stabilizer. It comprised by mixing 0.5 weight part of ultraviolet absorber B-Cap (Tetra-ethyl-2,2 '-(1,4-phenylene-dimethylene) -bismalonate).

  For the light diffusing plates produced in the above examples and comparative examples, the moisture absorption rate, the deflection, the total light transmittance, the haze, the yellowing degree, and the heat distortion temperature were measured. The measurement results are shown in Tables 5 to 8 below.

  Here, the moisture absorption rate was determined by measuring the change in weight after cutting the light diffusion plate to 10 × 10 cm and leaving it in water at 25 ° C. for 24 hours. Deflection was determined by mounting the sheet on a 20 ″ size backlight unit, leaving it to stand at 60 ° C. and a relative humidity of 75% for 96 hours, and then measuring the degree of bending of the four corners from the bottom. Was measured according to ASTM D648.

  Yellowing degree after exposure is measured according to ASTM D1003 after exposure for 240 hours at 40 ° C. with a Q-UV tester equipped with FS-40 313/280 lamp according to ASTM D1925 standard. did. The total light transmittance and haze were measured according to ASTM D1003.

  As a result of the above physical property evaluation, in the case of a light diffusion plate having a single base layer mixed with polycarbonate resin and polystyrene resin and used as a base resin, the dimensional stability is relatively excellent even under high temperature and high humidity conditions. The degree is high.

  As a result of the above physical property evaluation, in the case of a light diffusing plate having a base material layer mixed with a polycarbonate resin and a polystyrene resin and used as a base resin, and a surface layer containing a base resin made of PMMA resin formed on one side thereof, It can be seen that it exhibits excellent dimensional stability and yellowing.

  Furthermore, in the case of a light diffusing plate containing fluorine-based resin or fluorine-based resin particles in the surface layer, dimensional stability superior to that of a light diffusing plate not containing fluorine-based resin or fluorine-based resin particles is exhibited, and the content is It can be seen that the greater the increase, the better the dimensional stability.

  Therefore, when polystyrene resin with relatively low cost is mixed with polycarbonate resin and used as the base resin of the base material layer, the dimensional stability is equal to or better than when only polycarbonate resin is used as the base resin of the base material layer. As shown, it can be seen that costs can be saved.

  As a result of the above physical property evaluation, a light diffusing plate having a base material layer in which polycarbonate resin and polystyrene resin are mixed and used as a base resin, and a surface layer containing MS resin as a base resin formed on one or both surfaces thereof It can be seen that the case shows excellent dimensional stability.

  Therefore, it can be seen that even if a polystyrene resin having a relatively low cost is mixed with a polycarbonate resin and used as the base resin of the base material layer, it exhibits excellent dimensional stability, so that the cost can be reduced.

  As a result of the above physical property evaluation, it can be seen that in the case of a light diffusing plate not containing a polycarbonate resin and a polystyrene resin in the base material layer, physical properties such as dimensional stability and yellowing degree have decreased.

  From the above, the light diffusing plate of the present invention is excellent in total light transmittance and light diffusibility by using a mixture of a polycarbonate resin and a polystyrene resin for the base material layer, particularly excellent in high heat resistance and absorption resistance, Therefore, the dimensional stability is very excellent. Further, by using a polystyrene resin that is relatively cheaper than the polycarbonate resin, an effect of cost reduction can be expected.

  Moreover, the light diffusing plate of this invention can improve the yellowing degree when exposed to a light source for a long time by providing a surface layer.

  Furthermore, the light diffusing plate of the present invention includes fluorinated resin or fluorinated resin particles in the surface layer, thereby further improving dimensional stability and further lowering yellowing when exposed to a light source for a long time. Therefore, it is possible to provide a light diffusing plate having more excellent physical properties.

  As described above, the present invention provides a light diffusing plate. According to the present invention, the light diffusing plate has a base layer made of a mixture of polycarbonate resin and polystyrene resin as a base resin, so that it has high dimensional stability due to high absorption resistance, and even under conditions of high temperature and humidity. Almost no bending phenomenon occurs. Further, by further forming a surface layer or further including a fluorine resin or fluorine resin particles in the surface layer, the dimensional stability is further improved, and the yellowing degree is extremely high even when exposed to a light source for a long time. A low light diffusion plate can be provided.

  Although the present invention has been described with reference to the preferred embodiments, those skilled in the art will recognize that the present invention can be variously modified and changed without departing from the spirit and scope of the present invention described in the claims. You will understand what you can do.

Claims (17)

A light diffusing plate having a base material layer containing a mixture of polycarbonate resin and polystyrene resin as a base resin, wherein the base resin is a mixture of polycarbonate resin and polystyrene resin in a mass ratio of 5: 1 to 9: 1. A light diffusing plate.   The polycarbonate resin is selected from the group consisting of homopolymers of linear and branched aromatic polycarbonates produced by the reaction of dihydroxyphenol and phosgene or the reaction of dihydroxyphenol and a carbonate precursor. Item 4. A light diffusing plate according to Item 1.   2. The light diffusing plate according to claim 1, wherein the polycarbonate resin has a melt index (MI) of 8 to 30 g / 10 min at 300 ° C. and 1.2 kg load in accordance with ASTM D1238.   2. The light diffusing plate according to claim 1, wherein the polystyrene resin has a melt index (MI) of 0.5 to 3 g / 10 min at 200 ° C. under a load of 5 kg in accordance with ASTM D1238.   The light diffusing plate according to claim 1, further comprising a surface layer formed on one side or both sides of the base material layer and containing an acrylic resin or a styrene-acrylic copolymer resin as a base resin.   The acrylic resin is made of at least one monomer selected from the group consisting of alkyl methacrylate, methacrylate alkyl, cycloalkyl methacrylate, cycloalkyl acrylate, aryl methacrylate, and aryl methacrylate. The light diffusing plate according to claim 5 which is the obtained homopolymer, copolymer, or a mixture thereof.   The styrene-acrylic copolymer resin is at least one selected from the group consisting of methacrylic acid alkyl ester, acrylic acid alkyl ester, methacrylic acid cycloalkyl ester, acrylic acid cycloalkyl ester, methacrylic acid aryl ester, and acrylic acid aryl ester. 6. A copolymer of one acrylic monomer and at least one styrenic monomer selected from the group consisting of styrene, [alpha] -methyl styrene, m-methyl styrene, p-methyl styrene, and p-methoxy styrene. The light diffusing plate described in 1.   The light diffusing plate according to claim 5, wherein the styrene-acrylic copolymer resin is obtained by reacting an acrylic monomer and a styrene monomer at a weight ratio of 9: 1 to 1: 9.   The light diffusing plate according to claim 5, wherein the styrene-acrylic copolymer resin is obtained by reacting an acrylic monomer and a styrene monomer at a weight ratio of 6: 4 to 2: 8.   The light diffusion plate according to claim 5, wherein the surface layer further includes a fluorine-based resin or fluorine-based resin particles.   The light diffusing plate according to claim 1, wherein the base material layer further includes 0.1 to 35% by weight of a light diffusing agent based on a total weight of the composition of the base material layer.   The light diffusing plate according to claim 5, wherein the base material layer or the surface layer further contains a light diffusing agent in an amount of 0.1 to 35% by weight based on a total weight of the composition of the base material layer or the surface layer.   The light diffusing plate according to claim 11, wherein the light diffusing agent has a particle size of 0.2 to 50 μm.   The light diffusing plate according to claim 12, wherein the light diffusing agent has a particle size of 0.2 to 50 μm.   The light diffusing plate according to claim 12, wherein the surface layer has an embossed shape due to protrusion of the light diffusing agent and has a surface roughness of 1 to 50 μm.   The light diffusing plate according to claim 1, wherein the base material layer further includes 0.01 to 5% by weight of a light stabilizer based on a total weight of the composition of the base material layer.   The light diffusing plate according to claim 5, wherein the base material layer or the surface layer further contains 0.01 to 5% by weight of a light stabilizer based on a total weight of the composition of the base material layer or the surface layer.