TWI390296B - Light-diffusion plate - Google Patents

Description

Light diffuser

The present invention relates to a light diffusing plate that can be used in a liquid crystal display (LCD) backlight unit or a lighting device.

A conventional light diffusing plate has disclosed (1) a light diffusing plate having a surface convex portion via a physical process (Japanese Patent Publication No. Hei 4-275501), and (2) a coating on a transparent substrate of a polyester resin. A light-diffusing sheet obtained by a light-diffusion layer of a transparent resin particle (Japanese Patent Publication No. Hei 6-59108), (3) a method in which a bead is melt-mixed with a transparent resin, and the bead and the resin mixture are extruded. And the obtained light diffusing plate (Japanese Patent Publication No. Hei 6-123802), and (4) melt-kneading at least two kinds of transparent thermoplastic resins to form a light diffusing plate having an island-like structure (Showa 9-311205, Japan) No. Patent Publication).

The light diffusing plate of the above items (1) and (2) belongs to a surface light diffusing plate which can exhibit a light diffusing effect by using a surface convex portion or a light diffusing coating. Further, the light diffusing plate of the above items (3) and (4) is a light diffusing plate containing a light diffusing component even on the substrate.

In general, a light diffusing plate prepared mainly of a methyl methacrylate resin has an advantage in that it has superior light properties such as total light transmittance. However, since the shape of the light diffusing plate is low, when it is used together with a light source such as a cold cathode fluorescent lamp or an LED (light emitting diode), and when the light source is turned on or off to cause a temperature change. The water absorption rate of the light diffusing plate is apt to change, causing problems including deformation, resulting in bending, wrinkles or cracks. That is to say, under high temperature and high humidity conditions, deformation such as a bending phenomenon is likely to occur (Japanese Laid-Open Patent Publication No. Hei 07-10098 and No. 08-198976).

In order to solve these problems, a multilayer board containing methyl methacrylate-styrene and having an improved absorption has been proposed (Japanese Patent Publication No. 2004-37483 and Japanese Patent Publication No. 2003-95262). However, the light resistance of the resin used is practically insufficient, and thus may cause deterioration such as coloring. As a known process, an ultraviolet absorber can be added to improve the light resistance of the resin. However, in some resins having low light resistance, these improvement effects are not remarkable.

In order to avoid the problems encountered in the related art, the inventor of the present invention proposed the present invention after conducting intensive and thorough research on the light diffusing plate, thereby developing a high heat resistance and maintaining even under high temperature and high humidity conditions. The low-absorption property, so that the shape stability is high, and the light-diffusing property of the surface layer is long, even if it is exposed to the light source for a long period of time, there is no yellowing phenomenon.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a light diffusing plate having a high degree of dimensional stability, which causes little bending even under high temperature and high humidity conditions.

Another object of the present invention is to provide a light diffusing plate which can be manufactured at a lower cost and which still maintains a high degree of dimensional stability.

It is still another object of the present invention to provide a light diffusing plate which produces little yellowing.

In order to achieve the foregoing objects, the present invention provides a light diffusing plate comprising a substrate layer using a polycarbonate resin as a resin base resin.

Further, the present invention also provides a light diffusing plate comprising a substrate layer comprising a polycarbonate resin and a polystyrene resin mixture as a resin main component.

The polycarbonate resin may be selected from the group consisting of homopolymerized linear and branched aromatic polycarbonates prepared by reacting a dihydric phenol with phosgene or a dihydric phenol with a carbonate precursor. Things.

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

According to the ASTM D1238 standard, the polycarbonate resin may have a melt index of 8 to 30 g/10 minutes at 300 ° C under a load of 1.2 kg.

According to the ASTM D1238 standard, the melt index of the polystyrene resin at 200 ° C is 0.5 to 3 g/10 minutes under a load of 5 kg.

The light diffusing plate may further include a surface layer formed on one or both sides of the substrate layer and containing an acrylic resin or a styrene-acrylic copolymer resin as a resin main component.

The acrylic resin may be a homopolymer, a copolymer or a mixture thereof obtained from at least one monomer selected from the group consisting of alkyl methacrylate, alkyl acrylate, cycloalkyl methacrylate. , cycloalkyl acrylate, aryl methacrylate, and aryl acrylate.

The styrene-acrylic copolymer resin may be an alkyl methacrylate, an alkyl acrylate, a cycloalkyl methacrylate, a cycloalkyl acrylate, an aryl methacrylate, and an aryl acrylate. At least one acrylic monomer selected from the group consisting of: styrene, α-methylstyrene, m-methylstyrene, p-methylstyrene, and p-methoxystyrene a copolymer obtained by copolymerizing at least one styrene monomer selected.

The styrene-acrylic copolymer resin can be obtained by reacting the acrylic monomer with the styrene monomer in a weight ratio of 6:4 to 2:8.

The surface layer may further comprise a fluororesin or fluororesin particles.

The substrate layer or the surface layer may further comprise 0.1 to 35 wt% of a light diffusing agent, respectively, based on the total weight of the respective compositions.

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

The surface layer may have an embossed shape formed by the protrusion of the light diffusing agent, and has a surface roughness of 1 to 50 μm.

The substrate layer or the surface layer may further comprise 0.01 to 5 wt% of a light stabilizer, respectively, based on the total weight of the respective compositions.

The invention is described in detail below.

The light diffusing plate of the present invention comprises a substrate layer comprising a polycarbonate resin or a mixture comprising a polycarbonate resin and a polystyrene resin as a resin base resin.

The polycarbonate resin has excellent impact resistance, light transmittance, cold resistance and electrical properties, especially high heat resistance and absorption resistance, so that it has excellent dimensional stability and a wide temperature range. Therefore, this resin is mainly used for optical lenses, optical disc materials, helmets, shields, covers, and the like.

The polycarbonate resin used in the present invention is a general aromatic polycarbonate resin comprising a linear or branched carbonate homopolymer, a polyester copolymer, or a mixture thereof, which is composed of a dihydric phenol and phosgene. Or a dihydric phenol and a carbonate precursor are produced by reaction. In this connection, examples of dihydric phenols are 2,2-bis(4-hydroxyphenyl)propane (bisphenol A), bis(4-hydroxyphenyl)methane, 2,2-bis(4-hydroxy-3). , 5-dimethylphenyl)propane, and 1,1-bis(4-hydroxyphenyl)cyclohexane. Examples of such carbonate precursors are diphenyl carbonate, halogenated carbonyl, and diaryl carbonate.

According to the ASTM D1238 standard, the melt index (MI) of the polycarbonate resin at 300 ° C is preferably 7 to 30 g/10 minutes under a load of 1.2 kg.

Although the polycarbonate resin has excellent impact resistance, absorption resistance, and light transmittance, it is expensive but it is a disadvantage. Therefore, the polycarbonate resin can be mixed with a polystyrene resin having a similar refractive index and a relatively low price in order to strengthen the rigidity of the polycarbonate resin, reduce the material cost in the production cost, and maintain and enhance the optical and mechanical properties.

The polystyrene resin used for preparing the resin base of the substrate layer has been widely used for such as kitchen utensils, writing materials, and the like because it is hard, colorless, transparent, inexpensive (production relationship), and has good electrical properties. Daily necessities such as furniture, and electrical appliances such as large automobile molds and TV cases.

According to the ASTM D1238 standard, the melt index (MI) of the polystyrene resin used in the present invention at 200 ° C is 0.5 to 3 g/10 minutes under a load of 5 kg.

If you want to mix polycarbonate resin with polystyrene resin, you can use a twin-screw extruder with a screw diameter of 30 mm and a motor with 250 rpm at 200~300 °C, but at a temperature of 250 °C. These resins are melt-kneaded at a rotational speed.

In this connection, the polycarbonate resin and the polystyrene resin may be mixed in a ratio of 1:9 to 9:1. Each of the resins should be added in an amount of at least 10% in order to exhibit advantages of polycarbonate resin such as flexibility and shape stability, and advantages of polystyrene such as high absorbency and strength.

The light diffusing plate of the present invention may be a single-layer light diffusing plate composed only of a substrate layer containing the above-mentioned resin main agent, or a multilayer light composed of the substrate layer and a surface layer formed on one or both sides thereof. Diffuser plate.

In the case of the multilayer light diffusing plate, in addition to the aforementioned substrate layer, a surface layer may be formed on one or both sides of the substrate layer. In this connection, the resin main component of the surface layer is not particularly limited, but an acrylic resin or a styrene-acrylic copolymer resin may be used.

The acrylic resin is preferably a homopolymer or a copolymer obtained from at least one monomer selected from the group consisting of alkyl methacrylates such as methyl methacrylate, ethyl methacrylate, methyl group. Butyl acrylate, and 2-ethylhexyl methacrylate and the like; alkyl acrylates such as methyl acrylate, ethyl acrylate, and butyl acrylate; etc.; cycloalkyl methacrylates such as methacrylic acid rings Hexyl ester, 2-methylcyclohexyl methacrylate, and dicyclopentyl methacrylate; etc.; cycloalkyl acrylates such as cyclohexyl acrylate, and 2-methylcyclohexyl acrylate; Aryl acrylates such as phenyl methacrylate, and benzyl methacrylate; and the like, and aryl acrylates such as phenyl acrylate, and benzyl acrylate.

The styrene-acrylic copolymer resin is prepared by using the above-mentioned resin as an acrylic monomer, and styrene or substituted styrene as a styrene monomer. Examples of the substituted styrene include alkylstyrene such as ?-methylstyrene, halogenated styrene such as chlorostyrene, and vinylstyrene. Further, two or more kinds of styrene monomers may be used as necessary.

In particular, in the styrene-acrylic copolymer resin used in the present invention, the copolymerization ratio of the acrylic monomer and the styrene monomer is from 9:1 to 1:9, but in a ratio of from 6:4 to 1:9. should. These monomers are preferably used in the aforementioned ratio in view of adhesion to the substrate layer.

Further, the surface layer of the present invention may further contain a fluororesin or fluororesin particles.

The fluororesin has excellent thermal stability and electrical properties, and also has good chemical resistance, weather resistance, light resistance and oxygen resistance, especially low water absorption and high heat resistance, so the operating temperature can be as high as 250 ~300 °C. In addition, because of its excellent surface abrasion resistance, this resin is currently used in a wide variety of valve parts, pumps, filters, fittings, cables and computers, and is widely used by the aerospace industry.

In particular, the fluororesin or fluororesin particles used in the present invention include at least one selected from the group consisting of tetrafluoroethylene (TFE) homopolymer, tetrafluoroethylene and perfluoropropyl ether copolymer (PFA), and tetrafluoroethylene (TFE). Copolymer with hexafluoropropylene (HFP), copolymer of tetrafluoroethylene and ethylene (ETFE), and copolymer of vinylidenefluoride (VDF) and tetrafluoroethylene (TFE). When a fluororesin or a fluororesin particle is used, good water repellency is produced. That is, the surface layer is made to contain a fluororesin to further enhance the dimensional stability. As a result, even under high temperature and high humidity conditions, the bending phenomenon does not occur.

The content of the fluororesin in the surface layer is preferably 0.5 to 35 wt% (weight percent) based on the total composition of the surface layer, but considering the shape stability and the light transmittance, it should be 5 to 15 wt%.

Further, the substrate layer or the surface layer may further contain a light diffusing agent having a refractive index different from that of the resin main agent for increasing the diffusivity of light. Various organic or inorganic particles can be used for this purpose. In this connection, if the refractive index of the light diffusing agent is greatly different from that of the resin main agent, the intended light diffusing effect can be exhibited even if the amount is small. On the other hand, if the difference in refractive index is small, the amount of the material should be large.

In general, examples of organic particles are acrylic polymer particles such as methyl methacrylate, ethyl methacrylate, isobutyl methacrylate, n-butyl methacrylate, n-butyl methacrylate, acrylic acid, methyl Acrylic acid, hydroxyethyl methacrylate, hydroxypropyl methacrylate, hydroxyethyl acrylate, acrylamide, methylol acrylamide, glycidyl methacrylate, ethyl acrylate, isobutyl acrylate, acrylic acid Butyl ester, 2-ethylhexyl acrylate polymer, or a copolymer or terpolymer thereof; olefin polymer particles, such as polyethylene and polypropylene; propylene-olefin copolymer particles, first forming a homopolymer, A copolymer or a terpolymer particle layer, and a multilayered multicomponent particle obtained by applying another monomer layer to the above polymer particle layer, a siloxane polymer particle, a tetrafluoroethylene particle or the like.

Examples of the inorganic light-diffusing particles include calcium carbonate, barium sulfate, barium oxide, aluminum hydroxide, titanium oxide, zirconium oxide, magnesium fluoride, talc, glass, mica and the like. In general, organic particles have better light diffusibility than inorganic particles. In addition, at least two kinds of light-diffusing particles may be mixed if necessary.

When the surface layer further contains a light diffusing agent, the light diffusing effect can be further increased. In addition, the light-diffusing particles also protrude from the surface of the surface layer such that they emboss to exhibit a non-glossy surface and low reflectance. In this connection, the surface roughness of the surface layer is preferably about 0.1 to 50 μm. If the roughness exceeds 50 μm, the impact strength of the surface becomes insufficient. Conversely, if the roughness is less than 0.1 μm, the non-gloss effect will be degraded.

The content of the light diffusing agent in the substrate layer or the surface layer is 0.01 to 35 wt%, and preferably 0.5 to 15 wt%, based on the total weight of the resin base agent of the substrate layer or the surface layer of the present invention. When the content of the light diffusing agent is less than 0.01% by weight, it is difficult to achieve a sufficient light diffusing effect or a masking effect. On the other hand, when the content exceeds 35 wt%, the light transmittance is deteriorated. In this connection, the content of the light diffusing agent can be determined depending on the difference in refractive index from the resin main agent.

Further, the substrate layer or the surface layer may additionally contain a light stabilizer. Examples of light stabilizers include a UV absorber having a maximum absorption wavelength of 250 to 380 nm, or a radical scavenger such as a hindered amine UV stabilizer which maximizes the photostability effect. This component should exhibit this effect for a long time and must not separate or leave the sheet due to evaporation or extraction. The absorbent selected should be highly compatible with the substrate.

The ultraviolet absorber may be selected from the group consisting of cyanoacryl, salicylate, malonic acid ester, oxalic anilide, Diketone, hydroxyl benzophenone, hydroxy benzotriazole, organometallics, and mixtures thereof.

The UV stabilizer may be selected from the group consisting of: piperidinyl ester, oxazolidine and piperidino-oxazolidine, piperidinyl acetal (piperidispiroacetal), diazacycloalkanone, and mixtures thereof.

The light stabilizer may be used in an amount of 0.01 to 5 wt%, and preferably 0.1 to 2 wt%, based on the total weight of the resin composition of the substrate layer or the surface layer. In particular, when the surface layer contains such a component, the light stabilizing effect can be achieved without degrading the total light transmittance or physical properties of the substrate layer.

The light diffusing plate of the present invention can be used for a variety of indoor and outdoor applications. That is to say, the light diffusing plate can be applied to a signboard, a light-emitting signboard, a light-emitting cover, a glass display case, etc., but it is preferable to use a light diffusing plate as a display. An example of a light diffusing plate for a display is usually an LCD (liquid crystal display) backlight unit or a light diffusing plate for an edge-light-type backlight unit.

The invention may be further understood by the following examples of the invention, which are not to be construed as limiting the invention.

In the example, PC and PS were used as the resin main components of the substrate layer, and they were uniformly added in the composition ratio shown in Table 1, and then melt-kneaded at a temperature of 250 ° C using a twin-screw extruder.

In this connection, according to the ASTM D1238 standard, the polycarbonate resin has a melt index of 22 g/10 minutes at 300 ° C under a load of 1.2 kg. In addition, according to the ASTM D1238 standard, the melt index of the polystyrene resin at 200 ° C is 1.5 g/10 min under a load of 5 kg.

Further, the resin base agent of the surface layer is a polystyrene-acrylic copolymer resin obtained by polymethyl methacrylate, polystyrene, or copolymerization of an acrylic monomer and a styrene monomer according to a general process.

The light diffusing plate was formed by a co-extrusion process at a temperature of 250 ° C using an extruder having a screw diameter of 135 mm and 60 mm. In the case where the light diffusing plate is composed of only one substrate layer, the thickness of the substrate layer is 2.0 mm. However, when the light diffusion is additionally provided with the surface layer, that is, the surface layer is formed on one side surface of the substrate layer, the substrate layer has a thickness of 1.0 mm and the surface layer has a thickness of 0.1 mm.

In the composition of the light diffusing plate of each of the foregoing examples and comparative examples, the substrate layer is a resin main component shown in Table 1 and 0.2 part by weight of a beryllium resin (average particle size: 2 μm) as a light diffusing agent. B-cap (tetraethyl-2,2'-(1,4-phenylene-dimethylene)-bismalonic acid) as a UV absorber in 0.05 parts by weight in a light stabilizer (tetra-ethyl) -2,2'-(1,4-phenylene-dimethylidene)-bismalonate), the surface layer is composed of a resin base agent used for the surface layer, or the resin base agent and the fluororesin contained in the above table Or fluororesin particles, 2 parts by weight of ruthenium resin beads (average particle size: 2 μm) as a light diffusing agent and 0.5 parts by weight of B-cap (tetraethyl-2, 2' as a UV absorber in a light stabilizer -(1,4-Benzene-dimethylene)-bismalonic acid) is mixed and formed.

The light diffusing agents prepared in the foregoing examples and comparative examples were subjected to measurement of water absorption, bending, total light transmittance, haze, yellowing index, and heat deformation temperature. The results shown in Tables 5 to 8 are the results.

The water absorption rate was measured by first cutting the light diffusing plate to a size of 10 cm square, and then immersing it in water at 25 ° C for 24 hours. The bending method is performed by mounting the light diffusing plate on a 20-inch-sized backlight unit, allowing it to stand at a temperature of 60 ° C and a relative humidity of 75% for 96 hours, and then measuring the upward warpage of the light diffusing plate. The distance between the four corners and the surface of the backlight unit. The heat distortion temperature is measured in accordance with ASTM D648.

The yellowing index is based on the ASTM D1925 standard, using a Q-UV tester equipped with FS-40 313/280 fluorescent lamp, after 240 hours of exposure at 40 ° C, according to ASTM D1003 standard Make measurements. The total light transmittance and haze are also measured in accordance with ASTM D1003.

As is apparent from the results of the above respective properties, the light-diffusing sheet having only the substrate layer composed of the polycarbonate resin and the polystyrene resin mixture as the resin main component can be confirmed to have a higher temperature and high humidity. High shape stability, the only exception is the high yellowing index.

From the results of the above properties, it is understood that the substrate layer composed of a polycarbonate resin as a resin main component and a surface layer formed on one surface of the substrate layer, or the surface layer further containing a fluororesin or a fluororesin particle The diffuser plate confirms the high dimensional stability.

Therefore, when a polycarbonate resin is used as the resin base agent of the substrate layer, various light properties including shape stability can be seen, regardless of the type of the resin base agent used for the surface layer.

From the results of the above-mentioned properties, it is known that a substrate layer composed of a polycarbonate resin and a polystyrene resin mixture as a resin main component and a PMMA resin as a resin main agent on one surface of the substrate layer form a surface layer. The light diffusing plate can be confirmed to have superior shape stability and yellowing resistance.

Further, when the surface layer of the light diffusing plate further contains a fluororesin or a fluororesin particle, the shape stability is superior to that of a light diffusing plate which does not contain a fluororesin or a fluororesin particle. Further, when the amount of the fluororesin or the fluororesin particles is increased, the dimensional stability becomes better.

Therefore, when a polycarbonate resin and a relatively inexpensive polystyrene mixture are used as the resin base agent of the substrate layer, the dimensional stability is equivalent to or superior to that of the polycarbonate resin alone as the base resin of the substrate layer. The preparation cost can be reduced accordingly.

From the results of the above properties, it is known that a substrate layer composed of a polycarbonate resin and a polystyrene resin mixture as a resin main component and a surface layer formed by using an MS resin as a resin main component on one surface of the substrate layer The light diffusing plate can be confirmed to have superior shape stability.

Therefore, even if a relatively inexpensive polystyrene resin is mixed with a polycarbonate resin and used as a resin main component of the substrate layer, excellent shape stability can be exhibited, thereby reducing the production cost.

It can be seen from the results of the foregoing properties that the substrate layer of the light diffusing plate can be confirmed to have all properties including shape stability and yellowing resistance without containing a polycarbonate resin or a mixture of a polycarbonate resin and a polystyrene resin. Within, it will be reduced.

Therefore, since the light diffusing plate of the present invention comprises a substrate layer formed of a polycarbonate resin or a mixture of a polycarbonate resin and a polystyrene resin, it has superior total light transmittance and light diffusibility, particularly high heat resistance and Resistant to absorption, so that the shape stability is good. In addition, a polystyrene resin which is cheaper than polycarbonate resin is also used, so that the production cost is lowered.

Further, the light diffusing plate of the present invention further includes a surface layer so that an anti-yellowing effect can be exerted when it is irradiated with a light source for a long period of time.

Further, the surface layer of the light-diffusing sheet of the present invention further contains a fluororesin or a fluororesin particle so as to further improve the shape stability, and further reduce the yellowing index when irradiated with a light source for a long period of time, thereby producing a light-diffusing sheet having improved properties.

Industrial applicability

As described above, the present invention provides a light diffusing plate. Since the light diffusing plate of the present invention comprises a substrate layer using a polycarbonate resin as a main component of the resin, it has a high dimensional stability due to high absorption resistance, and can be reduced even under high temperature and high humidity conditions. The phenomenon of bending. In addition, a surface layer may be further provided, or the surface layer further contains a fluororesin or a fluororesin particle, so that the light diffusing plate has further improved shape stability, and the yellowing property is further reduced even when irradiated by the light source for a long time. .

The embodiments are intended to be illustrative only and not to limit the invention, and all modifications, additions and substitutions or substitutions may be made without departing from the spirit of the invention.

Claims (15)

A light diffusing plate comprising: a substrate layer having a mixture of a polycarbonate resin and a polystyrene resin as a resin base agent, wherein the mixture as a resin base agent is a polycarbonate resin and the polymer a styrene resin mixed in a weight ratio of 1:9 to 9:1; and a surface layer formed on one or both sides of the substrate layer, and containing an acrylic resin or a styrene-acrylic copolymer resin as a resin master And a fluororesin or fluororesin particles. The light diffusing plate according to claim 1, wherein the polycarbonate resin is selected from the group consisting of: reacting a dihydric phenol with phosgene or a dihydric phenol and a carbonate precursor. The linear and branched aromatic polycarbonate homopolymers were prepared. The light diffusing plate according to claim 1, wherein the polycarbonate resin has a melt index of 8 to 30 g/10 minutes at 300 ° C under a load of 1.2 kg in accordance with ASTM D1238. The light diffusing plate according to claim 1, wherein the polystyrene resin has a melt index of 0.5 to 3 g/10 minutes at 200 ° C under a load of 5 kg according to ASTM D1238 standard. . The light diffusing plate according to claim 1, wherein the acrylic resin is a homopolymer, a copolymer or a mixture thereof obtained from at least one selected from the group consisting of alkyl methacrylate Esters, alkyl acrylates, cycloalkyl methacrylates, cycloalkyl acrylates, aryl methacrylates, and aryl acrylates. The light diffusing plate according to claim 1, wherein the benzene An ethylene-acrylic copolymer resin composed of an alkyl methacrylate, an alkyl acrylate, a cycloalkyl methacrylate, a cycloalkyl acrylate, an aryl methacrylate, and an aryl acrylate. At least one acrylic monomer selected from the group, and a group consisting of styrene, α-methylstyrene, m-methylstyrene, p-methylstyrene, and p-methoxystyrene A copolymer of at least one styrene monomer selected. The light diffusing plate according to claim 1, wherein the styrene-acrylic copolymer resin is obtained by reacting an acrylic monomer and a styrene monomer in a weight ratio of 9:1 to 1:9. By. The light diffusing plate according to claim 1, wherein the styrene-acrylic copolymer resin is obtained by reacting an acrylic monomer and a styrene monomer in a weight ratio of 6:4 to 2:8. By. The light diffusing plate according to claim 1, wherein the substrate layer further comprises 0.1 to 35 wt% of a light diffusing agent based on the total weight of the composition. The light diffusing plate according to claim 1, wherein the substrate layer or the surface layer is based on the total weight of the respective components, and further comprises 0.1 to 35 wt% of a light diffusing agent. The light diffusing plate according to claim 9, wherein the light diffusing agent has a particle size of 0.2 to 50 μm. The light diffusing plate of claim 10, wherein the light diffusing agent has a particle size of 0.2 to 50 μm. The light diffusing plate of claim 10, wherein the surface layer has an embossed shape formed by the light diffusing agent protruding, and has Surface roughness from 1 to 50 μm. The light diffusing plate according to claim 1, wherein the substrate layer further comprises 0.01 to 5 wt% of a light stabilizer, based on the total weight of the composition. The light diffusing plate according to claim 1, wherein the substrate layer or the surface layer further comprises 0.01 to 5 wt% of a light stabilizer based on the total weight of the respective components.