KR100725827B1 - Light-diffusion plate - Google Patents

Abstract

A light-diffusion plate is provided to obtain high dimension stability with high heat-resistance and absorption-resistance by using a base resin as a mixture of a polycarbonate resin and a polystyrene resin. A light-diffusion plate includes a base layer and a surface layer. The base layer includes a first base resin as a mixture of a polycarbonate resin and a polystyrene resin. The surface layer includes a second base resin of an acrylic resin and a fluorine-based resin. The surface layer is formed on one side or both sides of the base layer. In the first base resin, a mixing ratio of the polycarbonate resin to the polystyrene resin is 1:9 to 9:1.

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.

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 When the temperature is changed by turning off, the water absorption rate of the light diffusing 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 addition, a light diffusion plate using a polycarbonate resin having excellent dimensional stability due to relatively high light transmittance and high heat resistance and high water absorption is proposed, but in the case of a light diffusion plate to which a polycarbonate resin is applied, high heat resistance and water absorption By the high dimensional stability but low light resistance there is a problem that yellowing phenomenon occurs when exposed to a light source for a long time.

On the other hand, polystyrene is a polymer of styrene and is a colorless and transparent thermoplastic, which is strong in acids, alkalis, oils, alcohols, etc., has excellent electrical properties, does not absorb water, is hard and has high strength, but is weak in impact and heat resistant. There is a small problem.

In order to compensate for the disadvantages of polycarbonate resins, polystyrene resins can be used to produce excellent light diffusing plates, but in general, polymer materials are not mixed with each other, and side effects such as phase separation occur. It was.

The present inventors use the polycarbonate resin and the polystyrene resin as a base resin, and exhibit yellow phenomena even when exposed to a light source for a long time with light resistance of the surface layer while showing high dimensional stability due to high heat resistance and low water absorption even at high temperature and wet conditions. Experiments confirmed that it can provide a light diffusion plate that does not come to complete the present invention.

Therefore, the present invention improves the dimensional stability by applying a fluorine resin, thereby providing a light diffusion plate having excellent optical characteristics and no yellowing phenomenon without warping in high temperature and high humidity environments, and also having a low matt surface. An object of the present invention is to provide a light diffusion plate exhibiting reflective characteristics.

The present invention for achieving the above object is a base layer comprising a first base resin mixed with a polycarbonate resin and a polystyrene resin; And a second base resin and a fluorine resin of acrylic resin, and providing a light diffusion plate including surface layers formed on one or both surfaces of the base layer.

The first base resin is characterized in that the mixing ratio of the polycarbonate resin and the polystyrene resin is 1: 9 to 9: 1.

The polycarbonate resin is characterized in that the melt index (MI) is 8 ~ 30 g / 10min at 300 ℃, 1.2kg load under the conditions of ASTM D1238.

The polystyrene resin is characterized in that the melt index (MI) at 200 ℃, 5kg load under the conditions of ASTM D1238 is 0.5 ~ 3 g / 10min.

The first base resin is produced by melt kneading a polycarbonate resin and a polystyrene resin at an molding temperature of 200 ~ 300 ℃ using an extruder.

The fluorine-based resin 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.

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

The substrate layer of the light diffusion plate of the present invention was prepared by mixing a polycarbonate resin and a polystyrene resin as the first base resin. This is because the polycarbonate resin has a disadvantage in that it is rather expensive and has low light resistance despite the impact resistance, water absorption and light transmittance of the polycarbonate resin. This is to reinforce rigidity and to maintain and improve optical and mechanical properties while reducing raw material costs in manufacturing cost.

The polycarbonate resin used to prepare the first base resin has excellent impact resistance and light transmittance, good cold resistance and electrical properties, and particularly has high heat resistance, and thus has excellent dimensional stability, and thus has wide use temperature range. It is used in lenses, optical disc materials, helmets, protective equipment, covers, and the like.

The polycarbonate resins used in the present invention are aromatic polycarbonate resins which are generally used, and linear and branched carbonate homopolymers and polypolymers prepared by reacting dihydroxy phenol with phosgene or by reaction of dihydroxy phenol with a carbonate precursor. Ester copolymers or mixtures of one or more thereof. The dihydroxy phenol is 2,2-bis (4-hydroxyphenyl) propane (ie bisphenol A), bis (4-hydroxy phenyl) methane, 2,2-bis (4-hydroxy-3,5 -Dimethylphenyl) propane and 1,1-bis (4-hydroxyphenyl) cyclohexane and the like, and the carbonate precursors include diphenyl carbonate, carbonyl halide and diaryl carbonate.

The polycarbonate resin has a melt index (MI) of 8 ~ 30 g / 10min at a load of 1.2 ℃ 300 ℃, ASTM D1238 standard conditions. If the low-viscosity polycarbonate resin of 30g / 10min or more, workability and melt mixing are very poor, which makes it difficult to manufacture a light diffusion plate.

The polystyrene resin used to manufacture the first base resin is hard, colorless, transparent, has good electrical properties, and is cheap in mass production, so kitchen products, stationery, furniture, daily necessities such as furniture, TV cabinets for automobiles, etc. It is used in many places such as telecommunications products.

The polystyrene resin used in the present invention uses a melt index (MI) of 0.5 to 3 g / 10min at a load of 200 ° C and 5 kg, which is a condition of ASTM D1238. If more than 3g / 10min, melt mixing is difficult due to the large viscosity difference with the polycarbonate resin.

The polycarbonate resin and the polystyrene resin are manufactured by melt kneading at 250 ° C. with a motor speed of 250 rpm using a twin screw extruder having a screw diameter of 30 mm.

At this time, the mixing ratio of the polycarbonate resin and the polystyrene resin is 1: 9 to 9: 1, because the advantage of the flexibility, light resistance and dimensional stability of the polycarbonate, and the advantage of high absorption and strength of polystyrene In order to save the mixing of each content to be at least 10% or more. Accordingly, when 90% or more of polystyrene is added, dimensional stability is lowered, and there is a problem in light resistance. In addition, by reducing the amount of addition of the diffusing agent due to the difference in refractive index between the resin and the diffusing agent, it is expected to contribute to the cost improvement side.

On the other hand, the present invention includes a surface layer formed on one side or both sides of the base layer. The surface layer includes an acrylic resin having excellent properties in light transmittance, light resistance, and the like as the second base resin. Acrylic resins used as the second base resin include methacrylic acid alkyl esters such as methyl methacrylate, ethyl methacrylate, butyl methacrylate and 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 any one homopolymer or their copolymers chosen from acrylic acid aryl esters, such as phenyl acrylate and benzyl acrylate.

On the other hand, the surface layer of this invention contains fluorine resin in acrylic resin.

Fluorine-based resins have excellent thermal stability and electrical properties, and are excellent in chemical durability, weather resistance, light resistance and oxygen resistance, and in particular, have almost no water absorption rate, high heat resistance, high use temperature of 250 ~ 300 ℃, and excellent surface friction. Currently, it is applied to various valves, pumps, tanks, filters, pipes, cables, computers, and aerospace industries.

In particular, the fluorine resin applied in the present invention is a tetrafluoroethylene (TFE) homopolymer, a copolymer of tetrafluoroethylene and perfluoropropyl ether (PFA), tetrafluoroethylene (TFE) and hexafluoropropylene At least one selected from a copolymer of (HFP), a copolymer of tetrafluoroethylene and ethylene (ETFE), and a copolymer of vinylidene fluoride (VDF) and tetrafluoroethylene (TFE) is preferable. The application of the fluorine-based resin has a light diffusing function and excellent water repellency.

The content of the fluorine-based resin contained in the surface layer is 0.5 to 50 parts by weight, preferably 5 to 20 parts by weight based on 100 parts by weight of the base resin of the surface layer. If the amount of the fluorine-based resin is less than 0.5 parts by weight, a sufficient water repellent effect cannot be obtained, and if it is more than 50 parts by weight, it is disadvantageous in light transmittance.

The substrate layer may further include a light diffusing agent, which 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. At this time, 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 should be included 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; Multi-layered multicomponent particles, siloxane-based polymer particles, tetrafluoroethylene-based particles formed by forming copolymer particles of acryl and olefin, particles of the homopolymer, copolymer or terpolymer, and then covering the layers with other monomers. Particles and the like.

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. The light diffusing agent is further included in the surface layer to further increase the light diffusing effect, and the light diffusing particles protrude to the surface of the surface layer to have an embossed shape, thereby achieving an effect of having a matte surface and a 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 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.

Meanwhile, in the present invention, a light stabilizer may be added to the base layer or the surface layer, and the light stabilizer may be added as an ultraviolet absorber and a radical scavenger having a maximum absorption wavelength in the range of 250 nm to 380 nm to maximize the light stabilizer effect. UV stabilizers of hindered amines which can be used 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 can be used in combination.

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 to 5 parts by weight, preferably 0.1 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.

When the light diffusion plate of the present invention forms a surface layer on one surface or both surfaces of the substrate layer, it can be produced by a method such as coextrusion molding, lamination, thermal bonding, surface coating, etc., which are well-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 14 and Comparative Example 3 are as shown in the following [Table 1] and [Table 2], [Table 1] is the composition and composition ratio constituting the base layer of the light diffusion plate, [Table 2 ] Relates to the composition and composition ratio constituting the light diffusion plate.

The first base resins of the base material layers of Examples 1 to 14 and Comparative Example 3 were uniformly charged with polycarbonate and polystyrene in the composition ratios of the following [Table 1] and melt kneaded at a temperature of 250 ° C. with a twin screw extruder.

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

Examples 1 to 7 are for the two-layer light diffusion plate in which the content of the polycarbonate and polystyrene resin of the substrate layer is fixed, the surface layer is formed on one surface of the substrate layer, and the content of the fluorine resin particles mixed in the surface layer is varied. will be. Examples 8 to 14 form a base layer and a surface layer with the same composition as Examples 1 to 7, form a surface layer on both sides of the base layer, and varying the content of the fluorine-based resin in the surface layer will be. In Comparative Example 3, a surface layer was formed on one surface of the substrate layer.

At this time, 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 7 and Comparative Example 3 had a thickness of the substrate layer of 1.9 mm and a thickness of the surface layer. Was 0.1 mm, and Examples 8 to 14 had a thickness of the substrate layer of 1.8 mm and a thickness of the surface layer of both surfaces of 0.1 mm.

PC PS PMMA Example 1 Example 8 100 parts by weight 100 parts by weight - Example 2 Example 9 100 parts by weight 100 parts by weight - Example 3 Example 10 100 parts by weight 100 parts by weight - Example 4 Example 11 100 parts by weight 100 parts by weight - Example 5 Example 12 100 parts by weight 100 parts by weight - Example 6 Example 13 100 parts by weight 100 parts by weight - Example 7 Example 14 100 parts by weight 100 parts by weight - Comparative Example 3 - - 100 parts by weight * PC: Polycarbonate (Polycarbonate reacted with 2,2-bis (4-hydroxyphenyl) propane and phosgene), LG Dow, Caliber 300-22 * PS: Polystyrene, Toyo, HRM40 * PMMA: Polymethyl methacrylate, Mitsubishi-Rayon VH-001

Substrate layer Surface layer First base resin of the composition by Table 1 Light diffusing agent Light stabilizer 2nd base resin Fluorine resin Light diffusing agent Light stabilizer Example 1 Example 8 100 parts by weight 0.2 parts by weight of silicon beads 0.05 parts by weight of B-Cap PMMA 100 parts by weight 1 part by weight of TEF resin 4 parts by weight of silicon beads 0.5 parts by weight of B-Cap Example 2 Example 9 100 parts by weight 0.2 parts by weight of silicon beads 0.05 parts by weight of B-Cap PMMA 100 parts by weight 10 parts by weight of TEF resin 4 parts by weight of silicon beads 0.5 parts by weight of B-Cap Example 3 Example 10 100 parts by weight 0.2 parts by weight of silicon beads 0.05 parts by weight of B-Cap PMMA 100 parts by weight 30 parts by weight of TEF resin 4 parts by weight of silicon beads 0.5 parts by weight of B-Cap Example 4 Example 11 100 parts by weight 0.2 parts by weight of silicon beads 0.05 parts by weight of B-Cap PMMA 100 parts by weight 50 parts by weight of TEF resin 4 parts by weight of silicon beads 0.5 parts by weight of B-Cap Example 5 Example 12 100 parts by weight 0.2 parts by weight of silicon beads 0.05 parts by weight of B-Cap PMMA 100 parts by weight 70 parts by weight of TEF resin 4 parts by weight of silicon beads 0.5 parts by weight of B-Cap Example 6 Example 13 100 parts by weight 0.2 parts by weight of silicon beads 0.05 parts by weight of B-Cap PMMA 100 parts by weight 100 parts by weight of TEF resin 4 parts by weight of silicon beads 0.5 parts by weight of B-Cap Example 7 Example 14 100 parts by weight 0.2 parts by weight of silicon beads 0.05 parts by weight of B-Cap PMMA 100 parts by weight 300 parts by weight of TEF resin 4 parts by weight of silicon beads 0.5 parts by weight of B-Cap Comparative Example 3 100 parts by weight 0.2 parts by weight of silicon beads 0.05 parts by weight of B-Cap PC 100 parts by weight 100 parts by weight of TEF resin 4 parts by weight of silicon beads 0.5 parts by weight of B-Cap * Silicon Bead: Silicone Resin Bead * TFE Resin: Tetrafluoroethylene Resin * B-Cap: Tetra-ethyl-2,2 '-(1,4-phenylene-dimethylidene) -bismalonate, UV absorber

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 3 below.

Here, the water absorption rate was measured by cutting the light diffusion plate into 10 × 10 ㎝ and leaving it in water at 25 ° C. for 24 hours, and then measuring the water absorption from the change in weight. 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 at 40 ℃ for 240 hours in a Q-UV tester equipped with FS-40 313/280 according to ASTM D1925 standard. Was measured.

Water absorption rate (%) Dimensional change amount (%) Total light transmittance (%) Heat Deflection Temperature (℃) Haze (%) Yellowness after exposure (△ YI) Example 1 0.219 0.23 71.5 103.4 99.5 1.43 Example 2 0.209 0.22 70.1 104.5 99.4 1.40 Example 3 0.156 0.20 71.6 103.8 99.2 1.40 Example 4 0.145 0.19 70.6 104.6 99.3 1.38 Example 5 0.132 0.18 69.7 103.4 99.5 1.39 Example 6 0.095 0.14 69.7 104.3 99.6 1.37 Example 7 0.090 0.13 69.0 104.5 99.1 1.36 Example 8 0.217 0.23 71.1 103.4 99.1 1.42 Example 9 0.207 0.21 70.9 102.6 99.3 1.41 Example 10 0.154 0.19 70.4 103.5 99.2 1.39 Example 11 0.143 0.18 70.3 103.7 99.5 1.37 Example 12 0.132 0.17 69.5 102.4 99.1 1.36 Example 13 0.093 0.13 69.8 103.6 99.3 1.35 Example 14 0.089 0.12 69.2 104.7 99.5 1.34 Comparative Example 3 0.321 0.27 69.8 98.5 99.3 22.47

As a result of the physical property evaluation, it can be seen that in Examples 1 to 14 according to the present invention, the water absorption rate and the warpage phenomenon were very excellent compared to Comparative Example 1 in which the surface layer did not contain the fluorine-based resin, and yellowing was also low.

In addition, as in Examples 1 to 7 and 8 to 14, it can be seen that as the content of the fluorine-based resin increases in the surface layer, the water absorption rate is improved, so that the dimensional stability of the warpage does not occur in a high temperature and high humidity environment.

In Examples 8 to 14, the addition of fluorine-based resins to both surfaces of the surface layer showed a lower water absorption than the cross sections of Examples 1 to 7, thereby reducing the amount of dimensional change in humid conditions. .

In the case of Comparative Example 3, even though the same fluorine-based resin was added to the surface layer, PMMA was used as the base layer resin, and thus it was found to be weak in heat, very high yellowing rate, or high water absorption.

On the other hand, Examples 1 'to 14' and Comparative Examples 1 'to 3' of [Table 4] have different types of fluorine-based resins in the configuration of the base layer and the surface layer having the compositions shown in [Table 1] and [Table 2]. will be. In this case, silicon bead particles were included as the light diffusing agent, and the physical property measurement method was as described above.

The result of measuring the physical properties while changing the content of the tetrafluoroethylene-hexafluoropropylene copolymer resin is shown in [Table 5].

Substrate layer Surface layer First base resin of the composition by Table 1 Light diffusing agent Light stabilizer 2nd base resin Fluorine Resin Light diffusing agent Light stabilizer Example 1 ′ Example 8 ′ 100 parts by weight 0.2 parts by weight of silicon beads 0.05 parts by weight of B-Cap PMMA 100 parts by weight 1 part by weight of TEF-HFP resin 4 parts by weight of silicon beads 0.5 parts by weight of B-Cap Example 2 ′ Example 9 ′ 100 parts by weight 0.2 parts by weight of silicon beads 0.05 parts by weight of B-Cap PMMA 100 parts by weight 10 parts by weight of TEF-HFP resin 4 parts by weight of silicon beads 0.5 parts by weight of B-Cap Example 3 ′ Example 10 ′ 100 parts by weight 0.2 parts by weight of silicon beads 0.05 parts by weight of B-Cap PMMA 100 parts by weight 30 parts by weight of TEF-HFP resin 4 parts by weight of silicon beads 0.5 parts by weight of B-Cap Example 4 ′ Example 11 ′ 100 parts by weight 0.2 parts by weight of silicon beads 0.05 parts by weight of B-Cap PMMA 100 parts by weight 50 parts by weight of TEF-HFP resin 4 parts by weight of silicon beads 0.5 parts by weight of B-Cap Example 5 ′ Example 12 ′ 100 parts by weight 0.2 parts by weight of silicon beads 0.05 parts by weight of B-Cap PMMA 100 parts by weight TEF-HFP resin 70 parts by weight 4 parts by weight of silicon beads 0.5 parts by weight of B-Cap Example 6 ′ Example 13 ′ 100 parts by weight 0.2 parts by weight of silicon beads 0.05 parts by weight of B-Cap PMMA 100 parts by weight 100 parts by weight of TEF-HFP resin 4 parts by weight of silicon beads 0.5 parts by weight of B-Cap Example 7 ′ Example 14 ′ 100 parts by weight 0.2 parts by weight of silicon beads 0.05 parts by weight of B-Cap PMMA 100 parts by weight 300 parts by weight of TEF-HFP resin 4 parts by weight of silicon beads 0.5 parts by weight of B-Cap Comparative Example 3 ′ 100 parts by weight 0.2 parts by weight of silicon beads 0.05 parts by weight of B-Cap PC 100 parts by weight 100 parts by weight of TEF-HFP resin 4 parts by weight of silicon beads 0.5 parts by weight of B-Cap * Silicone Beads: Silicone Resin Beads * TEF-HFP Resin: Tetrafluoroethylene-hexafluoropropylene Copolymer Resin * B-Cap: Tetra-ethyl-2,2 '-(1,4-phenylene-dimethylidene) -bismalonate, UV absorbers

Water absorption rate (%) Dimensional change amount (%) Total light transmittance (%) Heat Deflection Temperature (℃) Haze (%) Yellowness after exposure (△ YI) Example 1 ' 0.217 0.23 71.4 103.8 99.4 1.43 Example 2 ' 0.210 0.21 70.1 104.5 99.4 1.41 Example 3 ′ 0.154 0.18 71.3 103.6 99.2 1.39 Example 4 ' 0.126 0.17 70.6 104.3 99.3 1.37 Example 5 ' 0.108 0.16 69.9 103.6 99.3 1.36 Example 6 ' 0.095 0.15 70.5 104.3 99.6 1.34 Example 7 ' 0.048 0.13 69.4 104.7 99.1 1.32 Example 8 ' 0.218 0.22 70.6 103.4 99.5 1.42 Example 9 ' 0.201 0.20 70.7 103.7 99.3 1.40 Example 10 ' 0.151 0.17 70.4 103.4 99.2 1.37 Example 11 ' 0.124 0.16 70.5 103.7 99.3 1.35 Example 12 ' 0.106 0.14 70.8 103.6 99.1 1.34 Example 13 ' 0.086 0.12 69.9 104.2 99.3 1.33 Example 14 ' 0.038 0.10 69.2 104.6 99.2 1.33 Comparative example 3 ' 0.322 0.24 69.7 98.8 99.2 22.75

As a result of evaluating the physical properties, in the case of Examples 1 'to 14' according to the present invention, the water absorption rate and the warpage phenomenon were higher than those of Comparative Examples 1 'and 2' in which the tetrafluoroethylene-hexafluoropropylene copolymer resin was not included in the surface layer. It was very good and yellowing was also low.

In addition, as in Examples 1 'to 7' and 8 'to 14', as the amount of tetrafluoroethylene-hexafluoropropylene copolymer resin added to the surface layer from 1 to 300 parts by weight is increased, the water absorption rate is improved and high temperature is achieved. In addition, it can be seen that the dimensional stability of the warpage does not occur in a high humidity environment.

In Examples 8 'to 14', the addition of fluorine resin to both surfaces of the surface layer showed a lower water absorption than the cross sections of Examples 1 'to 7', which had the effect of reducing the amount of dimensional change in humid conditions. It can be seen.

In the case of Comparative Example 3 ', it can be seen that even though the same fluorine-based resin was added to the surface layer, PMMA was used as the base layer resin, and thus it was weak to heat, very high yellowing rate, or high water absorption.

As a result of the physical properties and results, the light diffusion plate of the present invention mixed two different types of resins as base resins, but did not phase separate from each other and acted as a single material. And it can be seen that using a fluorine-based resin can provide a light diffusion plate having excellent physical properties in terms of optical and dimensional stability.

Therefore, the light diffusing plate of the present invention is excellent in total light transmittance and light diffusivity, in particular, it is excellent in high heat resistance and water absorption rate, excellent in dimensional stability, and low yellowing degree even when exposed to a light source for a long time.

As described above, the light diffusing plate of the present invention is melt-kneaded polycarbonate resin and polystyrene resin which can be complemented to each other and used as a base resin, and thus has high dimensional stability with high heat resistance and absorption resistance, even in an environment of high temperature and high humidity. There was no warpage, and even when exposed to a light source for a long time by the acrylic resin of both surface layers provided a light diffusion plate having a low yellowing degree and excellent optical properties including total light transmittance.

Claims (6)

A base layer comprising a first base resin mixed with a polycarbonate resin and a polystyrene resin; And A light diffusing plate comprising a second base resin of the acrylic resin and a fluorine resin, the surface layer formed on one side or both sides of the base layer. The method of claim 1, The first base resin is a light diffusion plate, characterized in that the mixing ratio of polycarbonate resin and polystyrene resin is 1: 9 to 9: 1. The method of claim 1, The polycarbonate resin is a light diffusion plate, characterized in that the melt index (MI) of 8 ~ 30 g / 10min at 300 ℃, 1.2kg load under the conditions of ASTM D1238. The method of claim 1, The polystyrene resin is a light diffusion plate, characterized in that the melt index (MI) is 0.5 ~ 3 g / 10min at 200 ℃, 5kg load under the conditions of ASTM D1238. The method of claim 1, The first base resin is a light diffusion plate, characterized in that the polycarbonate resin and polystyrene resin was manufactured by melt kneading at a molding temperature of 200 ~ 300 ℃ using an extruder. The method of claim 1, The fluororesin of the surface layer is a tetrafluoroethylene (TFE) homopolymer, a copolymer of tetrafluoroethylene and perfluoropropyl ether (PFA), tetrafluoroethylene (TFE) and hexafluoropropylene (HFP) Light diffusion plate, characterized in that at least one selected from copolymers of tetrafluoroethylene and ethylene (ETFE), vinylidene fluoride (VDF) and tetrafluoroethylene (TFE) .