KR20060021545A - Light diffusion plate - Google Patents

Abstract

The present invention relates to the manufacture of a light diffusion plate having a high total light transmittance and excellent light diffusion rate and weather resistance. The light diffusion plate according to the present invention comprises 0.1 to 5.0 parts by weight of a benzoguanamine light diffusing agent based on 100 parts by weight of a resin; And / or 0.1 to 10 parts by weight of one or more components selected from silicone based, crosslinked polymethyl methacryl based, crosslinked polystyrene based, calcium carbonate.

Light Diffusion Plate, Light Diffusion Agent, Total Light Transmittance, Light Diffusion, Weatherability

Description

Light Diffusion Plate

The present invention relates to the manufacture of a light diffusion plate having a high total light transmittance and excellent light diffusion rate and weather resistance.

Recently, a large liquid crystal display uses a plurality of light sources in the backlight unit to increase the brightness. The light diffusion plate is used to cover the appearance of these light sources and to uniformly diffuse the light from the light sources. Light diffusers generally impart concealment and diffusivity by using organic or inorganic diffusing agents in transparent resins. However, the concealment and diffusivity of the light source is improved as the amount of the diffusion agent is increased, but at the same time, the light transmittance (total light transmittance) is lowered, resulting in a decrease in luminance. In addition, as the number of light sources increases, yellowing may occur in the diffusion plate by ultraviolet rays emitted from the light source.

Japanese Patent Laid-Open Nos. 63-291001 and 63-291002 disclose the use of crosslinked organic diffusing agents having a specific range of refractive index differences and particle diameters in acrylic resins. However, in the case of using an organic diffusing agent, in order to obtain sufficient diffusibility, a large amount must be added, and the distribution of particles may be changed due to an uneven distribution of particles. In addition, in the case of the polystyrene-based diffusing agent, there is a disadvantage that yellowing occurs easily by ultraviolet rays emitted from a light source.

As inorganic diffusion agents, calcium carbonate, barium sulfate, titanium oxide, aluminum hydroxide, silica, glass, talc, mica, white carbon, magnesium oxide, zinc oxide, etc. can also be used. The manufactured diffusion plate has a disadvantage in that the hiding power of the light source falls.

On the other hand, Japanese Patent Laid-Open Nos. 1-172801 and 3-207743 disclose the use of silicon-based fine particles having a specific structure in order to increase weather resistance and diffusion rate.

An object of the present invention is to provide a method for producing a light diffusing plate which is excellent in light diffusivity, excellent in weatherability, and has no decrease in light transmittance.

A specific object of the present invention is a light diffusion plate prepared by adding 0.1 to 5.0 parts by weight of a benzoguanamine-based resin light diffusing agent based on 100 parts by weight of a transparent resin, the total light transmittance of 60% or more, 70% or more, It is to manufacture a light diffusion plate having a weather resistance ΔE (transmission) value of less than 1.5.

In order to achieve the above object of the present invention, the present invention was prepared by adding 0.1 to 5.0 parts by weight of a benzoguanamine resin light diffusing agent based on 100 parts by weight of the transparent resin used in the light diffusion plate.

The second invention according to the present invention is based on the inorganic resin such as 0.1 to 5.0 parts by weight of the benzoguanamine-based resin light diffusing agent with respect to 100 parts by weight of the transparent resin and silicone, cross-linked polymethyl methacryl, cross-linked polystyrene, calcium carbonate At least one light diffusing agent selected is prepared by adding 0.1 to 10 parts by weight of the transparent resin.

Although the use of the transparent resin of the optical diffuser used in the present invention is not particularly limited, a methyl methacrylate homopolymer or a copolymer of methyl methacrylate and other monomers is preferable. Other monomers include methyl acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, cyclohexyl (meth) acrylate, styrene, α-methyl styrene, maleic anhydride, phenylmaleimide and cyclohexylmaleic Mead and the like.

The benzoguanamine-based resin light diffusing agent used in the present invention is preferably a condensate of formaldehyde and benzoguanamine to add 0.1 to 5 parts by weight based on the resin 100. More preferably, 0.1 to 1.0 parts by weight is added. When the amount is 0.1 parts by weight or less, sufficient light diffusivity cannot be obtained. When the amount is 5 parts by weight or more, the light transmittance is lowered and the luminance is decreased. The average particle diameter of the benzoguanamine light diffusing agent is preferably 0.1 to 15 µm, and preferably 0.8 to 5 µm. In general, when the particle size is 0.1 μm or less, the diffusivity decreases and the content of the diffusing agent must be increased. When the particle size is 15 μm or more, the light transmittance decreases and the dispersibility with the resin also decreases.

In the present invention, benzoguanamine-based resins may be used alone or in combination with other diffusing agents. Other diffusing agents include silicone, crosslinked polymethyl methacryl, crosslinked polystyrene, calcium carbonate and the like, and are preferably silicon. The amount of the other light diffusing agent added is preferably 0.1 to 10 parts by weight with respect to the resin 100. When the amount of the light diffusing agent is 10 parts by weight or more, the light transmittance is lowered to reduce the luminance. More preferably, 0.1 to 2 parts by weight is added.

The light diffusing plate of the present invention also contains stearyl sulfate sodium salt, cetyl sulfate sodium salt, glycidyl monostearate, polyether esteramide as antistatic agent, and hindered phenolic, sulfur type, phosphorus and ultraviolet absorber as antioxidant. Benzophenone-based, cyanoacrylate-based, salicylate-based, benzotriazole-based, malonic ester-based, oxalanilide-based and the like can be added.

The amount of these additives is 0.1 to 1.0 parts by weight and preferably 0.1 to 0.5 parts by weight with respect to the resin 100 in the case of the antistatic agent. In the case of antioxidant, it is 0.1-5.0 weight part with respect to resin 100, Preferably it is 0.1-1.5 weight part. In the case of the ultraviolet absorber, it is 0.1 to 5.0 parts by weight and preferably 0.1 to 1.0 part by weight based on the resin 100. In the case of using less than the above range, the desired physical properties cannot be sufficiently obtained, and in the case of exceeding the above range, the light diffusion or the brightness is adversely affected.

As a method for producing the light diffusion plate, a batch casting method, a continuous casting method, a single layer extrusion method, or a coextrusion method may be used. Preferably, the light diffusion plate is a coextrusion method.

The coextrusion method is a method of manufacturing a diffusion plate by laminating resins. In the inner layer, 0.1 to 5.0 parts by weight of benzoguanamine-based resin and / or other diffusing agents and additives are dispersed in 100 parts by weight of the resin, and the outer layer is one of the inner layers. It is placed on either side or both sides, and generally, 5 to 15 parts by weight of the organic light diffusing agent is added to the resin 100 to impart matte properties. If the added amount is 5 parts by weight or less, sufficient matting properties cannot be obtained, and light reflection becomes severe, and if it is 15 parts by weight or more, the light transmittance is reduced.

The total thickness of the light diffusion plate is 0.5 to 10 mm and preferably 1 to 5 mm. 10-100 micrometers is preferable and, as for the thickness of an outer layer, 30-50 micrometers is more preferable. If the total thickness of the diffuser plate is 0.5 mm or less, the mechanical strength is low, so that the warpage of the diffuser plate can easily occur, and in the case of 10 mm or more, the amount of the diffusion agent is increased and the weight of the product increases. If the thickness of the outer layer is 10 µm or less, the surface roughness is severe, and light transmittance is decreased. If the thickness is 100 µm or more, the matness is inferior.

Hereinafter, the present invention will be described in more detail with reference to the following examples. Unless otherwise stated, the scope of the present invention is not limited thereto.

[Examples 1-4 and Comparative Examples 1-4]

0.1 parts by weight of light diffusing agent and glycidyl monostearate in the amounts shown in Table 1 with respect to 100 parts by weight of PMMA resin (methyl methacrylate: methyl acrylate 96/4 copolymer, LG MMA EG 920, molecular weight 120,000), 0.15 parts by weight of tris (2,4-di- (tert) -butylphenyl) phosphate (Irgafos 168, Ciba Specialties), 2- (2-hydrooxy-5-methyl-phenyl) benzotriazole (Tinuvin P, Ciba Specialties ) 0.05 parts by weight was mixed with a Henschel mixer and pelletized (A) after kneading in a twin screw extruder (cylinder temperature 190 to 235 ° C).

8 weights of polymethyl methacrylate crosslinked beads (GM 0806S, average particle diameter: 8 µm, Ganz) with respect to 100 parts by weight of MS resin (methyl methacrylate / styrene 60/40 copolymer, Cevian MAS-30, molecular weight 120,000) And 0.5 parts by weight of glycidyl monostearate, 0.2 parts by weight of tris (2,4-di- (tert) -butylphenyl) phosphate (Irgafos 168, Ciba Specialties), 2- (2-hydrooxy-5-methyl -Phenyl) Benzotriazole (Tinuvin P, Ciba Specialties) 0.5 parts by weight was mixed with a Henschel mixer and kneaded in a twin screw extruder (cylinder temperature 190 to 220 ° C) and pelletized (B).

The prepared pellet (A) is supplied to the center supply block (screw diameter 150, Omnipa) of the sheet extruder to form an inner layer, and the pellet (B) is supplied to the auxiliary supply block (screw diameter 65, Omnipa) to supply the outer layer. It was formed on both sides of the inner layer. Co-extrusion was performed at temperatures of 170, 170, 190, 220, 230, 230, 230 ° C, flange temperature 230 ° C, adapter temperature 230 ° C, and die temperature 230 ° C, respectively, 900 mm wide and 2 mm thick (inner layer thickness 1.9). mm and 0.05 mm each of both sides of the outer layer thickness were prepared. The total light transmission (Tt) of the manufactured light diffusion plate was measured using HR-100 of Murakami Color Research Laboratory according to JIS K-7105, and the light diffusion factor (DF) was defined by the following equation. Become,

DF = 100 x (luminance in 20 ° direction for 0 ° transmitted light) + (luminance in 70 ° direction for 0 ° transmitted light) / (luminance in 5 ° direction for 0 ° transmitted light)

It was measured using GC 5000L of Nippon Denshoku. Weather resistance was used by ATLAS-UVCON, and ultraviolet light was continuously irradiated on the specimen (4 cm x 8 cm) for 200 hours at a temperature of 60 ℃. L *, a *, b * values for the transmitted light were measured in accordance with JIS K-7103 before and after irradiation using a spectrophotometer (Color-Eye 3100 manufactured by GretagMacbeth) to obtain the ΔE values. The relationship between ΔE, L *, a *, and b * values is as follows.

ΔE = [L (1) *-L (0) * 2 + a (1) *-a (0) * 2 + b (1) *-b (0) * 2] 1/2

L (0) *, a (0) *, b (0) * are the pre-irradiation measurements, and L (1) *, a (1) *, b (1) * are the post-irradiation measurements.

From the results of Table 1, when benzoguanamine-based resin or benzoguanamine-based resin / silicone diffuser is used (Examples 1 to 4), the total light transmittance (Tt) is 66.9 to 74.2% and the light diffusivity (DF) is 71.5 to 88.2% showed excellent transmittance and diffusion rate. Moreover, (DELTA) E value which is a measure of weather resistance showed the numerical value of 0.9-1.0, and was stable also to ultraviolet-ray.

On the other hand, when crosslinked polymethyl methacrylate alone or crosslinked polymethyl methacrylate / silicone diffuser was used (Comparative Examples 1 and 2), the excellent light transmittance and weather resistance were excellent, but the light diffusion did not provide sufficient light diffusion characteristics. On the other hand, in the case of using the crosslinked polystyrene diffusing agent (Comparative Examples 3 and 4), excellent diffusivity was obtained, but total light transmittance was decreased and weatherability was poor, resulting in yellowing.

TABLE 1

Benzoguanamine-based resin: Nippon Catalyst Co., Ltd., Epostar MS, average particle size 1.5 탆

Silicone: Nikko Rica MSP-S020, average particle size 2㎛

Crosslinked methyl methacrylate type: Sekisui, MBX-6, normal particle size 6㎛

Crosslinked polystyrene: Sekisui, SBX-6, average particle size 6 µm

The present invention contains 0.1 to 1.0% of a benzoguanamine-based resin light diffusing agent, so that the total light transmittance of the light diffusing plate is higher, and the light diffusing rate and weather resistance are superior to those of the conventional organic light diffusing agent or inorganic light diffusing agent. It can be seen that it has an effect.

Claims (12)

A light diffusion plate using 0.1 to 5 parts by weight of a benzoguanamine-based resin light diffusing agent having an average particle diameter of 0.1 to 15 µm with respect to 100 parts by weight of the transparent resin. The light diffusion plate of claim 1, wherein the transparent resin is a methyl methacrylate homopolymer or a copolymer. The copolymer of claim 2 wherein the copolymer is methyl methacrylate and methyl acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, cyclohexyl (meth) acrylate, styrene, α-methyl styrene, anhydrous A light diffusion plate, characterized in that a copolymer polymerized with at least one component selected from maleic acid, phenylmaleimide and cyclohexylmaleimide. The light diffusing plate according to claim 1, wherein the benzoguanamine-based resin which is the light diffusing agent is a condensate of formaldehyde and benzoguanamine. The light diffusing plate of claim 4, wherein the light diffusing agent further mixes 0.1 to 10 parts by weight of at least one other light diffusing agent selected from silicon, crosslinked polymethylmethacryl, crosslinked polystyrene and calcium carbonate. . The method of claim 4, wherein the transparent resin 100 further comprises at least one additive component selected from 0.1 to 1.0 parts by weight of antistatic agent, 0.1 to 5.0 parts by weight of antioxidant, 0.1 to 5.0 parts by weight of ultraviolet absorber. Light diffusion plate. The method of claim 5, wherein the transparent resin 100 further comprises at least one additive component selected from 0.1 to 1.0 parts by weight of antistatic agent, 0.1 to 5.0 parts by weight of antioxidant, 0.1 to 5.0 parts by weight of ultraviolet absorber. Light diffusion plate. The light diffusion plate according to any one of claims 1 to 7, wherein the total light transmittance is 60% or more, the light diffusion rate is 70% or more, and the weather resistance ΔE (transmission) value is less than 1.5. Methyl methacrylate homopolymer or methyl methacrylate and methyl acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, cyclohexyl (meth) acrylate, styrene, α-methyl styrene, maleic anhydride Inner layer in which 0.1 to 5 parts by weight of benzoguanamine-based resin is dispersed with respect to 100 parts by weight of the copolymer transparent resin polymerized with at least one component selected from an acid, phenylmaleimide and cyclohexyl maleimide, and one side of the inner layer or Laminated light diffuser plate composed of an outer layer which is placed on both sides and dispersed with 8 to 15 parts by weight of any one or more components selected from silicone-based, cross-linked poly methyl methacryl-based or cross-linked polystyrene-based organic light diffusing agent with respect to the polymer transparent resin 100. 10. The laminated light diffusion device of claim 9, wherein the benzoguanamine-based resin has an average particle diameter of 0.1 to 15 µm, a laminated light diffusing plate having a total thickness of 0.5 to 10 mm, and an outer layer having a thickness of 10 to 100 µm. plate. The light diffusing plate according to claim 9 or 10, wherein the total light transmittance is 60% or more, the light diffusivity is 70% or more, and the weather resistance ΔE (transmission) value is less than 1.5. a) preparing a pellet by kneading a resin mixture in which 0.1 to 5 parts by weight of a benzoguanamine-based resin is dispersed with respect to 100 parts by weight of a transparent resin; b) pellets are prepared by kneading a resin mixture in which 8 to 15 parts by weight of any one or more components selected from silicone-based, cross-linked polymethyl methacryl-based or cross-linked polystyrene-based organic light diffusing agent is dispersed in a twin screw extruder. Doing; c) supplying the pellets prepared in a) to the central feed block of the sheet extruder to form an inner layer, and supplying the pellets prepared in b) to the auxiliary feed block of the sheet extruder to form an outer layer to extrude the sheet ; Method for producing a laminated light diffuser plate, characterized in that the manufacturing.