KR20100070143A - Thermoplastic resin composition for light guide plate with improved humidity resistance and light stabilaty and the light guide plate manufactured by the resin composition - Google Patents

Abstract

PURPOSE: A thermoplastic resin composition, and a light guide plate manufactured therefrom are provided to reduce the generation of the curve by moisture, to improve the light-proof property of the light guide plate, and to prevent the efflorescence. CONSTITUTION: A thermoplastic resin composition contains a methyl methacrylate-styrene copolymer, a benzotriazole-based ultraviolet-absorbing agent, and a hindered amine photo-stabilizer. The methyl methacrylate-styrene copolymer contains 50~80 parts of styrene monomer by weight for 100 parts of copolymer by weight. The styrene monomer is selected from the group consisting of styrene, a-methylstyrene, m-methylstyrene, p-methylstyrene, and p-methoxystyrene. The benzotriazole-based ultraviolet-absorbing agent selected from the group consisting of 2-(2H-benzotriazol-2-yl)-p-cresol, 2-(2H-benzotriazole-2-yl)-4-(1,1,3,3-tetramethylbutyl)phenol, or 2,2'-methylenebis(6-(2H-benzotriazole-2-yl)-4-1,1,3,3-tetramethylbutyl) phenol.

Description

Thermoplastic resin composition for light guide plate having excellent moisture resistance and light resistance, and a light guide plate manufactured using the resin composition.

The present invention relates to a thermoplastic resin composition for a light guide plate and a light guide plate manufactured using the resin composition, and more particularly, excellent moisture resistance and light resistance that can be used as a raw material of a light guide plate, which is one of the main components of a backlight of a liquid crystal display device. It relates to a resin composition.

The light guide plate for backlight is a plate-shaped molded body having a function of transmitting light so as to convert the line light source emitted from the side of the light guide plate into a surface light source from which light is emitted from the entire front surface of the plate. Therefore, since the transmission length of the light is relatively long, it is necessary to use a material having high transmittance and low light loss.

Polymethyl methacrylate has been mainly used as a raw material for light guide plates. Polymethyl methacrylate is used as a raw material for various optical parts because of its high light transmittance in the visible light region, small birefringence and excellent light resistance. However, in the case of the light guide plate made of polymethyl methacrylate due to its high hygroscopicity, dimensional change and warpage due to moisture absorption may occur, and the phenomenon of whitening may occur.

In order to solve the warpage and the whitening phenomenon caused by the moisture absorption, it has been proposed to copolymerize methyl methacrylate and styrene monomer to apply to the light guide plate (Korea Patent Publication No. 2001-0095111), but the moisture resistance and light resistance The lack of improvement is insufficient for the light guide plate.

The present invention is to solve the above problems, by mixing a suitable amount of the benzotriazole ultraviolet absorber and the hindered amine light stabilizer in the base resin prepared by copolymerizing methyl methacrylate and styrene monomer in a specific ratio, It is an object to provide a resin composition for light guide plates excellent in wettability and light resistance.

Another object of the present invention is to provide a light guide plate manufactured using the resin composition.

The present invention is to achieve the above object, and includes a methyl methacrylate-styrene copolymer, a benzotriazole-based ultraviolet light absorber, and a hindered amine light stabilizer, and the styrene of the methyl methacrylate-styrene copolymer The content is 50 to 80 parts by weight based on 100 parts by weight of the methyl methacrylate-styrene copolymer provides a thermoplastic resin composition for a light guide plate.

In addition, the styrene monomer is characterized in that at least one selected from styrene, a-methyl styrene, m-methyl styrene, p-methyl styrene, and p- methoxy styrene.

In addition, the benzotriazole UV absorber is 2- (2H-benzotriazol-2-yl) -p-cresol, 2- (2H-benzotriazol-2-yl) -4- (1,1,3, 3-tetramethylbutyl) phenol or 2,2'-methylenebis (6- (2H-benzotriazol-2-yl) -4-1,1,3,3-tetramethylbutyl) phenol do.

In addition, the benzotriazole-based ultraviolet absorber is characterized in that 0.05 to 1.0 parts by weight based on 100 parts by weight of the methyl methacrylate-styrene copolymer.

In addition, the hindered amine light stabilizer is bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate, decane-2-acid bis (2,2,6,6-tetramethyl- 1 (octyloxy) -4-piperidinyl) ester, 1,1-dimethylethylhydroperoxide, bis (1,2,2,6,6-pentamethyl-4-piperidyl [[3,5- Bis (1,1dimethylethyl) -4-hydroxyphenyl] methyl] butyl maloenite, bis (1,2,2,6,6-pentamethyl-4-piperidyl) -sebacate, or methyl- 1,2,2,6,6-pentamethyl-4-piperidyl sebacate.

In addition, the hindered amine light stabilizer is characterized in that 0.05 to 1.0 parts by weight based on 100 parts by weight of the methyl methacrylate-styrene copolymer.

In addition, the said methyl methacrylate-styrene copolymer is a methacrylic acid alkyl ester, an acrylic acid alkyl ester, a methacrylic acid cycloalkyl ester, an acrylic cycloalkyl ester, a methacrylic acid aryl ester, an acrylonitrile, maleimide, and aryl acrylate. At least one monomer selected from the group consisting of esters or acid anhydrides thereof, acrylic acid, acid anhydrides of acrylic acid, methacrylic acid, acid anhydrides of methacrylic acid, maleic acid, and acid anhydrides of maleic acid are copolymerized together.

In addition, the resin composition is characterized in that it further comprises an additive selected from the group consisting of antioxidants, heat stabilizers, plasticizers, antistatic agents, nucleating agents, flame retardants, lubricants, impact modifiers, fluorescent brighteners.

Moreover, this invention provides the light guide plate manufactured using said resin composition.

According to the present invention, since the optical properties and light resistance are good and the amount of warpage generated by moisture is small, the light guide plate which does not generate dimensional change or whitening due to warpage can be provided while maintaining excellent optical properties when applied to the resin composition for light guide plates. Can be.

The present invention includes a methyl methacrylate-styrene copolymer, a benzotriazole ultraviolet absorber, and a hindered amine light stabilizer, and the content of styrene in the methyl methacrylate-styrene copolymer is the methyl methacrylate-styrene. It relates to a thermoplastic resin composition for a light guide plate, characterized in that 50 to 80 parts by weight based on 100 parts by weight of the copolymer.

Hereinafter, the present invention will be described in detail.

In the copolymer of the methyl methacrylate monomer and the styrene monomer, the content of the styrene monomer is preferably 50 to 80 parts by weight. When the content of the styrene monomer is less than 50 parts by weight, the hygroscopicity is increased, so that warpage or dimensional change is severe. When the content of the styrene monomer exceeds 80 parts by weight, the light resistance is so great that it cannot be overcome even by adding the ultraviolet absorbent or the light stabilizer included in the present invention. It is unpreferably lowered.

The styrene monomer used in the copolymer is preferably any one homopolymer selected from styrene, a-methyl styrene, m-methyl styrene, p-methyl styrene, and p-methoxy styrene or a copolymer thereof.

The above-mentioned methyl methacrylate-styrene copolymer may be copolymerized by adding a small amount of other monomers copolymerizable with them as necessary within the scope of not impairing the effects of the present invention, and the amount of the methyl methacrylate-styrene is usually added. It is the range of about 0-10 weight part with respect to a copolymer. As said monomer which can be copolymerized, alkyl methacrylate, alkyl acrylate, cycloalkyl ester of methacrylic acid, cycloalkyl ester of acrylic acid, aryl methacrylate, aryl ester of acrylic acid, etc., unsaturated acrylic acid, methacrylic acid, maleic acid, etc. Carboxylic acid or its acid anhydride, acrylonitrile, maleimide, etc. are mentioned.

As the benzotriazole ultraviolet absorber constituting the resin composition of the present invention, 2- (2H-benzotriazol-2-yl) -p-cresol, 2- (2H-benzotriazol-2-yl) -4- ( 1,1,3,3-tetramethylbutyl) phenol, 2,2'-methylenebis (6- (2H-benzotriazol-2-yl) -4-1,1,3,3-tetramethylbutyl) Phenolic etc. are mentioned, The content is preferable to mix | blend in the ratio of 0.05-1.0 weight part with respect to 100 weight part of said methyl methacrylate-styrene copolymers. If the amount of the ultraviolet absorber is too large, the color variation of the transmitted light is so severe that it is not suitable for use as a light guide plate, if too small it is not preferable because the effect of improving the UV stability is insignificant.

Examples of the hindered amine light stabilizer constituting the resin composition of the present invention include bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate and decan-2-acid bis (2,2, 6,6-tetramethyl-1 (octyloxy) -4-piperidinyl) ester, 1,1-dimethylethylhydroperoxide, bis (1,2,2,6,6-pentamethyl-4-piperi Dill [[3,5-bis (1,1dimethylethyl) -4-hydroxyphenyl] methyl] butyl maloenite, bis (1,2,2,6,6-pentamethyl-4-piperidyl) -Sebacate, methyl-1,2,2,6,6-pentamethyl-4-piperidyl sebacate, and the like, the content of which is 0.05 based on 100 parts by weight of the methyl methacrylate-styrene copolymer. If the amount of the light stabilizer is too small, the light resistance is inferior. If the amount of the light stabilizer is too small, problems such as coloring and mold contamination occur, which is not preferable.

In addition, the resin composition of the present invention may further include other additives, such as antioxidants, lubricants, if necessary.

Hereinafter, preferred examples are provided to help understanding of the present invention, but the following examples are merely to illustrate the present invention, and the scope of the present invention is not limited to the following examples.

EXAMPLE

Example 1

As the base resin, a methyl methacrylate-styrene copolymer having a weight ratio of styrene monomers of 80 parts by weight was used, and 0.2 parts by weight of Tinuvin-329 (Ciba) and a hindered amine, which were benzotriazole UV absorbers, in 100 parts by weight of the base resin. 0.2 parts by weight of Tinuvin-770 (Ciba), a light stabilizer, was melt-kneaded with a coaxial twin screw extruder (screw diameter 27 mm, L / D = 48) to prepare a pellet mixed composition. After drying the prepared pellets were prepared into a plate-like material having a thickness of 2mm using an extruder including a T-die.

 [Example 2]

The same method as in Example 1 was carried out except that the methyl methacrylate-styrene copolymer having a weight ratio of the styrene-based monomer was 50 parts by weight as the base resin.

Comparative Example 1

The same procedure as in Example 1 was carried out except that methyl methacrylate homopolymer (polymethyl methacrylate) was used as the base resin.

Comparative Example 2

Except for using a methyl methacrylate-styrene copolymer having a weight ratio of styrene monomer of 40 parts by weight as the base resin was carried out in the same manner as in Example 1.

Comparative Example 3

The same process as in Example 1 was carried out except that polystyrene was used as the base resin.

[Comparative Example 4]

The same procedure as in Example 1 was conducted except that no ultraviolet absorber and light stabilizer were used.

[Comparative Example 5]

The same procedure as in Example 1 was conducted except that cyano acrylate-based Uvinul 3035 (Basf) was used as the ultraviolet absorber.

[Comparative Example 6]

The same procedure as in Example 1 was conducted except that PR25 (Clariant), a benzylidene malonate system, was used as the ultraviolet absorber.

[Experimental Example]

The characteristics of the following items were measured for the manufactured product.

(1) Light transmittance: As an evaluation of transparency, the light transmittance was measured by a transmittance meter (HM-150, Murakami Color Research Laboratory) in accordance with JIS K 7361. In general, the light transmittance is 90% or more can be used as a light guide plate, and if it is 92% or more can be determined to be a very good level.

(2) Warpage characteristics: The plate-shaped product prepared by the melt extrusion processing method was cut to a size of 100 × 100 mm, and then left out in a constant temperature and humidity chamber at 80 ° C. and 90% humidity for 72 hours, and then warped. The results are shown in the table according to the bending state of the plate.

○: no warpage

△: warping slightly

×: warpage severe

(3) Light resistance: After irradiating ultraviolet light (QUV (light source UVB)) for 200 hours to the product prepared above, the color difference (DE) before and after irradiation was measured by measuring with a color difference meter. If the color difference before and after the irradiation is 3.0 or less, it can be judged as usable.

As shown in Table 1, the benzotriazole-based UV absorber and the hindered amine light stabilizer were added to the methyl methacrylate-styrene copolymer having styrene content of 80 parts by weight and 50 parts by weight, as shown in Examples 1 and 2. The prepared material can be confirmed that the warpage properties are significantly improved compared to the light guide plate made of polymethyl methacrylate of Comparative Example 1, as shown in Comparative Example 2 when using a copolymer having a styrene content of 40 parts by weight You can see this appears little by little. Therefore, according to the excellent bending characteristics results, it can be seen that the embodiment according to the present invention is superior in moisture resistance than the comparative example.

In addition, the color change of Comparative Example 3 using a base resin polymerized by styrene alone without methyl methacrylate, Comparative Example 4 without using an ultraviolet absorbent and a light stabilizer, and Comparative Examples 5 and 6 using different types of ultraviolet absorbents It can be seen that it is severe.

Claims (9)

A methyl methacrylate-styrene copolymer, a benzotriazole-based ultraviolet absorber, and a hindered amine light stabilizer, the content of styrene in the methyl methacrylate-styrene copolymer 100 is the methyl methacrylate-styrene copolymer 100 It is 50-80 weight part with respect to a weight part, The thermoplastic resin composition for light-guide plates. The method of claim 1, The styrene monomer is at least one member selected from styrene, a-methyl styrene, m-methyl styrene, p-methyl styrene, and p-methoxy styrene thermoplastic resin composition for a light guide plate. The method of claim 1, The benzotriazole UV absorber is 2- (2H-benzotriazol-2-yl) -p-cresol, 2- (2H-benzotriazol-2-yl) -4- (1,1,3,3- Tetramethylbutyl) phenol or 2,2'-methylenebis (6- (2H-benzotriazol-2-yl) -4-1,1,3,3-tetramethylbutyl) phenol Thermoplastic resin composition for. The method of claim 3, wherein The benzotriazole ultraviolet absorber is a thermoplastic resin composition for a light guide plate, characterized in that 0.05 to 1.0 parts by weight based on 100 parts by weight of the methyl methacrylate-styrene copolymer. The method of claim 1, The hindered amine light stabilizer is bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate, decane-2-acid bis (2,2,6,6-tetramethyl-1 ( Octyloxy) -4-piperidinyl) ester, 1,1-dimethylethylhydroperoxide, bis (1,2,2,6,6-pentamethyl-4-piperidyl [[3,5-bis ( 1,1dimethylethyl) -4-hydroxyphenyl] methyl] butyl maloenite, bis (1,2,2,6,6-pentamethyl-4-piperidyl) -sebacate, or methyl-1, It is 2,2,6,6-pentamethyl-4- piperidyl sebacate. The thermoplastic resin composition for light guide plates characterized by the above-mentioned. The method of claim 5, The hindered amine light stabilizer is a thermoplastic resin composition for a light guide plate, characterized in that 0.05 to 1.0 parts by weight based on 100 parts by weight of the methyl methacrylate-styrene copolymer. The method of claim 1, Methacrylic acid alkyl ester, acrylic acid alkyl ester, methacrylic acid cycloalkyl ester, acrylic acid cycloalkyl ester, methacrylic acid aryl ester, acrylonitrile, maleimide, aryl acrylate ester or the like in the methyl methacrylate-styrene copolymer 1 or more monomers selected from the group consisting of acid anhydrides, acrylic acid, acid anhydrides of acrylic acid, methacrylic acid, acid anhydrides of methacrylic acid, maleic acid, and acid anhydrides of maleic acid are copolymerized together. Composition. The method of claim 1, The resin composition further comprises at least one additive selected from the group consisting of antioxidants, heat stabilizers, plasticizers, antistatic agents, nucleating agents, flame retardants, lubricants, impact modifiers, and optical brighteners. . The light guide plate manufactured using the resin composition of any one of Claims 1-8.