JP3100853B2 - Light guide plate and surface light source structure comprising aromatic polycarbonate resin composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a light guide plate and a surface light source structure made of an aromatic polycarbonate resin composition. More particularly, the present invention relates to a light guide plate and a surface light source structure having excellent surface light-emitting properties and low luminance unevenness, which are made of an aromatic polycarbonate resin composition.

[0002]

2. Description of the Related Art As an edge light type surface light source structure used for a liquid crystal display, a pattern having a diffusing action such as a milky white color is printed on the back surface of a molded plate made of a transparent resin such as polymethyl methacrylate resin (Japanese Patent Laid-Open Publication No. HEI 9-163191). 5
(JP-A-17630), and those in which a convex or concave line is provided on the back surface of a molded plate (JP-A-5-94802). However, the method of printing a pattern having a diffusion action on a molded plate requires a processing step after molding,
Furthermore, in order to obtain uniform light emission at the light source incident portion such as a cold cathode tube and at a portion far from the light source, it is necessary to devise measures such as gradually changing the size and density of the pattern from the light source side to a portion far from the light source. In addition, the method of providing the line of the convex portion or the concave portion requires a precise mold, and there is a problem of transferability of the mold. The aromatic polycarbonate resin compositions having light diffusing properties are described in JP-A-3-143950 and JP-A-6-32973, but the molded articles obtained have low light transmittance and low surface light emission. It was inferior in properties and was not suitable for use as an edge light type surface light source structure. For this reason, a light guide plate and a surface light source which do not require post-processing after molding, have excellent surface light-emitting properties by a simple method, have less luminance unevenness on the light-emitting surface, have excellent light transmittance, and have good light diffusion properties. There is a need for a structure.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to provide a light guide plate and a surface light source structure which have excellent surface light emission and have less luminance unevenness. The present inventors have conducted intensive studies to achieve the above object, and as a result, obtained by molding a composition obtained by blending a specific amount of a bead-like crosslinked acrylic resin having a specific particle diameter with an aromatic polycarbonate resin. The molded article was found to be suitable as a light guide plate and a surface light source structure, and reached the present invention.

[0004]

According to the present invention, a weight average particle diameter of 1 to 100 parts by weight of an aromatic polycarbonate resin is 1 to 100 parts by weight.
30 μm bead-like crosslinked acrylic resin 0.005 to
The present invention relates to a light guide plate obtained by molding an aromatic polycarbonate resin composition containing 0.2 parts by weight.

[0005] The aromatic polycarbonate resin used in the present invention is a resin usually used as an engineering resin, and is an aromatic polycarbonate resin obtained by reacting a dihydric phenol with a carbonate precursor. Representative examples of the dihydric phenol used here include 2,2-bis (4-hydroxyphenyl) propane (commonly called bisphenol A), bis (4-hydroxyphenyl) methane, and 1,1-bis (4 -Hydroxyphenyl) ethane, 1,1-bis (4-hydroxyphenyl) cyclohexane, 2,2-bis (4-hydroxy-
3,5-dimethylphenyl) propane, 2,2-bis (4
-Hydroxy-3,5-dibromophenyl) propane,
2,2-bis (4-hydroxy-3-methylphenyl)
Propane, bis (4-hydroxyphenyl) ether,
4,4'-dihydroxydiphenyl, bis (4-hydroxyphenyl) sulfide, bis (4-hydroxyphenyl) sulfone and the like. Preferred dihydric phenols are bis (4-hydroxyphenyl) alkanes, of which bisphenol A is particularly preferred.

As the carbonate precursor, carbonyl halide, carbonate ester or haloformate is used, and specific examples include phosgene, diphenyl carbonate, dihaloformate of dihydric phenol and the like.

In producing the aromatic polycarbonate resin by reacting the above-mentioned dihydric phenol with a carbonate precursor, the dihydric phenol may be used alone or in combination of two or more. It may be a branched polycarbonate resin copolymerized with a polyfunctional aromatic compound, or a mixture of two or more aromatic polycarbonate resins. Further, a catalyst, a molecular weight regulator, an antioxidant and the like may be used as necessary.

Any molecular weight can be used for the aromatic polycarbonate resin. For example, when an aromatic polycarbonate resin is obtained using bisphenol A as a dihydric phenol and phosgene as a carbonate precursor, the concentration is 0.7 g / g. Those having a specific viscosity (η _SP ) of 0.15 to 1.5 measured with a dl methylene chloride solution at a temperature of 20 ° C. are preferred.

The bead-like crosslinked acrylic resin used in the present invention is a resin obtained by suspension polymerization or emulsion polymerization of an acrylic monomer with a crosslinking monomer. The acrylic monomer is an acrylate or methacrylate, for example, methyl acrylate,
Examples thereof include ethyl acrylate, propyl acrylate, butyl acrylate, 2-ethyl-hexyl acrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, and butyl methacrylate, and these may be used alone or in combination of two or more. Of these, methyl methacrylate is preferably used. Examples of the crosslinking monomer include divinylbenzene, allyl methacrylate, triallyl cyanurate, ethylene glycol dimethacrylate, propylene glycol allyl ether, diethylene glycol dimethacrylate, 1,6-hexanediol dimethacrylate, and the like, and divinylbenzene or ethylene glycol dimethacrylate. Is preferably used. The weight average particle diameter of the bead-like crosslinked acrylic resin is 1 to 30 μm, preferably 3 to 20 μm. The weight-average particle diameter of the bead-like crosslinked acrylic resin is determined by the electrozone method. Weight average particle size is 1μm
If it is less than 30 μm, a sufficient light diffusion effect cannot be obtained and the surface light emission is inferior. There are disadvantages. The blending amount of the bead-shaped crosslinked acrylic resin is 0.005 to 0.2 part by weight, preferably 0.01 to 0.1 part by weight, based on 100 parts by weight of the aromatic polycarbonate resin. If the amount is less than 0.005 parts by weight, the light diffusing property is insufficient, and the surface light emitting property is reduced. On the other hand, if the compounding amount exceeds 0.2 parts by weight, the light transmittance is reduced and the luminance unevenness of the light emitting surface is increased, so that uniform brightness cannot be obtained.

In the aromatic polycarbonate resin composition, a flame retardant, a flame retardant aid, a heat stabilizer, an antioxidant, an ultraviolet absorber, a fluorescent brightener, a mold release agent, a fluid, as long as the purpose and effect are not impaired. A modifier, a colorant, a lubricant, a foaming agent, and the like may be added as needed in their expression amounts. Further, other fillers such as glass fiber, glass powder, glass beads, glass flake, calcium carbonate, silica, clay, talc and mica may be used in a small amount.

For producing a light guide plate comprising the aromatic polycarbonate resin composition of the present invention, any method is employed. For example, the aromatic polycarbonate resin composition is kneaded with an extruder, a Banbury mixer, a roll, or the like, and then molded by a conventionally known method such as injection molding, extrusion molding, or compression molding to obtain a light guide plate.

The aromatic polycarbonate resin composition of the present invention can provide a light guide plate having little unevenness in luminance and excellent surface light emission by simply forming it into a sheet. Further, in order to further enhance surface light emission, a line of a convex portion or a concave portion may be provided on the back surface of the light guide plate.

Further, the present invention provides a light guide plate formed of the aromatic polycarbonate resin composition, a light source provided on at least one side of the light guide plate, and a surface light source constituted by a reflector provided on one surface of the light guide plate. It relates to the structure.

FIG. 1 shows an example of the surface light source structure of the present invention. In FIG. 1, A is a light source, B is a light guide plate, and C is a reflection plate. Examples of the light source include a cold cathode tube. The light source can be provided on at least one side surface of the light guide plate. The reflection plate preferably has a reflectance of 85% or more, and examples thereof include a white plate made of polyethylene terephthalate resin or a white plate made of an aromatic polycarbonate resin containing titanium oxide, zinc sulfide, or the like.

In this surface light source structure, light generated from the light source strikes the bead-like crosslinked acrylic resin at a certain rate while passing through the light guide plate and diffuses. The light diffused in the direction of the reflection plate is reflected by the reflection plate, proceeds to the surface of the light guide plate, and emits light on the surface of the light guide plate together with the light diffused in the surface direction. At this time, as in the description of the light guide plate, if the weight-average particle diameter of the bead-shaped crosslinked acrylic resin is less than a specific diameter or the blending amount is less than a specific amount, light is transmitted and sufficient light diffusion is obtained. When the weight average particle diameter exceeds a specific diameter or the blending amount exceeds a specific amount, the light diffuses sufficiently but conversely the light transmittance decreases and the light reaches a portion far from the light source. As a result, the luminance unevenness of the light emitting surface increases, and a desired surface light source structure cannot be obtained.

The molded article made of the aromatic polycarbonate resin composition of the present invention has high light transmittance and excellent light diffusivity, and is suitable as an edge light type light guide plate and a surface light source structure of a liquid crystal display. is there.

[0017]

The present invention will be further described with reference to the following examples. The evaluation was performed by the following methods (1) to (3). (1) Total light transmittance, diffuse light transmittance: 150 m per side
A test piece having a thickness of 4 m and a thickness of 4 mm was prepared, and each transmittance in the thickness direction was measured according to ASTM D1003 using a haze meter HR-100 manufactured by Murakami Color Research Laboratory. (2) Surface light-emitting property: A 150 mm-side, 4 mm-thick test piece is superimposed on a white reflector having a side of 150 mm and a thickness of 2 mm, and the side face of the test piece has a diameter of 3 mm and a length of 170 mm.
Was set up, and the light emission of the test piece was visually judged. In the judgment, an object having a light-emitting surface was indicated by ○, an object slightly dark was indicated by Δ, and a dark object was indicated by ×. (3) Brightness unevenness: A test piece having a side of 150 mm and a thickness of 4 mm was overlaid on a white reflector having a side of 150 mm and a thickness of 2 mm, and a diameter of 3 mm and a length of 170 mm were placed on the side of the test piece.
Of the test piece was visually determined for uneven brightness of the test piece.
In the judgment, an object having a uniform light-emitting surface was indicated by a circle, an object having a slightly non-uniform brightness was indicated by a triangle, and an object having a non-uniform brightness was indicated by a cross.

[0018]

Examples 1 to 4 and Comparative Examples 1 to 5 After the aromatic polycarbonate resin and additives shown in Table 1 were dry-blended at the ratios shown in Table 1, a single-screw extruder with a screw diameter of 30 mm [Nakatanani Kikai Co., Ltd. ): VSK-30], melt-kneading at a cylinder temperature of 280 ° C., and pellets are obtained by strand cutting.
After drying with a hot air circulating dryer at 5 ° C. for 5 hours, a test piece for evaluation was obtained at a cylinder temperature of 280 ° C. and a mold temperature of 80 ° C. using an injection molding machine [Toshiba Machine Co., Ltd .: IS-150EN]. Table 1 shows the evaluation results. The symbols of the aromatic polycarbonate resin and the additives in Table 1 are as follows. PC: aromatic polycarbonate resin [Panlite L-1225, η _SP = 0.41 manufactured by Teijin Chemicals Ltd.] PMMA-1: Crosslinked polymethyl methacrylate fine particles [MBX-5 weight average particles manufactured by Sekisui Plastics Co., Ltd.] Diameter 5 μm] PMMA-2: Crosslinked polymethyl methacrylate fine particles [MBX-12 weight average particle diameter 12 μm manufactured by Sekisui Chemical Co., Ltd.] MF: Glass milled fiber [PF manufactured by Nitto Boseki Co., Ltd.]
E-301 9 μm in diameter, 40 μm in length]

[0019]

[Table 1]

[0020]

The molded article made of the aromatic polycarbonate resin composition of the present invention has a high light transmittance and an excellent light diffusion property, and has a light guide plate of an edge light type for a liquid crystal display and a surface light source structure. As a result, it is possible to obtain excellent surface light emission and uniform brightness, and the industrial effects achieved are outstanding.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an example of a surface light source structure of the present invention.

[Explanation of symbols]

 A light source B light guide plate C reflector plate

Claims (2)

(57) [Claims] 1. An aromatic polycarbonate resin composition comprising 100 parts by weight of an aromatic polycarbonate resin and 0.005 to 0.2 parts by weight of a bead-like crosslinked acrylic resin having a weight average particle diameter of 1 to 30 μm. Light guide plate. 2. A light guide plate formed of the aromatic polycarbonate resin composition according to claim 1, a light source provided on at least one side of the light guide plate, and a reflector formed on one side of the light guide plate. Light source structure.