JP3172061B2 - Surface-emitting aromatic polycarbonate resin composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a surface-emitting aromatic polycarbonate resin composition. More specifically, the present invention relates to a surface-emitting aromatic polycarbonate resin having excellent surface light-emitting properties, low luminance unevenness on a light-emitting surface, and excellent color tone.

[0002]

2. Description of the Related Art Aromatic polycarbonate resins have excellent mechanical properties, heat resistance and weather resistance, and are used in a wide range of applications as resins having high light transmittance.

As an edge light type surface light source used for a liquid crystal display, a pattern having a diffusing action such as milky white is printed on the back surface of a molded plate made of a transparent resin such as polymethyl methacrylate resin (Japanese Patent Laid-Open No. 5-176).
No. 30), a method of emitting light from the front surface by providing a reflection line of a convex portion or a concave portion on the back surface of the molded plate (Japanese Patent Laid-Open No.
-94802).

[0004] However, the method of printing a pattern having a diffusion action on a molded plate requires a processing step after molding, and furthermore, a uniform light emission is obtained between the incident portion of a light source such as a cold cathode tube and a portion far from the light source. It is necessary to take 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 reflection line of the convex portion or the concave portion requires a precise mold, and there is a problem that an expected effect cannot be obtained if the mold has insufficient transferability during molding. An aromatic polycarbonate resin composition having a light diffusing property is disclosed in JP-A-3-143950,
Although described in JP-A-6-32973, the resulting molded articles have low light transmittance and are not suitable for this type of application. Also, Japanese Unexamined Patent Publication No.
No. 84 describes a light guide plate in which oxide fine particles are blended with a transparent resin such as polymethyl methacrylate, but has a drawback that light transmittance tends to decrease and uniform and sufficient surface light emission is hardly obtained. Japanese Patent Application Laid-Open No. Hei 6-67026 describes a light guide plate comprising a transparent resin mixed with an inorganic fibrous substance such as glass fiber or whisker. However, there is a disadvantage in that In addition, aromatic polycarbonate resin is a transparent resin having a slightly yellow tint due to its properties, and thus has a problem of adversely affecting the hue in a color liquid crystal display.In general, a small amount of blue dye is used to improve the color tone of the aromatic polycarbonate resin. A method of blending a pigment is known, but in this case, there is a problem that light transmittance is reduced and sufficient surface light emission cannot be obtained. Also, Japanese Patent Laid-Open No. 5-1
No. 73132 describes a phosphor screen illuminant in which a fluorescent substance is mixed in a light guide plate. However, in order to obtain sufficient surface light emission in such a luminous body, it is necessary to mix a large amount of a fluorescent substance, There are drawbacks in that the mechanical properties of the illuminant deteriorate and color tone unevenness occurs. Therefore, there is a demand for a surface-emitting aromatic polycarbonate resin composition having excellent surface light-emitting properties, less unevenness in luminance on the light-emitting surface, and excellent color tone.

[0005]

DISCLOSURE OF THE INVENTION The present invention relates to a surface-emitting aromatic polycarbonate resin composition comprising an aromatic polycarbonate resin composition, which has excellent surface light-emitting properties, has less luminance unevenness, and has an excellent color tone. The purpose is to provide.

As a result of intensive studies to achieve the above object, the present inventor has found that an aromatic polycarbonate resin containing a very small amount of a bead-like crosslinked acrylic resin having a specific particle size is used.
By blending a fluorescent whitening agent, a bead-like crosslinked acrylic resin having a specific particle size or a surface emitting resin composition having an excellent color tone due to an interaction that cannot be obtained when a fluorescent whitening agent is used alone is found. Reached the present invention.

[0007]

According to the present invention, there is provided a bead-like crosslinked acrylic resin having an aromatic polycarbonate resin of 99.995 to 99.8% by weight and a weight average particle diameter of 1 to 30 μm in an amount of 0.005 to 0.2% by weight. % Resin component 100%
The present invention relates to a surface-emitting aromatic polycarbonate resin composition in which 0.0005 to 0.1 parts by weight of a fluorescent whitening agent is added to parts by weight.

The aromatic polycarbonate resin used in the present invention is a resin generally used as an engineering resin, and is an aromatic polycarbonate resin obtained by reacting a dihydric phenol with a carbonate precursor by a solution method or a melting method. . Representative examples of the dihydric phenol used here include 2,2-bis (4-hydroxyphenyl) propane (commonly known as bisphenol A), bis (4-hydroxyphenyl) methane, 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- (4 -Hydroxy-3-
Methylphenyl) propane, bis (4-hydroxyphenyl) ether, 4,4′-dihydroxydiphenyl,
Bis (4-hydroxyphenyl) sulfide and bis (4-hydroxyphenyl) sulfone are exemplified. Preferred dihydric phenols are bis (4-hydroxyphenyl) alkanes, of which bisphenol A is particularly preferred.

Examples of the carbonate precursor include carbonyl halide, carbonate ester and haloformate, and specific examples include phosgene, diphenyl carbonate and dihaloformate of dihydric phenol.

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.

Basic means of these manufacturing methods will be briefly described. In the case of a solution method using, for example, phosgene as a carbonate precursor, the reaction is usually carried out in the presence of an acid binder and a solvent. Examples of the acid binder include alkali metal hydroxides such as sodium hydroxide and potassium hydroxide and amine compounds such as pyridine. As the solvent, for example, halogenated hydrocarbons such as methylene chloride and chlorobenzene are used. For promoting the reaction, a catalyst such as a tertiary amine or a quaternary ammonium salt may be used. At that time, the reaction temperature is usually 0 to 40 ° C, and the reaction time is several minutes to 5 hours.

In a transesterification reaction (melting method) using a carbonic acid diester as a carbonate precursor, a predetermined ratio of a dihydric phenol component is stirred with a carbonic acid diester under heating in an inert gas atmosphere to produce alcohol or phenols. It is carried out by a method of distilling. The reaction temperature varies depending on the boiling point of the produced alcohol or phenol, and is usually in the range of 120 to 300 ° C. The reaction is completed under reduced pressure from the beginning while distilling off alcohol or phenols produced. Further, a catalyst usually used in a transesterification reaction to promote the reaction can be used. Examples of the carbonic acid diester used in the transesterification reaction include diphenyl carbonate, dinaphthyl carbonate, bis (diphenyl) carbonate, dimethyl carbonate, diethyl carbonate, dibutyl carbonate and the like. Of these, diphenyl carbonate is particularly preferred.

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, a concentration of 0.7 g / The specific viscosity (η _sp ) measured with a dl methylene chloride solution at a temperature of 20 ° C. is 0.15 to 1.5.
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 crosslinked 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 methacrylate, and the like, and divinylbenzene or ethylene glycol dimethacrylate is preferred. Used.

The weight average particle size of the bead-shaped 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. When the weight average particle diameter is less than 1 μm, sufficient light diffusing property cannot be obtained and the surface luminous property is inferior. When the weight average particle diameter exceeds 30 μm, the compounding amount increases to obtain a sufficient light diffusing effect, and the light transmittance is impaired. In addition, there is a disadvantage that luminance unevenness becomes large.

The compounding amount of the bead-shaped crosslinked acrylic resin is 0.005 to 0.2% by weight, and 0.01 to 0.1% by weight based on 100% by weight of the total of the aromatic polycarbonate resin and the beaded crosslinked acrylic resin. % Is particularly preferred. If the amount is less than 0.005% by weight, the light diffusion property is insufficient and the surface light emission property is reduced. On the other hand, if the compounding amount exceeds 0.2% by weight, the light transmittance decreases, the luminance unevenness on the light emitting surface increases, and uniform brightness cannot be obtained.

The optical brightener used in the present invention comprises:
There is no particular limitation as long as it is used to improve the color tone of a synthetic resin or the like to white or bluish white.Examples include stilbene, benzimidazole, benzoxazole, naphthalimide, rhodamine, coumarin, and oxazine. And the like. Here, the fluorescent whitening agent has a function of absorbing ultraviolet energy of light rays and radiating this energy to a visible part. The compounding amount of the optical brightener is 0.00 to the total 100 parts by weight of the aromatic polycarbonate resin and the bead-like crosslinked acrylic resin.
0 to 0.1 parts by weight. If the amount is less than 0.0005 parts by weight, sufficient surface luminous properties and the effect of improving the color tone of the light emitting surface cannot be obtained, while if it exceeds 0.1 part by weight, the effect of improving the color tone of the light emitting surface is small, and It is not preferable because the color tone (hue) becomes uneven. Furthermore, the compounding amount of the expensive fluorescent whitening agent increases and the cost increases.

In the aromatic polycarbonate resin composition, a flame retardant, a flame retardant aid, a heat stabilizer, an antioxidant, an ultraviolet absorber, a mold release agent, a flow modifier, a coloring agent as long as the purpose and effect are not impaired. An agent, a lubricant, a foaming agent, and the like may be added as needed. Further, other fillers such as glass powder, glass beads, glass flakes, calcium carbonate, silica, clay, talc, and mica may be used in a small amount.

For producing the aromatic polycarbonate resin composition of the present invention, any method and apparatus can be used. For example, a method of kneading with an extruder, a Banbury mixer, a roll or the like is appropriately selected. The composition of the present invention can be formed by a conventionally known method such as injection molding, injection compression molding, extrusion molding, blow molding, compression molding, and powder molding.

The aromatic polycarbonate resin composition of the present invention can provide a light guide plate having little unevenness in brightness, excellent surface emitting properties, and further excellent color tone simply by molding into a sheet. Further, on the back surface of the light guide plate, a reflection line or a reflection dot of a convex portion or a concave portion, or a white dot printing may be performed in order to further enhance surface light emission.

The resin composition of the present invention is suitable as an edge light type light guide plate and a surface light emitter of a liquid crystal display because it has a high light transmittance and excellent surface light emission and excellent color tone of a light emitting surface.

[0022]

The present invention will be further described with reference to the following examples. The evaluation was performed by the following methods (1) to (4).

(1) Total light transmittance: A test piece of 150 mm on a side and 4 mm in thickness was used.
The transmittance in the thickness direction was measured according to ASTM D1003 using a haze meter HR-100 manufactured by KK.

(2) Average luminance: 150 mm on a side, thickness 2
150 mm on a side, thickness 4
mm test piece is superimposed, and a diameter of 2.6
A cold-cathode tube with a length of 170 mm and a length of 170 mm was installed.
The brightness (cd / m ² ) of the point is measured by a color luminance meter B manufactured by Topcon Corporation.
It measured by M-7 and made the average value the average brightness. The evaluation device is shown in FIG. 1 and FIG.

(3) Uneven brightness: From the maximum brightness and the minimum brightness of the above measurement results, the uneven brightness was evaluated using the following equation. Uneven brightness (%) = (minimum brightness / maximum brightness) × 100 That is, 100% brightness unevenness indicates that there is no brightness unevenness and that the brightness is the best.

(4) Hue: 150 mm on a side, 2 mm in thickness
150mm on a side, thickness 4mm on top of white reflective resin plate
Are placed on one side of the test piece, and the diameter of the test piece is 2.6 m.
m, a cold-cathode tube having a length of 150 mm was installed, and nine hues of the test piece were measured with a color luminance meter BM-7 manufactured by Topcon Co., Ltd. did.

[Examples 1 to 6 and Comparative Examples 1 to 5] Aromatic polycarbonate resin, crosslinked particles (beaded crosslinked acrylic resin) and additives (fluorescent brightener and dye) shown in Table 1
Was dry-blended at the ratio shown in Table 1, and then a single-screw extruder equipped with a vent having a screw diameter of 30 mm [Nakatani Machine Co., Ltd.
Manufactured by VSK-30] at a cylinder temperature of 280 ° C., pellets are obtained by strand cutting, and the obtained pellets are dried at 120 ° C. for 5 hours by a hot-air circulating drier, followed by injection molding machine [Toshiba Machine Co., Ltd. Co., Ltd .: IS
-150 EN] to obtain a test piece for evaluation at a cylinder temperature of 280 ° C and a mold temperature of 80 ° C. Table 1 shows the evaluation results.

The symbolic contents of the aromatic polycarbonate resin, crosslinked particles and additives in Table 1 are shown below. In addition, the weight% indicating the addition amount of the bead-like crosslinked particles indicates the ratio to the total of 100% by weight of the aromatic polycarbonate resin and the crosslinked particles. Parts by weight indicating the amount of the additive are 100 parts in total of the aromatic polycarbonate resin and the bead-like crosslinked particles.
Indicates the ratio to the weight.

(A) Aromatic polycarbonate resin PC-1: [Panlite L-1225 manufactured by Teijin Chemicals Ltd.]
η _sp = 0.40] PC-2: [Panelite AD-550 manufactured by Teijin Chemicals Ltd.]
3 η _sp = 0.28] (B) Bead-shaped crosslinked acrylic resin PMMA-1: crosslinked polymethyl methacrylate fine particles [MBX-5 manufactured by Sekisui Chemical Co., Ltd., weight average particle diameter 5 μm] PMMA-2: crosslinked polymethyl Methacrylate fine particles [MBX-12 weight average particle diameter 12 μm, manufactured by Sekisui Plastics Co., Ltd.] (C) Fluorescent brightener K-1: [Kayalite OS manufactured by Nippon Kayaku Kogyo Co., Ltd.] K-2: [BASF ( (D) Blue organic dye K-3: [Sumiplast Violet B manufactured by Sumitomo Chemical Co., Ltd.]

[0030]

[Table 1]

[0031]

The molded article from the composition of the present invention has high light transmittance and excellent light diffusivity, is suitable for an edge light type light guide plate of a liquid crystal display, and has excellent surface light emission. In addition, the uniform brightness can be obtained, and further, since the color tone is good, the industrial effect achieved is remarkable.

[Brief description of the drawings]

FIG. 1 is a simplified plan view of an evaluation device of the present invention.

FIG. 2 is a simplified cross-sectional view of the evaluation device of the present invention.

[Explanation of symbols]

 Reference Signs List 1 light source (cold cathode tube) 2 test piece 3 white reflective resin plate 4 to 12 measurement points

Claims (1)

(57) [Claims] 1. An aromatic polycarbonate resin 99.99
5 to 99.8% by weight and a weight average particle diameter of 1 to 30 μm
100 parts by weight of a resin component comprising 0.005 to 0.2% by weight of a bead-shaped crosslinked acrylic resin and 0.0
A surface-emitting aromatic polycarbonate resin composition comprising 005 to 0.1 parts by weight.