JP2005247999A - Light diffusing resin composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light diffusing resin composition useful as a material for a part composed of a light-diffusing molded article, e.g. a cover and lens for various displays using LED, a lens or lens cover of an LED signal lamp, an illumination lamp cover, an illuminated advertizing display, a transmission-type screen, various displays, a light-diffusing sheet of a liquid crystal display device and an optical waveguide, more particularly a light-diffusing resin composition composed of a polycarbonate and fine particles of an acryl-styrene copolymer, having high total light transmittance and haze value and giving a display free from the glare of LED in the case of using as a cover or lens of various display devices using LED. <P>SOLUTION: The light diffusing resin composition contains 100 pts. wt. of a polycarbonate resin and 0.1-5.0 pts. wt. of fine particles of an acryl-styrene copolymer having a refractive index of 1.505-1.575 and a weight-average particle diameter of 0.5-30μm. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a member made of a light diffusing molded article, for example, various display covers and lenses using LEDs, for example, a lens or lens cover of an LED signal lamp, a lighting cover, a lighting sign, a transmission screen, and various displays The present invention relates to a light diffusing resin composition useful as a material for a light diffusion sheet, a light guide plate and the like of a liquid crystal display device. More specifically, it consists of polycarbonate and acrylic-styrene copolymer fine particles, and has a high total light transmittance and high haze. In particular, when used as a cover or lens for various displays using LEDs, there is no display of LED glare. The present invention relates to a possible light diffusing resin composition.

Polycarbonate has a wide range of uses as a thermoplastic resin with excellent impact resistance, heat resistance, and transparency, and is lighter and more productive than inorganic glass. It can also be suitably used for applications requiring light diffusibility, such as transmission screens, various displays, light diffusion sheets for liquid crystal display devices, and light guide plates.
In order to impart light diffusibility to the polycarbonate, addition of inorganic compounds such as glass, silica and aluminum hydroxide has been proposed, but the thermal stability during molding and extrusion is low, and impact is reduced. There was a drawback that the mechanical strength such as strength was greatly reduced.
As a light diffusing polycarbonate resin improved in such a defect, for example, Patent Document 1 discloses that a refractive index difference with respect to 100 parts by weight of a polycarbonate resin is larger than 0.08 and at least partially. A light diffusing polycarbonate resin is disclosed in which 0.05 to 20 parts by weight of polymethyl methacrylate fine particles that are crosslinked and have a weight average particle size in the range of 0.5 to 100 μm are dispersed and added. As described in the examples, the total light transmittance was as low as less than 80%, which was inferior in practicality.

Patent Document 2 discloses a light diffusing resin composition comprising 100 parts by weight of an aromatic polycarbonate resin and 0.01 to 1 part by weight of a bead-like crosslinked acrylic resin as a molding material suitable for a light diffusing plate. However, the performance to eliminate glare when using the LED light source was insufficient.
In Patent Document 3, as a resin composition excellent in light transmittance and light diffusibility, 0.1 to 5 parts by weight of calcium carbonate (B) per 100 parts by weight of polycarbonate resin (A), titanium oxide (C) 0 A polycarbonate resin composition characterized by comprising 0.01 to 0.3 parts by weight and 0.001 to 2 parts by weight of polyorganohydrogensiloxane (D) has been disclosed, but in terms of thermal stability and impact resistance. Further, it was not satisfactory, and the total light transmittance was insufficient.
In Patent Document 4, a total of 100 parts by weight of 99.7 to 80% by weight of polycarbonate resin and 0.3 to 20% by weight of transparent fine particles having an average particle diameter of 1 to 30 μm and a fluorescent brightening agent of 0.0005 to 0.001. Although a light diffusion plate for direct-type backlight made of polycarbonate resin with a thickness of 0.5 to 3.0 mm formed from a resin composition consisting of 1 part by weight is disclosed, the brightness is improved by using a fluorescent whitening agent. Therefore, thermal stability is insufficient, discoloration during molding and extrusion, and discoloration during recycling are likely to occur, resulting in low practicality.
In addition, the molded product of Patent Documents 1 to 4 and the molded product made of the resin composition are not described when an LED having a low luminous flux and a high directivity is used as the light source, and these molded products are assumed to be as such. Even when used for various purposes, it is difficult to eliminate the glare of the LED, and therefore, display with excellent visibility is impossible.

Japanese Patent Laid-Open No. 03-143950 Japanese Patent Laid-Open No. 10-046018 JP 2000-169695 A JP 2004-029091 A

  The present invention solves the above-mentioned problems of the prior art, eliminates the glare of the LED especially when the LED is used as a light source, and uses a light diffusing resin composition having a high total light transmittance, and the same. It is to provide a light diffusing member.

As a result of intensive studies to solve the problems of the prior art, the present inventors blend acrylic-styrene copolymer fine particles having a specific refractive index and a specific particle diameter with a specific ratio in polycarbonate. Thus, a light diffusing resin composition that is excellent in light transmittance and light diffusibility without impairing the original properties of polycarbonate and effective in obtaining a molded product without glare when an LED is used as a light source has been found. Completed the invention.
That is, the gist of the present invention is that 100 parts by weight of a polycarbonate resin has a refractive index of 1.505 to 1.575 and a weight average particle diameter of 0.5 to 30 μm of acrylic-styrene copolymer fine particles 0.1 to 0.1. This is a light diffusing resin composition containing 5.0 parts by weight.

  Since the light diffusing resin composition of the present invention eliminates glare of the LED and has a high total light transmittance, the lens or lens cover of the signal lamp using the LED, the lighting cover, the lighting signboard, Can be used in a wide range of applications that require light diffusivity, such as transmissive screens, various displays, light diffusion sheets for liquid crystal display devices, and light guide plates, especially for display materials that use LEDs as the light source. ing.

Hereinafter, the present invention will be described in detail.
The polycarbonate resin used in the present invention is obtained by an interfacial polymerization method of an aromatic dihydroxy compound or a small amount thereof and phosgene, or an aromatic dihydroxy compound or a small amount of this compound and a carbonic acid. An aromatic polycarbonate polymer which may be branched, which is produced by a transesterification reaction with a diester.

  Examples of the aromatic dihydroxy compound include 2,2-bis (4-hydroxyphenyl) propane (= bisphenol A), 2,2-bis (4-hydroxy-3,5-dimethylphenyl) propane (= tetramethylbisphenol A). ) And the like bis (4-hydroxyphenyl) alkane dihydroxy compounds, 2,2-bis (4-hydroxy-3,5-dibromophenyl) propane (= tetrabromobisphenol A), 2,2-bis (4-hydroxy) -1,3-bis (4-hydroxyphenyl) cyclohexane, hydroquinone, resorcinol in addition to bis (4-hydroxyphenyl) alkane-based dihydroxy compounds containing halogen such as −3,5-dichlorophenyl) propane (= tetrachlorobisphenol A) 4,4-dihydroxydiphenyl The like, preferably contain a halogen also include good bis (4-hydroxyphenyl) alkane-based dihydroxy compounds, particularly preferred include bisphenol A. These aromatic dihydroxy compounds may be used alone or in combination.

  In order to obtain a branched polycarbonate, phloroglucin, 4,6-dimethyl-2,4,6-tri (4-hydroxyphenyl) heptene-2, 4,6-dimethyl-2,4,6-tri (4 -Hydroxyphenyl) heptane, 2,6-dimethyl-2,4,6-tri (4-hydroxyphenylheptene-3,1,3,5-tri (4-hydroxyphenyl) benzene, 1,1,1- Polyhydroxy compounds represented by tri (4-hydroxyphenyl) ethane and the like, and 3,3-bis (4-hydroxyaryl) oxindole (= isatin bisphenol), 5-chlorisatin bisphenol, 5,7-dichlorois Trihydroxy or higher polyhydroxy compounds such as chin bisphenol and 5-bromoisatin bisphenol The amount of polyhydroxy compound used is, for example, about 0.1 to 2 mol% of the dihydroxy compound.

  Furthermore, a monovalent aromatic hydroxy compound or the like can be used as a molecular weight regulator. Examples of the molecular weight modifier include m- and p-methylphenol, m- and p-propylphenol, p-bromophenol, p-tert-butylphenol, and p-long chain alkyl-substituted phenol.

The molecular weight of the polycarbonate resin used in the present invention is a viscosity average molecular weight measured from the viscosity of the methylene chloride solution at 25 ° C., preferably 16,000 to 38,000, more preferably 18,000 to 35,000. .
The polycarbonate resin used in the present invention may be a mixture of two or more.

  The acrylic-styrene copolymer fine particles used in the present invention are fine particles obtained by copolymerizing an acrylic monomer and a styrene monomer. For example, a suspension polymerization method of an acrylic monomer and a styrene monomer. It is preferable that the fine particles are polymerized with a crosslinking agent using a crosslinking agent. Examples of acrylic monomers include, for example, methacrylate monomers such as methyl methacrylate and ethyl methacrylate, acrylate monomers such as methyl acrylate and ethyl acrylate, and acrylamide. Typical examples of styrene monomers include styrene and α-methyl. Styrene, vinyltoluene and the like can be exemplified as typical examples. In the copolymerization of these monomers, these monomers may be used as the main components, and other monomers may be copolymerized as necessary. Examples of the crosslinking agent include commonly used ones such as ethylene glycol dimethacrylate, divinylbenzene, 1,6-hexanediol, trimethylpropane trimethacrylate, trimethylpropane trimethacrylate, and trimethylpropane triacrylate. Functional monomers can be used.

The weight average particle diameter of the acrylic-styrene copolymer fine particles used in the present invention is 0.5 to 30 μm, preferably 1.0 to 20 μm. If the particle size is less than 0.5 μm, the light diffusibility is low and the light source can be seen through, and if it exceeds 30 μm, the diffusion effect on the addition amount is low. Poor visibility.
The acrylic-styrene copolymer fine particles have a refractive index of 1.493 to 1.99 by changing the copolymerization ratio of the acrylic monomer and the styrene monomer in the range of 99: 1 to 1:99. Adjustment can be made within a range of 590. However, if the copolymerization ratio of the styrenic monomer becomes too high, the light resistance is lowered and yellowish, and conversely if the copolymerization ratio of the acrylic monomer becomes too high, the refractive index between the fine particles and the polycarbonate The difference between the two is too wide, the glare of the LED light source is conspicuous, and the visibility is low. Therefore, in the present invention, the refractive index of the acrylic-styrene copolymer fine particles is 1.505 to 1.575, preferably 1.510 to 1.570, and more preferably 1.515 to 1.565. Use one. In order to obtain fine particles having such a refractive index, it is necessary to adjust the copolymerization ratio of the acrylic monomer and the styrene monomer. Although the adjustment ratio varies depending on the monomer used, the refractive index becomes lower when a large amount of acrylic monomer is used, and the refractive index becomes higher when a large amount of styrene monomer is used. For example, when methyl methacrylate is used as the acrylic monomer and styrene is used as the styrene monomer, the ratio of the acrylic monomer to the styrene monomer is about 7: 3 when the refractive index is adjusted to about 1.52. When the ratio is adjusted to about 1.56, it is about 3: 7, and usually it should be adjusted before and after this.

The structure of the acrylic-styrene copolymer fine particles used in the present invention is not particularly limited, but the hollow one is easily deformed when mixed with a polycarbonate resin or when molding a resin composition, and the appearance of the molded product is This is not preferable because it often becomes defective and the balance between light diffusibility and light transmittance is often not so good. A porous material is excellent in light diffusibility even in a small amount, but is not preferred because the transmittance tends to decrease. In the case of fine particles having a two-layer structure of a core part and a shell part, the shell part is an acrylic-styrene copolymer fine particle, and the particle diameter and refractive index satisfy the scope of the present invention. Can be used. In that case, a core having a refractive index lower than that of the shell portion such as polymethyl methacrylate or silicone is preferable. However, in the case of such multi-layer structured fine particles, the cost may increase, and in the present invention, solid fine particles of an acrylic-styrene cross-linked copolymer are preferable.
As the acrylic-styrene copolymer fine particles usable in the present invention, those available from the market may be used. Examples of such commercially available products are, for example, from the GBS series or GSM series marketed by Gantz Kasei Co., Ltd. under the trade name Gantzpearl or Staphyloid, and conform to the physical properties defined in the present invention. To do.

  The light diffusing resin composition of the present invention is a mixture of 100 parts by weight of polycarbonate and 0.1 to 5.0 parts by weight of specific acrylic-styrene copolymer fine particles. If the acrylic-styrene copolymer fine particles are less than 0.1 parts by weight, the light diffusibility is poor. On the other hand, when the acrylic-styrene copolymer fine particle exceeds 5.0 parts by weight, the total light transmittance is lowered, and further, the mechanical strength and the heat resistance may be lowered.

In the light diffusing resin composition of the present invention, for example, an ultraviolet absorber, an antioxidant, a fluorescent brightener, a release agent, an antistatic agent, a colorant, a heat stabilizer, a fluidity improver, if necessary. You may add a flame retardant, an aggregation inhibitor, etc. Among these, at least one of ultraviolet absorbers, antioxidants, fluorescent brighteners, heat stabilizers, and flame retardants may be used.
Although it does not specifically limit as an example of a ultraviolet absorber, A cyclic | annular imino ester type ultraviolet absorber is used preferably especially. Examples of the cyclic imino ester ultraviolet absorber include p-phenylenebis (1,3-benzoxazin-4-one), which is commercially available from Takemoto Yushi Co., Ltd. under the trade name: Pionein ZA-101. Has been. The amount of the ultraviolet absorber used is preferably in the range of 0.05 to 5% by weight in the resin composition.
Moreover, as an example of antioxidant, what is necessary is just to select according to the objective what is known for thermoplastic resins, but a phosphorus type, a phenol type, etc. are preferable and these may be used together. Among these, phosphorus-based is preferable, and tris (2,4-di-t-butylphenyl) phosphite (for example, Asahi Denka Kogyo Co., Ltd. product, trade name: ADK STAB 2112) is preferable. The amount of the antioxidant used is preferably in the range of 0.05 to 5% by weight in the resin composition.
As examples of fluorescent brightening agents, known ones for thermoplastic resins can be used. Among them, those having a high molecular weight are preferable, for example, stilbene benzoxazole-based and phenylallyltriazolyl coumarin-based fluorescents. A brightener is mentioned. The amount of the optical brightener used is preferably in the range of 0.005 to 0.1% by weight in the resin composition. In order to increase the whiteness, a white pigment such as titanium oxide may be added. Further, as described in JP-A-2002-3710, an ultraviolet absorber such as benzotriazole, benzophenone, or triazine that does not have a maximum absorption wavelength at 350 to 400 nm for improving weather resistance, You may use separately from the said cyclic imino ester type ultraviolet absorber.

  The mixing and kneading of the light diffusing resin composition of the present invention may be carried out by a method applied to ordinary thermoplastic resins, for example, ribbon blender, Henschel mixer, Banbury mixer, drum tumbler, single screw extruder, 2 It can be carried out by an axial screw extruder, a multi-screw extruder or the like. The temperature condition for kneading is usually 260 to 300 ° C.

The light diffusing resin composition of the present invention can be used for a general thermoplastic resin molding method, but from the point of productivity, injection molding, injection compression molding, extrusion molding from a pellet-shaped resin composition. Furthermore, vacuum molding, pressure molding, free blow molding, or the like from an extruded sheet-like molded product can be performed to obtain a target molded product.
The thickness of the molded product when actually used is not particularly limited as long as the desired performance can be exhibited, but it is preferably 0.5 to 5 mm in practice. Even if the thickness of the molded product is too thin, the light diffusibility may not be sufficient or the light source may be seen through, which is not preferable. Is not preferable because it may be too heavy and difficult to use.
The light diffusing member of the present invention includes a light diffusing molding device, for example, a cover or a lens for various display devices using an LED (light emitting diode element), for example, a lens or a lens cover for an LED signal lamp, an OA device, or a television. And the like, a light diffusion sheet of a liquid crystal display device, a light guide plate, a cover of a lighting device or a lighting fixture, a lighting signboard, a transmission screen, and the like. In the present invention, the light source is particularly effective when used as a cover or a lens of a lighting fixture or a display fixture using an LED having a low luminous flux and high directivity.

EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to a following example, unless the summary is exceeded. Moreover, the evaluation method in the Example and comparative example of the light diffusable resin composition of this invention, and the molding conditions of a test piece are as follows.
1) Total light transmittance and haze: A test piece having a thickness of 3 mm was measured using NDH-2000 manufactured by Nippon Denshoku in accordance with JIS K7105.
2) Visibility: 10 x 0.6 candela LEDs placed 10 cm away from the back side of the 2 x 300 x 600 mm sheet-shaped molded product, and the LED glare from 30 cm away from the surface side of the sheet-shaped molded product The brightness was visually observed. The case where there was a slight glare was rated as x, the case where there was almost no glare, and the case where there was no glare as ◯.
3) Test piece molding conditions: The pellets pre-dried at 120 ° C. for 4 hours were molded with a 150M3 injection molding machine manufactured by Meiki Seisakusho at a cylinder temperature of 280 ° C., a molding cycle of 50 seconds, and a mold temperature of 80 ° C.

[Examples 1 to 5]
To 100 parts by weight of a polycarbonate resin (trade name: Iupilon (registered trademark) S-3000F) manufactured by Mitsubishi Engineering Plastics Co., Ltd., 0.1% of Pionin ZA-101 manufactured by Takemoto Yushi Co., Ltd. as a UV absorber. 2 parts by weight, manufactured by Asahi Denka Kogyo Co., Ltd. as a heat stabilizer, trade name: 0.05 parts by weight of ADK STAB 2112, and acrylic-styrene copolymer fine particles A (Gantz Kasei) shown in Table 1 as a light diffusing agent Product name: Gantz Pearl GSM-1261), B (Gantz Kasei Co., Ltd., product name: Gantz Pearl GSM-1841) or C (Gantz Kasei Co., Ltd., product name: Gantz Pearl GSM-0561) ) (Hereinafter, may be abbreviated as “copolymerized fine particles A, B, or C”) at the ratio shown in Table 1, and a single screw having a screw diameter of 40 mm and a cylinder set temperature of 260 ° C. To prepare pellets in an extruder, molding the test piece in the conditions evaluated, and the results are shown in Table 1. From Table 1, it became clear that the lens of the present invention has both high total light transmittance and high haze, no glare of LED, and excellent visibility.

[Comparative Examples 1-5]
As a light diffusing agent, crosslinked acrylic resin fine particles D (manufactured by Gantz Kasei Co., Ltd., trade name: Gantz Pearl GM-0630H) or E (manufactured by Gantz Kasei Co., Ltd., trade name: Gantz Pearl GM-0105) ) (Hereinafter, may be abbreviated as “polymer fine particles D or E”), and the test was performed under the same conditions as in Examples 1 to 5 except that the blending ratio was as shown in Table 2. Evaluation results Are shown in Table 2.

As is clear from the above, in the examples, the total light transmittance, haze, Izod impact strength, heat resistance, and visibility were all well-balanced and excellent, whereas in the comparative example, those were balanced. The light diffusing resin composition was not satisfactory.

Claims (10)

100 parts by weight of polycarbonate resin contains 0.1 to 5.0 parts by weight of acrylic-styrene copolymer fine particles having a refractive index of 1.505 to 1.575 and a weight average particle diameter of 0.5 to 30 μm. A light diffusing resin composition. The light-diffusing resin composition according to claim 1, which is a crosslinked acrylic-styrene copolymer fine particle. The light-diffusing resin composition according to claim 1 or 2, comprising at least one of an ultraviolet absorber, an antioxidant, a heat stabilizer, a flame retardant, and a fluorescent brightening agent. 4. The light diffusing resin composition according to claim 1, 2 or 3, comprising a cyclic imino ester-based ultraviolet absorber. The light-diffusing resin composition according to any one of claims 1 to 4, comprising a phosphorus-based antioxidant. A light diffusing member using the light diffusing resin composition according to any one of claims 1 to 5. The light diffusing member according to claim 6 used for an illuminating device. The light diffusing member according to claim 6, which is used for a display device. The light diffusing member according to claim 6, wherein the light diffusing member is used for a lighting device or a display device using an LED (light emitting diode) as a light source. The light diffusing member according to claim 6, which is a lens or a cover of an LED signal lamp.