JP2007023227A - Resin composition for light-diffusing member and light-diffusing member - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a resin composition for light-diffusing member, which has excellent light-diffusing properties, total light transmittance, hue and light resistance, especially suppresses gas produced in melt processing and has performance of excellent total balance without impairing properties characteristic of polycarbonate resin and a light-diffusing member. <P>SOLUTION: The resin composition for light-diffusing member comprises (A) 100 parts wt. of an aromatic polycarbonate resin, (B) 0.05-20 parts wt. of an ultraviolet light absorber composed of an acrylic copolymer and (C) 0.05-20 parts wt. of fine particles with a fluorescent dye dispersed therein. The light-diffusing member is obtained by melt-molding the resin composition. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a resin composition for a light diffusing member and a light diffusing member. Specifically, the resin composition for a light diffusing member is excellent in light diffusibility, total light transmittance, hue and light resistance without impairing the physical properties inherent to the polycarbonate resin. And a light diffusing member obtained from the resin composition.

  Polycarbonate resin has a wide range of uses as a thermoplastic resin excellent in impact resistance, heat resistance and transparency, and is lighter than inorganic glass and excellent in productivity, so by imparting light diffusibility, It is suitable for applications such as lighting covers, lighting signs, transmissive screens, various displays, and light diffusion sheets for liquid crystal display devices. In order to impart light diffusibility to this polycarbonate resin, a method of adding an inorganic compound such as glass, silica, aluminum hydroxide has been proposed, but the thermal stability during molding or extrusion is low, There was a drawback that the mechanical strength such as impact strength was greatly reduced.

  As a light diffusing polycarbonate resin improved in such a defect, for example, Patent Document 1 discloses a polymethylmethacrylate in which a difference in refractive index from a polycarbonate resin is larger than 0.08 and at least partially crosslinked. A light diffusing polycarbonate resin having acrylate fine particles dispersed therein is disclosed. However, in such a resin composition in which fine particles as a light diffusing agent are dispersed in a polycarbonate resin, when a large amount of fine particles are added to increase light diffusibility, the light transmittance decreases, and the light transmittance and light diffusion are reduced. There was a problem that a material having high properties could not be obtained.

  As a method for solving this, Patent Document 2 discloses a light diffusing resin composition in which a light diffusing agent composed of an inorganic phosphor, phosphor-containing resin particles or fluorescent dye-containing resin particles is dispersed in a transparent resin. Has been. However, although the resin composition of Patent Document 2 can increase the brightness, it has insufficient light resistance (weather) and is not practical as a light diffusing member.

  As a method for improving the light resistance of an aromatic polycarbonate resin, a method of adding various ultraviolet absorbers is known. For example, Patent Documents 3 and 4 disclose a polycarbonate resin composition comprising a polycarbonate resin containing a benzotriazole-based or benzophenone-based ultraviolet absorber and a benzoxazole-based or coumarin-based fluorescent brightening agent, Patent Document 5 further discloses a resin composition containing transparent fine particles.

  However, these resin compositions of Patent Documents 3 to 5 have a large amount of gas generated at the time of melt processing, are inferior in hue, and further have insufficient thermal stability, so that they are discolored during molding or recycling. There was a problem that it was easy to occur.

  On the other hand, Patent Document 6 discloses that the use of an ultraviolet absorbing composition containing a copolymer of methyl methacrylate and a benzotriazole compound improves the UV absorption characteristics. However, in the polycarbonate resin composition for a light diffusing member, the object of reducing the gas generated at the time of melt processing is not paid attention at all.

  Thus, the conventional resin composition is practically insufficient as a material for the light diffusing member, and is excellent in all of light diffusibility, total light transmittance, hue and light resistance, and in particular, melted. There has been a demand for a resin composition for a light diffusing member that suppresses gas generated during processing and has a comprehensively balanced performance.

Japanese Patent Laid-Open No. 03-143950 JP 09-176366 A Japanese Patent Application Laid-Open No. 07-196904 JP 2002-003710 A JP 2004-029091 A JP-A 63-227575

  The object of the present invention is to solve the above-mentioned problems of the prior art, and is excellent in all of light diffusibility, total light transmittance, hue and light resistance, without impairing the original properties of polycarbonate resin. An object of the present invention is to provide a resin composition for a light diffusing member and a light diffusing member that suppress the generated gas and have a comprehensively balanced performance.

  As a result of intensive studies to achieve the above object, the present inventors have made the polycarbonate resin contain a specific polymer type ultraviolet absorber and specific fine particles in which a fluorescent dye is dispersed, thereby allowing light diffusibility. The present invention has been completed by finding out that it is excellent in all of light transmittance, hue and light resistance, and in particular, it is possible to suppress the generated gas during melt processing.

  That is, the gist of the present invention is that 0.05 to 20 parts by weight of an ultraviolet absorber (B) made of an acrylic copolymer and a fluorescent dye are dispersed with respect to 100 parts by weight of an aromatic polycarbonate resin (A). A resin composition for a light diffusing member comprising 0.05 to 20 parts by weight of fine particles (C), and a light diffusing member formed by melt-molding the resin composition , Exist.

  The resin composition for a light diffusing member of the present invention satisfies high light diffusibility and high light transmittance at the same time without impairing the original characteristics of the aromatic polycarbonate resin, and can suppress discoloration during melt processing, thereby preventing transmitted light. Hue is good. In addition, there is little discoloration due to ultraviolet rays generated from the light source, and the light resistance is excellent. In particular, since the amount of gas generated during melt processing is small, a gas component does not adhere to the surface of the molded product by continuous molding, and a molded product with a good appearance can be obtained. Therefore, the resin composition of the present invention is suitable for a light diffusing member such as a light diffusing sheet and a light diffusing plate of a lighting cover, a lighting signboard, a transmissive screen, various displays, and a liquid crystal display device. It is suitable as a large diffusing plate for a liquid crystal television, which is often installed and is likely to be affected by the appearance performance.

Hereinafter, the present invention will be described in detail.
(A) Aromatic polycarbonate resin The aromatic polycarbonate resin (A) used in the present invention is an interfacial polymerization method (phosgene method) in which an aromatic dihydroxy compound or a small amount of a polyhydroxy compound is reacted with phosgene, or carbonic acid. It is a resin obtained by a melting method (transesterification method) for reacting with a diester, and is a linear or branched thermoplastic polymer or copolymer.

  As the aromatic dihydroxy compound as a raw material, 2,2-bis (4-hydroxyphenyl) propane (= bisphenol A), 2,2-bis (4-hydroxy-3,5-dimethylphenyl) propane (= tetramethylbisphenol) Bis (4-hydroxyphenyl) alkane dihydroxy compounds such as A), 2,2-bis (4-hydroxy-3,5-dibromophenyl) propane (= tetrabromobisphenol A), 2,2-bis (4- In addition to bis (4-hydroxyphenyl) alkane dihydroxy compounds containing halogen such as hydroxy-3,5-dichlorophenyl) propane (= tetrachlorobisphenol A), 1,1-bis (4-hydroxyphenyl) cyclohexane, hydroquinone, Resorcinol, 4,4-dihydroxydipheny And the like. Among these, a bis (4-hydroxyphenyl) alkane dihydroxy compound which may contain a halogen is preferable, and bisphenol A is particularly preferable. One kind of these aromatic dihydroxy compounds may be used, but a plurality of kinds may be used.

  In order to obtain a branched aromatic polycarbonate resin, a part of the above-mentioned aromatic dihydroxy compound is replaced with the following compounds: phloroglucin, 4,6-dimethyl-2,4,6-tris (4-hydroxyphenyl). ) Heptene-2,4,6-dimethyl-2,4,6-tris (4-hydroxyphenyl) heptane, 2,6-dimethyl-2,4,6-tris (4-hydroxyphenyl) heptene-3, 1 , 3,5-tris (4-hydroxyphenyl) benzene, 1,1,1-tris (4-hydroxyphenyl) ethane, 3,3-bis (4-hydroxyaryl) oxindole (= isatin bisphenol), 5 -A trivalent or higher polyvalent polyphenol such as chlorisatin bisphenol, 5,7-dichloroisatin bisphenol, 5-bromoisatin bisphenol What is necessary is just to substitute with a rehydroxy compound. The amount of the polyhydroxy compound to be substituted is usually 0.01 to 10 mol%, preferably 0.1 to 2 mol% of the aromatic dihydroxy compound.

  Furthermore, monovalent aromatic hydroxy compounds can be used as molecular weight regulators, specifically m- and p-methylphenol, m- and p-propylphenol, p-bromophenol, p-tert. -Butylphenol, p-long chain alkyl-substituted phenol and the like.

  The viscosity average molecular weight of the aromatic polycarbonate resin (A) used in the present invention is a value calculated from a solution viscosity measured at 25 ° C. using methylene chloride as a solvent, and is preferably 16,000 to 38,000, 000-35,000 is more preferable. Moreover, the aromatic polycarbonate resin (A) used by this invention may be a 2 or more types of mixture, if the viscosity average molecular weight of the said range is satisfy | filled.

(B) Ultraviolet Absorber The resin composition of the present invention is characterized by containing a specific polymer type ultraviolet absorber. The ultraviolet absorber (B) of the present invention is an ultraviolet absorber made of an acrylic copolymer, and includes general ultraviolet absorbers such as benzotriazole compounds, benzophenone compounds, and triazine compounds, and methyl methacrylate. It is a copolymer obtained by copolymerizing an acrylic monomer such as.

  By blending this specific acrylic copolymer UV absorber (B), discoloration during melt processing and after UV irradiation is suppressed, the hue is improved, and gas generated during melt molding is suppressed. It becomes possible to do.

  The ultraviolet absorber (B) of the present invention is, among others, at least selected from a copolymer obtained by copolymerizing a benzotriazole compound or a benzophenone compound, that is, a benzotriazole acrylic copolymer and a benzophenone acrylic copolymer. One ultraviolet absorber is preferred.

  A benzotriazole-based compound is a compound having a benzotriazole skeleton and derivatives thereof, and can be selected from commonly used ultraviolet absorbers. In order to copolymerize with an acrylic monomer, A compound having a hydroxyl group as a substituent is preferred.

  Specific examples of the benzotriazole compound include 2- (2′-hydroxy-5′-tert-butylphenyl) benzotriazole, 2- (2′-hydroxy-3 ′, 5′-di-tert). -Butylphenyl) benzotriazole, 2- (2'-hydroxy-3'-tert-butyl-5'-methylphenyl) -5-chlorobenzotriazole, 2- (2'-hydroxy-3 ', 5'-di-tert-butylphenyl) -5-chlorobenzotriazole and the like.

  The benzophenone compound to be copolymerized with the acrylic monomer is a compound having a benzophenone skeleton and a derivative thereof, and a compound having a hydroxyl group as a substituent for copolymerization with the acrylic monomer is preferable. .

  Specific examples of the benzophenone compounds include 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-octoxybenzophenone, 2-hydroxy-4-dodecyloxybenzophenone, and the like. .

  As the ultraviolet absorbent (B) of the present invention, among those described above, a benzotriazole acrylic copolymer is preferable because a light diffusing member having a good initial hue and a hue after ultraviolet irradiation can be obtained.

  Examples of the acrylic monomer copolymerized with the above-described compound include methyl acrylate, ethyl acrylate, methyl methacrylate, and ethyl methacrylate.

  Composition ratio of benzotriazole compound and / or benzophenone compound and acrylic monomer in (B) UV absorber of the present invention (benzotriazole compound and / or benzophenone compound: acrylic monomer) ) Is usually 80:20 to 20:80, preferably 70:30 to 30:70, more preferably 60:40 to 40:60.

  (B) The compounding quantity of a ultraviolet absorber is 0.05-20 weight part with respect to 100 weight part of aromatic polycarbonate resin (A), Preferably it is 0.1-10 weight part, More preferably, it is 0.5. ~ 5 parts by weight. (B) If the ultraviolet absorber exceeds 20 parts by weight, the strength as a light diffusing member tends to be insufficient, and if it is less than 0.05 parts by weight, the effect of suppressing discoloration and generated gas becomes insufficient. Tend.

(C) Fine particles The present invention is characterized in that the resin composition is mixed with fine particles (C) in which a fluorescent dye is dispersed. By blending the (C) fine particles, it is possible to suppress gas generated during melt molding.

  As the fine particles (C), various inorganic or organic particles used as a light diffusing agent can be used, and are not particularly limited, but the weight average particle size is usually 0.7 to 30 μm. Fine particles. Here, the measurement of a weight average particle diameter is performed by the Coulter method (Coulter Multisizer), for example. When the fine particles (C) having a weight average particle diameter of less than 0.7 μm are blended, the light diffusion property of the obtained resin composition is inferior, the light source is seen through, and the visibility tends to be inferior. On the contrary, fine particles having a particle diameter exceeding 30 μm have a low diffusion effect with respect to the added amount. As a weight average particle diameter of microparticles | fine-particles (C), Preferably it is 1-20 micrometers, More preferably, it is the range of 2-10 micrometers.

  Examples of inorganic fine particles include barium sulfate, talc, calcium carbonate, silica, and glass, and examples of organic fine particles include silicone resins, acrylic resins, benzoguanamine resins, styrene resins, butadiene resins, Or the microparticles | fine-particles which consist of these copolymers and a core-shell type polymer are mentioned. Among these fine particles, an acrylic resin is preferable from the viewpoint that the fluorescent dye can be easily dispersed, and an acrylic resin having a crosslinked structure is particularly preferable in view of solvent resistance and heat resistance.

  The crosslinkable monomer added when producing the acrylic resin having a crosslinked structure is not particularly limited. For example, one molecule such as ethylene glycol dimethacrylate, trimethylolpropane tri (meth) acrylate, and divinylbenzene. A monomer having two or more vinyl groups therein is preferred. These crosslinkable monomers may be used alone or in combination of two or more, and the use ratio thereof is preferably 5 to 50% by weight with respect to the total monomers.

In addition, the fine particles (C) of the present invention have a refractive index difference (Δn) of 0.01 or more from the aromatic polycarbonate resin (A) in terms of light diffusibility, and the polycarbonate resin (A). Are preferably incompatible fine particles. Here, the refractive index is a value with respect to light of d-line (587.562 nm, He) at a temperature of 25 ° C. The actual measurement shows that the refractive index (n _pc ) of the polycarbonate resin is V-block method (Kalnew The refractive index (n _ld ) of the fine particles is determined by the Becke method (method compared with a standard solution). Since the refractive index of the polycarbonate resin made from bisphenol A, which is preferably used in the present invention, is about 1.58, it is preferable to select fine particles having a difference of 0.01 or more. Moreover, even if the refractive index difference is 0.01 or more, the light diffusibility is insufficient, the light source can be seen through, and the visibility may be inferior. More preferably, it is 0.07 or more.

  As the fluorescent dye dispersed in the fine particles of the present invention, a white or blue fluorescent dye is preferably used. Specific examples include white organic light emitters and blue organic light emitters known as fluorescent brighteners and organic EL. A fluorescent whitening agent is a white or blue fluorescent dye blended in a molded product in order to make the molded product appear brighter, and has a function of eliminating the yellowness of the molded product and increasing the brightness. The function is similar to the bluing agent in terms of eliminating the yellowness of the molded product, but the bluing agent simply removes the yellow light of the molded product, whereas the fluorescent whitening agent has a wavelength of less than 400 nm. It differs in that it absorbs ultraviolet rays and changes its energy into visible light having a wavelength of 400 nm or more, particularly blue-violet light.

  As the fluorescent brightening agent, known fluorescent brightening agents for thermoplastic resins can be used. Among them, from the viewpoint of heat resistance, those having a molecular weight of 300 to 1000 are preferable, for example, benzoxazole-based Compounds and coumarin compounds are preferred.

  Specific examples of the benzoxazole-based compound include 4- (benzoxazol-2-yl) -4 ′-(5-methylbenzoxazol-2-yl) stilbene and 4,4′-bis (benzoxazole-2). -Yl) stilbene, 4,4′-bis (benzoxazol-2-yl) furan and the like, among others, stilbene benzoxazoles such as 4,4′-bis (benzoxazol-2-yl) stilbene Compounds are preferred.

  Specific examples of the coumarin compound include 3-phenyl-7-aminocoumarin, 3-phenyl-7- (imino-1 ′, 3 ′, 5′-triazine-2′-diethylamino-4′-chloro). -Coumarin, 3-phenyl-7- (imino-1 ', 3', 5'-triazine-2'-diethylamino-4'-methoxy) -coumarin, 3-phenyl-7-naphthotriazole coumarin, 4-methyl- Examples thereof include 7-hydroxycoumarin, and among them, phenylallyl triazolyl coumarin-based compounds such as 3-phenyl-7-naphthotriazole coumarin are preferable.

  Examples of white organic light emitters and blue organic light emitters include distyryl biphenyl-based blue fluorescent light-emitting materials, arylethynylbenzene-based blue fluorescent light-emitting materials, quinkipyridine-based fluorescent light-emitting materials, sexiphenyl-based blue fluorescent light-emitting materials, and dimesi. Examples thereof include tilboryl anthracene-based fluorescent light-emitting materials and quinacridone-based fluorescent light-emitting materials.

  Among the fluorescent dyes described above, fluorescent whitening agents selected from benzoxazole-based compounds and coumarin-based compounds are preferred from the viewpoint of thermal stability.

  The amount of the fluorescent dye dispersed in the fine particles (C) is such that the concentration of the fluorescent dye in the resin composition of the present invention is 0.00001 to 1% by weight, further 0.001 to 0.8% by weight, particularly 0. The amount is preferably in the range of 0.01 to 0.5% by weight. If the content of the fluorescent dye is less than 0.00001% by weight, the function of erasing the yellowishness of the molded product and enhancing the brightness and the function of absorbing ultraviolet rays and emitting to the visible blue-violet color are not sufficiently exhibited. On the other hand, even if the content exceeds 1% by weight, no further effect of addition is observed.

  The amount of the fluorescent dye dispersed in the fine particles is determined in consideration of the content of the fluorescent dye in the resin composition and the amount of the fine particles (C) to be blended in the resin composition. As the concentration in the fine particles, Usually, it is 0.001 to 5 weight%, Preferably it is 0.01 to 1.0 weight%, More preferably, it is 0.05 to 0.5 weight%.

  The method for dispersing the fluorescent dye in the fine particles is not particularly limited, and various known methods can be employed. For example, when an acrylic resin is used as the fine particles, a monomer composition to which a fluorescent dye is added is dispersed or emulsified in a solvent and polymerized (suspension polymerization, emulsion polymerization, seed polymerization, etc.), or in solution Fine particles (C) in which a fluorescent dye is dispersed can be easily obtained by a method such as a dispersion polymerization method in which a monomer composition to which a fluorescent dye is added is dissolved and a polymer is precipitated by polymerization.

  As the monomer composition in the case of using an acrylic resin as fine particles, a (meth) acrylic acid ester monomer can be used. For example, acrylic acid esters such as methyl acrylate and n-butyl acrylate, methacrylic acid Examples thereof include methacrylic acid esters such as methyl and n-butyl methacrylate, and among them, acrylates having 1 to 8 carbon atoms in the ester moiety are preferable. These monomers may be used alone or in combination of two or more, and the (meth) acrylic acid ester monomer is contained in a proportion of 50 to 95% in all monomers. Those are preferred. The monomer may be added with another monomer copolymerizable with a (meth) acrylic acid ester monomer. Examples of such other monomer include styrene, p. -Monomers having a vinyl group such as methylstyrene and vinyl acetate.

  In this invention, the compounding quantity of this microparticles | fine-particles (C) in a resin composition is 0.05-20 weight part with respect to 100 weight part of aromatic polycarbonate resin (A), Preferably it is 0.5-10. Part by weight, more preferably 1.0 to 5.0 parts by weight. If the amount of the fine particles (C) is too small, the light diffusibility is insufficient. On the other hand, if the amount is too large, the light transmittance tends to decrease.

  The resin composition of the present invention contains the above-mentioned (A) to (C) as essential components, but further contains a phosphorus heat stabilizer in order to improve the light transmittance and hue of the resin composition. preferable. As the phosphorus heat stabilizer, phosphites and phosphates are preferable.

  Examples of phosphites include triphenyl phosphite, trisnonylphenyl phosphite, tris (2,4-di-tert-butylphenyl) phosphite, trinonyl phosphite, tridecyl phosphite, and trioctyl phosphite. , Trioctadecyl phosphite, distearyl pentaerythritol diphosphite, tricyclohexyl phosphite, monobutyl diphenyl phosphite, monooctyl diphenyl phosphite, distearyl pentaerythritol diphosphite, bis (2,4-di-tert -Butylphenyl) pentaerythritol phosphite, bis (2.6-di-tert-butyl-4-methylphenyl) pentaerythritol phosphite, 2,2-methylenebis (4,6-di-tert) Butylphenyl) triesters of phosphorous acid such as octyl phosphite, diesters and monoesters, and the like.

  Examples of phosphate esters include trimethyl phosphate, triethyl phosphate, tributyl phosphate, trioctyl phosphate, triphenyl phosphate, tricresyl phosphate, tris (nonylphenyl) phosphate, 2-ethylphenyl diphenyl phosphate, tetrakis (2,4-di-). tert-butylphenyl) -4,4-diphenylene phosphonite.

  Among these phosphorus heat stabilizers, distearyl pentaerythritol diphosphite, bis (2,4-di-tert-butylphenyl) pentaerythritol phosphite, bis (2.6-di-tert-butyl-4) Phosphites such as -methylphenyl) pentaerythritol phosphite and tris (2,4-di-tert-butylphenyl) phosphite are preferred, and bis (2,6-di-tert-butyl-4-methylphenyl) is particularly preferred ) Phosphites such as pentaerythritol phosphite and tris (2,4-di-t-butylphenyl) phosphite are particularly preferred. In addition, a phosphorus heat stabilizer may be used independently and may be used in combination of 2 or more type.

  In this invention, the compounding quantity of the phosphorus type heat stabilizer in a resin composition is 0.005-0.2 weight part normally with respect to 100 weight part of aromatic polycarbonate resin (A), Preferably it is 0.01-0. 0.1 part by weight, more preferably 0.02 to 0.05 part by weight. If the amount of the phosphorus-based heat stabilizer is less than 0.005 parts by weight, the effect as a heat stabilizer is small, and if it exceeds 0.2 parts by weight, no further effect of addition is seen, but rather hydrolysis occurs. It tends to be easier.

  Various additives can be further blended in the resin composition of the present invention as long as the effects of the present invention are not impaired. For example, an antioxidant, a release agent, an antistatic agent, a colorant, a heat stabilizer, a fluidity improver, a flame retardant, an anti-aggregation agent, and the like may be added. Among these, it is preferable to use at least one selected from an antioxidant, a heat stabilizer, and a flame retardant.

  The production method of the light diffusing resin composition according to the present invention is not particularly limited, and the above-mentioned components (A) to (C), the heat stabilizer added as necessary, and predetermined amounts of other additives Are preferably mixed and further kneaded. In mixing and kneading, a method applied to a normal thermoplastic resin is adopted, for example, a ribbon blender, a Henschel mixer, a Banbury mixer, a drum tumbler, a single screw extruder, a twin screw extruder, a multi screw extruder. A machine can be used. The temperature condition of kneading is usually 230 to 300 ° C, preferably 235 to 280 ° C, more preferably 240 to 260 ° C.

  In molding using the resin composition of the present invention, a general thermoplastic resin molding method can be used. For example, from the viewpoint of productivity, injection molding, injection compression molding, or injection molding from a pellet-shaped resin composition Extrusion molding is possible, and the extruded sheet-like molded product can be further subjected to vacuum forming, pressure forming, or the like to obtain a desired light diffusing member.

  Examples of the light diffusing member of the present invention include lighting covers, lighting signs, transmissive screens, various displays, light diffusing sheets and light diffusing plates for liquid crystal display devices, and light diffusing sheets and light used for liquid crystal display devices among others. It is suitable as a diffusing plate, and in particular, can be suitably used as a diffusing plate for a large liquid crystal television.

  In addition, in order to improve the light diffusibility, the surface of the light diffusive member of the present invention may be subjected to unevenness processing such as embossing, V-groove processing, and ridge processing by a known method. By applying these processes, the amount of fine particles added can be reduced while maintaining the light diffusibility.

EXAMPLES Hereinafter, although an Example demonstrates this invention still in detail, this invention is not limited to a following example, unless the summary is exceeded.
[material]
Table 1 shows the raw materials used in Examples and Comparative Examples.

[Methods for measuring and evaluating physical properties of resin composition]
(1) Viscosity average molecular weight (Mv):
Using an Ubbelohde viscometer, the intrinsic viscosity [η] at 20 ° C. was measured using methylene chloride as a solvent, and the viscosity average molecular weight was determined from the following formula.

[Η] = 1.23 × 10 ⁻⁴ × (Mv) ^0.83

(1) Total light transmittance and haze:
Using a turbidimeter (“NDH-2000 type” manufactured by Nippon Denshoku Industries Co., Ltd.), the total light transmittance (%) and haze (%) of the test pieces molded in Examples and Comparative Examples were measured.

(2) Diffusion rate:
Using a GP-5 GONIOPHOTOMETER manufactured by MURAKAMI COLOR RESEARCH LABORATORY, the brightness of each test piece was measured under the following conditions, and the diffusivity (%) was determined by the following equation.
Measurement conditions: incident light 0 °, tilt angle 0 °, light receiving range 0 ° to 90 °, luminous flux stop 2.0,
Receiving aperture 3.0
Diffusion rate (%) = {(20 ° luminance value + 70 ° luminance value) / (5 ° luminance value × 2)} × 100

(3) Initial hue (YI):
Using the test pieces molded in Examples and Comparative Examples, the initial hue (YI) was measured with a spectroscopic colorimeter (“SE-2000 type” manufactured by Nippon Denshoku Industries Co., Ltd.).
(4) Hue after UV irradiation (YI):
Using a Super Xenon Weather Meter manufactured by Suga Test Instruments Co., Ltd., the test pieces molded in Examples and Comparative Examples were irradiated with ultraviolet rays at an irradiation intensity of 156 W / m ² for 600 hours, and then the hue (YI) was applied in the same manner as (3). It was measured.
(5) Gas generated during molding In Examples and Comparative Examples, the amount of gas generated after the test piece plate was molded was observed.

[Examples 1-3 and Comparative Examples 1-3]
After mixing each raw material in the ratio shown in Table 2, it is melt-kneaded at a cylinder temperature of 250 ° C. by a single screw extruder with a screw diameter of 40 mm (“VS-40” manufactured by Tanabe Plastics Machinery Co., Ltd.) to cut the strand. Thus, a pellet of the resin composition was obtained. The obtained pellets were dried with a hot air circulation dryer at 120 ° C. for 5 to 7 hours.

  Using the dried pellets, a 90 mm × 50 mm × 2 mm thick plate was formed at a temperature of 300 ° C. and a forming cycle of 40 sec by an injection molding machine (“J50” manufactured by Nippon Steel Works). Using this plate as a test piece, the above-described evaluation was performed, and the results are shown in Table 2.

From Table 2, the following becomes clear.
(1) Comparing Example 1 and Comparative Example 1, in Example 1 in which an ultraviolet absorber of a benzotriazole acrylic copolymer was blended with an aromatic polycarbonate resin, total light transmittance, haze and diffusivity The initial hue and the hue after ultraviolet irradiation are also excellent, but the amount of gas generated during molding is less than that of Comparative Example 1 using an ultraviolet absorber that is not an acrylic copolymer.

(2) Comparing Example 1 and Comparative Example 3, in Example 1 in which fine particles in which a fluorescent dye is dispersed are blended with an aromatic polycarbonate resin, the amount of gas generated during molding is small, and the initial hue and ultraviolet irradiation The later hue is also good.

Claims (5)

  UV absorber (B) 0.05 to 20 parts by weight of an acrylic copolymer and fine particles (C) 0.05 to 0.005 dispersed with a fluorescent dye with respect to 100 parts by weight of the aromatic polycarbonate resin (A) A resin composition for a light diffusing member, comprising 20 parts by weight.   The resin composition for a light diffusing member according to claim 1, wherein the ultraviolet absorber (B) is selected from a benzotriazole acrylic copolymer and a benzophenone acrylic copolymer.   The resin composition for a light diffusing member according to claim 1, wherein the fine particles (C) are an acrylic resin having a crosslinked structure.   The resin composition for a light diffusing member according to any one of claims 1 to 3, wherein the fluorescent dye dispersed in the fine particles (C) is a fluorescent whitening agent selected from a benzoxazole-based compound and a coumarin-based compound.   A light diffusing member obtained by melt-molding the resin composition for a light diffusing member according to claim 1.