JP2006063121A - Light-diffusing resin composition and light-diffusing member obtained using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light-diffusing resin composition simultaneously satisfying high light diffusibility and high total light transmittance, and a light-diffusing member using the same. <P>SOLUTION: The light-diffusing resin composition comprises 100 pts.wt. of an aromatic polycarbonate resin and, incorporated therewith, 0.01-2 pts.wt. of a polyorganosiloxane bearing a phenyl group at least on its side chain and having viscosity at 25°C of 1-1,000 cSt, and 0.05-2 pts.wt. of silicone-based diffusing fine particles having a weight-average particle size of 0.7-5 μm. The light-diffusing member is obtained using the same. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a light diffusing resin composition and a light diffusing member, and in particular, has excellent mechanical properties, thermal properties, electrical properties, weather resistance, and further has excellent light diffusibility and Light diffusing resin composition having high light transmittance and suppressing discoloration during melt processing, useful as a light diffusing sheet for lighting covers, lighting signs, transmissive screens, various displays, liquid crystal display devices, and the like The present invention relates to a light diffusing member obtained from a diffusing resin composition.

  Polycarbonate resin 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, providing light diffusibility. By doing so, it can be suitably used for applications requiring light diffusibility, 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, the 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 strength is low. For example, the mechanical strength is 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. However, in this method, as described in Examples 1 to 3, the haze is as low as less than 96%, and the polymethyl methacrylate fine particles are inferior in practicality because the hue of transmitted light is yellowish. there were.

  Patent Document 2 is composed of a composition in which 0.05 to 0.5 parts by weight of fine particles having an average particle size of 5 to 20 μm are blended with 100 parts by weight of a polycarbonate resin, and the total light transmittance is 85%. Although a high transmittance light diffusing plate made of polycarbonate resin having a diffuse transmittance of 10 to 30% has been disclosed above, the light diffusing plate has low light diffusibility and inferior practicality.

  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.

  Patent Document 4 discloses a film having a thickness of 30 to 300 μm formed of a composition comprising 100 parts by weight of a polycarbonate resin and 1 to 20 parts by weight of particles having an average particle diameter of 1 to 25 μm, and has a total light transmittance of 92%. A polycarbonate resin high transmission light diffusion film having a haze (cloudiness) of 60% or more, and more preferably a polycarbonate resin high transmission light diffusion film having an uneven pattern on the film surface is disclosed. Yes. In order to form a concavo-convex pattern on the surface of the film, a method is generally used in which a concavo-convex pattern is transferred by clamping and pressing with a cooling roll or the like having a concavo-convex pattern during film production. Production on the roll surface increases the production cost, and the uneven surface pattern of the roll surface wears out over long periods of time, resulting in changes in the total light transmittance and haze of the film over time. is doing. Moreover, although the thickness of the film currently disclosed by this patent document 4 is 30-300 micrometers, optical properties, such as the total light transmittance and haze of a film and a molded product of thickness exceeding 300 micrometers, are not mentioned. .

  Patent Document 5 discloses 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 0.005 to 0.1% by weight of optical brightener. Although a light diffusion plate for a direct backlight of a polycarbonate resin having a thickness of 0.5 to 3.0 mm formed from a resin composition consisting of parts is disclosed, although there is a description of optical properties, a fluorescent brightener Since the brightness is improved by using, the thermal stability is insufficient, discoloration at the time of molding, extrusion, and discoloration at the time of recycling are likely to occur, and the practicality is low.

In addition, none of the molded articles made of the resin compositions of Patent Documents 1 to 5 have high light transmittance and high light diffusivity at the same time, and the surface is glaring and has poor visibility. It was.
Patent Document 6 and Patent Document 7 propose methylphenylpolysiloxane as a material that can maintain transparency and impart releasability even when added to polycarbonate. However, it does not describe at all that it is used as a light diffusing resin, and in that case, it has an effect of improving transmittance and luminance.

Japanese Patent Laid-Open No. 03-143950 Japanese Patent Laid-Open No. 05-257002 JP 2000-169695 A JP 2003-240921 A JP 2004-029091 A JP-A-10-219090 JP-A-11-293101

  The present invention solves all the problems of the prior art, and provides a light diffusing resin composition having high light diffusibility and high total light transmittance at the same time, and a light diffusing member using the same. .

  As a result of intensive studies, the inventors have blended polyorganosiloxane having a specific structure and viscosity and silicone-based diffusing fine particles having a specific particle size at a specific ratio, thereby improving the original properties of the resin. The present invention has been completed by finding a diffusive resin that simultaneously satisfies high light diffusivity and high total light transmittance and has a good hue of transmitted light without loss.

  That is, the gist of the present invention is that 0.01 to 2 parts by weight of a polyorganosiloxane having a phenyl group at least in a side chain and having a viscosity of 1 to 1000 cSt at 25 ° C. with respect to 100 parts by weight of an aromatic polycarbonate resin, And a light diffusing resin composition comprising 0.05 to 2 parts by weight of silicone-based diffusing fine particles having a weight average diameter of 0.7 to 5 μm, and the light diffusing resin composition. It exists in the light diffusing member.

The light diffusing resin composition of the present invention does not impair the original characteristics of the aromatic polycarbonate resin, and further has no white turbidity or a decrease in transmittance, and has high light diffusivity and high total light transmittance at the same time. In addition, since the color of transmitted light is good, discoloration during melt processing is suppressed, and there is little discoloration due to ultraviolet rays emitted from the light source, so a light diffusing sheet for lighting covers, lighting signs, transmissive screens, various displays, and liquid crystal display devices It can be used in a wide range of applications that require light diffusivity, such as light diffusion plates.

Hereinafter, the present invention will be described in detail.
The polycarbonate resin according to the present invention is obtained by an interfacial polymerization method of an aromatic dihydroxy compound or a small amount of a polyhydroxy compound and phosgene, or the above aromatic dihydroxy compound or a small amount of the polyhydroxy compound and , An aromatic polycarbonate polymer which may be branched and is produced by a transesterification reaction with a carbonic acid 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). Bis (4-hydroxyphenyl) alkane-based dihydroxy compounds such as 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 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, and 5,7-dichlorois A trihydroxy or higher polyhydroxy compound 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.

As for the molecular weight of the polycarbonate resin used in the present invention, the viscosity average molecular weight measured from the viscosity of the methylene chloride solution at 25 ° C. is 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 polyorganosiloxane used in the present invention is a polyorganosiloxane having a phenyl group in at least a side chain and a viscosity at 25 ° C. of 1 to 1000 cSt, and can be easily obtained by a known organic synthesis reaction. .
As the polyorganosiloxane, those having a branched siloxane structure are preferable because the effects of the present invention are high.
Furthermore, the polyorganosiloxane of the present invention preferably has a structure represented by the following general formula (1).

（式（１）中のＲ_１は、それぞれ独立に、水素原子、アルキル基、アリール基から選ばれた基であり、Ｒ_２はフェニル基を示す。ｍは１以上、ｎは０以上の整数を示す。）

(R ₁ in Formula (1) is a group independently selected from a hydrogen atom, an alkyl group, and an aryl group, R ₂ represents a phenyl group, m is 1 or more, and n is an integer of 0 or more. Is shown.)

  In the polyorganosiloxane having the general formula (1), the kinematic viscosity at 25 ° C. is 1 to 1000 cSt, preferably 5 to 200 cSt, and more preferably 10 to 50 cSt. When the kinematic viscosity is less than 1 cSt, the amount of gas generated during molding increases, and molding defects due to gas, for example, unfilling, gas burnout, and transfer defects may occur. On the other hand, when the kinematic viscosity exceeds 1000 cSt, the effect of improving the hue and transmittance of the aromatic polycarbonate cannot be sufficiently obtained.

  Further, as described above, the polyorganosiloxane used in the present invention is required to have a phenyl group at least in the side chain, and preferably has a branched siloxane structure. Those having a low refractive index are most preferable as long as they do not impair the transparency. This is effective in order to make the light diffusing member, which is an application of the present invention, have a high transmittance.

  In this invention, said polyorganosiloxane is 0.01-2 weight part with respect to 100 weight part of aromatic polycarbonate resin, Preferably it is 0.02-1 weight part, More preferably, it is 0.04-0.7 weight. Part. When the use ratio of the polyorganosiloxane is less than 0.01 parts by weight, the effect of improving the transmittance and hue of the aromatic polycarbonate resin cannot be sufficiently obtained. When the use ratio exceeds 2 parts by weight, the aromatic is not aromatic. Although the hue and transmittance of the polycarbonate resin are good, molding defects due to gas, such as unfilling, gas burnout, and transfer defects, occur.

The silicone-based diffusing fine particles used in the present invention are not particularly limited as long as they are spherical fine particles having a siloxane bond and have a weight average diameter of 0.7 to 5 μm. When the particle size is less than 0.7 μm, sufficient light diffusibility cannot be obtained. When the particle diameter is larger than 5 μm, the amount of addition for obtaining the desired light diffusibility increases, and a decrease in physical properties is inevitable. Examples of silicone-based diffusing fine particles that can be generally used include silica, silicone resin, silicone rubber, and combinations thereof.
In particular, if the impact resistance is improved and high diffusibility and high transmittance are obtained, the silicone-based diffusing fine particles are preferably silicone rubber. Silicone rubber can be obtained by, for example, crosslinking vinyl group-containing silicone oil with hydrogen siloxane as disclosed in JP-A Nos. 61-283649 and 10-195149.

In the present invention, the silicone-based diffusing fine particles are 0.05 to 2 parts by weight, preferably 0.05 to 1.5 parts by weight, and more preferably 0.1 to 1 part by weight with respect to 100 parts by weight of the aromatic polycarbonate resin. is there. When the usage rate of the silicone-based diffusing fine particles is less than 0.05 parts by weight, sufficient light diffusibility cannot be obtained, and when the usage rate exceeds 2 parts by weight, sufficient transmittance can be obtained. Absent.
The light diffusing resin composition of the present invention includes, for example, an ultraviolet absorber, an antioxidant, a white or blue fluorescent dye, a release agent, an antistatic agent, a colorant, a heat stabilizer, a fluid as necessary. You may add a property improving agent, a flame retardant, an aggregation inhibitor, etc. Among these, it is preferable to use at least one of an ultraviolet absorber, an antioxidant, a white or blue fluorescent dye, a heat stabilizer, and a flame retardant.

Examples of UV absorbers include benzotriazole UV absorbers, benzophenone UV absorbers, triazine UV absorbers, oxanilide UV absorbers, malonic ester UV absorbers, hindered amine UV absorbers, and the like. . Specific examples include 2- (2-hydroxy-5-tert-octylphenyl) benzotriazole, 2- (3-tert-butyl-5-methyl-2-hydroxyphenyl) -5-chlorobenzotriazole, 2 -(5-methyl-2-hydroxyphenyl) benzotriazole, 2- [2-hydroxy-3,5-bis (α, α-dimethylbenzyl) phenyl] -2H-benzotriazole, 2,2′-methylenebis (4 -Cumyl-6-benzotriazolphenyl), 2,2'-p-phenylenebis (3,1-benzoxazin-4-one), p-phenylenebis (1,3-benzoxazin-4-one), propa Nedioic acid [(4-methoxyphenyl) -methylene] -dimethyl ester and the like can be mentioned.
In the present invention, in order to prevent the resulting light diffusing resin composition and the light diffusing member from being colored, it is preferable to use an ultraviolet absorber having a small transmittance at a wavelength of 380 nm to 400 nm. Absorbents are preferably used. Examples of the malonic acid ester ultraviolet absorber include 2- (1-arylalkylidene) malonic acid esters, which are commercially available from Clariant Japan under the trade names PR-25 and B-CAP. . 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 0.01 to 2% by weight in the resin composition.

As examples of white or blue fluorescent dyes, known fluorescent brighteners for thermoplastic resins can be used. Of these, high molecular weight compounds are preferred, for example, stilbene benzoxazole, phenyl allyl Examples include triazolyl coumarin-based fluorescent brighteners. Also, known white organic light emitters and blue organic light emitters can be used for organic EL. For example, distyryl biphenyl blue light emitting material, arylethynylbenzene blue fluorescent light emitting material, kinkipyridine light emitting material, sexiphenyl blue light emitting material. Examples thereof include luminescent materials, dimesitylboryl anthracene-based luminescent materials, and quinacridone-based luminescent materials. The amount of the fluorescent dye used is preferably in the range of 0.0001 to 0.1% by weight in the resin composition.
In order to increase the whiteness, a white pigment such as titanium oxide may be further added.

  The mixing and kneading of the resin composition for a light diffusing plate according to the present invention may be performed by a method applied to a normal thermoplastic resin. 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 or the like can be used. The temperature condition for kneading is usually 260 to 300 ° C.

For molding using the light diffusing resin composition of the present invention, a general thermoplastic resin molding method can be used. For example, injection molding from a pellet-shaped resin composition, injection compression molding from the viewpoint of productivity. Further, extrusion molding is possible, and further, vacuum forming, pressure forming, and the like from the extruded sheet-like molded product can be performed to obtain a target 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, among which light diffusing sheets for liquid crystal display devices and It can be suitably used as a light diffusing plate, particularly as a diffusing plate for large liquid crystal televisions.
Further, the light diffusing member of the present invention may be subjected to uneven processing on the surface such as embossing, V-groove processing, and ridge-like processing by a known method in order to increase the light diffusibility. By applying these processes, the amount of the light diffusing agent 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. The raw materials and evaluation methods used in the following examples are as follows. In addition, the symbol “M” described in the column of “trade name and content” in Table 1 means the viscosity average molecular weight, and “n” means the degree of polymerization.

(1) Viscosity average molecular weight:
The intrinsic viscosity [η] at 20 ° C. in methylene chloride was measured using an Ubbelohde viscometer, and determined from the following formula.
[Η] = 1.23 × 10 ⁻⁴ × (Mv) ^0.83
(2) Hue (YI) and total light transmittance, haze:
Each of the above measurements was performed on a plate (90 mm × 50 mm × 3 mm thickness) molded at a temperature of 300 ° C. by an injection molding machine (“J50” manufactured by Nippon Steel Works). A spectroscopic colorimeter (“SE-2000 type” manufactured by Nippon Denshoku Industries Co., Ltd.) is used for measuring YI, and a turbidimeter (“NDH-2000 type manufactured by Nippon Denshoku Industries Co., Ltd.”) is used for measuring total light transmittance and haze. ")It was used.
(3) Measurement of diffusivity Measurement was performed on the molded plate. The diffusivity was determined from the following colors. For the measurement of the luminance value, GP-5 GONIOPHOTOMETER manufactured by MURAKAMI COLOR RESEARCH LABORATORY was used. The measurement conditions were as follows: incident light 0 °, tilt angle 0 °, light receiving range 0 ° to 90 °, light beam stop 2.0, and light receiving stop 3.0.
(4) UV irradiation Light resistance evaluation was performed about the above-mentioned shaping | molding plate. As the irradiation apparatus, a Super Xenon Weather Meter manufactured by Suga Test Instruments Co., Ltd. was used. The irradiation intensity was 156 W / m ² and the irradiation time was 600 hours.
Diffusion rate (%) = {(20 ° luminance value + 70 ° luminance value) / (5 ° luminance value × 2)} × 100

Examples 1-11 and Comparative Examples 1-7
After blending the raw materials at the ratios shown in Table 2, Table 3, and Table 4, the cylinder temperature was 250 ° C. using a single screw extruder with a vent with a screw diameter of 40 mm (“VS-40” manufactured by Tanabe Plastics Machinery Co., Ltd.). The mixture was melt-kneaded to obtain pellets by strand cutting. The obtained pellets were dried at 120 ° C. for 5 to 7 hours with a hot-air circulating drier, and then molded for evaluation under the above conditions. And said evaluation was performed and the result was shown to each table | surface.

Claims (6)

0.01 to 2 parts by weight of a polyorganosiloxane having a phenyl group at least in a side chain and having a viscosity of 1 to 1000 cSt at 25 ° C. and a weight average diameter of 0.7 with respect to 100 parts by weight of an aromatic polycarbonate resin A light diffusing resin composition comprising 0.05 to 2 parts by weight of ˜5 μm silicone-based diffusing fine particles. The light diffusing resin composition according to claim 1, wherein the polyorganosiloxane is a polyorganosiloxane having a branched siloxane structure. The light-diffusing resin composition according to claim 1 or 2, wherein the polyorganosiloxane has a structure represented by the following general formula (1).

(R ₁ in Formula (1) is a group independently selected from a hydrogen atom, an alkyl group, and an aryl group, R ₂ represents a phenyl group, m is 1 or more, and n is an integer of 0 or more. Is shown.) The light diffusing resin composition according to any one of claims 1 to 3, wherein the silicone-based diffusing fine particles are silicone-based diffusing fine particles obtained by crosslinking vinyl group-containing silicone oil with hydrogen siloxane. The light-diffusing resin composition according to any one of claims 1 to 4, comprising 0.05 to 5 parts by weight of a malonic ester-based ultraviolet absorber with respect to 100 parts by weight of the polycarbonate resin. A light diffusing member using the light diffusing resin composition according to any one of claims 1 to 5.