JPH09279001A - Polycarbonate resin composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve a problem that the light-shielding properties of a molding obtained from a conventional titanium-oxide-containing polycarbonate resin composition is relatively low, therefore when a reflector made from the polycarbonate resin composition serves also as the housing of a lighting unit used in such a manner that a light source is directly placed on it or the holder or reflector of a light source, the image of the light source is seen from the back (the side opposite to that on which the light source is set) unless the reflector has a thick wall. SOLUTION: This composition comprises 100 pts.wt. in total, polycarbonate resin and titanium oxide, the amount of the titanium oxide being 10-25wt.%, based on the total of the polycarbonate resin and the titanium oxide, 0.001-5 pts.wt., per 100 pts.wt. total of the polycarbonate resin and the titanium oxide, polycarbonate resin stabilizer and 0.01-3 pts.wt. light-diffusing agent.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a polycarbonate resin composition, and more particularly to a polycarbonate resin composition containing titanium oxide.

[0002]

2. Description of the Related Art Illumination devices such as guide lights (emergency lights), display lights such as advertising lights, and backlights of liquid crystal display devices,
Conventionally, a reflector such as a reflector has been used. And
In recent years, a polyethylene terephthalate foamed film (hereinafter abbreviated as “PET foamed film”) or a polycarbonate resin composition has been widely used as the reflector.

The above-mentioned PET foam film is obtained by foaming PET with a white content added to form microvoids, thereby having a high reflection function. P
Since the reflector made of the ET foam film is in the form of a film, the light from the light source relatively easily leaks from the PET foam film to the outside, and as a result, the reflector made of the polycarbonate resin composition was used. The brightness (illumination rate) of the lighting device is more likely to decrease than in the case.

On the other hand, the above-mentioned polycarbonate resin composition contains a polycarbonate resin, a white pigment (mainly titanium oxide) and a polycarbonate resin stabilizer, and the reflector comprising the polycarbonate resin composition is composed of a white pigment. It utilizes the reflection effect of light. Since the light-shielding property of this reflector can be adjusted by adjusting the thickness thereof, it is possible to obtain an illuminating device having higher brightness (illumination rate) than when a reflector made of a PET foam film is used. Is. As a reflector made of a polycarbonate resin composition containing titanium oxide, the content of titanium oxide is currently 8 to 12% by weight.
Some things have been put to practical use.

Although the use as a reflector material is not specifically mentioned, Japanese Patent Publication No. 63-26140 discloses that a polycarbonate resin, a specific polycarbonate resin stabilizer and titanium dioxide are contained. Content of titanium dioxide is 0.00 relative to polycarbonate resin
A polycarbonate resin composition is disclosed which is from 1 to 10% by weight. Further, JP-A-6-200140 discloses a polycarbonate resin composition containing a polycarbonate resin, a white pigment and a specific polycarbonate resin stabilizer, and the content of the white pigment is about 0.01 to 16.7% by weight. The thing is disclosed. And US Pat. No. 53
Japanese Patent No. 91600 discloses a polycarbonate resin composition containing a polycarbonate resin, a white pigment and a specific polycarbonate resin stabilizer, and the content of the white pigment is about 0.001 to 33% by weight.

[0006]

In order to reduce the thickness and weight of the illuminating device or to reduce the number of parts, a reflector such as a reflector also serves as a housing of the illuminating device or a holder or reflector of the light source. However, when a conventional reflector made of a polycarbonate resin composition also serves as a holder or reflector for a housing of a lighting device or a light source, in particular, a housing or reflector or holder for use in which the light source is directly arranged thereon. If the thickness of the light source is also doubled, the shadow of the light source can be seen through from the back side of the reflector (the side opposite to the side on which the light source is arranged. The same applies below).

In a reflector made of a polycarbonate resin composition containing titanium oxide as a white pigment, by increasing the content of titanium oxide in the polycarbonate resin composition, light is shielded without increasing its thickness. It is possible to improve the property. However, in the conventional polycarbonate resin composition used as the material of the reflector, when the light source is directly arranged, the reflection of the same thickness as the conventional one having a light-shielding property such that the shadow of the light source cannot be seen through from the back side. If the content of titanium oxide is increased before the container is obtained, silver (silver strip) will be generated during the molding process. As a result, the appearance of the reflector is impaired.

An object of the present invention is to provide a polycarbonate resin composition capable of obtaining a thin-walled molded product which has little or no silver (silver strip) during molding and has a high light-shielding property. To do.

[0009]

In the polycarbonate resin composition of the present invention which achieves the above object, a polycarbonate resin and titanium oxide are contained in a proportion of 10 to 2 of the titanium oxide.
5 parts by weight of 100 parts by weight in total, and 0.001 to 5 parts by weight of a polycarbonate resin stabilizer with respect to 100 parts by weight of the polycarbonate resin and the titanium oxide, and light diffusion. It is characterized by containing 0.01 to 3 parts by weight of each agent.

[0010]

Embodiments of the present invention will be described below in detail. As described above, the polycarbonate resin composition of the present invention contains a total of 100 parts by weight of the polycarbonate resin and titanium oxide such that the ratio of the titanium oxide is 10 to 25% by weight. The polycarbonate resin can be easily produced by reacting a dihydric phenol with phosgene or a carbonic acid ester compound in the presence of an acid acceptor or a terminal terminating agent, and the kind thereof is not particularly limited.

Examples of the above dihydric phenol include hydroquinone, 4,4'-dihydroxydiphenyl and bis (4
-Hydroxyphenyl) alkane, bis (4-hydroxyphenyl) cycloalkane, bis (4-hydroxyphenyl) oxide, bis (4-hydroxyphenyl) sulfide, bis (4-hydroxyphenyl) sulfone,
Examples thereof include bis (4-hydroxyphenyl) ketone, 9,9-bis (4-hydroxyphenyl) fluorene, and halogen derivatives thereof. Among them, bisphenol A,
That is, 2,2-bis (4-hydroxyphenyl) propane is suitable.

Examples of the carbonic acid ester compound include diaryl carbonate such as diphenyl carbonate, and dialkyl carbonate such as diethyl carbonate and dimethyl carbonate.

The end terminator may have any structure as long as it is a monohydric phenol, and is not particularly limited. Specific examples of the terminal terminator include p-tert-butylphenol, p-tert-octylphenol, p-cumylphenol, phenol, p-
tert-amylphenol, p-nonylphenol, p-
Examples include cresol, tribromophenol, p-bromophenol, 4-hydroxybenzophenone and the like.
One type of terminal stopper may be used alone, or two or more types may be used in combination.

As the polycarbonate resin, those having a branched structure may be used, and the branching agent used for obtaining the polycarbonate resin having the branched structure is 1,1,1-tris (4-hydroxyphenyl). Ethane, α, α ′, α ″ -tris (4-hydroxyphenyl) -1,3,5-triisopropylbenzene, 1-
(Α-methyl-α- (4′-hydroxyphenyl) ethyl) -4- (α ′, α′-bis (4 ″ -hydroxyphenyl) ethyl) benzenephloroglucin, trimellitic acid, isatin bis (o-cresol) For example, compounds having three or more functional groups are suitable.

The polycarbonate resin used in the present invention preferably has a viscosity average molecular weight of 10,000 to 40,000. In the case of a polycarbonate resin composition using a polycarbonate resin having a viscosity average molecular weight of less than 10,000, the impact resistance of the molded article when formed into a molded article is low. On the other hand, in a polycarbonate resin composition using a polycarbonate resin having a viscosity average molecular weight exceeding 40,000, molding becomes difficult. The viscosity average molecular weight of the polycarbonate resin is more preferably 12,000 to 35,000, further preferably 15,000 to 30,000.

On the other hand, the titanium oxide used in combination with the above-mentioned polycarbonate resin may be either rutile type or anatase type, but it is preferable to use rutile type because it is excellent in thermal stability and weather resistance. preferable. In order to suppress the thermal decomposition of the polycarbonate resin, it is preferable that the titanium oxide be treated with various surface treating agents to cover the surface. As the surface treatment agent, hydrated alumina, silica, zinc, etc. are usually used.

The shape of titanium oxide is not particularly limited, and can be appropriately selected from scale-like shape, spherical shape, amorphous shape and the like. The particle size is preferably about 0.2 to 5 μm. In order to improve the dispersibility of the titanium oxide in the resin, a silicone oil, a polyol or the like can be used.

The compounding amount of the above-mentioned titanium oxide is 100 in total of the titanium oxide and the above-mentioned polycarbonate resin.
10-25% by weight (10-25 parts by weight)
It is preferable that With a polycarbonate resin composition containing less than 10% by weight of titanium oxide, it becomes difficult to obtain a thin molded product having high light-shielding properties. Also, 2
In a polycarbonate resin composition containing titanium oxide in an amount of more than 5% by weight, the occurrence frequency of silver increases when the polycarbonate resin composition is molded into a desired shape. Total 100 of polycarbonate resin and titanium oxide
The more preferable ratio of titanium oxide in the parts by weight is 15
-20% by weight.

The "thin molded product having a high light-shielding property" referred to in the present invention has a total light transmittance of about 0.2 at a thickness of 1 mm.
% Means a molded product having a content of not more than%. Further, the “total light transmittance” referred to in the present specification means that measured based on the method described in JIS K 7105. The lower the total light transmittance, the higher the light shielding property.

The polycarbonate resin composition of the present invention comprises
In addition to the polycarbonate resin and titanium oxide, it contains a polycarbonate resin stabilizer. Here, the term “polycarbonate resin stabilizer” as used in the present invention means a substance capable of suppressing a decrease in the molecular weight of the polycarbonate resin, which is caused by blending titanium oxide with the polycarbonate resin. When the molecular weight of the polycarbonate resin is reduced, the physical properties inherent to the polycarbonate resin are significantly reduced, and the thermal stability of the polycarbonate resin in the molding machine is reduced to cause oxidation and yellowing. When a reflector is manufactured using a polycarbonate resin composition in which the polycarbonate resin has turned yellow, the reflectance of the reflector decreases.

The kind of the polycarbonate resin stabilizer is not particularly limited, and phosphorus compounds, alkoxy group-containing organosiloxanes, organohydrogensiloxanes, alkoxysilane compounds, epoxy compounds and the like can be used. Specific examples of the above phosphorus compounds include (2,4-di-tert-butylphenyl) biphenylene diphosphonite, trimethyl phosphate, benzylphosphonate, organic phosphonate, organic phosphonate, alkylphosphonic acid. Dialkyl ester and the like can be mentioned.

Specific examples of the above-mentioned organosiloxane containing an alkoxy group include organopolysiloxane containing an organooxysilyl group bonded to a silicon atom via a divalent hydrocarbon group. Specific examples of the above-mentioned organohydrogensiloxane include polyorganohydrogensiloxane and end-capped polyorganohydrogensiloxane.

Specific examples of the above-mentioned alkoxysilane compound include methyltrimethoxysilane and alkylaminosilane. And, as specific examples of the above-mentioned epoxy compound, epoxy resin, epoxidized soybean oil,
3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate and the like.

Among these polycarbonate resin stabilizers, from the viewpoint that the generation of silver during molding can be suppressed to a relatively low level even if the concentration of titanium oxide in the polycarbonate resin composition is increased, it contains an alkoxy group. The organosiloxane is particularly preferred.

The above polycarbonate resin stabilizers may be used alone or in combination of two or more. In any case, the total amount of the polycarbonate resin stabilizer is preferably 0.001 to 5 parts by weight with respect to 100 parts by weight of the total amount of the polycarbonate resin and titanium oxide described above. If it is less than 0.001 part by weight, the effect of suppressing the decrease in the molecular weight of the polycarbonate resin caused by blending the titanium oxide with the polycarbonate resin is small. On the other hand, if it exceeds 5 parts by weight, depending on the type of the polycarbonate resin stabilizer, poor dispersion of titanium oxide and coloring of the polycarbonate resin stabilizer itself may occur. In some cases, the reflectivity may be reduced.

The more preferable compounding amount of the polycarbonate resin stabilizer based on 100 parts by weight of the total amount of the polycarbonate resin and titanium oxide depends on the kind of the polycarbonate resin stabilizer and the compounding amount of titanium oxide, but is about 0.1. ~ 2 parts by weight.

The polycarbonate resin composition of the present invention is
In addition to the polycarbonate resin, titanium oxide, and polycarbonate resin stabilizer, it contains a light diffusing agent. This light diffusing agent is a useful component for reducing the total light transmittance of the molded article made of the polycarbonate resin composition without substantially reducing the total light reflectance. By using this light diffusing agent, the content of titanium oxide in the polycarbonate resin composition that can be molded into a thin molded body having high light-shielding property and high Y value (total 100 parts by weight of polycarbonate resin and titanium oxide) It is possible to reduce the ratio (titanium oxide) to 10% by weight.

Here, the "Y value" referred to in this specification is J
This means the stimulus value Y (unit:%) when the tristimulus values X, Y, Z for the color of the sample (molded product) are obtained by the spectrophotometric method according to the method described in IS K 7105. The Y value corresponds to the luminance rate or the luminous reflectance. Y above
The value is, for example, MS2 manufactured by Macbeth.
It can be measured using 020 plus.

The light diffusing agent may be made of a solid which is optically transparent and has a refractive index different from that of the above-mentioned polycarbonate resin, and the particle diameter thereof is generally 0.2 to 5.
Preferably, it is 0 μm. Specific examples thereof include acrylic beads, silica beads, silicone resin beads and glass beads, hollow beads of the same material as these, amorphous powder, and plate-like powder.

The acrylic beads have an average diameter of 0.2 to
About 20 μm is preferable, and silica beads having an average diameter of about 2 to 20 μm, particularly 2 to 5 μm
It is preferably made of high-purity synthetic silica having a true spherical shape of m. Moreover, as the silicone resin beads, those having an average diameter of about 0.5 to 20 μm are preferable. As the glass beads, various glass beads such as those made of low alkali glass (E glass) and those having high refractive index glass (having a refractive index of about 1.9 to 2.2) can be used. Can be made, but the average diameter of E glass, which is inexpensive, is 5
.About.50 .mu.m, more preferably about 5 to 7 .mu.m, and most preferably about 10 to 12 .mu.m. Whichever beads are used, the beads are preferably monodisperse beads, and are preferably spherical beads having a retroreflective function.

From the viewpoint that it is easy to obtain a polycarbonate resin composition which can be molded into a molded product having a high light-shielding property and a high Y value, silica beads, glass beads, and a crystallinity excellent in a light diffusing function are used as the light diffusing agent. Irregular powders of the material, especially crystalline silica powders, are particularly preferred.

As the light diffusing agent, only one kind may be used, or 2
More than one species may be used in combination. In any case, the total amount of the light diffusing agent is preferably 0.01 to 3 parts by weight based on 100 parts by weight of the total of the polycarbonate resin and titanium oxide described above. If the amount is less than 0.01 parts by weight, it becomes difficult to obtain a polycarbonate resin composition that can be molded into a thin molded product having high light-shielding properties. On the other hand, a polycarbonate resin composition containing more than 3 parts by weight of a light diffusing agent may cause a decrease in reflectance when formed into a reflector.

The compounding amount of the light diffusing agent with respect to 100 parts by weight of the total of the above-mentioned polycarbonate resin and titanium oxide is
It can be appropriately selected according to the type of the light diffusing agent, the amount of titanium oxide compounded, the intended use of the polycarbonate resin composition, and the like. When trying to obtain a polycarbonate resin composition that can be molded into a thin molded body having a high light-shielding property, it is preferable to increase the compounding amount of the light diffusing agent as the compounding amount of titanium oxide decreases. . In this case,
For example, when the content of titanium oxide is 10% by weight, the content of the light diffusing agent is preferably 1 part by weight or more, and the content of titanium oxide is 15 to 20% by weight.
Is 0.1 to 1.5,
It is particularly preferred to use parts by weight.

The polycarbonate resin composition of the present invention comprises:
In addition to the above-mentioned components, various fillers, additives, other synthetic resins, elastomers and the like can be blended, if necessary, within a range that does not impair the object of the present invention. Specific examples of the above fillers include fibrous fillers such as glass fiber, carbon fiber, potassium titanate whiskers, mineral fibers, wollastonite, talc, mica, glass flakes,
Examples include plate-like fillers such as clay.

Specific examples of the above-mentioned additives include antioxidants such as hindered phenol type, phosphite type, and phosphoric acid type, ultraviolet absorbers such as benzotriazole type and benzophenone type, and hindered amine type. Such as light stabilizers, aliphatic carboxylic acid ester-based, paraffin-based, internal lubricants such as silicone oil and polyethylene wax, or commonly used flame retardants, flame retardant aids, release agents, antistatic agents, colorants, etc. To be

Specific examples of the other synthetic resin include polyester (polyethylene terephthalate, polybutylene terephthalate, etc.), polyamide, polyarylate, polyethylene, polypropylene, polymethylmethacrylate, polystyrene, ABS resin, AS resin and the like. Specific examples of the above elastomer include isobutylene-isoprene rubber, styrene-butadiene rubber, ethylene-propylene rubber, acrylic elastomer, and MBS and MAS which are core-shell type elastomers.
And the like.

The polycarbonate resin composition of the present invention is
It can be obtained by mixing each of the components described above in predetermined amounts and kneading. At this time, a commonly used method for compounding and kneading, such as a ribbon blender,
A method using a Henschel mixer, a drum tumbler, a single-screw extruder, a twin-screw extruder, a co-kneader, a multi-screw extruder can be applied, and the kneading temperature is appropriately selected within a range of 220 to 300 ° C. It is possible. The blending amount of each component is appropriately selected within the above-mentioned range depending on the intended use of the polycarbonate resin composition and the like.

A molded article using the polycarbonate resin composition of the present invention is prepared by blending and kneading each component in a predetermined amount in the same manner as in the case of obtaining a molded article from a conventional polycarbonate resin composition. After the resin composition is obtained, it can be obtained by molding the polycarbonate resin composition as it is into a desired shape by a method such as injection molding, blow molding, extrusion molding, compression molding, calender molding, and rotary molding. Alternatively, it can also be obtained by once obtaining a pellet made of the polycarbonate resin composition of the present invention, and then molding the pellet into a desired shape by the above method or the like. Molding temperature is approximately 2
It can be appropriately selected within the range of 60 to 300 ° C. When a mold is used for molding, the temperature of the mold can be appropriately selected within a range of approximately 80 to 120 ° C.

When a molded product is obtained using the polycarbonate resin composition of the present invention, there is no silver or little silver, so that a molded product having a good appearance can be obtained. Y value of is approximately 93% or more.
The total light transmittance of this molded product at a thickness of 1 mm is about 0.2 although it depends on the composition of the polycarbonate resin composition.
% Or less. Therefore, when the polycarbonate resin composition of the present invention is used as a material for a reflector, a reflector exhibiting a good appearance can be obtained, and an illumination device provided with this reflector is a conventional reflector. It has a brightness (illumination rate) equal to or higher than that of a lighting device including.

If the total light transmittance of the molded product is 0.2% or less at a thickness of 1 mm, the thickness of the molded product is 2-3 m.
By setting m, when a light source having a brightness of about 20000 cd / m ² is directly arranged on the light source, the shadow of the light source will not be seen through from the back surface side of the molded body. Therefore, when the polycarbonate resin composition of the present invention is used as a material for a reflector, it has a light-shielding property such that the shadow of the light source cannot be seen through from the back side even when the light source is directly arranged thereon. A thin reflector can be obtained. When the reflector also serves as the housing of the illuminating device or the holder or reflector of the light source, the illuminating device can be made thinner and lighter, or the number of parts can be easily reduced.

The polycarbonate resin composition of the present invention having the above-mentioned characteristics is used as an indicator lamp such as a guide lamp (emergency lamp) and an advertisement lamp, and a lighting device such as a backlight of a liquid crystal display device, an illuminated push switch, a photoelectric switch and the like. It is suitable as a material for a reflector used in.

[0042]

EXAMPLES Hereinafter, examples of the present invention will be described with reference to comparative examples, but the raw materials used in the examples and comparative examples will be described in advance. (1) Polycarbonate resin Tafflon FN1900A (bisphenol A type polycarbonate resin (homopolymer); viscosity average molecular weight 22,000) manufactured by Idemitsu Petrochemical Co., Ltd.

(2) Titanium oxide CR63 (rutile type titanium oxide powder surface-treated with alumina hydrate) manufactured by Ishihara Sangyo Co., Ltd.

(3) Polycarbonate resin stabilizer (i) Organopolysiloxane containing organooxysilyl group bonded to silicon atom through divalent hydrocarbon group BY1 manufactured by Toray Dow Corning Silicone Co., Ltd.
6-160 (ii) Polyorganohydrogen siloxane SH manufactured by Toray Dow Corning Silicone Co., Ltd.
1107

(4) Light diffusing agent (i) Glass beads EMB20 (average particle size 1) manufactured by Toshiba Ballotini Co., Ltd.
5 μm) (ii) Silica beads P-500 (average particle size 2 μm) manufactured by Catalyst Kasei Co., Ltd. (iii) Crystalline silica powder S9-2 (average particle size 2 μm) manufactured by Izumitec Co., Ltd.

Examples 1 to 7 (1) Production of Polycarbonate Resin Composition A polycarbonate resin, titanium oxide, a polycarbonate resin stabilizer and a light diffusing agent were blended in the proportions shown in Table 1 and dry blended. Then, the mixture was kneaded at a cylinder temperature of 280 ° C. using a vented twin-screw extruder (TEM-35 manufactured by Toshiba Machine Co., Ltd.) to obtain pellets composed of the polycarbonate resin composition of the present invention for each example.

(2) Measurement of optical properties of molded product The pellet obtained in (1) above was dried at 120 ° C. for 8 hours, and then injection-molded at a molding temperature of 280 ° C. and a mold temperature of 90 ° C. A first test piece composed of a flat plate of 25 × 35 × 1 mm and a second test piece composed of a flat plate of 150 × 150 × 3 mm were obtained for each example. In addition, as a mold for obtaining the first test piece, a mold whose surface was mirror-polished with water paper (# 1000) was used.

The total light transmittance and the Y value of the first test piece were measured. At this time, the total light transmittance is measured by using SZ Sigma 90 manufactured by Nippon Denshoku Industries Co., Ltd., and the Y value is M manufactured by Macbeth.
It measured using S2020 plus. On the other hand, for the second test piece, a cold-cathode tube having a diameter of 4 mm (HMB manufactured by Harrison Electric Co., Ltd .; brightness 20000 cd / m ² ) was placed so that its glass tube surface was in contact with one surface of the test piece. In this state, when the cold cathode tube was turned on, it was determined whether or not the shadow of the cold cathode tube was visually recognized from the back surface side of the test piece. Furthermore, the presence or absence of silver was visually determined. Table 2 shows the results.

Comparative Examples 1 to 4 Examples 1 to 1 except that the amounts shown in Table 1 were used for the respective components.
After the polycarbonate resin composition was manufactured for each comparative example in the same manner as in Example 7 (1), the first test piece and the second test piece were prepared in the same manner as in Examples 1 to 7 (2) for each comparative example. The test piece of was obtained. And about these test pieces, it carried out similarly to Example 1- Example 7 (2), and total light transmittance and Y.
The value was measured, and the presence or absence of see-through of the cold cathode tube and the presence or absence of silver were determined. Table 2 shows the results.

Reference Example 1 With respect to a commercially available PET foam film (Ref White RW188 manufactured by Kimoto Co., Ltd .; thickness 190 μm), total light transmittance and Y value were measured in the same manner as in Examples 1 to 7 (2). At the same time as the measurement, the presence or absence of see-through of the cold cathode tube was determined. Table 2 shows the results.

[0051]

[Table 1]

[0052]

[Table 2]

As shown in Table 2, Examples 1 to 7
In the first test pieces obtained respectively, the total light transmittance was as low as 0.06-0.14%, and the Y value was 95.2-9.
It is as high as 7.8%. Further, in the second test pieces obtained in each of these examples, the shadow of the cold cathode tube could not be visually recognized from the back surface side. Further, in these second test pieces, silver is not generated, or even if there is little silver. Therefore, each of the polycarbonate resin compositions produced in Examples 1 to 7 is suitable as a material for a reflector having a good appearance, and by using these polycarbonate resin compositions, a housing of a lighting device or a light source. It is also possible to fabricate a thin-walled reflector that doubles as a holder or reflector.

On the other hand, in the polycarbonate resin composition of Comparative Example 1 in which the content of titanium oxide was as small as 5 parts by weight, the total light transmittance of the first test piece obtained from the polycarbonate resin composition was 0.48%. Since it is high and the Y value is as low as 92.3%, it is not preferable as a material for the reflector. Furthermore, in the second test piece obtained from this polycarbonate resin composition, the shadow of the cold cathode tube could be visually recognized from the back surface side. Further, the polycarbonate resin composition of Comparative Example 2 in which the content of titanium oxide is within the limited range of the present invention but the content of the light diffusing agent is as large as 4 parts by weight gives a molded product having a low total light transmittance. However, the Y value of the first test piece is as low as 92.5%. Therefore, Comparative Example 2
The polycarbonate resin composition of is not preferable as a material for a reflector.

The content of titanium oxide is as large as 30 parts by weight,
Moreover, although the polycarbonate resin composition of Comparative Example 3 containing no light diffusing agent can obtain a molded product having a low total light transmittance and a high Y value, silver is intensely generated during the molding process. did. Therefore, Comparative Example 3
The above polycarbonate resin composition is not practical. The compounding amount of titanium oxide is within the limited range of the present invention, but the polycarbonate resin composition of Comparative Example 4 containing no light diffusing agent can obtain a molded article having a high Y value. The total light transmittance of the test piece of No. 1 was relatively high at 0.24%, and the shadow of the cold cathode tube could be visually recognized from the back surface side of the second test piece. Therefore, the polycarbonate resin composition of Comparative Example 4 is not preferable as a material for obtaining a thin reflector having a high light-shielding property.

[0056]

As described above, the polycarbonate resin composition of the present invention makes it possible to obtain a thin-walled molded product which has little or no silver during molding and has a high light-shielding property. Another polycarbonate resin composition. Therefore, according to the present invention, it is possible to provide a reflector that exhibits a good appearance and can obtain a brightness (illumination rate) equal to or higher than that of a conventional reflector.
Furthermore, it is possible to provide a thin-walled reflector that doubles as the housing of the lighting device or the holder or reflector of the light source, which makes it easy to reduce the thickness and weight of the lighting device or reduce the number of parts. Become.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masaya Okamoto 1 Inezaki Kaigan, Ichihara-shi, Chiba Idemitsu Petrochemical Co., Ltd.

Claims (5)

[Claims] 1. A total of 100 parts by weight of a polycarbonate resin and titanium oxide such that the ratio of the titanium oxide is 10 to 25% by weight, and a total of 100 parts by weight of the polycarbonate resin and the titanium oxide. On the other hand, a polycarbonate resin composition comprising 0.001 to 5 parts by weight of a polycarbonate resin stabilizer and 0.01 to 3 parts by weight of a light diffusing agent, respectively. 2. The polycarbonate resin composition according to claim 1, wherein the polycarbonate resin stabilizer is an organosiloxane containing an alkoxy group. 3. The polycarbonate resin composition according to claim 1, wherein the polycarbonate resin stabilizer is an organohydrogensiloxane. 4. The polycarbonate resin according to claim 1, wherein the molded product has a total light transmittance of 0.2% or less when molded into a molded product having a thickness of 1 mm. Composition. 5. The polycarbonate resin composition according to claim 1, wherein the Y value of the molded product when molded into a molded product having a thickness of 1 mm is 93% or more.