JP2002156511A - Light reflector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light reflector capable of ensuring uniform luminance without lowering luminance. SOLUTION: The light reflector is obtained by molding a polycarbonate resin composition containing (a) a polycarbonate resin, (b) titanium oxide powder and (c) an organosiloxane and satisfies the expression [glossiness (85 deg.)]/[glossiness (20 deg.)]>2 with respect to its surface glossiness.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a light reflector,
More specifically, the present invention relates to a light reflector suitable as a reflector for a liquid crystal display backlight or a reflection frame.

[0002]

2. Description of the Related Art Polycarbonate resins are excellent in mechanical properties (particularly, impact resistance), electrical properties, transparency and the like.
It is widely used in various fields such as A equipment, electric / electronic equipment, and construction. Among these fields of use, particularly in the use of a reflector for a liquid crystal display backlight, characteristics such as high reflectivity, light-shielding property, and light resistance are required. An application has been filed for a polycarbonate composition suitable for the above (JP-A-10-36656).

[0003] However, in recent years, as the colorization, definition and brightness of liquid crystal displays have progressed, there has been an increasing demand for higher brightness of backlights for liquid crystal displays. In such a case, a sufficient luminance cannot be uniformly exhibited. In general, it is well known that the reflector surface is mirror-finished in order to increase the brightness, but at that time, the brightness unevenness directly below the cold cathode tubes used for illumination and between the valleys of the cold cathode tubes and the cold cathode tubes. To increase the size and uniformity, the brightness must be sacrificed by a thicker diffusion sheet.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a light reflector capable of obtaining a uniform luminance under such circumstances without deteriorating the luminance.

[0005]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to achieve the above object, and as a result, have found that the gloss (85)
It has been found that the light reflector obtained by controlling the ratio of the glossiness (20 °) to the glossiness (20 °) can be suitable for the purpose.
The present invention has been completed based on such findings.

That is, the gist of the present invention is as follows. 1. A light reflector obtained by molding a polycarbonate resin composition containing (a) a polycarbonate resin, (b) a titanium oxide powder and (c) an organosiloxane, wherein the glossiness of the surface of the light reflector is represented by the following formula: (1) A light reflector characterized by satisfying: glossiness (85 °) / glossiness (20 °)> 2 (1). 2. When the polycarbonate resin composition contains the component (a) 100
2. The light reflector according to the above 1, wherein 0.01 to 30 parts by mass of the component (b) and 0.001 to 5 parts by mass of the component (c) are blended with respect to parts by mass. 3. The light according to 1 or 2, which satisfies the following expression (2): glossiness (85 °) / glossiness (20 °)> 5 (2) regarding the glossiness of the surface of the light reflector. Reflector. 4. The light reflector according to any one of the above items 1 to 3, wherein the organosiloxane (c) is a reactive group-containing organopolysiloxane. 5. 5. The light reflector according to the above 4, wherein the reactive group is an alkoxy group, a hydroxyl group or hydrogen. 6. 6. The light reflector according to any one of 1 to 5, wherein the light reflector is a reflector for a liquid crystal display backlight or a reflection frame.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail. In the polycarbonate composition as a raw material of the light reflector of the present invention, as the polycarbonate resin used as the component (a), various ones can be mentioned, and the polycarbonate resin represented by the general formula (I)

[0008]

Embedded image

A polymer having a repeating unit having the structure represented by the following formula is preferred. In the above general formula (I), X ¹ and X ² each represent a linear, branched or cyclic alkyl group having 1 to 6 carbon atoms, and specific examples include a methyl group,
Ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, tert-butyl group, n-amyl group, isoamyl group, n-hexyl group, isohexyl group,
Examples thereof include a cyclopentyl group and a cyclohexyl group. X ¹ and X ² may be the same or different. a and b are X ¹ and X, respectively.
² represents the number of substitutions, and is an integer of 0 to 4. When plural X ^1, a plurality of X ¹ may be the same as or different from each other, if X ² is plural, X ² may be the same with or different from each other.

Y is a single bond, an alkylene group having 1 to 8 carbon atoms (for example, methylene group, ethylene group, propylene group, butylene group, pentylylene group, hexylene group, etc.), an alkylidene group having 2 to 8 carbon atoms (for example, ethylidene group) , Isopropylidene group, etc.), a cycloalkylene group having 5 to 15 carbon atoms (eg, cyclopentylene group, cyclohexylene group, etc.), a cycloalkylidene group having 5 to 15 carbon atoms (eg, cyclopentylidene group, cyclohexylidene group, etc.) ), - S -, - SO -, - SO 2 -, - O -, - CO
-Bond or formula (II-1) or formula (II-2)

[0011]

Embedded image

The bond represented by The polymer is usually represented by the general formula (III)

[0013]

Embedded image

(Where X ¹ , X ² , a, b and Y are
Same as above. ), And a carbonate precursor such as phosgene or a carbonate compound. That is, for example, in a solvent such as methylene chloride, in the presence of a known acid acceptor or molecular weight regulator, by the reaction of a dihydric phenol with a carbonate precursor such as phosgene, or in the presence or absence of a solvent, It can be produced by a transesterification reaction between a polyhydric phenol and a carbonate precursor such as a carbonate compound.

As the dihydric phenol represented by the general formula (III), various ones can be mentioned. Especially 2,
2-bis (4-hydroxyphenyl) propane [commonly known as
Bisphenol A] is preferred. Examples of the dihydric phenol other than bisphenol A include bis (4-hydroxyphenyl) methane; 1,1-bis (4-hydroxyphenyl) ethane; and bis (4 such as 1,2-bis (4-hydroxyphenyl) ethane. -Hydroxyphenyl) alkane, 1,1-bis (4-hydroxyphenyl) cyclohexane; bis (4-hydroxyphenyl) cycloalkane such as 1,1-bis (4-hydroxyphenyl) cyclodecane, 4,4′-dihydroxydiphenyl , Bis (4-hydroxyphenyl) oxide, bis (4-hydroxyphenyl) sulfide, bis (4-hydroxyphenyl) sulfone, bis (4-hydroxyphenyl) sulfoxide, bis (4-hydroxyphenyl) ether, bis (4-hydroxyphenyl) ether (Hydroxyphenyl) ketone etc. be able to. In addition, examples of the dihydric phenol include hydroquinone. These dihydric phenols may be used alone or in combination of two or more.

Examples of the carbonate include diaryl carbonates such as diphenyl carbonate, and dialkyl carbonates such as dimethyl carbonate and diethyl carbonate. When reacting the dihydric phenol with the carbonate precursor to produce a polycarbonate, a molecular weight modifier can be used as necessary. The molecular weight regulator is not particularly limited, and those conventionally used in the production of polycarbonate can be used. Such materials include, for example, phenol, p-cresol, p-tert
-Butylphenol, p-tert-octylphenol, p-cumylphenol, p-nonylphenol, p
Monohydric phenols such as dodecylphenol.

The polycarbonate resin of the component (a) may be a homopolymer using one of the above-mentioned dihydric phenols, or a copolymer using two or more of the above-mentioned dihydric phenols. Further, it may be a thermoplastic random branched polycarbonate resin obtained by using a polyfunctional aromatic compound in combination with the dihydric phenol. The polyfunctional aromatic compound is generally referred to as a branching agent and includes 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] benzene, phloroglucin, trimellitic acid, isatin bis (o-cresol), and the like.

Further, a polycarbonate-polyorganosiloxane copolymer comprising an organosiloxane block having a number average degree of polymerization of 5 or more may be used. Further, a mixture of two or more kinds of various polycarbonate resins may be used. In the composition of the raw material of the present invention,
The polycarbonate resin used as the component (a)
In view of mechanical strength, particularly Izod impact strength and moldability, the viscosity average molecular weight is 13,000 to 30,000.
Are preferred, and particularly those in the range of 15,000 to 25,000. The viscosity-average molecular weight (Mv) was determined by measuring the viscosity of a methylene chloride solution at 20 ° C. using an Ubbelohde viscometer, and calculating the intrinsic viscosity [η] therefrom. [Η] = 1.23 × 10 ^-5 It is a value calculated by the equation of Mv ^0.83 .

Polycarbonate resins having such properties include, for example, Teflon FN3000A and FN2500.
A, FN2200A, FN1900A, FN1700
A, commercially available as an aromatic polycarbonate resin such as FN1500A (trade name, manufactured by Idemitsu Petrochemical Co., Ltd.). In the resin composition of the raw material of the present invention, the titanium oxide powder used as the component (b) is made of a polycarbonate resin of the component (a), which has essentially low reflectivity (high transparency), and has low transparency and high whiteness. And has the effect of imparting high reflectivity and improving the flame retardancy of the polycarbonate resin.

Titanium oxide as the component (b) is used in the form of fine powder for the purpose of imparting low transparency and high reflectivity to the polycarbonate resin of the component (a) as described above. Powdered titanium oxide can be produced by either the chlorine method or the sulfuric acid method.
The titanium oxide used in the present invention may be either a rutile type or an anatase type, but a rutile type is preferred in terms of thermal stability, weather resistance and the like. Further, the shape of the fine powder particles is not particularly limited, and can be appropriately selected and used, such as flaky, spherical, amorphous and the like.

The titanium oxide used as the component (b) is a hydrated oxide of aluminum and / or silicon,
Those surface-treated with an amine compound, a polyol compound or the like are preferable. This treatment improves the uniform dispersibility in the polycarbonate resin composition and the stability of the dispersed state. Examples of the hydrated oxides of aluminum and silicon, the amine compound and the polyol compound include hydrated alumina, hydrated silica, triethanolamine and trimethylolethane.

The treatment method itself in the above-mentioned surface treatment is not particularly limited, and an arbitrary method is appropriately adopted.
The amount of the surface treatment agent imparted to the surface of the titanium oxide particles by this treatment is not particularly limited, but the light reflectivity of the titanium oxide and 1 to 1 with respect to the titanium oxide in consideration of the moldability of the polycarbonate resin composition. About 15% by mass is appropriate.

In the composition of the present invention, the particle diameter of the titanium oxide powder used as the component (b) is not particularly limited, but in order to exhibit the above-mentioned effects efficiently, the average particle diameter is preferably 0. What is necessary is to use the thing of 0.01-5.0 micrometers, More preferably, it is 0.05-1.0 micrometers. In the raw material composition of the present invention, an organosiloxane is used as the component (c). There are various types of the organosiloxane, and examples of the reactive group include an organosiloxane containing an alkoxy group, a hydroxyl group, or hydrogen. Among them, an alkoxy group-containing organopolysiloxane is preferable. Specifically, the alkoxy group contains an organooxysilyl group bonded directly or via a divalent hydrocarbon group to a silicon atom, and includes linear, cyclic, network, and the like. A straight-chain organopolysiloxane having a partly branch is exemplified. Particularly, a linear organopolysiloxane is preferable.

Examples of the organopolysiloxane containing an organooxysilyl group in which an alkoxy group is bonded to a silicon atom directly or via a divalent hydrocarbon group include, for example, compounds represented by the following general formula (IV):

[0025]

Embedded image

[Wherein R ¹ represents a monovalent hydrocarbon group;
Is a monovalent hydrocarbon group, an alkoxy group (—OR ⁴ ) or a general formula (V) —R ² SiR ³ _x (OR ⁴ ) _(3-x) (V) (wherein R ² is divalent R ³ and R ^{4 each} represent a monovalent hydrocarbon group, and x is an integer of 0 to 2). However, at least one of A in one molecule
Is a monovalent hydrocarbon group containing an alkoxy group or an organooxysilyl group. M is an integer of 1 to 300;
n is an integer of 0 to 300, and m + n is 1 to 300
Is an integer. And a linear organopolysiloxane represented by the following formula:

Here, in the general formula (IV), specific examples of the monovalent hydrocarbon group represented by R ¹ include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group and a hexyl group. Alkenyl groups such as alkyl group, vinyl group, allyl group, butenyl group, pentenyl group and hexenyl group;
An aryl group such as a phenyl group, a tolyl group and a xylyl group, and an aralkyl group such as a benzyl group and a phenethyl group are exemplified. A specific example of the monovalent hydrocarbon group represented by A is
It is the same as in the case of R ¹ above.

On the other hand, in the general formula (V), examples of the divalent hydrocarbon group represented by R ² include an alkylene group such as a methylene group, an ethylene group, a propylene group and a butylene group. The monovalent hydrocarbon groups represented by R ³ and R ⁴ are the same as those described above, and specific examples of the organooxysilyl group-containing monovalent hydrocarbon group include trimethoxysilylethylene and triethoxysilyl. Examples include an ethylene group, a dimethoxyphenoxysilyl propylene group, a trimethoxysilylpropylene group, a trimethoxysilylbutylene group, a methyldimethoxysilylpropylene group, and a dimethylmethoxysilylpropylene group.

The molecular weight of such an organopolysiloxane is not particularly limited, and since it is possible to suppress a decrease in the molecular weight of the polycarbonate resin in the polycarbonate resin composition, m and n in the general formula (IV) are And m is an integer of 1 to 300, and n is 0 to
It is preferable that the integer is 300 and m + n is an integer of 1 to 300.

Further, such an organopolysiloxane can be obtained by various methods. For example, it can be produced by an addition reaction of an organopolysiloxane having a silicon-bonded hydrogen atom and an organooxysilyl group with a hydrocarbon compound having an aliphatic unsaturated hydrocarbon bond in the presence of a platinum-based catalyst. Further, it can be produced by an addition reaction between a hydrocarbon group-containing organopolysiloxane having an aliphatic unsaturated hydrocarbon bond and an organooxysilane having a silicon-bonded hydrogen atom in the presence of a platinum-based catalyst.

The organosiloxane as the component (c) may be used alone or in combination of two or more. The resin composition as a raw material of the light reflector of the present invention contains the above-mentioned components (a), (b) and (c). 0.01-30 parts by mass, more preferably 0.1-20 parts by mass, of titanium oxide powder as component (b) and 0.001-5 parts by mass of organosiloxane as component (c) based on 100 parts by mass of resin. Parts, more preferably 0.01 to 3 parts by mass.

If the amount of the component (b) is less than 0.01 parts by mass, sufficient whiteness may not be obtained. . Also,
If the amount exceeds 30 parts by mass, the whiteness may not be improved in spite of the increase in specific gravity, and it is not necessary to add the amount exceeding this. When the amount of the component (c) is less than 0.001 part by mass, the effect of suppressing a decrease in the molecular weight of the polycarbonate may be small. If the amount exceeds 5 parts by mass, the feed may become unstable due to slipping on the screw during kneading of the polycarbonate resin composition. Further, there is a concern that mechanical strength such as strength and rigidity may be reduced.

In the resin composition of the raw material of the present invention, various additives such as an antioxidant, a lightness improver, a lubricant (release agent) may be optionally added as a component (d) as long as the object of the present invention is not impaired. Mold agent), a flame retardant, an anti-drip agent, and other inorganic fillers. The raw material resin composition of the present invention can be prepared by blending (a) component, (b) component, (c) component and various additives and kneading them. As the compounding and kneading method, a method applied to a usual resin composition can be applied as it is, and a ribbon blender, a Henschel mixer, a Banbury mixer, a drum tumbler, a single screw or a multi-screw extruder having two or more screws, a co-kneader and the like can be used. The method used is preferred. The kneading temperature is not particularly limited, but is usually suitably selected from the range of 240 to 340 ° C.

By molding the resin composition thus obtained into a flat plate or a curved plate using a usual molding method, for example, an injection molding method or a compression molding method, the light reflector of the present invention is obtained. can get. In the present invention, the surface of the injection-molding or compression-molding mold (corresponding to the reflection surface of the light reflector) is made of glass beads having an average particle size of 40 to 200 μm.
It is necessary to polish (plast treatment) with alumina or a mixture thereof. By using the polished mold, a light reflector satisfying the following expression (1), preferably the following expression (2) can be obtained. Regarding the glossiness of the surface of the light reflector, glossiness (85 °) / glossiness (20 °)> 2 (1) glossiness (85 °) / glossiness (20 °)> 5 (5) 2) The light reflector manufactured in this way can obtain a uniform luminance without deteriorating the luminance.

This light reflector is preferably used for a reflector or a reflection frame for an illumination device or a liquid crystal display backlight, for example, and is particularly suitable for a liquid crystal display backlight.

[0036]

Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples. The types and amounts of the materials used in Examples and Comparative Examples are as follows. (A) Polycarbonate (PC resin) Toughlon FN1700A [trade name, manufactured by Idemitsu Petrochemical Co., Ltd.
Bisphenol A type polycarbonate, viscosity average molecular weight 17,000] (100 parts by mass) (b) Titanium oxide powder PF726 (trade name, manufactured by Ishihara Sangyo Co., Ltd.) (18 parts by mass) (c) Organosiloxane methoxy-modified silicone BY16-160 (Product name, manufactured by Dow Corning Toray Silicone Co., Ltd.) (0.5 parts by mass)

(D) Other additives (d-1) Flame retardant Adekastab PFR (trade name, manufactured by Asahi Denka Kogyo KK, phenyl resorcin polyphosphate, phosphorus content 10.8)
% By mass) (2.4 parts by mass) (d-2) Brightness enhancer Hostalx KS-N (trade name, manufactured by Hoechst), 4
-(Benzoxazol-2-yl) -4 '-(5-methylbenzoxazol-2-yl) stilbene (0.0
(1 part by mass) (d-3) Anti-drip agent CD076 (trade name, manufactured by Asahi ICI Fluoropolymer Co., Ltd.)
(0.36 parts by mass) (d-4) Antioxidant triphenylphosphine (0.12 parts by mass)

The performance of the light reflector was evaluated according to the following procedure. (1) JIS K using a test piece with a gloss of 30 × 30 × 3 mm
It was measured according to 7105. (%) Apparatus: Optical unit for gloss measurement VGS (manufactured by Nippon Denshoku Industries Co., Ltd.) Measuring unit: SZ Sigma 90 (manufactured by Nippon Denshoku Industries Co., Ltd.) Lamp: 5V-1.25A (2) Luminance, uniformity of luminance Box case (148m) made of black acrylic plate (2mm thick)
m × 104 mm × 30 mm), and set the crimped plate (148 mm × 104 mm × 3 mm) on the bottom surface,
Cold cathode tubes (HMBS26) at a height of 4 mm from the plate surface
E, manufactured by Harrison Electric Co., Ltd.). This is a milky acrylic plate (Acrylite L432, manufactured by Mitsubishi Rayon Co., Ltd.
2 mm), and the luminance unevenness was visually determined. The result of the judgment is shown below. ：: excellent ×: inferior Also, the luminance was measured at the center using LS-110 manufactured by Minolta.

Examples 1 to 3 and Comparative Example 1 Each component of the kind and amount shown above was subjected to a 50 mmφ single screw extruder at a cylinder temperature of 280 ° C. and a screw rotation speed of 1
The mixture was melt-kneaded at 00 rpm, extruded and pelletized to prepare a resin composition. After drying the obtained pellets at 120 ° C. for 5 hours, a flat surface (S55C mirror surface # 1000)
Was subjected to injection molding using a mold subjected to plast treatment with an inorganic material shown in Table 1 to prepare a test piece for measuring physical properties. Table 2 shows the performance evaluation results of the test pieces.

[0040]

[Table 1]

[0041]

[Table 2]

[0042]

The light reflector of the present invention can obtain a uniform brightness without deteriorating the brightness, and is particularly useful as a reflector for a liquid crystal display backlight or a reflector frame.

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) C08L 83:06) C08L 83:06)

Claims (6)

[Claims] 1. A light reflector obtained by molding a polycarbonate resin composition containing (a) a polycarbonate resin, (b) a titanium oxide powder, and (c) an organosiloxane, and a gloss of the surface of the light reflector. A light reflector characterized by satisfying the following expression (1): glossiness (85 °) / glossiness (20 °)> 2 (1). 2. The method according to claim 1, wherein the polycarbonate resin composition comprises:
Component (b) 0.01 to 30 parts by mass per 100 parts by mass of component
The light reflector according to claim 1, wherein the light reflector is obtained by mixing 0.001 to 5 parts by mass of the component (c) with the component (c). 3. The glossiness of the surface of the light reflector satisfies the following expression (2): glossiness (85 °) / glossiness (20 °)> 5 (2). Or the light reflector according to 2. 4. The light reflector according to claim 1, wherein the organosiloxane (c) is a reactive group-containing organosiloxane. 5. The light reflector according to claim 4, wherein the reactive group is an alkoxy group, a hydroxyl group or hydrogen. 6. The light reflector according to claim 1, wherein the light reflector is a reflector for a liquid crystal display backlight or a reflection frame.