JP4837981B2 - Thermoplastic resin composition having excellent light diffusibility and light diffusing plate comprising the same - Google Patents

Description

  The present invention provides light diffusibility and brightness by blending a transparent thermoplastic resin with a composition comprising polycaprolactone and a light diffusing agent with a cyclic phosphite antioxidant, and optionally with a fluorescent whitening agent. The present invention relates to an improved light diffusing resin composition and a light diffusing plate comprising the same. Specifically, for members that cover the light source, for example, light diffusing plates of direct-type backlight units and edge light type units of liquid crystal televisions, glove boxes of lighting fixtures, switches of various devices, and general applications that require light diffusibility A thermoplastic resin composition excellent in light diffusibility and a light diffusing plate formed by molding the same are provided.

  Transparent thermoplastic resins are widely used in the fields of electricity, electronics, OA, automobiles, etc. because of their light transmission properties. In each field, resins that satisfy the required performance are selected and used separately. ing. In particular, in applications such as liquid crystal television direct type and edge light type units, lighting fixture covers, and switches of various devices, if a transparent thermoplastic resin is used, the light source can be seen through because it transmits light, There is a demand for a material imparted with light diffusibility without recognizing the shape of the light source (lamp) behind the resin molded product and without impairing the luminance of the light source as much as possible.

For the purpose of imparting light diffusibility to a transparent thermoplastic resin, in the prior art, there is a method in which a polymer phase or inorganic particle having a different refractive index is blended as a dispersed phase with a thermoplastic resin that forms a continuous phase. It has been adopted. In addition, a method for expressing desired light diffusibility by adjusting the range of the difference in refractive index between the dispersed phase and the continuous phase and the size of the particles in the dispersed phase has been proposed.
JP-A-60-184559 Japanese Patent Laid-Open No. 3-143950

  However, there is a demand for imparting a high level of light diffusibility and brightness over the prior art, and various improvements have been studied in terms of the composition, refractive index, particle shape, particle diameter, etc. of the light diffusing agent. However, the optical performance to be expressed is determined by the light diffusing agent to be blended, and it is difficult to achieve the optical performance required by the modification of the light diffusing agent.

  As a result of intensive studies in view of such problems, the present inventors have found that a composition comprising a transparent thermoplastic resin and polycaprolactone and a light diffusing agent is added to a cyclic phosphite-based antioxidant, and if desired, a fluorescent enhancement agent. By blending a whitening agent, the present inventors have found a thermoplastic resin composition capable of suppressing discoloration during molding and obtaining a light diffusing plate having higher brightness, and completed the present invention.

That is, the present invention relates to a light diffusing agent (C) (crosslinked) with respect to 100 parts by weight of a resin component consisting of 85 to 99.9% by weight of a polycarbonate resin (A) and 0.1 to 15% by weight of a polycaprolactone (B). 0.1 to 10 parts by weight (excluding a light diffusing agent comprising (meth) acrylic polymer particles), 2,4,8,10-tetra-t-butyl-6-as a cyclic phosphite antioxidant [3- (3-Methyl-4hydroxy-5-t-butylphenyl) propoxy] dibenzo [d, f] [1,3,2] dioxaphosphine (D) 0.01-1 part by weight and fluorescence The present invention provides a thermoplastic resin composition excellent in light diffusibility, characterized by comprising 0 to 0.1 parts by weight of a whitening agent (E), and a light diffusing plate formed by molding the same.

  The light diffusing plate obtained by molding the thermoplastic resin composition excellent in light diffusibility of the present invention is used in all applications that require light diffusivity without causing yellowing of the hue of the thermoplastic resin and poor appearance. It is suitably used and has optical performance with less yolk and high brightness.

The polycarbonate resin (A) used in the present invention is a phosgene method in which various dihydroxydiaryl compounds and phosgene are reacted or a transesterification method obtained by reacting a dihydroxydiaryl compound and a carbonate such as diphenyl carbonate. A typical example is a polycarbonate resin produced from 2,2-bis (4-hydroxyphenyl) propane (bisphenol A).

  Examples of the dihydroxydiaryl compound include bisphenol 4-, bis (4-hydroxyphenyl) methane, 1,1-bis (4-hydroxyphenyl) ethane, 2,2-bis (4-hydroxyphenyl) butane, 2, 2-bis (4-hydroxyphenyl) octane, bis (4-hydroxyphenyl) phenylmethane, 2,2-bis (4-hydroxyphenyl-3-methylphenyl) propane, 1,1-bis (4-hydroxy-3) -Tert-butylphenyl) propane, 2,2-bis (4-hydroxy-3-bromophenyl) propane, 2,2-bis (4-hydroxy-3,5-dibromophenyl) propane, 2,2-bis ( Bis (hydroxyaryl) alkanes such as 4-hydroxy-3,5-dichlorophenyl) propane, 1,1- (4-hydroxyphenyl) cyclopentane, bis (hydroxyaryl) cycloalkanes such as 1,1-bis (4-hydroxyphenyl) cyclohexane, 4,4'-dihydroxydiphenyl ether, 4,4'-dihydroxy-3 Dihydroxy diaryl ethers such as 3,3'-dimethyldiphenyl ether, dihydroxy diaryl sulfides such as 4,4'-dihydroxydiphenyl sulfide, 4,4'-dihydroxydiphenyl sulfoxide, 4,4'-dihydroxy-3,3 ' Dihydroxy diaryl sulfoxides such as dimethyldiphenyl sulfoxide, dihydroxy diary such as 4,4'-dihydroxydiphenyl sulfone, 4,4'-dihydroxy-3,3'-dimethyldiphenyl sulfone Sulfone, and the like. These are used individually or in mixture of 2 or more types. In addition to these, piperazine, dipiperidyl hydroquinone, resorcin, 4,4'-dihydroxydiphenyl, and the like may be mixed and used.

  Furthermore, the above dihydroxyaryl compound and a trivalent or higher phenol compound as shown below may be used in combination. Trihydric or higher phenols include phloroglucin, 4,6-dimethyl-2,4,6-tri- (4-hydroxyphenyl) -heptene, 2,4,6-dimethyl-2,4,6-tri- (4 -Hydroxyphenyl) -heptane, 1,3,5-tri- (4-hydroxyphenyl) -benzol, 1,1,1-tri- (4-hydroxyphenyl) -ethane and 2,2-bis- [4 4- (4,4'-dihydroxydiphenyl) -cyclohexyl] -propane and the like.

The viscosity average molecular weight of the polycarbonate resin (A) is usually 10,000 to 100,000, preferably 15,000 to 35,000, and more preferably 17,000 to 28,000. In producing such a polycarbonate resin (A) , a molecular weight regulator, a catalyst and the like can be used as necessary.

  The polycaprolactone (B) used in the present invention is a polymer produced by ring-opening polymerization of ε-caprolactone in the presence of a catalyst, and in particular, a homopolymer of 2-oxepanone is preferably used. The polymer is easily available as a commercial product, and a tone polymer manufactured by Dow Chemical Company, CAPA manufactured by Solvay Company, and the like are used. The viscosity average molecular weight of the polycaprolactone (B) is preferably 10,000 to 100,000, more preferably 40,000 to 90,000.

  In addition, polycaprolactone (B) includes a modified polycaprolactone in which ε-caprolactone is modified by ring-opening polymerization in the presence of 1,4-butanediol or the like, or whose molecular terminal is replaced with an ether or ester group. Is also included.

The composition ratio of the polycaprolactone (B) is 0.1 to 15% by weight based on the total amount of the resin components composed of the polycarbonate resin (A) and the polycaprolactone (B). When the composition ratio is less than 0.1% by weight, the light diffusion effect cannot be obtained and sufficient luminance cannot be obtained, which is not preferable. On the other hand, if it exceeds 15% by weight, an extreme decrease in heat resistance occurs, and the pellets are fixed in the pre-drying step before the molding process, and blocking is not preferable. A more preferable composition ratio is 0.3 to 10% by weight.

The light diffusing agent (C) used in the present invention is not particularly limited in terms of chemical composition such as polymer and inorganic, but the polycarbonate resin (A) and / or polycaprolactone (which is a resin component of the present invention) When the light diffusing agent (C) is added to B) and dispersed by a known method such as melt mixing using an extruder, it is necessary that the light diffusing agent (C) is not compatible with the matrix phase or is present as particles that are hardly compatible. is there.

  Specific examples of the light diffusing agent (C) include calcium carbonate, silica, silicone, zinc sulfide, zinc oxide, titanium oxide, titanium phosphate, magnesium titanate, magnesium titanate, mica, glass filler, barium sulfate, clay, Inorganic diffusing agents such as talc, silicone rubber elastic, polymethylsilsesoxane, acrylic, styrene, polyester, polyolefin, urethane, nylon, methacrylate-styrene, fluorine, norbornene, etc. And organic diffusing agents.

  Furthermore, the particle size of the light diffusing agent (C) is not particularly limited as long as the desired light diffusibility can be obtained by adding the diffusing agent, but the average particle size is about 1 to 30 μm. Can be suitably used. If the thickness is less than 1 μm, only light is transmitted, and it may be difficult to obtain a light diffusion effect. On the other hand, if it exceeds 30 μm, a sufficient light diffusion effect cannot be obtained and visibility may be inferior. Moreover, there is no restriction | limiting in particular as particle size distribution, However, It is about 0.1-100 micrometers, Furthermore, it can use more suitably in the range of 1.5-25 micrometers. Further, two or more kinds of light diffusing agents having different average particle sizes, particle size distributions, and types may be used in combination, and the particle size distribution is not uniform, and those having two or more particle size distributions are used alone or It can also be used in combination.

The compounding amount of the light diffusing agent (C) is 0.1 to 10 parts by weight per 100 parts by weight of the resin component composed of the polycarbonate resin (A) and the polycaprolactone (B). If the blending amount is less than 0.1 parts by weight, it is difficult to obtain a sufficient light diffusion effect, which is not preferable. On the other hand, if the amount exceeds 10 parts by weight, the light transmission property is impaired, and sufficient light diffusion performance cannot be obtained. More preferably, it is the range of 0.2-6 weight part.

  Examples of the cyclic phosphite antioxidant (D) used in the present invention include those produced by reacting phenols or bisphenols, phosphorus trihalide and an amine compound. As a reaction method, a two-step reaction method is generally employed in which phenols or bisphenols and phosphorus trihalide are first reacted to form an intermediate, and then an amine compound is reacted. The reaction is usually performed in an organic solvent in an environment of 0 to 200 ° C.

As the cyclic phosphite antioxidant (D) , 2,4,8,10-tetra-t-butyl-6- [3- (3-methyl-4hydroxy-5-t-butylphenyl) propoxy Dibenzo [d, f] [1,3,2] dioxaphosphine is suitable, and is available as a commercially available product, and Sumitomo GP manufactured by Sumitomo Chemical Co., Ltd. may be mentioned.

The amount of the cyclic phosphite antioxidant (D) is 0.01 to 1 part by weight per 100 parts by weight of the resin component comprising the polycarbonate resin (A) and the polycaprolactone (B). If the blending amount is less than 0.01 parts by weight, the luminance is greatly lowered due to the heat history, and if it exceeds 1 part by weight, the deterioration of the resin is promoted, which is not preferable.

Furthermore, in the present invention, in order to make the color tone vivid, the fluorescent whitening agent (E) is added up to 0.1 part by weight per 100 parts by weight of the resin component composed of the polycarbonate resin (A) and the polycaprolactone (B). Also good. If the added amount exceeds 0.1 parts by weight, the thermal stability is deteriorated, which is not preferable. More preferably, it is up to 0.03 parts by weight. Depending on the type of thermoplastic resin, it has the property of absorbing some of the blue light and has a slightly yellowish color. Therefore, a compound (fluorescent whitening agent) that emits blue or purple fluorescence corresponding to this yellow complementary color is used. When added, the fluorescence cancels the yellowish color and a vivid color tone can be obtained. A fluorescent whitening agent absorbs energy in the ultraviolet region and emits a wavelength range from blue to violet in the visible region. By using this in combination, a brighter color tone can be achieved while maintaining light diffusion performance. Obtainable.

  In the thermoplastic resin composition excellent in light diffusibility of the present invention, various known additives, polymers, and the like can be added as necessary depending on the performance required in addition to the light diffusibility. For example, in order to suppress discoloration of resin molded products when exposed to light for a long period of time, a hindered amine light-resistant stabilizer, a benzotriazole-based, benzophenone-based, triazine-based, and malonate-based UV absorber and a combination thereof are used. May be added.

When flame retardancy is required, various known flame retardants, for example, brominated flame retardants such as tetrabromobisphenol A oligomers, monophosphate esters such as triphenyl phosphate and tricresyl phosphate, bisphenol A diesters, etc. In order to further improve the flame retardancy, phosphorous flame retardants such as phosphate-type condensed phosphates such as phosphate, resorcin diphosphate, tetraxylenyl resorcin diphosphate, ammonium polyphosphate and red phosphorus, various silicone flame retardants And metal salts of aromatic sulfonic acid and perfluoroalkanesulfonic acid, preferably 4-methyl-N- (4-methylphenyl) sulfonyl-benzenesulfonamide potassium salt, diphenylsulfone- 3- potassium sulfonate, Potassium phenyl sulfonic -3-3'- disulfonic acid, sodium para-toluene sulfonic acid, also organic metal salts such as potassium perfluorobutane sulfonate and the like may be added. Among these flame retardants, phosphorus-based flame retardants can be suitably used because they can improve not only flame retardancy but also fluidity.

  In the thermoplastic resin composition excellent in light diffusibility of the present invention, known additives other than those described above, such as phenol-based or phosphorus-based heat stabilizer [2,6-di-t-butyl-4-methylphenol, 2- (1-methylcyclohexyl) -4,6-dimethylphenol, 4,4'-thiobis- (6-tert-butyl-3-methylphenol), 2,2-methylenebis- (4-ethyl-6-t) -Methylphenol), n-octadecyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate, tris (2,4-di-t-butylphenyl) phosphite, 4,4'- Biphenylene diphosphinic acid tetrakis- (2,4-di-t-butylphenyl), etc.], lubricant [paraffin wax, n-butyl stearate, synthetic beeswax, natural beeswax, glycerin monoes , Montanic acid wax, polyethylene wax, pentaerythritol tetrastearate, etc.], colorant [eg titanium oxide, carbon black, dye], filler [calcium carbonate, clay, silica, glass fiber, glass sphere, glass flake, carbon Fiber, talc, mica, various whiskers, etc.], fluidity improver, spreading agent [epoxidized soybean oil, liquid paraffin, etc.], and other thermoplastic resins and various impact modifiers (polybutadiene, polyacrylic acid) A rubber-reinforced resin obtained by graft polymerization of a compound such as methacrylic acid ester, styrene, acrylonitrile, etc. to a rubber such as an ester or ethylene / propylene rubber may be added as necessary.

There is no restriction | limiting in the embodiment and order in this invention. For example, polycarbonate resin (A) polycaprolactone (B), light diffusing agent (C), cyclic phosphite antioxidant (D) and optionally fluorescent whitening agent (E) are weighed in arbitrary amounts. Then, after mixing together by a tumbler, riboblender, high-speed mixer, etc., the mixture is melt-kneaded using a normal single screw or twin screw extruder and pelletized, or some or all of each component is separated separately And a method of melt-mixing them into a extruder from a plurality of feeders, and further, polycaprolactone (B) and / or light diffusing agent (C) and / or cyclic with respect to the polycarbonate resin (A). A phosphite antioxidant (D) and / or a fluorescent brightening agent (E) are blended at a high concentration, once melt mixed and pelletized, After, the master batch and a polycarbonate resin (A), the can also be mixed with desired ratio. Then, when these components are melt-mixed, arbitrary conditions such as the position at which the extruder is introduced, the extrusion temperature, the screw rotation speed, the supply amount, and the like can be selected and pelletized. Furthermore, the masterbatch and the polycarbonate resin (A) can be directly mixed into an injection molding apparatus or a sheet extruder apparatus after dry mixing at a desired ratio to obtain a molded product.

  EXAMPLES Hereinafter, although an Example demonstrates this invention, this invention is not limited to these Examples. Unless otherwise specified, “%” and “part” in the examples are based on weight standards.

The raw materials used are as follows.
Polycaprolactone:
CAPA6800 manufactured by Solvay
(Viscosity average molecular weight: 80000, hereinafter abbreviated as PCL-1)
CAPA6500C made by Solvay
(Viscosity average molecular weight: 50000, hereinafter abbreviated as PCL-2)
Tone polymer P-787 manufactured by Dow Chemical Company
(Viscosity average molecular weight: 80000, hereinafter abbreviated as PCL-3)
Polycarbonate resin:
Sumitomo Dow Caliber 200-30
(Viscosity average molecular weight: 17200, hereinafter abbreviated as PC-1)
Caliber 200-3 manufactured by Sumitomo Dow
(Viscosity average molecular weight: 28000, hereinafter abbreviated as PC-2)
Light diffusing agent:
MSP-S020 made by Nikko Rica
(Polymethylsilsesoxane-based diffusing agent, hereinafter abbreviated as LD-1)
GM-0449S manufactured by Gantz Kasei
(Acrylic diffusing agent, hereinafter abbreviated as LD-2)
Antioxidant:
Sumitomo Chemical Co., Ltd.
(Cyclic phosphite-based antioxidant, hereinafter abbreviated as AO-1)
Sand stub P-EPQ made by Clariant Japan
(Phosphorus antioxidant hereinafter abbreviated as AO-2)
Optical brightener:
HOSTARUX KSN made by Clariant Japan

Various evaluation items and the measurement method in the present invention will be described.
1. Evaluation of moldability When preparing flat plate test pieces using an injection molding machine, in the pellets used for molding, the state of the pellets after preliminary drying is visually confirmed, and molding is difficult with the pellets fixed to each other. Some were rejected (x), and those that could be molded without problems were marked as acceptable (O).

2. Measurement of shielding factor The shielding factor in the present invention represents the amount of light that does not transmit in the visible light wavelength region, 380 to 720 nm, is calculated by the following general formula, and is an ultraviolet-visible spectrophotometer (V-manufactured by JASCO Corporation). 570).
Shielding rate (%) = {1− (transmitted light amount / 34,000)} × 100
When the shielding rate calculated by the measurement method was in the range of 60 to 85%, it was determined to be acceptable (◯), and other cases were determined to be unacceptable (x). Outside this range, the lamp-to-lamp brightness decreases, and a sufficient brightness cannot be obtained.

3. Measurement of Luminance Two cold cathode tubes were placed on the back side of a flat test piece (90 mm × 50 mm × 2 mm thickness), and the luminance on the surface of the test piece in the vertical direction between the lamps was measured. The luminance means the ratio of the luminous intensity directed in a certain direction per unit area in a plane perpendicular to the direction, and generally represents the degree of brightness of the light emitting surface [unit: (cd / m ² ). ].
The criteria for evaluation of the initial injection molded specimens, passes the test measurements of the ramp between the luminance is 2500 cd / ^{m 2} or more (○), was judged as unsatisfactory those which are less than 2500cd / ^{m 2} (×) .

4. Evaluation of thermal stability When preparing a flat plate test piece using an injection molding machine, the resin composition was allowed to stay in the cylinder for 15 minutes, and then normal injection molding was carried out to obtain the third shot of the flat plate test piece. Optical measurement was performed to evaluate thermal stability.
As a standard for evaluation of the test piece after staying, the same luminance measurement as that of the initial injection-molded test piece is performed, and the amount of decrease is less than 50 Cd / m 2 is acceptable (◯), and is 50 Cd / m 2 or more. Things were rejected (x).

5). Measurement of bluishness b * was measured with a spectrophotometer (CMS-35SP manufactured by Murakami Color Research Co., Ltd.) using a flat plate test piece prepared by injection molding. b * represents the degree from yellow to blue, and the smaller b *, the less yellow and the stronger blue.

6). Comprehensive judgment In the evaluation of the shielding rate, luminance, and moldability, a sample satisfying all of the criteria was accepted (◯), and a sample not satisfying it was rejected (x).

(Example 1 to Example 6)
According to the blending ratio shown in Table 1, polycaprolactone (PCL-1), polycarbonate resin (PC-1), light diffusing agent (LD-1), and cyclic phosphate ester antioxidant (AO-1) are superfloaters ( And dry-mixed. Subsequently, melt kneading was performed at a temperature of 250 to 290 ° C. by a twin screw extruder (KTX-37 manufactured by Kobe Steel) (shaft diameter = 37 mmφ, L / D = 30). Using an injection molding machine (J100E2P manufactured by Nippon Steel), a flat plate test piece having a length of 90 mm, a width of 50 mm, and a thickness of 2 mm was created under the conditions of a cylinder set temperature of 300 ° C. The same injection molding machine was used for the thermal stability test. Was used for 15 minutes in a cylinder under a temperature condition of 320 ° C., and evaluation was performed using a test piece for the third shot under normal injection molding conditions.
As for formability, the pellets did not stick to each other after preliminary drying, and both were good. Regarding the optical performance, the shielding rate and the luminance between the lamps were good, and the decrease in luminance after residence was very small. The results are shown in Table 1.

(Example 7 to Example 8)
Except changing the kind of polycaprolactone to PCL-2 or PCL-3, the same operation as Example 2 was performed and the flat test piece was created. The pellets did not stick to each other after the preliminary drying, and the moldability was good. Regarding the optical performance, the shielding rate and the luminance between the lamps were good, and the luminance after dwelling was also good. The results are shown in Table 2.

Example 9
Except changing the kind of polycarbonate resin to PC-2, operation similar to Example 2 was performed and the flat test piece was created. The pellets did not stick to each other after the preliminary drying, and the moldability was good. Regarding the optical performance, the shielding rate and the luminance between the lamps were good, and the luminance after dwelling was also good. The results are shown in Table 2.

(Example 10 to Example 11)
The same operation as in Example 2 was performed except that the type of the light diffusing agent was changed to LD-1 and the addition amount thereof was changed to 1.5 parts in Example 10 and 6 parts in Example 11. A test piece was prepared. The pellets did not stick to each other after the preliminary drying, and the moldability was good. Regarding the optical performance, the shielding rate and the luminance between the lamps were good, and the luminance after dwelling was also good. The results are shown in Table 2.

(Example 12)
A plate test piece was prepared in the same manner as in Example 2 except that 0.01 part of the optical brightener was added to Example 2. The pellets did not stick to each other after the preliminary drying, and the moldability was good. The shielding rate and inter-lamp brightness were also good results. In addition, the color tone showed a decrease in b * in comparison with Example 2, and also exhibited a vivid blue tint visually. The results are shown in Table 3.

(Comparative Examples 1 to 3)
The compounding amount of the light diffusing agent (LD-1) is fixed at 0.3 part, and in Comparative Example 1, 100% of the polycarbonate resin (PC-1) is added without adding polycaprolactone (PCL-1). Then, the same procedure as in Example 2 was performed, except that the composition ratio of polycaprolactone (PCL-1) was changed to 0.05%, and in Comparative Example 3, the composition ratio of polycaprolactone (PCL-1) was changed to 20%. A flat plate test piece was prepared. The evaluation results are shown in Table 4.
In Comparative Example 1, no polycaprolactone was blended, and in Comparative Example 2, the composition ratio of polycaprolactone was less than the constituent requirements of the present invention, and both had inferior lamp brightness.
Comparative Example 3 was a case where the composition ratio of polycaprolactone was larger than the constituent requirements of the present invention, and the luminance between the lamps was good, but the moldability was inferior and it was rejected.

(Comparative Example 4 to Comparative Example 5)
The composition ratio of polycaprolactone (PCL-1) was fixed at 3%. In Comparative Example 4, LD-1 was used as 0.05 part as a light diffusing agent, and in Comparative Example 5, LD-2 was used as 15 parts as a light diffusing agent. Except changing, the same operation as Example 2 was performed and the flat test piece was created. The evaluation results are shown in Table 4.
Comparative Example 4 is an example where the blending amount of the light diffusing agent is less than the constituent requirement of the present invention, and Comparative Example 5 is an example where the blending amount of the light diffusing agent is greater than the constituent requirement of the present invention. It was inferior in the shielding rate and the brightness between lamps.

(Comparative Examples 6-11)
About Comparative Examples 6-9, although it is the same composition as Examples 1-4, it changed into the composition which has not added cyclic phosphite antioxidant (AO-1), and performed the same operation as Example 2. A flat plate test piece was prepared. The evaluation results are shown in Table 5.
In Comparative Examples 6 to 9, since the cyclic phosphite-based antioxidant as a constituent element of the present invention was not added, the decrease in luminance after staying exceeded the specified range and failed.
Comparative Examples 10 to 11 are the same compositions as in Examples 5 to 6, except that the cyclic phosphite antioxidant was changed to a general phosphorus antioxidant (AO-2). The same operation was performed to prepare a flat plate test piece. The evaluation results are shown in Table 2.
Since Comparative Examples 10-11 differed in the kind of antioxidant of a structural requirement, the fall of the brightness | luminance after a residence exceeded a regulation range, and was disqualified.

It is a figure which shows the measuring method of the brightness | luminance between lamps of this invention.

Explanation of symbols

A: Luminance meter B: Light beam C: Light diffusion plate D: Lamp (cold cathode tube)

Claims (5)

The light diffusing agent (C) (crosslinked (meth) acrylic heavy weight) is added to 100 parts by weight of the resin component consisting of 85 to 99.9% by weight of the polycarbonate resin (A) and 0.1 to 15% by weight of the polycaprolactone (B). 0.1 to 10 parts by weight (excluding light diffusing agent composed of coalesced particles), 2,4,8,10-tetra-t-butyl-6- [3- (3- Methyl-4hydroxy-5-t-butylphenyl) propoxy] dibenzo [d, f] [1,3,2] dioxaphosphine (D) 0.01 to 1 part by weight and optical brightener (E) A thermoplastic resin composition excellent in light diffusibility, comprising 0 to 0.1 parts by weight. The thermoplastic resin composition having excellent light diffusibility according to claim 1, wherein the polycaprolactone (B) has a viscosity average molecular weight of 40,000 to 90,000. A light diffusing plate formed from the thermoplastic resin composition having excellent light diffusibility according to claim 1 or 2 . The light diffusing plate according to claim 3 , which is used for a liquid crystal display. The light diffusing plate according to claim 3 , which is used for a direct type backlight of a liquid crystal display.

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