JP2008216598A - Optical reflection plate, illuminating device and display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical reflection plate which is scarcely accompanied by lowering of a total reflection index even when exposed to light and which maintains an excellent total reflection index extending over a long period of time. <P>SOLUTION: The optical reflection plate is characterized in that it is formed by molding a thermoplastic resin composition containing 100 pts.wt. of a thermoplastic resin, 10-100 pts.wt. of titanium oxide, 0.01-0.8 pts.wt. of a primary anti-oxidizing agent, 0.01-0.8 pts.wt. of a secondary anti-oxidizing agent, 0.01-0.8 pts.wt. of an ultraviolet absorbing agent, and 0.01-0.8 pts.wt. of a hindered amine light stabilizer. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a light reflection plate that has excellent light reflection performance over a long period of time with little reduction in total light reflectance even when irradiated with light, and an illumination device and display device using the light reflection plate.

  In recent years, liquid crystal display devices have been used for various purposes as display devices. This liquid crystal display device is provided with a backlight unit on the back surface of the liquid crystal cell. The backlight unit includes a cold cathode tube, a lamp reflector, a light guide plate, a diffusion plate provided on the front side of the light guide plate, and The light reflecting plate is disposed on the rear surface side of the light guide plate, and the light reflecting plate plays a role of reflecting light leaking to the rear surface side of the light guide plate toward the liquid crystal cell side. Such a backlight system is called a sidelight system. Also, for large screens such as liquid crystal televisions, the sidelight method cannot be expected to increase the screen brightness, and therefore the direct light method is adopted. In this system, cold cathode tubes are arranged in parallel to each other on the back side of the liquid crystal screen, and a light reflecting plate is disposed on the back side of the cold cathode tubes to increase the brightness.

  As said light reflecting plate, in patent document 1, in the light reflecting plate formed by shape | molding the molding material containing a polypropylene resin and an inorganic filler, titanium oxide is 4-15 mass% with respect to the molding material whole quantity as an inorganic filler. A light reflecting plate containing 25 to 40% by mass of an inorganic filler other than titanium oxide with respect to the total amount of the molding material is proposed, and the total light reflectance is increased by increasing the amount of titanium oxide. It can be improved effectively.

  However, titanium oxide is activated by receiving light to generate radicals, oxidatively decompose and yellow the organic matter in contact with titanium oxide, and reduce the total light reflectance of the light reflector. There was a problem.

Further, it is known that when titanium oxide is irradiated with ultraviolet rays, it undergoes a photochemical change in the crystal and oxygen defects increase, producing purple-blue Ti ⁺³ and turning dark gray. This photochemical change is reversible and has the property of gradually restoring from dark gray to white when left in a dark place.

  Moreover, in order to express the high light total reflectance required as a light reflecting plate using titanium oxide, it is necessary to contain titanium oxide at a high concentration of 10% by weight or more in the light reflecting plate. The higher the is, the more remarkable the two reactions by titanium oxide described above.

  For this reason, when the light reflecting plate containing titanium oxide is exposed to light, the initial total light reflectance of the light reflecting plate is reduced in a short time, and the luminance of the display screen of the liquid crystal display device is lowered. It had the problem of inviting.

JP 2006-309108 A

  The present invention provides a light reflecting plate that hardly deteriorates the total light reflectance even when exposed to light and maintains an excellent total light reflectance over a long period of time, and uses this light reflecting plate. Provided lighting device and display device.

  The light reflecting plate of the present invention comprises 100 parts by weight of a thermoplastic resin, 10 to 100 parts by weight of titanium oxide, 0.01 to 0.8 part by weight of a primary antioxidant, and 0.01 to 0.8 part by weight of a secondary antioxidant. Part, a thermoplastic resin composition containing 0.01 to 0.8 part by weight of an ultraviolet absorber and 0.01 to 0.8 part by weight of a hindered amine light stabilizer.

  The thermoplastic resin is not particularly limited, and examples thereof include polyethylene resins, polyolefin resins such as polypropylene resins, polyester resins, acrylic resins such as polymethyl acrylate, polyvinyl chloride resins, and polychlorinated resins. Examples thereof include diene resins such as vinylidene resins, fluorine resins, polyether resins, polyamide resins, polyurethane resins, polybutadienes, polyolefin resins are preferable, and polypropylene resins are more preferable. In addition, a thermoplastic resin may be used independently or 2 or more types may be used together.

  Examples of the polyethylene resin include low density polyethylene, linear low density polyethylene, high density polyethylene, and medium density polyethylene.

  In addition, examples of the polypropylene resin include homopolypropylene, ethylene-propylene copolymer, propylene-α-olefin copolymer, and the like. Homopolypropylene is preferred because it does not cloud the glass plate constituting the glass. Further, when the light reflecting plate is foamed, the polypropylene resin is preferably a high melt tension polypropylene resin disclosed in Japanese Patent No. 2521388 or Japanese Patent Application Laid-Open No. 2001-226510. .

  In addition, the ethylene-propylene copolymer and the propylene-α-olefin copolymer may be either a random copolymer or a block copolymer. The content of the α-olefin component in the propylene-α-olefin copolymer is preferably 0.5 to 30% by weight, and more preferably 1 to 10% by weight.

  Examples of the α-olefin include α-olefins having 4 to 10 carbon atoms, such as 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-heptene, 1-octene and the like. Is mentioned.

  The titanium oxide includes a rutile type, anatase type and ilmenite type, but a rutile type is preferred. Titanium oxide, when its photocatalytic action is strong, deteriorates the thermoplastic resin and causes a decrease in the total light reflectivity of the light reflecting plate. Therefore, it is preferable to perform surface treatment.

  Although it does not specifically limit as the surface treatment method of the said titanium oxide, The method etc. which coat | cover with hydrous oxides, such as aluminum, silicon, titanium, zirconium, tin, etc. are mentioned.

  And, if the content of titanium oxide in the thermoplastic resin composition is small, the total light reflectivity of the light reflecting plate is lowered, but at most, the light ray of the light reflecting plate that is commensurate with the blending amount of titanium oxide. Not only is the total reflectance improved, but also the lightness of the light reflector is impaired, so the amount is limited to 10 to 100 parts by weight with respect to 100 parts by weight of the thermoplastic resin, preferably 20 to 80 parts by weight, 30 -65 weight part is more preferable.

  The primary antioxidant used in the light reflecting plate of the present invention is a stabilizer that traps radicals generated by heat or light and stops the radical reaction. As such primary antioxidant, A phenolic antioxidant is preferred because it has a high effect of suppressing a decrease in the total light reflectance of the plate.

  Examples of the phenolic antioxidant include 2,6-di-t-butyl-4-methylphenol and n-octadecyl-3- (3 ′, 5′-di-t-butyl-4′-hydroxyphenyl). ) Propionate, tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionyloxymethyl] methane, tris [N- (3,5-di-t-butyl-4-hydroxybenzyl)] Isocyanurate, butylidene-1,1-bis (2-methyl-4-hydroxy-5-t-butylphenyl), triethylene glycol bis [3- (3-t-butyl-4-hydroxy-5-methylphenyl) Propionate], 3,9-bis {2- [3 (3-t-butyl-4-hydroxy-5-methylphenyl) propionyloxy] -1,1-dimethylethyl} -2,4 8,10-tetraoxaspiro [5.5] undecane and the like, may be also alone, or two or more are used alone.

  And, if the content of the primary antioxidant in the thermoplastic resin composition is small, the decrease in the total light reflectance of the light reflecting plate cannot be suppressed, while at most, the total light reflection of the light reflecting plate. Since there is no change in the effect of suppressing the decrease in rate, it is limited to 0.01 to 0.8 parts by weight, preferably 0.05 to 0.5 parts by weight, with respect to 100 parts by weight of the thermoplastic resin.

  The secondary antioxidant used in the light reflector of the present invention ionizes hydroperoxide (ROOH), which is an intermediate of auto-oxidative degradation of thermoplastic resin caused by heat and light, to prevent auto-oxidation. Therefore, phosphorus antioxidants and sulfur antioxidants are preferable, and phosphorus antioxidants are more preferable because they are highly effective in suppressing a decrease in total light reflectance of the light reflector.

  Examples of the phosphorus antioxidant include tris (nonylphenyl) phosphite, tris (2,4-di-t-butylphenyl) phosphite, distearyl pentaerythritol diphosphite, and bis (2,4-diphenyl). -T-butylphenyl) pentaerythritol phosphite, 2,2-methylenebis (4,6-di-t-butylphenyl) -4,4'-biphenylenedi-phosphonite, and the like. Two or more kinds may be used in combination.

  Examples of the sulfur-based antioxidant include dilauryl-3,3′-thio-dipropionate, dimyristyl-3,3′-thio-dipropionate, distearyl-3,3′-thio-dipropionate, and pentaerythritol tetrakis. (3-laurylthio-propionate) and the like may be mentioned, and these may be used alone or in combination of two or more.

  And, if the content of the secondary antioxidant in the thermoplastic resin composition is small, it is not possible to suppress the decrease in the total light reflectance of the light reflecting plate, while at most, the total light amount of the light reflecting plate is not. There is no change in the effect of suppressing the decrease in reflectivity, and the color of the secondary antioxidant itself causes a decrease in the total light reflectivity of the light reflecting plate. Therefore, 0.01 to 0.00% relative to 100 parts by weight of the thermoplastic resin. It is limited to 8 parts by weight, and preferably 0.05 to 0.5 parts by weight.

  Furthermore, examples of the ultraviolet absorber used in the light reflecting plate of the present invention include 2- (2′-hydroxy-5′-methylphenyl) benzotriazole and 2- [2′-hydroxy-3 ′, 5′-. Bis (α, α-dimethylbenzyl) phenyl] -benzotriazole, 2- (2′-hydroxy-3 ′, 5-di-t-butylphenyl) -benzotriazole, 2- (2′-hydroxy-3′- t-butyl-5′-methylphenyl) -5-chlorobenzotriazole, 2- (2′-hydroxy-3 ′, 5′-di-t-butylphenyl) -5-chlorobenzotriazole, 2- (2 ′ -Hydroxy-3 ', 5'-di-t-amyl) benzotriazole, 2- (2'-hydroxy-5'-t-octylphenyl) benzotriazole, 2,2'-methylenebis [4- (1,1 , 3,3- Benzotriazole ultraviolet absorbers such as tetramethylbutyl) -6- (2N-benzotriazol-2-yl) phenol], 2,4-dihydroxy-benzophenone, 2-hydroxy-4-methoxy-benzophenone, 2-hydroxy- 4-methoxybenzophenone-5-sulfonic acid, 2-hydroxy-4-n-octyl-benzophenone, 2-hydroxy-4-n-dodecyloxy-benzophenone, bis (5-benzoyl-4-hydroxy-2-methoxyphenyl) methane 2,2′-dihydroxy-4-methoxy-benzophenone, 2,2′-dihydroxy-4,4′-dimethoxybenzophenone and other benzophenone ultraviolet absorbers, phenyl salicylate, 4-t-butylphenyl salicylate, etc. Salicylate UV absorbers, Cyanoacrylate ultraviolet absorbers such as ethyl-2-cyano-3,3-diphenyl-acrylate and 2-ethylhexyl-2-cyano-3,3′-diphenyl-acrylate, 2-ethoxy-3-tert-butyl-2 Oxalic acid anilide-based UV absorbers such as' -ethyl-bisoxalic acid bisanilide, 2-ethoxy-2'-ethyl-oxalic acid bisanilide, 2,4-di-t-butylphenyl-3,5-di-t -Benzoate UV absorbers such as butyl-4-hydroxybenzoate, 2- [4,6-bis (2,4-dimethylphenyl) -1,3,5-triazin-2-yl] -5-hydroxyphenol, 2- (2,4-dihydroxyphenyl) -4,6-bis (2,4-dimethylphenyl) -1,3,5-triazine, 2,4-bis ( -Hydroxy-4-butoxyphenyl) -6- (2,4-dibutoxyphenyl) -1,3-5-triazine and other triazine-based UV absorbers and the like, and the reduction of the total light reflectance of the light reflector Benzotriazole-based ultraviolet absorbers are preferable because of effectively suppressing the above. In addition, an ultraviolet absorber may be used independently or 2 or more types may be used together.

  Further, if the content of the ultraviolet absorber in the thermoplastic resin composition is small, the decrease in the total light reflectance of the light reflecting plate cannot be suppressed, but at most, the total light reflectance of the light reflecting plate is not allowed. Since there is no change in the effect of suppressing the decrease in the amount, the amount is limited to 0.01 to 0.8 parts by weight, preferably 0.05 to 0.5 parts by weight with respect to 100 parts by weight of the thermoplastic resin.

  The hindered amine light stabilizer used in the light reflector of the present invention is not particularly limited, and examples thereof include bis (2,2,6,6-tetramethyl-4-piperidinyl) sebacate and bis (N-methyl). -2,2,6,6-tetramethyl-4-piperidinyl) sebacate, bis (1,2,2,6,6-pentamethyl-4-piperidinyl) -2- (3,5-di-t-butyl- 4-hydroxybenzyl) -2-n-butylmalonate, tetrakis (2,2,6,6-tetramethyl-4-piperidyl) -1,2,3,4-butane-tetracarboxylate, tetrakis (1, 2,2,6,6-pentamethyl-4-piperidyl) -1,2,3,4-butane-tetracarboxylate, (2,2,6,6-tetramethyl-4-piperidyl) -1,2, 3, 4 A mixture of butane-tetracarboxylate and (2,2,6,6-tetramethyl-4-tridecyl) -1,2,3,4-butane-tetracarboxylate, (1,2,2,6,6 -Pentamethyl-4-piperidyl) -1,2,3,4-butane-tetracarboxylate and (1,2,2,6,6-pentamethyl-4-tridecyl) -1,2,3,4-butane Mixture with tetracarboxylate, {2,2,6,6-tetramethyl-4-piperidyl-3,9- [2,4,8,10-tetraoxaspiro (5.5) undecane] diethyl} -1 , 2,3,4-Butane-tetracarboxylate and {2,2,6,6-tetramethyl-β, β, β ′, β′-tetramethyl-3,9- [2,4,8,10 -Tetraoxaspiro (5.5) undecane] diethyl}- , 2,3,4-butane-tetracarboxylate, {1,2,2,6,6-pentamethyl-4-piperidyl-3,9- [2,4,8,10-tetraoxaspiro ( 5.5) Undecane] diethyl} -1,2,3,4-butane-tetracarboxylate and {1,2,2,6,6-pentamethyl-β, β, β ′, β′-tetramethyl-3 , 9- [2,4,8,10-tetraoxaspiro (5.5) undecane] diethyl} -1,2,3,4-butane-tetracarboxylate, poly [6- (1,1 , 3,3-tetramethylbutyl) imino-1,3,5-triazine-2,4-diyl], [(2,2,6,6-tetramethyl-4-piperidyl) imino] hexamethylene [(2 , 2,6,6-tetramethyl-4-piperidyl) imino], 4-hydroxy A mixture of cis-2,2,6,6-tetramethyl-1-piperidineethanol and dimethyl succinate polymer, N, N ′, N ″, N ′ ″-tetrakis {4,6-bis [butyl- ( N-methyl-2,2,6,6-tetramethylpiperidin-4-yl) amino] -triazin-2-yl} -4,7-diazadecane-1,10-diamine and the like are used alone. Or 2 or more types may be used together.

  In addition, if the content of the hindered amine light stabilizer in the thermoplastic resin composition is small, a decrease in the total light reflectance of the light reflecting plate cannot be suppressed. There is no change in the effect of suppressing the decrease in the reflectance, and the hindered amine light stabilizer itself is colored to cause a decrease in the total light reflectance of the light reflecting plate. It is limited to 8 parts by weight, and preferably 0.05 to 0.5 parts by weight.

  Here, the deterioration of the thermoplastic resin is caused by the cleavage of the polymer main chain. Specifically, radicals are generated by heat, light, and the like, and the generated radicals react with oxygen to turn into peroxy radicals, drawing hydrogen from the main chain into hydroperoxides. Thereafter, hydroperoxide is decomposed by the action of heat, light, and the like, becomes an alkoxy radical, cuts the polymer main chain, and a radical is generated as the polymer main chain is cut. By repeating this reaction cycle, the polymer main chain is cleaved to lower the molecular weight, and the thermoplastic resin deteriorates. This deterioration of the thermoplastic resin causes yellowing of the thermoplastic resin, resulting in a decrease in the total light reflectance of the light reflecting plate.

Further, as described above, titanium oxide is activated by receiving light, and oxidatively decomposes and yellows organic matter in contact with titanium oxide, thereby reducing the total light reflectance of the light reflector. In addition to the above point, when ultraviolet rays are irradiated, there is a problem that a photochemical change is caused in the crystal, oxygen defects are increased, and purple-blue Ti ⁺³ is generated to change to dark gray.

  Therefore, in the light reflector of the present invention, although a clear mechanism has not been elucidated, a primary antioxidant, a secondary antioxidant, an ultraviolet absorber, and a hindered amine light stabilizer are added in a predetermined amount as described above. Thus, the yellowing caused by the deterioration of the thermoplastic resin and the photochemical change of the titanium oxide are suppressed, thereby preventing the decrease in the total light reflectance of the light reflecting plate.

  Specifically, in the light reflecting plate of the present invention, by adding an ultraviolet absorber and a hindered amine light stabilizer, yellowing due to deterioration of the thermoplastic resin is prevented by the light stabilizing effect of the thermoplastic resin. The aim is to prevent oxidative degradation of organic substances and to suppress photochemical changes due to the activation of titanium oxide.

  On the other hand, as described above, the ultraviolet absorber and the hindered amine light stabilizer have the power to suppress the oxidative decomposition of the organic matter by the titanium oxide, but the suppression power is not sufficient, and the ultraviolet absorber and the hindered amine The system light stabilizer itself may be oxidized and decomposed by titanium oxide.

  Therefore, in the light reflector of the present invention, in addition to the ultraviolet absorber and the hindered amine light stabilizer, a primary antioxidant and a secondary antioxidant are added to trap the radical reaction and ionic decomposition of the hydroperoxide. The plastic resin is light-stabilized to further prevent yellowing due to deterioration, and the oxidative decomposition of the UV absorber and the hindered amine light stabilizer by titanium oxide is prevented.

  That is, the light reflector of the present invention prevents decomposition of the UV absorber and the hindered amine light stabilizer by titanium oxide, in addition to preventing yellowing due to deterioration of the thermoplastic resin by the primary antioxidant and the secondary antioxidant. In addition, this protected UV absorber and hindered amine light stabilizer prevent oxidative degradation of organic substances by titanium oxide and suppress photochemical changes. While being surely prevented from being reduced over time, it is configured to maintain an excellent total light reflectance even over a long period of time.

  Furthermore, you may add a copper damage inhibitor (metal deactivator) to the said thermoplastic resin composition. Thus, by adding a copper damage inhibitor to the thermoplastic resin composition, the light reflection plate comes into contact with a metal such as copper, or a heavy metal ion such as copper ion acts on the light reflection plate. However, copper ions, which are deterioration promoting factors, can be captured as chelate compounds, and when the light reflector is incorporated into various liquid crystal display devices or lighting devices, the light reflector contacts with metals such as copper. Even so, it is possible to prevent the thermoplastic resin from being deteriorated and yellowing.

  Examples of the copper damage inhibitor (metal deactivator) include hydrazine compounds such as N, N-bis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionyl] hydrazine, 3 -(3,5-di-tetra-butyl-4-hydroxyphenyl) propionyl dihydride and the like.

  And, if the content of the copper damage inhibitor (metal deactivator) in the thermoplastic resin composition is small, the effect of adding the copper damage inhibitor may not be manifested. Since total light reflectance may fall, 0.1-3.0 weight part is preferable with respect to 100 weight part of thermoplastic resins.

  Further, an antistatic agent may be added to the thermoplastic resin composition. By adding the antistatic agent in this way, the light reflecting plate can be prevented from being charged, dust and dirt can be prevented from adhering to the light reflecting plate, and the total light reflectance of the light reflecting plate can be reduced. Can be prevented.

  As such an antistatic agent, for example, ionomers such as polyethylene oxide, polypropylene oxide, polyethylene glycol, polyester amide, polyether ester amide, and ethylene-methacrylic acid copolymer, and fourth polymers such as polyethylene glycol methacrylate copolymer are used. A class ammonium salt, a polymer type antistatic agent such as a block copolymer having a structure in which an olefinic block and a hydrophilic block described in JP-A-2001-278985 are bonded alternately and repeatedly, an inorganic salt, a polyhydric alcohol , Metal compounds, carbon and the like. If the content of the antistatic agent excluding the polymeric antistatic agent in the thermoplastic resin composition is small, the effect of adding the antistatic agent may not be manifested. 100% by weight of thermoplastic resin because not only an effect commensurate with the addition concentration of the anti-static agent but also a decrease in the effect of the antistatic agent, or significant bleeding out, coloring and yellowing due to light may occur. 0.1 to 5.0 parts by weight is preferable.

  Further, the content of the polymer type antistatic agent in the thermoplastic resin composition is preferably 1 to 10 parts by weight with respect to 100 parts by weight of the thermoplastic resin for the same reason as described above.

  In addition to copper damage inhibitors (metal deactivators) and antistatic agents, the thermoplastic resin composition includes dispersants such as metal stearates, quenchers, lactone processing stabilizers, fluorescent whitening. An agent, a crystal nucleating agent, or the like may be added.

  Next, the manufacturing method of the light reflecting plate of this invention is demonstrated. This light reflecting plate is obtained by molding the thermoplastic resin composition, and may be formed of either a foamed sheet or a non-foamed sheet.

  First, the case where the light reflecting plate of the present invention is formed from a foam sheet will be described. As a manufacturing method of this light reflector, a general-purpose method is adopted, for example, thermoplastic resin, titanium oxide, primary antioxidant, secondary antioxidant, ultraviolet absorber, hindered amine light stabilizer and foaming agent. Supply to an extruder and melt-knead to obtain a foamable thermoplastic resin composition, and this foamable thermoplastic resin composition is extruded and foamed from a die attached to the tip of the extruder to produce a light reflector made of a foam sheet The method of doing is mentioned. The die is not particularly limited as long as it is widely used in extrusion foaming, and examples thereof include a T die and an annular die.

  In the above manufacturing method, when a T die is used as a die, a light reflecting plate made of a foamed sheet can be manufactured by extrusion foaming from a extruder into a sheet shape, while an annular die is used as a die First, a cylindrical body is manufactured by extrusion foaming from a circular die, and after the cylindrical body is gradually expanded in diameter, supplied to a cooling mandrel and cooled, the cylindrical body is moved in the extrusion direction. A light reflecting plate made of a foamed sheet can be manufactured by continuously cutting, opening and unfolding between the inner and outer peripheral surfaces.

  The blowing agent is not particularly limited, and is an organic gas such as saturated aliphatic hydrocarbons such as propane, butane and pentane, and halogenated hydrocarbons such as tetrafluoroethane, chlorodifluoroethane and difluoroethane; carbon dioxide and nitrogen gas. Gaseous inorganic compounds such as water; liquid inorganic compounds such as water; mixtures of organic acids or salts thereof with bicarbonate, such as a mixture of sodium bicarbonate and citric acid, dinitrosopentamethylenetetramine, etc. Solid foaming agents and the like are mentioned, and it is preferable to use a mixture of an organic acid or a salt thereof and bicarbonate and an organic gas, and a mixture of sodium bicarbonate and citric acid and an organic gas are used. It is more preferable to use together.

  Next, the case where the light reflecting plate is formed from a non-foamed sheet will be described. As a manufacturing method of this light reflector, a general-purpose method is adopted. For example, a thermoplastic resin, titanium oxide, primary antioxidant, secondary antioxidant, ultraviolet absorber and hindered amine light stabilizer are used as an extruder. A method of producing a light reflecting plate made of a non-foamed sheet by feeding and melt-kneading to make a thermoplastic resin composition, and extruding the thermoplastic resin composition into a sheet form from a T die attached to the tip of an extruder is mentioned. It is done.

  Furthermore, a foamed sheet or a non-foamed sheet may be laminated and integrated on one surface of the light reflecting plate of the present invention to form a light reflecting laminated plate. As a manufacturing method of such a light reflecting laminated plate, a general-purpose method is adopted. For example, (1) A method of laminating and integrating a foam sheet and a non-foamed sheet constituting the light reflecting plate by a coextrusion method. (2) A method in which a non-foamed sheet constituting a light reflecting plate and a foamed sheet are laminated and integrated together by a coextrusion method, and (3) a non-foamed sheet is extruded and laminated on one surface of the foamed sheet constituting the light reflecting plate. (4) a method of thermally laminating a non-foamed sheet on one surface of the foamed sheet constituting the light reflecting plate, and the thickness of the non-foamed sheet can be easily adjusted. The method is preferable, and among the above (1) and (2), it is more preferable to use the feed block method.

  The methods (1) and (2) will be specifically described. First, as a manufacturing apparatus, two extruders, a first extruder and a second extruder, and a co-extrusion die composed of a joining die and an annular die connected to the joining die are prepared, and the first extruder and Both second extruders are connected to the confluence die of the coextrusion die.

  Then, the thermoplastic resin and the foaming agent are supplied to the first extruder and melt-kneaded to obtain a foamable thermoplastic resin composition, while the thermoplastic resin is supplied to the second extruder and in the absence of the foaming agent. To knead to make a non-foaming thermoplastic resin.

  When the light reflecting plate is composed of a foam sheet, the foam sheet and the non-foamed sheet are both lighted to the first extruder. When the light reflecting plate is composed of a non-foamed sheet, the foam sheet and the non-foamed sheet are both light. In the case of constituting a reflector, titanium oxide, primary antioxidant, secondary antioxidant, ultraviolet absorber and hindered amine light stabilizer are further supplied to both the first and second extruders.

  Next, the foamable thermoplastic resin composition of the first extruder and the non-foamable thermoplastic resin of the second extruder are supplied to the joining die of the coextrusion die and joined together to form a foamable thermoplastic resin having an annular cross section. The foamable laminate is formed by forming a foamable laminate comprising a composition layer and a non-foamable thermoplastic resin layer laminated on either the inner or outer surface of the foamable thermoplastic resin composition layer. Is supplied to an annular die connected to a converging die and extruded and foamed from the annular die into a cylindrical shape to obtain a cylindrical foam.

  Subsequently, after gradually expanding the diameter of the cylindrical foam and supplying it to the cooling mandrel to cool the cylindrical foam, the cylindrical foam is continuously inserted between the inner and outer peripheral surfaces in the extrusion direction. It is possible to obtain a light-reflecting laminated plate in which a foamed sheet or a non-foamed sheet is laminated and integrated on one surface of the light-reflecting plate. When both titanium oxide, primary antioxidant, secondary antioxidant, ultraviolet absorber and hindered amine light stabilizer are supplied to both the first and second extruders, both foam sheet and non-foam sheet are used. It becomes a light reflector.

  The ratio of the outer diameter of the inner die at the opening of the annular die to the outer diameter of the cooling mandrel on the extruder side (outer diameter of the cooling mandrel on the extruder side / outer diameter of the inner die), so-called The blow-up ratio is preferably 2.5 to 3.5.

  The light reflection plate or the light reflection laminated plate is irradiated with light emitted from a cold-cathode tube having an illuminance of 11000 ± 500 lux for 1 hour. % Is preferably less than 0.2%, more preferably less than 0.2%, and particularly preferably less than 0.1%.

  Here, the illuminance of light emitted from the cold cathode tube is measured in the following manner. First, as shown in FIG. 1, a square measuring part P having a side of 20 cm is drawn on the surface of the light reflecting plate or the light reflecting laminated plate A, and the square measuring part P is parallel to the upper and lower sides. Three straight horizontal lines are drawn at intervals of 5 cm, and three straight vertical lines parallel to the left and right sides are drawn at intervals of 5 cm, and the inside of the measurement unit is divided into 16 equal parts.

  Thereafter, each vertex P1 of the square measurement part P, the intersection P1 of the horizontal and vertical lines, and the intersection P1 of the horizontal and vertical lines and the upper, lower, left and right sides of the measurement part are taken as measurement points, and these measurement points P1 A through hole A1 penetrating between the front and back surfaces of the light reflecting plate or the light reflecting laminated plate A is provided, and the light reflecting plate or the light reflecting laminated plate A is passed through the through hole A1 as shown in FIG. The measurement part B1 of the illuminance measuring device B is inserted and arranged from the back side. At this time, adjustment is made so that the tip of the measurement unit B1 of the illuminance measuring device B and the surface of the light reflecting plate or the light reflecting laminated plate A coincide with each other, and the light is reflected through the measuring point P1. The light leakage prevention member C is used to block the gap between the through hole A1 of the light reflecting plate or light reflecting laminated plate A and the measuring part B1 of the illuminance measuring device B so as not to escape to the back side of A. Note that the shape of the light leakage preventing member C may not be the shape shown in FIG. 2 as long as light does not escape to the back surface side of the light reflecting plate or the light reflecting laminated plate A through the measurement point P1.

  Next, in an environment of room temperature of 20 ° C. and relative humidity of 60%, light is irradiated from the cold cathode tube D toward the light reflecting plate or the light reflecting laminated plate A, and the illuminance of light at each measuring point P1 is measured at each measuring point. Measure using the illuminance measuring instrument B arranged in P1. Then, the arithmetic mean value of the illuminance of the light measured at each measurement point P1 is set as the illuminance of the light applied to the light reflecting plate or the light reflecting laminated plate A. The illuminance measuring device is commercially available from Konica Minolta under the trade name “Digital Illuminometer T-1”, for example.

  The light reflecting plate of the present invention can be used by being incorporated in a direct light type backlight, a sidelight type backlight, or a planar light source type backlight constituting a liquid crystal display device.

  Further, the light reflector of the present invention is a backlight unit of a liquid crystal display device such as a word processor, a personal computer, a mobile phone, a navigation system, a television, and a portable television, and a backlight of a surface emitting system such as an illumination box. It can also be used by being incorporated in an illuminating device constituting a light, a slot illuminator, a copying machine, a projector type display, a facsimile, an electronic blackboard or the like. The lighting device of the present invention includes at least the light reflecting plate or the light reflecting laminated plate and a light source.

  The light reflecting plate of the present invention comprises 100 parts by weight of a thermoplastic resin, 10 to 100 parts by weight of titanium oxide, 0.01 to 0.8 part by weight of a primary antioxidant, and 0.01 to 0.8 part by weight of a secondary antioxidant. Part, a thermoplastic resin composition containing 0.01 to 0.8 parts by weight of an ultraviolet absorber and 0.01 to 0.8 parts by weight of a hindered amine light stabilizer, and is formed into a primary antioxidant. In addition to preventing yellowing due to deterioration of the thermoplastic resin by the agent and the secondary antioxidant, in addition to preventing the decomposition of the UV absorber and the hindered amine light stabilizer by titanium oxide, This protected ultraviolet absorber and hindered amine light stabilizer prevent the oxidative degradation of organic substances by titanium oxide and suppress the photochemical change of titanium oxide. Therefore, the light reflector of the present invention is initially prepared. Together to have a light total reflection index is never lowered significantly in a short time, maintaining the excellent light total reflectance for a long period of time.

(Example 1)
Homopolypropylene (trade name “PL500A” manufactured by Sun Allomer Co., Ltd., melt flow rate: 3.3 g / 10 min, density: 0.9 g / cm ³ ) 50 parts by weight, rutile type titanium oxide in ethylene-propylene block copolymer 50 parts by weight of a master batch (trade name “PPM 1KB662 WHT FD” manufactured by Toyo Ink Co., Ltd., ethylene-propylene block copolymer: 30% by weight, titanium oxide: 70% by weight) containing phenol, phenolic as a primary antioxidant 0.1 parts by weight of an antioxidant (trade name “IRGANOX1010” manufactured by CIBA), 0.1 part by weight of a phosphorus-based antioxidant (trade name “IRGAFOS168” manufactured by CIBA) as a secondary antioxidant, and as an ultraviolet absorber Benzotriazole UV absorber (trade name “TINUVIN326” manufactured by CIBA) 0 A thermoplastic resin composition comprising 15 parts by weight and 0.15 parts by weight of a hindered amine light stabilizer (trade name “TINUVIN111” manufactured by CIBA) is supplied to a single screw extruder having a diameter of 90 mm and melt-kneaded. After melt-kneading at 200 ° C., it is extruded from a die of a T die (sheet width: 500 mm, slit interval: 0.8 mm) attached to the tip of the extruder after being held at 190 ° C. at the tip of the extruder. A light reflecting plate having a density of 1.3 g / cm ³ made of a non-foamed sheet was obtained by taking it up to 0.3 mm with a take-up machine.

(Example 2)
The phenolic antioxidant, which is a primary antioxidant, is 0.05 parts by weight instead of 0.1 part by weight, and the phosphorus antioxidant, which is a secondary antioxidant, is 0.001 part by weight instead of 0.1 part by weight. 05 parts by weight, 0.075 parts by weight of a benzotriazole-based ultraviolet absorber as an ultraviolet absorber instead of 0.15 parts by weight, and 0.075 parts by weight of a hindered amine light stabilizer instead of 0.15 parts by weight A light reflecting plate made of a non-foamed sheet having a thickness of 0.3 mm and a density of 1.3 g / cm ³ was obtained in the same manner as in Example 1 except that the parts were used.

(Example 3)
A tandem type extruder in which a second-stage single-screw extruder (caliber: 115 mm) was connected to the tip of a first-stage single-screw extruder (caliber: 90 mm) via a connecting tube was prepared. And 40 parts by weight of homopolypropylene (trade name “PF814” manufactured by Sun Allomer, melt flow rate: 2.8 g / 10 min, density: 0.9 g / cm ³ ), homopolypropylene (trade name “PL500A” manufactured by Sun Allomer), Melt flow rate: 3.3 g / 10 min, density: 0.9 g / cm ³ ) 10 parts by weight, masterbatch containing rutile titanium oxide in an ethylene-propylene block copolymer (product of Toyo Ink Co., Ltd.) Name “PPM 1KB662 WHT FD”, ethylene-propylene block copolymer: 30% by weight, titanium oxide: 70% by weight) 50 parts by weight, 1.0 part by weight of a mixture of sodium bicarbonate and citric acid as a foaming agent, primary 0.1 weight of phenolic antioxidant (trade name “IRGANOX1010” manufactured by CIBA) as an antioxidant Part by weight, 0.1 parts by weight of a phosphorus-based antioxidant (trade name “IRGAFOS168” manufactured by CIBA) as a secondary antioxidant, and a benzotriazole-based UV absorber (trade name “TINUVIN326” manufactured by CIBA) as a UV absorber A thermoplastic resin composition comprising 0.15 parts by weight and 0.15 parts by weight of a hindered amine light stabilizer (trade name “TINUVIN111” manufactured by CIBA) is supplied to the first stage extruder and melted at 200 ° C. After kneading, 1.54 parts by weight of butane (isobutane / normal butane (% by weight) = 35: 65) with respect to 100 parts by weight of the polypropylene resin is press-fitted into the first-stage extruder and further melt-kneaded and foamed. A thermoplastic resin composition was obtained.

  Subsequently, the foamable thermoplastic resin composition is continuously supplied from the first-stage single-screw extruder to the second-stage single-screw extruder through the connecting pipe to cool the foamable thermoplastic resin composition to 170 ° C. Then, it was continuously supplied to an annular die attached to the tip of the second stage single screw extruder and extruded and foamed into a cylindrical shape to continuously produce a cylindrical foam. The annular die had an inner diameter of 140 mm and a slit interval of 0.6 mm at the opening.

Thereafter, the cylindrical foam is taken up while gradually expanding the diameter, and molded along a cylindrical cooling mandrel having a diameter of 424 mm and a length of 500 mm, in which cooling water of 25 ° C. is circulated. However, after cooling by blowing air over the entire outer peripheral surface of the cylindrical foam from the air outlet of the air ring disposed in a state surrounding the cooling mandrel, the cylindrical foam is opposed to the diametrical direction. The light reflecting plate made of a foamed sheet having a thickness of 0.5 mm and a density of 0.7 g / cm ³ was obtained by cutting between the inner and outer peripheral surfaces at a point, and opening and developing.

Example 4
Prepare the tandem extruder used in Example 3 and a single-screw extruder with a diameter of 90 mm, and join together the second-stage single-screw extruder of the tandem extruder and the single-screw extruder with a diameter of 90 mm. While being connected to the die, an annular die was connected to the merging die.

Homopolypropylene (trade name “PF814” manufactured by Sun Allomer Co., Ltd., melt flow rate: 2.8 g / 10 min, density: 0.9 g / cm ³ ) 50 parts by weight, homopolypropylene (trade name “PL500A” manufactured by Sun Allomer Co., Ltd.), melt flow Late: 3.3 g / 10 min, density: 0.9 g / cm ³ ) 30 parts by weight, masterbatch containing rutile titanium oxide in ethylene-propylene block copolymer (trade name “Toyo Ink Co., Ltd.” PPM 1KB662 WHT FD ”, ethylene-propylene block copolymer: 30% by weight, titanium oxide: 70% by weight) 20 parts by weight, thermoplastic comprising 1.0 part by weight of a mixture of sodium bicarbonate and citric acid as a foaming agent After the resin composition is supplied to the first stage extruder and melt-kneaded at 200 ° C., 100 weight polypropylene resin And the foamed thermoplastic resin composition and further kneaded by press-fitting 1.16 parts by weight of butane (isobutane / n-butane (weight%) = 35:65) to the first stage of the extruder with respect to part.

  Subsequently, the foamable thermoplastic resin composition is continuously supplied from the first-stage single-screw extruder to the second-stage single-screw extruder through the connecting pipe to cool the foamable thermoplastic resin composition to 170 ° C. After that, it was continuously fed to a confluence die attached to the tip of the second stage single screw extruder.

On the other hand, homopolypropylene (trade name “PL500A” manufactured by Sun Allomer Co., Ltd., melt flow rate: 3.3 g / 10 min, density: 0.9 g / cm ³ ) 50 parts by weight, rutile type in the ethylene-propylene block copolymer. Master batch containing titanium oxide (trade name “PPM 1KB662 WHT FD”, manufactured by Toyo Ink Co., Ltd., ethylene-propylene block copolymer: 30% by weight, titanium oxide: 70% by weight) 50 parts by weight as a primary antioxidant 0.1 part by weight of a phenolic antioxidant (trade name “IRGANOX1010” manufactured by CIBA), 0.1 part by weight of a phosphorus antioxidant (trade name “IRGAFOS168” manufactured by CIBA) as a secondary antioxidant, UV absorption Benzotriazole UV absorber (trade name “TINUVIN 326 manufactured by CIBA Co., Ltd.) ) 0.15 parts by weight and hindered amine light stabilizer (trade name “TINUVIN111” manufactured by CIBA) 0.15 parts by weight of non-foaming thermoplastic resin composition is supplied to a single screw extruder having a diameter of 90 mm Then, after melt-kneading at 200 ° C., it was kept at 190 ° C. at the tip of the extruder and continuously supplied to a confluence die attached to the tip of the extruder.

  Then, a foamable thermoplastic resin composition extruded from the second single-screw extruder of the tandem extruder, and a non-foamable thermoplastic resin composition extruded from a single-screw extruder having a diameter of 90 mm A non-foaming heat layer laminated on the outer surface of a foamable thermoplastic resin composition layer having an annular cross section made of a foamable thermoplastic resin composition and joined by a joining die. A foamable laminate comprising a non-foamable thermoplastic resin composition layer comprising a plastic resin composition is formed, and the foamable laminate is supplied to an annular die connected to a merging die, and from the annular die to a cylindrical shape A cylindrical foam was obtained by extrusion foaming. The annular die had an inner diameter of 140 mm and a slit interval of 0.6 mm at the opening.

Thereafter, the cylindrical foam is taken up while gradually expanding the diameter, and molded along a cylindrical cooling mandrel having a diameter of 424 mm and a length of 500 mm, in which cooling water of 25 ° C. is circulated. However, after cooling by blowing air over the entire outer peripheral surface of the cylindrical foam from the air outlet of the air ring disposed in a state surrounding the cooling mandrel, the cylindrical foam is opposed to the diametrical direction. In this respect, the light reflecting laminated plate in which the foamed sheet was laminated and integrated on one surface of the light reflecting plate made of a non-foamed sheet was obtained by cutting between the inner and outer peripheral surfaces, and opening and developing. The obtained light reflecting laminate had an overall thickness of 0.7 mm, a non-foamed sheet thickness of 0.3 mm, a foamed sheet thickness of 0.4 mm, and an overall density of 0.8 g / cm ³ . .

(Example 5)
In the first stage of the tandem extruder, 0.1 parts by weight of a phenolic antioxidant (trade name “IRGANOX1010” manufactured by CIBA) as a primary antioxidant and a phosphorus antioxidant (as a secondary antioxidant) 0.1 parts by weight of CIBA product name “IRGAFOS168”), 0.15 parts by weight of benzotriazole UV absorber (trade name “TINUVIN326” manufactured by CIBA) as a UV absorber, and hindered amine light stabilizer (CIBA) A light-reflecting laminate was obtained in the same manner as in Example 4 except that 0.15 part by weight of a trade name “TINUVIN111” manufactured by the company was further added. The obtained light reflecting laminate had an overall thickness of 0.7 mm, a non-foamed sheet thickness of 0.3 mm, a foamed sheet thickness of 0.4 mm, and an overall density of 0.8 g / cm ³ . .

(Comparative Example 1)
A thickness of 0 was obtained in the same manner as in Example 1 except that the phenolic antioxidant, phosphorus antioxidant, benzotriazole ultraviolet absorber, and hindered amine light stabilizer were not added to the single screw extruder. A light reflector having a thickness of ³ mm and a density of 1.3 g / cm ³ was obtained.

(Comparative Example 2)
The thickness was set to 0. 3 as in Example 3 except that the phenolic antioxidant, phosphorus antioxidant, benzotriazole ultraviolet absorber, and hindered amine light stabilizer were not added to the tandem extruder. A light reflecting plate having a density of 5 g and a density of 0.7 g / cm ³ was obtained.

(Comparative Example 3)
Except that a phenolic antioxidant, a phosphorus antioxidant, a benzotriazole ultraviolet absorber, and a hindered amine light stabilizer were not added to a single screw extruder having a diameter of 90 mm, the same as in Example 4. A light reflecting laminate was obtained. The obtained light reflecting laminate had an overall thickness of 0.7 mm, a non-foamed sheet thickness of 0.3 mm, a foamed sheet thickness of 0.4 mm, and an overall density of 0.8 g / cm ³ . .

(Comparative Example 4)
A light reflector having a thickness of 0.3 mm and a density of 1.3 g / cm ³ was obtained in the same manner as in Example 1 except that no phenol-based antioxidant was added.

(Comparative Example 5)
A light reflector having a thickness of 0.3 mm and a density of 1.3 g / cm ³ was obtained in the same manner as in Example 1 except that no phosphorylation inhibitor was added.

(Comparative Example 6)
A light reflector having a thickness of 0.3 mm and a density of 1.3 g / cm ³ was obtained in the same manner as in Example 1 except that the benzotriazole-based ultraviolet absorber was not added.

(Comparative Example 7)
A light reflector having a thickness of 0.3 mm and a density of 1.3 g / cm ³ was obtained in the same manner as in Example 1 except that the hindered amine light stabilizer was not added.

  The luminance evaluation, backlight unit (BLU) built-in irradiation evaluation, and yellow index (YI) change (ΔYI) of the obtained light reflecting plate and light reflecting laminated plate were measured in the following manner, and the results are shown in Table 1. It was shown to.

(Luminance evaluation)
As shown in FIG. 3, the light reflecting plate A is disposed on the front surface of the U-shaped frame 1 facing upward in the cross section, and 15 cold-cathode tubes 2 having a diameter of 4 mm are provided at a position 5 mm ahead of the light reflecting plate A, Further, a backlight unit having an effective screen size of 52 cm × 30 cm, in which a diffusion plate 3, a diffusion sheet 4, a prism sheet 5 and a diffusion sheet 6 are arranged in this order in front of the cold cathode fluorescent lamp 2. Produced.

  All the cold-cathode tubes using the light reflecting plate or the light reflecting laminated plate A obtained in each of the examples or comparative examples as the light reflecting plate disposed in front of the frame 1 of the backlight unit disposed in the dark room. Was lit for 1 hour in an environment of room temperature 20 ° C. and relative humidity 60%. When the light reflecting laminate A is disposed on the front surface of the frame 1, the light reflecting plate is disposed facing the cold cathode tube 2 (the light reflecting plate of Example 5 is a non-foamed sheet made of a cold cathode). It was arranged in a state facing the tube 2 side). The light emitted from the cold cathode fluorescent lamp 1 to the light reflecting plate or the light reflecting laminated plate A had an illuminance of 11000 lux.

  An imaginary straight line parallel to the edge of the diffusion sheet 6 is drawn on the surface of the diffusion sheet 6 of the backlight unit in a grid pattern at intervals of 10 cm as shown in FIG. 4, and the luminance at nine intersections of this grid is represented by the color luminance. Measurement was performed using a total (trade name “BM-7” manufactured by Topcon Techno House Co., Ltd.). And the arithmetic mean value of the brightness | luminance in each intersection was made into the brightness | luminance. In addition, it adjusted so that the intersection E might be located in the intersection of the diagonal of the diffusion sheet 6. FIG.

(Evaluation of built-in backlight unit (BLU) irradiation)
First, the total light reflectance of the light reflecting plate or the light reflecting laminated plate A before being incorporated in the backlight unit used in the luminance evaluation was measured to obtain the total light reflectance before incorporating the backlight unit (BLU) (Table 1 is described in the column “Before BLU incorporation”). The measurement of the total light reflectance of the light reflecting plate or the light reflecting laminated plate A was performed as follows.

  The light reflection plate or light reflection laminated plate A has a total light reflectance of a light reflection of a wavelength of 550 nm when a total reflection light measurement is performed under an incident condition of 8 ° in accordance with measurement method B described in JIS K7105. The rate was measured under an environment of room temperature of 20 ° C. and a relative humidity of 60%, and the value was shown as a relative value when the light reflectance when a barium sulfate plate was used as the standard reflector was 100. The total light reflectance of the light reflecting plate or the light reflecting laminate A is prepared by 30 light reflecting plates or light reflecting laminates A, and the total light reflectance of each light reflecting plate or light reflecting laminate A is prepared. The arithmetic average value of

  Specifically, the total light reflectance of the light reflecting plate and the light reflecting laminated plate A is measured by an ultraviolet-visible spectrophotometer commercially available from Shimadzu Corporation under the trade name “UV-2450”, and a product from Shimadzu Corporation. The measurement was performed in combination with an integrating sphere attachment device (inner diameter: φ60 mm) commercially available under the name “ISR-2200”.

  Next, a backlight unit used for luminance evaluation was prepared. As the light reflecting plate disposed in front of the frame 1 of the backlight unit disposed in the dark room, the light reflecting plate or the light reflecting laminated plate A obtained in each example or comparative example is used, and all the cold cathode tubes are used. 2 is turned on for 1 hour in an environment of room temperature 20 ° C. and relative humidity 60%, and then the light reflection plate or light reflection laminate A is taken out from the backlight unit, and the room temperature is 20 ° C. and relative humidity 60 is in the dark room. % Environment for 15 minutes.

  The light reflecting plate or the light reflecting laminated plate A is taken out from the backlight unit and left for 15 minutes. This is because the light reflecting plate or the light reflecting laminated plate A is heated, This is to eliminate the influence of heat in the reflectance measurement. The total light reflectance immediately after the light reflecting plate or the light reflecting laminated plate A is taken out from the backlight unit and the total light reflectance after 15 minutes from the taking out can be regarded as the same if the influence of heat is excluded. .

  When the light reflecting laminate was disposed on the front surface of the frame 1, the light reflecting plate was disposed facing the cold cathode tube 2 (the light reflecting plate of Example 5 is a non-foamed sheet cooled). It was arranged in a state facing the cathode tube 2 side). The light irradiated from the cold cathode fluorescent lamp 1 to the light reflecting plate or the light reflecting laminated plate had an illuminance of 11000 lux.

  Thereafter, the total light reflectance of each light reflecting plate or light reflecting laminated plate A was measured as described above. This procedure is performed for 30 light reflecting plates or light reflecting laminated plates A for each example or comparative example, and the arithmetic mean value of the total light reflectance of each light reflecting plate or light reflecting laminated plate A is calculated as a backlight unit. (BLU) The total light reflectance for 1 hour after incorporation (in Table 1, it is described in the column of “1 h after incorporation of BLU”).

  Further, after taking out the light reflecting plate or the light reflecting laminated plate from the backlight unit, the total light reflectivity after being left in a dark room at room temperature of 20 ° C. and a relative humidity of 60% for 24 hours is measured as described above. did. This procedure is performed for 30 light reflecting plates or light reflecting laminated plates A for each example or comparative example, and the arithmetic average value of the total light reflectance of each light reflecting plate or light reflecting laminated plate A is 24 hours. It was set as the total light reflectance after being left (in Table 1, it is described in the column “after 24 hours”).

(Change of yellow index (YI) (ΔYI))
In the backlight unit (BLU) built-in irradiation evaluation, the yellow index (yellow index before built-in) of the light reflecting plate or the light reflecting laminated plate before the backlight unit and the above-mentioned backlight unit (BLU) built-in irradiation evaluation In the same manner as described above, the yellow index of the light reflecting plate or the light reflecting laminated plate after being mounted on the front surface of the frame 1 of the backlight unit disposed in the dark room and receiving light from the cold cathode tube for one hour ( The yellow index after incorporation) was measured using a spectrocolorimeter (trade name “CM-2600d” manufactured by Konica Minolta, Inc.) according to ASTM D1925, and the difference between the yellow index after incorporation and the yellow index before incorporation Was calculated as the yellow index change (ΔYI). A smaller yellow index change (ΔYI) indicates a smaller degree of yellowing.

  Comparing the example and the comparative example, the change in the yellow index (ΔYI) is comparable, and the significant reduction in the total light reflectance in the light reflecting plate or the light reflecting laminated plate of the comparative example is the photochemical change of titanium oxide. It can be seen that this is not caused by yellowing of homopolypropylene and discoloration by additives.

It is the front view which showed the measurement part at the time of measuring the illumination intensity of a light reflection board or a light reflection laminated board. It is the schematic diagram which showed the provision point of the illumination intensity measuring device at the time of measuring the illumination intensity of a light reflection board or a light reflection laminated board. It is the longitudinal cross-sectional view which showed the backlight unit. It is the schematic diagram which showed the measurement point of the diffusion sheet surface at the time of measuring the brightness | luminance of a light reflection board or a light reflection laminated board.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Frame 2 Cold cathode tube 3 Diffusion plate 4 Diffusion sheet 5 Prism sheet 6 Diffusion sheet A Light reflecting plate or light reflecting laminated plate

Claims (8)

100 parts by weight of thermoplastic resin, 10 to 100 parts by weight of titanium oxide, 0.01 to 0.8 part by weight of primary antioxidant, 0.01 to 0.8 part by weight of secondary antioxidant, 0.01 to UV absorber A light reflector obtained by molding a thermoplastic resin composition containing ˜0.8 parts by weight and hindered amine light stabilizers 0.01 to 0.8 parts by weight. 2. The reduction in total light reflectance after irradiating light having an illuminance of 11000 ± 500 lux emitted from a cold cathode tube for 1 hour is less than 0.3%. Light reflector. The light reflecting plate according to claim 1 or 2, wherein the total light reflectance is 95% or more. The light reflecting plate according to claim 1, wherein the thermoplastic resin is a polyolefin resin. The light reflecting plate according to claim 1, wherein the primary antioxidant is a phenolic antioxidant. The light reflecting plate according to claim 1, wherein the secondary antioxidant is a phosphorus-based antioxidant. An illuminating device using the light reflecting plate according to any one of claims 1 to 6. A display device using the light reflecting plate according to claim 1.

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