JP2010145908A - Light reflecting sheet and method of manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To inexpensively manufacture a light reflection sheet having excellent light reflectivity, formed of resin foam body. <P>SOLUTION: As a resin composition for obtaining the light reflection sheet, a filler A having a higher refractive index than thermoplastic resin by 1.0 or more and a filler B having a smaller average particle size than the filler A are mixed with the thermoplastic resin at 9-15 wt.% in total of the whole resin composition, and the quantity of filler A mixed is 25-75 wt.% of the whole filler. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a light reflecting sheet made of a resin foam excellent in light reflectivity, and a method for producing the light reflecting sheet at a low cost.

  With the recent trend toward energy saving, light reflecting sheets for effectively using light from a light source are used in fluorescent lamps, signboards, liquid crystal displays, and the like. In any case, a higher total light reflectivity (hereinafter simply referred to as “reflectance”) is advantageous in terms of both energy and cost, and so far, ingenuity has been made for obtaining a light reflection sheet having high reflectivity.

  In general, light reflection occurs at the interface between substances having different refractive indexes, and the intensity of reflection increases as the difference in refractive index between the two substances increases. Therefore, in order to increase the reflectance of the sheet, a large number of interfaces of different substances having a large refractive index difference may be arranged in the thickness direction of the sheet. As one of the methods for increasing the reflectivity in this way, a technique has been disclosed in which a filler having a high refractive index is mixed into a resin and foamed to cause reflection at the interface between the resin and the filler and the interface between the resin and the bubble. ing. For example, in patent document 1, after adding the inorganic filler whose refractive index difference with resin is 1.0 or more to resin, it is made to foam and the sheet | seat with a high reflectance is obtained.

Japanese Patent No. 400005123

  In the technique of Patent Document 1, the average bubble diameter of bubbles in the sheet is limited to a range of 50 to 650 μm. This is because if the bubble is made smaller than the lower limit of 50 μm, the light diffusion efficiency is lowered. However, since the technology of Patent Document 1 cannot make the bubble small, the reflectance can be increased unless a large amount of inorganic filler is added. could not. However, when a large amount of an inorganic filler is added to the resin, there is a problem that the moldability is lowered and the cost is increased.

  The present invention has been made in view of the above-described circumstances, and maintains a light diffusion efficiency, has a good moldability and is made of a resin foam excellent in light reflectivity, and the light reflection thereof. It aims at providing the method of manufacturing a sheet | seat cheaply.

  As a result of intensive studies to solve the above-mentioned problems, the present inventor has, as a result, a filler A having a refractive index higher by 1.0 or more than the refractive index of the resin, and an average particle diameter of the resin is higher than that of the filler A. It has been found that when a predetermined amount of the small filler B is added and the ratio of the filler A in the whole filler is a predetermined amount, a light reflecting sheet having a high reflectance can be manufactured. In addition, an average particle diameter means the value measured based on X50 of JISZ8825 (laser diffraction method).

This invention was made | formed based on the knowledge mentioned above, and provides the manufacturing method of the light reflection sheet shown to following (1)-(5), and the light reflection sheet shown to following (6).
(1) A light reflecting sheet made of a resin foam, wherein the resin composition for obtaining the resin foam has a refractive index higher by 1.0 or more than the thermoplastic resin relative to the thermoplastic resin. And filler B having an average particle diameter smaller than that of filler A is 9 to 15 wt% of the total amount of the thermoplastic resin, filler A and filler B, and the amount of filler A is the filler A and filler. The light reflecting sheet, which is 25 to 75 wt% of the total amount of B.
(2) The light reflecting sheet according to (1), wherein the filler A is titanium oxide.
(3) The light reflecting sheet according to (1) or (2), wherein the filler B is calcium carbonate.
(4) The light reflecting sheet according to (1) to (3), wherein the filler A has an average particle size of 100 to 500 nm.
(5) The light reflecting sheet according to (1) to (4), wherein the average particle size of the filler B is 100 nm or less.
(6) A method for producing a light reflecting sheet according to (1) to (5), wherein a multi-row foam obtained by extruding the resin composition from an extruder having a perforated die is compressed into a sheet shape. A method for producing a light reflecting sheet.

  In the present invention, the filler A has a role of reflecting light at the interface between the resin and the filler and enhancing the light concealing property. In order to improve the light concealing property, the particle diameter of the filler must be about half the wavelength of the light, but this restriction has contributed to making it difficult to reduce the bubbles. Therefore, if filler B having an average particle diameter smaller than that of filler A is added, filler B functions as a cell nucleating agent, and the bubbles can be made fine. Further, since the filler B having a small average particle diameter helps light diffusion, the light diffusion efficiency is not lowered. Therefore, when the filler A and the filler B are used in combination, a light reflection sheet having a higher light diffusion efficiency and a higher reflectance than when the filler A or the filler B is used alone can be obtained. Moreover, if a cheaper material than the filler A is used as the filler B, a foam sheet having a high reflectance can be manufactured at a low cost.

  The light reflecting sheet according to the present invention has high light diffusion efficiency and excellent light reflectivity. Moreover, according to the manufacturing method of the light reflection sheet which concerns on this invention, the light reflection sheet of this invention can be manufactured cheaply.

  Hereinafter, the present invention will be described in more detail. The reflectance (total light reflectance) of the light reflecting sheet according to the present invention is desirably 97% or more. It is because the performance as a light reflection sheet is inferior when the reflectance is less than 97%. The reflectance referred to here is 550 nm using a spectrophotometer (for example, model U-4100, standard white plate: aluminum oxide, manufactured by Hitachi High-Technologies Corporation) in accordance with measurement method B of JIS-K7105. The reflectance [%] measured at a wavelength of.

  The thickness of the light reflecting sheet is desirably 0.5 to 3.0 mm. This is because if the thickness of the light reflecting sheet is less than 0.5 mm, the sheet is easily torn during secondary molding, and if it exceeds 3.0 mm, handling becomes worse and the installation location is limited. Considering the balance between secondary formability and handling, the thickness of the light reflecting sheet is preferably 0.5 to 2.0 mm, more preferably 0.5 to 1.0 mm.

  The expansion ratio of the light reflecting sheet is desirably 1.5 to 10 times. This is because if the expansion ratio is less than 1.5 times, sufficient reflectance cannot be obtained, and the cost of the material increases. If the expansion ratio exceeds 10, the rigidity of the light reflecting sheet is insufficient. . Considering the balance of reflectance, material cost, and rigidity, the foaming ratio of the light reflecting sheet is preferably 2 to 8 times, and more preferably 2 to 5 times. Foaming ratio here refers to foaming in which the density of the thermoplastic resin composition before foaming is measured with an electronic balance (for example, model: AG204, manufactured by METTLER TOLEDO) in accordance with JIS K7112 Method A (submersion method). The value obtained by dividing by the density of the body.

  In the present invention, the main resin component constituting the light reflecting sheet is not particularly limited. For example, polyolefin resins such as polyethylene and polypropylene, polyester resins such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, and polypropylene terephthalate, polystyrene , Styrene resins such as acrylonitrile-styrene copolymer, acrylonitrile-butadiene-styrene copolymer, polycarbonate, polyamide, polyether, polyurethane, polyphenylene sulfide, polyesteramide, polyetherester, polyvinyl chloride, polymethacrylate, Modified polyphenylene ether, polyarylate, polysulfone, polyetherimide, polyamideimide, polyimide And it can be exemplified mixtures of copolymers, or these resins to them as a main component. A polyolefin resin or a polyester resin is particularly preferable from the viewpoint of low absorption in the visible light region.

  Examples of polyolefin resins include low density polyethylene, linear low density polyethylene, high density polyethylene, polypropylene, ethylene propylene rubber, ethylene-propylene-diene terpolymer, styrene butadiene rubber, ethylene vinyl acetate copolymer, Examples thereof include, but are not limited to, ethylene vinyl alcohol resin, ethylene ethyl acrylate resin, and ethylene acrylic acid resin. Furthermore, modified products such as silane-modified products and carboxylic acid-modified products of the above resins can be used, and these resins can be used alone or as a mixture of two or more. Considering the balance between price and heat resistance, polypropylene resin is particularly preferable.

  The polypropylene resin used in the present invention is not particularly limited as long as propylene is homopolymerized by a known method. The stereoregularity of the polymer side chain is not particularly limited, and any of isotactic, syndiotactic, and atactic polypropylene can be used. Further, not only a propylene homopolymer but also a propylene copolymer which is a copolymer of propylene and a non-propylene monomer may be used. Propylene copolymers include random, block, and graft copolymers of propylene and olefin monomers selected from the group consisting of ethylene, alpha olefins having 3 to 8 carbon atoms, and dienes having 4 to 10 carbon atoms.

  There is no particular limitation on the melt tension of the polypropylene resin, and either general-purpose polypropylene or high melt tension polypropylene may be used. The high melt tension polypropylene here refers to a capillary rheometer (for example, Capillograph 1C manufactured by Toyo Seiki Seisakusho Co., Ltd.) with a die having a diameter of 2 mm, a land length of 8 mm, and an inflow angle of 90 °, a temperature of 230 ° C., and a piston descending speed of 20 mm. / Min, a polypropylene having a value of 100 mN or more when the melt tension is measured at a take-up speed of 2 m / min. These polypropylenes may be used alone or in combination of two or more.

  The melt flow rate (hereinafter referred to as MFR) of the polypropylene resin is preferably in the range of 0.1 to 10 g / 10 min. This is because if the MFR is less than 0.1 g / 10 min, the load is too high and extrusion tends to be difficult, and if the MFR exceeds 10 g / 10 min, it is difficult to keep the die pressure sufficiently high. Considering the balance between the load during extrusion and the pressure of the die, the MFR is preferably 0.5 to 8 g / 10 min, more preferably 1 to 5 g / 10 min. The MFR of the polypropylene resin is a value measured at a temperature of 230 ° C. and a load of 2.16 kg (condition code name M) by the method defined in JIS K7210.

  In the resin composition used in the present invention, various additives such as an antioxidant, an antistatic agent, a crystal nucleating agent, a lubricant, an ultraviolet absorber, a light stabilizer, a fluorescent enhancer are used within the range not inhibiting the effects of the present invention. Whitening agents, dyes, pigments, processing aids, impact modifiers, fillers and the like may be added.

  In the present invention, the filler A is not particularly limited as long as it is a filler having a refractive index higher by 1.0 or more than the refractive index of the resin, more preferably 1.0 to 1.1 higher. Examples of the filler A include, but are not limited to, particles such as titanium oxide, zirconium oxide, and potassium titanate, or a mixture thereof. Among these, when titanium oxide, particularly rutile type titanium oxide is used, a light reflecting sheet having high concealability and reflectance can be obtained at a low cost. In order to prevent aggregation of the inorganic particles, the surface of the inorganic particles may be treated with a coupling agent. The average particle size of the filler A is preferably 100 to 500 nm, and more preferably 200 to 300 nm in order to improve the light concealing property.

  In the present invention, the filler B is not particularly limited as long as the average particle diameter is smaller than that of the filler A. More preferably, the average particle diameter of the filler B is 1/5 to 1/20 of the average particle diameter of the filler A. Examples of the filler B include calcium carbonate, talc, barium sulfate, zinc oxide, titanium oxide, magnesium carbonate, alumina, silica, aluminum silicate, kaolin, kaolinite, clay, diatomaceous earth, and montmorillonite, or a mixture thereof. However, it is not limited to these. Above all, when calcium carbonate is used, a foamed sheet having fine bubbles can be obtained at low cost. In order to prevent aggregation of the inorganic particles, the surface of the inorganic particles may be treated with a coupling agent. The average particle size of the filler B is preferably 100 nm or less, and more preferably 50 nm or less, in order to enhance the effect of bubble miniaturization.

  In the present invention, the ratio of the filler A and the filler B combined is preferably 9 to 15 wt%, particularly preferably 10 to 13 wt% with respect to the total mass of the thermoplastic resin and the filler. When the total amount of the filler is less than 9 wt% with respect to the total mass of the thermoplastic resin and the filler, the effect of refining the bubbles is not sufficient, and the total amount of the filler exceeds 15 wt% with respect to the total mass of the thermoplastic resin and the filler. This is because even if many gas escapes occur and the bubbles become finer, the foaming ratio is low and the reflectivity decreases.

  In the present invention, the proportion of the filler A in the whole filler is preferably 25 to 75 wt%, particularly 50 to 75 wt%, with respect to the total mass of the filler A and the filler B. If the amount of filler A with respect to the whole filler is less than 25 wt%, the reflectivity will decrease due to the decrease in filler having a high refractive index, and if the amount of filler A with respect to the entire filler exceeds 75 wt%, the fineness of the bubbles will be insufficient. This is because the reflectance is also lowered.

  In the present invention, as the foaming agent, either a chemical foaming agent or a physical foaming agent may be used. Chemical foaming agents include azodicarbonamide, N, N′-dinitrosopentamethylenetetramine, 4,4′-oxybis (benzenesulfonylhydrazide), sodium hydrogen carbonate, bistetrazole diammonium, bistetrazole piperazine, 5- Phenyltetrazole or the like can be used alone or in a suitable blend, but is not limited thereto. Further, a decomposition aid (such as urea) for adjusting the decomposition temperature may be added to these chemical foaming agents.

  As the physical foaming agent, inorganic gas such as carbon dioxide, nitrogen, water, air, argon, helium, rare gas, or organic gas such as butane and pentane can be used alone or in combination. It is not limited. Carbon dioxide is desirable in consideration of safety during production and high solubility in the resin.

  When carbon dioxide is used as the foaming agent, the concentration of carbon dioxide in the entire mixture of the resin composition and carbon dioxide is preferably 3 to 15 wt%. When the ratio of carbon dioxide is less than 3 wt%, a sufficient number of bubbles and expansion ratio cannot be obtained. When the ratio is more than 15 wt%, outgassing and bubble breakage increase, resulting in a sufficient number of bubbles and expansion ratio. Because there is no. Considering the balance between the number of bubbles and the expansion ratio, the concentration of carbon dioxide is preferably 3 to 12 wt%, more preferably 5 to 10 wt%. The gas concentration here is a value obtained by dividing the gas flow rate [g / min] measured by a mass flow meter (for example, D006H-SS-200 manufactured by Oval) by the discharge amount [g / min] and multiplying by 100. Say. The discharge amount is calculated as an average value by performing the operation of measuring the mass of the resin discharged from the die for 1 minute twice.

  As a method for producing the light reflecting sheet of the present invention, a so-called batch foaming method in which a resin composition is impregnated with a foaming agent and then foamed by reducing pressure or heating may be used. A so-called extrusion foaming method in which a mixture of foaming agents is extruded and foamed at the same time may be used, but is not limited thereto.

  In the case of the extrusion foaming method, the foaming agent may be kneaded into the resin composition in advance before being supplied to the extruder, or may be supplied to the molten resin composition from a nozzle provided on the side surface of the extruder. Moreover, the extruder for manufacturing the light reflection sheet of this invention may be one, and the tandem system which connected two extruders in series may be used. A tandem system is preferable from the viewpoint of increasing the gas dissolution time in the resin and sufficiently lowering the resin temperature. As the die, a T die, a circular die, a porous die and the like can be used, but the die is not limited thereto.

  As a method for producing the light reflecting sheet of the present invention, a method in which a multi-row foam obtained by extruding a resin composition from an extruder having a perforated die is compressed into a sheet shape can be preferably employed. As described above, when a porous die is used as the die and the cross-sectional shape of the hole is a perfect circle, the diameter is preferably 0.3 to 2.0 mm. If the hole diameter is less than 0.3 mm, clogging with foreign substances is likely to occur, and the die pressure increases too much, which may result in impossibility of extrusion. If the hole diameter exceeds 2.0 mm, the die pressure This is because there is a possibility that the number of bubbles and the expansion ratio cannot be maintained. Considering the balance between clogging with foreign matter, die pressure and good foamability, the diameter of each hole is preferably 0.5 to 1.5 mm, more preferably 0.5 to 1.0 mm.

  When a porous die is used as the die, the method of compressing the extruded multi-strip foam is to discontinue crushing by providing a steel belt or a forming roll immediately after the die exit, and from the top and bottom with a metal plate However, it is not limited to these. In order to obtain a wide light reflecting sheet, it is necessary to compress immediately after leaving the die, specifically, before the width of the foam shrinks to 70% of the flow path width of the porous die. preferable.

  You may provide the coating layer containing a light stabilizer as needed in the single side | surface or both surfaces of the light reflection sheet of this invention. Light stabilizers include organic light stabilizers such as hindered amine, salicylic acid, benzophenone, benzotriazole, cyanoacrylate, triazine, benzoate, and oxalic anilide, or inorganic light such as sol-gel. Although a stabilizer can be used, it is not restricted to these.

  Here, although an example of the manufacturing apparatus of the light reflection sheet which concerns on this invention is shown, the manufacturing apparatus of this invention light reflection sheet is not restricted to the following apparatus. FIG. 1 is a schematic view of the manufacturing apparatus. In the figure, 1 indicates an extruder. In the extruder 1, a hopper 2, a gas supply port 3, and a perforated die 4 are installed. In the figure, reference numeral 5 denotes a gas supply pipe connected to the gas supply port 3, 6 denotes a carbon dioxide cylinder connected to the gas supply pipe 5, and 7 denotes a gas flow rate control device interposed in the gas supply pipe 5. The extruder 1 has a role of completely melting the resin and uniformly dispersing the gas in the resin. The extruder 1 may be a single-screw extruder alone, but in order to sufficiently cool the resin at the die outlet, it is desirable to use a tandem extruder in which two extruders are connected in series. The L / D (length / diameter of the extrusion screw) of the extruder (first-stage extruder in the case of a tandem extruder) is desirably 30 or more.

  Next, with reference to FIG. 1, an example of a method for producing a light reflecting sheet according to the present invention is shown, but the method for producing a light reflecting sheet according to the present invention is not limited to the following method. First, a dry blended resin and additive mixture (hereinafter simply referred to as resin) is supplied to the hopper 2 of the extruder 1. The resin advances while melting in the barrel of the extruder 1 as the screw in the extruder 1 rotates. On the other hand, a predetermined amount of carbon dioxide controlled by the gas flow rate control device 7 is supplied from the gas supply pipe 5 to the extruder 1 at the gas supply port 3 installed in the middle of the barrel of the extruder 1. The molten resin and gas come into contact with each other at the gas supply port 3, and the gas is dissolved in the resin by the high pressure in the extruder 1. A mixture of resin and gas that is homogeneously mixed in the extruder 1 is extruded from the perforated die 4 and foamed at the same time. Finally, the target light reflecting sheet 9 can be obtained by compressing the extruded multi-row foam with the molding machine 8.

  EXAMPLES Hereinafter, although this invention is demonstrated further in detail based on an Example and a comparative example, this invention is not limited to the following Example.

Example 1
First, as shown in Table 1, filler A (rutile type) is used for resin (block polypropylene, refractive index 1.6, MFR = 1.8 g / 10 min (230 ° C., 2.16 kgf), hereinafter referred to as PP1). Titanium oxide, refractive index 2.74, average particle diameter 300 nm) 7.5 wt% and filler B (calcium carbonate, average particle diameter 20 nm) 2.5 wt% were prepared in advance as a master batch. Next, this resin composition is supplied to the hopper of a 40 mm single screw extruder (FSM-40 manufactured by Ikegai Co., Ltd., L / D = 34), and carbon dioxide is supplied from a gas supply port provided in the middle of the barrel of the extruder. Supplied. The supply pressure of carbon dioxide was fixed at 11 MPa. The temperature of the extruder was set to 170 to 190 ° C. from the hopper to the center of the extruder, and thereafter the temperature was lowered stepwise so that the resin temperature at the die outlet was 150 to 160 ° C. As shown in FIG. 2, when a layer in which 18 or 17 holes having a diameter of 0.5 mm are horizontally arranged at intervals of 2 mm is formed as one layer as shown in FIG. 2, the holes of adjacent layers are staggered. A multi-layered die with a total of 88 holes (18 holes, 17 holes, 18 holes, 17 holes, 18 holes) used. Extrusion foaming was performed at a screw speed of 40 rpm, a discharge rate of about 70 g / min, and a carbon dioxide gas flow rate of about 6 g / min. Next, the extruded foam was compressed with a steel belt (belt spacing 1 mm) installed immediately after the exit of the die to obtain a light reflecting sheet. The reflectance and expansion ratio of the obtained light reflecting sheet were measured by the above-described methods.

(Example 2)
A light reflecting sheet was prepared and the foam was investigated under the same conditions as in Example 1 except that the blending ratio of titanium oxide and calcium carbonate was changed to 5.0 wt%.

(Example 3)
Except that the blending ratio of titanium oxide was changed to 2.5 wt% and the blending ratio of calcium carbonate was changed to 7.5 wt%, the production of the light reflecting sheet and the investigation of the foam were performed under the same conditions as in Example 1. .

Example 4
A light-reflecting sheet was prepared and the foam was investigated under the same conditions as in Example 1 except that the mixing ratio of titanium oxide and calcium carbonate was changed to 6.25 wt%.

(Example 5)
A light-reflecting sheet was prepared and the foam was examined under the same conditions as in Example 1 except that the blending ratio of titanium oxide and calcium carbonate was changed to 7.5 wt%.

(Comparative Example 1)
The light reflecting sheet was prepared and the foam was examined under the same conditions as in Example 1 except that the titanium oxide content was changed to 10 wt% and calcium carbonate was not added.

(Comparative Example 2)
A light reflecting sheet was prepared and the foam was examined under the same conditions as in Example 1 except that titanium oxide was not blended and the blending ratio of calcium carbonate was changed to 10 wt%.

(Comparative Example 3)
A light reflecting sheet was prepared and the foam was investigated under the same conditions as in Example 1 except that only PP1 was foamed without blending titanium oxide and calcium carbonate.

(Comparative Example 4)
A light-reflecting sheet was prepared and the foam was examined under the same conditions as in Example 1 except that the mixing ratio of titanium oxide and calcium carbonate was changed to 3.75 wt%.

(Comparative Example 5)
A light reflecting sheet was prepared and the foam was investigated under the same conditions as in Example 1 except that the mixing ratio of titanium oxide and calcium carbonate was changed to 10 wt%.

(Comparative Example 6)
Except that the blending ratio of titanium oxide was changed to 9.0 wt% and the blending ratio of calcium carbonate was changed to 1.0 wt%, the production of the light reflecting sheet and the investigation of the foam were performed under the same conditions as in Example 1. .

(Comparative Example 7)
Except that the titanium oxide content was changed to 1.0 wt% and the calcium carbonate content was changed to 9.0 wt%, a light reflecting sheet was prepared and the foam was investigated under the same conditions as in Example 1. .

  Table 1 shows the manufacturing conditions and physical property measurement results of the light reflecting sheet. From Table 1, the light reflecting sheet of the present invention in which the filler A and the filler B are blended in an amount of 9 to 15 wt% of the entire resin composition and the blending amount of the filler A is 25 to 75 wt% of the entire filler is 97% or more. It can be seen that it has a high reflectance. On the other hand, from Table 2, all of the light reflecting sheets of the comparative examples had a reflectance of less than 97%.

It is the schematic which shows an example of the manufacturing apparatus of the light reflection sheet which concerns on this invention. It is the schematic which looked at the perforated die used in the example from the front.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Extruder 2 Hopper 3 Gas supply port 4 Die 5 Gas supply pipe 6 Carbon dioxide cylinder 7 Gas flow control device 8 Molding machine 9 Light reflection sheet

Claims (6)

  A light-reflecting sheet made of a resin foam, wherein the resin composition for obtaining the resin foam is a filler A having a refractive index higher by 1.0 or more than the thermoplastic resin with respect to the thermoplastic resin, and a filler The filler B having a smaller average particle diameter than A is added in a total amount of 9 to 15 wt% of the total amount of the thermoplastic resin, filler A and filler B, and the amount of filler A is the sum of filler A and filler B. The light reflecting sheet, which is 25 to 75 wt% of the amount.   The light reflecting sheet according to claim 1, wherein the filler A is titanium oxide.   The light reflecting sheet according to claim 1, wherein the filler B is calcium carbonate.   The light reflecting sheet according to any one of claims 1 to 3, wherein an average particle size of the filler A is 100 to 500 nm.   The light reflecting sheet according to any one of claims 1 to 4, wherein an average particle diameter of the filler B is 100 nm or less.   It is a manufacturing method of the light reflection sheet given in any 1 paragraph of Claims 1-5, Comprising: The multi line foam obtained by extruding the resin composition from the extruder which has a porous die is compressed into a sheet form. A method for producing a light reflecting sheet, comprising molding.

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