JP2012096494A - Reflector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a reflective film excellent in reflectivity, heat resistance, and rigidity.SOLUTION: A reflector includes a resin layer A that contains at least one kind of a styrene copolymer selected from a group composed of a styrene-α-methylstyrene copolymer (SAMS), a styrene-acrylic acid copolymer (SAA), a styrene-methacrylic acid copolymer (SMAA), and a styrene-maleic anhydride copolymer (SMA). Preferably, the resin layer A contains not only the styrene copolymer but also an olefin resin and/or a thermoplastic elastomer.

Description

  The present invention relates to a reflective material that can be suitably used as a constituent member of a liquid crystal display, a lighting fixture, or a lighting signboard.

  Reflective materials are used in many fields such as liquid crystal displays, lighting fixtures or lighting signs. Recently, in the field of liquid crystal displays, devices have become larger and display performance has become more advanced, and it has become necessary to improve the performance of the backlight unit by supplying as much light as possible to the liquid crystal. Even for materials, there is a demand for even better light reflectivity (also simply referred to as “reflectivity”).

As a reflective material, for example, a reflective film for a liquid crystal display using a white polyester film mainly composed of an aromatic polyester resin is known (see Patent Document 1).
However, when an aromatic polyester-based resin is used as a material for the reflecting material, the aromatic ring contained in the molecular chain of the aromatic polyester-based resin absorbs ultraviolet rays. There was a problem that the film deteriorated and yellowed, and the light reflectivity of the reflective film was lowered.

Further, by stretching a film formed by adding a filler to a polypropylene resin, a fine void is formed in the film, and light scattering reflection is caused (refer to Patent Document 2), olefin-based An olefin-based resin light reflector having a laminated structure including a base material layer containing a resin and a filler and a layer containing an olefin-based resin is also known (see Patent Document 3).
A reflective film using such an olefin resin has a feature that there are few problems of film deterioration and yellowing due to ultraviolet rays.

Furthermore, as a reflective sheet made of a resin composition not containing a large amount of inorganic powder, biaxial stretching with reduced heat shrinkage, comprising at least one of a polypropylene resin and a resin incompatible with the polypropylene resin A reflection sheet is known (see Patent Document 4).
This reflection sheet has a feature that it exhibits higher reflectance than a conventional reflection sheet having the same basis weight and density even if it does not contain a large amount of inorganic powder.

  Furthermore, a reflector having excellent heat resistance, moldability, appearance, and the like obtained by injection molding a resin composition containing a styrene polymer having a syndiotactic structure is also known (see Patent Document 5). ).

Japanese Patent Laid-Open No. 04-239540 JP-A-11-174213 JP 2005-031653 A JP 2008-158134 A JP 2003-020373 A

As described above, the reflective material using an olefin-based resin has few problems of film deterioration and yellowing due to ultraviolet rays, and its usefulness is high. However, since the heat resistance is not sufficient, when used as a constituent member of a liquid crystal display that requires heat resistance, there are problems such as shrinkage of the film due to heat and waviness.
In recent years, light sources with high-temperature heat generation such as LEDs have been used in fields such as liquid crystal displays, lighting fixtures, and lighting signs, and more heat resistance is required by reflecting materials.
On the other hand, in the reflector described in Patent Document 5, it is excellent in heat resistance and useful for use as an injection-molded product. For example, in the field of a liquid crystal display, a luminaire, or a lighting signboard, In extrusion molding and further stretching molding of the reflective sheet, since it has crystallinity and a high crystallization speed, crystallization may proceed rapidly depending on the conditions of melt extrusion and stretching operation, When bent, the sheet may crack. Further, since syndiotactic polystyrene is rigid, the sheet may break while passing through a plurality of rolls in the stretching operation.

  Accordingly, an object of the present invention is to provide a new reflecting material having excellent reflectivity and excellent heat resistance and rigidity.

  The present invention relates to styrene-α-methylstyrene copolymer (SAMS), styrene-acrylic acid copolymer (SAA), styrene-methacrylic acid copolymer (SMAA), and styrene-maleic anhydride copolymer (SMA). A reflector comprising a resin layer A containing one or more styrene copolymers selected from the group consisting of:

  The reflective material of the present invention includes a styrene-α-methylstyrene copolymer (SAMS), a styrene-acrylic acid copolymer (SAA), a styrene-methacrylic acid copolymer (SMAA), and a styrene-maleic anhydride copolymer. By providing the resin layer A containing one or more styrene copolymers selected from the group consisting of (SMA), heat resistance and rigidity can be ensured. Therefore, the reflective material of this invention can be used suitably as reflective materials, such as a liquid crystal display, a lighting fixture, or an illumination signboard.

It is a figure for demonstrating the heat resistance evaluation method performed in the Example.

  Hereinafter, a reflective material (referred to as “the present reflective material”) as an example of an embodiment of the present invention will be described. However, the present invention is not limited to this reflector.

(This reflector)
The reflective material comprises styrene-α-methylstyrene copolymer (SAMS), styrene-acrylic acid copolymer (SAA), styrene-methacrylic acid copolymer (SMAA), and styrene-maleic anhydride copolymer (SMA). And a resin layer A containing one or more styrene copolymers selected from the group consisting of:

(Resin layer A)
Resin layer A comprises styrene-α-methylstyrene copolymer (SAMS), styrene-acrylic acid copolymer (SAA), styrene-methacrylic acid copolymer (SMAA), and styrene-maleic anhydride copolymer (SMA). And a layer containing one or more styrenic copolymers selected from the group consisting of: a layer capable of imparting heat resistance to the reflector and handling properties such as rigidity. .

(resin)
As a resin (base resin) constituting the main component of the resin layer A, a styrene-α-methylstyrene copolymer (SAMS), a styrene-acrylic acid copolymer (SAA), a styrene-methacrylic acid copolymer (SMAA), By adopting one or more styrene-based copolymers selected from the group consisting of styrene-maleic anhydride copolymers (SMA), the reflective material has excellent reflection performance, rigidity, and heat resistance. Can be granted. That is, among the copolymers of styrene resin with comonomer and styrene that have improved heat resistance, among them, the styrene copolymer can maintain transparency and rigidity, and can improve heat resistance. is there.

  Furthermore, from the viewpoint of improving the heat resistance of the reflective material, the glass transition temperature (Tg) of the styrene copolymer contained in the resin layer A is preferably 85 ° C. or higher and 150 ° C. or lower, and more preferably 90 ° C. or higher. It is preferably 150 ° C. or lower, and more preferably 100 ° C. or higher and 150 ° C. or lower.

  In the resin layer A, the styrene copolymer (the total amount of these when a styrene copolymer of two or more components is included) is 50% by mass or more with respect to the mass of the entire resin layer A. Is more preferably 60% by mass or more, and particularly preferably 70% by mass or more (including 100%).

(Other resin components)
The resin layer A can also contain other resins. For example, it is preferable to contain an olefin resin and / or a thermoplastic elastomer from the viewpoint of increasing the bending strength.
By forming the resin layer A by blending the styrene copolymer with an olefin resin and / or a thermoplastic elastomer, the folding strength and the olefin resin layer that cannot be obtained by the styrene copolymer layer alone are obtained. Heat resistance and rigidity that could not be obtained alone can be secured.
At this time, the melt flow rate (referred to as “MFR”, JISK-7210, 230 ° C., load 21.18 N) of the olefin resin and / or the thermoplastic elastomer is 0.1 g / 10 min or more and 40 g / 10 min or less. In particular, it is more preferably 0.5 g / 10 min or more and 20 g / 10 min or less.
Moreover, it is preferable to adjust MFR of a styrene-type copolymer to the said range. If the MFR of both is adjusted in this way, the olefin resin and / or the thermoplastic elastomer is oriented in the styrene copolymer, and there is no possibility that the mechanical properties as a reflector are extremely deteriorated. Particularly preferred.

Examples of the olefin resin include polypropylene resins such as polypropylene and propylene-ethylene copolymer, and polyethylene resins such as polyethylene, high-density polyethylene, and low-density polyethylene. A combination of more than one species can be used. Of these, polyethylene resins and polypropylene resins are preferable, and among them, polypropylene resins are preferable from the viewpoints of high melting point and excellent heat resistance and high mechanical properties such as elastic modulus.
Also, from the viewpoint of extrusion moldability, among polypropylene resins, the melt flow rate (referred to as “MFR”, JISK-7210, 230 ° C., 21.18 N) is 0.1 g / 10 min to 20 g / 10 min, especially 0.8. Polypropylene resins having 2 g / 10 min to 10 g / 10 min, particularly 0.5 g / 10 min to 5 g / 10 min are particularly preferable.

  On the other hand, examples of the thermoplastic elastomer include olefin-based elastomers, styrene-based elastomers, urethane-based elastomers, polyester-based elastomers, and the like, and one or more of these can be used in combination. Among them, the styrene elastomer is preferable from the viewpoint of improving the homogeneity of the resin layer A because it is compatible with not only a styrene copolymer but also an olefin resin, particularly a polypropylene resin.

Examples of the styrene-based elastomer include a copolymer of styrene and a conjugated diene such as butadiene or isoprene, and / or a hydrogenated product thereof. The styrene-based elastomer is a block copolymer having styrene as a hard segment and conjugated diene as a soft segment, and does not require a vulcanization step, and is preferable. A hydrogenated product is more preferable because of high thermal stability.
Preferred examples of the styrene elastomer include, for example, a styrene-butadiene-styrene block copolymer, a styrene-isoprene-styrene block copolymer, a styrene-ethylene-butylene-styrene block copolymer, and a styrene-butadiene-butylene-styrene copolymer. Examples thereof include a polymer and a styrene-ethylene-propylene-styrene block copolymer.
In particular, styrene-ethylene-butylene-styrene block copolymers, styrene-butadiene-butylene-styrene copolymers, styrene-ethylene-propylene-styrene block copolymers, which have lost the double bond of the conjugated diene component by hydrogenation. A coalescence (also referred to as a hydrogenated styrene-based elastomer) is preferable.

  The content of the olefin resin other than the styrene copolymer and / or the thermoplastic elastomer contained in the resin layer A is preferably 5 to 45% by mass with respect to the mass of the resin layer A as a whole. More preferably, it is -30 mass%.

(Other ingredients)
The resin layer A contains other resins including styrene copolymers and styrene resins other than those described above as long as the effects of the styrene copolymer, olefin resin and / or thermoplastic elastomer are not impaired. May be. In addition, fine powder fillers, antioxidants, light stabilizers, heat stabilizers, dispersants, UV absorbers, fluorescent brighteners, compatibilizers and other additives are included within the range that does not impair the above effects. May be.

(Form of resin layer A)
The resin layer A may be a layer made of a sheet body, or may be a layer formed by forming a thin film of the molten resin composition by extrusion or coating (without forming a sheet). In the case of a sheet body, the sheet body may be an unstretched film or a uniaxial or biaxially stretched film.
In addition, the resin layer A may have a fine space | gap inside from a viewpoint of improving reflective performance. Examples of the method for forming voids in the resin layer A include the following methods.
(1) After forming a resin composition in which particles that are incompatible with the styrene copolymer are dispersed in a styrene copolymer into a sheet shape, the sheet is stretched to form fine bubbles inside the film. Forming method.
(2) A method in which at least one selected from organic hollow particles, inorganic hollow particles, organic porous particles, and inorganic porous particles is added to a styrene-based copolymer to form a melt.
(3) A method in which foamable particles are added to a styrenic copolymer and melt-extruded to foam inside the film.
(4) A method of forming a porous layer by dissolving an inert gas in a styrene copolymer at high pressure and then releasing the pressure.
These methods may be used singly or a plurality of methods may be used in combination.

(Resin layer B)
The reflective material of the present invention may have a laminated structure in which the resin layer A is provided on at least one surface of the resin layer B containing at least another resin other than the styrene-based resin and a fine filler. . By having such a configuration, while providing heat resistance and rigidity to the resin layer A, functional separation such as maintaining workability such as stretchability and bending strength while imparting reflectivity to the resin layer B. Thus, there is an advantage that heat resistance and workability can be imparted while exhibiting higher reflection performance. Therefore, in such a laminated structure, it is preferable that the resin layer B is located in the outermost layer on the light irradiation side (reflection use surface side). By setting it as such a structure, rigidity and heat resistance can be provided to a reflecting material.

(resin)
Examples of the resin (base resin) forming the main component of the resin layer B include olefin resins, polyester resins, acrylic resins, polyvinyl chloride resins, polyvinylidene chloride resins, fluorine resins, polyether resins, Polyamide resins, polyurethane resins, diene resins and the like can be mentioned. Among these, from the viewpoint of imparting reflective performance and bending workability to the present reflective material, olefin-based resins are preferable.

Examples of the olefin resin include polypropylene resins such as polypropylene and propylene-ethylene copolymers, polyethylene resins such as polyethylene, high-density polyethylene and low-density polyethylene, and cycloolefins such as ethylene-cyclic olefin copolymers. And at least one polyolefin resin selected from olefin elastomers such as ethylene resins, ethylene-propylene rubber (EPR), and ethylene-propylene-diene terpolymers (EPDM). Among these, from the viewpoint of mechanical properties, flexibility, etc., polypropylene resins and polyethylene resins are preferable, and among them, from the viewpoint of high melting point and excellent heat resistance, and high mechanical properties such as elastic modulus. Polypropylene resin is preferable.
Also, from the viewpoint of extrusion moldability, among polypropylene resins, the melt flow rate (referred to as “MFR”, JISK-7210, 230 ° C., load 21.18 N) is 0.1 g / 10 min or more, 20 g / 10 min or less, In particular, a polypropylene resin having a weight of 0.2 g / 10 min or more and 10 g / 10 min or less, particularly 0.5 g / 10 min or more and 5 g / 10 min or less is particularly preferable.

(Fine powder filler)
In order to obtain excellent light reflectivity, the resin layer B is important to contain a fine powder filler. By containing fine powder filler, in addition to refractive scattering due to refractive index difference, refractive scattering due to refractive index difference with gap formed around fine powder filler, and further formed around fine powder filler Light reflectivity can also be obtained from refractive scattering due to a difference in refractive index between the void and the fine powder filler.

Examples of the fine powder filler include inorganic fine powder and organic fine powder.
Inorganic fine powders include calcium carbonate, magnesium carbonate, barium carbonate, magnesium sulfate, barium sulfate, calcium sulfate, zinc oxide, magnesium oxide, calcium oxide, titanium oxide, zinc oxide, alumina, aluminum hydroxide, hydroxyapatite, silica, Examples include mica, talc, kaolin, clay, glass powder, asbestos powder, zeolite, silicate clay. Any of these may be used alone or in admixture of two or more. Among these, considering the difference in refractive index with the resin constituting the sheet, those having a large refractive index are preferable, and calcium carbonate, barium sulfate, titanium oxide or zinc oxide having a refractive index of 1.6 or more is used. Is particularly preferred.
In addition, titanium oxide has a significantly higher refractive index than other inorganic fillers and can significantly increase the difference in refractive index from the base resin, so it is less blended than when other fillers are used. Excellent reflectivity can be obtained in an amount. Furthermore, by using titanium oxide, high light reflectivity can be obtained even if the thickness of the reflector is reduced.
Therefore, it is more preferable to use a filler containing at least titanium oxide. In this case, the amount of titanium oxide is 30% or more of the total mass of the inorganic filler, or a combination of an organic filler and an inorganic filler. In such a case, the total mass is preferably 30% or more.

  The titanium oxide used in the present invention is preferably a crystalline titanium oxide such as anatase type or rutile type, and among them, a titanium oxide having a refractive index of 2.7 or more from the viewpoint of a large difference in refractive index from the base resin. Is preferred. In this respect, rutile type titanium oxide is preferable.

  Further, it is particularly preferable to use high-purity titanium oxide having high purity among titanium oxides. Here, the high-purity titanium oxide means titanium oxide having a small light absorption ability with respect to visible light, that is, titanium oxide having a small content of coloring elements such as vanadium, iron, niobium, copper, and manganese.

  Examples of high-purity titanium oxide include those produced by a chlorine process. In the chlorine method process, rutile ore containing titanium oxide as a main component is reacted with chlorine gas in a high-temperature furnace of about 1000 ° C. to produce titanium tetrachloride first, and then this titanium tetrachloride is burned with oxygen, High purity titanium oxide can be obtained. There is a sulfuric acid process as an industrial method for producing titanium oxide, but the titanium oxide obtained by this method contains a large amount of colored elements such as vanadium, iron, copper, manganese, niobium, etc. Absorption capacity increases. Therefore, it is difficult to obtain high-purity titanium oxide by the sulfuric acid method process.

  In addition, in order to improve the dispersibility of the inorganic fine powder in the base resin, the surface of the fine powder filler is subjected to a surface treatment with a silicon compound, a polyhydric alcohol compound, an amine compound, a fatty acid, a fatty acid ester, or the like. You may use what you did.

  On the other hand, examples of the organic fine powder include polymer beads and polymer hollow particles, which can be used alone or in combination of two or more. Moreover, you may use combining inorganic fine powder and organic fine powder.

  The fine powder filler preferably has a particle size of 0.05 μm or more and 15 μm or less, more preferably 0.1 μm or more and 10 μm or less. If the particle size of the filler is 0.05 μm or more, the dispersibility in the base resin does not decrease, and a homogeneous sheet can be obtained. If the particle size is 15 μm or less, the interface between the base resin and the fine powder filler is densely formed, and a highly reflective reflector is obtained.

  The amount of fine powder filler is preferably 10 to 80% by mass with respect to the total mass of the resin layer A in consideration of the light reflectivity, mechanical strength, productivity, and the like of the reflective material. More preferably, it is -70 mass%. If the content of the fine powder filler is 10% by mass or more, the area of the interface between the base resin and the fine powder filler can be sufficiently secured, and high reflectivity can be imparted to the reflector. When the content of the fine powder filler is 80% by mass or less, the mechanical strength necessary for the reflector can be ensured.

  In the resin layer B, the content ratio of the base resin and the fine powder filler is, from the viewpoint of light reflectivity, mechanical strength, productivity, and the like, base resin: fine powder filler = 80: 20 to 30:70, particularly 80:20 to 40:60 is preferable.

(Other ingredients)
The resin layer B may contain other resins as long as the effects of the base resin and the fine powder filler described above are not impaired. Moreover, you may contain antioxidant, a light stabilizer, a heat stabilizer, a dispersing agent, a ultraviolet absorber, a fluorescent whitening agent, a compatibilizing agent, a lubricant, and other additives.

(Form of resin layer B)
The resin layer B may be a layer made of a sheet body, or may be a layer formed by forming a thin film of the molten resin composition by extrusion or coating (without forming a sheet). In the case of a sheet body, the sheet body may be an unstretched film, a uniaxial or biaxially stretched film, but a stretched film obtained by stretching at least 1.1 times in a uniaxial direction, particularly two An axially stretched film is preferred.

(Porosity of resin layer B)
The resin layer B preferably has fine voids in the range of 20% to 80% from the viewpoint of ensuring reflection performance. In other words, the porosity of the resin layer A, that is, the volume ratio of the voids in the resin layer A is preferably 20% or more and 80% or less, particularly 25% or more and 75% or less, especially 30% or more, 70 % Or less is preferable.

In addition, when both the resin layer A and the resin layer B contain an olefin resin, the olefin resin of the resin layer B is the same as the olefin resin of the resin layer A from the viewpoint of improving the adhesion between the resin layers A and B. It is preferable to contain an olefin resin containing the same monomer unit.
For example, when the base resin of the resin layer B is a polypropylene resin, the resin layer A preferably contains a polypropylene resin as the olefin resin.

  Further, when the resin layer A contains a thermoplastic elastomer, especially when it contains a styrene elastomer, the resin layer A and the resin layer are compatible with not only a styrene resin but also an olefin resin, particularly a polypropylene resin. From the viewpoint of improving adhesiveness with B, it is preferable.

(Laminated structure)
As described above, the reflective material may have a laminated structure in which the resin layer A and the resin layer B are provided. However, the laminated structure is not limited thereto, and in addition, for example, A three-layer structure in which the resin layer A is provided on both surfaces of the resin layer B can be given. Furthermore, in addition to the resin layer A and the resin layer B, other layers may be provided, or other layers may be interposed between the resin layers A and B. For example, an adhesive layer may be interposed between the resin layer A and the resin layer B.

(Thickness)
The thickness of the reflective material is not particularly limited, and is preferably, for example, 30 μm to 1500 μm, and particularly preferably about 50 μm to 1000 μm in consideration of handleability in practical use.
For example, the thickness of the reflective material for liquid crystal display is preferably 50 μm to 700 μm. For example, the thickness of the reflective material for lighting fixtures and lighting signboards is preferably 100 μm to 1000 μm.

  As can be seen from the results of Examples described later, even if the resin layer A is thin, the heat resistance of the entire reflecting material can be increased. On the other hand, if the resin layer A is too thick, the bending resistance is lowered. From such a viewpoint, the total thickness ratio of the resin layer A and the resin layer B (for example, when there are two resin layers A), the ratio of the total thickness of the two layers is 1: 2 to 1:15. Is more preferable, and 1: 2 to 1:10 is particularly preferable.

(Reflectance)
This reflective material can make 97% or more of the average reflectance of at least one side with respect to light having a wavelength of 420 nm to 700 nm. If it has such a reflection performance, it exhibits good reflection characteristics as a reflective material, and a liquid crystal display or the like incorporating this reflective material can achieve a sufficient brightness of the screen.

(Porosity)
The reflective material preferably includes a layer having voids in order to improve reflection performance, and the porosity of the layer, that is, the volume ratio of the voids to the layer is 10% or more, 90% or less, particularly It is preferably 20% or more and 80% or less. By providing the gap in such a range, the whitening of the reflective material proceeds sufficiently, so that high light reflectivity can be achieved, and the mechanical strength of the reflective material is reduced and does not break. .

The layer having voids as described above may be either one of the resin layers A and B, or both, or other layers.
However, in the two-layer or three-layer configuration composed of the resin layers A and B, it is preferable to provide the above-described voids only in the resin layer B. By providing the air gap only in the resin layer B, the reflectance can be increased without reducing the mechanical strength of the reflective material as compared with the reflective material having the air gap in the resin layer A.

In addition, the porosity of this reflective material can be calculated | required by the following formula in the case of forming a space | gap by extending | stretching.
Porosity (%) = {(density of film before stretching−density of film after stretching) / density of film before stretching} × 100

(Production method)
The method for producing the reflective material is not particularly limited, and a known method can be adopted. Below, although an example is given and demonstrated about the manufacturing method of the reflecting material provided with the laminated structure, it is not limited to the following manufacturing method at all.

  First, a resin composition A in which an olefin resin and / or a thermoplastic elastomer and other additives are blended with a styrene copolymer as necessary is prepared. Specifically, an olefin resin and / or a thermoplastic elastomer, other antioxidants, and the like are added to a styrene copolymer as necessary, and mixed with a ribbon blender, tumbler, Henschel mixer, etc., and then a Banbury mixer. The resin composition A can be obtained by kneading at a temperature equal to or higher than the melting point of the resin (for example, 200 ° C. to 280 ° C.) using a single or twin screw extruder. Alternatively, the resin composition A can be obtained by adding a predetermined amount of a styrene copolymer, an olefin resin and / or a thermoplastic elastomer or the like with a separate feeder or the like. Also, a so-called master batch in which an olefin resin and / or a thermoplastic elastomer and other antioxidants are blended at a high concentration in advance is prepared, and this master batch and a styrene copolymer, an olefin resin and / or A resin composition A having a desired concentration can be prepared by mixing with a thermoplastic elastomer.

  On the other hand, the resin composition B which mix | blended the fine powder filler, the other additive, etc. with the olefin resin etc. as needed is produced. Specifically, a fine powder filler or the like is added to the olefin resin as a main component and mixed with a ribbon blender, tumbler, Henschel mixer, etc., and then a Banbury mixer, a single screw or twin screw extruder is used. Thus, the resin composition B can be obtained by kneading at a temperature equal to or higher than the melting point of the resin (for example, 190 ° C. to 270 ° C.). Alternatively, the resin composition A can be obtained by adding a predetermined amount of an olefin resin, a fine powder filler, or the like with a separate feeder or the like. Also, a resin composition having a desired concentration is prepared by preparing a so-called master batch in which a fine powder filler, other additives, etc. are blended in high concentration with an olefin resin in advance, and mixing this master batch with the olefin resin. B can also be used.

Next, after drying the resin compositions A and B thus obtained, they are supplied to different extruders, respectively, heated to a predetermined temperature or higher and melted.
Conditions such as the extrusion temperature need to be set in consideration of a decrease in molecular weight due to decomposition. For example, the extrusion temperature of the resin composition A is 200 ° C. to 280 ° C. The extrusion temperature is preferably 190 ° C to 270 ° C.
Thereafter, the melted resin composition A and resin composition B are merged into a T-die for two types and three layers, extruded from a slit-like discharge port of the T-die in a laminated shape, and solidified to a cooling roll to form a cast sheet. Form.

The obtained cast sheet is preferably stretched at least in the uniaxial direction. By extending | stretching, the interface of the olefin resin in the resin layer B and a fine powder filler peels, a space | gap is formed, whitening of a sheet | seat advances, and the light reflectivity of a film can be improved. Furthermore, the cast sheet is particularly preferably stretched in the biaxial direction. By only uniaxially stretching, the formed void has only a fibrous form extending in one direction, but by biaxially stretching, the void is elongated in both the vertical and horizontal directions and becomes a disk-shaped form.
That is, by biaxially stretching, the peeling area at the interface between the olefin resin and the fine filler in the resin layer B is increased, and the whitening of the sheet further proceeds. As a result, the light reflectivity of the film is further increased. Can be increased. Moreover, since biaxial stretching reduces the anisotropy of the shrinkage direction of the film, the heat resistance of the film can be improved, and the mechanical strength of the film can be increased.

The stretching temperature at which the cast sheet is stretched is preferably a temperature within the range of not less than the glass transition temperature (Tg) of the styrene copolymer of the resin layer A and not more than (Tg + 50 ° C.).
When the stretching temperature is equal to or higher than the glass transition temperature (Tg), the film can be stably formed without breaking during stretching. Further, when the stretching temperature is a temperature of (Tg + 50) ° C. or less, the stretching orientation becomes high, and as a result, the porosity becomes large, so that a film having a high reflectance is easily obtained.

  The order of biaxial stretching is not particularly limited, and for example, simultaneous biaxial stretching or sequential stretching may be used. After melt film formation using a stretching facility, the film may be stretched to MD by roll stretching, and then stretched to TD by tenter stretching, or biaxial stretching may be performed by tubular stretching or the like. In the case of biaxial stretching, the stretching magnification is preferably 6 times or more as the area magnification. By stretching the area magnification by 6 times or more, the porosity of the entire reflection film composed of the resin layer A and the resin layer B may be 40% or more.

  After stretching, it is preferable to perform heat setting in order to impart dimensional stability (morphological stability of voids) to the reflective film. It is preferable that the processing temperature for heat-setting a film is 110-170 degreeC. The processing time required for heat setting is preferably 1 second to 3 minutes. Moreover, although there is no limitation in particular about extending | stretching equipment etc., it is preferable to perform the tenter extending | stretching which can perform a heat setting process after extending | stretching.

(Use)
The reflective material can be used as a reflective material as it is, but it can also be used as a structure in which the reflective material is laminated on a metal plate or a resin plate, for example, a liquid crystal display such as a liquid crystal display. It is useful as a reflector used in devices, lighting fixtures, lighting signs, and the like.

  In this case, examples of the metal plate on which the reflective material is laminated include an aluminum plate, a stainless plate, and a galvanized steel plate.

  Examples of the method of laminating the reflective material on a metal plate or resin plate include a method using an adhesive, a method of heat-sealing without using an adhesive, a method of bonding via an adhesive sheet, and extrusion coating. And the like. However, it is not limited to these methods.

More specifically, an adhesive such as polyester, polyurethane, or epoxy is applied to the surface of the metal plate or resin plate (collectively referred to as “metal plate, etc.”) to which the reflective material is to be bonded. Can be pasted together.
In such a method, a commonly used coating facility such as a reverse roll coater or a kiss roll coater is used, and the adhesive film thickness after drying is about 2 μm to 4 μm on the surface of a metal plate or the like on which a reflective material is bonded. Apply an adhesive so that
Next, the coated surface is dried and heated with an infrared heater and a hot air heating furnace, and while maintaining the surface of the metal plate or the like at a predetermined temperature, the reflecting material is immediately coated and cooled using a roll laminator, and reflected. You can get a board.

The reflective material is useful as a reflective member for use in a liquid crystal display device such as a liquid crystal display, a lighting fixture, and a lighting signboard.
In general, a liquid crystal display includes a liquid crystal panel, a polarizing reflection sheet, a diffusion sheet, a light guide plate, a reflection sheet, a light source, a light source reflector, and the like.
This reflector can also be used as a reflector that plays a role of making light from a light source efficiently enter a liquid crystal panel or a light guide plate, or condenses light emitted from a light source disposed at an edge portion to guide the light guide plate. It can also be used as a light source reflector having a role of being incident on the light source.

(Explanation of terms)
In general, "film" refers to a thin flat product that is extremely small compared to its length and width and whose maximum thickness is arbitrarily limited, and is usually supplied in the form of a roll (Japan) Industrial standard JISK6900), and in general, “sheet” refers to a product that is thin by definition in JIS and generally has a thickness that is small instead of length and width. However, since the boundary between the sheet and the film is not clear and it is not necessary to distinguish the two in terms of the present invention, in the present invention, even when the term “film” is used, the term “sheet” is included and the term “sheet” is used. In some cases, “film” is included.

  In addition, the expression “main component” in the present specification includes the meaning of allowing other components to be contained within a range that does not hinder the function of the main component unless otherwise specified. At this time, although the content ratio of the main component is not specified, the main component (when two or more components are main components, the total amount thereof) is 50% by mass or more, preferably 70% in the composition. It occupies at least 90% by mass, particularly preferably at least 90% by mass (including 100%).

In the present invention, when expressed as “X to Y” (X and Y are arbitrary numbers), “X is preferably greater than X” and “preferably Y”, with the meaning of “X to Y” unless otherwise specified. It means “smaller”.
Further, in the present invention, when expressed as “X or more” (X is an arbitrary number), it means “preferably larger than X” unless otherwise specified, and “Y or less” (Y is an arbitrary number). ) Includes the meaning of “preferably smaller than Y” unless otherwise specified.

  The present invention will be described more specifically with reference to the following examples. However, the present invention is not limited to these examples, and various applications are possible without departing from the technical idea of the present invention.

(Measurement and evaluation method)
First, measurement methods and evaluation methods for various physical property values of samples obtained in Examples and Comparative Examples will be described. Hereinafter, the film take-up (flow) direction is indicated as MD, and its orthogonal direction is indicated as TD.

(Porosity)
Measure the density of the film before stretching (denoted as “unstretched film density”) and the density of the film after stretching (denoted as “stretched film density”), and substitute for the following formula to determine the porosity of the film ( %).
Porosity (%) = {(Unstretched film density−Stretched film density) / Unstretched film density} × 100

(Average reflectance)
An integrating sphere was attached to a spectrophotometer ("U-3900H", manufactured by Hitachi, Ltd.), and the reflectance when the alumina white plate was 100% was measured at intervals of 0.5 nm over a wavelength of 420 nm to 700 nm. The average value of the measured values obtained was calculated, and this value was defined as the average reflectance (%).

(Heat-resistant)
A reflective material (sample) is pasted on the SUS plate imitating the structure of the backlight unit of a 20-inch TV (see Fig. 1) so that there is no gap between the SUS plate and the reflective material. I put it in. After 3 hours, it was taken out and cooled to room temperature. Thereafter, the distance between the SUS plate and the reflective material (how many mm the reflective material is waved with respect to the SUS plate) was measured.

The heat resistance was evaluated in light of the following evaluation criteria for the distance between the SUS plate and the reflective material. However, the symbols “◯” and “Δ” are above the practical level.
Evaluation criteria:
“◯”: Distance is less than 1 mm “Δ”: Distance is less than 2 mm “X”: Distance is 2 mm or more

(rigidity)
In accordance with JIS P-8125, the bending stiffness (g · cm) was measured under the following conditions, and the bending rigidity (kgf / cm ² ) of the sheet was determined by substituting it into the following formula.
・ Measuring device: Taber V-5 bending stiffness tester 150-B type (Taber)
・ Bending angle: 15 degrees ・ Bending rigidity = 2 × 0.01 / (sample thickness) ³ × bending stiffness

Rigidity was evaluated in light of the bending rigidity ratio described below. However, the symbols “◯” and “Δ” are above the practical level.
Evaluation criteria:
“◯”: Bending rigidity is 15,000 (kgf / cm ² ) or more “Δ”: Bending rigidity is 12,000 (kgf / cm ² ) or more “×”: Bending rigidity is 12,000 (kgf / kg) cm ² )

(Preparation of resin composition A-1)
Styrene copolymer (manufactured by PS Japan, trade name “G9001”, styrene-methacrylic acid copolymer, density (ISO1183): 1.06 cm ³ , glass transition temperature Tg (JISK-7121): 125 ° C.), MFR (230 ° C., 21.18N, JISK-7210): 3.9 g / 10 min) and polypropylene resin (manufactured by Nippon Polypro Co., Ltd., trade name “Novatech PP EA9”, density (JISK-7112): 0.9 cm ³ , pellets of MFR (230 ° C., 21.18N, JISK-7210): 0.5 g / 10 min) were mixed at a mass ratio of 75:25, and then, using a twin screw extruder heated to 220 ° C. It pelletized and produced resin composition A-1.

(Preparation of resin composition B-1)
Polypropylene resin (Nippon Polypro Co., Ltd., trade name “NOVATEC PP FY6HA”, density (JISK-7112): 0.9 g / cm ³ , MFR (230 ° C., 21.18 N, JISK-7210): 2.4 g / 10 min ) Pellets and titanium oxide (trade name “KRONOS 2230” manufactured by KRONOS, density 4.2 g / cm ³ , rutile titanium oxide, Al, Si surface treatment, TiO ₂ content 96.0%, manufacturing method: chlorine After mixing at a mass ratio of 50:50, the mixture was pelletized using a twin screw extruder heated at 270 ° C. to prepare a resin composition B-1.

(Production of reflective material)
The resin compositions A-1 and B-1 were respectively supplied to extruders A and B heated to 210 ° C. and 200 ° C., and then melt-kneaded at 210 ° C. and 200 ° C. The sheet was joined to a three-layer T die, extruded into a sheet shape so as to have a three-layer structure of resin layer A-1, resin layer B-1, and resin layer A-1, and cooled and solidified to form a laminated sheet.
The obtained laminated sheet was roll-rolled twice in MD at a temperature of 145 ° C., and then biaxially stretched by stretching ten-fold in TD at 135 ° C. to obtain a thickness of 350 μm (resin layer A-1: 50 μm). , Resin layer B-1: 250 μm A reflection material having a lamination ratio A-1: B-1 = 1: 2.5) was obtained. The stretchability (workability) was good and no breakage occurred.
The obtained reflecting material was evaluated for porosity, average reflectance, and heat resistance. In addition, regarding the porosity, it evaluated about resin layer B-1. That is, the resin composition B-1 was supplied to the extruder B, and a single layer film (thickness 250 μm) of only the resin layer B-1 was obtained and evaluated according to the above operation.

(Preparation of resin composition A-2)
Styrene copolymer (manufactured by PS Japan, trade name “G9001”), polypropylene resin (manufactured by Nippon Polypro, trade name “Novatech PP EA9”), and styrene elastomer (manufactured by Asahi Kasei Corporation, Product name “Tuftec P2000”, styrene-butadiene-butylene-styrene copolymer, MFR (230 ° C., 21.18N, JISK-7210): 35 g / 10 min)) in a mass ratio of 81: 9: 10 After mixing, the mixture was pelletized using a twin screw extruder heated to 220 ° C. to prepare Resin Composition A-2.

(Preparation of resin composition B-2)
After mixing the pellets of polypropylene resin (trade name “NOVATEC PP FY6HA” manufactured by Nippon Polypro Co., Ltd.) and titanium oxide (trade name “KRONOS 2230” manufactured by KRONOS Co., Ltd.) at a mass ratio of 60:40, 270 ° C. The resin composition B-2 was produced by pelletizing using a twin-screw extruder heated in step 1.

(Production of reflective material)
The resin compositions A-2 and B-2 were respectively supplied to extruders A and B heated to 210 ° C. and 200 ° C., and then melt-kneaded at 210 ° C. and 200 ° C. in the respective extruders. The sheet was joined to a three-layer T die, extruded into a sheet shape so as to have a three-layer structure of resin layer A-2 / resin layer B-2 / resin layer A-2, and cooled and solidified to form a laminated sheet.
The obtained laminated sheet was roll-stretched 2.8 times to MD at a temperature of 145 ° C., and then biaxially stretched by stretching tenter to TD at 140 ° C. to obtain a thickness of 250 μm (resin layer A-2 : 35 [mu] m, resin layer B-2: 180 [mu] m, a reflective material having a lamination ratio A-2: B-2 = 1: 2.5) was obtained. The stretchability (workability) was good and no breakage occurred. The obtained reflector was evaluated in the same manner as in Example 1.

  In the production of the resin composition A-2 of Example 2, instead of using pellets of a styrene elastomer (manufactured by Asahi Kasei Co., Ltd., trade name “Tuftec P2000”), a soft polypropylene resin (manufactured by Dow Chemical Company, trade name “ VERSIFY 2400-05 ”, MFR (230 ° C., 21.18N, JISK-7210): 1.9 g / 10 min)), and the obtained laminated sheet was converted to MD at a temperature of 145 ° C. A reflector similar to that of Example 2 was obtained except that biaxial stretching was performed by stretching the film 8 times and then stretching the film tentally to TD at 140 ° C. 3 times. The stretchability (workability) was good and no breakage occurred. Evaluation similar to Example 1 was performed about the obtained reflecting material.

(Comparative Example 1)
(Preparation of resin composition B-3)
A pellet of polypropylene resin (trade name “Novatech PP FY6HA” manufactured by Nippon Polypro Co., Ltd.) and titanium oxide (trade name “KRONOS 2230” manufactured by KRONOS Co., Ltd.) are mixed at a mass ratio of 50:50, and then 270 ° C. The resin composition B-3 was produced by pelletizing using a twin-screw extruder heated in step 1.

(Production of reflective material)
The resin composition B-3 was supplied to an extruder heated to 200 ° C., melt-kneaded at 200 ° C. in the extruder, then extruded into a sheet form from a T-die, and cooled and solidified to form a sheet. The obtained sheet was roll-stretched twice to MD at a temperature of 130 ° C., and then biaxially stretched by stretching the tenter to TD at 130 ° C. to obtain a reflector having a thickness of 200 μm. Evaluation similar to Example 1 was performed about the obtained reflecting material.

(Comparative Example 2)
(Preparation of resin composition A-4)
Amorphous cycloolefin resin (trade name “TOPAS8007”, manufactured by Polyplastics Co., Ltd., addition copolymer of ethylene and norbornene, density (ISO1183): 1.02 g / cm ³ , MFR (230 ° C., 21.18 N) , JISK-7210): 10 g / 10 min) pellets and polypropylene resin pellets (trade name “Novatech PP EA9” manufactured by Nippon Polypro Co., Ltd.) are mixed at a mass ratio of 75:25, and then heated to 230 ° C. The resin composition A-4 was produced by pelletizing using the twin screw extruder.

(Preparation of resin composition B-4)
After mixing the pellets of polypropylene resin (trade name “NOVATEC PP FY6HA” manufactured by Nippon Polypro Co., Ltd.) and titanium oxide (trade name “KRONOS 2230” manufactured by KRONOS Co., Ltd.) at a mass ratio of 60:40, 270 ° C. The resin composition B-4 was produced by pelletizing using a twin-screw extruder heated in step 1.

(Production of reflective material)
The resin compositions A-4 and B-4 were respectively supplied to extruders A and B heated to 230 ° C. and 200 ° C., and then melt-kneaded at 230 ° C. and 200 ° C. The sheet was joined to a three-layer T die, extruded into a sheet shape so as to have a three-layer structure of resin layer A-4 / resin layer B-4 / resin layer A-4, and cooled and solidified to form a laminated sheet.
The obtained laminated sheet was roll-stretched 2.8 times to MD at a temperature of 0 ° C., and then biaxially stretched by stretching ten times to TD at 140 ° C. to obtain a thickness of 250 μm (resin layer A-4: A reflective material having a thickness of 35 μm and a resin layer B-4: 180 μm (lamination ratio A-4: B-4 = 1: 2.5) was obtained. The obtained reflector was evaluated in the same manner as in Example 1.

As is apparent from Table 1, the reflectors of Examples 1 to 3 and Comparative Examples 1 and 2 have a high light reflectivity with a reflectance of 97% or more with respect to light having a wavelength of 420 nm to 700 nm. I understood. In addition, the reflectors of Examples 1 to 3 and Comparative Example 2 have a rigidity of 12,000 (kgf / cm ² ) or more and satisfy a practical level, whereas the reflector of Comparative Example 1 It was found that the rigidity was inferior to the practical level.
Further, the reflectors of Examples 1 to 3 did not cause undulation even after the wave test, and the reflectors of Examples 1 and 2 had a sheet lift of less than 1 mm with respect to the SUS surface. It was found that the film was almost flat at less than 1.5 mm and had good heat resistance.
On the other hand, the reflective material of Comparative Examples 1 and 2 generated a large wave of 2 mm or more after the wave test, and was found to be inferior to the reflective materials of Examples 1 to 3 in terms of heat resistance.
From the above, it was found that the reflective materials of Examples 1 to 3 had high light reflectivity, good rigidity, and good heat resistance.

Claims (8)

  From the group consisting of styrene-α-methylstyrene copolymer (SAMS), styrene-acrylic acid copolymer (SAA), styrene-methacrylic acid copolymer (SMAA) and styrene-maleic anhydride copolymer (SMA). A reflective material comprising a resin layer A containing one or more selected styrenic copolymers.   2. The reflector according to claim 1, wherein the resin layer A contains an olefin resin and / or a thermoplastic elastomer in addition to the styrene copolymer.   The reflective material according to claim 2, wherein the thermoplastic elastomer is a styrene-based elastomer.   It has the laminated structure which provided the resin layer A as described in any one of Claims 1-3 in the at least single side | surface of the resin layer B containing other resin and fine powder fillers other than a styrene resin at least. Characteristic reflector.   The reflective material according to claim 4, wherein the resin layer A is located on an outermost layer that is a reflective use surface of the reflective material.   6. The reflector according to claim 4, wherein the total thickness ratio of the resin layer A and the resin layer B is resin layer B: resin layer A = 2: 1 to 15: 1.   A reflector having a configuration in which the reflector according to any one of claims 1 to 6 is laminated on a metal plate or a resin plate.   The reflector according to any one of claims 1 to 6, wherein the reflector is used as a constituent member of a liquid crystal display, a lighting fixture, or a lighting signboard.

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