JP6641627B2 - Reflective film and edge light type backlight unit using the same - Google Patents

Description

  The present invention relates to a reflection film used for a backlight of a liquid crystal display device or the like, and particularly to a reflection film suitable for an edge light type backlight unit.

  The liquid crystal display device generally employs a backlight system in which light is emitted by illuminating a liquid crystal layer from the back. As the backlight system, an edge light type and a direct type are known.

  As a reflective film used for these backlights, a resin layer containing particles (hereinafter, also referred to as a bead layer, a particle-containing layer or a coating layer) is laminated on at least one surface of a white film, and the surface is made of particles. A reflection film having a portion (projection) formed thereon is known.

  For example, in order to improve the brightness of a backlight and to suppress uneven brightness, a resin layer in which the coverage of particles, the number of stacked particles, the height of protrusions, the number of protruding particles, and the like have been proposed (for example, Patent Document 1). 4).

  Further, in order to suppress the sticking of the light guide plate and the reflective film constituting the edge light type backlight unit, or to suppress the light guide plate from being scratched by the contact between the light guide plate and the reflective film, It has been proposed that particles are contained in a resin layer to form protrusions (projections) by the particles on the surface of the resin layer (for example, Patent Documents 5 to 9).

JP 2010-85843 A JP 2010-44321 A JP 2010-44238 A JP 2013-210639 A JP 2003-92018 A JP-T-2008-512719 International Publication No. 2011/105294 JP 2012-108190 A JP 2012-159610 A

  The above-mentioned patent documents disclose many kinds of particles as particles contained in the resin layer. Among these particles, polyethylene particles are also exemplified. The melting point of conventionally known polyethylene particles is generally about 100 to 110 ° C.

  The present inventors have noticed that polyethylene particles have relatively low hardness and relatively little deterioration (discoloration or the like) due to heat, and have started the development of a reflective film utilizing these characteristics.

  However, when polyethylene particles, which are generally known in the art, are contained in the resin layer, melting or deformation is likely to occur in a high temperature environment during processing or use of the product, and as a result, a member ( (E.g., light guide plate).

  It is also known that polyethylene particles have relatively good slipperiness. However, in the case where a conventionally known polyethylene particle is contained in a resin layer to form a projection (projection) on the surface of a reflective film, slipperiness due to contact with a light guide plate is not sufficiently exhibited. As a result, it has been found that there is a problem that a part of the polyethylene particles shaved by the contact with the light guide plate adheres to the light guide plate and contaminates the light guide plate.

  Therefore, an object of the present invention is to make use of the characteristics of polyethylene particles (the characteristics of relatively low hardness and relatively little deterioration (discoloration) due to heat) to adhere to a member (for example, a light guide plate) that comes into contact with the reflective film. At the same time, damage (scratch scratches and contamination) of the contact member (eg, light guide plate) and contamination of the contact member (eg, light guide plate) due to heat can be suppressed, and heat resistance (discoloration due to heat is small). ) Is to provide a good reflective film.

The above object of the present invention has been basically achieved by the following inventions.
[1] A reflective film having a resin layer containing polyethylene particles having a viscosity average molecular weight of 10,000 or more and a melting point of 115 ° C. or more on at least one surface of a base film.
[2] The reflection film according to [1], wherein the density of the polyethylene particles is 942 kg / m ³ or more.
[3] The reflective film according to [1], wherein the polyethylene particles have a viscosity average molecular weight of 700,000 or more.
[4] The reflective film according to any one of [1] to [3], wherein a dynamic friction coefficient between an acrylic plate and a surface of at least one surface of the reflective film having the resin layer is 0.6 or less.
[5] The reflective film according to any one of [1] to [4], wherein the content of the polyethylene particles in the resin layer is 3 to 75% by mass based on 100% by mass of the total amount of the resin layer.
[6] The reflective film according to any one of [1] to [5], wherein the base film is a film having bubbles therein at least.
[7] The film according to any one of [1] to [6], wherein the base film is a film in which a film layer (layer A) is laminated on both sides of a film layer (layer B) containing bubbles therein. Reflective film.
[8] An edge light type backlight unit, wherein the reflective film according to any one of [1] to [7] is arranged so that the surface on the side having the resin layer faces the light guide plate.

  Advantageous Effects of Invention According to the present invention, it is possible to suppress sticking to a member (hereinafter, also referred to as a contact member, for example, a light guide plate) that comes into contact with the reflective film, and at the same time, to damage the contact member (for example, the light guide plate) It is possible to provide a reflection film that can suppress contamination of a contact member (for example, a light guide plate) due to heat and heat, and has good heat resistance (small discoloration due to heat).

  In the present invention, the member (contact member) that comes into contact with the reflective film is not particularly limited, and the contact member can be appropriately selected depending on the use and purpose of use of the reflective film.

  The reflection film of the present invention is particularly suitable for an edge light type backlight unit, and such a backlight unit is arranged in a state where the reflection film and the light guide plate are in contact with each other. The effect of the present invention will be described below.

  White spot unevenness (a phenomenon that a bright spot is visible in a spot) may occur due to sticking of the reflective film and the light guide plate. However, the sticking of the light guide plate by using the reflective film of the present invention may occur. Adherence is suppressed, and as a result, occurrence of white spot unevenness is suppressed.

  The light guide plate may be damaged by the contact between the reflection film and the light guide plate. However, the use of the reflection film of the present invention suppresses the damage of the light guide plate. Here, the damage of the light guide plate means, for example, that the light guide plate is scratched or that particles in the resin layer of the reflection film are shaved and transferred to the light guide plate to contaminate the light guide plate.

  In addition, the backlight unit of the liquid crystal display device may be heated to a high temperature by turning on the liquid crystal display device. When the conventional polyethylene particles are used as the particles to be contained in the resin layer, the polyethylene particles melt and contaminate the light guide plate. However, the contamination of the light guide plate due to such heat is suppressed by using the reflective film of the present invention.

  Further, the reflective film of the present invention has good heat resistance (discoloration due to heat) by using polyethylene particles having a viscosity average molecular weight of 10,000 or more and a melting point of 115 ° C. or more.

It is the image of the surface photograph by the scanning electron microscope of the resin layer surface which shows an example of the reflection film which concerns on this invention. It is a schematic cross section of the resin layer part of the reflective film which concerns on one Embodiment of this invention. It is a schematic cross section of the resin layer part of the reflective film which concerns on another embodiment of this invention.

Hereinafter, the present invention will be described in detail with embodiments.
The reflective film of the present invention is characterized in that at least one surface of the base film has a resin layer containing polyethylene particles having a viscosity average molecular weight of 10,000 or more and a melting point of 115 ° C. or more. Hereinafter, polyethylene particles having a viscosity average molecular weight of 10,000 or more and a melting point of 115 ° C. or more may be referred to as polyethylene particles according to the present invention.

  Further, in the reflective film of the present invention, it is preferable that a convex portion made of the polyethylene particles is formed on the surface of the resin layer.

  Providing the above-mentioned protrusions on the surface of the resin layer is preferable because sticking of the reflection film and the light guide plate is suppressed, and as a result, white spot unevenness is suppressed. In addition, it is preferable to form the convex portion with the polyethylene particles according to the present invention, since damage to the light guide plate (scratch scratches and contamination) and contamination of the light guide plate due to heat are suppressed. Use of the polyethylene particles according to the present invention is preferable because heat resistance (discoloration due to heat) is improved.

  Here, whether or not the protrusions due to the particles are formed on the surface of the resin layer can be confirmed, for example, by observing the surface of the resin layer with a scanning electron microscope (SEM) at a magnification of 500 times. In this case, the projections can be more clearly confirmed by observing the observation angle at an oblique angle of 30 degrees with respect to the resin layer surface.

  FIG. 1 is an image of a surface photograph by a scanning electron microscope of the surface of a resin layer as an example of the reflection film according to the present invention. It can be clearly confirmed that the projections due to the particles are present on the surface of the resin layer of the reflection film 100.

  2 and 3 are schematic cross-sectional views showing examples of the resin layer portion of the reflection film according to the present invention. 2, reference numeral 1 denotes a resin film, reference numeral 2 denotes particles (polyethylene particles having a viscosity average molecular weight of 10,000 or more and a melting point of 115 ° C. or higher), reference numeral 3 denotes a resin layer containing particles 2, Reference numeral 4 indicates a base film.

  The protrusions of the resin layer surface due to the particles may be formed such that only a part of the particles protrude from the surface (FIG. 2A), or more than half of the particles may protrude from the surface (FIG. 2B). ). The protrusion may be formed of individual particles as shown in FIGS. 2A and 2B, or the protrusion may be formed in a state where a plurality of particles are aggregated or aggregated (FIG. 2C).

  Further, the particles may be arranged on the surface of the resin layer in a planar manner with almost no gaps to form a convex portion (FIG. 3A), or a plurality of particles may be convexly overlapped in the thickness direction of the resin layer. A part may be formed (FIG. 3B).

  Although not shown in FIGS. 2 and 3, it is preferable that part or all of the convex region is covered with a resin (binder) contained in the resin layer. This is preferable because dropping of particles is effectively suppressed.

[Polyethylene particles having a viscosity average molecular weight of 10,000 or more and a melting point of 115 ° C or more]
The polyethylene particles according to the present invention include particles composed of a homopolymer of ethylene and / or particles composed of a copolymer containing ethylene as a main component, and among these particles, the viscosity average molecular weight is 10,000 or more. Particles having a melting point of 115 ° C. or higher are selected.

  The melting point of the polyethylene particles according to the present invention is preferably 120 ° C. or higher, more preferably 125 ° C. or higher, and 128 ° C. from the viewpoints of suppressing sticking between the reflective film and the light guide plate and suppressing damage to the light guide plate and heat contamination. The above is particularly preferred.

  On the other hand, since the transparency tends to decrease and the hardness tends to increase as the melting point of the polyethylene particles increases, the upper limit of the melting point of the polyethylene particles increases the viewpoint of securing the transparency of the particles and the hardness of the particles. From the viewpoint of suppressing the damage of the light guide plate by making it relatively small, the temperature is preferably 175 ° C or lower, more preferably 170 ° C or lower, and particularly preferably 160 ° C or lower.

  The viscosity average molecular weight of the polyethylene particles according to the present invention is preferably 50,000 or more, and more preferably 100,000 or more, from the viewpoint of suppressing sticking of the reflective film and the light guide plate and suppressing damage and heat contamination of the light guide plate. More preferably, it is particularly preferably at least 150,000.

  As described above, the polyethylene particles according to the present invention include particles made of a copolymer containing ethylene as a main component, and the copolymer containing ethylene as a main component is the content of ethylene in the copolymer. It means that the ratio is 50% by mass or more. When the content ratio of ethylene in the copolymer is less than 50% by mass, the intrinsic characteristics of polyethylene particles (the characteristics that polyethylene particles have relatively low hardness and relatively little deterioration (such as discoloration) due to heat) are sufficiently obtained. May not be expressed. The content ratio of ethylene in this copolymer is preferably 70% by mass or more, more preferably 80% by mass or more, and preferably 90% by mass or more from the above viewpoint (from the viewpoint of sufficiently exhibiting the original characteristics of the polyethylene particles). Particularly preferred. The upper limit is about 99% by mass. Examples of the copolymer component of the copolymer include α-olefins (eg, propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, 1-decene, 1-dodecene, and 4-methyl-1-pentene). , 3-methyl-1-pentene), cyclic olefins, acrylic acid, methacrylic acid, acrylates, methacrylates, styrene, fluorinated ethylene and the like.

  Among the above copolymer components, α-olefins, cyclic olefins, acrylic acid, methacrylic acid, acrylates, methacrylates, and styrene are preferred, and α-olefins and cyclic olefins are particularly preferred.

  Among the above-mentioned polyethylene particles, particles composed of a homopolymer of ethylene are particularly preferred. The particles made of a homopolymer of ethylene have an appropriate hardness, so that damage to the light guide plate can be effectively suppressed, and the mixing with the resin layer is relatively good, and the coating property of the resin layer is relatively good. There are advantages.

As one preferred embodiment of the polyethylene particles according to the present invention, for example, particles having a viscosity average molecular weight of 10,000 or more and a melting point of 115 ° C. or more are selected from polyethylene particles having a density of 942 kg / m ³ or more. Can be selected and used. Hereinafter, polyethylene particles having a viscosity average molecular weight of 10,000 or more and a density of 942 kg / m ³ or more may be referred to as “high-density polyethylene particles”.

The density of the high density polyethylene particles is more preferably 945 kg / ^{m 3} or more, more preferably 950 kg / ^{m 3} or more. Since the melting point tends to increase as the density of the high-density polyethylene particles increases, it is preferable that the density of the high-density polyethylene particles be high as described above. On the other hand, since the transparency when the density of the high density polyethylene particle is high tends to be more likely and hardness decrease, the density of the upper limit is preferably 980 kg / m ³ or less, 970 kg / m ³ or less is more preferable.

  The high-density polyethylene particles may have a viscosity average molecular weight of 50,000 or more from the viewpoint of improving the slipperiness of the reflective film surface or effectively preventing sticking between the reflective film and the light guide plate. It is more preferably at least 100,000, particularly preferably at least 150,000. The upper limit of the viscosity average molecular weight of the high-density polyethylene particles is not particularly limited, but is suitably less than 700,000.

  Examples of the high-density polyethylene particles include “Flowbeads” (registered trademark) “HE-3040” manufactured by Sumitomo Seika Co., Ltd. and “Sunfine” (registered trademark) TM “LH” manufactured by Asahi Kasei Chemicals Corporation. Series ".

  In another preferred embodiment of the polyethylene particles according to the present invention, for example, particles having a melting point of 115 ° C. or more are selected and used from polyethylene particles having a viscosity average molecular weight of 700,000 or more. it can.

  From the viewpoint of obtaining a higher melting point, the above polyethylene particles having a viscosity average molecular weight of 700,000 or more have a viscosity average molecular weight of preferably 800,000 or more, more preferably 1,000,000 or more, and particularly preferably 1.5 million or more. The upper limit is not particularly limited, but is preferably 20,000,000 or less, more preferably 10,000,000 or less, particularly preferably 7,000,000 or less, and most preferably 5,000,000 or less.

The density of polyethylene particles viscosity average molecular weight of 700,000 or more is not particularly limited, preferably in the range of 925~980kg / ^{m 3,} more preferably in the range of 930~970kg / ^{m 3,} the 935~965kg / ^{m 3} The range is more preferred.

  Examples of polyethylene particles having a melting point of 115 ° C. or more and a viscosity average molecular weight of 700,000 or more include, for example, “Miperone” (registered trademark, trade name) series (manufactured by Mitsui Chemicals, Inc.) and “HIZEX Million” (registered trademark, product) Name) series (Mitsui Chemicals), “Sunfine” (registered trademark, trade name) series (Asahi Kasei Chemicals), “Dyneema” (registered trademark, trade name) series (DSM), “Spectra” ( (Registered trademark, trade name) series (manufactured by Honeywell), "GUR" (registered trademark, trade name) series (manufactured by Chikona), "Hostalen" (registered trademark, trade name) series (manufactured by Hoechst), and the like. .

  It is preferable that the polyethylene particles according to the present invention be contained such that a convex portion due to the polyethylene particles is formed on the surface of the resin layer. In this respect, the average particle size (r: μm) of the polyethylene particles is preferably 5 μm or more, more preferably 10 μm or more, and particularly preferably 15 μm or more. By including polyethylene particles having an average particle diameter of 5 μm or more in the resin layer, moderate protrusions are formed on the surface of the resin layer, and as a result, sticking between the reflection film and the light guide plate is effectively suppressed. This is preferable because the occurrence of white spot unevenness is suppressed.

  The upper limit of the average particle diameter of the polyethylene particles is preferably 100 μm or less, and more preferably 75 μm or less, from the viewpoint of suppressing the falling off of the polyethylene particles and ensuring uniform coatability when applying and forming the resin layer. It is particularly preferably 50 μm or less.

  Polyethylene particles having an average particle diameter of 5 to 100 μm are contained in the resin layer to form appropriate protrusions on the surface of the resin layer. Sticking to the light plate can be effectively suppressed. In addition, the convex portion formed by the polyethylene particles is preferable because the hardness is relatively small, so that the light guide plate can be prevented from being damaged.

  Here, the average particle diameter (r: μm) is a square or a rectangle having the smallest area completely surrounding one particle on a photograph. The length (major axis diameter) is defined as the maximum length of the particles, and a value obtained by averaging the maximum lengths of the number of particles described in the examples.

  The shape of the polyethylene particles according to the present invention is preferably spherical. By forming the protrusions on the resin layer with spherical polyethylene particles, the light guide plate can be further prevented from being damaged. Here, the term “spherical” does not necessarily mean only a true sphere, but means a particle whose cross-sectional shape is surrounded by a curved surface such as a circle, an ellipse, a substantially circular shape, or a substantially elliptical shape. In the cross section, the ratio of the major axis to the minor axis (major axis / minor axis) means 1.4 or less.

  By forming the projections made of the polyethylene particles according to the present invention on the surface of the resin layer, a favorable effect of, for example, improving the slipperiness of the reflective film surface is exhibited. By improving the slipperiness of the reflective film surface, damage (scratch scratches) of the light guide plate caused by contact between the reflective film surface and the light guide plate is suppressed, and the polyethylene particles contained in the resin layer are further scraped off. Is suppressed, so that contamination of the light guide plate is suppressed, which is preferable.

  Conventionally known polyethylene particles (particles having a relatively low melting point) are not included in the resin layer to form a convex portion on the surface of the resin layer. Rather, the slipperiness was found to be inferior. Similarly, when polyethylene wax particles (common polyethylene wax particles have a viscosity-average molecular weight of less than 10,000) are included in the resin layer to form projections on the surface of the resin layer, the reflection film surface It was found that the slipperiness did not improve, but rather the slipperiness was inferior. The reason is presumed that the convex portion formed by the conventional polyethylene particles or polyethylene-based wax particles is compressed and deformed by contact with a contact member (for example, a light guide plate), and the slipperiness is assumed to be reduced. If the slipperiness is poor, the polyethylene particles contained in the resin layer may be scraped off and contaminate the light guide plate.

  The above-mentioned slipperiness of the reflective film surface can be represented by a dynamic friction coefficient between the reflective film surface and the acrylic plate. The dynamic friction coefficient is preferably 0.6 or less, and particularly preferably 0.3 or less. That is, in the reflective film according to the present invention, the dynamic friction coefficient of at least one surface of the reflective film is preferably 0.6 or less, and particularly preferably 0.3 or less. That is, when the resin layer is provided on both surfaces of the base film, the dynamic friction coefficient of the reflective film surface on only one surface may be 0.6 or less (particularly preferably 0.3 or less), The dynamic friction coefficient of the reflective film surface may be 0.6 or less (particularly preferably 0.3 or less).

  In addition, if the surface of the reflective film has good sliding properties, when the backlight vibrates or the light guide plate is thermally deformed, the phenomenon that the reflective film is caught by the light guide plate and the reflective film is not easily deformed is less likely to occur. There is expected.

[Resin layer]
The resin layer according to the present invention is provided on at least one surface of the base film. That is, the resin layer according to the present invention may be provided on only one side of the base film, or may be provided on both sides.

  The resin layer according to the present invention preferably contains the polyethylene particles according to the present invention and a resin (binder). The resin is not particularly limited, but is preferably a resin mainly containing an organic component, such as a polyester resin, a polyurethane resin, an acrylic resin, a methacrylic resin, a polyamide resin, a polyethylene resin, a polypropylene resin, a polyvinyl chloride resin, and a polyvinylidene chloride resin. , A polystyrene resin, a polyvinyl acetate resin, a fluorine resin and the like.

  These resins may be used alone, or two or more copolymers or a mixture thereof may be used. Among them, polyester resin, polyurethane resin, acrylic resin or methacrylic resin are preferably used in view of heat resistance, dispersibility of additives, productivity and glossiness.

  Further, from the viewpoint of improving the light resistance of the resin layer, it is preferable to use a resin containing an ultraviolet absorber (ultraviolet absorbing component) or a light stabilizer (light stabilizing component). Benzotriazole and benzophenone are exemplified as ultraviolet absorbing components contained in these resins, and hindered amine (HALS) is exemplified as a light stabilizing component contained in the resins. Particularly, a resin containing an ultraviolet absorbing component and a light stabilizing component is preferable.

  As such a resin, a resin obtained by copolymerizing a polymerizable monomer containing an ultraviolet absorbing component and an acrylic monomer in a molecule, a resin obtained by copolymerizing a polymerizable monomer containing a light stabilizing component and an acrylic monomer in a molecule, or Resins obtained by copolymerizing a polymerizable monomer containing an ultraviolet absorbing component in the molecule, a polymerizable monomer containing a light stabilizing component in the molecule, and an acrylic monomer are exemplified.

  Examples of the polymerizable monomer containing an ultraviolet absorbing component in the molecule include 2- (2′-hydroxy-5′-methacryloxyethylphenyl) -2H-benzotriazole (for example, a product manufactured by Otsuka Chemical Co., Ltd.) Name "RUVA-93").

  Examples of the polymerizable monomer containing a light stabilizing component in the molecule include, for example, 4-methacryloyloxy-2,2,6,6-tetramethylpiperidine (for example, trade name “ADEKA STAB LA- manufactured by ADEKA Corporation”). 82 ”).

  The method for producing these resins is disclosed in detail in JP-A-2002-90515, and the resin can be produced with reference thereto. These resins are commercially available from Nippon Shokubai Co., Ltd. as "Hals Hybrid" (registered trademark) and can be obtained.

  In order to suppress sticking between the reflective film and the light guide plate, it is preferable to form a moderate amount of convex portion on the surface of the resin layer, and from this viewpoint, the content of the polyethylene particles in the resin layer is the total amount of the resin layer. It is preferably at least 3% by mass, more preferably at least 5% by mass, further preferably at least 7% by mass, particularly preferably at least 10% by mass with respect to 100% by mass. The upper limit of the content is preferably 75% by mass or less, more preferably 60% by mass or less, from the viewpoint of suppressing the falling off of the polyethylene particles and ensuring uniform coatability at the time of forming the resin layer. , 55% by mass or less is particularly preferred. That is, the content of the polyethylene particles in the resin layer is preferably 3 to 75% by mass based on 100% by mass of the total amount of the resin layer.

  The content of the resin (binder) in the resin layer is 100% in terms of the total amount of the resin layer, from the viewpoint of fixing the polyethylene particles to prevent the resin particles from falling off, and from the viewpoint of ensuring uniform coatability when forming the resin layer. It is preferably at least 20% by mass, more preferably at least 25% by mass, and particularly preferably at least 30% by mass with respect to the mass%. The upper limit of the resin content is preferably 90% by mass or less, and more preferably 85% by mass or less with respect to 100% by mass of the total amount of the resin layer, from the viewpoint of forming moderately large protrusions on the resin layer surface in an appropriate amount. More preferably, it is particularly preferably 80% by mass or less.

  It is preferable that the resin layer further contains a crosslinking agent. That is, by forming the resin layer from the composition containing the above-described resin (binder) and the cross-linking agent, a cross-linked structure is formed in the resin layer and the hardness of the resin layer is improved. This is preferable because the effect of suppressing falling off can be improved.

  As such a cross-linking agent, an isocyanate-based, melamine-based, or epoxy-based cross-linking agent is preferable, and among them, an isocyanate-based cross-linking agent is preferable from the viewpoint that a cross-linking reaction can be rapidly performed even at a relatively low temperature.

  The content of the crosslinking agent in the resin layer is preferably in the range of 0.3 to 20% by mass, more preferably in the range of 0.5 to 15% by mass, and more preferably in the range of 1 to 10% by mass based on 100% by mass of the total amount of the resin layer. A range is particularly preferred.

  The reflective film of the present invention may be charged at the time of processing (the reflective film is punched out, formed and incorporated into a backlight) or the like, which may cause a problem that charged dust or dust existing around adheres. . In order to cope with such a problem, it is preferable that the resin layer contains an antistatic agent within a range that does not impair the effects of the present invention.

  Examples of such antistatic agents include organic antistatic agents such as cationic resins and anionic resins, conductive inorganic compounds (eg, tin oxide, antimony-doped tin oxide (ATO), indium oxide, tin-doped indium oxide, and the like). ).

  Various additives can be further added to the resin layer according to the present invention as long as the effects of the present invention are not impaired. Examples of the additive include a fluorescent whitening agent, a heat stabilizer, an oxidation stabilizer, an organic lubricant, a coupling agent, a dye, a pigment, and the like.

  The thickness (d) of the resin layer is not particularly limited, but is preferably in the range of 0.3 to 20 μm, more preferably in the range of 0.5 to 15 μm, and particularly preferably in the range of 1 to 10 μm. Here, the thickness of the resin layer means the thickness of a portion where no convex portion due to particles exists on the resin layer. In other words, it is the thickness of the portion where no protrusions due to particles exist.

  If the thickness of the resin layer is less than 0.3 μm, the polyethylene particles may fall off. On the other hand, if the thickness of the resin layer exceeds 20 μm, the projections of the polyethylene particles may not be formed sufficiently.

  In particular, from the viewpoint of suppressing damage to the light guide plate and suppressing sticking between the reflective film and the light guide plate (suppressing occurrence of white spot unevenness), the average particle diameter of the polyethylene particles contained in the resin layer ( The ratio (r / d) of (r: μm) to the resin layer thickness (d: μm) is preferably 1.5 or more, more preferably 2.0 or more, and particularly preferably 3.0 or more. The upper limit of the ratio (r / d) is preferably 30 or less, more preferably 25 or less, and particularly preferably 20 or less, from the viewpoint of suppressing the falling off of the polyethylene particles.

  The thickness of the resin layer can be determined, for example, as follows. First, the reflective film of the present invention is cut in a direction perpendicular to the film plane at a knife inclination angle of 3 ° using a rotary microtome manufactured by Japan Microtome Laboratory Co., Ltd. The cross section of the obtained film was observed using a scanning electron microscope (S-3400N, manufactured by Hitachi, Ltd.). The thickness of the five portions where no portion is present is measured, and the average value is defined as the thickness of the resin layer.

  As shown in FIGS. 3A and 3B, the present invention includes a mode in which particles are arranged on the surface of the resin layer in a planar manner with almost no gap to form a projection. In this embodiment, the thickness of the resin layer refers to the distance from the surface of the base material to the surface of the projection made of particles at five points, and the average value is referred to as the thickness of the resin layer. When measuring the distance from the surface of the base material to the surface of the convex portion formed by the particles, if the surface of the convex region formed by the particles is covered with a resin (binder), the covering resin (binder) may be used. Measure the distance including). These embodiments are preferable because the dropout of the particles can be suppressed by coating a part or all of the convex region formed by the particles with the resin contained in the resin layer. That is, by adjusting the average particle diameter of the particles contained in the resin layer, the content ratio of the particles to the resin, or the like, or by adjusting the compatibility of the particles and the resin, one of the convex regions formed by the particles is formed. A part or the whole can be covered with the resin contained in the resin layer.

  The resin layer may contain particles other than polyethylene particles (hereinafter, referred to as “other particles”). When the resin layer contains other particles, the average particle size of the other particles is preferably smaller than the average particle size of the polyethylene particles. It is preferable that the resin layer contains other particles having a relatively small average particle diameter, because the scratch resistance of the resin layer (the scratch is hardly formed) is improved.

  The average particle size of the other particles is preferably 0.8 times or less, more preferably 0.7 times or less, and particularly preferably 0.6 times or less the average particle size of the polyethylene particles. The lower limit is preferably at least 0.05 times, more preferably at least 0.1 times. Specifically, the average particle size of the other particles is preferably in the range of 1 to 20 μm, more preferably in the range of 2 to 15 μm.

  The content of the other particles in the resin layer is preferably from 10 to 200 parts by mass, more preferably from 20 to 150 parts by mass, and particularly preferably from 30 to 130 parts by mass, based on 100 parts by mass of the polyethylene particles. .

  As other particles, for example, as organic particles, acrylic resin particles, silicone resin particles, nylon resin particles, styrene resin particles, benzoguanamine resin particles, urethane resin particles, polyester resin particles and the like Examples of the organic particles include inorganic particles such as silica, aluminum hydroxide, aluminum oxide, zinc oxide, barium sulfide, and magnesium silicate. Among these particles, nylon resin particles are preferable. Nylon-based resin particles have a relatively low hardness, and are therefore preferable from the viewpoint of suppressing damage to the light guide plate.

  In the reflection film according to the present invention, the resin layer is provided on at least one surface of the base film. The resin layer may be provided on only one side of the base film, or may be provided on both sides of the base film.

  The lamination of the resin layer can be performed, for example, by applying a coating composition (coating solution) containing at least a resin, polyethylene particles and an organic solvent on a base film and drying.

  In applying the resin layer coating composition to the base film, any coating method can be used. For example, coating methods such as gravure coating, roll coating, spin coating, reverse coating, bar coating, screen coating, blade coating, air knife coating, and dipping can be used. The coating composition for the resin layer may be applied (in-line coating) during the production of the base film, or may be applied (off-line coating) on the base film after the completion of the crystal orientation.

[Base film]
The substrate film is not particularly limited, and examples thereof include a deposited film of silver or aluminum, a laminated film of silver or aluminum foil, a white film, and a multilayer laminated film.

  When the base film is used as a reflective film, the higher the visible light reflectance, the better. For this reason, a white film containing bubbles and / or incompatible particles inside is preferably used.

  The white film is, for example, a film made of a thermoplastic resin or the like so as to have a white color by adding a white colorant and / or bubbles.

  The white film preferably has high visible light reflectance (for example, preferably has a reflectance of visible light (wavelength of 550 nm) of 95% or more). From this viewpoint, a white film having at least bubbles therein is preferably used. Can be

  The white film having bubbles therein is not particularly limited, but examples thereof include a porous unstretched or biaxially stretched polypropylene film and a porous unstretched or stretched polyethylene terephthalate film. These production methods are described in [0034] to [0057] of JP-A-8-262208, [0007] to [0018] of JP-A-2002-90515, and [0008] of JP-A-2002-138150. ] To [0034]. Above all, a porous white biaxially stretched polyethylene terephthalate film disclosed in JP-A-2002-90515, or a porous white biaxially stretched polyethylene terephthalate film mixed and / or copolymerized with polyethylene naphthalate is preferably used.

  A preferred embodiment of the white film is a film in which a film layer (layer A) is laminated on at least one surface of the above-described film layer (layer B) containing bubbles therein. In this embodiment, the layer A may be laminated on only one side of the layer B, or may be laminated on both sides of the layer B. That is, a two-layer configuration of A layer / B layer and a three-layer configuration of A1 layer / B layer / A2 layer can be given. Among them, a three-layer structure of A1 layer / B layer / A2 layer is preferable from the viewpoint of obtaining high rigidity. Here, the A1 layer and the A2 layer are the A layers, and the A1 layer and the A2 layer may have the same configuration (the same composition and thickness) or different configurations (the composition and / or the thickness are different). There may be.

  In the three-layer structure as described above, the A1 layer and the A2 layer may be formed with completely the same composition, or may be formed with different compositions. It is preferable that the A2 layer has exactly the same composition. In the following description, the A1 layer and the A2 layer may be collectively referred to as an “A layer”, and the expression “A layer” may be expressed as a two-layer A layer and a three-layer A1 layer and an A2 layer. Is included. In the following description, the content of various materials contained in the A layer indicates the content per layer.

  The A layer preferably has a function of supporting (holding) the B layer. From the viewpoint of imparting this function to the layer A, the layer A is preferably a layer mainly composed of resin. Here, that the layer A is a layer mainly composed of a resin means that the resin is contained in an amount of 50% by mass or more with respect to the total amount of the layer A of 100% by mass. Further, the A layer preferably contains 60% by mass or more of the resin, more preferably 70% by mass or more, and particularly preferably 80% by mass or more. The upper limit is about 99% by mass.

  Further, the A layer preferably contains particles. By including the particles in the A layer, a suitable sliding property can be imparted to the reflection film. By providing the reflective film with slipperiness, handleability and workability (such as punching for forming a transmission portion (opening)) are improved.

  As a resin constituting the A layer, a polyester resin is preferable. As such a polyester resin, polyethylene terephthalate (PET) or polyethylene naphthalate (PEN) is preferable. In addition, various known additives such as an antioxidant and an antistatic agent may be added to the polyester resin. The content of the polyester resin constituting the layer A is preferably 50% by mass or more, more preferably 60% by mass or more, and particularly preferably 70% by mass or more, based on 100% by mass of the total amount of the resin constituting the A layer. The upper limit is about 99% by mass.

  Examples of the particles contained in the layer A include organic particles and inorganic particles. Examples of the organic particles include polyester resins, polyamide resins such as benzoguanamine, polyurethane resins, acrylic resins, methacrylic resins, polyamide resins, polyethylene resins, polypropylene resins, polyvinyl chloride resins, polyvinylidene chloride resins, polystyrene resins, and polyacetic acids. Examples include particles made of a resin such as a vinyl resin, a fluorine-based resin, and a silicone resin, and particles made of a copolymer or a mixture of two or more of the above resins.

  Inorganic particles include calcium carbonate, magnesium carbonate, zinc carbonate, titanium oxide, zinc oxide, cerium oxide, magnesium oxide, barium sulfate, zinc sulfide, calcium phosphate, silica, alumina, mica, mica titanium, talc, clay, kaolin, and fluorine. Lithium fluoride, calcium fluoride and the like.

  Among the above particles, inorganic particles are preferable, and among the inorganic particles, calcium carbonate, titanium oxide, barium sulfate, and silica are preferably used.

  The average particle diameter of the particles contained in the layer A is preferably in the range of 0.05 to 15 μm, more preferably in the range of 0.1 to 5 μm, and still more preferably in the range of 0.2 to 3 μm.

  The content of the particles in the A layer is preferably at least 0.005% by mass, more preferably at least 0.01% by mass, based on 100% by mass of the total amount of the A layer. The upper limit of the content is preferably 20% by mass or less, more preferably 10% by mass or less, and particularly preferably 5% by mass or less, based on 100% by mass of the total amount of the layer A. If the content of the particles is less than 0.005% by mass, good sliding properties may not be obtained. On the other hand, if the content of the particles exceeds 20% by mass, the film-forming property may be reduced.

  The layer B is preferably a layer that is whitened by containing fine bubbles inside the film layer. As the layer B, a porous unstretched or biaxially stretched polypropylene film and a porous unstretched or stretched polyethylene terephthalate film are preferably used. As described above, for example, JP-A-8-262208, JP-A-2002-90515, and JP-A-2002-138150 disclose a method for producing a film layer (B layer) containing bubbles therein. It is disclosed in detail and can be used in the present invention.

  The B layer is preferably made of a polypropylene resin or a polyester resin, and is particularly preferably made of a polyester resin. As the polyester resin constituting the layer B, polyethylene terephthalate (PET) or polyethylene naphthalate (PEN) is preferable. In addition, various known additives such as an antioxidant and an antistatic agent may be added to the polyester resin. The content of the polyester resin constituting the layer B is preferably 50% by mass or more, more preferably 60% by mass or more, and particularly preferably 70% by mass or more based on 100% by mass of the total amount of the layer B. The upper limit is about 95% by mass.

  The formation of air bubbles in the layer B can be achieved, for example, by finely dispersing a resin incompatible with the polyester resin in a polyester film as a film substrate and stretching (for example, biaxially stretching) the resin.

  It is preferable that the layer B contains a polyester resin constituting the layer B mixed with an incompatible resin (hereinafter, also referred to as an incompatible resin). By containing the incompatible resin, a cavity having the incompatible resin as a nucleus is formed at the time of stretching, and light reflection occurs at the cavity interface, which is preferable. The resin incompatible with the polyester resin may be a homopolymer or a copolymer, and may be a polyolefin resin such as polyethylene, polypropylene, polybutene, polymethylpentene, a cyclic polyolefin resin, a polystyrene resin, or a polyacrylate. A resin, a polycarbonate resin, a polyacrylonitrile resin, a polyphenylene sulfide resin, a fluororesin, or the like is preferably used. These may be used in combination of two or more.

  Among the above incompatible resins, a resin which has a large difference in critical surface tension from a polyester resin and is not easily deformed by heat treatment after stretching is preferable. Specifically, a polyolefin-based resin is preferable. Examples of the polyolefin-based resin include polyolefin resins such as polyethylene, polypropylene, polybutene, and polymethylpentene; cyclic polyolefin resins; and copolymers thereof.

  The preferred content of the incompatible resin contained in the B layer is 5% by mass or more and 25% by mass or less based on 100% by mass of the total amount of the B layer. In addition, the immiscible resin contained in the layer B should have a number average particle diameter of 0.4 μm or more and 3.0 μm or less dispersed in a matrix made of a polyester resin. It is preferable to obtain Further, the number average particle diameter of the immiscible resin is more preferably in the range of 0.5 μm to 1.5 μm.

  The term "number average particle diameter" as used herein means that a cross section of the film in the width direction (TD) is cut out, and the B layer portion of the cross section is measured using a scanning electron microscope (FE-SEM) S-2100A manufactured by Hitachi, Ltd. It is the average value of the diameters when the area of 100 particles observed is calculated and converted into a perfect circle.

  It is preferable that the layer B further contains particles such as organic particles and inorganic particles. Examples of such particles include the same particles as those described above that can be contained in the layer A. Among these particles, inorganic particles of calcium carbonate, barium sulfate, and titanium dioxide, which have low absorption in the visible light region having a wavelength of 400 to 700 nm, are preferred from the viewpoints of reflection characteristics, concealing properties, production costs, and the like. In the present invention, barium sulfate and titanium dioxide are most preferred from the viewpoints of improving the winding property of the film, the long-term film formation stability, and the reflection characteristics. The average particle diameter of the particles is preferably in the range of 0.1 to 3 μm, and the use of such inorganic particles is preferable since the reflectivity and the concealment property are improved.

  The content of the inorganic particles in the B layer is preferably 0.1% by mass or more, more preferably 0.5% by mass or more based on 100% by mass of the total amount of the B layer, from the viewpoint of securing good reflection characteristics and concealing properties. It is more preferably at least 1% by mass. On the other hand, when the content of such inorganic particles increases, the transmission yellowness (YI) of the reflection sheet tends to increase. Therefore, the upper limit content of the inorganic particles is preferably 10% by mass or less, and more preferably 5% by mass. The lower limit is more preferably 3% by mass or less.

  The B layer preferably further contains a copolyester. By including the copolymerized polyester in the B layer, a stable film can be formed even when the B layer contains a relatively high concentration of inorganic particles. The copolymerized polyester also has a role as a dispersant for the incompatible resin in the B layer.

  Examples of such a copolymerized polyester include a copolymer of polyethylene terephthalate and isophthalic acid, a copolymer of polyethylene terephthalate and cyclohexane dimethanol, and a copolymer of polybutylene terephthalate and polytetramethylene terephthalate. In the present invention, it is preferable to contain at least two types selected from the group consisting of these copolymerized polyesters.

  When the white film has a two-layer configuration, the thickness ratio of each layer is preferably in the range of A layer: B layer = 2: 98 to 20:80 from the viewpoint of maintaining high reflectance, and further, A layer: B Layer = 3: 97 to 10:90 is more preferable.

  In the case where the white film has a three-layer structure, the thickness ratio of each layer is preferably in the range of A1 layer: B layer: A2 layer = 1: 98: 1 to 15:70:15 from the viewpoint of maintaining high reflectance. Further, the range of A1 layer: B layer: A2 layer = 2: 96: 2 to 10:80:10 is more preferable.

  The thickness of the base film is preferably 30 μm or more, more preferably 50 μm or more, and particularly preferably 100 μm or more, from the viewpoint of ensuring high reflectance. The upper limit of the thickness is preferably 1,000 μm or less, more preferably 500 μm or less, further preferably 400 μm or less, and particularly preferably 300 μm or less, from the viewpoint of reducing the thickness of the backlight unit.

  A commercially available base film can be used. For example, as a white film having a single-layer structure, "Lumirror" (registered trademark) E20 (manufactured by Toray Industries, Inc.), SY90, SY95 (manufactured by SKC) and the like can be mentioned. "(Registered trademark) film UXSP, UXJP (manufactured by Teijin Dupont Film Co., Ltd.) and the like. As a three-layer white film," Lumirror "(registered trademark) E60L, E6SL, E6SR, E6SQ, E6Z, E80A , E85D (manufactured by Toray Industries, Inc.), "Tetron" (registered trademark) films UX, UXE, UXS7, UXQ1 (manufactured by Teijin Dupont Films), Lumilex II (manufactured by Mitsubishi Plastics, Inc.), and the like. Examples of the white film having a configuration other than these include Optilon ACR3000, ACR3020 (manufactured by DuPont), and “MCPET” (registered trademark) (manufactured by Furukawa Electric Co., Ltd.).

[Liquid crystal display backlight unit]
The reflective film of the present invention is suitable for a backlight unit of a liquid crystal display. As a backlight method, an edge light type and a direct type are generally adopted, but the reflection film of the present invention is applied to both types. In particular, the reflective film of the present invention is suitable for an edge light type backlight system.

  The edge light type backlight method is a method in which light from a light source disposed at a side end of a light guide plate is propagated through the light guide plate to illuminate a liquid crystal layer (screen). Is disposed on the side opposite to the liquid crystal layer. At this time, the reflective film of the present invention is arranged such that the surface on which the resin layer is laminated faces the light guide plate.

  As described above, such an edge light type backlight system has a problem that the light guide plate and the reflective film come into contact with each other, thereby damaging the light guide plate, and a problem of white spot unevenness due to sticking of the light guide plate and the reflective film. However, these problems are alleviated by using the reflective film of the present invention.

  Further, as described above, the specific problem (the problem of contaminating the light guide plate by heat) when using polyethylene particles generally known in the art for the resin layer is a reflection film of the present invention, that is, It is suppressed by including the polyethylene particles according to the present invention in the resin layer.

  Hereinafter, the present invention will be described in detail with reference to examples, but the present invention is not limited to these examples. In addition, the measuring method, the evaluation method, and the material in this example are shown below.

[Measurement method and evaluation method]
(1) Confirmation of polyethylene particles in resin layer Using a stereomicroscope (manufactured by Nikon, SMZ1500), adjust the magnification appropriately at a magnification of 20 to 200 times, and observe the surface of the resin layer. The contained particles were sampled and used as a sample to be measured.

The obtained sample was further cut, and the vicinity of the center of the particle was measured by the microscopic FT-IR method.
The particle sampling, the cutting treatment, and the measurement by the microscopic FT-IR method were performed on 20 particles contained in the resin layer.

Next, from the infrared light absorption waveform of the microscopic FT-IR obtained as described above, it was confirmed that the resin layer contained polyethylene particles.
The device names and measurement conditions used in the micro FT-IR method are shown below.
-Apparatus: Infrared microscopic spectrometer IRμs (SPECTRA-TECH)
·conditions:
Light source: Silicon carbide rod heating element (manufactured by Grover)
Detector: Narrow MCT (HgCdTe)
Detection wave number range: 4,000 to 650 cm ^-1
Purge: nitrogen gas Measurement mode: transmission method Resolution: 8 cm ^-1
Number of integrations: 512 times Data correction: Baseline correction.

(2) Measurement of melting point of polyethylene particles Measurement and analysis were performed using a differential scanning calorimeter (DSC) (manufactured by Seiko Instruments Inc., RDC220) in accordance with JIS K7121-1987. Using a 5 mg particle sample, a melting curve endotherm was obtained from a DSC curve graph (vertical axis: DSC (mW), horizontal axis: temperature (° C.)) obtained when the temperature was raised from 25 ° C. to 200 ° C. at 20 ° C./min. The temperature indicated by the peak apex was read and defined as the melting point. When there were a plurality of peaks of the melting endothermic peak, the temperature indicated by the vertex having the smallest value in the vertical axis direction (the vertex located closest to the endothermic side) was defined as the melting point.

(3) Measurement of density of polyethylene particles The density was measured by a density gradient tube method (23 ° C.) according to JIS K7112 (1999).

(4) Measurement of viscosity average molecular weight of polyethylene particles In accordance with JIS K7367-3 (1999), intrinsic viscosity [η] and viscosity average molecular weight (Mv) were measured.
20 mg of polyethylene particles were added to 20 mL of decalin (containing 1 g / L of dibutylhydroxytoluene (BHT)) and stirred at 150 ° C. for 2 hours to dissolve the polyethylene particles. Using a Canon-Fenske viscometer (SO), the drop time (ts) of the solution was measured in a thermostat at 135 ° C. As a blank, the fall time (tb) of only decalin in which polyethylene particles were not dissolved was measured. The specific viscosity (ηsp / C) of polyethylene was plotted according to the following equation, and the intrinsic viscosity [η] extrapolated to a concentration of 0 was determined.
(Ηsp / C) = (ts / tb−1) /0.1
From this [η], the viscosity average molecular weight (Mv) was determined according to the following equation.
Mv = (5.37 × 10 ⁴ ) × [η] ^1.37

(5) Average particle diameter of polyethylene particles contained in the resin layer The reflection film was cut in a direction perpendicular to the film plane at a knife inclination angle of 3 ° using a rotary microtome manufactured by Japan Microtome Laboratory Co., Ltd. . The cross section of the obtained film was observed with a scanning electron microscope (S-3400N manufactured by Hitachi, Ltd.) (particles larger than 50 μm were 500 times, and other particles were 1,000 times). The maximum length of each of the 30 particles randomly selected from the particles contained in the layer was measured, and the average value was taken as the average particle diameter of the particles. Here, the maximum length of a particle is a square or a rectangle having the smallest area completely surrounding one particle (that is, a square or a rectangle in which the particle is in contact with four sides of the square or the rectangle). The length of the side, and in the case of a rectangle, the length of the long side (major axis diameter) was taken as the maximum length of the particle (that is, the longest tangential diameter in the fixed direction was taken as the maximum length of the particle).

(6) Thickness of Resin Layer The reflection film was cut in a direction perpendicular to the film plane at a knife inclination angle of 3 ° using a rotary microtome manufactured by Japan Microtome Laboratory Co., Ltd. The cross section of the obtained film was observed using a scanning electron microscope (S-3400N, manufactured by Hitachi, Ltd.) (magnification: 500 times). The thickness was measured at five portions where no protrusions due to particles were present on the surface of the layer, and the average was taken as the thickness of the resin layer.

  In the case of the embodiment in which the surface of the resin layer is covered with particles as shown in FIG. 3, the distance from the surface of the base material to the surface of the convex portion due to the particles is measured at five points, and the average value of the resin layer is measured. It is called thickness. When measuring the distance from the surface of the base material to the surface of the convex portion formed by the particles, if the surface of the convex region formed by the particles is covered with a resin (binder), the covering resin (binder) may be used. Measure the distance including).

(7) Evaluation of Slipperity The coefficient of kinetic friction between the resin layer surface of the reflective film and an acrylic plate (“SUMIPEX” (registered trademark) E (clear) ”, thickness 3 mm, manufactured by Sumitomo Chemical Co., Ltd.) was determined according to JIS K7125 (1999). The measurement was performed using a Toray Slip Tester 200G-15C (manufactured by MAKINO SEISAKUSHO) manufactured in accordance with the JIS regulations. In this evaluation, an acrylic plate, a reflective film, and a sliding piece having the following sizes were placed in this order on a test table of a slip tester, and at this time, the resin layer surface of the reflective film was placed on the acrylic plate side. In addition, the longitudinal direction of the acrylic plate and the reflective film shall be the moving direction (the direction of the relative displacement movement between the contact surface of the acrylic plate and the reflective film), and the contact surface of the acrylic plate and the reflective film at the following moving speed. The relative displacement between them was performed. The coefficient of kinetic friction in this evaluation was calculated from the frictional force at a point 100 mm after the relative displacement movement between the contact surface of the acrylic plate and the reflective film was started.

<Measurement conditions>
Size of reflective film: 80mm x 200mm
Acrylic plate size: 150mm x 300mm
Size of slide piece, mass: 63 mm x 63 mm, 200 g
Moving speed: 150 mm / min.

<Evaluation>
By preparing three test pieces from the same sample for each reflective film, the dynamic friction coefficient was measured three times and averaged. In addition, about the reflective film which has a resin layer on both surfaces of a base material film, each one resin layer surface and the other resin layer surface evaluated each. The thus obtained dynamic friction coefficient was evaluated according to the following criteria.
S: The dynamic friction coefficient is 0.3 or less.
A: The dynamic friction coefficient is greater than 0.3 and 0.6 or less.
B: Dynamic friction coefficient is larger than 0.6.

(8) Heat resistance evaluation 1 (discoloration due to heat)
After heating the reflection film in an atmosphere at a temperature of 60 ° C. for 500 hours, it was allowed to stand at room temperature for 1 hour, and the discoloration of the resin layer surface of the reflection film was visually evaluated according to the following criteria.
A: No discoloration.
B: Discoloration is observed.

(9) Heat resistance evaluation 2 (contamination of light guide plate by heat)
A 17-inch liquid crystal television (manufactured by Panasonic Corporation, "VIERA" (registered trademark) TH-L17F1) was disassembled, and an edge light type backlight using LED as a light source (hereinafter referred to as backlight A) was taken out. The size of the light emitting surface of the backlight A was 37.5 cm × 21.2 cm, and the diagonal length was 43.1 cm. Further, from the backlight A, three optical films, a light guide plate (acryl plate, 3.5 mm thickness, the height of the convex portion formed on the light guide plate of 12 μm) and the reflection film were taken out, and the reflection film of the present invention was mounted. It was cut into the same shape and size as the reflective film. After preparing the cut sample for each reflective film, place the reflective layer instead of the mounted reflective film so that the resin layer surface of the cut sample faces the light guide plate side, disassemble the light guide plate and three optical films Installed in the same order and orientation as before.

The backlight A thus disassembled and assembled is heated in an atmosphere at a temperature of 80 ° C. for 1 hour, then left at room temperature for 1 hour, and the liquid crystal television is disassembled again, and the surface of the light guide plate in contact with the reflective film. Was visually evaluated according to the following criteria.
S: No contamination.
A: Slight contamination is observed, but at an acceptable level.
B: Contaminated.

(10-1) Evaluation of Light Guide Plate Damage (Scratch Scratch) Part 1
A sample was prepared for each reflective film, and the surface of the resin layer of the reflective film was in contact with the surface of the light guide plate obtained by disassembling a 40-inch liquid crystal television (PAVV UN40B7000WF, manufactured by Samsung) on which the convex portion was provided. after lamination ^{as, 200gf / cm 2 (0.0196MPa)} , linear reflection film of 1 m / min under a load of 100gf / cm ² (0.0098MPa) and 50gf / cm ² (0.0049MPa) It was pulled up at a speed, and the degree of scratches generated on the surface of the light guide plate was visually observed and evaluated according to the following criteria.
Class A: No damage is seen under any load.
Class B: 200 gf / cm ² of but scratches is observed under load, under a load of 100 gf / cm ^2, not seen wounds under a load of 50 gf / cm ^2.
Class C: 200gf / cm ^2, but scratches observed under a load of 100 gf / cm ^2, not seen wounds under a load of 50 gf / cm ^2.
Class D: Scratches are seen under a load of 50 gf / cm ² .

(10-2) Evaluation of damage to light guide plate (transfer contamination of particle shavings) Part 2
A 40-inch liquid crystal television (manufactured by Samsung, PAVV UN40B7000WF) was disassembled and laminated so that the surface of the resin layer of the reflective film was in contact with the surface of the light guide plate on which the convex portions were provided, and then 200 gf The reflective film is pulled up at a linear velocity of 1 m / min under a load of / cm ² (0.0196 MPa), and the shavings of the particles contained in the reflective film are transferred to the light guide plate on the surface of the light guide plate, thereby forming the light guide plate. The presence or absence of contamination was visually observed and evaluated according to the following criteria.
A: No contamination.
B: Contaminated.

(11) Evaluation of white spot unevenness (attachment of reflective film and light guide plate) 52-inch liquid crystal television ("BRAVIA" (registered trademark) KDL-52EX700, manufactured by Sony Corporation) is disassembled and an edge using LED as a light source The light-type backlight was taken out. The size of the light emitting surface of this backlight was 116 cm × 65.5 cm, and the diagonal length was 133.2 cm. Furthermore, three optical films, a concave light guide plate (acrylic plate, 4 mm thickness, concave depth 55 μm) and a reflective film are taken out from the backlight, and cut into the same shape and size as the reflective film on which the reflective film of the present invention is mounted. did. After preparing the cut sample for each reflective film, place the cut reflective film in place of the mounted reflective film so that the resin layer surface of the cut reflective film faces the light guide plate side, and disassemble the light guide plate and three optical films before disassembly. It was installed in the same direction and direction as.
The liquid crystal television was turned on, and white spot unevenness was visually observed according to the following criteria.
S: No white spot is observed.
A: White spots are slightly observed, but at an acceptable level.
B: White spots are clearly observed.

(12) Evaluation of coatability of resin layer The resin layer applied on the base film was visually observed, and the degree of occurrence of streak-like unevenness was evaluated according to the following criteria.
S: No streak unevenness is observed.
A: Thin streak unevenness is observed.
B: Streak unevenness is clearly recognized.

(13) Confirmation of protrusions due to particles on the surface of the resin layer The surface of the resin layer of the reflective film was scanned with a scanning electron microscope (S-3400N, manufactured by Hitachi, Ltd.) (500 times) at an angle of 30 degrees with respect to the surface of the resin layer. Observation was performed at an oblique angle, and it was confirmed whether or not a convex portion was present.

[Particles to be contained in resin layer]
Various particles as shown below were prepared. The shape of the particles is spherical except for the particles g and j (amorphous).

<Particle (a); Particle composed of a homopolymer of ethylene having a viscosity average molecular weight of more than 100,000>
Mitsui Chemicals Co., Ltd. "Miperon" (registered trademark) XM-220, density 940 kg / ^{m 3,} viscosity average molecular weight of 2,000,000

<Particles (b); particles comprising a homopolymer of ethylene having a viscosity average molecular weight of more than 100,000>
“Miperon” (registered trademark) XM-221U manufactured by Mitsui Chemicals, Inc., density 940 kg / m ³ , viscosity average molecular weight 2,000,000,

<Particle (c); Particle composed of a homopolymer of ethylene having a viscosity average molecular weight of more than 100,000>
“Miperon” (registered trademark) PM-200 manufactured by Mitsui Chemicals, Inc., density 940 kg / m ³ , viscosity average molecular weight 1.8 million

<Particle (d); Particle composed of a homopolymer of ethylene having a viscosity average molecular weight of more than 100,000>
“Miperon” (registered trademark) XM-330 manufactured by Mitsui Chemicals, Inc., density 940 kg / m ³ , viscosity average molecular weight 2,000,000

<Particle (e); High-density polyethylene particles>
Sumitomo Seika Chemicals Co., Ltd. "Flow beads" (registered trademark) HE-3040, density of 961kg / ^{m 3,} viscosity average molecular weight 450,000

<Particle (f); Low-density polyethylene particles>
"Flow beads" (registered trademark) LE-2080 manufactured by Sumitomo Seika Co., Ltd., density 919 kg / m ³ , viscosity average molecular weight 100,000

<Particles (g); Low-density polyethylene particles>
"Flosen" (registered trademark) UF20 manufactured by Sumitomo Seika Co., Ltd., density 921 kg / m ³ , viscosity average molecular weight 150,000

<Particle (h); Crosslinked acrylic particles>
"Techpolymer" (registered trademark) MBX-30 manufactured by Sekisui Plastics Co., Ltd.

<Particle (i); Crosslinked acrylic particles>
"Techpolymer" (registered trademark) SSX-104 manufactured by Sekisui Plastics Co., Ltd.

<Particle (j); polyethylene wax particles>
"Celidust" (registered trademark) 3620, manufactured by Clariant, having a viscosity average molecular weight of 4,800.

<Particle (k); Other particles>
SP10 (nylon 12 resin particles) manufactured by Toray Industries, Inc.

<Particle (l); Other particles>
SP500 (nylon 12 resin particles) manufactured by Toray Industries, Inc.

[Example 1]
One side of a white film (“Lumirror” (registered trademark) E6SQ: 300 μm, manufactured by Toray Industries, Inc.) is coated with the following resin layer coating solution using a bar coater so that the resin layer thickness is about 3 μm. Then, the resultant was dried at 100 ° C., and a resin layer was laminated thereon to produce a reflection film.

<Resin layer coating liquid>
70 parts by mass of a benzotriazole-containing acrylic copolymer resin (“Hals Hybrid” (registered trademark) UV-G720T concentration 40% by mass solution manufactured by Nippon Shokubai Co., Ltd.), particles a (“Miperone” manufactured by Mitsui Chemicals, Inc.) (Registered trademark) XM-220, viscosity average molecular weight 2,000,000) 12 parts by mass, isocyanate type crosslinking agent ("Coronate" (registered trademark) HL, manufactured by Nippon Polyurethane Industry Co., Ltd., concentration 75% by mass) 2.7 parts by mass And 55 parts by mass of ethyl acetate were added with stirring to prepare a coating solution.

  The solid content concentration of this coating solution is 30% by mass. Further, the content ratio of the particles was 28.6% by mass and the content ratio of the resin was 66.7% by mass based on 100% by mass of the total solid content contained in the coating solution.

[Examples 2 to 5 and Comparative Examples 1 to 5]
A reflective film was produced in the same manner as in Example 1, except that the particles a in the resin layer coating solution of Example 1 were changed to the particles shown in Table 1. In addition, in Example 4, it applied so that resin layer thickness might be set to about 6 micrometers.

[Example 6]
A reflective film was produced in the same manner as in Example 1, except that the following resin layer coating liquid was used.
<Resin layer coating liquid>
50 parts by mass of benzotriazole-containing acrylic copolymer resin ("Hals Hybrid" (registered trademark) UV-G720T concentration 40% by mass solution manufactured by Nippon Shokubai Co., Ltd.), particles a ("Miperone" manufactured by Mitsui Chemicals, Inc.) (Registered trademark) XM-220, viscosity average molecular weight 2,000,000) 20 parts by mass, isocyanate-based crosslinking agent ("Coronate" (registered trademark) HL, manufactured by Nippon Polyurethane Industry Co., Ltd., concentration: 75% by mass) 2.7 parts by mass And 67 parts by mass of ethyl acetate were added with stirring to prepare a coating solution.
The solid content concentration of this coating solution is 30% by mass. Further, the content ratio of the particles was 47.6% by mass and the content ratio of the resin was 47.6% by mass with respect to the total solid content of 100% by mass contained in this coating solution.

[Example 7]
A reflective film was produced in the same manner as in Example 1, except that the following resin layer coating liquid was used.
<Resin layer coating liquid>
85 parts by mass of benzotriazole-containing acrylic copolymer resin (“Hals Hybrid” (registered trademark) UV-G720T concentration 40% by mass solution manufactured by Nippon Shokubai Co., Ltd.), particles a (“Miperone” manufactured by Mitsui Chemicals, Inc.) (Registered trademark) XM-220, viscosity average molecular weight 2,000,000) 6 parts by mass, isocyanate type crosslinking agent ("Coronate" (registered trademark) HL, manufactured by Nippon Polyurethane Industry Co., Ltd., concentration 75% by mass) 2.7 parts by mass And 46 parts by mass of ethyl acetate were added with stirring to prepare a coating solution.
The solid content concentration of this coating solution is 30% by mass. Further, the content ratio of the particles was 14.3% by mass and the content ratio of the resin was 81.0% by mass based on 100% by mass of the total solid content contained in this coating solution.

[Example 8]
A reflective film was produced in the same manner as in Example 1, except that the following resin layer coating liquid was used.
<Resin layer coating liquid>
16 parts by mass of benzotriazole-containing acrylic copolymer resin (“Hals Hybrid” (registered trademark) UV-G720T concentration: 40% by mass solution manufactured by Nippon Shokubai Co., Ltd.), particles a (“Miperone” manufactured by Mitsui Chemicals, Inc.) (Registered trademark) XM-220, viscosity average molecular weight 2,000,000) 33.6 parts by mass, isocyanate crosslinking agent ("Coronate" (registered trademark) HL, manufactured by Nippon Polyurethane Industry Co., Ltd., concentration: 75% by mass) 2.7 Parts by mass and 87 parts by mass of ethyl acetate were added with stirring to prepare a coating solution.
The solid content concentration of this coating solution is 30% by mass. Further, the content ratio of the particles was 80.0% by mass and the content ratio of the resin was 15.2% by mass based on 100% by mass of the total solid content contained in this coating solution.

[Example 9]
A reflective film was produced in the same manner as in Example 1, except that the following resin layer coating liquid was used.
<Resin layer coating liquid>
26.5 parts by mass of benzotriazole-containing acrylic copolymer resin (“Hals Hybrid” (registered trademark) UV-G720T concentration 40% by mass solution manufactured by Nippon Shokubai Co., Ltd.), particles a (Mitsui Chemicals, Inc.) 29.4 parts by mass of Miperon® (registered trademark) XM-220, viscosity average molecular weight 2,000,000, isocyanate type crosslinking agent (“Coronate” (registered trademark) HL, manufactured by Nippon Polyurethane Industry Co., Ltd., concentration: 75% by mass) 2 0.7 parts by mass and 84 parts by mass of ethyl acetate were added with stirring to prepare a coating solution.
The solid content concentration of this coating solution is 30% by mass. Further, the content ratio of the particles was 70.0% by mass and the content ratio of the resin was 20.2% by mass based on 100% by mass of the total solid content contained in this coating solution.

[Example 10]
A reflective film was produced in the same manner as in Example 1, except that the following resin layer coating liquid was used.
<Resin layer coating liquid>
96.8 parts by mass of benzotriazole-containing acrylic copolymer resin ("Hals Hybrid" (registered trademark) UV-G720T concentration 40% by mass solution manufactured by Nippon Shokubai Co., Ltd.), particles a (manufactured by Mitsui Chemicals, Inc.) 1.3 parts by mass of Miperon® (registered trademark) XM-220, viscosity average molecular weight 2,000,000), isocyanate-based crosslinking agent (“Coronate” (registered trademark) HL, manufactured by Nippon Polyurethane Industry Co., Ltd., concentration: 75% by mass) 2 0.7 parts by mass and 39 parts by mass of ethyl acetate were added with stirring to prepare a coating solution.
The solid content concentration of this coating solution is 30% by mass. Further, the content ratio of the particles was 3.0% by mass and the content ratio of the resin was 92.2% by mass with respect to 100% by mass of the total solid content contained in this coating solution.

[Example 11]
A reflective film was produced in the same manner as in Example 1, except that the following resin layer coating liquid was used.
<Resin layer coating liquid>
94.8 parts by mass of benzotriazole-containing acrylic copolymer resin ("Hals Hybrid" (registered trademark) UV-G720T concentration 40% by mass solution manufactured by Nippon Shokubai Co., Ltd.), particles a (manufactured by Mitsui Chemicals, Inc.) 2.1 parts by mass of Miperon® (registered trademark) XM-220, viscosity average molecular weight 2,000,000, isocyanate-based crosslinking agent (“Coronate” (registered trademark) HL, manufactured by Nippon Polyurethane Industry Co., Ltd., concentration: 75% by mass) 2 0.7 parts by mass and 40 parts by mass of ethyl acetate were added with stirring to prepare a coating solution.
The solid content concentration of this coating solution is 30% by mass. Further, the content ratio of the particles was 5.0% by mass and the content ratio of the resin was 90.3% by mass based on 100% by mass of the total solid content contained in this coating solution.

[Example 12]
A reflective film was produced in the same manner as in Example 1, except that the following resin layer coating liquid was used.
<Resin layer coating liquid>
Benzotriazole-containing acrylic copolymer resin ("Hals Hybrid" (registered trademark) UV-G720T concentration 40% by mass solution manufactured by Nippon Shokubai Co., Ltd.) 86.3 parts by mass, particles a (manufactured by Mitsui Chemicals, Inc.) 3.4 parts by mass of MIPERON® (registered trademark) XM-220, viscosity average molecular weight 2,000,000), 2.1 parts by mass of nylon particles (SP10 manufactured by Toray Industries, Inc.), isocyanate-based crosslinking agent (Nippon Polyurethane Industry Co., Ltd.) 2.7 parts by mass of "Coronate" (registered trademark) HL, concentration: 75% by mass) and 45 parts by mass of ethyl acetate were added with stirring to prepare a coating solution.
The solid content concentration of this coating solution is 30% by mass. In addition, the content ratio of polyethylene particles a was 8.1% by mass, the content ratio of nylon particles was 5.0% by mass, and the content ratio of resin was 82.2% by mass based on 100% by mass of the total solid content contained in this coating solution. It is.

[Examples 13 to 18]
In Examples 6, 7, 9 to 12, a reflection film was produced in the same manner except that particles a of the resin layer coating liquid were changed to particles e. The sixth embodiment corresponds to the thirteenth embodiment. Similarly, the seventh embodiment is the fourteenth embodiment, the ninth embodiment is the fifteenth embodiment, the tenth embodiment is the sixteenth embodiment, the eleventh embodiment is the seventeenth embodiment, and the twelfth embodiment. Corresponds to Example 18 respectively. Further, in Example 18, the nylon particles (SP10) of Example 12 were changed to nylon particles (SP500).

[Evaluation]
The above-described measurement and evaluation were performed on the reflective films produced in the above Examples and Comparative Examples. The results are shown in Tables 1 and 2.
In each of the examples and the comparative examples, it was confirmed that a convex portion due to particles was present on the surface of the resin layer.

  In all of the examples of the present invention, the heat resistance 1 (no discoloration due to heat) and the heat resistance 2 (no contamination of the light guide plate due to heat) are good, and damage to the light guide plate and unevenness of white spots are observed. The occurrence is suppressed. Further, all the examples of the present invention have good slipperiness and coatability.

  On the other hand, Comparative Examples 1 and 2 using polyethylene particles having a melting point of less than 115 ° C. are inferior in heat resistance 2 (there is no contamination of the light guide plate by heat). Further, in Comparative Examples 1 and 2, since the sliding property is poor, particles are cut off by contact with the light guide plate and transferred to the light guide plate, thereby contaminating the light guide plate. Further, Comparative Examples 1 and 2 are inferior in coatability and cause streak unevenness. Comparative Examples 1 and 2 are inferior in evaluation of white spot unevenness.

  Comparative Example 3 using the crosslinked acrylic particles is inferior in damage to the light guide plate.

  In Comparative Example 4 using the crosslinked acrylic particles, damage to the light guide plate was inferior, and since particles having a relatively small average particle diameter were used, white spot unevenness was observed.

  Comparative Example 5 using polyethylene-based wax particles (having a viscosity average molecular weight of less than 10,000) is inferior in heat resistance 2 (no light guide plate is contaminated by heat). Further, in Comparative Example 5, the particles were shaved by contact with the light guide plate and transferred to the light guide plate due to poor slipperiness, thereby contaminating the light guide plate. Further, Comparative Example 5 was inferior in coatability and caused the occurrence of streak-like unevenness. Comparative Example 5 was inferior in evaluation of white spot unevenness.

  INDUSTRIAL APPLICABILITY The reflection film according to the present invention can be applied to any reflection film requiring suppression of sticking to a member (contact member) in contact with the reflection film, suppression of damage to the contact member or contamination of the contact member due to heat, and heat resistance. In particular, it is suitable for use in an edge light type backlight unit.

1: coating with resin 2: particles (polyethylene particles)
3: resin layer 4: base film 100: reflective film

Claims (7)

A reflective film comprising a resin film containing, on at least one surface of a substrate film, polyethylene particles having a viscosity average molecular weight of 450,000 to less than 700,000 and a melting point of 130 ° C to 136 ° C. Density of the polyethylene particles is 942kg / ^{m 3} or more, the reflection film according to claim 1. The dynamic friction coefficient of the side surface and the acrylic board having a resin layer of at least one surface of the reflective film is 0.6 or less, the reflection film according to claim 1 or 2. The reflective film according to any one of claims 1 to 3 , wherein the content of the polyethylene particles in the resin layer is 3 to 75% by mass based on 100% by mass of the total amount of the resin layer. The reflective film according to any one of claims 1 to 4 , wherein the base film is a film having bubbles therein at least. The reflective film according to any one of claims 1 to 5 , wherein the base film is a film in which a film layer (layer A) is laminated on both sides of a film layer (layer B) containing bubbles therein. An edge light type backlight unit, wherein the reflection film according to any one of claims 1 to 6 is arranged so that the surface on the side having the resin layer faces the light guide plate.

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