WO2016042992A1 - Reflective film and edge-lit backlight unit using same - Google Patents

Abstract

A reflective film which is characterized by having, on at least one surface of a base film, a resin layer that contains polyethylene particles having a viscosity average molecular weight of 10,000 or more and a melting point of 115°C or more. The present invention is able to provide a reflective film which is suppressed in adhering to a member (for example, a light guide plate) that comes into contact with the reflective film, while being capable of suppressing damage (such as scratches and contamination) on the contact member (for example, a light guide plate) and contamination of the contact member by heat at the same time, and which has good heat resistance (and undergoes little discoloration due to heat).

Description

Reflective film and edge light type backlight unit using the same

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

The liquid crystal display device generally employs a backlight system that emits light by illuminating the liquid crystal layer from the back. As this backlight system, an edge light type and a direct type are known.

As a reflective film used in 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 projected by particles. A reflective film in which a portion (projection) is formed is known.

For example, in order to improve the luminance of the backlight and suppress luminance unevenness, a resin layer that defines particle coverage, the number of particles stacked, the height of protrusions, the number of protruding particles, and the like has been proposed (for example, Patent Document 1). ~ 4).

In addition, in order to suppress sticking between the light guide plate and the reflective film constituting the edge light type backlight unit, or to suppress scratches on the light guide plate due to contact between the light guide plate and the reflective film, It has been proposed that particles are contained in the resin layer to form convex portions (projections) due to 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 Japanese Patent Laid-Open No. 2003-92018 Special table 2008-512719 International Publication No. 2011/105294 JP 2012-108190 A JP 2012-159610 A

In the above-mentioned patent documents, many types of particles are disclosed 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 inventors of the present invention have noticed that polyethylene particles have relatively low hardness and relatively little deterioration (discoloration, etc.) due to heat, and have started to develop a reflective film that takes advantage of these characteristics.

However, when polyethylene particles generally known from the past are contained in the resin layer, they are likely to melt and deform under a high temperature environment during processing or product use, and as a result, a member that contacts the reflective film ( For example, it has been found that it causes an inconvenient problem of contaminating the light guide plate).

Also, it is known that polyethylene particles have relatively good slipperiness. However, when polyethylene particles generally known from the past are included in the resin layer to form protrusions (projections) on the surface of the reflective film, the slipperiness due to contact with the 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 scraped off by contact with the light guide plate adheres to the light guide plate and contaminates the light guide plate.

Accordingly, an object of the present invention is to stick to a member (for example, a light guide plate) that comes into contact with a reflective film, taking advantage of the properties of polyethylene particles (the properties of relatively low hardness and relatively little deterioration (discoloration) against heat). At the same time, it is possible to suppress damage (scratch scratches and contamination) of the contact member (for example, light guide plate) and contamination of the contact member (for example, light guide plate) due to heat, and heat resistance (small discoloration due to heat). ) Is to provide a good reflective film.

The above object of the present invention has been basically achieved by the following invention.
[1] A reflective film comprising 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 reflective 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 coefficient of dynamic friction between the surface having the resin layer on at least one surface of the reflective film and the acrylic plate 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 with respect to 100% by mass of the total resin layer.
[6] The reflective film according to any one of [1] to [5], wherein the base film is a film having at least air bubbles inside.
[7] The film according to any one of [1] to [6], wherein the base film is a film in which a film layer (A layer) is laminated on both surfaces of a film layer (B layer) containing air bubbles inside. Reflective film.
[8] An edge-light type backlight unit in which the reflective film according to any one of [1] to [7] is disposed so that the surface having the resin layer faces the light guide plate.

According to the present invention, damage to the contact member (for example, the light guide plate) (scratch scratch, Contamination) and contamination of the contact member (for example, the light guide plate) due to heat can be suppressed, and a reflective film having good heat resistance (small discoloration due to heat) can be provided.

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 reflective film of the present invention is particularly suitable for an edge light type backlight unit, and the backlight unit is disposed so that the reflective film and the light guide plate are in contact with each other. Hereinafter, a light guide plate is used as an example of a contact member. The effects of the present invention will be described.

White spot unevenness (a phenomenon in which a spot that is brightly visible in a dotted shape occurs) may occur due to sticking between the reflective film and the light guide plate, but sticking to the light guide plate by using the reflective film of the present invention. Sticking is suppressed, and as a result, the occurrence of uneven white spots is suppressed.

Although a light guide plate may be damaged when a reflective film and a light guide plate contact, damage to a light guide plate is suppressed by using a reflective film of the present invention. Here, the damage to the light guide plate includes, for example, scratching the light guide plate, or particles in the resin layer of the reflective film being 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 become hot when the liquid crystal display device is turned on. When conventional polyethylene particles are used as particles to be included in the resin layer, the polyethylene particles melt and contaminate the light guide plate. However, by using the reflective film of the present invention, such contamination of the light guide plate by heat is suppressed.

Furthermore, 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 an image of the surface photograph by the scanning electron microscope of the resin layer surface which shows an example of the reflective 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 together with embodiments.
The reflective film of the present invention is characterized by 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. 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 the resin layer surface has convex portions formed of the polyethylene particles.

It is preferable to provide the convex portions as described above on the surface of the resin layer because sticking between the reflective film and the light guide plate is suppressed, and as a result, occurrence of white spot unevenness is suppressed. And it is preferable to form the convex part with the polyethylene particles according to the present invention because damage (scratch scratches or contamination) of the light guide plate and contamination of the light guide plate due to heat are suppressed. In addition, it is preferable to use the polyethylene particles according to the present invention because heat resistance (discoloration due to heat) is improved.

Here, whether or not the convex portions of the particles are formed on the surface of the resin layer can be confirmed by, for example, observing the surface of the resin layer with a scanning electron microscope (SEM) at a magnification of 500 times. In this case, the observation can be made more clearly 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 taken by a scanning electron microscope on the surface of a resin layer as an example of a reflective film according to the present invention. It can be clearly confirmed that convex portions due to particles are present on the surface of the resin layer of the reflective film 100.

2 and 3 are schematic sectional views showing examples of the resin layer portion of the reflective film according to the present invention. In FIG. 2, the code | symbol 1 is the film | membrane by resin, the code | symbol 2 is a particle | grain (the polyethylene particle whose viscosity average molecular weight is 10,000 or more and melting | fusing point is 115 degreeC or more), and the code | symbol 3 contains the resin layer containing the particle | grains 2, The code | symbol 4 has each shown the base film.

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

Further, the convexity may be formed by arranging the particles on the surface of the resin layer in a planar manner with almost no gap (FIG. 3A), and further, the convexity with a plurality of particles overlapping 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 a part or all of the convex region is covered with a resin (binder) contained in the resin layer. This is preferable because dropout 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 made of an ethylene homopolymer and / or particles made of a copolymer containing ethylene as a main component. 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. or higher, from the viewpoint of suppressing sticking between the reflective film and the light guide plate and suppressing damage to the light guide plate or thermal contamination. The above is particularly preferable.

On the other hand, as the melting point of the polyethylene particles increases, the transparency tends to decrease and the hardness tends to increase. Therefore, the upper limit of the melting point of the polyethylene particles is to ensure the transparency of the particles and the hardness of the particles. From the standpoint of suppressing damage to the light guide plate by making it relatively small, it 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 from the viewpoint of suppressing sticking between the reflective film and the light guide plate and suppressing damage to the light guide plate or thermal contamination. More preferably, it is particularly preferably 150,000 or more.

As described above, the polyethylene particles according to the present invention include particles made of a copolymer having ethylene as a main component, and the copolymer having 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 original characteristics of the polyethylene particles (the characteristics that the polyethylene particles have relatively low hardness and relatively little deterioration (discoloration, etc.) due to heat) are sufficient. It may not develop. The ethylene content in the copolymer is preferably 70% by mass or more, more preferably 80% by mass or more, and more preferably 90% by mass or more from the above viewpoint (from the viewpoint of sufficiently expressing the original characteristics of the polyethylene particles). Particularly preferred. The upper limit is about 99% by mass. The copolymer component of the copolymer includes α-olefins (for example, propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, 1-decene, 1-dodecene, 4-methyl-1-pentene). , 3-methyl-1-pentene, etc.), cyclic olefin, acrylic acid, methacrylic acid, acrylic ester, methacrylic ester, styrene, fluorinated ethylene and the like.

Among the above copolymer components, α-olefin, cyclic olefin, acrylic acid, methacrylic acid, acrylic ester, methacrylic ester, and styrene are preferable, and α-olefin and cyclic olefin are particularly preferable.

Among the above-mentioned polyethylene particles, particles made of an ethylene homopolymer are particularly preferable. Particles made of an ethylene homopolymer have an appropriate hardness, so that damage to the light guide plate can be effectively suppressed, and mixing to the resin layer is relatively good, and the applicability of the resin layer is relatively good. There are advantages.

One preferred embodiment of the polyethylene particles according to the present invention is, for example, particles having a viscosity average molecular weight of 10,000 or more and a melting point of 115 ° C. or more among polyethylene particles having a density of 942 kg / m ³ or more. It 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, the density of the high density polyethylene particles is preferably higher 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 suppressing sticking between the reflective film and the light guide plate. Preferably, it is 100,000 or more, more preferably 150,000 or more. The upper limit of the viscosity average molecular weight of the high density polyethylene particles is not particularly limited, but is preferably less than about 700,000.

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

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

The above-mentioned 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 1,500,000 or more from the viewpoint of obtaining a higher melting point. The upper limit is not particularly limited, but is preferably 20 million or less, more preferably 10 million or less, particularly preferably 7 million or less, and most preferably 5 million or less.

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

Examples of polyethylene particles having a melting point of 115 ° C. or higher and a viscosity average molecular weight of 700,000 or higher include “Miperon” (registered trademark, product name) series (manufactured by Mitsui Chemicals), “Hi-Zex Million” (registered trademark, product) Name) Series (made by Mitsui Chemicals), “Sun Fine” (registered trademark, product name) series (made by Asahi Kasei Chemicals), “Dyneema” (registered trademark, product name) series (made by DSM), “Spectra” ( Registered trademark, product name) series (manufactured by Honeywell), "GUR" (registered trademark, product name) series (manufactured by Ticona), "Hostalen" (registered trademark, product name) series (manufactured by Hoechst), etc. .

The polyethylene particles according to the present invention are preferably contained so that convex portions of the polyethylene particles are formed on the surface of the resin layer. In this respect, the average particle diameter (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 containing polyethylene particles having an average particle diameter of 5 μm or more in the resin layer, moderate convex portions are formed on the surface of the resin layer, and as a result, sticking between the reflective 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, more preferably 75 μm or less, from the viewpoint of suppressing dropping of the polyethylene particles and ensuring uniform coating properties when the resin layer is formed by coating. The thickness is preferably 50 μm or less.

Polyethylene particles having an average particle diameter of 5 to 100 μm are contained in the resin layer, and appropriate convex portions are formed on the surface of the resin layer. Sticking with the light plate can be effectively suppressed. Moreover, since the convex part formed with the polyethylene particle has comparatively small hardness, it can suppress the damage of a light-guide plate, and is preferable.

Here, the average particle diameter (r: μm) is a square or rectangle having the smallest area that completely surrounds one particle on a photograph. In the case of a square, the length of one side, and in the case of a rectangle, the length of a long side. The length (major axis diameter) is defined as the maximum length of the particles, and is 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 convex portion on the resin layer with spherical polyethylene particles, the light guide plate can be further prevented from being damaged. Here, “spherical” does not necessarily mean only a true sphere, but means that the cross-sectional shape of the particle is surrounded by a curved surface such as a circle, an ellipse, a substantially circle, or a substantially ellipse. In the cross section, the ratio of major axis to minor axis (major axis / minor axis) means 1.4 or less.

By forming a convex portion of the polyethylene particles according to the present invention on the surface of the resin layer, for example, a preferable effect of improving the slipperiness of the reflective film surface is exhibited. By improving the slipperiness of the reflective film surface, damage (scratch scratch) 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. This is preferable because contamination of the light guide plate is suppressed.

Conventionally known polyethylene particles (particles having a relatively low melting point) do not improve the slipperiness of the reflective film surface when they are contained in the resin layer and have convex portions formed on the resin layer surface. Rather, it was found that the slipperiness was inferior. In the same manner as above, polyethylene wax particles (general polyethylene wax particles having a viscosity average molecular weight of less than 10,000) are also included in the resin layer to form convex portions on the surface of the reflective film. It was found that the slipperiness was not improved but rather slippery. The reason for this is presumed that the convex portions formed by conventional polyethylene particles or polyethylene wax particles are compressed and deformed by contact with a contact member (for example, a light guide plate), and slipperiness is reduced. When the slipperiness is inferior, the polyethylene particles contained in the resin layer may be scraped off to contaminate the light guide plate.

The slip property of the reflective film surface can be expressed 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 the reflective film surface of at least one surface 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 on the surface of the reflective film only on one surface may be 0.6 or less (particularly 0.3 or less is preferable) The dynamic friction coefficient on the surface of the reflective film may be 0.6 or less (particularly 0.3 or less is preferable).

In addition, when the reflective film surface has good sliding properties, when the backlight vibrates or when the light guide plate is thermally deformed, the effect that the reflective film is not easily deformed by being caught by the light guide plate 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 only on 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 a resin mainly composed of organic components is preferable. For example, polyester resin, polyurethane resin, acrylic resin, methacrylic resin, polyamide resin, polyethylene resin, polypropylene resin, polyvinyl chloride resin, polyvinylidene chloride resin , Polystyrene resin, polyvinyl acetate resin, fluorine resin and the like.

These resins may be used alone, or two or more copolymers or a mixture thereof may be used. Of these, polyester resins, polyurethane resins, acrylic resins or methacrylic resins are preferably used in terms of heat resistance, additive dispersibility, productivity, and glossiness.

Also, 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). Examples of the ultraviolet absorbing component contained in these resins include benzotriazole and benzophenone, and examples of the light stabilizing component contained in the resin include hindered amine (HALS). In particular, 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 in the molecule and an acrylic monomer, a resin obtained by copolymerizing a polymerizable monomer containing a light stabilizing component in the molecule and an acrylic monomer, or Examples thereof include a resin 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.

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 Stub LA-” manufactured by ADEKA Corporation). 82 ").

The method for producing these resins is disclosed in detail in Japanese Patent Application Laid-Open No. 2002-90515, and can be produced with reference to this. In addition, these resins are commercially available as “Hals Hybrid” (registered trademark) from Nippon Shokubai Co., Ltd., and can be obtained.

In order to suppress sticking between the reflective film and the light guide plate, it is preferable to form an appropriate amount of convex portions on the surface of the resin layer. From this viewpoint, the content of polyethylene particles in the resin layer is the total amount of the resin layer. 3 mass% or more is preferable with respect to 100 mass%, 5 mass% or more is more preferable, 7 mass% or more is further more preferable, and 10 mass% or more is especially preferable. The upper limit 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 coating properties at the time of forming the resin layer. 55 mass% or less is particularly preferable. That is, the content of polyethylene particles in the resin layer is preferably 3 to 75% by mass with respect to 100% by mass of the total resin layer.

The content of the resin (binder) in the resin layer is such that the total amount of the resin layer is 100 from the viewpoint of fixing the polyethylene particles and suppressing dropping off, and ensuring uniform coatability when the resin layer is applied and formed. 20 mass% or more is preferable with respect to mass%, 25 mass% or more is more preferable, and 30 mass% or more is especially preferable. The upper limit of the resin content is preferably 90% by mass or less, and 85% by mass or less, with respect to 100% by mass of the total resin layer, from the viewpoint of forming a moderately large convex portion on the surface of the resin layer. More preferred is 80% by mass or less.

The resin layer preferably further contains a crosslinking agent. That is, the resin layer is formed from a composition containing the above-described resin (binder) and a crosslinking agent, whereby a crosslinked structure is formed in the resin layer and the hardness of the resin layer is improved. It is preferable because the effect of suppressing dropout can be improved.

As such a crosslinking agent, an isocyanate-based, melamine-based, or epoxy-based crosslinking agent is preferable, and an isocyanate-based crosslinking agent is preferable from the viewpoint that a crosslinking 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 with respect to 100% by mass of the total resin layer, and 1 to 10% by mass. A range is particularly preferred.

The reflective film of the present invention may be charged during processing (the reflective film is punched, molded and incorporated in the backlight), and there may be a problem that charged dust or dust existing in the vicinity 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 (for example, tin oxide, antimony-doped tin oxide (ATO), indium oxide, tin-doped indium oxide, etc.) ).

In the resin layer according to the present invention, various additives can be further added within a range that does not impair the effects of the present invention. Examples of the additive include a fluorescent brightening agent, a heat stabilizer, an oxidation stabilizer, an organic lubricant, a coupling agent, a dye, and a pigment.

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. That is, it is the thickness of the portion where there is no protrusion due to particles.

When the thickness of the resin layer is less than 0.3 μm, the polyethylene particles may fall off, whereas when the thickness of the resin layer exceeds 20 μm, the convex portions due to the polyethylene particles may not be sufficiently formed.

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 the occurrence of uneven white spots), the average particle diameter of polyethylene particles contained in the resin layer ( The ratio (r / d) between r: μm) and 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 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 Nippon Microtome Research Co., Ltd. The obtained film cross section was observed using a scanning electron microscope (S-3400N, manufactured by Hitachi, Ltd.), and not the portion where the convex portion due to the particle exists on the surface of the resin layer, but the convex portion due to the particle on the surface of the resin layer. The thickness of 5 portions where no portion exists is measured, and the average value is taken as the thickness of the resin layer.

The present invention includes a mode in which, as shown in FIG. 3A and FIG. 3B described above, particles are arranged in a plane on the surface of the resin layer almost without gaps to form convex portions. In this embodiment, the thickness of the resin layer is determined by measuring the distance from the surface of the substrate to the surface of the convex portion of the particles at five locations, and the average value is referred to as the thickness of the resin layer. In addition, when measuring the distance from the base material surface to the surface of the convex part by the particle, if the surface of the convex part region formed by the particle is covered with a resin (binder), the resin (binder covering) ) Including the distance. These aspects are preferable because part or all of the convex region formed by the particles can be covered with the resin contained in the resin layer, thereby preventing the particles from falling off. In other words, by adjusting the average particle diameter of the particles contained in the resin layer, the content ratio of the particles and the resin, or by adjusting the compatibility between the particles and the resin, one of the convex regions formed by the particles Part or all can be covered with a resin contained in the resin layer.

The resin layer can contain particles other than polyethylene particles (hereinafter referred to as “other particles”). When other particles are contained in the resin layer, the average particle size of the other particles is preferably smaller than the average particle size of the polyethylene particles. It is preferable for the resin layer to contain other particles having a relatively small average particle diameter, since the scratch resistance of the resin layer (which makes it difficult for scratches to enter) is improved.

The average particle diameter 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 that of the polyethylene particles. The lower limit is preferably 0.05 times or more, and more preferably 0.1 times or more. Specifically, the average particle diameter 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 other particles in the resin layer is preferably in the range of 10 to 200 parts by weight, more preferably in the range of 20 to 150 parts by weight, and particularly preferably in the range of 30 to 130 parts by weight with respect to 100 parts by weight of the polyethylene particles. .

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

In the reflective 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 only on 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 and drying a coating composition (coating liquid) containing at least a resin, polyethylene particles, and an organic solvent on a base film.

Any coating method can be used for coating the coating composition of the resin layer on the base film. 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. Moreover, the coating composition of the resin layer may be applied at the time of manufacturing the base film (in-line coating), or may be applied on the base film after completion of crystal orientation (off-line coating).

[Base film]
It does not specifically limit as a base film, Silver, the vapor deposition film of aluminum, the laminate film of silver foil or aluminum foil, a white film, a multilayer laminated film, etc. are mentioned.

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 therein is preferably used.

The white film is, for example, a film that is made white by adding a white colorant and / or air bubbles to a film made of a thermoplastic resin or the like.

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

The white film having air bubbles inside is not particularly limited, and examples thereof include a porous unstretched or biaxially stretched polypropylene film and a porous unstretched or stretched polyethylene terephthalate film. With respect to these production methods and the like, [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] and the like. Among them, the porous white biaxially stretched polyethylene terephthalate film disclosed in JP-A-2002-90515, or the porous white biaxially stretched polyethylene terephthalate film mixed and / or copolymerized with polyethylene naphthalate is preferably used.

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

In the three-layer configuration as described above, the A1 layer and the A2 layer may be configured with the same composition or may be configured with different compositions, but from the viewpoint of the productivity of the white film, It is preferable that A2 layer is comprised by the completely same composition. In the following description, the A1 layer and the A2 layer may be collectively referred to as “A layer”, and the expression “A layer” includes the two-layer A layer, the three-layer A1 layer, and the A2 layer. Is included. In the following description, the content of various materials contained in the A layer refers to the content per layer.

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

The layer A preferably contains particles. By including particles in the A layer, an appropriate slip property can be imparted to the reflective film. By imparting slipperiness to the reflective film, handling properties and workability (such as punching for forming a transmission portion (opening portion)) are improved.

As the 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 A layer is preferably 50% by mass or more, more preferably 60% by mass or more, and particularly preferably 70% by mass or more with respect to 100% by mass of the total resin constituting the A layer. The upper limit is about 99% by mass.

Examples of the particles contained in the A layer 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, polyacetic acids. Examples thereof include particles made of a resin such as a vinyl resin, a fluorine 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, titanium mica, talc, clay, kaolin, fluoride. And lithium fluoride and calcium fluoride.

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 size 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 particles in the A layer is preferably 0.005% by mass or more, and more preferably 0.01% by mass or more with respect to 100% by mass of the total amount of the A layer. The upper limit content is preferably 20% by mass or less, more preferably 10% by mass or less, and particularly preferably 5% by mass or less with respect to 100% by mass of the total amount of the A layer. When the content of the particles is less than 0.005% by mass, good sliding properties may not be obtained. On the other hand, when the content of the particles exceeds 20% by mass, the film forming property may be deteriorated.

The B layer is preferably a layer that is whitened by containing fine bubbles inside the film layer. The layer B is preferably a porous unstretched or biaxially stretched polypropylene film or a porous unstretched or stretched polyethylene terephthalate film. As described above, the method for producing the film layer (B layer) containing bubbles in the inside is disclosed in, for example, JP-A-8-262208, JP-A-2002-90515, JP-A-2002-138150, etc. 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 particularly preferably made of a polyester resin. As the polyester resin constituting the B layer, 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 B layer is preferably 50% by mass or more, more preferably 60% by mass or more, and particularly preferably 70% by mass or more with respect to 100% by mass of the total amount of the B layer. The upper limit is about 95% by mass.

Formation of air bubbles in the B layer can be achieved, for example, by finely dispersing a resin incompatible with the polyester resin in a polyester film that is a film substrate and stretching (for example, biaxial stretching).

The B layer is preferably mixed with a polyester resin constituting the B layer in an incompatible resin (hereinafter sometimes referred to as an incompatible resin). The inclusion of the incompatible resin is preferable because a cavity having the incompatible resin as a nucleus is formed at the time of stretching, and light reflection occurs at the cavity interface. The resin incompatible with the polyester resin may be a homopolymer or a copolymer. Polyolefin resin such as polyethylene, polypropylene, polybutene, polymethylpentene, cyclic polyolefin resin, polystyrene resin, polyacrylate Resins, polycarbonate resins, polyacrylonitrile resins, polyphenylene sulfide resins, fluororesins, and the like are preferably used. Two or more of these may be used in combination.

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

The preferable content of the incompatible resin contained in the B layer is 5% by mass or more and 25% by mass or less with respect to 100% by mass of the total amount of the B layer. In addition, the incompatible resin contained in the B layer is dispersed in a matrix made of a polyester resin with a number average particle diameter of 0.4 μm or more and 3.0 μm or less. It is preferable in obtaining. Furthermore, the number average particle diameter of the incompatible resin is more preferably in the range of 0.5 μm or more and 1.5 μm or less.

The number average particle diameter here is a cross section of the film in the width direction (TD), and the B layer portion of the cross section is a scanning electron microscope (FE-SEM) model S-2100A manufactured by Hitachi, Ltd. The average value of the diameters when the area of 100 particles observed in this way is obtained and converted to 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 that can be contained in the A layer. Among these particles, inorganic particles such as calcium carbonate, barium sulfate, and titanium dioxide that absorb less in the visible light range of wavelength 400 to 700 nm are preferable from the viewpoints of reflection characteristics, concealability, production cost, and the like. In the present invention, barium sulfate and titanium dioxide are most preferable from the viewpoints of film winding property, long-term film-forming stability, and improvement in reflection characteristics. The average particle diameter of the particles is preferably in the range of 0.1 to 3 μm. Use of such inorganic particles is preferable because the reflectivity and concealability 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 with respect to 100% by mass of the total amount of the B layer, from the viewpoint of ensuring good reflection characteristics and concealment. More preferred is 1% by mass or more. On the other hand, when the content of such inorganic particles increases, the transmission yellowness (YI) of the reflective sheet tends to increase. Therefore, the upper limit content of the inorganic particles is preferably 10% by mass or less, and 5% by mass. The following is more preferable, and 3% by mass or less is particularly preferable.

The B layer preferably further contains a copolyester. By containing the copolyester in the B layer, it is possible to stably form a film even when the B layer contains a relatively high concentration of inorganic particles. The copolyester also has a role as a dispersant for the incompatible resin in the B layer.

Examples of such a copolyester include a copolymer of polyethylene terephthalate and isophthalic acid, a copolymer of polyethylene terephthalate and cyclohexanedimethanol, a copolymer of polybutylene terephthalate and polytetramethylene terephthalate, and the like. In this invention, it is preferable to contain at least 2 types chosen from the group which consists of these copolyesters.

When the white film has a two-layer structure, 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 The range of layer = 3: 97 to 10:90 is more preferable.

When 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. Furthermore, 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 Films Co., Ltd.) and the like. As a white film having a three-layer structure," Lumirror "(registered trademark) E60L, E6SL, E6SR, E6SQ, E6Z, E80A , E85D (manufactured by Toray Industries, Inc.), “Tetron” (registered trademark) film UX, UXE, UXS7, UXQ1 (manufactured by Teijin DuPont Films, Inc.), Lumirex II (manufactured by Mitsubishi Plastics, Inc.), and the like. Moreover, as an example of a white film having a configuration other than these, Optilon ACR3000, ACR3020 (manufactured by DuPont), “MCPET” (registered trademark) (manufactured by Furukawa Electric Co., Ltd.) can be mentioned.

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

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

As described above, the edge light type backlight system has a problem of damaging the light guide plate due to contact between the light guide plate and the reflective film, and white spot unevenness due to adhesion between the light guide plate and the reflective film. However, these problems are alleviated by using the reflective film of the present invention.

In addition, as described above, a specific problem (problem that the light guide plate is contaminated by heat) when using polyethylene particles that are conventionally known in the resin layer is the reflective 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, evaluation method, and material in a present Example are shown below.

[Measurement method and evaluation method]
(1) Confirmation of polyethylene particles in resin layer Using a stereomicroscope (SMK1500, manufactured by Nikon), adjust the magnification at 20 to 200 times and observe the surface of the resin layer with a metal jig. The contained particles were sampled and used as samples to be measured.

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

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

(2) Melting | fusing point measurement of polyethylene particle Using the differential scanning calorimeter (DSC) (the Seiko Electronics Co., Ltd. make, RDC220), it measured and analyzed based on JISK7121-1987. Using a 5 mg particle sample, 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 taken as the melting point. When there were a plurality of vertices of the melting endothermic peak, the temperature indicated by the vertex having the smallest value in the vertical axis direction (vertex located on the most endothermic side) was taken as the melting point.

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

(4) Measurement of viscosity average molecular weight of polyethylene particles The intrinsic viscosity [η] and viscosity average molecular weight (Mv) were measured according to JIS K7367-3 (1999).
20 mL of decalin (containing 1 g / L of dibutylhydroxytoluene (BHT)) was charged with 20 mg of polyethylene particles and stirred at 150 ° C. for 2 hours to dissolve the polyethylene particles. The solution was measured at a constant temperature of 135 ° C. using a Canon-Fenske viscometer (SO) for the drop time (ts) between the marked lines. In addition, the fall time (tb) of only decalin which did not melt | dissolve polyethylene particles as a blank was measured. The specific viscosity (ηsp / C) of polyethylene was plotted according to the following formula, 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 formula.
Mv = (5.37 × 10 ⁴ ) × [η] ^1.37

(5) Average particle diameter of polyethylene particles contained in the resin layer The reflective film was cut in a direction perpendicular to the film plane at a knife inclination angle of 3 ° using a rotary microtome manufactured by Nippon Microtome Laboratories. . 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 larger, otherwise 1,000 times). The maximum length of each of 30 particles randomly selected with respect to the particles contained in the layer was measured, and the average value of these was taken as the average particle diameter of the particles. Here, the maximum length of a particle is a square or rectangle having the smallest area that completely surrounds one particle (that is, a square or rectangle in which the particle is in contact with the four sides of the square or 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 constant tangent diameter was taken as the maximum length of the particle).

(6) Resin Layer Thickness The reflective film was cut in a direction perpendicular to the film plane at a knife inclination angle of 3 ° using a rotary microtome manufactured by Nippon Microtome Research 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 of five portions where no convex portions due to particles exist on the surface of the layer was measured, and the average value was taken as the thickness of the resin layer.

In the case where the surface of the resin layer as shown in FIG. 3 is covered with particles, the distance from the substrate surface to the surface of the convex portion by the particles is measured at five locations, and the average value of the resin layer surface is It is called thickness. In addition, when measuring the distance from the base material surface to the surface of the convex part by the particle, if the surface of the convex part region formed by the particle is covered with a resin (binder), the resin (binder covering) ) Including the distance.

(7) Evaluation of slipperiness The coefficient of kinetic friction between the resin layer surface of the reflective film and the acrylic plate (“Sumipex” (registered trademark) E (clear) ”3 mm thickness manufactured by Sumitomo Chemical Co., Ltd.) is defined in JIS K7125 (1999). In conformity, the measurement was performed using a Toray Co., Ltd. type slip tester 200G-15C (manufactured by MAKINO SEISAKUSHO) produced 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 reflection film shall be the moving direction (direction in which the relative displacement movement between the contact surface of the acrylic plate and the reflective film) is made, and the contact surface of the acrylic plate and the reflective film at the following moving speed The relative displacement between them was made. The dynamic friction coefficient in this evaluation was calculated from the frictional force at the point moved 100 mm after starting the relative displacement movement between the contact surfaces of the acrylic plate and the reflective film.

<Measurement conditions>
Reflective film size: 80mm x 200mm
Acrylic plate size: 150mm x 300mm
Slide piece size, mass: 63mm x 63mm, 200g
Movement 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 film, each resin layer surface and the other resin layer surface were evaluated. The dynamic friction coefficient thus obtained 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 less than or equal to 0.6.
B: The dynamic friction coefficient is larger than 0.6.

(8) Heat resistance evaluation 1 (discoloration due to heat)
The reflective film was heated in an atmosphere at a temperature of 60 ° C. for 500 hours and then allowed to stand at room temperature for 1 hour, and the discoloration of the resin layer surface of the reflective film was visually evaluated according to the following criteria.
A: There is no discoloration.
B: Discoloration is recognized.

(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 (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, three optical films, a light guide plate (acrylic plate, 3.5 mm thickness, height of the convex portion formed on the light guide plate 12 μm) and the reflective film were taken out from the backlight A, and the reflective film of the present invention was mounted. Cut into the same shape and size as the reflective film. After preparing the sample cut for each reflective film, install the cut sample resin layer side facing the light guide plate instead of the mounted reflective film, and disassemble the light guide plate and three optical films Installed in the same order and direction as before.

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

(10-1) Evaluation of damage (scratch damage) of the light guide plate 1
Samples were prepared for each reflective film, and the resin layer surface of the reflective film was in contact with the surface of the light guide plate provided with the projections obtained by disassembling a 40-inch liquid crystal television (manufactured by Samsung, PAVV UN40B7000WF). 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) The surface 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 scratches are 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 observed under a load of 50 gf / cm ² .

(10-2) Evaluation of damage to light guide plate (transfer contamination of particle shavings) Part 2
After laminating a 40-inch liquid crystal television (manufactured by Samsung, PAVV UN40B7000WF) so that the surface of the light guide plate provided with the convex portion is laminated so that the surface of the resin layer of the reflective film is in contact, 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 particles contained in the reflective film are transferred onto the surface of the light guide plate and transferred to the light guide plate. Whether it was contaminated was visually observed and evaluated according to the following criteria.
A: There is no contamination.
B: Contaminated.

(11) Evaluation of white spot unevenness (attachment of reflective film and light guide plate) Disassembling a 52-inch LCD TV (manufactured by Sony Corporation, “BRAVIA” (registered trademark) KDL-52EX700) and using LED as the 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. Further, 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 was mounted. did. After preparing a sample cut for each reflective film, install the cut reflective film so that the resin layer surface of the cut reflective film faces the light guide plate instead of the mounted reflective film, before disassembling the light guide plate and the three optical films. Installed in the same direction and direction.
The liquid crystal television was turned on, and white spot unevenness was visually observed according to the following criteria.
S: A white spot is not observed.
A: A white point is slightly observed, but it is an acceptable level.
B: A white spot is clearly observed.

(12) Evaluation of application property of resin layer The resin layer applied on the base film was visually observed, and the degree of occurrence of streaky unevenness was evaluated according to the following criteria.
S: Streaky unevenness is not recognized.
A: Thin streaky irregularities are observed.
B: Streaky unevenness is clearly recognized.

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

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

<Particle (a); particle made of a homopolymer of ethylene having a viscosity average molecular weight exceeding 100,000>
“Miperon” (registered trademark) XM-220 manufactured by Mitsui Chemicals, Inc., density 940 kg / m ³ , viscosity average molecular weight 2 million

<Particle (b): Particle made of a homopolymer of ethylene having a viscosity average molecular weight exceeding 100,000>
“Miperon” (registered trademark) XM-221U manufactured by Mitsui Chemicals, Inc., density 940 kg / m ³ , viscosity average molecular weight 2 million,

<Particle (c): Particle made of a homopolymer of ethylene having a viscosity average molecular weight exceeding 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 made of a homopolymer of ethylene having a viscosity average molecular weight exceeding 100,000>
“Miperon” (registered trademark) XM-330 manufactured by Mitsui Chemicals, Ltd., density 940 kg / m ³ , viscosity average molecular weight 2 million

<Particle (e); High-density polyethylene particle>
“Flow beads” (registered trademark) HE-3040 manufactured by Sumitomo Seika Co., Ltd., density 961 kg / m ³ , viscosity average molecular weight 450,000

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

<Particle (g); Low density polyethylene particle>
“Flocene” (registered trademark) UF20 manufactured by Sumitomo Seika Co., Ltd., density 921 kg / m ³ , viscosity average molecular weight 150,000

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

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

<Particle (j); Polyethylene wax particles>
“Celidust” (registered trademark) 3620 manufactured by Clariant, viscosity average molecular weight 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]
Using a bar coater, apply the following resin layer coating solution on one side of a white film (“Lumirror” (registered trademark) E6SQ: 300 μm thickness) manufactured by Toray Industries, Inc.) so that the resin layer thickness is about 3 μm. And it dried at 100 degreeC and laminated | stacked the resin layer, and produced the reflective film.

<Resin layer coating solution>
70 parts by mass of a benzotriazole-containing acrylic copolymer resin (“HALS HYBRID” (registered trademark) UV-G720T concentration 40 mass% solution manufactured by Nippon Shokubai Co., Ltd.), particles a (“Miperon” manufactured by Mitsui Chemicals, Inc.) (Registered trademark) XM-220, viscosity average molecular weight 2 million) 12 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 Then, 55 parts by mass of ethyl acetate was added with stirring to prepare a coating solution.

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

[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 liquid of Example 1 were changed to the particles shown in Table 1. In addition, Example 4 was applied so that the resin layer thickness was about 6 μm.

[Example 6]
A reflective film was produced in the same manner as in Example 1 except that the following resin layer coating solution was used.
<Resin layer coating solution>
Benzotriazole-containing acrylic copolymer resin (“HALS HYBRID” (registered trademark) UV-G720T 40% by weight solution manufactured by Nippon Shokubai Co., Ltd.) 50 parts by mass, particle a (“Miperon” manufactured by Mitsui Chemicals, Inc.) (Registered trademark) XM-220, viscosity average molecular weight 2 million 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 Then, 67 parts by mass of ethyl acetate was 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 with respect to 100% by mass of the total solid content contained in the coating solution is 47.6% by mass, and the content ratio of the resin is 47.6% by mass.

[Example 7]
A reflective film was produced in the same manner as in Example 1 except that the following resin layer coating solution was used.
<Resin layer coating solution>
Benzotriazole-containing acrylic copolymer resin (manufactured by Nippon Shokubai Co., Ltd. “HALS HYBRID” (registered trademark) UV-G720T concentration 40 mass% solution) 85 parts by mass, particles a (“Miperon” manufactured by Mitsui Chemicals, Inc.) (Registered trademark) XM-220, viscosity average molecular weight 2 million) 6 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 Then, 46 parts by mass of ethyl acetate was 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 with respect to 100% by mass of the total solid content contained in the coating liquid is 14.3% by mass, and the content ratio of the resin is 81.0% by mass.

[Example 8]
A reflective film was produced in the same manner as in Example 1 except that the following resin layer coating solution was used.
<Resin layer coating solution>
Benzotriazole-containing acrylic copolymer resin (“HALS HYBRID” (registered trademark) UV-G720T 40% by mass solution manufactured by Nippon Shokubai Co., Ltd.) 16 parts by mass, particle a (“Mipperon” manufactured by Mitsui Chemicals, Inc.) (Registered trademark) XM-220, 33.6 parts by mass of viscosity average molecular weight 2 million, isocyanate-based crosslinking agent (“Coronate” (registered trademark) HL manufactured by Nippon Polyurethane Industry Co., Ltd., concentration 75% by mass) 2.7 Mass parts 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 with respect to 100% by mass of the total solid content contained in the coating solution is 80.0% by mass, and the content ratio of the resin is 15.2% by mass.

[Example 9]
A reflective film was produced in the same manner as in Example 1 except that the following resin layer coating solution was used.
<Resin layer coating solution>
26.5 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 (manufactured by Mitsui Chemicals, Inc.) 29.4 parts by weight of Mipperon (registered trademark) XM-220, viscosity average molecular weight 2 million, isocyanate cross-linking agent (“Coronate” (registered trademark) HL, concentration 75% by mass, manufactured by Nippon Polyurethane Industry Co., Ltd.) 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. Moreover, the content ratio of the particles with respect to 100% by mass of the total solid content contained in the coating solution is 70.0% by mass, and the content ratio of the resin is 20.2% by mass.

[Example 10]
A reflective film was produced in the same manner as in Example 1 except that the following resin layer coating solution was used.
<Resin layer coating solution>
96.8 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 (manufactured by Mitsui Chemicals, Inc.) MIPERON "(registered trademark) XM-220, viscosity average molecular weight 2 million) 1.3 parts by mass, 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 with respect to 100% by mass of the total solid content contained in the coating solution is 3.0% by mass, and the content ratio of the resin is 92.2% by mass.

[Example 11]
A reflective film was produced in the same manner as in Example 1 except that the following resin layer coating solution was used.
<Resin layer coating solution>
94.8 parts by mass of a benzotriazole-containing acrylic copolymer resin (“HALS HYBRID” (registered trademark) UV-G720T concentration 40 mass% solution manufactured by Nippon Shokubai Co., Ltd.), particles a (manufactured by Mitsui Chemicals, Inc.) "Miperon" (registered trademark) XM-220, viscosity average molecular weight 2 million) 2.1 parts by mass, isocyanate-based cross-linking agent ("Coronate" (registered trademark) HL manufactured by Nippon Polyurethane Industry Co., Ltd., concentration 75 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 with respect to 100% by mass of the total solid content contained in the coating solution is 5.0% by mass, and the content ratio of the resin is 90.3% by mass.

[Example 12]
A reflective film was produced in the same manner as in Example 1 except that the following resin layer coating solution was used.
<Resin layer coating solution>
Benzotriazole-containing acrylic copolymer resin (manufactured by Nippon Shokubai "Hals Hybrid" (registered trademark) UV-G720T concentration 40 mass% solution) 86.3 parts by mass, particles a (manufactured by Mitsui Chemicals, Inc.) "Miperon" (registered trademark) XM-220, viscosity average molecular weight 2 million) 3.4 parts by mass, nylon particles (SP10 manufactured by Toray Industries, Inc.) 2.1 parts by mass, isocyanate 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 with respect to 100% by mass of the total solid content contained in this coating solution is 8.1% by mass, the content ratio of nylon particles is 5.0% by mass, and the content ratio of resin is 82.2% by mass. It is.

[Examples 13 to 18]
In Examples 6, 7, and 9 to 12, reflective films were produced in the same manner except that the particle a of the resin layer coating solution was changed to particles e. In addition, Example 6 corresponds to Example 13, and similarly, Example 7 is Example 14, Example 9 is Example 15, Example 10 is Example 16, Example 11 is Example 17, Example 12 Corresponds to Example 18, respectively. Furthermore, in Example 18, the nylon particles (SP10) of Example 12 were changed to nylon particles (SP500).

[Evaluation]
About the reflective film produced by said Example and comparative example, the measurement and evaluation which were mentioned above were performed. The results are shown in Tables 1 and 2.
In addition, it was confirmed that the convex part by particle | grains exists in the resin layer surface in any of an Example and a comparative example.

In all the examples of the present invention, heat resistance 1 (no discoloration due to heat) and heat resistance 2 (no light guide plate contamination due to heat) are good, and the light guide plate is damaged and white spots are uneven. Occurrence is suppressed. Moreover, all of the examples of the present invention have good slipping property and coating property.

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 (the light guide plate is not contaminated by heat). Moreover, since Comparative Example 1 and 2 are inferior in slipperiness, particle | grains are shaved by contact with a light-guide plate, are transcribe | transferred to a light-guide plate, and the light-guide plate is contaminated. Further, Comparative Examples 1 and 2 are inferior in applicability and cause streaky irregularities. Further, Comparative Examples 1 and 2 are inferior in white spot unevenness evaluation.

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

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

Comparative Example 5 using polyethylene wax particles (viscosity average molecular weight less than 10,000) is inferior in heat resistance 2 (the light guide plate is not contaminated by heat). In Comparative Example 5, since the slipperiness is inferior, the particles are scraped by contact with the light guide plate and transferred to the light guide plate to contaminate the light guide plate. Moreover, the comparative example 5 is inferior in applicability | paintability, and there exists generation | occurrence | production of streaky irregularity. Moreover, the comparative example 5 is inferior in evaluation of a white spot nonuniformity.

The reflective film according to the present invention can be applied to any reflective film that is required to suppress sticking to a member (contact member) that comes into contact with the reflective film, to prevent 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 (8)

1. A reflective film comprising 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 reflective film according to claim 1, wherein the density of the polyethylene particles is 942 kg / m ³ or more.
3. The reflective film according to claim 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 claims 1 to 3, wherein a coefficient of dynamic friction between the surface having the resin layer on at least one surface of the reflective film and the acrylic plate is 0.6 or less.
5. 5. The reflective film according to claim 1, wherein the content of the polyethylene particles in the resin layer is 3 to 75% by mass with respect to 100% by mass of the total resin layer.
6. 6. The reflective film according to claim 1, wherein the base film is a film having at least air bubbles inside.
7. The reflective film according to any one of claims 1 to 6, wherein the base film is a film in which a film layer (A layer) is laminated on both surfaces of a film layer (B layer) containing bubbles inside.
8. An edge light type backlight unit, wherein the reflective film according to any one of claims 1 to 7 is disposed so that the surface having the resin layer faces the light guide plate.

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