JP2017134380A - Reflection film for edge light type backlight and backlight for liquid crystal display using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a reflection film that has suppressed adhesion between the reflection film and a contact member (for example, light guide plate) and has suppressed damage to particles.SOLUTION: There is provided a reflection film for an edge light type backlight including a particle-containing layer containing particles at least on a single side of a base material film, and satisfies the following (i) and (ii). (i) The aspect ratio of the particles is 1.06 to 1.30. (ii) The average particle diameter of the particles is 15 to 100 μm.SELECTED DRAWING: Figure 1

Description

The present invention relates to a reflective film for improving luminance unevenness of a liquid crystal backlight. More particularly, the present invention relates to a reflection film suitably used for an edge light type backlight, a surface light source for illumination such as a signboard / vending machine, and a backlight for a liquid crystal display using the same.

  In the liquid crystal display, a backlight for illuminating the liquid crystal cell is used. Conventionally, depending on the type of liquid crystal display, a relatively small liquid crystal monitor employs an edge light type backlight, while a relatively large liquid crystal television employs a direct type backlight. As these reflective films for a backlight, a white film formed porous by air bubbles is generally used (Patent Document 1). Moreover, as a film suitably used with a light guide plate having a prism shape, a reflective film in which a layer containing soft beads is laminated on a base sheet layer has been developed (Patent Documents 2 and 3).

  With the thinning of liquid crystal televisions from around 2009, edge-light type backlights have been adopted in liquid crystal televisions, and at the same time, development related to edge-light type backlights has been vigorously carried out. Furthermore, light emitting diodes (hereinafter abbreviated as LEDs) are being adopted as light sources in order to reduce power consumption and make mercury free.

  Unlike a notebook computer or desktop monitor, a television is required to have high brightness, and a large number of LEDs must be arranged. Therefore, it was necessary to create a case using aluminum with a high thermal conductivity coefficient and take measures for heat dissipation. However, when aluminum is employed, mechanical strength tends to be poor. Therefore, for example, as shown in FIG. 1, it has been necessary to form irregularities on the back housing 4 by drawing. The unevenness was also intended to save space by arranging a circuit or the like in the recess for thinning.

  Moreover, a light guide plate is indispensable as an optical member in the edge light type backlight. With respect to the light guide plate, a conventional notebook personal computer or desktop monitor has a size of about 25 inches, but a TV needs a 30 to 60 inches. Therefore, a light guide plate having a convex portion obtained by printing a circle or a dot on an acrylic plate (3 to 4 mm thickness), a light guide plate having a concave portion by laser processing or UV transfer method, and the like have been developed.

The large edge light type backlight has a structure in which the light guide plate and the reflective film are in direct contact with each other. Therefore, there are the following problems (1) to (5) as problems in the structure.
(1) The problem is that the light guide plate and the reflective film are non-uniformly adhered to cause uneven brightness.
(2) The problem is that the reflective film rises due to local convex portions generated due to poor molding of the back housing, and the reflective film is in strong contact with the light guide plate, resulting in scratches on the light guide plate and uneven brightness.
(3) In a TV vibration test, the light guide plate and the reflective film rub against each other, scratching the light guide plate and causing uneven brightness.
(4) In a backlight using a convex light guide plate, as a result of the convex portions formed on the reflective film being compressed by the convex portions of the light guide plate, the light guide plate and the reflective film are non-uniformly adhered and white spots (dots) The problem of generating a brightly visible part).
(5) In a backlight using a convex light guide plate, the convex portion formed on the reflective film is broken by the convex portion of the light guide plate, and the broken pieces adhere to the light guide plate side, thereby causing white spot unevenness (in the form of dots) The problem of generating brightly visible parts).

  The problems (1) to (4) have been solved by defining the rigidity of the reflective film, the height of the surface protrusion, and the hardness and type of particles contained in the surface protrusion within an appropriate range (Patent Literature). 4-6).

JP-A-8-262208 JP 2003-92018 A Special table 2008-512719 gazette Japanese Patent No. 5578177 Japanese Patent No. 5218931 Japanese Patent Laying-Open No. 2015-69020

However, the thinning of the light guide plate (thinning from 4 mm to 2 mm) for the purpose of thinning the backlight and making the curved surface has progressed recently, and the convex portion formed on the reflective film described in the above problem (5) However, the problem of being broken by the convex portions of the light guide plate has become a major issue. The cause is the following problems (i) to (ii) in the backlight structure as the light guide plate is made thinner and curved.
(I) Increase in load on the reflective film due to increased deflection of the light guide plate due to thermal expansion.
(Ii) The fixing pressure of the optical film of the backlight is increased to suppress the deflection of the light guide plate, and the contact pressure between the light guide plate and the reflective film is increased.

  Therefore, the object of the present invention is to suppress the sticking of the reflective film and the light guide plate and the scratch of the light guide plate, and further suppress the damage of the particles on the surface of the reflective film (a phenomenon in which part of the particles are scraped off). It is to provide a reflective film. Another object of the present invention is to provide an edge light type backlight using the reflective film according to the present invention.

The present invention employs the following means in order to solve such problems.
(1) An edge-light-type reflective film for backlight having a particle-containing layer containing particles on at least one surface of the substrate film and satisfying the following (i) and (ii).
(I) The aspect ratio of the particles is 1.06 to 1.30.
(Ii) The average particle diameter of the particles is 15 to 100 μm.
(2) The reflective film for an edge light type backlight according to (1), wherein the particles are particles containing an aromatic polyester and / or particles containing polyamide.
(3) A backlight for a liquid crystal display, comprising the reflective film for an edge light type reflective backlight according to (1) or (2) and having a light emitting diode as a light source.

  According to the present invention, sticking between a reflective film and a contact member (for example, a light guide plate) is suppressed, and particle damage on the surface of the reflective film is suppressed. Moreover, according to the preferable aspect of this invention, the damage of the contact member by a reflective film and a contact member (for example, light-guide plate) contacting is suppressed.

  In this invention, the member (contact member) which contacts a reflective film is not specifically limited, A contact member is suitably selected according to the use and intended purpose of a reflective film.

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

It is a schematic diagram which shows one embodiment of the large sized edge light type backlight which uses LED as a light source. It is a related schematic diagram of the light-guide plate which has a convex part, a reflective film, and a back housing | casing. It is the side view which showed typically the method of evaluating the damage of the particle | grains in the reflective film surface.

  The reflective film of the present invention has a particle-containing layer containing particles on at least one surface of the base film.

  Hereafter, each structural component which comprises this invention is demonstrated in detail.

[Base film]
When the base film according to the present invention is used as a reflective film for backlights or lighting applications, the higher the visible light reflectance, the better. For this purpose, a white film containing bubbles and / or incompatible particles therein is preferably used. Examples of these white films include, but are not limited to, polyolefins and polyesters such as porous unstretched or biaxially stretched polypropylene films, porous unstretched or stretched polyethylene terephthalate films, and the like. In particular, polyesters are preferably used from the viewpoint of moldability and productivity.

  About these manufacturing methods etc., paragraphs [0034] to [0057] of JP-A-8-262208, paragraphs [0007] to [0018] of JP-A-2002-90515, and JP-A-2002-138150. It is disclosed in detail in paragraphs [0008] to [0034]. Among them, the porous white biaxially stretched polyethylene terephthalate film disclosed in JP-A-2002-90515 can be preferably used as the base film according to the present invention for the reasons described above.

  More preferably, it is a porous white biaxially stretched polyethylene terephthalate film mixed and / or copolymerized with polyethylene naphthalate from the viewpoint of heat resistance and reflectance. Most preferably, a porous white biaxially stretched polyethylene terephthalate film containing inorganic particles can be used in order to improve the flame retardancy of the porous white biaxially stretched polyethylene terephthalate film itself.

  The content of the inorganic particles contained in the porous white biaxially stretched polyethylene terephthalate film is preferably 2% by mass or more, more preferably 7%, based on the total mass of the porous white biaxially stretched polyethylene terephthalate film. It is at least 30% by mass, most preferably at least 30% by mass.

  The structure of the substrate film according to the present invention may be appropriately selected depending on the intended use and required characteristics, and is not particularly limited, but is a single layer having at least one layer and / or two or more layers. The composite film is preferable, and it is preferable that at least one layer thereof contains bubbles and / or inorganic particles.

  An example of a single layer configuration (= 1 layer) is, for example, a substrate film having only a single A layer, and includes a configuration in which the A layer contains inorganic particles and / or bubbles. The content of the inorganic particles is preferably 2% by mass or more, more preferably 7% by mass or more, and most preferably 10% by mass or more with respect to the total mass of the base film.

  An example of a two-layer structure is a base film having a two-layer structure of A layer / B layer in which a B layer is laminated on the A layer, and at least one of these A and B layers is inorganic. The thing of the structure containing particle | grains and / or air bubbles is mentioned. The content of the inorganic particles is preferably 2% by mass or more, more preferably 7% by mass or more, and most preferably 30% by mass or more based on the total mass of the base film, that is, the total mass of the two layers. .

  Furthermore, as an example of a three-layer structure, as described above, a base film having a three-layer laminated structure in which three layers of A layer / B layer / A layer and A layer / B layer / C layer are laminated, The thing of the structure which contained the inorganic particle and / or the bubble in at least 1 layer of each layer is mentioned. As described above, the content of the inorganic particles is preferably 2% by mass or more, more preferably 7% by mass or more, and further preferably 30% by mass or more with respect to the total mass of the base film. In the case of a three-layer configuration, the B layer is most preferably a layer containing bubbles from the viewpoint of productivity.

  The number average particle diameter of the inorganic fine particles contained in the base film is preferably 0.3 to 2.0 μm.

  Examples of the 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, lithium fluoride, calcium fluoride, or the like can be used.

  Next, although the manufacturing method of the white base film of 3 layer structure among the said base films is demonstrated, it is not limited to this example.

First, polymethylpentene is added as an incompatible polymer, and polyethylene glycol, polybutylene terephthalate and polytetramethylene glycol copolymer as a low specific gravity agent are added into polyethylene terephthalate. The mixture is sufficiently mixed and dried, and then supplied to the extruder B heated to a temperature of 270 to 300 ° C. Polyethylene terephthalate containing inorganic and / or organic additives such as BaSO ₄ , CaCO ₃ and TiO ₂ is supplied to the extruder A by a conventional method. Then, in the T-die three-layer die, the polymer of the extruder B is arranged on the inner layer (B layer), and the polymer of the extruder A is arranged on both surface layers (A layer), so that A layer / B layer / A layer Laminated in three layers of the structure.

  The melt-laminated sheet is closely cooled and solidified by electrostatic force on a drum cooled to a drum surface temperature of 10 to 60 ° C. to obtain an unstretched film. The unstretched film is guided to a roll group heated to 80 to 120 ° C., longitudinally stretched 2.0 to 5.0 times in the longitudinal direction, and cooled with a roll group of 20 to 50 ° C. Subsequently, the film is stretched in the direction perpendicular to the longitudinal direction in an atmosphere heated to 90 to 140 ° C. while being guided to a tenter while gripping both ends of the longitudinally stretched film with clips. In this case, the stretching ratio is 2.5 to 4.5 times in the longitudinal and lateral directions, and the area ratio (longitudinal stretching ratio x lateral stretching ratio) is preferably 9 to 16 times. That is, when the area magnification is less than 9, the resulting film may have insufficient whiteness. On the other hand, if the area magnification exceeds 16 times, tearing tends to occur at the time of stretching, and the film forming property may deteriorate. In order to impart flatness and dimensional stability to the biaxially stretched film in this manner, heat setting is performed at 150 to 230 ° C. in a tenter, uniformly cooled, and further cooled to room temperature. The substrate film according to the present invention is obtained.

  What is marketed can be used as an example of this base film. 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.

[Method of forming particle-containing layer]
The method for forming the particle-containing layer in the present invention is not particularly limited, and examples thereof include a method in which an appropriate binder resin and particles are mixed in an appropriate solvent, applied to a substrate film, and then dried. .

[Average particle diameter]
In the present invention, the average particle size of the particles in the particle-containing layer containing particles is 15 μm to 100 μm. When the average particle diameter is in this range, it is easier to secure a gap with the light guide plate. When the average particle diameter is larger than 100 μm, the particles are likely to drop out, which may cause defects on the screen. On the other hand, if the average particle diameter is smaller than 15 μm, it may be difficult to secure a gap with the light guide plate which is the original purpose. From such a viewpoint, the range of the average particle diameter of the particles in the particle-containing layer containing particles is particularly preferably 20 to 50 μm.

[Aspect ratio of particles]
When the particle aspect ratio (major axis diameter / minor axis diameter) is 1.06 to 1.30, the effect of suppressing damage to the light guide plate is enhanced while ensuring a gap with the light guide plate, and the damage of the particles is reduced. Suitable for suppression. Such aspect ratio is preferably 1.20 or more, and preferably 1.25 or less. When the aspect ratio exceeds 1.30, the frequency of arranging the particles in the major axis direction of the particles increases with respect to the reflective film, and the particles may be damaged on the surface of the reflective film. On the other hand, when the aspect ratio is smaller than 1.06, the contact area of the light guide plate is reduced, so that the pressure applied to the particles increases and the particles may be easily damaged.

[Particle composition]
In the present invention, the particles contained in the particle-containing layer may be organic particles, inorganic particles, or organic-inorganic composite particles regardless of their types. From the viewpoint of easily satisfying the above-described particle mode, organic particles containing a polymer such as acrylic, aromatic polyester, polyurethane, polyamide, polyolefin, and polyether are preferable. From the viewpoint that the particles are not easily broken by the convex portions of the light guide plate, the particles are particularly preferably particles containing an aromatic polyester or particles containing polyamide, and a combination of both may be used.

  As the aromatic polyester, a polyester composed of a dicarboxylic acid component and a diol component is used. Examples of the dicarboxylic acid include terephthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, 4,4'-diphenyldicarboxylic acid, adipic acid, and sebacic acid. Examples of the diol include ethylene glycol, 1,4-butanediol, 1,4-cyclohexanedimethanol, and 1,6-hexanediol. Among these aromatic polyesters, polyethylene terephthalate and polybutylene terephthalate are preferable.

  As the particles containing polyamide, particles containing nylon resin are preferable, and particles containing nylon 6 are particularly preferable. Nylon 6 has a higher elastic modulus than nylon 12 and is less likely to cause particle damage.

  Of these particles, two or more particles having different particle materials may be used in combination.

[Ingredients other than particles in particle-containing layer]
The binder resin constituting the particle-containing layer is not particularly limited. 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, silicone resin and the like. Moreover, these resins may be used alone or in combination of two or more. Among them, polyester resin, polyurethane resin, acrylic resin and methacrylic resin are preferably used from the viewpoint of heat resistance, dispersibility of particles, applicability of coating liquid when forming a particle-containing layer by coating, and glossiness of the resulting reflective film. The In addition, the adhesion between the particles and the binder resin is important for improving the damage (shaving property) of the particles. When nylon 6 particles are used, it is more preferable to use a polyester resin as the binder resin.

  From the viewpoint of light resistance of the particle-containing layer containing particles, the particle-containing layer preferably contains an ultraviolet absorber and a light stabilizer. As the ultraviolet absorber and the light stabilizer, there are an inorganic type and an organic type. It does not specifically limit regarding the form to contain, You may mix the binder resin which forms this particle | grain containing layer, and an ultraviolet absorber or a light stabilizer. On the other hand, when it is desired to prevent the ultraviolet absorber or the light stabilizer from bleeding out of the particle-containing layer, it may be copolymerized with a binder resin monomer contained in the particle-containing layer. Moreover, you may make it chemically bond with the binder resin contained.

  As the inorganic ultraviolet absorber, titanium oxide, zinc oxide, and cerium oxide are generally known. Among them, at least one selected from the group consisting of zinc oxide, titanium oxide, and cerium oxide is difficult to bleed out, It is preferably used in terms of economy, light resistance, ultraviolet absorption, and photocatalytic activity. Such ultraviolet absorbers may be used in combination of several kinds as required. Of these, zinc oxide or titanium oxide is most preferable from the viewpoints of economy, ultraviolet absorption, and photocatalytic activity.

  Examples of organic ultraviolet absorbers include benzotriazole and benzophenone. In particular, benzotriazole can be suitably used because it contains nitrogen in the structure and thus has a function as a flame retardant, but is not particularly limited thereto. Since these ultraviolet absorbers only absorb ultraviolet rays and cannot capture organic radicals generated by ultraviolet irradiation, the radicals may cause the thermoplastic resin film of the base material to deteriorate in a chain manner. In order to capture these radicals and the like, a light stabilizer is preferably used in combination, and a hindered amine compound (HALS) is preferably used as the light stabilizer.

  When the ultraviolet absorber has a particle shape regardless of whether it is inorganic or organic, it can be used as a particle having a particle diameter of 25 to 50 μm or a particle having a particle diameter of 1 to 15 μm.

  Here, as a monomer that can be copolymerized to fix such an organic ultraviolet absorber or light stabilizer, vinyl monomers such as acrylic and styrene are highly versatile and economically preferable. Among these monomers, styrene-based vinyl monomers have an aromatic ring and therefore tend to yellow. In terms of light resistance, copolymerization with acrylic monomers is most preferably used.

  Further, as a reactive vinyl monomer substituted with benzotriazole, 2- (2′-hydroxy-5′-methacryloxyethylphenyl) -2H-benzotriazole (trade name: RUVA-93); Otsuka Chemical Co., Ltd. ))) Can be used. Further, as a combination of a hindered amine compound and a reactive vinyl monomer, 4-methacryloyloxy-2,2,6,6-tetramethylpiperidine (““ ADEKA STAB ”(registered trademark) LA-82”; ADEKA Corporation) Can be used.

  In the present invention, examples of such organic ultraviolet absorbers include resins containing organic ultraviolet absorbers such as benzotriazole and benzophenone, resins obtained by copolymerizing benzotriazole and benzophenone monomers, and hindered amines ( Resins containing and / or copolymerizing light stabilizers such as HALS-based reactive monomers can be used.

  Organic UV-absorbing resins containing a resin obtained by copolymerizing such benzotriazole-based and benzophenone-based reactive monomers, and further a resin copolymerized with a hindered amine (HALS) -based reactive monomer are more preferable because of their high UV absorbing effect. Of these, benzotriazole is particularly preferable because it contains nitrogen in the structure and also has a function as a flame retardant.

  These production methods and the like are disclosed in detail in paragraphs [0019] to [0039] of JP-A-2002-90515. In addition, “Hals Hybrid” (registered trademark) (manufactured by Nippon Shokubai Co., Ltd.) containing an acrylic monomer and ultraviolet absorber copolymer as an active ingredient can be used.

[Method of forming particle-containing layer]
Although the formation method in particular of a particle content layer is not restrict | limited, It is preferable to form a particle content layer by apply | coating the coating liquid containing particle | grains to a base film. In forming the particle-containing layer on at least one surface of the base film by coating, any method can be employed. For example, a coating solution containing a binder resin and particles in a solvent is a gravure coat, roll coat, spin coat, reverse coat, reverse kiss coat, bar coat, screen coat, blade coat, air knife coat, slit die coat, lip Examples of the method include applying at the time of manufacturing a base film using a variety of coating methods such as coating and dipping, and applying on the base film after completion of crystal orientation. The former application method is called in-line coating, and the latter application method is called off-line coating. When there is little restriction on the effective coating width and it is desired to flexibly respond to changes in product width, reverse kiss coating can be most preferably used.

  The solvent that can be used for mixing the binder resin and the particles constituting the particle-containing layer is preferably a liquid having a property of dissolving the binder resin. After the coating liquid is applied to the substrate film surface, the solvent is vaporized. Solvents include aromatic hydrocarbons such as toluene, xylene and styrene, ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone, alcohols such as methanol, isopropyl alcohol and isobutyl alcohol, chlorobenzene, and orthodichlorobenzene. Chlorinated aromatic hydrocarbons such as monochloromethane and monochloroethane, esters such as methyl acetate, ethyl acetate and butyl acetate, ethers such as ethyl ether and 1,4-dioxane, ethylene Examples include glycol ethers such as glycol monomethyl ether, alicyclic hydrocarbons such as cyclohexane, and aliphatic hydrocarbons such as normal hexane. Of these, aromatic hydrocarbon-based, ketone-based and ester-based organic solvents are preferable.

  The binder resin is not particularly limited as long as it dissolves, but methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, methyl acetate, ethyl acetate, and butyl acetate are preferable in terms of solubility, versatility, and cost. In addition, it is preferable to use a mixture of two or more solvents having different boiling points in that the drying speed can be adjusted.

[Other Additives Available for Base Film and Particle-Containing Layer]
Such a base film and a particle-containing layer can contain various additives. Examples of such additives include fluorescent brighteners, crosslinking agents, heat stabilizers, oxidation stabilizers, organic lubricants, antistatic agents, nucleating agents, dyes, pigments, fillers, dispersants, flame retardants and cups. There are ring agents.

[Application of reflective film]
The reflective film of the present invention is used for an edge light type backlight, and among them, it can be suitably used for an edge light type liquid crystal display backlight and an illumination surface light source such as a signboard or a vending machine.

  In addition, it can be suitably used as a reflection film constituting various surface light sources, a sealing film for solar cell modules that require reflection characteristics, and a back sheet. In addition, paper substitutes, ie cards, labels, stickers, home delivery slips, video printer paper, inkjet, barcode printer paper, posters, maps, dust-free paper, display boards, white boards, thermal transfer, offset printing, telephones Receiving sheet base materials used for various printing records such as cards and IC cards, building materials such as wallpaper, lighting equipment and indirect lighting equipment used indoors and outdoors, members mounted on automobiles, railways, aircraft, etc., circuit materials, etc. It can also be used as an electronic component.

[Edge light type backlight]
The reflective film of this invention is used suitably for an edge light type backlight. In the edge light type backlight, for example, the reflective film of the present invention and the light guide plate are incorporated in this order in a casing, and the reflective film is incorporated so that the particle-containing layer side faces the light guide plate. A light source such as an LED is installed at the edge portion of the light guide plate. Furthermore, an optical film such as a diffusion film or a prism film may be installed on the front surface of the light guide plate (the side opposite to the reflection film).

  By using the reflective film of the present invention for such an edge light type backlight, a good quality backlight with less luminance unevenness can be obtained.

  The size (rectangular diagonal length) of the backlight for a liquid crystal display using an LED as a light source that exhibits the effects of the present invention more effectively is 76.2 cm (30 inches) or more, preferably 88.9 cm. (35 inches) or more, more preferably 101.6 cm (40 inches) or more, and most preferably 127 cm (50 inches) or more.

  Moreover, it is preferable that the light guide plate is provided with a recess or projection of 3 μm or more on the surface of the light guide plate in the edge light type backlight. Furthermore, it is preferable that a concave or convex portion of 10 μm or more is provided.

The irregularities on the surface of the light guide plate are defined as follows.
(I) Take out the light guide plate arranged above the reflective film from the liquid crystal television.
(Ii) The light guide plate is cut into a 5 cm square, and any five sheets are taken out.
(Iii) Using a laser microscope VK-9700 manufactured by Keyence Co., Ltd., observation is performed with the magnification of the objective lens set to 20 times, and a portion detected at a height or depth of 1 μm or more is defined as surface irregularities.

  As the material of the light guide plate, for example, an acrylic resin, a resin obtained by mixing an acrylic resin and a styrene resin, a styrene resin, glass, or the like is used.

  The light guide plate 2 having the convex portions as shown in FIG. 2 subjected to dot printing is preferable in terms of production capacity. In addition, a light guide plate having a concave portion formed by laser processing or a light guide plate having a convex portion or a concave portion formed by molding using a mold or a roll is less likely to cause loss of light absorption or the like at the dot printing portion. Therefore, it is preferable in terms of high backlight luminance.

  As described above, such an edge light type backlight system has a problem of uneven white spots due to adhesion between the light guide plate and the reflective film, and damage to the surface of the reflective film due to the contact between the light guide plate and the reflective film. However, these problems are suppressed by using the reflective film obtained by the present invention.

  Hereinafter, the present invention will be described in more detail with reference to examples. The present invention is not limited to these examples. First, measurement methods and evaluation methods are shown below.

(1) Measurement of average particle diameter of particles While observing the surface of the reflective film with a stereomicroscope, a rotary microtome manufactured by Nippon Microtome Research Co., Ltd. is used and reflected through the center of gravity of the particles at a knife tilt angle of 3 °. Cut in a direction perpendicular to the film plane. The obtained reflecting film cross section was observed with a scanning electron microscope (S-3400N manufactured by Hitachi, Ltd.) (500 to 1,000 times), and the particle diameter of the particles was measured from the cross-sectional photograph. Here, on the image observed with a scanning electron microscope, the particle diameter is a square or rectangle having the smallest area completely surrounding one particle (that is, a square or rectangle in which particles are in contact with four sides), In the case of a rectangle, the length of one side (major axis diameter) in the case of a rectangle was defined as the particle diameter (that is, the longest constant tangent diameter was defined as the particle diameter). Arbitrary 30 points were measured and taken as the average particle size.

(2) Particle shape It evaluated by the procedure of the following (i) and (ii).
(I) Particle sampling Using a stereomicroscope (Nikon, SMZ1500), the particles contained in the particle-containing layer with a metal jig while appropriately observing the surface of the particle-containing layer while adjusting the magnification at 20 to 200 times. Sampling.
(Ii) Calculation of aspect ratio 30 particles randomly selected from the particles sampled in (i) above were observed with a scanning electron microscope (S-3400N manufactured by Hitachi, Ltd.) (500 to 1,000 times). did. Here, on the image observed with a scanning electron microscope, a square or rectangle having the smallest area completely surrounding one particle (that is, a square or rectangle in which particles are in contact with four sides) is drawn. In the case of a rectangle, the length of the long side is the major axis diameter, and the length of the short side is the minor axis diameter. The major axis diameter / minor axis diameter (aspect ratio) was determined for each particle, and the average value of the aspect ratios of the 30 particles obtained was taken as the aspect ratio.

(3) Evaluation of white spot unevenness (attachment of reflection film and light guide plate) Evaluation was performed according to the following procedures (i) to (v).
(I) A 24-inch liquid crystal monitor (manufactured by CIMEI, 24LH) was disassembled, and an edge light type backlight using an LED as a light source was taken out.
(Ii) Using a Nichiban epoxy adhesive “Araldite” (registered trademark) AR-R30, a cylindrical object having a height of 300 μm and a diameter of 3 mm was prepared.
(Iii) The optical sheet and the light guide plate are removed, and the cylindrical body is arranged on the rear case at the center in the short side direction and 20 cm away from the LED bar in the long side direction, and is the same as the mounted reflective film. A size reflective film and a light guide plate were set in this order on the rear case.
(Iv) A metal ring (2,500 g, inner diameter 900 mm) was set on the upper part of the light guide plate at a position where the protrusion becomes the center of the ring.
(V) Using a Konica Minolta two-dimensional color luminance meter CA-2000, the luminance ratio (L1) of the protruding portion and the luminance portion (L2) of the non-projecting portion (L2) are calculated and evaluated according to the following criteria: did.
Class A: less than 1.30 Class B: 1.30 or more.

(4) Evaluation of Particle Damage (Machinability) FIG. 3 is a schematic side view of the evaluation method, and evaluation was performed according to the following procedures (i) to (iii).
(I) A 55-inch liquid crystal television (manufactured by LG, model name: 55UB8500-JA) was disassembled, and an edge light type backlight using an LED as a light source was taken out.
(Ii) After fixing the convex light guide plate 2 taken out from the backlight on the desk 7 so that the convex portions face upward, the particle-containing layer of the reflective film 1 (5 cm × 10 cm) is formed on the convex light guide plate 2 2 stainless steel discs (diameter 30 mm, 2 mm thickness disc) 8, PET film 9 with a thickness of 125 μm, and a weight of 500 g are successively placed on the reflective film 1. The reflective film 1 was moved in the direction of arrow X at a speed of 10 cm / second.
(Iii) The reflective film 1 was taken out, and the particle-containing layer was observed using a laser microscope (Laser microscope VK-9710 manufactured by Keyence Co., Ltd.) with a magnification of the objective lens of 50 times and a display magnification of 100%. The observation area is 200 μm × 300 μm. The degree of particle damage (the degree of scraping) was observed and evaluated according to the following criteria.
Class A: Most particles are not damaged.
Class B: Some particles are slightly damaged, but at an acceptable level.
Class C: Many of the particles are damaged and at an unacceptable level.

(5) Evaluation of scratch property (scratch scratch) of light guide plate The surface of the particle-containing layer of the reflective film is brought into contact with the surface provided with the convex portion of the convex light guide plate used in the evaluation of (4) above. After being laminated, the reflective film was pulled up at a linear velocity of 1 m / min under a load of 250 gf / cm ² (0.0245 MPa), and the degree of scratches generated on the surface of the light guide plate was visually observed. The evaluation was based on the following criteria.
Class A: No scratches are seen.
Class B: Scratches are seen.

<Production Example 1: Creation of particles used in particle-containing layer containing particles>
150 parts by mass of dimethyl terephthalate, 98 parts by mass of ethylene glycol, 1.0 part by mass of diethylene glycol, 0.05 part by mass of manganese acetate, 0.012 part by mass of lithium acetate were charged into a rectifying column and a flask equipped with a distillation condenser. While stirring, the mixture was heated to 150 to 240 ° C. to distill methanol to conduct a transesterification reaction. After methanol was distilled, 0.03 parts by mass of trimethyl phosphate and 0.04 parts by mass of germanium dioxide were added, and the reaction product was transferred to the reactor. Next, while stirring, the pressure in the reactor was gradually reduced to 0.3 mmHg and the temperature was raised to 292 ° C. to carry out a polycondensation reaction to obtain polyethylene terephthalate. The obtained polyethylene terephthalate was extruded from a strand die and cut after cooling to form pellets. As a result of adjusting the shape of the strand, the shape of the pellet was almost a rectangular parallelepiped shape, and the average shape was 4 mm × 3 mm × 2 mm. Next, the obtained pellets were dried and crystallized by heating at 170 ° C. for 3 hours in an oven, and averaged by pulverizing while cooling with liquid nitrogen using Matsubo Co., Ltd. atomizer mill TAP-1. Polyester particles having a particle diameter of 60 μm were obtained. Furthermore, particles having an average particle diameter of 43 μm were obtained by air classification of the polyester particles.

[Example 1]
“HALS HYBRID” (registered trademark) UV-G720T (acrylic copolymer, 40% by weight solution, refractive index 1.58, manufactured by Nippon Shokubai Co., Ltd.): 9.48 g, Duranate 24A-100 (isocyanate type) Cross-linking agent, manufactured by Asahi Kasei Chemicals Corporation): 0.36 g, ethyl acetate: 9.70 g, “Orgasol” (registered trademark) 1002 D NAT 1 (nylon 6 resin particles, manufactured by Arkema Co., Ltd., average particle diameter 20 μm) : 0.46 g was mixed and stirred to prepare a coating solution. This coating solution was applied to one side of a white film made of 300 μm porous biaxially stretched polyethylene terephthalate (“Lumirror” (registered trademark) E6SQ manufactured by Toray Industries, Inc.) using Metabar # 24. A particle-containing layer was provided under a drying condition of minutes.

[Example 2]
“HALS HYBRID” (registered trademark) UV-G720T (acrylic copolymer, solution having a concentration of 40% by mass, refractive index 1.58, manufactured by Nippon Shokubai Co., Ltd.): 9.29 g, Duranate 24A-100 (isocyanate type) Cross-linking agent, manufactured by Asahi Kasei Chemicals Corporation): 0.36 g, ethyl acetate: 9.80 g, particles obtained in Production Example 1 above: 0.23 g, nylon 12 resin particles (SP10, Toray Industries, Inc., refractive index 1) 0.53, average particle size 10 μm, coefficient of variation 48%): 0.32 g was mixed and stirred to prepare a coating solution. This coating solution was applied to one side of a white film made of 300 μm porous biaxially stretched polyethylene terephthalate (“Lumirror” (registered trademark) E6SQ manufactured by Toray Industries, Inc.) using Metabar # 24. A particle-containing layer was provided under a drying condition of minutes.

[Example 3]
“HALS HYBRID” (registered trademark) UV-G720T (acrylic copolymer, 40% by weight solution, refractive index 1.58, manufactured by Nippon Shokubai Co., Ltd.): 8.96 g, Duranate 24A-100 (isocyanate type) Cross-linking agent, manufactured by Asahi Kasei Chemicals Corporation): 0.36 g, ethyl acetate: 9.99 g, particles obtained in Production Example 1 above: 0.23 g, nylon 12 resin particles (SP10, Toray Industries, Inc., refractive index 1) 0.53, average particle size 10 μm, coefficient of variation 48%): 0.46 g was mixed and stirred to prepare a coating solution. This coating solution was applied to one side of a white film made of 300 μm porous biaxially stretched polyethylene terephthalate (“Lumirror” (registered trademark) E6SQ manufactured by Toray Industries, Inc.) using Metabar # 24. A particle-containing layer was provided under a drying condition of minutes.

[Example 4]
“HALS HYBRID” (registered trademark) UV-G720T (acrylic copolymer, 40% by weight solution, refractive index 1.58, manufactured by Nippon Shokubai Co., Ltd.): 9.49 g, Duranate 24A-100 (isocyanate type) Cross-linking agent, manufactured by Asahi Kasei Chemicals Corporation): 0.36 g, ethyl acetate: 9.69 g, particles obtained in Production Example 1 above: 0.23 g, nylon 12 resin particles (SP10, Toray Industries, Inc., refractive index 1) 0.53, average particle size 10 μm, coefficient of variation 48%): 0.23 g was mixed and stirred to prepare a coating solution. This coating solution was applied to one side of a white film made of 300 μm porous biaxially stretched polyethylene terephthalate (“Lumirror” (registered trademark) E6SQ manufactured by Toray Industries, Inc.) using Metabar # 24. A particle-containing layer was provided under a drying condition of minutes.

[Example 5]
“HALS HYBRID” (registered trademark) UV-G720T (acrylic copolymer, 40% by weight solution, refractive index 1.58, manufactured by Nippon Shokubai Co., Ltd.): 8.32 g, Duranate 24A-100 (isocyanate type) Cross-linking agent, manufactured by Asahi Kasei Chemicals Co., Ltd.): 0.36 g, ethyl acetate: 10.4 g, particles obtained in Production Example 1 above: 0.23 g, nylon 12 resin particles (SP10, Toray Industries, Inc., refractive index 1) 0.53, average particle size 10 μm, coefficient of variation 48%): 0.69 g was mixed and stirred to prepare a coating solution. This coating solution was applied to one side of a white film made of 300 μm porous biaxially stretched polyethylene terephthalate (“Lumirror” (registered trademark) E6SQ manufactured by Toray Industries, Inc.) using Metabar # 24. A particle-containing layer was provided under a drying condition of minutes.

[Example 6]
“HALS HYBRID” (registered trademark) UV-G720T (acrylic copolymer, solution having a concentration of 40% by mass, refractive index 1.58, manufactured by Nippon Shokubai Co., Ltd.): 9.29 g, Duranate 24A-100 (isocyanate type) Cross-linking agent, manufactured by Asahi Kasei Chemicals Corporation): 0.36 g, ethyl acetate: 9.80 g, “Orgasol” (registered trademark) 1002 D NAT 1 (manufactured by Arkema Co., Ltd.): 0.32 g, nylon 12 resin particles ( SP3 manufactured by Toray Industries, Inc., refractive index 1.53, average particle diameter 10 μm, coefficient of variation 48%): 0.23 g was mixed and stirred to prepare a coating solution. This coating solution was applied to one side of a white film made of 300 μm porous biaxially stretched polyethylene terephthalate (“Lumirror” (registered trademark) E6SQ manufactured by Toray Industries, Inc.) using Metabar # 24. A particle-containing layer was provided under a drying condition of minutes.

[Example 7]
“HALS HYBRID” (registered trademark) UV-G720T (acrylic copolymer, solution having a concentration of 40% by mass, refractive index 1.58, manufactured by Nippon Shokubai Co., Ltd.): 7.20 g, Duranate 24A-100 (isocyanate type) Cross-linking agent, manufactured by Asahi Kasei Chemicals Corporation): 0.36 g, ethyl acetate: 11.2 g, “Orgasol” (registered trademark) 1002ES 5 NAT 1 (nylon 6 resin particles, manufactured by Arkema Co., Ltd., average particle diameter 50 μm) : 4.80 g, nylon 12 resin particles (SP10 manufactured by Toray Industries, Inc., refractive index 1.53, average particle diameter 10 μm, coefficient of variation 48%): 0.20 g was mixed and stirred to prepare a coating solution. This coating solution was applied to one side of a white film made of 300 μm porous biaxially stretched polyethylene terephthalate (“Lumirror” (registered trademark) E6SQ manufactured by Toray Industries, Inc.) using Metabar # 24. A particle-containing layer was provided under a drying condition of minutes.

[Example 8]
“HALS HYBRID” (registered trademark) UV-G720T (acrylic copolymer, 40% by weight solution, refractive index 1.58, manufactured by Nippon Shokubai Co., Ltd.): 9.48 g, Duranate 24A-100 (isocyanate type) Cross-linking agent, manufactured by Asahi Kasei Chemicals Corporation): 0.36 g, ethyl acetate: 9.70 g, “Orgasol” (registered trademark) 2002 ES 6 NAT 3 (nylon 12 resin particles, manufactured by Arkema Co., Ltd., average particle size 60 μm) ): 0.46 g was mixed and stirred to prepare a coating solution. This coating solution was applied to one side of a white film made of 300 μm porous biaxially stretched polyethylene terephthalate (“Lumirror” (registered trademark) E6SQ manufactured by Toray Industries, Inc.) using Metabar # 30. A particle-containing layer was provided under a drying condition of minutes.

[Example 9]
“HALS HYBRID” (registered trademark) UV-G720T (acrylic copolymer, 40% by weight solution, refractive index 1.58, manufactured by Nippon Shokubai Co., Ltd.): 3.60 g, Duranate 24A-100 (isocyanate type) Cross-linking agent, manufactured by Asahi Kasei Chemicals Corporation): 0.18 g, ethyl acetate: 5.62 g, “Orgasol” (registered trademark) 1002 ES 5 NAT 1 (manufactured by Arkema Co., Ltd.): 0.46 g, “Orgasol” ( (Registered trademark) 1002 D NAT 1 (manufactured by Arkema Co., Ltd.): A coating solution was prepared by adding 0.14 g with stirring. This coating solution was applied to one side of a white film made of 300 μm porous biaxially stretched polyethylene terephthalate (“Lumirror” (registered trademark) E6SQ manufactured by Toray Industries, Inc.) using Metabar # 30. A particle-containing layer was provided under a drying condition of minutes.

[Example 10]
“Pesresin” (registered trademark) S-680EA (aromatic polyester resin, ethyl acetate solution having a concentration of 45% by mass, number average molecular weight 3,000, manufactured by Takamatsu Yushi Co., Ltd.): 3.20 g, Duranate 24A-100 ( Isocyanate-based crosslinking agent, manufactured by Asahi Kasei Chemicals Corporation: 0.18 g, ethyl acetate: 6.03 g, “Orgasol” (registered trademark) 1002 ES 5 NAT 1 (manufactured by Arkema Inc.): 0.46 g, “Orgasol "(Registered trademark) 1002 D NAT 1 (manufactured by Arkema Co., Ltd.): A coating solution was prepared by adding 0.13 g with stirring. This coating solution was applied to one side of a white film made of 300 μm porous biaxially stretched polyethylene terephthalate (“Lumirror” (registered trademark) E6SQ manufactured by Toray Industries, Inc.) using Metabar # 30. A particle-containing layer was provided under a drying condition of minutes.

[Example 11]
“Pesresin” (registered trademark) S-180EA (aromatic polyester resin, ethyl acetate solution having a concentration of 30% by mass, number average molecular weight 15,000, manufactured by Takamatsu Yushi Co., Ltd.): 4.93 g, Duranate 24A-100 ( Isocyanate-based crosslinking agent, manufactured by Asahi Kasei Chemicals Corporation: 0.18 g, ethyl acetate: 4.30 g, “Orgasol” (registered trademark) 1002 ES 5 NAT 1 (manufactured by Arkema): 0.46 g, “Orgasol "(Registered trademark) 1002 D NAT 1 (manufactured by Arkema Co., Ltd.): A coating solution was prepared by adding 0.13 g with stirring. This coating solution was applied to one side of a white film made of 300 μm porous biaxially stretched polyethylene terephthalate (“Lumirror” (registered trademark) E6SQ manufactured by Toray Industries, Inc.) using Metabar # 30. A particle-containing layer was provided under a drying condition of minutes.

[Comparative Example 1]
“HALS HYBRID” (registered trademark) UV-G720T (acrylic copolymer, 40% by weight solution, refractive index 1.58, manufactured by Nippon Shokubai Co., Ltd.): 9.48 g, Duranate 24A-100 (isocyanate type) Crosslinking agent, manufactured by Asahi Kasei Chemicals Corporation): 0.36 g, ethyl acetate: 9.70 g, and particles obtained in Production Example 1: 0.46 g were mixed and stirred to prepare a coating solution. This coating solution was applied to one side of a white film made of 300 μm porous biaxially stretched polyethylene terephthalate (“Lumirror” (registered trademark) E6SQ manufactured by Toray Industries, Inc.) using Metabar # 24. A particle-containing layer was provided under a drying condition of minutes.

[Comparative Example 2]
“HALS HYBRID” (registered trademark) UV-G720T (acrylic copolymer, 40% by weight solution, refractive index 1.58, manufactured by Nippon Shokubai Co., Ltd.): 9.48 g, Duranate 24A-100 (isocyanate type) Cross-linking agent, manufactured by Asahi Kasei Chemicals Corporation): 0.36 g, ethyl acetate: 9.70 g, nylon 12 resin particles (SP10 manufactured by Toray Industries, Inc., refractive index 1.53, average particle size 10 μm, coefficient of variation 48%): 0.46 g was mixed and stirred to prepare a coating solution. This coating solution was applied to one side of a white film made of 300 μm porous biaxially stretched polyethylene terephthalate (“Lumirror” (registered trademark) E6SQ manufactured by Toray Industries, Inc.) using Metabar # 24. A particle-containing layer was provided under a drying condition of minutes.

[Comparative Example 3]
“HALS HYBRID” (registered trademark) UV-G720T (acrylic copolymer, solution having a concentration of 40% by mass, refractive index 1.58, manufactured by Nippon Shokubai Co., Ltd.): 9.70 g, Duranate 24A-100 (isocyanate type) Cross-linking agent, manufactured by Asahi Kasei Chemicals Corporation): 0.37 g, ethyl acetate: 9.56 g, particles obtained in Production Example 1 above: 0.23 g, nylon 12 resin particles (SP10 manufactured by Toray Industries, Inc., refractive index 1) 0.53, average particle size 10 μm, coefficient of variation 48%): 0.14 g was mixed and stirred to prepare a coating solution. This coating solution was applied to one side of a white film made of 300 μm porous biaxially stretched polyethylene terephthalate (“Lumirror” (registered trademark) E6SQ manufactured by Toray Industries, Inc.) using Metabar # 24. A particle-containing layer was provided under a drying condition of minutes.

  The measurement and evaluation which were mentioned above about the reflective film produced in each Example and each comparative example were performed.

  Table 1-1 shows the types of particles, the ratio of particles in the particle-containing layer, the average particle diameter, and the aspect ratio. In Table 1-2, evaluation results with white spot unevenness, particle damage, and light guide plate scratches are listed.

  The reflective films of the examples having the features of the present invention were all better in evaluation results of white spot unevenness and particle damage than the reflective films of the comparative examples.

DESCRIPTION OF SYMBOLS 1 Reflective film 2 Light guide plate 3 Light emitting diode 4 Back housing 5 Convex part of a light guide plate 6 Concave part of a back housing 7 Desk 8 Stainless disc 9 PET film 10 Weight

Claims (3)

An edge-light-type reflective film for a backlight having a particle-containing layer containing particles on at least one surface of a substrate film and satisfying the following (i) and (ii).
(I) The aspect ratio of the particles is 1.06 to 1.30.
(Ii) The average particle diameter of the particles is 15 to 100 μm.   The reflective film for an edge light type backlight according to claim 1, wherein the particles are particles containing an aromatic polyester and / or particles containing polyamide.   A backlight for a liquid crystal display, comprising the reflective film for an edge-light-type backlight according to claim 1, wherein the light-emitting diode is a light source.