JP5532799B2 - White reflective film - Google Patents

Description

  The present invention relates to a white reflective film that suppresses tube unevenness (display brightness unevenness due to the arrangement of fluorescent lamps) while improving the brightness of a backlight for a direct liquid crystal display.

  Liquid crystal display devices are used in various applications such as notebook computers and mobile phone devices, televisions, monitors, car navigation systems, and the like. The liquid crystal display device incorporates a backlight device serving as a light source, and is configured to display light by controlling light beams from the backlight device through a liquid crystal cell. The characteristic required for this backlight device is not only as a light source for emitting light, but also to make the entire screen shine brightly and uniformly.

  The configuration of the backlight device can be roughly divided into two. One is a system called a sidelight type backlight. This is a method mainly used for, for example, a notebook personal computer or the like that is required to be thin and small, but is characterized by using a light guide plate as a basic configuration. In the case of a sidelight-type backlight, a light source is disposed on the side surface of the light guide plate, light is incident on the light guide plate from the side surface, and light is propagated throughout the surface while totally reflecting inside the light guide plate. A part of the light is removed from the total reflection condition by diffusing dots or the like applied to the back surface, and the light is collected from the front surface of the light guide plate to function as a backlight, that is, a surface light source. In the case of a sidelight type backlight, in addition to these configurations, a reflection film that functions to reflect and reuse light leaking from the back surface of the light guide plate, and a diffusion sheet that equalizes the light emitted from the front surface of the light guide plate Various types of optical films are used, such as a light collecting sheet represented by a prism sheet that improves the front luminance, and a luminance improving sheet that improves the luminance on the liquid crystal panel.

  Another method is a method called a direct type backlight. This is a system that is preferably used for television applications that require large size and high brightness, but the basic structure is characterized by a structure in which fluorescent tubes are arranged directly behind the screen without using a light guide plate. By arranging a plurality of linear or partially linear fluorescent tubes in parallel at the back of the screen, it is possible to deal with a large screen and to ensure sufficient brightness. However, brightness unevenness (brightness unevenness) in the screen is caused by the fluorescent tube arranged at the back of the screen, which is also a feature, and the unevenness becomes an image of the fluorescent tube (tube unevenness), which causes a reduction in image quality. For this reason, in the direct type backlight, in order to eliminate the tube unevenness, a light diffusion plate having extremely strong light diffusibility is arranged on the upper side of the fluorescent tube to make the screen uniform (Patent Document 1). The light diffusing plate is a light diffusing plate made of an acrylic resin or a polycarbonate resin in which fine particles are dispersed. This light diffusing plate eliminates tube unevenness and makes the screen uniform, but because it diffuses strongly, the total light transmittance is low and the light utilization efficiency deteriorates. As a result, the required front brightness is insufficient. Therefore, a diffusion sheet showing a light collecting effect in the front direction is disposed on the light diffusion plate while diffusing light isotropically. This diffusion sheet is a sheet called a bead sheet in which a diffusion layer containing fine particles such as organic cross-linked particles is formed on a base material sheet. Unlike a light diffusion plate, this diffusion film is an optical film that exhibits a certain degree of directivity in the front direction. It is. In addition to these, a reflecting member that reflects light emitted backward from the fluorescent tube, a light collecting sheet represented by a prism sheet for improving light collecting properties, and a deflection of light emitted from the fluorescent tube are separated. A brightness enhancing sheet for improving the brightness on the liquid crystal panel is incorporated, and a direct type backlight device is configured by combining various sheets. However, in direct-type backlights used for flat-screen TVs that have been attracting attention in recent years, and direct-type backlights that reduce the number of fluorescent tubes installed for the purpose of reducing power consumption from the viewpoint of environmental friendliness, tube unevenness is prominent. Therefore, it is necessary to use a large number of the above-mentioned optical members, which makes it difficult to reduce the thickness, increases the cost, and consumes less power when manufacturing optical members. On the contrary, there is a concern of increasing the environmental impact. In order to solve such a problem, a method (Patent Document 2) for improving the functions and performance of various sheets by applying a prism shape having a sawtooth cross section to the light diffusing plate, and a prism shape having a cross section sawtooth shape. There has also been proposed a method (Patent Document 3) in which a reflecting member is molded into a projection so as to be suitable for the applied light diffusion plate.

  In addition, there has been proposed a method of trying to suppress tube unevenness by using a very low gloss reflective film (Patent Document 4).

JP 2004-29091 A JP 2006-164890 A JP 2006-155926 A JP 2006-72347 A

  However, the light diffusing plate having extremely strong light diffusibility as in Patent Document 1 has the effect of eliminating tube unevenness and increasing the uniformity of the screen, but the total light transmittance is not high and it is difficult to increase the brightness. In addition, the methods of molding the light diffusing plate and the reflecting member as in Patent Documents 2 and 3 are not preferable from the viewpoint of cost and productivity, and it is difficult to achieve both uniformity and luminance. The reality is that no measures have been taken. Moreover, even if it uses a very low gloss reflective film like patent document 4, the effect which suppresses pipe | tube unevenness may become inadequate.

  In view of the background of the prior art, the present invention is to provide a white reflective film for a display device that can efficiently suppress tube unevenness and has a high luminance, and a direct backlight of the same. That is, the present invention does not provide a white reflective film for a display device with high brightness and a direct-type backlight device comprising the same, which can efficiently suppress tube unevenness even if the optical member is used without special processing. It is what.

In order to solve this problem, the present invention employs the following configuration. That is, the white reflective film of the present invention is
(1) The glossiness according to JIS K 7105 (1981) measured from the surface on which at least one resin layer is laminated on at least one surface of the white film and the resin layer is provided has the following (i), (ii ) White reflective film that simultaneously satisfies
(I) The 60 degree gloss is 25 or more (ii) The value obtained by dividing the 60 degree gloss by the 20 degree gloss is 2.5 or more. (2) The resin layer contains particles, and The white reflective film according to (1), wherein the maximum particle diameter in the resin layer cross section perpendicular to the film surface of the particles is smaller than the thickness of the resin layer,
(3) The white reflective film according to (2) , wherein the particle has an irregular shape, a flat shape, or a needle shape.
(4) The white reflective film according to any one of (2) and (3) , wherein the particles are porous,
(5) A direct type backlight configured using the white reflective film according to any one of (1) to (4),
It is.

  According to the present invention, by providing a resin layer having a specific glossiness on at least one side of a white film, the brightness uniformity of the backlight can be improved when used by incorporating it in a direct type backlight, It is possible to provide a backlight whose luminance is uniform within the backlight surface (with reduced tube unevenness).

It is an example of the cross-sectional schematic diagram of the white reflective film of this invention. It is an example of the cross-sectional schematic diagram of the white film of the base material concerning this invention. It is sectional drawing of the direct type | mold backlight apparatus incorporating the white reflective film of this invention. It is a figure which shows typically the direct type backlight apparatus used for the pipe unevenness and brightness | luminance evaluation of this invention from upper part.

  The present invention, the white reflection film that suppresses the above-mentioned problem, that is, unevenness of the tube (luminance unevenness of the display surface due to the arrangement of fluorescent lamps), has earnestly studied, has at least one resin layer on at least one side of the white film, As a result, it was clarified that such a problem can be solved at once by using a resin having a glossiness measured from the surface provided with the resin layer in a specific range.

The white reflective film of the present invention has a resin layer provided on at least one surface of the white film, and the glossiness according to JIS K 7105 (1981) measured from the surface provided with the resin layer is the following (i), It is necessary to satisfy (ii) at the same time.
(I) 60 degree glossiness is 25 or more (ii) The value obtained by dividing 60 degree glossiness by 20 degree glossiness is 2.5 or more JIS K 7105 measured from the surface provided with such a resin layer When the glossiness according to (1981) satisfies the above (i) and (ii) at the same time, the glossiness is changed and controlled by the incident angle, and light is efficiently transmitted between the fluorescent tube and the frontal direction. Therefore, it is presumed that the tube unevenness in the direct type backlight is suppressed.

  When such a resin layer is not provided or the glossiness according to JIS K 7105 (1981) measured from the surface does not satisfy at least one of the above (i) and (ii) Even if the white reflective film is incorporated into a backlight, the effect of suppressing tube unevenness cannot be obtained.

  More preferably, the 60 degree glossiness of (i) is 30 or more. When this value is 30 or more, the change in the glossiness due to the incident angle tends to appear remarkably, and a greater effect of suppressing tube unevenness appears. When this value is less than 25, even if the value obtained by dividing the 60 degree glossiness of (ii) by the 20 degree glossiness is 2.5 or more, the light is efficiently transferred between the fluorescent tubes. This is not preferable because it is difficult to reflect in the direction and the effect of suppressing tube unevenness is reduced.

  The value obtained by dividing the 60 ° glossiness of (ii) by the 20 ° glossiness is preferably 3 or more, and most preferably 4 or more. When this value is 4 or more, it is considered that the change and control of the glossiness due to the incident angle becomes large, and the effect of suppressing tube unevenness appears more. When this value is less than 2.5, since the change / control of the glossiness is small, the ratio of light reflected between the fluorescent tubes in the front direction decreases, and the effect of suppressing tube unevenness decreases. It is not preferable.

  This is thought to be due to the following mechanism. In many backlights, the light emitted from the light source is incident on the reflective film at 60 degrees from the normal direction. The higher the 60 degree glossiness of the film, that is, the greater the amount of specular reflection light, the higher the brightness in the middle of the lamp and the effect of suppressing tube unevenness. On the other hand, when the light incident on the reflection film at 20 degrees is specularly reflected, it is bounced back to the portion close to the lamp, so that the one that is diffused and reflected as much as possible, that is, the one with a lower glossiness of 20 degrees, Expresses the effect of suppressing tube unevenness. When both of these two effects are manifested, the tube unevenness is efficiently suppressed, and the ratio of 60 degree glossiness to 20 degree glossiness (value obtained by dividing 60 degree glossiness by 20 degree glossiness) is 2. When it is 5 or more, a remarkable effect of suppressing tube unevenness is exhibited.

  In addition, the resin layer defined in the white reflective film of this invention is a layer which uses a high molecular compound, and the form of the resin layer is the thin film provided on the white film, and bonding of films The composite layer is not limited to these.

  The resin layer according to the present invention preferably contains particles, and the maximum particle diameter (hereinafter also simply referred to as the maximum particle diameter) in the cross section of the resin layer perpendicular to the film surface of the particles is preferably smaller than the thickness of the resin layer. When containing particles with such a small particle size, it becomes easier to satisfy the above (i) and (ii) for the reasons described later, and when not containing particles or when containing particles larger than the resin layer thickness, The white reflective film of the present invention can be obtained more easily, and further, a reflective film having an effect of suppressing tube unevenness can be obtained.

  Such particles may be made of either organic or inorganic materials, or a mixture of both. In addition, from the viewpoint of improving dispersibility in the resin layer, maintaining stability, productivity, and the like, surface treatment may be performed within a range that does not impair the effects of the invention.

  Examples of the particles used in the present invention include acrylic particles such as acrylic particles, polyester particles, polyolefin particles, and silicone particles. Specifically, Chemisnow (registered trademark) (manufactured by Soken Chemical Co., Ltd.), silicone resin KR series, etc. (Manufactured by Shin-Etsu Chemical Co., Ltd.), Techpolymer (registered trademark) (manufactured by Sekisui Plastics Co., Ltd.), and the like can be used. In the case of an inorganic system, any of metals, salts, oxides, hydroxides and the like can be used. For example, Quattron (registered trademark) (manufactured by Fuso Chemical Industry Co., Ltd.), Whiscal (registered trademark) (Maruo calcium ( Co., Ltd.), Kaolin Clay (manufactured by Imeris Minerals Japan Co., Ltd.), Silo Hovic (manufactured by Fuji Silysia Chemical Co., Ltd.), and the like, but are not particularly limited thereto.

  The content of the particles contained in the resin layer according to the present invention is not particularly limited, and depends on the type and shape of the particles used, dispersibility, productivity, etc., but with respect to the entire resin layer containing the particles. The content is preferably 0.1% by weight or more, and more preferably 1.5% by weight or more, but a content with a good effect of suppressing tube unevenness may be selected.

  When the content of the particles is less than 0.1% by weight, the tube unevenness suppressing effect may not be improved. Further, the upper limit is not particularly limited, but when it exceeds 75% by weight, productivity may be inferior, particles may easily fall off from the resin layer, or the 60 degree gloss may be less than 25. Therefore, it is preferably controlled to 75% by weight or less.

  Considering the resin layer dispersibility and productivity, organic particles include acrylic particles, polyester particles, silicone particles, etc. Specifically, Chemisnow (registered trademark) (manufactured by Soken Chemical Co., Ltd.), silicone resin KR series, etc. (Manufactured by Shin-Etsu Chemical Co., Ltd.), Techpolymer (registered trademark) (manufactured by Sekisui Plastics Co., Ltd.), and the like can be used. In the case of inorganic systems, salts and oxides are preferably used. For example, Quattron (registered trademark) (manufactured by Fuso Chemical Industry Co., Ltd.), Wiscal (registered trademark) (manufactured by Maruo Calcium Co., Ltd.), Kaolin clay ( (Imeris Minerals Japan Co., Ltd.), Silo Hovic (Fuji Silysia Chemical Co., Ltd.), etc. are mentioned, but not particularly limited thereto.

  For example, in the case of an acrylic resin, 5 to 12% by weight of a particle having a maximum particle size of 5 μm as defined below may be added to the resin layer, or silica may be used as a preferable combination of the type of particles used, the particle size, and the content. In the case of particles, one having a maximum particle size of 2 μm may be added to the resin layer in an amount of 1 to 8% by weight. Of course, other types of particles, particle sizes, and contents (i) (ii) are glossy. If even the condition of degree is satisfied, the effect of suppressing the tube unevenness will be manifested.

  Moreover, although the thickness of the resin layer concerning this invention is dependent also on the kind etc. of particle | grains, it is preferable that it is 0.05-50 micrometers, More preferably, it is 0.8-10 micrometers.

  When the thickness of the resin layer is 0.05 μm or more, it becomes easy to impart light resistance when an ultraviolet absorber or / and a light stabilizer are added, and the thickness of the resin layer is a preferred embodiment of the present invention. It is easier to contain particles having a smaller maximum particle size. On the other hand, if the thickness exceeds 50 μm, the brightness of the entire backlight may decrease, which is not preferable from the viewpoint of economy.

  In addition, the thickness of the resin layer here means the total thickness of the resin layer containing particles. When the resin layer containing particles is one or more, the thickness of the entire resin layer, that is, a plurality of layers. It is obtained from the thickness of the entire resin layer.

  In the present invention, by containing particles in the resin layer and using particles whose maximum particle diameter is smaller than the thickness of the resin layer, the surface of the resin layer is likely to be smooth, and the 60 degree glossiness is easily set to 25 or more. . On the other hand, the 20 degree glossiness is easily affected by the scattering of light inside the resin layer, so using such a particle size increases the surface area of the interface between the particle and the resin layer and scatters more light. 20 degree glossiness can be reduced, and as a result, the ratio of 60 degree glossiness / 25 degree glossiness can be easily set to 2.5 or more.

  In the present invention, the shape of the particles contained in the resin layer is the average projected area S of the particles observed from the direction parallel to the resin surface (the same as the direction parallel to the film surface, the same applies hereinafter), and perpendicular to the resin surface. It is more preferable that the non-spherical shape has a ratio S / L with respect to the average projected area L of the particles observed from a certain direction (same as the direction perpendicular to the film surface, the same applies hereinafter). . The term “non-spherical shape” as used herein means a shape other than a true spherical shape. Here, with respect to S / L, the S / L tends to be less than 1.0 for particles having shape anisotropy due to the shearing force when forming the resin layer.

  In the present invention, the ratio S / L between the average projected area S of particles observed from a direction parallel to the resin surface and the average projected area L of particles observed from a direction perpendicular to the resin surface is less than 1.0. The non-spherical shape is advantageous from the standpoint of productivity and cost because the content of particles can be reduced and the resin layer can be made thinner in order to exhibit an effect of reducing luminance unevenness. S / L is preferably 0.6 or less, and more preferably 0.2 or less. The lower limit of S / L is not particularly defined, but is preferably 0.01 or more in view of particles that can be made substantially. As the non-spherical shape in which S / L is less than 1.0, for example, a flat shape such as a star shape, a leaf shape or a disk shape, a rhombus shape, a rectangular shape, a needle shape, a confetti shape, an indefinite shape, etc. Etc. Among them, an indefinite shape, a flat shape, and a needle shape are preferable. However, since it cannot be uniquely limited depending on the component, refractive index, and production method of the particle, it is not particularly limited to these, If the particles having such a shape are contained, it is easy to satisfy the above (i) and (ii) without any special processing, and the effect of suppressing tube unevenness can be obtained as compared with the case where the particles having such a shape are not contained. Cheap.

  The indefinite shape is a particle whose particle is not fixed in a certain shape and whose shape varies depending on the individual particle. For example, this is the case when the crystals are secondarily pulverized. As an example of particles having an indefinite shape, Syrohovic (registered trademark) manufactured by Fuji Silysia Co., Ltd. can be mentioned. In addition, the flat shape means a particle having a small particle size in a direction that is wide in a specific two-dimensional direction and perpendicular thereto, and the needle shape is a material that is long in a specific one-dimensional direction and has a short diameter on a surface orthogonal thereto. say.

  The maximum particle size of the particles contained in the resin layer in the present invention is determined as follows. The thermoplastic resin film of the present invention was cut in a direction perpendicular to the resin surface at a knife inclination angle of 3 ° using a rotary microtome manufactured by Nippon Microtome Laboratory Co., Ltd., and the resulting thermoplastic resin film resin The layer cross section is observed using a scanning electron microscope ABT-32 manufactured by Topcon Corporation. The observation magnification is a magnification at which 20 to 100 particles contained in the resin layer can be seen in one field of view. Among the particle parts existing in one field of view, the maximum diameters of the five largest diameters are measured, and any five fields of view are observed in the same manner, and the average value of the maximum diameters of a total of 25 points is determined. The maximum particle diameter in the cross section of the resin layer perpendicular to the film surface of the particles in the present invention.

  However, in the case where the resin layer in the present invention contains non-spherical particles whose S / L is less than 1.0, 20 to 100 particles can be seen in one field of view. In the state, the length of the particle part measured in the resin layer thickness direction is measured at five locations from the largest value, and any five visual fields are similarly observed. The average value of the lengths of the particle portions in the resin layer thickness direction at a total of 25 positions determined in this manner is defined as the maximum particle diameter of the particles in the present invention. When a plurality of types of particles are contained in the resin layer, the maximum particle size of the particles is obtained for each particle as described above, and the largest value is used as the maximum particle size of the particles in the present invention.

  Here, “average projected area S”, “average projected area L”, and “ratio S / L” are obtained as follows. First, the white reflective film of the present invention is cut in a direction perpendicular to the resin surface at a knife inclination angle of 3 ° using a rotary microtome manufactured by Nippon Microtome Laboratory. The resin layer cross section of the obtained white reflective film is observed using a scanning electron microscope ABT-32 manufactured by Topcon Corporation. The observation magnification is a magnification at which 20 to 100 particles contained in the resin layer can be seen in one field of view. Among the particle portions existing in one field of view, the areas of five locations are measured from those having a large projected area. In the same manner, arbitrary five visual fields are observed, and an average value of the projected areas of a total of 25 locations is defined as an average projected area S. Next, the resin surface is observed in the same manner from the direction perpendicular to the resin surface, and the average value of the total projected areas at 25 locations is defined as the average projected area L. The obtained average projected area S is divided by the average projected area L to obtain S / L.

  In the present invention, the particles are more preferably porous particles. The term “porous” as used herein means that a particle has pores, and the term “pore” refers to a portion that is recessed in a concave shape toward the inside of the particle. For example, it may be a hollow shape, a shape that is recessed toward the inside or center of the particle, such as a needle or a curve, or a shape that penetrates the particle, and the size and volume may vary. It is not limited to. By using particles having pores in this way, it is easy to satisfy the above (i) and (ii) without performing special processing. It is easy to obtain a non-uniformity suppressing effect. In the present invention, the presence or absence of the pores of the particles can be determined by the following method, for example.

  The sample was cut in a direction perpendicular to the film plane with a knife inclination angle of 3 ° using a rotary microtome manufactured by Nippon Microtome Laboratories Co., Ltd., and the obtained film cross section was scanned with a scanning electron microscope ABT manufactured by Topcon Corporation. -32 so that one particle is projected substantially over the entire field of view, for example, at an observation magnification of 2500 to 10,000 times, and by appropriately adjusting the contrast of the image, Presence / absence and particle shape can be confirmed.

  If the particles cannot be cut, immerse the resin layer in an organic solvent, peel off and collect the resin layer, and then press and slide the slide glass to remove the particles from the resin layer and collect a sufficient amount of particles. . Subsequently, the obtained particles are used, for example, at an observation magnification of 2500 to 10,000 times so that one particle is projected over the entire visual field region using a scanning electron microscope ABT-32 manufactured by Topcon Corporation. Moreover, the contrast of the image was appropriately adjusted and observed, and the presence or absence of pores and the shape of the particles were judged. Note that the presence / absence of pores is determined based on whether or not spots or spots are present in the particles in the observed image. There were no pores.

  Examples of the substance having pores include Pyrosilo (registered trademark) and Silo Hovic (registered trademark) manufactured by Fuji Silysia.

  When the white reflective film of the present invention is used as a backlight, the compound contained in the white film or resin layer of the substrate may be deteriorated by light emitted from a lamp such as a fluorescent tube, particularly ultraviolet rays (for example, yellowing) Such as optical degradation or degradation degradation to lower molecular weight). In order to cope with such a problem, the resin forming the resin layer provided on the white film of the base material contains at least one of an ultraviolet absorber and a light stabilizer within a range that does not inhibit the effect of the present invention. It is preferable to do. By including at least one of these in the resin layer, a reflective film with little change in luminance and color tone can be obtained even when used for a long time.

  The resin used as the resin layer according to the present invention is not particularly limited, but a resin mainly composed of an organic component is preferable. For example, a polyester resin, a polyurethane resin, an acrylic resin, a methacrylic resin, a polyamide resin, a polyethylene resin, a polypropylene resin, Examples thereof include polyvinyl chloride resin, polyvinylidene chloride resin, polystyrene resin, polyvinyl acetate resin, and fluorine resin.

  These resins may be used alone, or two or more copolymers or a mixture thereof may be used. Among these, polyester resins, polyurethane resins, acrylic or methacrylic resins are preferably used in terms of heat resistance, additive dispersibility, productivity, and gloss. In terms of the light resistance of the resin layer, it is more preferable that the resin contains an ultraviolet absorber and a light stabilizer.

  Such ultraviolet absorbers and light stabilizers are roughly classified into inorganic and organic types, but are not particularly limited with respect to the form of inclusion, and may be a method such as mixing with a resin that forms such a resin layer. In order to prevent bleeding out from the resin layer, for example, a method such as copolymerization with a resin forming the resin layer may be used.

  As such inorganic ultraviolet absorbers, titanium oxide, zinc oxide, cerium oxide and the like are generally known, and at least one selected from the group consisting of zinc oxide, titanium oxide and cerium oxide does not bleed out. It is preferably used from the viewpoints 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 is most preferable from the viewpoints of economy, ultraviolet absorption, and photocatalytic activity. As such zinc oxide, FINEX-25LP, FINEX-50LP (manufactured by Sakai Chemical Industry Co., Ltd.) or the like can be used.

  Examples of such organic ultraviolet absorbers include benzotriazole and benzophenone.

  Since these ultraviolet absorbers only absorb ultraviolet rays and cannot capture organic radicals generated by ultraviolet irradiation, the white film of the base material may be chain-degraded by these radicals. In order to capture these radicals and the like, a light stabilizer is preferably used in combination, and a hindered amine (HALS) compound is preferably used as the light stabilizer.

  Here, as the copolymerization monomer for fixing the organic ultraviolet absorber and / or the light stabilizer, vinyl monomers such as acrylic and styrene are highly versatile and economically preferable. Among these copolymerizable monomers, since the styrene vinyl monomer has an aromatic ring and is easily yellowed, copolymerization with an acrylic vinyl monomer is most preferably used in terms of light resistance.

  In addition, as a thing by which the reactive vinyl monomer was substituted by the said benzotriazole, 2- (2'-hydroxy-5'-methacryloxyethylphenyl) -2H-benzotriazole (brand name: RUVA-93); Otsuka Chemical ( In addition, 4-methacryloyloxy-2,2,6,6-tetramethylpiperidine (“Adeka Stab LA-82”) can be used in which a hindered amine compound is substituted with a reactive vinyl monomer. "; Manufactured by ADEKA Co., Ltd.) can be used.

  In the present invention, the organic ultraviolet absorber includes a resin containing an organic ultraviolet absorber such as benzotriazole or benzophenone, a resin copolymerized with a benzotriazole-based or benzophenone-based reactive monomer, or a hindered amine. A resin containing and / or copolymerizing a light stabilizer such as a (HALS) -based reactive monomer can be used within a range that does not impair the effects of the present invention.

  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 thin and have a high UV-absorbing effect. More preferred.

  These production methods and the like are disclosed in detail in JP-A-2002-90515 [0019] to [0039]. Among them, HALS HYBRID (registered trademark) (manufactured by Nippon Shokubai Co., Ltd.) containing an acrylic monomer and UV absorber copolymer as an active ingredient can be used.

  In addition, when processing the present invention, that is, when the white reflective film of the present invention is punched out, molded, and incorporated into a backlight, etc., there is a problem that charged dust or dust existing around it adheres. There is a case. In order to cope with such a problem, it is preferable to contain an antistatic agent in the resin that forms the resin layer provided on the white film of the base material as long as the effects of the present invention are not impaired.

  Such an antistatic agent is roughly classified into an organic type and an inorganic type, but the form to be contained is not particularly limited, and a method such as mixing with a resin forming the resin layer may be used. When it is desired to prevent bleeding out from the layer, for example, a method of copolymerizing with a resin forming the resin layer may be used.

  Examples of such an organic antistatic agent include cationic conductive resins and anionic ones. As such an inorganic antistatic agent, for example, tin oxide, antimony-doped tin oxide (hereinafter abbreviated as ATO), indium oxide, tin-doped indium oxide, or the like can be used.

  Furthermore, when providing this resin layer by application | coating, the coating material which disperse-processed ATO and the resin binder previously can also be used. From the standpoint of antistatic properties, these coating materials include, for example, ELCOM P-3501 (polyester resin binder, manufactured by Catalyst Chemical Industry Co., Ltd.), ELCOM TO-1002 ATC (acrylic resin binder, manufactured by Catalyst Chemical Industry Co., Ltd.). Can be used.

  The white film of the base material according to the present invention (the white reflective film of the present invention has a white film of the base material and a resin layer) should have a high visible light reflectivity. The contained white film is preferably used. Although these white films are not limited, porous unstretched or biaxially stretched polypropylene films and porous unstretched or stretched polyethylene terephthalate films are preferably used as examples. About these manufacturing methods etc., [0034]-[0057] of JP-A-8-262208, [0007]-[0018] of JP-A-2002-90515, [0008]-[0034] of JP-A-2002-138150, etc. It is disclosed in detail. Among them, porous white biaxially stretched polyethylene terephthalate film disclosed in JP-A-2002-90515 and porous white biaxially stretched mixed and / or copolymerized with polyethylene naphthalate from the viewpoint of heat resistance and reflectivity A polyethylene terephthalate film is particularly preferred as the white film according to the present invention for the reasons described above.

  The structure of the white film of the base material according to the present invention may be appropriately selected depending on the intended use and required characteristics, and is not particularly limited. However, the single layer having at least one layer and / or 2 A composite film having at least one layer is preferred, and at least one of the composite films preferably contains at least one of bubbles, inorganic particles, and organic particles.

  An example of a single layer configuration (= 1 layer) is, for example, a white film of a base material having only a single layer A, and the layer A contains at least one of bubbles, inorganic particles, and organic particles. The thing of composition is mentioned. Moreover, as an example of 2 layer structure, it is the white film of the base material of the 2 layer structure of A layer / B layer which laminated | stacked B layer on the said A layer, These A and B layers in at least any one layer , Bubbles, inorganic particles, and organic particles may be used. Moreover, you may use the white film of the 2 layer structure which turned the edge of any one surface layer of the white film of the 3 layer structure mentioned later with the cutter knife etc., and peeled the whole one surface layer. Furthermore, as an example of a three-layer structure, as described above, a white film of a base material 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. There is a configuration in which at least one of each layer contains at least one of bubbles, inorganic particles, and organic particles. 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 and / or organic particles contained in the white film of the base material is preferably 0.3 to 2.0 μm. As such organic particles, resins mainly composed of a high-melting cross-linked polymer component are preferable. For example, polyester resin, polyamide resin particles such as benzoguanamine, polyurethane resin, acrylic resin, methacrylic resin, polyamide resin, polyethylene resin, polypropylene Examples thereof include resins, polyvinyl chloride resins, polyvinylidene chloride resins, polystyrene resins, polyvinyl acetate resins, fluorine-based resins, silicone resin particles, and hollow particles thereof. These resins may be used alone, or two or more copolymers or a mixture thereof may be used. In terms of the light resistance of the white film, it is preferable that the contained spherical particles contain an ultraviolet absorber and a light stabilizer. 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 a 3 layer structure white film (polyester film) is demonstrated among the said base material white films, it is not limited to this example.

First, polymethylpentene is mixed in polyethylene terephthalate as an incompatible polymer, and polyethylene glycol, polybutylene terephthalate and polytetramethylene glycol copolymer are mixed as a low specific gravity agent. 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 times, the whiteness of the obtained film becomes poor. On the other hand, if the area magnification exceeds 16 times, the film tends to be broken during stretching and the film forming property tends to be poor. 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. To obtain a base thermoplastic resin film according to the present invention.

  As an example of such a base thermoplastic resin film, first, as a white film having a single layer structure, Lumirror (registered trademark) E20 (manufactured by Toray Industries, Inc.), SY64, SY70 (manufactured by SKC), white refstar (registered) (Trademark) WS-220 (manufactured by Mitsui Chemicals, Inc.) and the like. Examples of the two-layer white film include Tetron (registered trademark) film UXZ1, UXSP (manufactured by Teijin DuPont Films), PLP230 (Mitsubishi Resin). As a white film having a three-layer structure, Lumirror (registered trademark) E60L, E6SL, E6SR, E6SQ, E6Z, E80, E80A, E80B (manufactured by Toray Industries, Inc.), Tetoron (registered) Trademark) film UX, UXH (manufactured by Teijin DuPont Films Co., Ltd.). Examples of white sheets having a configuration other than these include Optilon ACR3000, ACR3020 (manufactured by DuPont), and MCPET (registered trademark) (manufactured by Furukawa Electric Co., Ltd.).

  Various additives can be added to the white reflective film (white film and / or resin layer) according to the present invention within a range not impairing the effects of the present invention. Examples of additives include organic and / or inorganic fine particles, crosslinking agents, flame retardants, flame retardant aids, luminescent materials typified by fluorescent brighteners, heat stabilizers, oxidation stabilizers, organic lubricants, Antistatic agents, nucleating agents, dyes, fillers, dispersants, coupling agents, and the like can be used.

  In the white reflective film of the present invention, the average reflectance at a wavelength of 400 to 700 nm measured from the surface provided with the resin layer is preferably 85% or more, more preferably 87% or more, and further preferably 90% or more. Most preferably, it is 95% or more.

  When the average reflectance is less than 85%, the luminance may be insufficient depending on the applied liquid crystal display. In addition, when the resin layer is provided in both surfaces, the average reflectance measured from any resin layer should just be 85% or more. As a method for setting the average reflectance at a wavelength of 400 to 700 nm to 85% or more, for example, there is a method of increasing the absolute amount of the light reflecting interface in the white film of the substrate or the resin surface. In particular, a method of forming more void structures in the white film of the base material described above or increasing the thickness of the portion having the void structure can be mentioned.

  In the present invention, the surface on which the resin layer is provided is not particularly limited, and has a two-layer structure of A layer / B layer, a three-layer structure of A layer / B layer / A layer or A layer / B layer / C layer. In some cases, it may be provided on either side.

  In the present invention, when the resin layer is formed on at least one side of the white film, it can be formed by any method. For example, a resin-containing coating liquid can be used for gravure coating, roll coating, spin coating, reverse coating. Using various coating methods such as bar coating, screen coating, blade coating, air knife coating, and dipping, it can be applied at the time of manufacturing a white film of the substrate (in-line coating) or applied on the white film after completion of crystal orientation ( Examples include a method of forming a coating layer such as offline coating) and a method of attaching another film or sheet by lamination or the like, but is not particularly limited thereto.

  The white reflective film of the present invention thus obtained efficiently suppresses tube unevenness and has high brightness even when used without special processing on the optical member when incorporated in a direct type liquid crystal backlight. A backlight for a display device can be provided. According to a more preferable aspect, even when the luminance is used for a long time, the luminance can be reduced little. Therefore, the white reflective film of the present invention can be suitably used as a reflector of a direct type backlight for a liquid crystal display. In addition, it is also suitably used as a reflector for edge light type backlights, a reflector for edge light type backlights, a reflector for various surface light sources and lighting devices, and a sealing film for solar cell modules. be able to.

  The measurement method and evaluation method are shown below.

(1) Glossiness According to JIS K 7105 (1981), the glossiness from the surface provided with the resin layer of the white reflective film in the present invention is a digital variable glossiness meter UGV-5D manufactured by Suga Test Instruments Co., Ltd. And measured. At that time, the secondary standard surface No. made by the same company for each measurement angle of 20 degrees and 60 degrees. After calibration using 89W039, arbitrary 5 points were measured for each reflective film, and the average value was defined as the glossiness at the incident angle of the reflective film.

(2) Maximum particle diameter in the resin cross section in the direction perpendicular to the film surface of the particles The maximum particle diameter in the resin cross section in the direction perpendicular to the film surface of the particles contained in the resin layer in the present invention was determined as follows. . The thermoplastic resin film of the present invention is cut in a direction perpendicular to the resin surface at a knife inclination angle of 3 ° using a rotary microtome manufactured by Nippon Microtome Laboratories. The resin layer cross section of the obtained thermoplastic resin film is observed using a scanning electron microscope ABT-32 manufactured by Topcon Corporation. The observation magnification is a magnification at which 20 to 100 particles contained in the resin layer can be seen in one field of view. Among the particle portions existing in one field of view, the maximum diameters at the five locations from the largest are measured. Arbitrary five visual fields are observed by the same method, and the average value of the maximum diameters at a total of 25 positions is set as the maximum particle diameter of the particles in the present invention.

  However, in the case where the resin layer in the present invention contains non-spherical particles whose S / L is less than 1.0, 20 to 100 particles can be seen in one field of view. In the state, the length of the particle part measured in the resin layer thickness direction is measured at five locations from the largest value, and any five visual fields are similarly observed. The average value of the lengths of the particle portions in the resin layer thickness direction at a total of 25 positions determined in this manner is defined as the maximum particle diameter of the particles in the present invention. When a plurality of types of particles are contained in the resin layer, the maximum particle size of the particles is obtained for each particle as described above, and the largest value is used as the maximum particle size of the particles in the present invention.

  Here, “average projected area S”, “average projected area L”, and “ratio S / L” are obtained as follows. First, the white reflective film of the present invention is cut in a direction perpendicular to the resin surface at a knife inclination angle of 3 ° using a rotary microtome manufactured by Nippon Microtome Laboratory. The resin layer cross section of the obtained white reflective film is observed using a scanning electron microscope ABT-32 manufactured by Topcon Corporation. The observation magnification is a magnification at which 20 to 100 particles contained in the resin layer can be seen in one field of view. Among the particle portions existing in one field of view, the areas of five locations are measured from those having a large projected area. In the same manner, arbitrary five visual fields are observed, and an average value of the projected areas of a total of 25 locations is defined as an average projected area S. Next, the resin surface is observed in the same manner from the direction perpendicular to the resin surface, and the average value of the total projected areas at 25 locations is defined as the average projected area L. The obtained average projected area S is divided by the average projected area L to obtain S / L.

(3) Thickness of resin layer The thickness of the resin layer in this invention was calculated | required as follows. The sample is cut in a direction perpendicular to the film plane at a knife tilt angle of 3 ° using a rotary microtome manufactured by Nippon Microtome Research Co., Ltd. Particles obtained by observing the obtained film cross section with a scanning electron microscope ABT-32 manufactured by Topcon Corporation at a magnification such that the resin layer has an area of 30% to 70% with respect to the screen, and are laminated on the white film of the substrate The total thickness of the resin layer contained is measured at five locations on each side, and the average value is defined as “the thickness of the resin layer”.

(4) Light resistance (yellowness change Δb value)
A forced ultraviolet irradiation test was conducted under the following conditions using an ultraviolet deterioration accelerating tester iSuper UV Tester SUV-W131 (manufactured by Iwasaki Electric Co., Ltd.), and then the b value was determined. Three samples were subjected to an acceleration test, the b values before and after the test were measured, and the average value of the differences was defined as light resistance (yellowishness change Δb value).
"UV irradiation conditions"
Illuminance: 100 mW / cm ² , Temperature: 60 ° C., Relative humidity: 50% RH, Irradiation time: 48 hours Light resistance evaluation results are determined as follows. .
Class A: Yellowish change Δb value is less than 5 Class B: Yellowish change Δb value is 5 or more and less than 15 Class C: Yellowish change Δb value is 15 or more.

(5) Luminance and tube unevenness of direct type backlight device Lighted after arranging the white reflective film of the present invention and each optical member described later on the direct type backlight described later, manufactured by Konica Minolta Sensing Co., Ltd. Using a two-dimensional color luminance meter CA-2000, luminance and tube unevenness were measured from the front side of the direct type backlight device as shown in FIG. 3, that is, from the direction perpendicular to the direct type backlight device. Both luminance and uniformity are rectangular in the center of the direct backlight device with a rectangular measurement area, 20 cm in the direction parallel to the fluorescent tube, and 7 times the distance between the centers of adjacent fluorescent tubes in the direction perpendicular to the fluorescent tube Each region was measured by measuring a region where seven fluorescent tubes were placed vertically in the vertical and horizontal directions with the distance as the vertical.

  The luminance was evaluated as the average luminance of the area. As shown in FIG. 4, the tube unevenness is a vertical direction of the region (seven times the distance between the centers of the fluorescent tubes adjacent to each other in the direction perpendicular to the fluorescent tube), that is, a tube unevenness line corresponding to seven fluorescent tubes. In the horizontal direction (20 cm in the direction parallel to the fluorescent tube), 10 equal lines, that is, 10 uneven lines were evaluated at intervals of 2 cm. Next, for one line of tube unevenness, the following formula (1) is used, where Lmax is the average value of 5 points from the highest brightness, Lmin is the average value of 5 points from the lowest brightness, and Lave is the average value of Lmax and Lmin. ) Was used to calculate the degree of uniformity, and the average value of the degree of uniformity for 10 lines of tube unevenness was taken as tube unevenness. The larger the average value, the stronger the tube unevenness, and the smaller the average value, the weaker the tube unevenness.

Uniformity of one line of tube unevenness = (Lmax−Lmin) / Lave− (1)
Furthermore, the relative value from the average value of the uniformity in the models 1 and 2 in the comparative example 1 was obtained as a percentage for the average value of the uniformity in each example and comparative example, and the result was obtained as a tube unevenness evaluation result. The tube unevenness evaluation result is determined by the following, and if it is A to D class, it is acceptable, and A class is most preferable.
Class A: Grade 35% or less Class B: Grade 35% to 45% Grade C: Grade 45% to 55% Class D: Grade 55% to 75% Class E: Grade 75 Greater than%.

The structure of the direct type backlight device used in Examples and Comparative Examples is shown below.
Size: 32 inches (725mm x 413mm, diagonal 834mm)
Diameter of fluorescent tube: 3mm
Number of fluorescent tubes: 19 Distance between centers of fluorescent tubes L: 20.4 mm
Distance H between fluorescent tube center and diffuser plate: 6.5 mm
Distance between center of fluorescent tube and reflection film: 3.0 mm.

The following two types of optical members were installed from the side close to the fluorescent tube, and brightness and tube unevenness were measured respectively.
Model 1: diffusion plate RM803 (manufactured by Sumitomo Chemical Co., Ltd., thickness 2 mm) / diffusion sheet GM3 (manufactured by Kimoto Corp.) two models 2: diffusion plate RM803 (manufactured by Sumitomo Chemical Co., Ltd., thickness 2 mm) / microlens Film UTE II (manufactured by MNTtech Co., Ltd.) 2 sheets Note that the diffusion sheet and the microlens film were placed with the opposite surface of the uneven surface facing the fluorescent tube side.

  Binder resins and compounds used in the examples and comparative examples are shown below.

(1) Binder resin A: Acrylic resin (Foret GS-1000 concentration 30% solution manufactured by Soken Chemical Co., Ltd.)
(2) Binder resin B: Benzotriazole-containing acrylic copolymer resin (Halus Hybrid (registered trademark) UV-G720T concentration 40% solution manufactured by Nippon Shokubai Co., Ltd.)
(3) Particle A: True spherical crosslinked acrylic particle MBX-5 (Sekisui Plastics Co., Ltd., volume average particle diameter 5 μm)
(4) Particle B: True spherical silicone particle Tospearl (Nissho Sangyo Co., Ltd., volume average particle diameter 3 μm)
(5) Particle C: Flat kaolin clay Pororite 102A (manufactured by Imeris Minerals Japan, average flat plane major axis 2 μm, average thickness 0.5 μm or less)
(6) Particle D: Acicular calcium carbonate particle whiscal A (manufactured by Maruo Calcium Co., Ltd., average fiber length 25 μm, average fiber diameter 0.8 μm)
(7) Particle E: Porous amorphous silica silo hobic 100 (manufactured by Fuji Silysia Chemical Ltd., average particle size 2.5 μm).

Example 1
Binder resin B: 1.0 g
Ethyl acetate: 21.5g
Was added with stirring to make a coating solution.

  A three-layered thermoplastic resin film (Lumirror (registered trademark) E6SR, manufactured by Toray Industries, Inc., thickness 188 μm) composed of porous biaxially stretched polyethylene terephthalate was prepared as a white film of the substrate. The said coating liquid was apply | coated to the single side | surface of this base material white film using Metabar # 3, and it heat-dried at 120 degreeC for 1 minute, and obtained the white reflective film of this invention.

(Example 2)
Binder resin A: 11.5g
Ethyl acetate: 13.1 g
Particle A: 0.4 g
Was added with stirring to make a coating solution.

  A three-layered thermoplastic resin film (Lumirror (registered trademark) E6SR, manufactured by Toray Industries, Inc., thickness 188 μm) composed of porous biaxially stretched polyethylene terephthalate was prepared as a white film of the substrate. The said coating liquid was apply | coated to the single side | surface of this base material white film using Metabar # 12, and it heat-dried at 120 degreeC for 1 minute, and obtained the white reflective film.

(Example 3)
Binder resin B: 10.0g
Ethyl acetate: 12.0g
Particle A: 0.5g
Was added with stirring to make a coating solution.

  A three-layered thermoplastic resin film (Lumirror (registered trademark) E6SR, manufactured by Toray Industries, Inc., thickness 188 μm) composed of porous biaxially stretched polyethylene terephthalate was prepared as a white film of the substrate. The said coating liquid was apply | coated to the single side | surface of this base material white film using Metabar # 30, and it heat-dried at 120 degreeC for 1 minute, and obtained the white reflective film of this invention.

Example 4
Binder resin B: 10.0g
Ethyl acetate: 12.4g
Particle B: 0.6g
Was added with stirring to make a coating solution.

  A three-layered thermoplastic resin film (Lumirror (registered trademark) E6SR, manufactured by Toray Industries, Inc., thickness 188 μm) composed of porous biaxially stretched polyethylene terephthalate was prepared as a white film of the substrate. The said coating liquid was apply | coated to the single side | surface of this base material white film using Metabar # 14, and it heat-dried at 120 degreeC for 1 minute, and obtained the white reflective film of this invention.

(Example 5)
Binder resin B: 10.0g
Ethyl acetate: 16.9g
Particle C: 1.7 g
A three-layered thermoplastic resin film (Lumirror (registered trademark) E6SR, manufactured by Toray Industries, Inc., thickness 188 μm) composed of porous biaxially stretched polyethylene terephthalate was prepared as a white film of the substrate. The said coating liquid was apply | coated to the single side | surface of this base material white film using Metabar # 12, and it heat-dried at 120 degreeC for 1 minute, and obtained the white reflective film of this invention.

(Example 6)
Binder resin B: 10.0g
Ethyl acetate: 11.8g
Particle D: 0.4 g
A three-layered thermoplastic resin film (Lumirror (registered trademark) E6SR, manufactured by Toray Industries, Inc., thickness 188 μm) composed of porous biaxially stretched polyethylene terephthalate was prepared as a white film of the substrate. The said coating liquid was apply | coated to the single side | surface of this base material white film using Metabar # 18, and it heat-dried at 120 degreeC for 1 minute, and obtained the white reflective film of this invention.

(Example 7)
Binder resin B: 10.0g
Ethyl acetate: 10.3g
Particle E: 0.1 g
A three-layered thermoplastic resin film (Lumirror (registered trademark) E6SR, manufactured by Toray Industries, Inc., thickness 188 μm) composed of porous biaxially stretched polyethylene terephthalate was prepared as a white film of the substrate. The said coating liquid was apply | coated to the single side | surface of this base material white film using Metabar # 18, and it heat-dried at 120 degreeC for 1 minute, and obtained the white reflective film of this invention.

(Example 8)
Binder resin B: 10.0g
Ethyl acetate: 10.7g
Particle E: 0.2 g
A three-layered thermoplastic resin film (Lumirror (registered trademark) E6SR, manufactured by Toray Industries, Inc., thickness 188 μm) composed of porous biaxially stretched polyethylene terephthalate was prepared as a white film of the substrate. The said coating liquid was apply | coated to the single side | surface of this base material white film using Metabar # 18, and it heat-dried at 120 degreeC for 1 minute, and obtained the white reflective film of this invention.

(Comparative Example 1)
Thermoplastic resin film (Lumirror (registered trademark) E6QD manufactured by Toray Industries, Inc.) provided with a coating layer containing particles on one side of a three-layer base film composed of porous biaxially stretched polyethylene terephthalate as a white reflective film , Substrate film thickness 188 μm) was prepared, and luminance unevenness was evaluated as it was.

(Comparative Example 2)
Binder resin B: 10.0g
Ethyl acetate: 15.6g
Particle A: 1.4g
Was added with stirring to make a coating solution.

  A three-layered thermoplastic resin film (Lumirror (registered trademark) E6SR, manufactured by Toray Industries, Inc., thickness 188 μm) composed of porous biaxially stretched polyethylene terephthalate was prepared as a white film of the substrate. The said coating liquid was apply | coated to the single side | surface of this base material white film using Metabar # 12, and it heat-dried at 120 degreeC for 1 minute, and obtained the white reflective film.

(Comparative Example 3)
Binder resin B: 10.0g
Ethyl acetate: 16.9g
Particle A: 1.7g
Was added with stirring to make a coating solution.

  A three-layered thermoplastic resin film (Lumirror (registered trademark) E6SR, manufactured by Toray Industries, Inc., thickness 188 μm) composed of porous biaxially stretched polyethylene terephthalate was prepared as a white film of the substrate. The said coating liquid was apply | coated to the single side | surface of this base material white film using Metabar # 12, and it heat-dried at 120 degreeC for 1 minute, and obtained the white reflective film.

(Comparative Example 4)
Binder resin B: 10.0g
Ethyl acetate: 14.5g
Particle A: 1.1 g
Was added with stirring to make a coating solution.

  A three-layered thermoplastic resin film (Lumirror (registered trademark) E6SR, manufactured by Toray Industries, Inc., thickness 188 μm) composed of porous biaxially stretched polyethylene terephthalate was prepared as a white film of the substrate. The said coating liquid was apply | coated to the single side | surface of this base material white film using Metabar # 12, and it heat-dried at 120 degreeC for 1 minute, and obtained the white reflective film.

  In any of Examples 1 to 8, the effect of suppressing tube unevenness was observed. Regarding the glossiness according to JIS K 7105 (1981) measured from the surface provided with the resin layer of the white film, the 60 ° glossiness is 30 or more or “value obtained by dividing the 60 ° glossiness by 20 ° glossiness”. The white reflective film of 4 or more has an effect of further suppressing tube unevenness (Examples 2 to 8), the 60 ° glossiness is 30 or more, and “a value obtained by dividing the 60 ° glossiness by the 20 ° glossiness”. In particular, the white reflective film having a thickness of 4 or more was effective in suppressing tube unevenness (Examples 7 and 8). Furthermore, the white film containing particles whose average particle diameter is smaller than the thickness of the resin layer in the resin layer also has an effect of suppressing tube unevenness (Examples 4 to 8), and the particles are indefinite. Even in the case of particles having a flat shape or a needle shape, the effect of suppressing tube unevenness was observed (Examples 5 to 8). Especially, when the said particle | grain is porous, the effect which suppresses tube | pipe nonuniformity was seen more (Example 7, 8).

  In addition, the resin layer containing an ultraviolet absorber and / or a light stabilizer and having a sufficient thickness of the resin layer could not only suppress tube unevenness but also provide light resistance (implementation) Examples 3-8).

  On the other hand, the glossiness according to JIS K 7105 (1981) measured from the surface provided with the resin layer is “60 ° glossiness is less than 25” or / and ““ 60 ° glossiness is divided by 20 ° glossiness. When the “value” was less than 2.5, the effect of suppressing tube unevenness was not observed (Comparative Examples 1 to 4).

1: White reflective film 2: Substrate white film having a three-layer structure 3: Resin layer 4: Layer containing inorganic particles and / or bubbles 5: Fluorescent tube 6: Diffuser 7: Luminance meter 8: Tube unevenness and luminance Evaluation area 9: Pipe unevenness evaluation line

Claims (5)

At least one resin layer is laminated on at least one surface of the white film, and the glossiness according to JIS K 7105 (1981) measured from the surface provided with the resin layer is the same as the following (i) and (ii) White reflective film to fill.
(I) The 60-degree glossiness is 25 or more (ii) The value obtained by dividing the 60-degree glossiness by the 20-degree glossiness is 2.5 or more.   The white reflective film according to claim 1, wherein the resin layer contains particles, and a maximum particle diameter in a cross section of the resin layer perpendicular to a film surface of the particles is smaller than a thickness of the resin layer. The white reflective film according to claim 2 , wherein the particle has an indefinite shape, a flat shape, or a needle shape. The white reflective film according to claim 2 , wherein the particles are porous. A direct-type backlight configured using the white reflective film according to claim 1.

Images