JP2008286907A - Laminate for reflection - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laminate for reflection which attains prevention of light leakage and luminance improvement of a liquid crystal backlight. <P>SOLUTION: The laminate is constituted by laminating a white film or a film, having a metallic layer on both surfaces of a light-shielding layer containing particles. In the laminate for reflection, the particles are contained in the light-shielding layer so that ratio S/L is smaller than 1.0, wherein S denotes average projected area of particles observed from a direction which is parallel to a laminate surface and L denotes average projected area of particles observed from a direction which is vertical to the laminate surface. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a reflective laminate for improving the luminance of a liquid crystal backlight, and more particularly to a reflection plate for a surface light source of an edge light and a direct light for a liquid crystal display, and a member used for a double-sided light source. Is.

  Backlights that illuminate liquid crystal cells are used in liquid crystal displays. Depending on the type of liquid crystal display, an edgelight type backlight is used for liquid crystal monitors, and a direct type backlight is used for liquid crystal televisions. As these reflective films for a backlight, a porous white film formed of bubbles is generally used (Patent Document 1). Furthermore, in order to prevent yellow discoloration of the film due to ultraviolet rays radiated from the cold cathode tube, a white film in which an ultraviolet absorbing layer is laminated has been proposed (Patent Documents 2 and 3).

Various methods for improving various characteristics of luminance in these reflective films have been disclosed. For example, a method of providing a light shielding layer on the film surface opposite to the light source and a method of providing a film on both surfaces of the light shielding layer containing particles are disclosed in order to improve the brightness in the edge light system (patent) References 4, 5).
JP-A-8-262208 JP 2001-166295 A JP 2002-90515 A JP 2002-333510 A JP 2005-99314 A

  In a rapidly growing reflective film for liquid crystal televisions, cost reduction is strongly demanded, while improvement of the reflective properties of the reflective film is also demanded at the same time. This is because if the luminance as a backlight is improved by improving the reflection characteristics of the reflective film, the expensive sheet used on the upper part of the light source can be reduced. For example, as an example of the configuration of a backlight for a liquid crystal television, from the light source side to the light source side, a diffusion plate (thickness of about 2 mm) / diffusion film (thickness of about 200 μm to 300 μm) / diffusion film (thickness of about 200 μm to 300 μm) / diffusion film ( If the brightness of the entire backlight is improved by 2 to 3%, one diffusion film can be reduced in the above configuration.

  However, the reflection characteristics of the reflection film often depend on the void structure inside the white film, but the improvement of the reflection characteristics by devising the void structure is becoming a limit. Further, due to the backlight structure, light transmitted through the white film leaks light due to a metal or plastic joint used for the casing, and the light is lost.

  Unlike the above-described conventional methods, the present invention provides a light shielding property in a laminate in which a film having a white film or a metal layer is laminated on both sides of the light shielding layer, with the light shielding layer having a specific configuration. It is an object of the present invention to provide a reflective laminate that improves and contributes to improving the luminance of a backlight.

  The present invention employs the following means in order to solve such problems. That is, a laminate in which a film having a white film and / or a metal layer is laminated on both surfaces of a light shielding layer containing particles, and the average projected area of the particles observed from a direction parallel to the laminate surface The reflective laminate is contained in the light shielding layer so that the ratio S / L between S and the average projected area L of the particles observed from the direction perpendicular to the laminate surface is less than 1.0.

Moreover, the preferable aspect of the laminated body for surface light source reflective members of this invention is as follows.
(1) The refractive index difference between the particles and the binder resin in the light shielding layer is 0.05 or more,
(2) The shape of the particles is at least one selected from the group consisting of a star shape, a flat shape, a diamond shape, and a rectangular shape,
(3) The particles are contained so that the flat surface is parallel to the laminate surface,
(4) The shape of the particles is acicular and / or confetti.
(5) The sum of the average reflectance at a wavelength of 400 to 700 nm on both surfaces of the laminate is 140% or more,
(6) The thickness of the light shielding layer is 5 μm or more,
(7) having a coating layer containing an ultraviolet absorber and / or a light stabilizer on at least one surface of the laminate;
Is to satisfy.

  Further, the present invention is a direct-type liquid crystal backlight using the reflective laminate of the present invention, and a double-sided light source having light sources on both sides of the reflective laminate of the present invention.

  According to the present invention, loss due to light leakage is reduced by using a laminate for a surface light source reflecting member in which a film having a white film or a metal layer is laminated on both sides of a specific light shielding layer, and used for a backlight. In this case, it is possible to contribute to improvement of the luminance of the backlight.

  In the present invention, the reflection laminate which contributes to the above-described problem, that is, the improvement of the luminance of the backlight, has been studied sharply. As a result, a film having a white film or a metal layer is laminated on both sides of the light shielding layer, and the shape of the particles contained in the light shielding layer, and further, the particles are contained in the light shielding layer so as to satisfy a specific condition. As a result, it was confirmed that the reflection characteristics and the light shielding properties were improved and the luminance enhancement effect when used in the backlight was confirmed, and that this problem was solved at once.

  The reflective laminate of the present invention is obtained by laminating a film having a white film or a metal layer on both sides of a light shielding layer, and has a light shielding effect and a reflection effect on both sides when incorporated in a liquid crystal backlight. Therefore, the brightness of the backlight is improved, so that it can be used as a double-sided light source.

  In the present invention, it is necessary to contain non-spherical particles in the light shielding layer so as to satisfy specific conditions. The term “aspherical shape” as used herein means a shape other than a true spherical shape. The ratio S / L between the average projected area S of the particles observed from a direction parallel to the laminate surface and the average projected area L of the particles observed from a direction perpendicular to the laminate surface is less than 1.0. In the light shielding layer. When S / L is contained so as to be less than 1.0, particles can be contained in any number of layers in the thickness direction in the light shielding layer as shown in FIGS. When observed from above, the particles appear to overlap. When considering the interface between the binder resin and the particles that make up the light shielding layer, if the particles are contained in layers like this, there will be more interfaces that are exposed to light incident from the direction perpendicular to the laminate surface. Therefore, the shielding property of reflecting or absorbing the light can be improved. 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 non-spherical particles that can be contained so that the 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, Examples include confetti, irregular shape, and the like. If the S / L is 1.0 or more when the particle shape is a true sphere shape, it becomes difficult to contain particles in the thickness direction of the light shielding layer, and the effect of improving the light shielding property cannot be obtained. .

  In the present invention, if the particle to be added is the non-spherical shape, black pigment, black dye, carbon black, and acetylene black whose refractive index difference is difficult to measure with a binder resin in the light shielding layer as described later are constituents. Even in the case of the particles, the interface that absorbs light increases and the shielding property can be improved.

  Here, “average projected area S”, “average projected area L”, and “ratio S / L” are obtained as follows. First, the reflective laminate of the present invention is cut in a direction perpendicular to the laminate surface at a knife inclination angle of 3 ° using a rotary microtome manufactured by Nippon Microtome Research Co., Ltd. The light shielding layer cross section of the obtained laminate is observed using a scanning electron microscope ABT-32 manufactured by Topcon Corporation. The observation magnification is a magnification at which at least 20 particles contained in the light shielding 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, after peeling the film one surface of the laminate, the light shielding layer surface is similarly observed from the direction perpendicular to the laminate surface, and the average value of the projected areas of a total of 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.

  The particles contained in the light shielding layer preferably have a refractive index difference of 0.05 or more with respect to the binder resin in the light shielding layer. If there is a difference in the refractive index, more light is reflected and absorbed at the interface between the binder resin and the particles, thereby improving the light shielding property. The difference in refractive index is preferably 0.15 or more, more preferably 1.00 or more.

  Here, the refractive index is a ratio of changing the angle of the traveling direction at the boundary of the medium where different waves (light rays or the like) travel in a straight line, and is a value specific to a substance based on a vacuum. Furthermore, the refractive index difference here is the absolute value of the difference between the refractive index of the binder resin and the refractive index of the particles when observed at the same wavelength, even if the difference in refractive index is a negative value. The absolute value, that is, a positive value is the refractive index difference.

  Here, “the refractive index of the binder” and “the refractive index of the particles” are obtained as follows. First, a binder resin is extracted from the light shielding layer using a solvent, and after the solvent is distilled off, measurement is performed at 25 ° C. by an ellipsometry method. The value obtained here is referred to as “binder refractive index”. Next, the light shielding layer was immersed in a solvent, and the light shielding layer was peeled and collected, and then the particles were dropped from the light shielding layer by pressing and sliding on a slide glass. The particles obtained here were confirmed by the Becke line detection method at the temperature where the refractive index of each liquid organic compound was known to be invisible, and the refractive index of the liquid organic compound used at this time was changed to “ The refractive index of the particles ”.

  The component of the binder resin used in the light shielding layer according to the present invention 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, etc. may be used alone, or two or more kinds of copolymers or mixtures selected from the above resin group may be used. Among these, acrylic resin, methacrylic resin, polyurethane resin, and polyester resin are preferably used from the viewpoint of heat resistance and price.

  Although the component of the particle | grains contained in the light-shielding layer concerning this invention is not specifically limited, It is preferable that a refractive index difference with binder resin is 0.05 or more. Since the refractive index of the binder resin is 1.4 to 1.6, particles having a refractive index difference of 0.05 or more are various metals including alloys, various metal oxides, organic resins, mixtures of organic resins, Examples of metals and metal oxides include calcium carbonate, anatase titanium oxide, rutile titanium oxide, kaolin, silver, aluminum, gold, copper, platinum, zinc, zinc oxide, lead oxide, antimony oxide, oxidation Aluminum, magnesium oxide, chromium oxide, and the like are listed. Examples of organic substances include polystyrene resin, acrylic resin, silicone resin, nylon resin, benzoguanamine resin, urethane resin, and two or more kinds of copolymers or mixtures selected from these resin groups. Etc.

  Various additives may be added to the light shielding layer according to the present invention as long as the effects of the invention are not impaired. Examples thereof include organic or inorganic pigments and dyes, adhesives, crosslinking agents, heat stabilizers, oxidation stabilizers, organic or inorganic particles, antistatic agents, and dispersants. In particular, it is preferable to add a black pigment, dye, or metal paste that absorbs light, such as carbon black and acetylene black, in order to further improve the light shielding property, and to maintain the shape as a laminate, adhesive or adhesive It is preferable to add an agent.

  The particles contained in the light shielding layer according to the present invention are preferably contained in a star shape, a flat shape, a rhombus shape, or a rectangular shape so that the flat surface is parallel to the laminate surface. When present in parallel to the laminate surface, more particles overlap in the thickness direction of the light shielding layer, and reflection or absorption between the particles is repeated, so that the light shielding property can be improved more effectively. The thickness of the light shielding layer according to the present invention is preferably 5 μm or more. If the thickness is less than 5 μm, not only the adhesion to the laminated film becomes insufficient and defects such as peeling occur, but also there is a possibility that the interface having the absolute amount or refractive index difference of the particles is reduced and the light shielding property is not improved. There is. The thickness of the light shielding layer is preferably 5 μm or more, more preferably 10 μm or more, and further preferably 20 μm or more.

  As a method for forming the light shielding layer according to the present invention, a method of directly providing the light shielding layer on the inner surface of a white film or a film having a metal layer can be used.

  As a method for forming the light shielding layer, a method of providing a coating layer containing a binder resin, non-spherical particles and additives, a method of providing a binder resin, non-spherical particles, a resin layer containing additives, and the like can be used. .

  In order to provide a coating layer containing a binder resin, non-spherical particles, and additives, a light shielding layer is applied by applying a coating material for the light shielding layer on the surface to be coated, removing excess solvent and moisture by a drying process, Then, it is cured by light, electron beam, radiation or the like to form a light shielding layer. As a means for coating, for example, gravure coating, micro gravure coating, roll coating, spin coating, reverse coating, bar coating, screen coating, blade coating, air knife coating, dipping and the like can be used.

  In order to provide a light shielding layer by providing a resin layer containing a binder resin, non-spherical particles, and additives, an easy-adhesion layer is provided in some cases, and a melt of these binder resin, non-spherical particles, and additives is added to the light shielding layer. Dry lamination after extruding to the surface to be formed, molten resin paint mixed with these binder resins, non-spherical particles, additives and, in some cases, solvents, by casting or uniaxial stretch molding. The method of bonding to the formation surface of a light-shielding layer can be used.

  The laminate according to the present invention preferably has a sum of average reflectances of 140% or more at wavelengths of 400 to 700 nm on both sides. More preferably, it is 160% or more, and particularly preferably 180% or more. If the sum of the average reflectances is less than 140%, the light shielding property may be insufficient, or the luminance may be insufficient depending on the applied liquid crystal display. Here, the reflectance refers to the total reflectance, and is obtained based on the total amount of specular reflection light and diffuse reflection light.

  The film used for the laminate according to the present invention (hereinafter referred to as a base film) should have a higher visible light reflectance because the sum of the average reflectances satisfies 140% or more. A film or a film having a metal layer is used. Whether a white film is laminated on both sides of the light shielding layer, a film having a metal layer on both sides is laminated, a white film is laminated on one side, and a film having a metal layer is laminated on the other side Good. Although it is not limited as a film having a metal layer, as a film having a metal layer, on a transparent, semi-transparent, white substrate film, vapor deposition, sputtering, using silver or aluminum or a metal paste thereof, It is preferable that the metal thin film layer is formed by laminating or coating. The white film is not limited, but a porous unstretched or biaxially stretched polypropylene film or a porous unstretched or stretched polyethylene terephthalate film is preferably used as an example. 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, the porous white biaxially stretched polyethylene terephthalate film disclosed in JP-A-2002-90515 is particularly preferable as the white film according to the present invention for the reasons described above.

  In the present invention, the following white film may be used to maximize the luminance of the backlight. In the case of a white film having a three-layer structure of A layer / B layer / A layer, the A layer corresponding to the film surface is 0.5 weight with respect to the total weight of each A layer with inorganic particles and / or organic particles in the polyester. % Or less is preferable. The content is more preferably 0.1% by weight or less, particularly preferably 0.07% by weight or less. Further, in the case of a white film having a three-layer structure of A layer / B layer / C layer, the A layer and / or C layer corresponding to the film surface is composed of polyester and inorganic particles and / or organic particles, and each layer (inorganic fine particles and The layer is preferably 0.5% by weight or less based on the total weight of (or the layer containing organic particles). The content is more preferably 0.1% by weight or less, particularly preferably 0.07% by weight or less.

Next, although the manufacturing method of the said white film is demonstrated, it is not limited to this example. Polymethylpentene is added as an incompatible polymer, and polyethylene glycol, polybutylene terephthalate and polytetramethylene glycol copolymer are added as a low specific gravity agent to 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. If necessary, polyethylene terephthalate containing an inorganic additive such as SiO ₂ is supplied to the extruder A by a conventional method. In the T-die three-layer die, the composition of A layer / B layer / A layer is such that the polymer of the extruder B comes to the inner layer (B layer) and the polymer of the extruder A comes to both surface layers (A layer). You may laminate | stack on these 3 layers.

  The melted 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 holding both ends of the longitudinally stretched film with clips. 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. If the area magnification is less than 9, the whiteness of the resulting film will be poor. 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, and after uniform cooling, the film is cooled to room temperature. And it winds with a winder and obtains a white film.

  The reflective laminate of the present invention may deteriorate the substrate film by light emitted from a lamp such as a cold cathode tube during use as a backlight, particularly ultraviolet rays (for example, optical deterioration such as yellowing or low And a coating layer containing an ultraviolet absorber and / or a light stabilizer in the binder resin layer (hereinafter referred to as a light-resistant coating layer) on the lamp surface side of the base film. preferable.

  The binder resin for the light-resistant coating layer is not particularly limited, but a resin mainly composed of organic components is preferable. For example, polyester resin, polyurethane resin, acrylic resin, methacrylic resin, polyamide resin, polyethylene resin, polypropylene resin, polyvinyl chloride Examples of the resin include 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. Of these, polyester resins, polyurethane resins, acrylic or methacrylic resins are preferably used in terms of heat resistance, particle dispersibility, coatability, and glossiness. In terms of the light resistance of the lamp surface side coating layer, it is more preferable that the binder resin layer also contains an ultraviolet absorber and a light stabilizer.

The resin constituting the resin layer containing the ultraviolet absorber is not particularly limited, but a resin containing an inorganic ultraviolet absorber such as titanium oxide or zinc oxide, a resin containing an organic ultraviolet absorber such as benzotriazole or benzophenone, Alternatively, a resin obtained by copolymerizing a benzotriazole-based or benzophenone-based reactive monomer can be used.
As the resin constituting the resin layer containing the light stabilizer, it is preferable to use an organic ultraviolet absorbing resin including a resin copolymerized with a hindered amine (HALS) -based reactive monomer.

  As the inorganic ultraviolet absorber, zinc oxide, titanium oxide, cerium oxide, zirconium oxide and the like are generally used. Among these, at least one selected from the group consisting of zinc oxide, titanium oxide, and cerium oxide is preferably used because it does not bleed out and is excellent in light resistance. 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 zinc oxide, FINEX-25LP, FINEX-50LP (manufactured by Sakai Chemical Industry Co., Ltd.) or the like can be used.

Organic UV absorbers include resins containing organic UV absorbers such as benzotriazole and benzophenone, resins obtained by copolymerizing benzotriazole and benzophenone reactive monomers, and hindered amine (HALS) reactivity. A resin obtained by copolymerizing a light stabilizer such as a monomer can be used. In particular, organic UV-absorbing resins containing a resin copolymerized with a benzotriazole-based or benzophenone-based reactive monomer, and further a resin copolymerized with a hindered amine (HALS) -based reactive monomer have a high UV absorbing effect in a thin layer. 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.

  The reflective laminate according to the present invention may contain spherical particles in the coating layer provided on the lamp surface side of the base film in order to improve the anti-blocking property and the luminance when incorporated in the backlight. The kind of the spherical particles is not particularly limited, and any organic or inorganic type can be used. As the organic spherical particles, acrylic resin particles, silicone resin particles, nylon resin particles, styrene resin particles, polyethylene resin particles, polyamide resin particles such as benzoguanamine, urethane resin particles, etc. may be used. it can. As the inorganic spherical particles, silica, aluminum hydroxide, aluminum oxide, zinc oxide, barium sulfide, magnesium silicate, or a mixture thereof can be used. From the viewpoint of dispersibility with commonly used resin binders, coating properties, economy, and the like, it is preferable to use organic spherical particles. Among them, a copolymer of an acrylic vinyl monomer and a styrene vinyl monomer can be suitably used in the present invention because the refractive index can be changed by adjusting two kinds of copolymerization ratios.

  In the present invention, since it is necessary to disperse the spherical particles in the solvent in the coating step of the coating layer provided on the lamp surface side of the base film, since the solvent resistance is necessary, the spherical particles have a crosslinked structure. It is preferable to have. When it does not have a crosslinked structure, spherical particles are eluted in the coating step, and it becomes impossible to provide a coating layer in which the particle shape and particle size are maintained.

  In order to form a crosslinked structure, it is preferable to form a crosslinked structure using a vinyl compound having a plurality of functional groups in one molecule, and in the present invention, in particular, a vinyl compound having a plurality of functional groups in one molecule. As such, a polyfunctional acrylic compound such as a bifunctional acrylic compound, a trifunctional acrylic compound, or a tetrafunctional or higher polymerizable acrylic compound can be used.

  In the present invention, "Techpolymer" (manufactured by Sekisui Plastics Co., Ltd.) can be used. If the coefficient of variation is less than 30%, the S series is preferred, and if the coefficient of variation is less than 15%, Spherical particles made of a copolymer of methyl methacrylate and ethylene glycol dimethacrylate, such as the SSX series, can be most suitably used.

  In the spherical particles in the coating layer provided on the lamp surface side of the substrate film according to the present invention, when a UV absorber and / or a light stabilizer is added, or when these resins are produced, the reactive double In some cases, chemical bonding is carried out by copolymerization with a UV absorber having a bond and / or a light stabilizer. In view of less bleeding out from the spherical particles, it is preferable to fix the ultraviolet absorber and / or the light stabilizer by chemical bonding as in the latter case.

  The ultraviolet absorbers and light stabilizers contained in the spherical particles are roughly classified into inorganic types and organic types. As inorganic ultraviolet absorbers, titanium oxide, zinc oxide, cerium oxide, and the like are generally known, and zinc oxide is most preferable in terms of economy, ultraviolet absorption, and photocatalytic activity.

  Examples of 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 as a base material may be deteriorated in a chain by these radicals. In order to capture these radicals and the like, a light stabilizer is preferably used in combination, and a hindered amine compound is used.

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

  2- (2′-hydroxy-5′-methacryloxyethylphenyl) -2H-benzotriazole (trade name: RUVA-93); manufactured by Otsuka Chemical Co., Ltd. And a hindered amine compound substituted with a reactive vinyl monomer, 4-methacryloyloxy-2,2,6,6-tetramethylpiperidine (“Adeka Stab LA-82”; ADEKA Co., Ltd.) can be used.

  In the present invention, if the difference in refractive index between the binder resin and the spherical particles in the coating layer provided on the lamp surface side of the base film is reduced as much as possible, the luminance is improved and the light resistance of the coating layer is also improved. The copolymer component and the monomer composition of the resin binder and the spherical particles are preferably the same. However, since the resin binder component needs to be diluted in a solvent in the coating step, it is preferable that the resin binder component does not have a crosslinked structure. In that sense, it is preferable that the resin binder component does not contain the polyfunctional acrylic compound. Furthermore, since the light resistance of the coating layer is also improved, the copolymer component of the resin binder and the spherical particles, the monomer composition, the ultraviolet absorber, and the light stabilizer are preferably the same.

  The coating layer provided on the lamp surface side of the base film according to the present invention can be coated by any method. For example, methods such as gravure coating, roll coating, spin coating, reverse coating, bar coating, screen coating, blade coating, air knife coating and dipping can be used. In addition, the coating liquid for forming the coating layer may be applied at the time of film production of the substrate (in-line coating), or may be applied on the film after completion of crystal orientation (off-line coating).

  The reflective laminate of the present invention thus obtained can prevent light leakage of the liquid crystal backlight and improve the luminance. Further, according to a preferred embodiment, the reflectance does not decrease much even when used for a long time. It can be advantageously used as an edge light and a direct light for a liquid crystal screen or a reflector for a double-sided surface light source and a reflector.

  The measurement method and evaluation method are shown below.

(1) Refractive index of binder resin, refractive index of spherical particles When the refractive index values of the binder resin and spherical particles are unknown, the refractive index is determined by the following procedure. First, the binder resin is extracted from the coating layer using an organic solvent, and after the organic solvent is distilled off, measurement is performed on light having a wavelength of 589.3 nm at 25 ° C. by an ellipsometry method. The value obtained here is defined as “the refractive index of the binder resin”.
Next, the coating layer was immersed in an organic solvent, and the coating layer was peeled and collected, and then the spherical particles were dropped from the coating layer by pressing and sliding on a slide glass. The spherical particles obtained here were confirmed by the Becke line detection method to confirm that the contours of the particles could not be seen at a temperature where the refractive index of each liquid organic compound was known, and the refractive index of the liquid organic compound used at this time was determined. It is assumed that “the refractive index of the spherical particles”.

(2) Average shadow area S, average projected area L, ratio S / L of particles in the light shielding layer
Samples prepared in each example and comparative example are cut in a direction perpendicular to the laminate surface at a knife inclination angle of 3 ° using a rotary microtome manufactured by Japan Microtome Laboratory. The light shielding layer cross section of the obtained laminate is observed using a scanning electron microscope ABT-32 manufactured by Topcon Corporation. The observation magnification is a magnification at which at least 20 particles contained in the light shielding 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, after peeling the film one surface of the laminate, the light shielding layer surface is similarly observed from the direction perpendicular to the laminate surface, and the average value of the projected areas of a total of 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) Total light transmittance Based on JIS K7361-1, using a turbidimeter (cloudiness meter) NDH2000 (manufactured by Nippon Denshoku Industries Co., Ltd.), the total light transmittance in the laminate thickness direction is measured on both sides. The average value was calculated by measurement. An average value was calculated for three samples, and this was taken as the total light transmittance.

(4) Average reflectance 10 nm at a wavelength of 400-700 nm with a φ60 integrating sphere 130-0632 (Hitachi Ltd.) and a 10 ° C. inclined spacer attached to a spectrophotometer U-3410 (Hitachi Ltd.) The average value of the total reflectance of the interval was calculated on both sides. Part number 210-0740 manufactured by Hitachi Instrument Service Co., Ltd. was used for the standard white plate. An average value was calculated for three samples, and this was used as an average reflectance.

(5) Average reflectance after durability test Using a UV degradation acceleration tester iSuper UV Tester SUV-W131 (Iwasaki Electric Co., Ltd.), a substrate film 1 described later is subjected to a forced ultraviolet irradiation test under the following conditions. After doing so, the average reflectance was determined. An average value was calculated for three samples, and this was taken as the average reflectance after the durability test.
"UV irradiation conditions"
Illuminance: 100 mW / cm ² , temperature: 60 ° C., relative humidity: 50% RH, irradiation time: 72 hours.

(6) Average brightness 21-inch direct backlight (lamp tube diameter: 3 mmΦ, number of lamps: 12, distance between lamps: 25 mm, distance between reflection film and lamp center: 4.5 mm, distance between diffuser plate and lamp center: 13.5 mm) was used, and brightness measurement was performed with the surface of the base film 1 described later facing the lamp side in the optical sheet configuration in the following two models.
Model 1: Diffusion plate RM803 (Sumitomo Chemical Co., Ltd., thickness 2 mm) / Diffusion sheet GM3 (Kimoto Co., Ltd., thickness 100 μm) 2 sheets Model 2: Diffusion plate RM803 (Sumitomo Chemical Co., Ltd., thickness 2 mm) / Diffusion sheet GM3 (manufactured by Kimoto Co., Ltd., thickness 100 μm) / prism sheet BEF-II (manufactured by 3M, thickness 130 μm) / polarized light separation sheet DBEF (manufactured by 3M, thickness 400 μm)
In the luminance measurement, the cold cathode ray tube lamp was turned on for 60 minutes to stabilize the light source, and then the luminance (cd / m ² ) was measured using a color luminance meter BM-7fast (manufactured by Topcon Corporation). An average value was calculated for three samples, and this was used as the average luminance.

Example 1
As a coating liquid for forming a light-resistant coating layer, Hals Hybrid (registered trademark) UV-G13 (acrylic copolymer, 40% concentration solution, manufactured by Nippon Shokubai Co., Ltd.): 10.0 g, toluene: 18.9 g A coating liquid was prepared by adding while stirring. This coating solution was applied and dried using Metabar # 12 on one side of a white film (Lumirror (registered trademark) E6SL, manufactured by Toray Industries, Inc.) made of 250 μm porous biaxially stretched polyethylene terephthalate. A base film 1 having a light-resistant coating layer with an application amount of 4.0 g / m ² was obtained.

  Next, as a coating liquid for forming a light shielding layer, an acrylic pressure-sensitive adhesive 8319 (30% concentration solution, refractive index 1.49, manufactured by Resino Color Industry Co., Ltd.): 10.0 g, flat kaolin particles (Porarite 102A, solid A coating liquid was prepared by adding 100% min, average particle size 2 μm, refractive index 1.56, manufactured by Imerizu Minerals Japan Co., Ltd.): 0.3 g, toluene: 9.7 g while stirring. The coating liquid was applied and dried using Metabar # 40 (Co., Ltd.) on the opposite surface of the base film 1 having the light-resistant coating layer to provide a light shielding layer with a coating layer thickness of 10 μm. . The light shielding layer surface and a white film made of biaxially stretched polyethylene terephthalate containing 38 μm titanium oxide (Lumirror (registered trademark) E20 manufactured by Toray Industries, Inc.) were dry laminated and bonded to obtain a reflective laminate. .

(Example 2)
As a coating solution for forming a light shielding layer, an acrylic pressure-sensitive adhesive 8319 (30% concentration solution, refractive index 1.49, manufactured by Resino Color Industry Co., Ltd.): 10.0 g, flat kaolin particles (Porarite 102A, solid content 100) %, Average particle diameter 2 μm, refractive index 1.56, manufactured by Imerizu Minerals Japan): 0.3 g, Toka Black # 8500 / F (carbon black, solid content 100%, manufactured by Tokai Carbon Co., Ltd.): A coating liquid prepared by adding 0.3 g and toluene: 11.2 g with stirring was prepared. On the opposite side of the surface of the base film 1 obtained in the same manner as in Example 1 having the light-resistant coating layer, this coating solution was applied and dried using Metabar # 40 (Co). A light shielding layer having a coating layer thickness of 10 μm was provided. The light shielding layer surface and a white film made of biaxially stretched polyethylene terephthalate containing 38 μm titanium oxide (Lumirror (registered trademark) E20 manufactured by Toray Industries, Inc.) were dry laminated and bonded to obtain a reflective laminate. .

(Example 3)
As a coating liquid for forming a light shielding layer, an acrylic pressure-sensitive adhesive 8319 (30% concentration solution, refractive index 1.49, manufactured by Resino Color Industry Co., Ltd.): 10.0 g, flat kaolin particles (Porarite 102A, average particle size) Example 1 Using a coating liquid obtained by adding 2 μm, solid content of 100%, refractive index of 1.56, manufactured by Imerizu Minerals Japan Ltd.): 0.3 g, toluene: 9.7 g with stirring. The surface of the base film 1 obtained in the same manner as described above was coated and dried using Metabar # 24, on the surface opposite to the surface having the light-resistant coating layer, and a light shielding layer having a coating layer thickness of 6 μm was provided. It was. This light shielding layer surface and an aluminum vapor deposition surface of a 25 μm aluminum vapor deposition film (Metal Me (registered trademark) Metal Me S, manufactured by Toray Film Processing Co., Ltd.) were dry laminated and bonded to obtain a reflective laminate.

Example 4
As a coating liquid for forming a light shielding layer, an acrylic pressure-sensitive adhesive 8319 (30% concentration solution, refractive index 1.49, manufactured by Resino Color Industry Co., Ltd.): 10.0 g, flat kaolin particles (Porarite 102A, average particle size) 2 μm, solid content 100%, refractive index 1.56, manufactured by Imerizu Minerals Japan): 0.3 g, Toka Black # 8500 / F (carbon black, solid content 100%, manufactured by Tokai Carbon Co., Ltd.): A coating liquid prepared by adding 0.3 g and toluene: 11.2 g with stirring was prepared. On the surface opposite to the surface having the light-resistant coating layer of the base film 1 obtained in the same manner as in Example 1, this coating solution was applied and dried using Metabar # 16. A light shielding layer having a layer thickness of 4 μm was provided. This light shielding layer surface and an aluminum vapor deposition surface of a 25 μm aluminum vapor deposition film (Metal Me (registered trademark) Metal Me S, manufactured by Toray Film Processing Co., Ltd.) were dry laminated and bonded to obtain a reflective laminate.

(Example 5)
The light shielding layer contains star-shaped titanium oxide particles (star-shaped titanium oxide fine powder, solid content 100%, crystal grain size 0.5 μm, refractive index 2.52, manufactured by Sumitomo Osaka Cement Co., Ltd.) A reflective laminate was obtained in the same manner as in Example 2 except that.

(Example 6)
The light shielding layer contains star-shaped titanium oxide particles (star-shaped titanium oxide fine powder, solid content 100%, crystal grain size 0.5 μm, refractive index 2.52, manufactured by Sumitomo Osaka Cement Co., Ltd.) A reflective laminate was obtained in the same manner as in Example 3 except that.

(Example 7)
Rhomboidal calcite crystal-type calcium carbonate particles (CUBE-18BHS, average particle size 1.8 μm, solid content 100%, refractive index 1.65, Maruo Calcium Co., Ltd.) A laminate for reflection was obtained in the same manner as in Example 2 except that (manufactured) was used.

(Example 8)
Rhomboidal calcite crystal-type calcium carbonate particles (CUBE-18BHS, average particle size 1.8 μm, solid content 100%, refractive index 1.65, Maruo Calcium Co., Ltd.) The laminate for reflection was obtained in the same manner as in Example 3 except that (manufactured) was used.

Example 9
Except that the particles contained in the light shielding layer are confetti-like aragonite crystalline calcium carbonate particles (solid content 100%, average particle size 2.0 μm, refractive index 1.65, manufactured by Maruo Calcium Co., Ltd.) A reflective laminate was obtained in the same manner as in Example 2.

(Example 10)
Except that the particles contained in the light shielding layer are confetti-like aragonite crystalline calcium carbonate particles (solid content 100%, average particle size 2.0 μm, refractive index 1.65, manufactured by Maruo Calcium Co., Ltd.) A reflective laminate was obtained in the same manner as in Example 3.

(Example 11)
Aragonite crystal-type calcium carbonate particles (whisker A), average fiber length 25 μm, average fiber diameter 1.0 μm, solid content 100%, refractive index 1.63, Maruo calcium A reflective laminate was obtained in the same manner as in Example 2 except that (made by Co., Ltd.) was used.

(Example 12)
Aragonite crystal-type calcium carbonate particles (whisker A), average fiber length 25 μm, average fiber diameter 1.0 μm, solid content 100%, refractive index 1.63, Maruo calcium A reflective laminate was obtained in the same manner as in Example 3 except that (made by Co., Ltd.) was used.

(Example 13)
The particles contained in the light shielding layer are flat polystyrene particles (TECHPOLYMER (registered trademark) LMX series, average particle size 3.0 μm, solid content 100%, refractive index 1.59, manufactured by Sekisui Plastics Co., Ltd.). A reflective laminate was obtained in the same manner as in Example 2 except that it was used.

(Example 14)
The particles contained in the light shielding layer are flat polystyrene particles (TECHPOLYMER (registered trademark) LMX series, average particle size 3.0 μm, solid content 100%, refractive index 1.59, manufactured by Sekisui Plastics Co., Ltd.). A reflective laminate was obtained in the same manner as in Example 3 except that it was used.

(Comparative Example 1)
Evaluation was performed only with a white film (Lumirror (registered trademark) E6SL, manufactured by Toray Industries, Inc.) made of 250 μm porous biaxially stretched polyethylene terephthalate.

(Comparative Example 2)
Addition of acrylic adhesive 8319 (30% concentration solution, refractive index 1.49, manufactured by Resino Color Industry Co., Ltd.): 10.0 g, toluene: 8.2 g as a light shielding layer forming coating solution with stirring A coating liquid was prepared. A white film made of 250 μm porous biaxially stretched polyethylene terephthalate (Lumirror (registered trademark) E6SL manufactured by Toray Industries, Inc.) is used as the base film 1 without using a light-resistant coating layer, and Metabar # 40 is used. This coating liquid was then applied and dried to provide a layer to which particles having a coating layer thickness of 10 μm were not added. The light shielding layer surface and a white film made of biaxially stretched polyethylene terephthalate containing 38 μm of titanium oxide (Lumirror (registered trademark) E20 manufactured by Toray Industries, Inc.) were dry laminated and bonded to obtain a laminate.

(Comparative Example 3)
The light-resistant coating layer is not provided, and the particles contained in the light shielding layer are spherical polystyrene particles (TECHPOLYMER (registered trademark) SBX series, SBX-3, average particle size 3.0 μm, solid content 100%, refractive index 1 .59, manufactured by Sekisui Plastics Co., Ltd.), a laminate was obtained in the same manner as in Example 1.

In any of Examples 1 to 14, a light shielding effect was observed, and in particular, light absorbing carbon black was added to the light shielding layer. The shielding effect was remarkable (Example 4). Furthermore, in the system to which non-spherical particles having the largest refractive index difference from the binder resin in the light shielding layer were added, the luminance was high (Examples 5 and 6).
In the case of a single film without providing a light shielding layer (Comparative Example 1), a system that does not contain particles or additives in the light shielding layer (Comparative Example 2), or a system in which particles added to the light shielding layer are in a spherical shape In (Comparative Example 3), the light shielding effect and the luminance improvement effect were not seen. Moreover, when not providing a light-resistant coating layer, light resistance became inadequate and the fall of the reflectance was caused (Comparative Examples 1-3).

It is an example of the schematic diagram in the light shielding layer of the laminated body for reflection of this invention. It is an example of the schematic diagram observed from the direction parallel to the laminated body surface of the laminated body for reflection of this invention. It is an example of the schematic diagram observed from the direction perpendicular | vertical to the laminated body surface of the laminated body for reflection of this invention.

Explanation of symbols

1: Base film 1
2: Base film 2
3: Light shielding layer 4: Binder resin 5: Particle 6: Projected area (shaded portion) of one particle portion observed from a direction parallel to the laminate surface
7: Projection area (shaded portion) of one particle observed from a direction perpendicular to the laminate surface

Claims (10)

  A laminated body in which a film having a white film and / or a metal layer is laminated on both surfaces of a light shielding layer containing particles, and the particles have an average projected area S of particles observed from a direction parallel to the laminated body surface The reflective laminate contained in the light shielding layer so that the ratio S / L to the average projected area L of the particles observed from the direction perpendicular to the laminate surface is less than 1.0.   The reflective laminate according to claim 1, wherein a difference in refractive index between the particles and the binder resin in the light shielding layer is 0.05 or more.   The laminate for reflection according to claim 1 or 2, wherein the shape of the particle is at least one selected from the group consisting of a star shape, a flat shape, a rhombus shape, and a rectangular shape.   The laminate for reflection according to claim 3, wherein the particles are contained so that a flat surface thereof is parallel to the surface of the laminate.   The reflective laminate according to claim 1 or 2, wherein the particle has a needle shape and / or a confetti shape.   The reflective laminate according to any one of claims 1 to 5, wherein a sum of average reflectances at wavelengths of 400 to 700 nm on both surfaces of the laminate is 140% or more.   The reflective laminate according to any one of claims 1 to 6, wherein the light shielding layer has a thickness of 5 µm or more.   The reflective laminate according to any one of claims 1 to 7, which has a coating layer containing an ultraviolet absorber and / or a light stabilizer on at least one side of the laminate.   A direct-type liquid crystal backlight using the reflective laminate according to claim 1.   The double-sided light source using the reflection laminated body in any one of Claims 1-8.

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