JP4700722B2 - Backlight system and optical sheet with adhesive - Google Patents

Description

  The present invention relates to a configuration of a light source (backlight system) that efficiently emits light and an optical sheet with an adhesive used in the backlight system. By using the backlight system and the pressure-sensitive adhesive optical sheet of the present invention, the optical pressure-sensitive adhesive has low total reflection of light at the interface with the optical member, excellent adhesion and cohesion, and excellent long-term durability. The optical sheet with the pressure-sensitive adhesive provided with a layer can be attached to an adherend that emits light to efficiently emit light, and further contributes to energy saving and long life.

  In optical devices such as TVs, monitors, game consoles, and mobile phones, the light emitted from the surface directly affects the brightness of the screen, and improving the brightness greatly affects the appearance of brightness and contrast. is there. In addition, when the emitted light is used for illumination, naturally, the luminance directly affects the brightness, and those having a high luminance also have an energy-saving advantage such that the current value can be reduced.

  Until now, in order to emit light from such a light source uniformly, the design of the light guide plate and the design and shape of the light emitter itself such as the cold cathode tube and the LED have been devised so that the power can be as low as possible. Have been devised to emit light (for example, see Patent Documents 1 and 2). Furthermore, a device has been devised such that the brightness is uniformly improved on the light guide plate by an optical film such as a diffuser plate or a retroreflective plate that diffuses light.

  However, even in a commercially available monitor or the like, a diffuser plate that makes light emitted from a light guide plate integrated with a light source uniform is only on (mounted on) the light guide plate (for example, Patent Documents). Naturally, since a thin air layer exists between the light guide plate and the diffusion plate, it was confirmed that a loss of light occurred. In order to eliminate this loss, we examined the idea of surface-treating the light guide plate itself to provide a diffusion function and the idea of eliminating the air layer using matching oil between the light guide plate and the diffusion plate. It has been found that it is difficult to respond to product changes such as a large increase in size and size, and in the latter case, problems such as liquid leakage occur due to the heat of the light source.

  In addition, it is known that the light guide plate and the prism sheet are fixed via an adhesive (for example, see Patent Documents 3 to 8), but the adherend (for example, the light guide plate) made of polyester resin or polycarbonate resin is known. When the acrylic pressure-sensitive adhesive is stuck, there is a problem that bubbles are generated at the interface between the adherend and the pressure-sensitive adhesive. This is because the moisture in the resin such as polymethyl methacrylate resin and polycarbonate resin used for the light guide plate volatilizes due to the influence of heat caused by the lighting of the backlight, so foaming at the interface between the adhesive layer and the light guide plate Conceivable.

  No pressure-sensitive adhesive has been known so far to solve this problem. For example, in Patent Documents 3 to 6, a light guide plate and a prism sheet or a lens sheet are bonded with a transparent pressure-sensitive adhesive (double-sided tape is also acceptable). However, there is no detailed description about the pressure-sensitive adhesive, and it is unclear what type of pressure-sensitive adhesive can be used.

  Patent Documents 7 to 8 describe a surface light source device in which a directional light diffusion film is bonded to a light guide plate or a prism sheet via a light diffusion adhesive. A simple manufacturing method is also described. However, there is no description about the problem that bubbles are generated at the interface. Due to the above-mentioned problems, there is no example of attaching an optical film to a light guide plate using an adhesive even if various liquid crystal monitors, liquid crystal TVs, etc. are disassembled. It is. In these patent documents, there is no description of this countermeasure or the like, and it is unclear what kind of adhesive can be used.

JP 2006-179494 A JP-A-11-288614 JP-A-10-301109 JP-A-11-109344 JP 11-110131 A JP-A-11-133419 JP 2005-044744 A JP-A-2005-050654

  Therefore, the present invention is provided with an optical pressure-sensitive adhesive layer that has less total reflection of light at the interface with the optical member, is excellent in adhesiveness and cohesive force, and is excellent in long-term durability in order to cope with the above-described problems. A backlight system that can attach an optical sheet with an adhesive to an adherend that emits light to efficiently emit light, and that also contributes to energy saving and long life, and the backlight system It is an object to provide an optical sheet with an adhesive used in the above. Furthermore, an object of the present invention is to provide an image display device and an illumination device using the backlight system.

  In addition, the present invention is an optical sheet with an adhesive provided with an adhesive layer in which a foaming phenomenon at the interface is not seen even when used for a resin used as an ordinary light guide plate such as polymethyl methacrylate resin or polycarbonate resin. Can be attached to an adherend that emits light, and light can be emitted efficiently, and further, a backlight system that contributes to energy saving and long life, and an adhesive used in the backlight system It aims at providing an optical sheet with an agent. Furthermore, an object of the present invention is to provide an image display device and an illumination device using the backlight system.

  Further, the present invention provides an optical sheet with an adhesive provided with an optical adhesive layer that has less total reflection of light at the interface with the optical member, is excellent in adhesiveness and cohesion, and is excellent in long-term durability. An object of the present invention is to provide a method of manufacturing a backlight system that can be attached to an adherend that emits light and efficiently emits light, and further contributes to energy saving and long life.

  Furthermore, the present invention enables the light to be efficiently emitted by being attached to an adherend that emits light, and further contributes to energy saving and long life. An object of the present invention is to provide a method for improving the brightness of incident light.

  As a result of intensive studies to achieve the above object, the present inventors have found that the above object can be achieved by using the following backlight system and an optical sheet with an adhesive used in the backlight system. The invention has been completed.

  That is, the backlight system of the present invention comprises a pressure-sensitive adhesive polymer having a gel fraction of 35 to 85%, comprising an adherend from which light is emitted and an optical film that has been subjected to an uneven surface treatment so as to increase the surface area. The optical film is a laminate of a plurality of optical films, the refractive index of the adherend is smaller than the refractive index of the adhesive layer, and The refractive index of the pressure-sensitive adhesive layer is smaller than the refractive index of at least one layer of the multi-layer optical film, and the pressure-sensitive adhesive layer is affixed to the opposite surface of the optical film subjected to the uneven processing. And

  In the present invention, the pressure-sensitive adhesive layer 20 is formed by combining an optical film (for example, 10 or 12) subjected to uneven processing such as a microlens and / or a light diffusion plate and an adherend (for example, 30) from which light is emitted. In other words, the present inventors have found a material that exhibits an extremely excellent brightness enhancement effect as described above.

  In addition, the optical film in this invention contains other forms of film shapes, such as an optical tape and an optical sheet.

  The adherend is preferably a light source, a light guide, or a light source unit.

  The optical film is preferably a microlens and / or a light diffusing plate.

  Furthermore, the optical film may be a laminate of a plurality of optical films.

  Moreover, it is preferable that the storage elastic modulus in 23 degreeC of the said adhesive layer is 10,000-1,000,000 Pa.

  Furthermore, it is preferable that the refractive index of the said adhesive layer is 1.50 or more.

  The image display device and the illumination device of the present invention include the above-described backlight system.

  On the other hand, the optical sheet with pressure-sensitive adhesive of the present invention is characterized in that the pressure-sensitive adhesive layer is laminated on the outermost layer of the optical film used in the backlight system described above.

  The pressure-sensitive adhesive layer has 10 to 150 parts by weight of a tackifier having an aromatic ring with respect to 100 parts by weight of a (meth) acrylic polymer obtained by copolymerizing 0.1 to 10% by weight of a hydroxyl group-containing monomer, and It is preferable that it is an adhesive layer which consists of an adhesive composition which mix | blended 0.03-2 weight part of crosslinking agents.

  The (meth) acrylic polymer is a modified (meth) acrylic copolymer obtained by copolymerizing a high-refractive index monomer with a (meth) acrylic polymer obtained by copolymerizing 0.1 to 10% by weight of a hydroxyl group-containing monomer. The polymer is preferably a polymer.

  The (meth) acrylic polymer is a copolymer containing 0.1 to 20% by weight of nitrogen-containing monomer, 0.1 to 5% by weight of carboxyl group-containing monomer, and 0.1 to 10% by weight of hydroxyl group-containing monomer. A modified (meth) acrylic polymer obtained by further copolymerizing a (meth) acrylic polymer with a high refractive index monomer is preferable.

  Furthermore, the pressure-sensitive adhesive composition may further contain 0.01 to 2 parts by weight of a silane coupling agent with respect to 100 parts by weight of the (meth) acrylic polymer.

  The (meth) acrylic polymer is preferably a (meth) acrylic polymer obtained by copolymerizing 50 to 99% by weight of n-butyl acrylate.

  Furthermore, the pressure-sensitive adhesive layer is preferably a pressure-sensitive adhesive layer that contains light-transmitting uncolored particles in a dispersed manner and exhibits light diffusibility.

  Moreover, it is preferable that the thickness of the said adhesive layer is 2-100 micrometers.

  On the other hand, in the method for manufacturing a backlight system of the present invention, the adherend from which the light is emitted and the optical film that has been subjected to the concave and convex processing so as to increase the surface area are bonded via an adhesive layer. Including a process.

  In addition, a method for improving the luminance of emitted light according to the present invention is characterized by using the above-described backlight system.

  As described above, the backlight system of the present invention and the optical sheet with an adhesive used in the backlight system, on the light guide plate, the sealing material, and the light source unit from which light from the light emitter is emitted, are provided with an adhesive. It has been found that the brightness is greatly improved by pasting the opposite surface of the optical film that is processed with unevenness that increases the surface area, such as microlenses and diffusion plates (surface that has not been processed with unevenness). It is. Furthermore, this technology will contribute to energy saving and long life.

  As the pressure-sensitive adhesive composition (pressure-sensitive adhesive layer) used in the present invention, a general acrylic pressure-sensitive adhesive may be used because of its good transparency and weather resistance, but a pressure-sensitive adhesive having a high refractive index. When using, the effect of improving luminance could be exhibited. The reason why the above effects are manifested is not clear, but the refractive index of the optical member is 1.50 to 1.55 for glass, 1.54 for polycarbonate, and 1.50 for triacetyl cellulose. Since there is a large difference of 1.47, a difference in refractive index occurs at the interface between the optical member and the adhesive, and when light enters at a shallow angle, total reflection occurs, which prevents the effective use of light. It is speculated that it can be effectively reduced. The measurement wavelength of the refractive index is 589 nm.

  On the other hand, in the method for manufacturing a backlight system of the present invention, the adherend from which the above-described light is emitted and the optical film that has been subjected to the concave-convex processing so as to increase the surface area are bonded via an adhesive layer. Although it includes a process, it is possible to easily manufacture a backlight system in which the luminance of emitted light is greatly improved.

  Moreover, although the brightness | luminance improvement method of the emitted light of this invention is using the above-mentioned backlight system, it can improve the brightness | luminance of an emitted light significantly easily.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  As shown in FIGS. 1 to 5 as an example, the backlight system 6 of the present invention includes an adherend from which light is emitted (for example, 30), and an optical film that has been subjected to uneven processing so as to increase the surface area ( For example, 10 or 12) is bonded through the pressure-sensitive adhesive layer 20. Further, the lighting device of the present invention can be used as the lighting device as it is due to the configuration shown as an example in FIG.

  Examples of the adherend include a light source, a light guide, and a light source unit. Among them, the light source 32, the light guide 30, and the light source unit 3 are preferable.

  Examples of the light source include a PDP phosphor, an LED phosphor, an organic EL, a cold cathode tube, and a laser light source, and a great effect is observed even if any of them is used. Although it is possible to attach an optical sheet directly to these light sources via an adhesive layer, it is possible to attach these light sources, for example, backlights for liquid crystal televisions and monitors whose surfaces are glass plates or acrylic plates. A glass substrate such as a light guide plate using an LED as a light source or an organic EL light emitter is used. By affixing the optical sheet with the pressure-sensitive adhesive layer of the present invention directly to such a light source, an effect of efficiently emitting light from the light source without confining the light from the inside can be exhibited.

  Normally, when a diffusion plate or the like is provided on the backlight, only the optical sheet is placed on the upper part of the backlight, and a thin air layer having a refractive index of 1.0 exists between the backlight and the optical sheet. However, this loss is reduced by providing an optical sheet through the pressure-sensitive adhesive layer, and the refractive index is higher than the refractive index of the surface of the backlight that is the adherend. By providing the pressure-sensitive adhesive layer, it is presumed that light loss is almost eliminated and light can be emitted efficiently.

  Moreover, as an optical film which performed the uneven | corrugated process so that the above-mentioned surface area may increase, the optical film which has given the uneven | corrugated process which increases a surface area to the opposite surface of an adhesive layer is used. By performing such processing that increases the surface area, it is possible to finally emit light efficiently to the air layer.

  Specific examples of the optical film that has been subjected to the concavo-convex processing so as to increase the surface area include a microlens, a light diffusing plate, a prism sheet, etc. Among them, a microlens and / or a light diffusing plate are particularly preferable. Preferably there is.

  Examples of the microlens include those having a surface that has been subjected to a uniform bullet-like, spherical, or pyramidal processing of 1 to 100 μm. Since such a microlens has a uniform structure, uniform light can be emitted to the air layer.

  In addition, the microlens array used in the present invention is not particularly limited, but, for example, one having an f-number (lens focal length / effective aperture) of 0.5 to 4.0 is preferable, and 0.6 to 3.0. When it exists in the said range, the light of a backlight can be condensed more efficiently.

  The manufacturing method of the microlens is not particularly limited, and a method of performing surface molding by pressing a uniform sheet with a mold or the like, or molding by applying a liquid resin and curing with UV or heat is also possible. It is.

  In addition, by applying a polymer solution in which diffusing particles are dispersed with a dry thickness smaller than the particle size of the fine particles, the fine particles are kneaded and extruded into a diffusion plate with a concavo-convex shape on the surface or a polymer melt. A diffusion plate having a light diffusion function on the surface can also be used.

  As the optical film in the present invention, an optical sheet in which a plurality of optical films of different materials are laminated on the pressure-sensitive adhesive layer surface and the processed surface of the air layer surface unevenness can also be used. For example, it is possible to devise such as providing a function for maintaining strength on the pressure-sensitive adhesive layer surface and a function that allows easy processing on the air surface.

  Specific materials can be used as long as they are transparent. Acrylic resin, polyester resin, epoxy resin, polystyrene resin, polycarbonate resin, urethane resin, styrene-acrylonitrile copolymer, styrene-methyl methacrylate Examples thereof include copolymers.

  In particular, it is preferable that the refractive index of the adherend surface from which light is emitted <the refractive index of the pressure-sensitive adhesive layer <the refractive index of the optical film in order. . For example, a polymethyl methacrylate light guide plate from which light is emitted has a surface refractive index of 1.49, an acrylic adhesive has a refractive index of 1.49 or more, and an optical film has a refractive index of 1.50 or more. Are preferably used.

  Moreover, the said optical film can be set as the thing (optical film) 1 by which the multilayered optical film was laminated | stacked. Here, as a method of laminating the laminated optical film 1, it is possible to simply superimpose, but by using the pressure-sensitive adhesive of the present invention, it is possible to more efficiently guide light to the liquid crystal module.

  As an optical film (optical member), what is used for formation of image display apparatuses, such as a liquid crystal display device, is used, and the kind in particular is not restrict | limited. For example, the optical member includes an optical film such as a polarizing plate. As the polarizing plate, one having a transparent protective film on one side or both sides of a polarizer is generally used.

  The polarizer is not particularly limited, and various types can be used. Examples of polarizers include hydrophilic polymer films such as polyvinyl alcohol films, partially formalized polyvinyl alcohol films, and ethylene / vinyl acetate copolymer partially saponified films, and two colors such as iodine and dichroic dyes. Examples include polyene-based oriented films such as those obtained by adsorbing volatile substances and uniaxially stretched, polyvinyl alcohol dehydrated products, and polyvinyl chloride dehydrochlorinated products. Among these, a polarizer composed of a polyvinyl alcohol film and a dichroic material such as iodine is preferable. The thickness of these polarizers is not particularly limited, but is generally about 5 to 80 μm.

  A polarizer obtained by dyeing a polyvinyl alcohol film with iodine and uniaxially stretching it can be produced, for example, by dyeing polyvinyl alcohol in an aqueous solution of iodine and stretching it 3 to 7 times the original length. If necessary, it can be immersed in an aqueous solution such as potassium iodide which may contain boric acid, zinc sulfate, zinc chloride and the like. Further, if necessary, the polyvinyl alcohol film may be immersed in water and washed before dyeing. In addition to washing the polyvinyl alcohol film surface with dirt and anti-blocking agents by washing the polyvinyl alcohol film with water, it also has the effect of preventing unevenness such as uneven coloring by swelling the polyvinyl alcohol film. is there. Stretching may be performed after dyeing with iodine, may be performed while dyeing, or may be dyed with iodine after stretching. The film can be stretched in an aqueous solution of boric acid or potassium iodide or in a water bath.

  As a material for forming the transparent protective film provided on one side or both sides of the polarizer, a material excellent in transparency, mechanical strength, thermal stability, moisture shielding property, isotropy and the like is preferable. For example, polyester polymers such as polyethylene terephthalate and polyethylene naphthalate, cellulose polymers such as diacetyl cellulose and triacetyl cellulose, acrylic polymers such as polymethyl methacrylate, styrene such as polystyrene and acrylonitrile / styrene copolymer (AS resin) -Based polymer, polycarbonate-based polymer and the like. In addition, polyethylene, polypropylene, polyolefins having a cyclo or norbornene structure, polyolefin polymers such as ethylene / propylene copolymers, vinyl chloride polymers, amide polymers such as nylon and aromatic polyamide, imide polymers, sulfone polymers , Polyether sulfone polymer, polyether ether ketone polymer, polyphenylene sulfide polymer, vinyl alcohol polymer, vinylidene chloride polymer, vinyl butyral polymer, arylate polymer, polyoxymethylene polymer, epoxy polymer, or the above Polymer blends and the like are also examples of polymers that form the transparent protective film. The transparent protective film can also be formed as a cured layer of thermosetting or ultraviolet curable resin such as acrylic, urethane, acrylurethane, epoxy, and silicone.

  Moreover, the polymer film described in JP-A-2001-343529 (WO01 / 37007), for example, (A) a thermoplastic resin having a substituted and / or unsubstituted imide group in the side chain, and (B) a substitution in the side chain And / or a resin composition containing an unsubstituted phenyl and a thermoplastic resin having a nitrile group. A specific example is a film of a resin composition containing an alternating copolymer composed of isobutylene and N-methylmaleimide and an acrylonitrile / styrene copolymer. As the film, a film made of a mixed extruded product of the resin composition or the like can be used.

  Although the thickness of a protective film can be determined suitably, generally it is about 1-500 micrometers from points, such as workability | operativity, such as intensity | strength and handleability, and thin layer property. 1-300 micrometers is especially preferable, and 5-200 micrometers is more preferable.

  Moreover, it is preferable that a protective film has as little color as possible. Therefore, Rth = (nx−nz) · d (where nx is the refractive index in the slow axis direction in the film plane, nz is the refractive index in the film thickness direction, and d is the film thickness). A protective film having a direction retardation value of −90 nm to +75 nm is preferably used. By using a film having a thickness direction retardation value (Rth) of −90 nm to +75 nm, the coloring (optical coloring) of the polarizing plate caused by the protective film can be almost eliminated. The thickness direction retardation value (Rth) is more preferably −80 nm to +60 nm, and particularly preferably −70 nm to +45 nm.

  As the protective film, a cellulose polymer such as triacetyl cellulose is preferable from the viewpoints of polarization characteristics and durability. A triacetyl cellulose film is particularly preferable. In addition, when providing a protective film on both sides of a polarizer, the protective film which consists of the same polymer material may be used by the front and back, and the protective film which consists of a different polymer material etc. may be used. The polarizer and the protective film are usually in close contact with each other through an aqueous adhesive or the like. Examples of the water-based adhesive include an isocyanate-based adhesive, a polyvinyl alcohol-based adhesive, a gelatin-based adhesive, a vinyl-based latex, a water-based polyurethane, and a water-based polyester.

  The surface of the transparent protective film to which the polarizer is not adhered may be subjected to a hard coat layer, an antireflection treatment, an antisticking treatment, or a treatment for diffusion or antiglare.

  Hard coat treatment is applied for the purpose of preventing scratches on the surface of the polarizing plate. For example, a transparent protective film with a cured film excellent in hardness, sliding properties, etc. with an appropriate ultraviolet curable resin such as acrylic or silicone It can be formed by a method of adding to the surface of the film. The antireflection treatment is performed for the purpose of preventing reflection of external light on the surface of the polarizing plate, and can be achieved by forming an antireflection film or the like according to the conventional art. Further, the anti-sticking treatment is performed for the purpose of preventing adhesion with an adjacent layer.

  Anti-glare treatment is applied for the purpose of preventing external light from reflecting on the surface of the polarizing plate and obstructing the visibility of the light transmitted through the polarizing plate. For example, roughening by sandblasting or embossing It can be formed by imparting a fine concavo-convex structure to the surface of the transparent protective film by an appropriate method such as a method or a compounding method of transparent fine particles. The fine particles to be included in the formation of the surface fine concavo-convex structure are, for example, conductive composed of silica, alumina, titania, zirconia, tin oxide, indium oxide, cadmium oxide, antimony oxide or the like having an average particle size of 0.5 to 50 μm. Transparent fine particles such as inorganic fine particles and organic fine particles made of a crosslinked or uncrosslinked polymer may be used. When forming a surface fine uneven structure, the amount of fine particles used is generally about 2 to 50 parts by weight, preferably 5 to 25 parts by weight, based on 100 parts by weight of the transparent resin forming the surface fine uneven structure. The antiglare layer may also serve as a diffusion layer (viewing angle expanding function or the like) for diffusing the light transmitted through the polarizing plate to expand the viewing angle.

  The antireflection layer, antisticking layer, diffusion layer, antiglare layer, and the like can be provided on the transparent protective film itself, or can be provided separately from the transparent protective film as an optical layer.

  The optical film of the present invention includes, for example, a liquid crystal display device such as a reflecting plate, a transflective plate, a retardation plate (including wavelength plates such as 1/2 and 1/4), a viewing angle compensation film, and a brightness enhancement film What becomes an optical layer which may be used for formation of this is mention | raise | lifted. These can be used alone as the optical member of the present invention, and can be laminated on the polarizing plate for practical use and used in one or more layers.

  In particular, a reflective polarizing plate or semi-transmissive polarizing plate in which a polarizing plate is further laminated with a reflecting plate or a semi-transmissive reflecting plate, an elliptical polarizing plate or circular polarizing plate in which a retardation plate is further laminated on a polarizing plate, a polarizing plate A wide viewing angle polarizing plate in which a viewing angle compensation film is further laminated on a plate, or a polarizing plate in which a brightness enhancement film is further laminated on a polarizing plate is preferable.

  A reflective polarizing plate is a polarizing plate provided with a reflective layer, and is used to form a liquid crystal display device or the like that reflects incident light from the viewing side (display side). Thus, there is an advantage that it is easy to reduce the thickness of the liquid crystal display device. The reflective polarizing plate can be formed by an appropriate method such as a method in which a reflective layer made of metal or the like is attached to one surface of the polarizing plate via a transparent protective layer, if necessary.

  Specific examples of the reflective polarizing plate include those in which a reflective layer is formed by attaching a foil or a vapor deposition film made of a reflective metal such as aluminum on one side of a transparent protective film matted as necessary. Moreover, the transparent protective film contains fine particles so as to have a surface fine concavo-convex structure and a reflective layer having a fine concavo-convex structure thereon. The reflective layer having the fine concavo-convex structure has an advantage that incident light is diffused by irregular reflection to prevent directivity and glaring appearance and to suppress unevenness in brightness and darkness. Moreover, the transparent protective film containing fine particles also has an advantage that incident light and its reflected light are diffused when passing through it and light and dark unevenness can be further suppressed. The reflective layer of the fine concavo-convex structure reflecting the surface fine concavo-convex structure of the transparent protective film can be formed by, for example, depositing metal by an appropriate method such as a vapor deposition method such as a vacuum vapor deposition method, an ion plating method, a sputtering method, or a plating method. It can be performed by a method of directly attaching to the surface of the transparent protective layer.

  Instead of the method of directly applying the reflecting plate to the transparent protective film of the polarizing plate, the reflecting plate can be used as a reflecting sheet provided with a reflecting layer on an appropriate film according to the transparent film. Since the reflective layer is usually made of metal, the usage form in which the reflective surface is covered with a transparent protective film, a polarizing plate, etc. prevents the decrease in reflectance due to oxidation, and thus the long-term sustainability of the initial reflectance. In addition, it is more preferable to avoid a separate attachment of the protective layer.

  The transflective polarizing plate can be obtained by using a transflective reflective layer such as a half mirror that reflects and transmits light with the reflective layer. A transflective polarizing plate is usually provided on the back side of a liquid crystal cell, and displays an image by reflecting incident light from the viewing side (display side) when a liquid crystal display device is used in a relatively bright atmosphere. In a relatively dark atmosphere, a liquid crystal display device or the like that displays an image using a built-in light source such as a backlight built in the back side of the transflective polarizing plate can be formed. In other words, the transflective polarizing plate can save the energy of using a light source such as a backlight in a bright atmosphere, and is useful for forming a liquid crystal display device that can be used with a built-in light source in a relatively dark atmosphere. It is.

  An elliptically polarizing plate or a circularly polarizing plate in which a retardation plate is further laminated on a polarizing plate will be described. A phase difference plate or the like is used when changing linearly polarized light to elliptically polarized light or circularly polarized light, changing elliptically polarized light or circularly polarized light to linearly polarized light, or changing the polarization direction of linearly polarized light. In particular, a so-called quarter-wave plate (also referred to as a λ / 4 plate) is used as a retardation plate that changes linearly polarized light into circularly polarized light or changes circularly polarized light into linearly polarized light. A half-wave plate (also referred to as a λ / 2 plate) is usually used when changing the polarization direction of linearly polarized light.

  The elliptically polarizing plate is effectively used for black-and-white display without the above color by compensating (preventing) the coloration (blue or yellow) generated by the birefringence of the liquid crystal layer of the super twist nematic (STN) type liquid crystal display device. It is done. Further, the one in which the three-dimensional refractive index is controlled is preferable because it can compensate (prevent) coloring that occurs when the screen of the liquid crystal display device is viewed from an oblique direction. The circularly polarizing plate is effectively used, for example, when adjusting the color tone of an image of a reflective liquid crystal display device in which the image is displayed in color, and also has an antireflection function.

  Examples of the retardation plate include a birefringent film obtained by uniaxially or biaxially stretching a polymer material, a liquid crystal polymer alignment film, and a liquid crystal polymer alignment layer supported by a film. The thickness of the retardation plate is not particularly limited, but is generally about 20 to 150 μm.

  Examples of the polymer material include polyvinyl alcohol, polyvinyl butyral, polymethyl vinyl ether, polyhydroxyethyl acrylate, hydroxyethyl cellulose, hydroxypropyl cellulose, methyl cellulose, polycarbonate, polyarylate, polysulfone, polyethylene terephthalate, polyethylene naphthalate, polyether sulfone, Polyphenylene sulfide, polyphenylene oxide, polyallylsulfone, polyvinyl alcohol, polyamide, polyimide, polyolefin, polyvinyl chloride, cellulose polymer, norbornene resin, or binary, ternary various copolymers, graft copolymers Examples thereof include polymers and blends. These polymer materials become oriented products (stretched films) by stretching or the like.

  Examples of the liquid crystalline polymer include various main chain types and side chain types in which a conjugated linear atomic group (mesogen) imparting liquid crystal alignment is introduced into the main chain or side chain of the polymer. It is done. Specific examples of main-chain liquid crystalline polymers include nematic-oriented polyester-based liquid crystalline polymers, discotic polymers, and cholesteric polymers that have a structure in which a mesogenic group is bonded to a spacer portion that imparts flexibility. It is done. Specific examples of the side chain type liquid crystalline polymer include polysiloxane, polyacrylate, polymethacrylate, or polymalonate as a main chain skeleton, and a nematic alignment imparting paraffin through a spacer portion composed of a conjugated atomic group as a side chain. Examples thereof include those having a mesogen moiety composed of a substituted cyclic compound unit. These liquid crystalline polymers can be obtained by, for example, applying a solution of a liquid crystalline polymer on an alignment surface such as one obtained by rubbing the surface of a thin film such as polyimide or polyvinyl alcohol formed on a glass plate or one obtained by obliquely depositing silicon oxide. This is done by developing and heat treatment.

  The retardation plate may have an appropriate retardation according to the purpose of use, such as for the purpose of compensating for coloring or viewing angle due to birefringence of various wavelength plates and liquid crystal layers, for example. In this case, the retardation plate may be laminated to control optical characteristics such as retardation.

  The elliptical polarizing plate and the reflective elliptical polarizing plate are obtained by laminating a polarizing plate or a reflective polarizing plate and a retardation plate in an appropriate combination. Such an elliptically polarizing plate can also be formed by sequentially laminating them in the manufacturing process of the liquid crystal display device so as to be a combination of a (reflective) polarizing plate and a retardation plate, as described above. In addition, an optical member such as an elliptically polarizing plate is advantageous in that it is excellent in quality stability, laminating workability and the like, and can improve the manufacturing efficiency of a liquid crystal display device and the like.

  The viewing angle compensation film is a film for widening the viewing angle so that an image can be seen relatively clearly even when the screen of the liquid crystal display device is viewed from a slightly oblique direction rather than perpendicular to the screen. Examples of such a viewing angle compensation phase difference plate include a phase difference plate, an alignment film such as a liquid crystal polymer, and a support in which an alignment layer such as a liquid crystal polymer is supported on a transparent substrate. A normal retardation plate uses a birefringent polymer film uniaxially stretched in the plane direction, whereas a retardation plate used as a viewing angle compensation film stretches biaxially in the plane direction. Birefringent polymer film, biaxially stretched film such as polymer with birefringence with a controlled refractive index in the thickness direction that is uniaxially stretched in the plane direction and stretched in the thickness direction, etc. Used. Examples of the tilted alignment film include a film obtained by bonding a heat shrink film to a polymer film and stretching or / and shrinking the polymer film under the action of the contraction force by heating, or a film obtained by obliquely aligning a liquid crystal polymer. Can be given. The raw material polymer for the phase difference plate is the same as the polymer described in the previous phase difference plate, preventing coloration due to a change in the viewing angle based on the phase difference by the liquid crystal cell and expanding the viewing angle for good visual recognition. An appropriate one for the purpose can be used.

  In addition, from the viewpoint of achieving a wide viewing angle with good visibility, an optical compensation position in which an alignment layer of a liquid crystal polymer, particularly an optically anisotropic layer composed of a tilted alignment layer of a discotic liquid crystal polymer, is supported by a triacetyl cellulose film. A phase difference plate can be preferably used.

  A polarizing plate obtained by bonding a polarizing plate and a brightness enhancement film is usually provided on the back side of a liquid crystal cell. The brightness enhancement film reflects a linearly polarized light with a predetermined polarization axis or a circularly polarized light in a predetermined direction when natural light is incident due to a backlight such as a liquid crystal display device or reflection from the back side, and transmits other light. In addition, a polarizing plate in which a brightness enhancement film is laminated with a polarizing plate allows light from a light source such as a backlight to enter to obtain transmitted light in a predetermined polarization state, and reflects light without transmitting the light other than the predetermined polarization state. The The light reflected on the surface of the brightness enhancement film is further inverted through a reflective layer provided on the rear side thereof, and re-incident on the brightness enhancement film, and part or all of the light is transmitted as light in a predetermined polarization state. The brightness can be improved by increasing the amount of light transmitted through the improvement film and increasing the amount of light that can be used for liquid crystal display image display by supplying polarized light that is difficult to absorb into the polarizer. is there. That is, when light is incident through the polarizer from the back side of the liquid crystal cell without using a brightness enhancement film, light having a polarization direction that does not coincide with the polarization axis of the polarizer is almost polarized. It is absorbed by the polarizer and does not pass through the polarizer. That is, although depending on the characteristics of the polarizer used, approximately 50% of the light is absorbed by the polarizer, and accordingly, the amount of light that can be used for liquid crystal image display is reduced, resulting in a dark image. In the brightness enhancement film, light having a polarization direction that is absorbed by the polarizer is reflected once by the brightness enhancement film without being incident on the polarizer, and further inverted through a reflective layer provided on the rear side thereof. Repeatedly re-enter the brightness enhancement film, and the brightness enhancement film transmits only polarized light whose polarization direction is such that the polarization direction of light reflected and inverted between the two can pass through the polarizer. Therefore, light such as a backlight can be efficiently used for displaying an image on the liquid crystal display device, and the screen can be brightened.

  A diffusion plate (light diffusion sheet) can also be provided between the brightness enhancement film and the reflective layer. The polarized light reflected by the brightness enhancement film is directed to the reflective layer or the like, but the installed diffuser plate uniformly diffuses the light passing therethrough and simultaneously cancels the polarized state and becomes a non-polarized state. That is, the diffuser plate returns the polarized light to the original natural light state. The light in the non-polarized state, that is, the natural light state is directed to the reflection layer and the like, reflected through the reflection layer and the like, and again passes through the diffusion plate and reenters the brightness enhancement film. Thus, while maintaining the brightness of the display screen by providing a diffuser plate that returns polarized light to the original natural light state between the brightness enhancement film and the reflective layer, etc., at the same time, the unevenness of the brightness of the display screen is reduced, A uniform and bright screen can be provided. By providing such a diffuser plate, it is considered that the first incident light has a moderate increase in the number of repetitions of reflection, and in combination with the diffusion function of the diffuser plate, a uniform bright display screen can be provided.

  As the brightness enhancement film, for example, a dielectric multilayer thin film or a multilayer laminate of thin film films having different refractive index anisotropy, such as a characteristic that transmits linearly polarized light having a predetermined polarization axis and reflects other light. Such as a cholesteric liquid crystal polymer alignment film or a film substrate whose alignment liquid crystal layer is supported on a film substrate, which reflects either left-handed or right-handed circularly polarized light and transmits other light. Appropriate ones such as those shown can be used.

  Therefore, in the brightness enhancement film of the type that transmits linearly polarized light having the predetermined polarization axis as described above, the transmitted light is directly incident on the polarizing plate with the polarization axis aligned, thereby efficiently transmitting while suppressing absorption loss due to the polarizing plate. Can be made. On the other hand, in a brightness enhancement film of a type that emits circularly polarized light such as a cholesteric liquid crystal layer, it can be directly incident on a polarizer, but the circularly polarized light is linearly polarized via a retardation plate in order to suppress absorption loss. It is preferable to make it enter into a polarizing plate. Note that circularly polarized light can be converted to linearly polarized light by using a quarter wave plate as the retardation plate.

  A retardation plate that functions as a quarter-wave plate in a wide wavelength range such as a visible light region has, for example, a retardation layer that functions as a quarter-wave plate for light-color light with a wavelength of 550 nm and other retardation characteristics. The phase difference layer shown, for example, the phase difference layer which functions as a half-wave plate, etc. can be obtained by the method of superimposing. Therefore, the retardation plate disposed between the polarizing plate and the brightness enhancement film may be composed of one or more retardation layers.

  In addition, a cholesteric liquid crystal layer that has a reflection wavelength different from each other and has an arrangement structure in which two layers or three or more layers are overlapped to obtain a layer that reflects circularly polarized light in a wide wavelength range such as a visible light region. Based on this, transmitted circularly polarized light in a wide wavelength range can be obtained.

  Moreover, the polarizing plate may consist of what laminated | stacked the polarizing plate and the optical layer of 2 layers or 3 layers or more like the above-mentioned polarization separation type polarizing plate. Therefore, a reflective elliptical polarizing plate or a semi-transmissive elliptical polarizing plate in which the above-mentioned reflective polarizing plate or semi-transmissive polarizing plate and a retardation plate are combined may be used.

  An optical film in which the optical layer is laminated on a polarizing plate can be formed by a method of sequentially laminating separately in the manufacturing process of a liquid crystal display device or the like. There is an advantage that the manufacturing process of the liquid crystal display device and the like can be improved because of excellent stability and assembly work. For the lamination, an appropriate adhesive means such as a pressure-sensitive adhesive layer can be used. When adhering the polarizing plate and the other optical layer, their optical axes can be set at an appropriate arrangement angle in accordance with the target phase difference characteristic.

  In addition, in each layer such as an optical film and an adhesive layer of the optical film with an adhesive of the present invention, for example, a salicylic acid ester compound, a benzophenol compound, a benzotriazole compound, a cyanoacrylate compound, a nickel complex compound, etc. It may be one having a UV absorbing ability by a method such as a method of treating with a UV absorber.

  The optical film (optical film with an adhesive) of the present invention can be preferably used for forming various image display devices such as a liquid crystal display device. The liquid crystal display device can be formed according to the conventional method. That is, a liquid crystal display device is generally formed by assembling components such as a liquid crystal module 50 such as a liquid crystal cell, an optical member with an adhesive, and an illumination system as necessary, and incorporating a drive circuit. In the present invention, there is no particular limitation except that the optical film according to the present invention is used. As the liquid crystal cell, for example, an arbitrary type such as a TN type, an STN type, or a π type can be used.

  An appropriate liquid crystal display device such as a liquid crystal display device in which an optical film with an adhesive is disposed on one side or both sides of a liquid crystal cell, or a backlight or a reflector used in an illumination system can be formed. In that case, the optical member by this invention can be installed in the one side of a liquid crystal cell. Further, when forming a liquid crystal display device, for example, a single layer of appropriate parts such as a diffuser plate, an antiglare layer, an antireflection film, a protective plate, a prism array, a lens array sheet, a light diffuser plate, and a backlight at an appropriate position. Alternatively, two or more layers can be arranged.

  In order to improve the anchoring force when such an optical film is bonded to the pressure-sensitive adhesive layer, the surface of the optical film may be subjected to easy attachment treatment such as corona treatment or plasma treatment, or undercoating treatment.

  Further, the image display device and the illumination device of the present invention are liquid crystal display devices using the above-described backlight system, which can emit light efficiently, and further contribute to energy saving and long life. Become.

  On the other hand, the backlight system 6 of the present invention has an adherend (for example, 30) from which light is emitted via an adhesive layer 20 as shown in FIGS. The optical film (for example, 10 and 12) which gave the processing process is joined. The pressure-sensitive adhesive layer 20 may be a single layer, or two or more layers may be laminated and used.

  Although it does not specifically limit as an adhesive which forms the adhesive layer 20, An acrylic adhesive and a rubber-type adhesive can be especially used without a restriction | limiting.

  Examples of rubber-based adhesives include natural rubber, a copolymer of natural rubber and an acrylic component such as methyl methacrylate, a styrene block copolymer and a hydrogenated product thereof, and a styrene-butadiene-styrene block copolymer and Examples thereof include hydrogenated products. Among these, a copolymer of natural rubber and an acrylic component such as methyl methacrylate is preferable. These may be used singly or in combination of two or more.

  As the acrylic pressure-sensitive adhesive, for example, a (meth) acrylic polymer obtained by copolymerizing 0.1 to 10% by weight of a hydroxyl group-containing monomer is particularly preferable.

  Specific examples of the hydroxyl group-containing monomer include 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, and 6-hydroxyhexyl (meth) acrylate. In particular, a pressure-sensitive adhesive composition (and a pressure-sensitive adhesive layer) using a (meth) acrylic polymer as a base polymer in which a hydroxyl group-containing monomer having 4 or more carbon atoms in the side chain is used is also preferable from the viewpoint of heat resistance. Used.

  When the hydroxyl group-containing monomer is used, it is copolymerized in an amount of 0.1 to 10% by weight, preferably 0.3 to 7% by weight. If the content of the hydroxyl group-containing monomer is too small, the long-term durability may be lowered. If the content is too large, the durability may be deteriorated.

  As the acrylic pressure-sensitive adhesive, an acrylic monomer having an alkyl group to be copolymerized is used, and ethyl (meth) acrylate, propyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, Pentyl (meth) acrylate, isoamyl (meth) acrylate, hexyl (meth) acrylate, heptyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isooctyl (meth) acrylate, isononyl (meth) acrylate, isomyristyl (Meth) acrylate and the like. These may be used singly or in combination of two or more. In particular, n-butyl (meth) acrylate is preferably used in consideration of the compatibility with the tackifier added to the base polymer, and in this case, 50 to 99% by weight is used in the acrylic copolymer. It is preferably 6 to 99% by weight.

  Furthermore, another copolymerizable monomer (monomer component) may be appropriately copolymerized with the (meth) acrylic polymer. Examples of the copolymerizable monomer include methyl (meth) acrylate, vinyl acetate, acrylamide, dimethylaminomethylacrylamide, acryloylmorpholine, glycidyl acrylate, styrene derivatives such as styrene and α-methylstyrene, vinyl toluene and α- Examples thereof include high refractive index monomers such as vinyltoluene derivatives, benzyl (meth) acrylate, naphthyl (meth) acrylate, phenoxyethyl (meth) acrylate, phenoxybutyl (meth) acrylate, and the like.

  In particular, a monomer component having a carboxyl group (carboxyl group-containing monomer) is also used in order to improve adhesiveness, increase cohesion, or efficiently crosslink to increase heat resistance.

  Examples of the carboxyl group-containing monomer include acrylic acid, methacrylic acid, itaconic acid, maleic acid and the like, and acrylic acid and methacrylic acid are particularly preferably used. These may be used singly or in combination of two or more.

  When the carboxyl group-containing monomer is used, it is copolymerized in an amount of 0.1 to 5% by weight, preferably 0.2 to 3% by weight. If the amount of the carboxyl group-containing monomer is too small, the adhesiveness is inferior, and if it is too large, the compatibility with the tackifier is greatly reduced and the pressure-sensitive adhesive becomes cloudy.

The (meth) acrylic polymer contains 0.1 to 20% by weight of a nitrogen-containing monomer,
It is preferably a (meth) acrylic polymer obtained by copolymerizing 0.1 to 5% by weight of a carboxyl group-containing monomer and 0.1 to 10% by weight of a hydroxyl group-containing monomer, and more preferably the (meth) acrylic polymer. Those whose gel fraction is preferably adjusted to 30 to 85% by weight are more preferably used. Thus, when a functional group containing a nitrogen atom and a carboxyl group coexist in the pressure-sensitive adhesive polymer ((meth) acrylic polymer), the internal cohesive force is further improved by the interaction, and polymethyl methacrylate resin or polycarbonate resin. Even if it is provided to a resin used as a normal light guide plate such as the above, the effect that the foaming phenomenon at the interface is not seen becomes more remarkable.

  Examples of the nitrogen-containing monomer include monomers having an amino group, an imide group or an amide group, such as (meth) acrylamide, N, N-dimethyl (meth) acrylamide, N, N-diethylacrylamide, and N-methylol. (Meth) acrylamide, N-methoxymethyl (meth) acrylamide, N-butoxymethyl (meth) acrylamide, dimethylaminoethyl (meth) acrylate, t-butylaminoethyl (meth) acrylate, (meth) acrylonitrile, N- (Meth) acryloylmorpholine, N-vinyl-2-pyrrolidone, N-cyclohexylmaleimide, N-phenylmaleimide, N-methylmaleimide, N-ethylmaleimide, N-propylmaleimide, N-butylmaleimide, N-to Kisil Malemi And the like. These may be used singly or in combination of two or more.

  When using the said nitrogen-containing monomer, 0.1 to 20 weight% is preferable, More preferably, 0.1 to 10 weight% is copolymerized. When the amount of the nitrogen-containing monomer is too small, the internal cohesive force cannot be sufficiently improved, and when the amount is too large, the adhesiveness may be lowered, which is not preferable.

  The (meth) acrylic polymer has a weight average molecular weight of usually 600,000 or more, preferably 700,000 to 3,000,000. If the weight average molecular weight is too small, the durability is poor, and if it is too large, the workability deteriorates, which is not preferable.

  The production of the (meth) acrylic polymer may employ any known production method such as solution polymerization, bulk polymerization, and emulsion polymerization.

  For example, in solution polymerization, it is preferable to use 0.01 to 0.2 parts by weight of a polymerization initiator such as azobisisobutyronitrile (AIBN) with respect to 100 parts by weight of the (meth) acrylic polymer, More preferably, 0.05 to 0.15 parts by weight are used. It can be obtained by reacting at 50 to 70 ° C. for 8 to 30 hours under a nitrogen stream using a polymerization solvent such as ethyl acetate.

  The acrylic copolymer thus obtained can be modified for the purpose of adjusting the refractive index, increasing the internal cohesive force, and increasing the heat resistance.

  For example, as the modification treatment, in the presence of 100 parts by weight of the obtained (meth) acrylic polymer, a monomer (monomer component) having a composition different from that of the (meth) acrylic polymer is preferably 10 to 200 parts by weight, preferably In addition to 10 to 100 parts by weight, the medium is adjusted as required, and the graft polymerization reaction is carried out using 0.02 to 5 parts by weight of peroxide, preferably 0.04 to 2 parts by weight.

  Here, the monomer having a different composition is not particularly limited, and (meth) acrylic monomers such as benzyl (meth) acrylate, phenoxy (meth) acrylate, naphthyl (meth) acrylate, and isobornyl (meth) acrylate, Examples thereof include high refractive index monomers such as styrene derivatives such as styrene and α-methylstyrene, and derivatives such as vinyltoluene and α-vinyltoluene. By using the high refractive index monomer, the refractive index of the acrylic pressure-sensitive adhesive can be increased.

  As a polymerization method, in the case of solution polymerization, a necessary monomer and a solvent whose viscosity is adjusted are added to a solution of a (meth) acrylic polymer, and after nitrogen substitution, 0.02 to 5 weight of peroxide. Part, preferably 0.04 to 2 parts by weight, and heated at 50 to 80 ° C. for 4 to 15 hours to carry out the graft polymerization reaction.

  For emulsion polymerization, add water to adjust the amount of solids to the aqueous dispersion of (meth) acrylic polymer, add the necessary monomers, and replace with nitrogen with stirring. After the monomer is absorbed into the polymer particles, a water-soluble peroxide aqueous solution is added, and the reaction is terminated by heating at 50 to 80 ° C. for 4 to 15 hours.

  Thus, by polymerizing the monomer in the presence of the (meth) acrylic polymer, a homopolymer of this monomer is also produced, but the graft polymerization to the (meth) acrylic polymer also occurs, A polymer composed of another homopolymer is uniformly present in the acrylic copolymer. In this case, if the amount of peroxide used as an initiator is small, it takes too much time for the graft polymerization reaction, and if it is too large, a large amount of monomer homopolymer is generated.

  In the said adhesive composition (adhesive layer), tackifiers, such as a tackifier, can be used suitably.

  Although it does not specifically limit as said tackifier, A non-colored and transparent thing is preferable. As the tackifier, for example, a tackifier having an aromatic ring and having a refractive index in the range of 1.51 to 1.75 is preferably used. Moreover, it is preferable that the weight average molecular weights of a tackifier are 1000-3000, and it is preferable that a softening point is 90 degrees C or less. If the weight average molecular weight exceeds 3000 or the softening point exceeds 90 ° C., the compatibility with the acrylic polymer may be reduced, and if the weight average molecular weight is less than 1000, the cohesive force of the adhesive is reduced. There is a case.

  As a measure of the transparency, a Gardner hue of 1 or less in a 50% by weight toluene solution is used. Specifically, styrene oligomer, phenoxyethyl acrylate oligomer, copolymer of styrene and α-methylstyrene, copolymer of vinyltoluene and α-methylstyrene, hydrogenated product of C9 petroleum resin, terpene phenol Examples thereof include hydrogenated products, hydrogenated products of rosin and derivatives thereof. At this time, the tackifier having a softening point of 40 ° C. or lower is used in an amount of less than 30 parts by weight, and is used in combination with a tackifier having a softening point of 50 ° C. or higher in excess of 20 parts by weight (total 50 parts by weight). Is preferable in terms of heat resistance.

  The amount of these tackifiers used is 10 to 150 parts by weight, preferably 20 to 100 parts by weight, with respect to 100 parts by weight of the (meth) acrylic polymer solid content, and is adjusted to a predetermined refractive index. If the amount is too small, the refractive index will not increase sufficiently, and if it is too large, it will become hard and the adhesiveness will deteriorate, which is not preferable.

  In the said adhesive composition (adhesive layer), a crosslinking agent can be used suitably. In particular, when a (meth) acrylic polymer is used as the base polymer, it is preferable because the cohesive force and durability are improved by crosslinking.

  Examples of the crosslinking agent include an isocyanate crosslinking agent, an epoxy crosslinking agent, an oxazoline crosslinking agent, and a peroxide.

  Diisocyanates such as tolylene diisocyanate, diphenylmethane diisocyanate, xylylene diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate, diisocyanate adducts modified with various polyols, isocyanurate rings, burettes, and allophanates And a polyisocyanate compound in which is formed. In particular, aliphatic and alicyclic isocyanates are preferably used because the cross-linked product becomes transparent.

  Although the amount of the crosslinking agent varies depending on the material used, it is usually in the range of 0.03 to 2 parts by weight, preferably 0.05 to 1 part by weight per 100 parts by weight of the (meth) acrylic polymer. Used in. If the amount of the crosslinking agent is too small, the cohesive force is insufficient, and if it is too large, the adhesiveness is lowered, which is not preferable.

  In addition, in an aqueous dispersion of a modified (meth) acrylic polymer produced by emulsion polymerization, an isocyanate crosslinking agent is often not used, but when used, the isocyanate group easily reacts with water. An isocyanate-based cross-linking agent may be used.

  As the peroxide, any peroxide can be used as long as it generates radicals by heating to advance the crosslinking of the base polymer of the pressure-sensitive adhesive composition. Use a peroxide of 80 ° C. to 160 ° C., preferably 90 ° C. to 140 ° C. If the half-life temperature for 1 minute is too low, a reaction may occur during storage before coating and drying to increase the viscosity and the coating may become impossible. If it is too high, the temperature during the crosslinking reaction will increase and a side reaction will occur, resulting in peroxidation. The product may remain and cross-linking with time may proceed, which is not preferable.

  Examples of the peroxide used in the present invention include di (2-ethylhexyl) peroxydicarbonate (1 minute half-life temperature: 90.6 ° C.), di (4-t-butylcyclohexyl) peroxydicarbonate ( 1 minute half-life temperature: 92.1 ° C.), di-sec-butyl peroxydicarbonate (1 minute half-life temperature: 92.4 ° C.), t-butyl peroxyneodecanoate (1 minute half-life temperature: 103.5 ° C.), t-hexyl peroxypivalate (half-life temperature for 1 minute: 109.1 ° C.), t-butyl peroxypivalate (half-life temperature for 1 minute: 110.3 ° C.), dilauroyl peroxide (1 minute half-life temperature: 116.4 ° C.), di-n-octanoyl peroxide (1 minute half-life temperature: 117.4 ° C.), 1,1,3,3-tetramethylbutyl Oxy-2-ethylhexanoate (1 minute half-life temperature: 124.3 ° C), di (4-methylbenzoyl) peroxide (1 minute half-life temperature: 128.2 ° C), dibenzoyl peroxide (half-minute for 1 minute) Period temperature: 130.0 ° C.), t-butyl peroxyisobutyrate (1 minute half-life temperature: 136.1 ° C.), 1,1-di (t-hexylperoxy) cyclohexane (1 minute half-life temperature: 149.2 ° C.). Especially, since the crosslinking reaction efficiency is excellent, di (4-t-butylcyclohexyl) peroxydicarbonate (1 minute half-life temperature: 92.1 ° C.), dilauroyl peroxide (1 minute half-life temperature: 116. 4 ° C), dibenzoyl peroxide (1 minute half-life temperature: 130.0 ° C) and the like are preferably used.

  The peroxide half-life is an index representing the decomposition rate of the peroxide, and means the time until the remaining amount of peroxide is reduced to half. The decomposition temperature for obtaining a half-life at an arbitrary time and the half-life time at an arbitrary temperature are described in the manufacturer catalog, for example, “Organic peroxide catalog 9th edition by Nippon Oil & Fats Co., Ltd.” (May 2003) ".

  The peroxide may be used alone, or two or more kinds may be mixed and used, but the total content is 0.1% of the peroxide with respect to 100 parts by weight of the base polymer. It is preferable to contain 03-2 weight part, It is more preferable to contain 0.04-1.5 weight part, It is more preferable to contain 0.05-1 weight part. If the amount is less than 0.03 parts by weight, the cohesive force may be insufficient. On the other hand, if the amount exceeds 2 parts by weight, the crosslinking may be excessively formed and the adhesiveness may be poor.

  In addition, when an aromatic isocyanate compound is used in order to use the above peroxide, the adhesive after curing may be colored, so in applications where transparency is required, aliphatic And alicyclic isocyanates are preferably used.

  The amount of such a crosslinking agent varies depending on the material used, but is usually 0.03 to 2 parts by weight, preferably 0.05 to 1 part by weight, based on 100 parts by weight of the (meth) acrylic polymer. Used in the range of If the amount is too small, the cohesive force is insufficient.

  The pressure-sensitive adhesive composition obtained by blending the above (meth) acrylic polymer with the above-mentioned crosslinking agent is coated and dried on a support, and the gel fraction of the pressure-sensitive adhesive after crosslinking is 35 to 85% by weight, preferably 40 to 40%. The crosslinking treatment is performed so that the amount becomes 80% by weight, more preferably 45 to 70% by weight. If the gel fraction is too small, the cohesive force is inferior, and if it is too large, the adhesiveness is inferior, which is not preferable. Even if this occurs, the foaming phenomenon at the adhesive interface between the acrylic plate and the pressure-sensitive adhesive can be suppressed. The gel fraction of the pressure-sensitive adhesive polymer ((meth) acrylic polymer) here means that when a tackifier that is not incorporated into the crosslinked structure is used, the tackifier is dissolved in the solvent together with the uncrosslinked polymer. Thus, it shows the amount of crosslinked polymer relative to the initial adhesive polymer, with the amount of tackifier corrected. Moreover, although a gel fraction may increase by heat storage etc., the increase of a gel fraction is set so that it may become a maximum of 95 weight% on the basis of 10 weight%.

  In order to obtain the gel fraction, it is natural to adjust the amount of the crosslinking agent. However, when a peroxide is used, the crosslinking treatment temperature and time are also important. As a guideline, it is possible to set the crosslinking treatment temperature and time so that is 50% by weight or more, preferably 70% by weight or more. If the amount of peroxide decomposition is small, the amount of remaining peroxide increases and a crosslinking reaction over time occurs, which is not preferable.

  Specifically, for example, when the crosslinking treatment temperature is 1 minute half-life temperature, the decomposition amount is 50% by weight in 1 minute and 75% by weight in 2 minutes, and it is necessary to heat treatment for 1 minute or more. If the half-life time of the peroxide at the temperature is 30 seconds, a crosslinking treatment of 30 seconds or more is required. If the peroxide half-life time at the crosslinking treatment temperature is 5 minutes, the crosslinking time of 5 minutes or more is required. Processing is required.

  As described above, the crosslinking treatment temperature and time are adjusted and adjusted proportionally from the half-life time assuming that the peroxide is linearly proportional to the peroxide used. It is necessary to process. As this temperature, the temperature at the time of drying may be used as it is, or it may be processed after drying.

  The crosslinking treatment time is set in consideration of productivity and workability, but 0.2 to 20 minutes, preferably 0.5 to 10 minutes is used.

  When using an aromatic isocyanate compound when using a peroxide, the cured adhesive may be colored, and in applications where transparency is required, aliphatic and alicyclic Isocyanates are preferably used.

  The pressure-sensitive adhesive layer used in the present invention preferably has a storage elastic modulus at 23 ° C. in the range of 10,000 to 1,000,000 Pa, more preferably 30,000 to 500,000 Pa. Preferably, an adhesive having a viscosity of 40,000 to 400,000 Pa is used. If the storage elastic modulus is too small, peeling or the like after sticking tends to occur, and if it is too large, the adhesiveness is inferior.

  Further, as the pressure-sensitive adhesive composition (pressure-sensitive adhesive layer), it is preferable to use a light-transmitting pressure-sensitive adhesive composition (pressure-sensitive adhesive layer) that contains light-transmitting non-colored particles in a dispersed manner and exhibits light diffusibility.

  As the light-transmitting non-colored particles dispersed and contained in the diffusion pressure-sensitive adhesive composition (diffusion pressure-sensitive adhesive layer), appropriate colorless and transparent particles can be used. As light-transmitting non-colored particles, for example, inorganic particles that may be conductive such as silica, alumina, titania, zirconia, tin oxide, indium oxide, cadmium oxide, antimony oxide, various crosslinked or uncrosslinked polymers, etc. Organic particles made of

  In the above, it is preferable to form as a diffusion adhesive layer having a light diffusivity of 10% or less due to the inclusion of non-colored particles. When the light diffusivity exceeds 10%, the degree of light diffusion becomes excessive, and the brightness in the front (vertical) direction when the reflective liquid crystal display device is viewed under illumination is poor. The light diffusivity is more preferably 1 to 9%, 1.5 to 8%, and particularly 2 to 7% in terms of the balance between the wide viewing angle due to light diffusibility and the brightness in the front direction. .

The light diffusivity is the vertical transmission direction I ₀ of the vertical incident light H when the vertical light H is incident on the diffusion adhesive layer 1 as illustrated in FIG. 1 of JP-A-2000-347006. _{I 10} the intensity of the transmitted light in the direction inclined 10 degrees with respect to the intensity of the transmitted light in the _{I 0} to 30 degrees inclined direction when the _{I 30,} at _{100 × I 30 / I 10 (} %) Defined.

The non-colored particles that can be preferably used in view of the achievement of the light diffusivity and the controllability of the adhesive force are those having an average particle diameter of 1 to 10 μm, preferably 9 μm or less, particularly 2 to 8 μm. In addition, when the refractive index of the non-colored particles is n ¹ and the refractive index of the adhesive layer is n ^{2 in} terms of suppressing backscattering and providing good diffusibility in the transmission direction, the formula: 0.01 <| n A combination satisfying ¹⁻ n ² | <0.1, preferably | n ¹ −n ² | <0.09, particularly −0.08 <n ¹ −n ² <−0.01 is preferable.

  The amount of the light-transmitting non-colored particles to be dispersed and contained in the diffusion adhesive layer is appropriately determined based on the above-described light diffusivity and the like. 5 to 200 parts by weight, preferably 10 to 150 parts by weight, more preferably 15 to 100 parts by weight of non-colored particles are used per 100 parts by weight of the product (solid content).

  As described above, the pressure-sensitive adhesive itself can be obtained by dispersing fine particles in the pressure-sensitive adhesive composition (pressure-sensitive adhesive layer) or by developing haze due to domain formation by the polymer of the added monomer when the modified acrylic copolymer is modified. In addition, a design with a diffusion function is also possible, and a light dispersion effect can be brought about.

  Further, when the pressure-sensitive adhesive composition comprising this (meth) acrylic polymer is applied to a hydrophilic adherend such as glass, a silane coupling agent is added in an amount of 0.01 to 0.01 in order to increase the water resistance at the interface. 1 part by weight is blended.

  Examples of the silane coupling agent include 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, and 2- (3,4-epoxycyclohexyl). Epoxy group-containing silane coupling agents such as ethyltrimethoxysilane, 3-aminopropyltrimethoxysilane, N-2- (aminoethyl) -3-aminopropylmethyldimethoxysilane, 3-triethoxysilyl-N- (1, (3-dimethylbutylidene) propylamine, amino group-containing silane coupling agents such as N-phenyl-3-aminopropyltrimethoxysilane, 3-acryloxypropyltrimethoxysilane, 3-methacryloxypropyltriethoxysilane ( (Meth) acrylic group-containing Silane coupling agents, such as Inshianeto group-containing silane coupling agents such as 3-isocyanate propyl triethoxysilane and the like. Use of such a silane coupling agent is preferable for improving durability.

  The silane coupling agent may be used alone or in combination of two or more, but the total content is 100 parts by weight of the (meth) acrylic polymer. It is preferable to contain 0.01-2 weight part of silane coupling agents, and it is more preferable to contain 0.02-1 weight part. If it is less than 0.01 parts by weight, the durability improving effect may be inferior. On the other hand, if it exceeds 2 parts by weight, the adhesive force to an optical member such as a liquid crystal cell may be excessively increased and the removability may be inferior. is there.

  The pressure-sensitive adhesive composition may contain other known additives, for example, powders such as vulcanizing agents, tackifiers, colorants, pigments, dyes, surfactants, plasticizers, Use surface lubricants, leveling agents, softeners, antioxidants, anti-aging agents, light stabilizers, UV absorbers, polymerization inhibitors, inorganic or organic fillers, metal powders, particles, foils, etc. It can be added appropriately depending on the application. Moreover, you may employ | adopt the redox system which added a reducing agent within the controllable range.

  The pressure-sensitive adhesive composition uses an optical sheet (optical film) as a support, and is coated, dried and crosslinked on the support to obtain an optical sheet with a pressure-sensitive adhesive layer. It is also usually carried out by applying and drying on a peeled support and transferring it to various optical sheets. When coated and dried on an embossed release support and transferred to an optical sheet, the surface of the pressure-sensitive adhesive layer can be made uneven, and there is also an advantage that bubbles can be easily removed when affixed to an adherend to which light is emitted. .

  As the above-mentioned coating method, it is processed by any coating method such as reverse coater, comma coater, lip coater, die coater, etc., so that the pressure-sensitive adhesive thickness after drying is usually 2 to 500 μm, preferably 5 to 100 μm. The

  Moreover, the optical sheet with pressure-sensitive adhesive of the present invention is such that the pressure-sensitive adhesive layer having the above-described configuration in the backlight system is formed on one side of the optical film. Since the optical sheet with pressure-sensitive adhesive of the present invention includes a pressure-sensitive adhesive layer that exhibits the above-described effects, the effect of being able to emit light efficiently without confining light from the light source can be exhibited.

  Such an optical sheet with an adhesive layer of the present invention is used by being attached to an adherend to which light is irradiated from below. The refractive index of the pressure-sensitive adhesive layer is higher than the refractive index of the surface of the adherend from which light is emitted, and the refractive index of the optical sheet is higher than the refractive index of the pressure-sensitive adhesive layer. Since there is no reflection, there is no loss of emitted light, and light can be emitted efficiently. The present invention has also found such an efficient light emission method.

  On the other hand, even when there are fine irregularities on the surface of such a light source and light is lost, the light can be efficiently emitted by attaching the optical sheet with the pressure-sensitive adhesive layer of the present invention. This is considered to be due to the fact that the pressure-sensitive adhesive is soft, so that the pressure-sensitive adhesive enters such a concavo-convex portion, eliminates the air layer from being engulfed by the unevenness, and has a high refractive index.

  Furthermore, an effect that suppresses variation in light emission luminance seen in the FED method or the like can be expected.

  On the other hand, in the method for manufacturing a backlight system of the present invention, the adherend from which the above-described light is emitted and the optical film that has been subjected to the concave-convex processing so as to increase the surface area are bonded via an adhesive layer. Although it includes a process, it is possible to easily manufacture a backlight system in which the luminance of emitted light is greatly improved.

  Moreover, although the brightness | luminance improvement method of the emitted light of this invention is using the above-mentioned backlight system, it can improve the brightness | luminance of an emitted light significantly easily.

  Examples and the like specifically showing the configuration and effects of the present invention will be described below. The evaluation items in the examples and the like were performed as follows.

[Example 1]
In a reaction vessel equipped with a cooling pipe, a nitrogen introduction pipe, a thermometer, and a stirrer, 233 parts by weight of ethyl acetate as a solvent, 98 parts by weight of butyl acrylate, 1.0 part by weight of acrylic acid, 4-hydroxybutyl acrylate 1 0.0 part by weight and 0.1 part by weight of 2,2′-azobisisobutyronitrile were added, and after nitrogen substitution, the temperature was raised to 55 ° C. and a polymerization reaction was carried out for 15 hours. A solution of a (meth) acrylic polymer having a weight average molecular weight of 970,000 was obtained. The refractive index of this (meth) acrylic polymer was 1.46.

  A styrene oligomer (softening point: 72-77 ° C., weight average molecular weight: 1350, refractive index: 1.59, manufactured by Eastman Chemical Co., Ltd.) as a tackifier for 100 parts by weight of the solid content of the (meth) acrylic polymer. 40 parts by weight of picolastic A75), isocyanurate trimer of hexamethylene diisocyanate (manufactured by Mitsui Chemicals Polyurethane, Takenate D-170N), 0.1 part by weight of 3-glycidoxypropyltrimethoxysilane .1 part by weight was added to obtain a pressure-sensitive adhesive composition of the present invention.

  This pressure-sensitive adhesive composition was applied to 38 μm PET subjected to silicone release treatment so that the pressure-sensitive adhesive had a dry thickness of 15 μm, dried and cross-linked at 120 ° C. for 3 minutes, and (meth) acrylic polymer gel A pressure-sensitive adhesive layer having a fraction of 69% by weight and a refractive index of 1.50 was obtained.

  In addition, 20 parts by weight of a polystyrene resin (manufactured by PS Japan, HH105) was dissolved in 100 parts by weight of toluene to prepare a polystyrene solution.

  Next, the above polystyrene solution was applied to the surface of a 24 μm polyester (manufactured by Teijin DuPont, PET film G2, refractive index: 1.50), and a polystyrene layer (refractive index: 1.59, thickness after curing: 5 μm). And a microlens (f-number: 0.86) processed to a radius of 5 μm by hot pressing at 160 ° C. was obtained. Then, the said adhesive layer was transcribe | transferred to the polyester film side, and it was set as the optical sheet with an adhesive layer of Example 1.

[Example 2]
Example 1 except that the tackifier was changed to 80 parts by weight of a styrene oligomer (softening point: 82-85, weight average molecular weight: 1380, refractive index: 1.60, SX-85 manufactured by Yasuhara Chemical Co., Ltd.). In the same manner as described above, a pressure-sensitive adhesive layer having a gel fraction of 68% by weight and a refractive index of 1.52 was obtained. Further, this pressure-sensitive adhesive layer was transferred to the polyester film side of the microlens described in Example 1 to obtain an optical sheet with a pressure-sensitive adhesive layer in Example 2.

Example 3
While adding 30 parts by weight of styrene and 0.15 parts by weight of benzoyl peroxide as a polymerization initiator to 100 parts by weight of the solid content of the (meth) acrylic polymer of Example 1, while substituting with nitrogen The graft polymerization reaction was performed at 60 ° C. for 5 hours and at 70 ° C. for 8 hours to obtain a modified (meth) acrylic polymer. The refractive index of this modified (meth) acrylic polymer was 1.47.

  A copolymer of α-methylstyrene and styrene (softening point: 82-88 ° C., weight average molecular weight: 1200, refractive index: 1.61, manufactured by Eastman Chemical Co., Ltd.) was added to 100 parts by weight of the modified (meth) acrylic polymer. , Crystallex 3085) 80 parts by weight, trimethylolpropane tolylene diisocyanate adduct (Nihon Polyurethane Co., Coronate L) 0.15 parts by weight, 3-glycidoxypropyltriethoxysilane 0.1 part by weight The pressure-sensitive adhesive composition of the present invention was used.

  This pressure-sensitive adhesive composition was applied to 38 μm PET subjected to silicone release treatment so that the pressure-sensitive adhesive had a dry thickness of 15 μm, dried and cross-linked at 120 ° C. for 3 minutes, and (meth) acrylic polymer gel A pressure-sensitive adhesive layer having a fraction of 67% by weight and a refractive index of 1.53 was obtained. Further, this pressure-sensitive adhesive layer was transferred to the polyester film side of the microlens described in Example 1 to obtain an optical sheet with the pressure-sensitive adhesive layer of Example 3.

Example 4
A styrene oligomer (softening point: 82-85 ° C., weight average molecular weight: 1380, refractive index: 1.60, manufactured by Yasuhara Chemical Co., Ltd., SX-85) was added to 100 parts by weight of the modified (meth) acrylic polymer of Example 3. ) A pressure-sensitive adhesive layer having a (meth) acrylic polymer gel fraction of 67% and a refractive index of 1.51 was obtained in the same manner as in Example 3 except that the amount was 40 parts by weight. Further, this pressure-sensitive adhesive layer was transferred to the polyester film side of the microlens described in Example 1 to obtain an optical sheet with a pressure-sensitive adhesive layer of Example 4.

Example 5
In a reaction vessel equipped with a cooling tube, a nitrogen introduction tube, a thermometer, and a stirrer, 233 parts by weight of ethyl acetate as a solvent, 98.5 parts by weight of butyl acrylate, 0.5 parts by weight of acrylic acid, 4-hydroxybutyl acrylate 1 0.0 part by weight and 0.1 part by weight of 2,2′-azobisisobutyronitrile were added, and after nitrogen substitution, the temperature was raised to 55 ° C. and a polymerization reaction was carried out for 15 hours. A solution of a (meth) acrylic polymer having a weight average molecular weight of 1,120,000 was obtained.

  50 parts by weight of styrene and 2.5 parts by weight of 4-hydroxybutyl acrylate, and 0.25 part by weight of benzoyl peroxide as a polymerization initiator, based on 100 parts by weight of the solid content of this (meth) acrylic polymer Was added, and the graft polymerization reaction was carried out at 60 ° C. for 5 hours and at 70 ° C. for 8 hours to obtain a modified (meth) acrylic polymer. The refractive index of this modified (meth) acrylic polymer was 1.48.

  80 weight of styrene oligomer (softening point: 82-85 ° C., weight average molecular weight: 1380, refractive index: 1.60, manufactured by Yashara Chemical Co., SX-85) as a tackifier to 100 parts by weight of this modified (meth) acrylic polymer Part, 0.15 parts by weight of trimethylolpropane tolylene diisocyanate adduct (manufactured by Nippon Polyurethane Co., Ltd., Coronate L), 0.1 part by weight of 3-glycidoxypropyltriethoxysilane, and the pressure-sensitive adhesive composition of the present invention It was a thing.

  This pressure-sensitive adhesive composition was applied to 38 μm PET subjected to silicone release treatment so that the pressure-sensitive adhesive had a dry thickness of 15 μm, dried and cross-linked at 120 ° C. for 3 minutes, and (meth) acrylic polymer gel A pressure-sensitive adhesive layer having a fraction of 65% by weight and a refractive index of 1.53 was obtained. Further, this pressure-sensitive adhesive layer was transferred to the polyester film side of the microlens described in Example 1 to obtain an optical sheet with a pressure-sensitive adhesive layer of Example 5.

Example 6
Copolymer of α-methylstyrene and styrene (softening point: 82-88 ° C., weight average molecular weight: 1200, refractive index: 1.61, Eastman) to 100 parts by weight of the modified (meth) acrylic polymer of Example 5. Chemical Co., Ltd., Crystallex 3085) 40 parts by weight, styrene oligomer (softening point: room temperature or lower, weight average molecular weight: 430, refractive index: 1.60, Eastman Chemical Co., Ltd., Picolastic A5) 10 parts by weight, benzoyl par 0.3 parts by weight of oxide, 0.05 parts by weight of trimethylolpropane isophorone diisocyanate adduct (Mitsui Chemical Polyurethane, Takenate D-140N) and 0.2 parts by weight of 3-glycidoxypropyltriethoxysilane were added. The pressure-sensitive adhesive composition of the present invention was used.

  This pressure-sensitive adhesive composition was applied to 38 μm PET subjected to silicone release treatment so that the dry thickness of the pressure-sensitive adhesive was 15 μm, dried and cross-linked at 140 ° C. for 3 minutes, and a (meth) acrylic polymer gel A pressure-sensitive adhesive layer having a fraction of 60% by weight and a refractive index of 1.52 was obtained.

  This was affixed to a light diffusion sheet having a thickness of 100 μm to obtain an optical sheet with an adhesive layer of Example 6.

Example 7
An optical sheet with an adhesive layer of Example 7 (refraction index of the adhesive: 1.46, (meth)) The gel fraction of the acrylic polymer was 70% by weight).

Example 8
In the graft polymerization reaction of the modified (meth) acrylic polymer of Example 5, the same operation as in Example 5 was performed except that 40 parts by weight of styrene and 10 parts by weight of acryloylmorpholine were used. A pressure-sensitive adhesive layer having a gel fraction of 68% by weight and a refractive index of 1.54 was obtained. Further, this pressure-sensitive adhesive layer was transferred to the polyester film side of the microlens described in Example 1 to obtain an optical sheet with a pressure-sensitive adhesive layer in Example 8.

Example 9
In a reaction vessel equipped with a cooling pipe, a nitrogen introduction pipe, a thermometer, and a stirrer, 233 parts by weight of ethyl acetate as a solvent, 92 parts by weight of butyl acrylate, 2 parts by weight of acrylic acid, 1 part by weight of 4-hydroxybutyl acrylate, After 5 parts by weight of acryloylmorpholine and 0.1 part by weight of 2,2′-azobisisobutyronitrile were added and purged with nitrogen, the temperature was raised to 55 ° C. and a polymerization reaction was carried out for 15 hours. A solution of a (meth) acrylic polymer having a weight average molecular weight of 1.18 million was obtained. The refractive index of this (meth) acrylic polymer was 1.47.

  A styrene oligomer (softening point: 72-77 ° C., weight average molecular weight: 1350, refractive index: 1.59, manufactured by Eastman Chemical Co., Ltd.) as a tackifier for 100 parts by weight of the solid content of this (meth) acrylic polymer. 40 parts by weight of Picolastic A75), 0.1 part by weight of hexamethylene diisocyanate adduct of trimethylolpropane (Mitsui Chemical Polyurethane, Takenate D-160N), 3-glycidoxypropyltrimethoxysilane 0 .1 part by weight was added to obtain a pressure-sensitive adhesive composition of the present invention.

  The pressure-sensitive adhesive composition was applied to 38 μm PET subjected to silicone release treatment so that the pressure-sensitive adhesive layer had a dry thickness of 15 μm, dried and crosslinked at 120 ° C. for 3 minutes, and the (meth) acrylic polymer An adhesive layer having a gel fraction of 66% and a refractive index of 1.51 was obtained. Further, this pressure-sensitive adhesive layer was transferred to the polyester film side of the microlens described in Example 1 to obtain an optical sheet with a pressure-sensitive adhesive layer of Example 9.

Example 10
While adding 30 parts by weight of styrene and 0.15 parts by weight of benzoyl peroxide as a polymerization initiator to 100 parts by weight of the solid content of the (meth) acrylic polymer of Example 9, while substituting with nitrogen The graft polymerization reaction was performed at 60 ° C. for 5 hours and at 70 ° C. for 8 hours to obtain a modified (meth) acrylic polymer. The refractive index of this modified (meth) acrylic polymer was 1.48.

  A copolymer of α-methylstyrene and styrene (softening point: 82-88 ° C., weight average molecular weight: 1200, refractive index: 1.61, manufactured by Eastman Chemical Co., Ltd.) was added to 100 parts by weight of the modified (meth) acrylic polymer. , Crystallex 3085) 80 parts by weight, trimethylolpropane tolylene diisocyanate adduct (Japan Polyurethane Co., Coronate L) 0.1 parts by weight, 3-glycidoxypropyltriethoxy silane 0.1 parts by weight And it was set as the adhesive composition.

  This pressure-sensitive adhesive composition was applied to 38 pm PET subjected to silicone release treatment so that the dry thickness of the pressure-sensitive adhesive was 15 μm, dried and crosslinked at 120 ° C. for 3 minutes, and a gel of (meth) acrylic polymer An adhesive layer having a fraction of 63% and a refractive index of 1.54 was obtained. Further, this pressure-sensitive adhesive layer was transferred to the polyester film side of the microlens described in Example 1 to obtain an optical sheet with a pressure-sensitive adhesive layer of Example 10.

Example 11
When the modified (meth) acrylic polymer of Example 8 was subjected to a graft polymerization reaction, the same operation as in Example 8 was performed except that N, N-dimethylacrylamide was used instead of acryloylmorpholine, and the above (meth) A pressure-sensitive adhesive layer having an acrylic polymer gel fraction of 70% by weight and a refractive index of 1.54 was obtained. Furthermore, this pressure-sensitive adhesive layer was transferred to the polyester film side of the microlens described in Example 1 to obtain an optical sheet with a pressure-sensitive adhesive layer in Example 11.

Example 12
In a reaction vessel equipped with a cooling tube, a nitrogen introduction tube, a thermometer, and a stirrer, 233 parts by weight of ethyl acetate as a solvent, 99 parts by weight of butyl acrylate, 0.5 parts by weight of acrylic acid, 4-hydroxybutyl acrylate 0 0.5 part by weight and 0.1 part by weight of 2,2′-azobisisobutyronitrile were added, and after nitrogen substitution, the temperature was raised to 55 ° C. and a polymerization reaction was carried out for 15 hours. A solution of a (meth) acrylic polymer having a weight average molecular weight of 1.30,000 was obtained.

  40 parts by weight of styrene and 2 parts by weight of 4-hydroxybutyl acrylate are added to 100 parts by weight of the solid content of this (meth) acrylic polymer, and 0.20 part by weight of benzoyl peroxide is added as a polymerization initiator. While performing nitrogen substitution, a graft polymerization reaction was carried out at 60 ° C. for 5 hours and at 70 ° C. for 8 hours to obtain a modified (meth) acrylic polymer. The refractive index of this modified (meth) acrylic polymer was 1.47.

  Copolymer of α-methylstyrene and styrene (softening point: 82-88 ° C., weight average molecular weight: 1200, refractive index: 1.61, based on 100 parts by weight of the solid content of the modified (meth) acrylic polymer. Eastman Chemical Co., Ltd., Crystallex 3085) 60 parts by weight, trimethylolpropane xylylene diisocyanate adduct (Mitsui Chemical Polyurethane, Takenate D-110N) 0.2 parts by weight, 3-glycidoxypropyltriethoxysilane 0.1 part by weight of silane was blended to prepare an adhesive composition.

  This pressure-sensitive adhesive composition was applied to 38 μm PET subjected to silicone release treatment so that the pressure-sensitive adhesive had a dry thickness of 15 μm, dried and cross-linked at 120 ° C. for 3 minutes, and (meth) acrylic polymer gel A pressure-sensitive adhesive layer having a fraction of 74% by weight and a refractive index of 1.52 was obtained. Further, this pressure-sensitive adhesive layer was transferred to the polyester film side of the microlens described in Example 1 to obtain an optical sheet with a pressure-sensitive adhesive layer of Example 12.

Example 13
To 100 parts by weight of the modified (meth) acrylic polymer of Example 12, 80 parts of a styrene oligomer (softening point: 82-85 ° C., weight average molecular weight: 1380, refractive index: 1.60, manufactured by Yashara Chemical Co., SX-85) , 0.15 part of hydrogenated xylylene diisocyanate adduct of trimethylolpropane (Mitsui Chemicals Polyurethanes, Takenate D-120N), 0.1 part by weight of 3-glycidoxypropyltriethoxysilane, It was set as the composition.

  This pressure-sensitive adhesive composition was applied to 38 μm PET subjected to silicone release treatment so that the pressure-sensitive adhesive had a dry thickness of 15 μm, dried and cross-linked at 120 ° C. for 3 minutes, and (meth) acrylic polymer gel A pressure-sensitive adhesive layer having a fraction of 71% by weight and a refractive index of 1.53 was obtained. Further, this pressure-sensitive adhesive layer was transferred to the polyester film side of the microlens described in Example 1 to obtain an optical sheet with a pressure-sensitive adhesive layer in Example 13.

Example 14
In a reaction vessel equipped with a cooling pipe, a nitrogen introduction pipe, a thermometer, and a stirrer, 233 parts by weight of ethyl acetate as a solvent, 99 parts by weight of butyl acrylate, 1 part by weight of 4-hydroxybutyl acrylate, 2,2′- After adding 0.1 part by weight of azobisisobutyronitrile and carrying out nitrogen substitution, the temperature was raised to 55 ° C. and a polymerization reaction was carried out for 15 hours. A solution of a (meth) acrylic polymer having a weight average molecular weight of 930,000 was obtained.

  50 parts by weight of styrene and 2.5 parts by weight of 4-hydroxybutyl acrylate are added to 100 parts by weight of the solid content of this (meth) acrylic polymer, and 0.25 parts by weight of benzoyl peroxide as a polymerization initiator. Was added, and a graft polymerization reaction was performed at 60 ° C. for 5 hours and at 70 ° C. for 8 hours to obtain a modified (meth) acrylic polymer. The refractive index of this modified (meth) acrylic polymer was 1.48.

  Styrene oligomer (softening point: 82-85 ° C., weight average molecular weight: 1380, refractive index: 1.60, manufactured by Yashara Chemical Co., SX-85) with respect to 100 parts by weight of the solid content of the modified (meth) acrylic polymer. 80 parts by weight, 1 part by weight of xylylene diisocyanate adduct of trimethylolpropane (Mitsui Chemical Polyurethane, Takenate D-110N), 0.1 part by weight of 3-glycidoxypropyltriethoxysilane, It was set as the composition.

  This pressure-sensitive adhesive composition was applied to 38 μm PET subjected to silicone release treatment so that the pressure-sensitive adhesive had a dry thickness of 15 μm, dried and cross-linked at 120 ° C. for 3 minutes, and (meth) acrylic polymer gel A pressure-sensitive adhesive layer having a fraction of 82% by weight and a refractive index of 1.53 was obtained. Further, this pressure-sensitive adhesive layer was transferred to the polyester film side of the microlens described in Example 1 to obtain an optical sheet with a pressure-sensitive adhesive layer of Example 14.

Example 15
40 parts by weight of styrene and 2 parts by weight of 4-hydroxybutyl acrylate are added to 100 parts by weight of the solid content of the (meth) acrylic polymer of Example 14, and 0.20 weight by weight of benzoyl peroxide as a polymerization initiator. Part was added, and grafting reaction was performed at 60 ° C. for 5 hours and at 70 ° C. for 8 hours while replacing with nitrogen to obtain a modified (meth) acrylic polymer. The refractive index of this modified (meth) acrylic polymer was 1.47.

  Copolymer of α-methylstyrene and styrene (softening point: 82-88 ° C., weight average molecular weight: 1200, refractive index: 1.61, based on 100 parts by weight of the solid content of the modified (meth) acrylic polymer. Eastman Chemical Co., Ltd., Crystallex 3085) 60 parts by weight, trimethylolpropane hydrogenated xylylene diisocyanate adduct (Mitsui Chemical Polyurethane, Takenate D-120N) 0.7 parts by weight, 3-glycidoxypropyltri 0.1 parts by weight of ethoxysilane was blended to prepare an adhesive composition.

  This pressure-sensitive adhesive composition was applied to 38 μm PET subjected to silicone release treatment so that the pressure-sensitive adhesive had a dry thickness of 15 μm, dried and cross-linked at 120 ° C. for 3 minutes, and (meth) acrylic polymer gel A pressure-sensitive adhesive layer having a fraction of 80% by weight and a refractive index of 1.52 was obtained. Further, this pressure-sensitive adhesive layer was transferred to the polyester film side of the microlens described in Example 1 to obtain an optical sheet with a pressure-sensitive adhesive layer of Example 15.

Example 16
In the pressure-sensitive adhesive composition of Example 5, melamine-formaldehyde condensate particles (manufactured by Nippon Shokubai Co., Ltd., Eposter S6) were added as light-transmitting non-colored particles to 30 parts by weight of the modified (meth) acrylic polymer. The pressure-sensitive adhesive composition of the present invention was made uniform by adding parts by weight.

  The pressure-sensitive adhesive composition was applied in a uniform state to 38 μm PET subjected to silicone release treatment so that the dry thickness of the pressure-sensitive adhesive was 15 μm, and dried and crosslinked at 120 ° C. for 3 minutes. A pressure-sensitive adhesive layer having an acrylic polymer gel fraction of 60% by weight and a refractive index of 1.53 was obtained. Further, this pressure-sensitive adhesive layer was transferred to the polyester film side of the microlens described in Example 1 to obtain an optical sheet with the pressure-sensitive adhesive layer of Example 16.

Example 17
30 parts by weight of phenoxyethyl acrylate and 1.5 parts by weight of 4-hydroxybutyl acrylate are added to 100 parts by weight of the solid content of the (meth) acrylic polymer of Example 14, and benzoyl peroxide is further used as a polymerization initiator. While adding 0.15 part by weight and carrying out nitrogen substitution, a graft polymerization reaction was performed at 60 ° C. for 5 hours and at 70 ° C. for 8 hours to obtain a modified (meth) acrylic polymer. The refractive index of this modified (meth) acrylic polymer was 1.48.

  Styrene oligomer (softening point: 82-85 ° C., weight average molecular weight: 1380, refractive index: 1.60, manufactured by Yashara Chemical Co., SX-85) with respect to 100 parts by weight of the solid content of the modified (meth) acrylic polymer. 40 parts by weight, 0.5 parts by weight of xylylene diisocyanate adduct of trimethylolpropane (Mitsui Chemical Polyurethane, Takenate D-110N), 0.1 parts by weight of 3-glycidoxypropyltriethoxysilane are blended, It was set as the adhesive composition.

  This pressure-sensitive adhesive composition was applied to 38 μm PET subjected to silicone release treatment so that the pressure-sensitive adhesive had a dry thickness of 15 μm, dried and cross-linked at 120 ° C. for 3 minutes, and (meth) acrylic polymer gel A pressure-sensitive adhesive layer having a fraction of 75% by weight and a refractive index of 1.52 was obtained. Further, this pressure-sensitive adhesive layer was transferred to the polyester film side of the microlens described in Example 1 to obtain an optical sheet with a pressure-sensitive adhesive layer of Example 17.

Example 18
30 parts by weight of benzyl acrylate and 1.5 parts by weight of 4-hydroxybutyl acrylate are added to 100 parts by weight of the solid content of the (meth) acrylic polymer of Example 14, and benzoyl peroxide 0 is further added as a polymerization initiator. .15 parts by weight was added and nitrogen substitution was performed, and a graft polymerization reaction was performed at 60 ° C. for 5 hours and at 70 ° C. for 8 hours to obtain a modified (meth) acrylic polymer. The refractive index of this modified (meth) acrylic polymer was 1.48.

  Styrene oligomer (softening point: 82-85 ° C., weight average molecular weight: 1380, refractive index: 1.60, manufactured by Yashara Chemical Co., SX-85) with respect to 100 parts by weight of the solid content of the modified (meth) acrylic polymer. 80 parts by weight, 1.0 part by weight of tolylene diisocyanate adduct of trimethylolpropane (manufactured by Nippon Polyurethane Co., Ltd., Coronate L), 0.1 part by weight of 3-glycidoxypropyltriethoxysilane, It was a thing.

  This pressure-sensitive adhesive composition was applied to 38 μm PET subjected to silicone release treatment so that the pressure-sensitive adhesive had a dry thickness of 15 μm, dried and cross-linked at 120 ° C. for 3 minutes, and (meth) acrylic polymer gel A pressure-sensitive adhesive layer having a fraction of 81% by weight and a refractive index of 1.54 was obtained. Further, this pressure-sensitive adhesive layer was transferred to the polyester film side of the microlens described in Example 1 to obtain an optical sheet with a pressure-sensitive adhesive layer in Example 18.

[Comparative Example 1]
The optical sheet of Comparative Example 1 was evaluated by leaving three sheets of the diffusion plate, BEF, and diffusion plate that were placed on the backlight without attaching the optical sheet with the adhesive layer to the light source.

[Comparative Example 2]
In Example 1, the same operation was performed except that the amount of the isocyanate-based crosslinking agent was 0.5 parts by weight. The gel fraction of the (meth) acrylic polymer was 93% by weight.

[Comparative Example 3]
In Example 1, the same operation was performed except that the amount of the isocyanate crosslinking agent was 0.02 part by weight. The gel fraction of the (meth) acrylic polymer was 30% by weight.

  The following evaluation was performed about the optical sheet (optical film with an adhesive) obtained by the Example and the comparative example. The results are shown in Table 1.

<Measurement of molecular weight>
The weight average molecular weight of the obtained (meth) acrylic polymer was measured by GPC (gel permeation chromatography).
・ Analyzer: HLC-8120GPC manufactured by Tosoh Corporation
Column: manufactured by Tosoh Corporation, G7000H _XL + GMH _XL -H + GMH _XL
-Low molecular weight column: manufactured by Tosoh Corporation, GMH _HR -H + GMH _HR + G2000 MH _HR
Column size: 7.8 mmφ x 30 cm each (total 90 cm)
-Column temperature: 40 ° C
・ Flow rate: 0.8ml / min
・ Injection volume: 100 μl
・ Eluent: Tetrahydrofuran ・ Detector: Differential refractometer (RI)
The molecular weight was calculated in terms of polystyrene.

<Measurement of gel fraction>
W ₁ g of the pressure-sensitive adhesive layer prepared in each Example / Comparative Example was taken out and immersed in ethyl acetate at room temperature (about 25 ° C.) for 7 days. Then, the pressure-sensitive adhesive layer (insoluble matter) subjected to the immersion treatment was taken out from ethyl acetate, and the weight W ₂ g after drying at 130 ° C. for 2 hours was measured.

Furthermore, when the weight part of the tackifier is 100 parts by weight with respect to 100 parts by weight of the pressure-sensitive adhesive polymer ((meth) acrylic polymer) when the pressure-sensitive adhesive is blended,
Gel fraction (% by weight) = (W ₂ / W ₁ ) × (100 + A)
As calculated. In this example and comparative example, the tackifier is completely dissolved in the state immersed in ethyl acetate without being taken into the crosslinked structure of the polymer.

<Measurement of adhesive strength>
A polyester adhesive tape (Nitto Denko, No. 31B) is attached as a backing to the uneven processed surface of the optical sheet (width 25 mm) obtained in Examples and Comparative Examples, and it is applied to a non-alkali glass with a 2 kg roller. The roll was reciprocated for pasting. Then, after processing for 30 minutes in an autoclave at 50 ° C. and 0.5 MPa, after leaving for 3 hours in an atmosphere of 23 ° C. × 50% RH, the peel adhesive strength (N / 20 mm) at a peel angle of 90 ° and a peel speed of 300 mm / min. ) Was measured.

  Further, after the above autoclave treatment, it was stored at 60 ° C. for 6 hours, left in a 23 ° C. × 50% RH atmosphere for 3 hours, and then measured for peel adhesive strength at a peel angle of 90 ° and a peel speed of 300 mm / min. Was the adhesive strength (N / 20 mm) after heating.

<Measurement of refractive index>
Under an atmosphere of 25 ° C., sodium D line (589 nm) was irradiated, and the refractive index was measured using an Abbe refractometer (manufactured by ATAGO, DR = M4).

<Measurement of brightness>
The optical sheet with the pressure-sensitive adhesive layer is pasted on the light guide plate of the backlight of a 17-inch color display (SyncMaster 712N) manufactured by Samsung Electronics Co., Ltd. The backlight system (light source) has a structure in which optical films formed by processing of increasing unevenness are sequentially laminated. Furthermore, the diffuser plate, BEF, and diffuser plate that were used in this display were stacked as they were, using TOPCON Bm-9 as the luminance meter, the distance between the light source and the luminance meter being 350 mm, a 20 mm square part A luminance meter was aligned with the center of the light source shielded from light and the luminance was measured (cd / cm ² ) in a dark room.

<Measurement of dynamic viscoelasticity>
The dynamic viscoelasticity was measured under the following conditions.
・ Equipment: ARES manufactured by TA Instruments
-Deformation mode: Torsion-Measurement frequency: Constant frequency 1 Hz
・ Temperature increase rate: 5 ° C./min ・ Measurement temperature: Measured from near the glass transition temperature of the adhesive to 160 ° C. ・ Shape: Parallel plate 8.0 mmφ
・ Sample thickness: 0.5-2mm (initial stage)
The storage elastic modulus (G ′) at 23 ° C. was read.

  In the present invention, the storage elastic modulus (G ′) at 23 ° C. measured by dynamic viscoelasticity is 10,000 to 1,000,000 Pa, preferably 30,000 to 500,000 Pa, more preferably. A pressure sensitive adhesive of 40,000 to 400,000 Pa is used. If the storage elastic modulus (G ′) is too small, the pressure-sensitive adhesive protrudes and the workability and workability are deteriorated. On the other hand, if the storage elastic modulus (G ′) is too large, the adhesiveness decreases, which is not preferable. .

By setting it as such a range, a peeling film can be peeled off from the optical sheet with an adhesive layer of this invention, and it can be easily and easily affixed on a to-be-adhered body at room temperature, and workability | operativity improves greatly. Hereinafter, the measurement results of the storage elastic modulus will be shown.
(Example 1) 70,000 Pa
(Example 2) 85,000 Pa
(Example 3) 155,000 Pa
(Example 4) 104,000 Pa
(Example 5) 202,000 Pa
(Example 6) 116,000 Pa
(Example 7) 132,000 Pa
(Example 8) 264,000 Pa
(Example 9) 170,000 Pa
(Example 10) 272,000 Pa
(Example 11) 255,000 Pa
(Example 12) 133,000 Pa
(Example 13) 146,000 Pa
(Example 14) 196,000 Pa
(Example 15) 188,000 Pa
(Example 16) 292,000 Pa
(Example 17) 104,000 Pa
(Example 18) 96,000 Pa

<Foaming test when affixed to an acrylic plate>
The pressure-sensitive adhesive surface of the optical sheet with the pressure-sensitive adhesive layer obtained in Examples and Comparative Examples was attached to an acrylic plate (Sumitomo Chemical Co., Sumipex E00, thickness: 2 mm), and 30 at 50 ° C. and 0.5 MPa autoclave. After the minute treatment, it was put into a dryer at 70 ° C. and 80 ° C., and the presence or absence of foaming after 24 hours was observed.

  In Examples 1 to 18, foaming was not observed at 70 ° C. and 80 ° C. On the other hand, in Comparative Examples 2 and 3, foaming was not observed at 70 ° C., but foaming was observed at 80 ° C.

  The results of the measurement and evaluation are shown in Table 1.

  From Table 1, it was found that all of the optical sheets with pressure-sensitive adhesives produced in Examples 1 to 18 were excellent in adhesiveness and greatly improved in luminance.

It is sectional drawing which shows the one aspect | mode of the backlight system of this invention. It is sectional drawing which shows the one aspect | mode of the backlight system of this invention. It is sectional drawing which shows the one aspect | mode of the backlight system of this invention. It is sectional drawing which shows the one aspect | mode of the backlight system of this invention. It is sectional drawing which shows the one aspect | mode of the backlight system of this invention. It is sectional drawing which shows the one aspect | mode of the illuminating device of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1: Laminated optical film 10: Microlens sheet | seat l2: Diffusion sheet 14: Brightness improvement film 20: Adhesive layer 3: Light source unit 30: Light guide 32: Issue device (light source)
40: Adhesive layer 50: Liquid crystal module 6: Backlight system

Claims (16)

The adherend from which light is emitted and the optical film that has been subjected to the concave-convex processing so as to increase the surface area are joined via an adhesive layer containing an adhesive polymer having a gel fraction of 35 to 85%. And
The optical film is a laminate of a plurality of optical films,
The refractive index of the adherend is smaller than the refractive index of the pressure-sensitive adhesive layer, and the refractive index of the pressure-sensitive adhesive layer is smaller than the refractive index of at least one layer of the multilayer optical film,
An adhesive layer is affixed to the opposite surface of the optical film that has been subjected to the uneven processing ,
Backlight system storage elastic modulus at 23 ° C. of the pressure-sensitive adhesive layer is characterized 10,000~1,000,000Pa der Rukoto. The backlight system according to claim 1, wherein the adherend is a light source, a light guide, or a light source unit. The backlight system according to claim 1, wherein the optical film is a microlens and / or a light diffusing plate. The backlight system according to any one of claims 1 to third refractive index of the adhesive layer is 1.50 or more. The image display apparatus containing the backlight system in any one of Claims 1-4 . The illuminating device containing the backlight system in any one of Claims 1-4 . The optical sheet with an adhesive formed by laminating | stacking an adhesive layer on the outermost layer of the said optical film used for the backlight system in any one of Claims 1-4 . 10 to 150 parts by weight of a tackifier having an aromatic ring with respect to 100 parts by weight of a (meth) acrylic polymer obtained by copolymerizing 0.1 to 10% by weight of a hydroxyl group-containing monomer, and a crosslinking agent The optical sheet with pressure-sensitive adhesive according to claim 7 , comprising a pressure-sensitive adhesive composition containing 0.03 to 2 parts by weight. A modified (meth) acrylic polymer obtained by copolymerizing a (meth) acrylic polymer obtained by copolymerizing the (meth) acrylic polymer with a hydroxyl group-containing monomer in an amount of 0.1 to 10% by weight. The optical sheet with pressure-sensitive adhesive according to claim 8 . The (meth) acrylic polymer is copolymerized with 0.1 to 20% by weight of nitrogen-containing monomer, 0.1 to 5% by weight of carboxyl group-containing monomer, and 0.1 to 10% by weight of hydroxyl group-containing monomer. The optical sheet with pressure-sensitive adhesive according to claim 8 or 9 , which is a (meth) acrylic polymer. The pressure-sensitive adhesive according to any one of claims 8 to 10, wherein the pressure-sensitive adhesive composition further comprises 0.01 to 2 parts by weight of a silane coupling agent with respect to 100 parts by weight of the (meth) acrylic polymer. Attached optical sheet. The optical sheet with pressure-sensitive adhesive according to any one of claims 8 to 11 , wherein the (meth) acrylic polymer is a (meth) acrylic polymer obtained by copolymerizing 50 to 99% by weight of n-butyl acrylate. The optical sheet with pressure-sensitive adhesive according to any one of claims 7 to 12 , wherein the pressure-sensitive adhesive layer is a pressure-sensitive adhesive layer containing light-transmitting non-colored particles dispersed therein and exhibiting light diffusibility. The optical sheet with pressure-sensitive adhesive according to any one of claims 7 to 13 , wherein the pressure-sensitive adhesive layer has a thickness of 2 to 100 µm. And the adherend from which light is emitted, and an optical film subjected to uneven processing such surface area increases, more of claims 1-4, characterized in that it comprises a step of bonding through an adhesive layer A manufacturing method of the backlight system according to claim 1. A backlight system according to any one of claims 1 to 4 , wherein the brightness of emitted light is improved.

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