JP5258332B2 - Light scattering adhesive composition, light scattering adhesive layer, light scattering adhesive sheet, and backlight system using them - Google Patents

Description

  The present invention has less reflection of light at the interface with the optical member (optical film, optical sheet, etc.), is excellent in adhesiveness and cohesive force, is also excellent in long-term durability, and further improves the brightness. The present invention relates to a light scattering pressure-sensitive adhesive composition that can realize energy saving, a light scattering pressure-sensitive adhesive sheet provided with a light scattering pressure-sensitive adhesive layer using the pressure-sensitive adhesive composition, and a backlight system that efficiently emits light using these. .

  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.

  In order to emit light from such a light source uniformly, the design of the light guide plate and the design such as the shape and arrangement of the light-emitting body itself such as a cold cathode tube and LED have been devised, and light is emitted with as low power as possible. Ingenuity has been made. 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 commercially available monitors and the like, the diffusion plate that makes the light emitted from the light guide plate integrated with the light source uniform is only on (mounted on) the light guide plate. It was confirmed that there was a loss of light because there was a thin air layer between the diffusion plate and the diffusion plate. 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.

  Moreover, fixing the light guide plate and the prism sheet which is an optical member using the time of adhesion is disclosed (Patent Document 1). As the pressure-sensitive adhesive used here, an acrylic pressure-sensitive adhesive having good transparency and weather resistance is used, but the refractive index of the optical member is 1.50 to 1.55 for glass and 1.54 for polycarbonate. , Triacetylcellulose 1.50, and there is a large difference from the general refractive index of 1.46 for acrylic adhesives, resulting in a difference in refractive index at the interface between the optical member and the adhesive, and light at a shallow angle. When the light enters, total reflection occurs, resulting in a phenomenon that the effective use of light is hindered. In this case, the refractive index measurement wavelength is 589 nm.

  In Patent Document 2, the refractive index using an acrylic polymer obtained by copolymerizing an acrylic monomer having an aromatic group substituted with bromine and an acrylic monomer having an aromatic group not substituted with bromine is 1. 48 or more pressure-sensitive adhesives are disclosed, and Patent Document 3 discloses a pressure-sensitive adhesive having an index of refraction of 1.49 to 1.60 using an acrylic polymer copolymerized with a monomer having an aromatic group. No. 4 discloses a pressure-sensitive adhesive having a refractive index of 1.50 to 1.55 using an acrylic polymer containing 40 to 90% by weight of a monomer having an aromatic group.

  In addition, in order to synthesize a polymer having a high refractive index, it is disclosed that an aromatic ring or a monomer into which bromine is introduced is copolymerized (Non-patent Document 1).

  However, when the refractive index of the pressure-sensitive adhesive is adjusted to be high by the methods described in Patent Documents 2 to 4, it is necessary to increase the copolymerization ratio. In this case, the adhesiveness is significantly reduced. A trade-off phenomenon is observed and causes problems. In addition, it is complicated to adjust the copolymerization ratio.

  In addition, use of a halogen such as bromine in Patent Document 2 is not preferable from the viewpoint of environmental measures, and is not preferable particularly in applications in the electric / electronic field.

  In Patent Documents 5 and 6, attempts have been made to adjust the refractive index and adhesive force of the pressure-sensitive adhesive using a tackifier. Patent Document 7 discloses an acrylic pressure-sensitive adhesive having a molecular weight of 1900 or less. A pressure-sensitive adhesive containing a system refractive index adjusting agent is disclosed.

  The above Patent Documents 5 and 6 have the convenience (workability) that the refractive index of the pressure-sensitive adhesive can be adjusted only by using the refractive index adjusting agent, but a general acrylic pressure-sensitive adhesive is a tackifier. When the amount of the refractive index adjusting agent is increased, it becomes cloudy and causes a problem. Moreover, in patent document 7, in order to eliminate the said problem, although the low molecular weight refractive index regulator is used, the problem that the heat resistance of an adhesive falls arises.

  In addition, as a method for imparting a light scattering function to an adhesive, Patent Document 8 discloses a method in which resin particles are added to an adhesive to cause light scattering. Patent Document 9 proposes a method of using a light scattering adhesive as an alternative to a light diffusing plate, and Patent Document 10 proposes a light scattering adhesive defined by the refractive index and volume content of a matrix and a spherical filler. Yes.

  Patent Documents 11 and 12 propose a surface light source device that is bonded to a prism sheet via a light diffusion adhesive of a directional light scattering film, further suppresses reflection at the interface, and refraction with a particle size of 1 to 100 nm. A method of increasing the refractive index by adding fine particles having an index of 1.8 or more to an adhesive has been proposed.

  However, in Patent Documents 8 to 10, there is no specific description regarding the pressure-sensitive adhesive composition, and it is unclear what type of pressure-sensitive adhesive is suitable as the light-scattering pressure-sensitive adhesive.

  In Patent Documents 11 and 12, there is no specific description regarding the pressure-sensitive adhesive composition, and it is unclear what type of pressure-sensitive adhesive is suitable as a light-scattering pressure-sensitive adhesive. A method for adjusting the rate is not disclosed.

"Optical properties of polymers" (by Yasuhiro Koike, Kyoritsu Shuppan, 1994, pages 11-13) JP-A-10-301109 JP 2003-535921 A JP 2002-173656 A JP 2003-13029 A JP 2000-321960 A JP 2002-14225 A JP 2003-342546 A JP 7-216328 A JP 2004-145155 A JP 2004-333716 A JP-A-2005-44744 JP 2005-50654 A

  Therefore, in order to address the above-mentioned problems, the present invention is a light provided with a light-scattering pressure-sensitive adhesive layer that has low reflection of light at the interface with the optical member, excellent adhesion and cohesion, and excellent long-term durability. The purpose of the present invention is to provide a backlight system that is a technology that can attach a scattering adhesive sheet to an adherend that emits light to efficiently emit light, and further contributes to energy saving and long life. And

  As a result of intensive studies to achieve the above-mentioned object, the present inventors have used the following light scattering pressure-sensitive adhesive composition, light scattering pressure-sensitive adhesive layer, light scattering pressure-sensitive adhesive sheet and a backlight system using these. The inventors have found that the above object can be achieved and have completed the present invention.

  That is, the light scattering pressure-sensitive adhesive composition of the present invention is 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. The (meth) acrylic pressure-sensitive adhesive composition containing 150 parts by weight and 0.03 to 2 parts by weight of a crosslinking agent contains transparent particles and has a haze value of 20 to 90%.

  In the light scattering adhesive composition of the present invention, the (meth) acrylic polymer is preferably a (meth) acrylic polymer obtained by copolymerizing a high refractive index monomer.

  The light scattering pressure-sensitive adhesive composition of the present invention preferably contains 1 to 70 parts by weight of the transparent particles with respect to 100 parts by weight of the (meth) acrylic pressure-sensitive adhesive composition.

  In the light scattering adhesive composition of the present invention, the transparent particles preferably have an average particle size of 0.1 to 30 μm.

  In the light scattering pressure-sensitive adhesive composition of the present invention, the (meth) acrylic pressure-sensitive adhesive composition contains 0.01 to 2 parts by weight of a silane coupling agent with respect to 100 parts by weight of the (meth) acrylic polymer. It is preferable.

  In the light scattering adhesive composition of the present invention, the (meth) acrylic polymer is preferably a (meth) acrylic polymer obtained by copolymerizing 50 to 99% by weight of n-butyl acrylate.

  The light scattering pressure-sensitive adhesive layer of the present invention is preferably composed of the light scattering pressure-sensitive adhesive composition.

  The light scattering adhesive layer of the present invention preferably has a refractive index of 1.50 or more.

  In the light scattering pressure-sensitive adhesive layer of the present invention, the refractive index of the transparent particles is larger than the refractive index of the pressure-sensitive adhesive layer, and the refractive index difference between the refractive index of the transparent particles and the refractive index of the pressure-sensitive adhesive layer is It is preferable that it is 0.01 or more.

  The light scattering adhesive layer of the present invention preferably has a storage elastic modulus at 23 ° C. of 10,000 to 1,000,000 Pa.

  The light scattering pressure-sensitive adhesive sheet of the present invention is a light scattering pressure-sensitive adhesive sheet formed by forming the pressure-sensitive adhesive layer on a support, and the thickness of the pressure-sensitive adhesive layer is preferably 2 to 100 μm.

  The backlight system of the present invention is preferably formed by forming the light scattering adhesive sheet on an adherend to which light is irradiated.

  Since the light-scattering pressure-sensitive adhesive composition of the present invention contains transparent particles in the pressure-sensitive adhesive composition, the light-scattering pressure-sensitive adhesive layer using the pressure-sensitive adhesive composition is applied to an adherend from which light is emitted. By sticking, the luminance can be greatly improved, and further, with the improvement in luminance, there is also an energy saving advantage, which is effective.

  In addition, by using the light scattering pressure-sensitive adhesive layer using the light scattering pressure-sensitive adhesive composition of the present invention, the optical member (optical sheet, optical film, etc.) and less light reflection at the interface, adhesiveness and cohesive force, A light-scattering adhesive sheet with excellent long-term durability can be obtained. By sticking this adhesive sheet to an adherend that emits light, it is possible to emit light efficiently and further save energy. It is possible and effective to obtain a backlight system that contributes to a long service life.

  Hereinafter, embodiments of the present invention will be described in detail.

  The light scattering pressure-sensitive adhesive composition of the present invention contains a (meth) acrylic polymer obtained by copolymerizing 0.1 to 10% by weight of a hydroxyl group-containing monomer.

  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 0.1 to 10% by weight, preferably 0.3 to 7% by weight, more preferably 0.3 to 3% 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.

  Further, the (meth) acrylic polymer is preferably a (meth) acrylic polymer obtained by copolymerizing a high refractive index monomer having a homopolymer having a refractive index of 1.50 or more.

  Specific examples of the high refractive index monomer include styrene derivatives having aromatic rings such as styrene and α-methylstyrene, benzyl (meth) acrylate, naphthyl (meth) acrylate, phenoxyethyl (meth) acrylate, and phenoxybutyl. (Meth) acrylate, derivatives such as vinyltoluene and α-vinyltoluene. By using a high refractive index monomer, further improvement of the refractive index can be expected, which is effective.

  When the high refractive index monomer is used, it is copolymerized in an amount of 10 to 50% by weight, preferably 15 to 40% by weight. If the content of the high refractive index monomer is too small, the refractive index cannot be improved, and if it is too large, the adhesiveness may be lowered.

  Further, as the (meth) acrylic polymer, a (meth) acrylic monomer having an alkyl group to be copolymerized is used, and ethyl (meth) acrylate, propyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl is used. (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 (n-butyl acrylate) is preferably used in consideration of the compatibility with the tackifier added to the base polymer. It is preferable to use -99weight%, More preferably, it is 65-99weight%.

  Further, the above (meth) acrylic polymer may be appropriately copolymerized with another copolymerizable monomer (monomer component). Examples of the copolymerizable monomer include derivatives such as methyl (meth) acrylate, vinyl acetate, acrylamide, dimethylaminomethylacrylamide, acryloylmorpholine, and glycidyl acrylate.

  In addition, 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 using the said carboxyl group-containing monomer, Preferably it is 0.1 to 5 weight%, More preferably, 0.2 to 3 weight% is copolymerized. 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.

  For the purpose of adjusting the refractive index of the (meth) acrylic polymer in the present invention, increasing the internal cohesive force, and increasing the heat resistance, modification treatment can be performed using the above monomer.

  As the modification treatment, in the presence of 100 parts by weight of the obtained (meth) acrylic polymer, 10 to 200 parts by weight of monomer (monomer component) having a composition different from that of the (meth) acrylic polymer is used, preferably 10 to 100 parts by weight. By adding parts by weight, a graft polymerization reaction can be performed.

  The weight average molecular weight of the (meth) acrylic polymer is usually preferably 600,000 or more, 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.

  In addition, as a polymerization method for performing the above modification treatment, for example, 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, peroxidation is performed. The product can be added 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 solid content to the aqueous dispersion of the (meth) acrylic polymer, add the necessary monomers, and replace with nitrogen while stirring. After allowing the particles to absorb the monomer, a water-soluble aqueous peroxide solution is added, and the reaction is terminated by heating at 50 to 80 ° C. for 4 to 15 hours.

  Thus, by polymerizing a monomer in the presence of a (meth) acrylic polymer, a homopolymer of this monomer is also produced, but by graft polymerization to a (meth) acrylic polymer, other homopolymers are also produced. It will be in the state in which the polymer which consists of exists uniformly in an acrylic type 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 pressure-sensitive adhesive composition (pressure-sensitive adhesive layer), a tackifier (tackifier) is used.

  As the tackifier used in the present invention, a tackifier having an aromatic ring, preferably having a refractive index in the range of 1.51 to 1.75, more preferably 1.53 to 1.70 is used. The In addition, since the colored tackifier is unpreferable in order to color an adhesive, it is a preferable aspect to use a colorless and transparent tackifier.

  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. When the weight average molecular weight exceeds 3000, or when the softening point exceeds 90 ° C., the compatibility with the acrylic polymer may decrease. When the weight average molecular weight is less than 1000, the cohesive force of the pressure-sensitive adhesive May decrease.

  As a measure of the transparency of the tackifier, 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, hydrogenated terpene phenol And hydrogenated products of rosin and its derivatives. 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 tackifier is used in an amount of 10 to 150 parts by weight, preferably 20 to 100 parts by weight, more preferably 30 to 100 parts by weight based on 100 parts by weight of the (meth) acrylic polymer solid content. Adjusted to 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.

  The amount of the cross-linking 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. Preferably it is used in the range of 0.05 to 0.6 parts by weight. 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, so it is blocked. An isocyanate-based crosslinking agent prepared 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 02-2 weight part, and it is more preferable to contain 0.05-1 weight part. If it is less than 0.02 parts by weight, the crosslinking reaction may be insufficient and the cohesive force may be insufficient. On the other hand, if it 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 transparent particles in the present invention are used for imparting a light scattering function. Examples of the transparent particles include organic particles such as a crosslinked acrylic resin, a crosslinked styrene resin, a crosslinked urethane resin, a melamine resin, a benzoguanamine resin, an epoxy resin, and a silicone resin, and transparent fine particles made of an inorganic compound such as silica.

  Specific examples of the transparent particles include a benzoguanamine / formaldehyde condensate (Epester M30, refractive index 1.66), a melamine / formaldehyde condensate (Epester, refractive index 1.66), and a polymethyl methacrylate-based crosslink (Eposter MX, refractive index 1.49), cross-linked polymethyl methacrylate (Techpolymer MBX, refractive index 1.49) manufactured by Sekisui Kasei, cross-linked polystyrene (Techpolymer SBX, refractive index 1.59), manufactured by Toshiba Silicone Silicone resin (Tospearl, refractive index 1.43), Toray Epoxy resin (Trepearl, refractive index 1.59), and the like.

  The average particle diameter of the transparent particles is preferably 0.1 to 30 μm, more preferably 0.2 to 20 μm, and particularly preferably 0.5 to 10 μm. If it is less than 0.1 μm, the light scattering effect is reduced, and if it exceeds 30 μm, the adhesiveness is adversely affected. In addition, since the average particle diameter of a transparent particle becomes larger at the time of adhesion | attachment when it is larger than the thickness of an adhesive layer, it is a preferable aspect to use a small transparent particle.

  The blended amount of the transparent particles is preferably 1 to 70 parts by weight, more preferably 3 to 60 parts by weight with respect to 100 parts by weight of the solid content of the (meth) acrylic pressure-sensitive adhesive composition. Preferably it is 5-55 weight part. If the amount is less than 1 part by weight, the light scattering effect is reduced, and if it exceeds 70 parts by weight, the adhesiveness is remarkably lowered.

  The refractive index of the transparent particles is larger than the refractive index of the light scattering pressure-sensitive adhesive layer of the present invention, and the refractive index difference between the refractive index of the transparent particles and the refractive index of the pressure-sensitive adhesive layer is 0.01 or more. Is more preferably 0.03 to 0.5, and particularly preferably 0.05 to 0.3. If it is less than 0.01, the light scattering effect is not sufficient, and if the difference in refractive index is too large, the total light transmittance is lowered, which is not preferable.

The haze value of the light-scattering pressure-sensitive adhesive composition (pressure-sensitive adhesive layer) containing the transparent particles is 20 to 90%, preferably 25 to 90%, and more preferably 40 to 90%. If the haze value is less than 20%, the light diffusing function is insufficient, and if it exceeds 90%, the transmittance decreases, which is not preferable. The haze value is calculated by the following equation using the diffuse transmittance (Hd) and the total light transmittance (Ht).
Haze value (%) = (Hd / Ht) × 100

  The refractive index of the light scattering pressure-sensitive adhesive layer of the present invention is preferably 1.50 or more, more preferably 1.50 to 1.62. If it is less than 1.50, the refractive index difference with an optical member (for example, glass, polycarbonate, etc.) becomes large, and reflection of light at the interface between the optical member and the pressure-sensitive adhesive layer increases, which is not preferable.

  The pressure-sensitive adhesive composition obtained by blending the above-mentioned (meth) acrylic polymer with the above-mentioned crosslinking agent is preferably coated and dried on a support, and the gel fraction of the pressure-sensitive adhesive after crosslinking is preferably 20 to 90% by weight. Is crosslinked to 30 to 85% by weight. If the gel fraction is too small, the cohesive force is inferior, and if it is too large, the adhesiveness is inferior.

  By setting the gel fraction of the pressure-sensitive adhesive after cross-linking to the above range, even when moisture or residual monomer is generated from the acrylic plate when bonded to an acrylic plate, the adhesion between the acrylic plate and the pressure-sensitive adhesive The foaming phenomenon at the interface can be suppressed. The gel fraction of the pressure-sensitive adhesive ((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. , Shows the amount of crosslinked polymer relative to the initial adhesive, modified in the amount of tackifier. 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.

  Furthermore, when the pressure-sensitive adhesive composition comprising this (meth) acrylic polymer is applied to a hydrophilic adherend such as glass, a silane coupling agent can be used to increase the water resistance at the interface.

  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 part by weight, the durability improving effect may be inferior, whereas if it exceeds 2 parts by weight, the adhesive force to the liquid crystal cell or the like may be excessively increased and the removability may be inferior.

  The pressure-sensitive adhesive composition may contain other known additives, for example, powders such as vulcanizing agents, colorants, pigments, dyes, surfactants, plasticizers, surface lubricants, Depending on the use of 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 as appropriate. Moreover, you may employ | adopt the redox system which added a reducing agent within the controllable range.

  The pressure-sensitive adhesive composition is coated, dried and crosslinked on various supports, particularly optical sheets (optical films), to obtain a light-scattering pressure-sensitive adhesive sheet. It is also usually carried out by applying and drying on a peeled support and transferring it to various optical sheets.

  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 100 μm, preferably 5 to 80 μm. The

  In the light scattering adhesive sheet of the present invention, the light scattering adhesive layer in the backlight system is formed on one side of a support, particularly an optical sheet (optical film). Since the light-scattering pressure-sensitive adhesive sheet of the present invention includes the pressure-sensitive adhesive layer that exhibits the above-described effects, the light-scattering pressure-sensitive adhesive sheet can exhibit an effect of efficiently emitting light without confining light from the light source.

  Such a light scattering pressure-sensitive adhesive sheet of the present invention is used by being attached to an adherend to which light is irradiated from below. Also, the refractive index of the pressure-sensitive adhesive layer is higher than the refractive index of the surface of the adherend from which light comes out, and the refractive index of the optical sheet (optical film) is higher than the refractive index of the pressure-sensitive adhesive layer. Thus, since there is no reflection between the respective layers, there is no loss of emitted light, and light can be emitted efficiently, which is a preferable mode.

  The backlight system of the present invention is preferably formed by bonding an adherend to which light is irradiated, an optical sheet (optical film), and a light-scattering adhesive sheet composed of an adhesive layer.

  Examples of the adherend include a light source, a light guide, and a light source unit.

  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 a method of attaching an optical sheet (optical film) directly to these light sources via an adhesive layer is possible, a structure incorporating these light sources, such as a liquid crystal television having a glass plate or acrylic plate on the surface, A glass substrate such as a backlight of a monitor, a light guide plate using an LED as a light source, or an organic EL light emitter is used. By affixing the light scattering adhesive sheet of the present invention directly to such a light source, the effect of being able to emit efficiently without confining the light from the light source inside can be exhibited.

  Moreover, even when there are fine irregularities on the surface of the light source and light is lost, the light can be efficiently emitted by applying the light scattering adhesive sheet of the present invention. This is considered to be due to the softness of the pressure-sensitive adhesive, and the effect that the pressure-sensitive adhesive enters such uneven portions, eliminates the air layer from being caught 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.

  Usually, when a diffusion plate or the like is provided on a backlight, an optical member (an optical sheet, an optical film, or the like) is simply placed on the backlight, and the refractive index is 1 between the backlight and the optical member. Light loss occurred due to the presence of a thin air layer of 0.0, but this loss was reduced by providing a light scattering adhesive sheet, and in particular, the refraction of the surface of the backlight as the adherend By providing the pressure-sensitive adhesive layer having a refractive index higher than the refractive index, it is assumed that light loss is almost eliminated and light can be emitted efficiently.

  Specific examples of the optical member include a microlens, a light diffusing plate, and a prism sheet. Among these, a microlens and / or a light diffusing plate are preferable.

  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.

  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.

  Specific materials for the optical sheet (optical film) can be used as long as they are transparent, and examples thereof include acrylic resins, polyester resins, epoxy resins, polystyrene resins, polycarbonate resins, and the like.

  The optical sheet (optical film) may be a laminate of a plurality of layers of optical sheets (optical film). Here, as a method of laminating the laminated optical sheet (optical film), it may be simply stacked, but by using the light scattering pressure-sensitive adhesive sheet using the light scattering pressure-sensitive adhesive layer of the present invention, more light is transmitted to the liquid crystal module. It is possible to guide efficiently.

  As the optical member (optical sheet, optical film, etc.), those used for forming an image display device such as a liquid crystal display device are used, and the type thereof is not particularly 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 in the 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 member (optical sheet, optical film, etc.) used in the present invention includes, for example, a reflecting plate, a semi-transmissive plate, a retardation plate (including wavelength plates such as 1/2 and 1/4), and a viewing angle compensation film. And an optical layer that may be used for forming a liquid crystal display device such as a brightness enhancement film. 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 member (such as an optical sheet or an optical film) obtained by laminating the optical layer 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. What was made into the member is excellent in the stability of quality, assembly work, etc., and has the advantage that the manufacturing process of a liquid crystal display device etc. can be improved. 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 retardation characteristics.

  In addition, each layer such as an optical member (such as an optical sheet or an optical film) or an adhesive layer includes, for example, a salicylic acid ester compound, a benzophenol compound, a benzotriazole compound, a cyanoacrylate compound, a nickel complex compound, and the like. What gave the ultraviolet absorptivity by systems, such as a system processed with a ultraviolet absorber, etc. may be used.

  The light scattering pressure-sensitive adhesive sheet 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. In other words, a liquid crystal display device can be generally formed by appropriately assembling components such as a liquid crystal module such as a liquid crystal cell, the light scattering adhesive sheet, and an illumination system as necessary, and incorporating a drive circuit. However, there is no particular limitation, and it can be based on the conventional method. 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 the light scattering adhesive sheet is disposed on one side or both sides of a liquid crystal cell, or a backlight or a reflecting plate used in an illumination system can be formed. In that case, an optical member (such as an optical sheet or an optical film) can be placed on one side of the 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.

  Such an optical member (such as an optical sheet or an optical film) is subjected to easy attachment treatment such as corona treatment or plasma treatment or undercoating treatment on the surface of the optical member in order to improve the anchoring force when bonded to the adhesive layer. You may go.

  In addition, an image display device and a lighting device can be manufactured using the backlight system of the present invention. By using the backlight system, it becomes possible to emit light efficiently, and further contribute to energy saving and long life.

  On the other hand, the backlight system of the present invention is characterized in that an adherend from which light is emitted and a support, particularly an optical member (such as an optical sheet or an optical film), are bonded via an adhesive layer. Is. The pressure-sensitive adhesive layer may be a single layer, or two or more layers may be laminated and used.

  In addition to the transparent particles, as the pressure-sensitive adhesive composition (pressure-sensitive adhesive layer), for example, alumina, titania, zirconia, tin oxide, indium oxide, cadmium oxide, It is also possible to blend inorganic particles that may be conductive such as antimony oxide, organic particles composed of various crosslinked or uncrosslinked polymers, and the like.

  It is a preferable embodiment to form a diffusion pressure-sensitive adhesive layer having a light diffusivity of 10% or less by containing the inorganic 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 inorganic 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. . Further, when the refractive index of the inorganic particles and the like 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 ¹ −n ² | <0.1, preferably | n ¹ −n ² | <0.09, particularly a combination satisfying −0.08 <n ¹ −n ² <−0.01 preferable.

  The amount of the light-transmitting inorganic 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 the inorganic particles are used per 100 parts by weight of the pressure-sensitive adhesive composition (solid content).

  As described above, the fine particles are dispersed in the pressure-sensitive adhesive composition (pressure-sensitive adhesive layer), or when the modified acrylic copolymer is modified, the haze is manifested by the formation of a domain by the polymer of the added monomer. A design having a diffusion function is also possible, and a light dispersion effect can be obtained.

  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, 99.0 parts by weight of butyl acrylate, 1.0 part by weight of 4-hydroxybutyl acrylate, Then, 0.1 part by weight of 2,2′-azobisisobutyronitrile was 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 940,000 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-160N), 0.3 part by weight, 3-glycidoxypropyltrimethoxysilane 0.1 part by weight was added, and further 15 parts by weight of ethyl acetate 30 parts by weight of melamine formaldehyde condensate (refractive index: 1.66, average particle size: 1-2 μm, manufactured by Nippon Shokubai Co., Ltd., Eposta S12) as transparent particles A lightly dispersed pressure-sensitive adhesive composition of the present invention was obtained by adding the material uniformly dispersed in the composition.

  The 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 crosslinked at 120 ° C. for 3 minutes, and (meth) acrylic polymer gel A light scattering pressure-sensitive adhesive layer having a fraction of 66% by weight was obtained. In addition, the refractive index of the adhesive layer when not blending transparent particles was 1.50.

[Example 2]
30 parts by weight of styrene and 0.15 parts by weight of benzoyl peroxide as a polymerization initiator are added to 100 parts by weight of the solid content of the (meth) acrylic polymer of Example 1, and nitrogen substitution is performed at 60 ° C. The graft polymerization reaction was carried out for 5 hours and further at 70 ° C. for 8 hours to obtain a solution of a modified (meth) acrylic polymer. The refractive index of this modified (meth) acrylic polymer was 1.47.

  Copolymer of α-methylstyrene and styrene as a tackifier (softening point: 82-88 ° C., weight average molecular weight: 1200, refractive index: 1.61) to 100 parts by weight of the solid content of the modified (meth) acrylic polymer. 80 parts by weight, manufactured by Eastman Chemical Co., Ltd., Crystal Rex 3085), and 0.5 parts by weight of tolylene diisocyanate adduct of trimethylolpropane (Nihon Polyurethane Co., Ltd., Coronate L), 3-glycidoxypropyl 0.1 parts by weight of trimethoxysilane was added, and further 15 parts by weight of benzoguanamine formaldehyde condensate (refractive index: 1.66, average particle size: 2.5 to 4 μm, manufactured by Nippon Shokubai Co., Ltd., Eposter M30) as transparent particles. What was uniformly dispersed in 30 parts by weight of ethyl acetate was added to obtain the light scattering 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 had a dry thickness of 15 μm, dried and crosslinked at 120 ° C. for 3 minutes, and (meth) acrylic polymer gel A light scattering pressure-sensitive adhesive layer having a fraction of 71% by weight was obtained. In addition, the refractive index of the adhesive layer when not blending transparent particles was 1.53.

Example 3
A styrene oligomer (softening point: 82-85 ° C., weight average molecular weight: 1380, refractive index: 1.60, Yasuhara Chemical Co., Ltd.) as a tackifier with respect to 100 parts by weight of the solid content of the modified (meth) acrylic polymer of Example 2 The light scattering pressure-sensitive adhesive layer having a gel fraction of (meth) acrylic polymer of 60% by weight was obtained in the same manner as in Example 2 except that 40 parts by weight was manufactured. In addition, the refractive index of the adhesive layer when not blending transparent particles was 1.51.

Example 4
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, 98.5 parts by weight of butyl acrylate, 0.5 parts by weight of acrylic acid, 4-hydroxy acrylate After adding 1.0 part by weight of butyl and 0.1 part by weight of 2,2′-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 1,120,000 was obtained.

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

  A styrene oligomer (softening point: 82-85 ° C., weight average molecular weight: 1380, refractive index: 1.60, manufactured by Yashara Chemical Co., SX) as a tackifier with respect to 100 parts by weight of the solid content of the modified (meth) acrylic polymer. -85) 80 parts by weight are added, and further, 0.5 parts by weight of tolylene diisocyanate adduct of trimethylolpropane (manufactured by Nippon Polyurethane Co., Ltd., Coronate L), 0.1 parts by weight of 3-glycidoxypropyltrimethoxysilane Furthermore, 20 parts by weight of melamine formaldehyde condensate (refractive index: 1.66, average particle size: 1 to 2 μm, manufactured by Nippon Shokubai Co., Ltd., Eposter S12) is dispersed uniformly in 40 parts by weight of ethyl acetate as transparent particles. Was added to obtain a light scattering 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 had a dry thickness of 15 μm, dried and crosslinked at 120 ° C. for 3 minutes, and (meth) acrylic polymer gel A light scattering pressure-sensitive adhesive layer having a fraction of 54% by weight was obtained. In addition, the refractive index of the adhesive layer when not blending transparent particles was 1.53.

Example 5
A light scattering pressure-sensitive adhesive layer having a gel fraction of (meth) acrylic polymer of 50% by weight was obtained in the same manner as in Example 4 except that the addition amount of the transparent particles was changed to 30 parts by weight.

Example 6
A light scattering pressure-sensitive adhesive layer having a gel fraction of (meth) acrylic polymer of 47% by weight was obtained in the same manner as in Example 4 except that the addition amount of the transparent particles was 50 parts by weight.

Example 7
30 parts by weight of benzyl acrylate and 1.5 parts by weight of 4-hydroxybutyl acrylate, and 0.15 parts by weight of benzoyl peroxide as a polymerization initiator with respect to 100 parts by weight of the solid content of the (meth) acrylic polymer of Example 1 Was added, and a graft polymerization reaction was carried out at 60 ° C. for 5 hours and further at 70 ° C. for 8 hours to obtain a modified (meth) acrylic polymer solution. The refractive index of this modified (meth) acrylic polymer was 1.48.

  A styrene oligomer (softening point: 82-85 ° C., weight average molecular weight: 1380, refractive index: 1.60, manufactured by Yashara Chemical Co., SX) as a tackifier with respect to 100 parts by weight of the solid content of the modified (meth) acrylic polymer. -85) 40 parts by weight were added, and further, xylylene diisocyanate adduct of trimethylolpropane (manufactured by Mitsui Chemicals Polyurethanes, Takenate D-110N) 0.5 part by weight, 3-glycidoxypropyltrimethoxysilane. 1 part by weight is added, and further 15 parts by weight of ethyl acetate is added to 15 parts by weight of benzoguanamine formaldehyde condensate (refractive index: 1.66, average particle size: 2.5 to 4 μm, manufactured by Nippon Shokubai Co., Ltd., Eposta M30) as transparent particles. A lightly dispersed pressure-sensitive adhesive composition of the present invention was obtained by adding the material uniformly dispersed in the composition.

  The 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 crosslinked at 120 ° C. for 3 minutes, and (meth) acrylic polymer gel A light scattering pressure-sensitive adhesive layer having a fraction of 70% by weight was obtained. In addition, the refractive index of the adhesive layer when not blending transparent particles was 1.52.

[Comparative Example 1]
A pressure-sensitive adhesive layer having a (meth) acrylic polymer gel fraction of 72% by weight was obtained in the same manner as in Example 1 except that no tackifier was added. In addition, the refractive index of the adhesive layer when not blending transparent particles was 1.46.

  The following evaluation was performed about the adhesive layer 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 with respect to 100 parts by weight of the pressure-sensitive adhesive polymer ((meth) acrylic polymer) when the pressure-sensitive adhesive is blended is A, and the weight part of the transparent particles is B,
Gel fraction (% by weight) = (W ₂ / W ₁ ) × (100 + A + B) −B
As calculated. In this example and comparative example, it was confirmed that the tackifier was not dissolved in the crosslinked structure of the polymer and was completely dissolved in the state immersed in ethyl acetate, but the transparent particles were not dissolved.

<Measurement of adhesive strength>
A polyester film (Luminer S-10, manufactured by Toray Industries, Inc.) is used as a backing to the light scattering adhesive layer (width 25 mm) obtained in Examples and Comparative Examples. Stuck. 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 and the value was defined as the adhesive strength before heating (N / 20 mm).

  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-M2).

<Measurement of haze>
Under an atmosphere of 25 ° C., measurement was performed according to JIS K-7136 using a D-56 light with a reflection / transmittance meter (manufactured by Murakami Color Research Laboratory, model HR-100).

<Measurement of brightness>
The pressure-sensitive adhesive layer is pasted on a light guide plate (polymethyl methacrylate, refractive index 1.49) of a backlight of a 17-inch color display (SyncMaster 712N) manufactured by Samsung Electronics Co., and polyester (refractive index 1) .50, thickness 25 μm) The surface of the polyester layer coated with a polystyrene layer (refractive index 1.59, thickness 5 μm) and processed into a hemisphere with a radius of 5 μm by hot pressing at 160 ° C. This was pasted to make the configuration of a backlight system (light source). 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 The luminance (cd / cm ² ) was measured in a dark room by aligning a luminance meter at the center of the light source shielded from light. The luminance in the initial configuration without attaching an adhesive layer or the like was set to 100, and the luminance in the examples and comparative examples was evaluated as relative values.

<Measurement of storage modulus>
The storage modulus 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.

  From Table 1, it has confirmed that it was excellent in all the characteristics in all the Examples. On the other hand, in Comparative Example 1, it was confirmed that the adhesive strength was inferior both before and after heating, and the luminance was inferior to that of the Example.

Claims (10)

10 to 150 parts by weight of a tackifier having an aromatic ring and 100 to 2 parts of a crosslinking agent 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. to contain parts (meth) acrylic pressure-sensitive adhesive composition, containing transparent particles, a light scattering adhesive layer haze value is from 20% to 90% der Ru light scattering adhesive composition,
The refractive index of the transparent particles is larger than the refractive index of the pressure-sensitive adhesive layer, and the refractive index difference between the refractive index of the transparent particles and the refractive index of the pressure-sensitive adhesive layer is 0.01 or more. Light scattering adhesive layer. The light-scattering pressure-sensitive adhesive layer according to claim 1, wherein the (meth) acrylic polymer is a (meth) acrylic polymer obtained by further copolymerizing a high refractive index monomer. The light scattering pressure-sensitive adhesive layer according to claim 1, wherein the transparent particle is contained in an amount of 1 to 70 parts by weight with respect to 100 parts by weight of the (meth) acrylic pressure-sensitive adhesive composition. The average particle diameter of the said transparent particle is 0.1-30 micrometers, The light-scattering adhesive layer in any one of Claims 1-3 characterized by the above-mentioned. The said (meth) acrylic-type adhesive composition contains 0.01-2 weight part of silane coupling agents with respect to 100 weight part of said (meth) acrylic-type polymers, The characterized by the above-mentioned. The light-scattering adhesive layer in any one. The light according to any one of claims 1 to 5, wherein the (meth) acrylic polymer is a (meth) acrylic polymer obtained by copolymerizing 50 to 99% by weight of n-butyl acrylate. Scattering adhesive layer . Refractive index is 1.50 or more, The light-scattering adhesive layer in any one of Claims 1-6 characterized by the above-mentioned. Light scattering adhesive layer according to any one of claims 1 to 7, the storage modulus at 23 ° C. is characterized in that it is a 10,000～1,000,000Pa. A light scattering pressure-sensitive adhesive sheet comprising the pressure-sensitive adhesive layer according to any one of claims 1 to 8 formed on a support, wherein the pressure-sensitive adhesive layer has a thickness of 2 to 100 µm. Scattering adhesive sheet. A backlight system comprising a light scattering adhesive sheet according to claim 9 formed on an adherend to which light is irradiated.