JP2010039170A - Optical film with pressure-sensitive adhesive, laminated optical member, and image display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical film capable of reducing dispersion, and capable of preventing a contrast from getting low, even when mounted on an image display formed highly precisely with 50 μm or less of pixel pitch. <P>SOLUTION: The optical film 12 with a pressure-sensitive adhesive is laminated with the optical film such as a polarizing film 11 and the pressure-sensitive adhesive 6, the pressure-sensitive adhesive 6 contains a pressure-sensitive adhesive resin containing an acrylic polymer as a main component, and fine particles comprising an acrylic resin having 0.1-4 μm of average particle size, and having a refractive index difference to a polymer constituting the pressure-sensitive adhesive resin within a range of 0.01-0.05, and the fine particles exist at a ratio of 10-40 pts.wt. per 100 pts.wt. of the pressure-sensitive adhesive resin, in the optical film with the pressure-sensitive adhesive. Other optical layer is laminated onto the optical film with the pressure-sensitive adhesive, to form a laminated optical member, and the optical film with the pressure-sensitive adhesive is combined with image display elements such as liquid crystal cells, to constitute the image display. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an optical film with a pressure sensitive adhesive. The present invention also relates to a laminated optical member obtained by laminating the optical film with pressure-sensitive adhesive on another optical layer, and an image display device provided with the optical film with pressure-sensitive adhesive or laminated optical member. . The image display device targeted by the present invention includes a liquid crystal display device and an organic electroluminescence (organic EL) display device.

  Conventionally, liquid crystal display devices have been used in desktop calculators, electronic timepieces, and the like, but their use has been rapidly expanding in recent years. That is, liquid crystal display devices have been used from mobile devices such as mobile phones to large televisions regardless of screen size. In addition to liquid crystal display devices, organic EL display devices have also been increasingly used mainly for mobile applications. As the applications of these image display devices are expanded, performance suitable for each application is required. For example, in an image display device for mobile use such as a mobile phone, high definition and high contrast of pixels are achieved in order to provide good visibility even on a small screen.

  Similarly, good visibility is demanded for polarizing films widely used in image display devices. In general, a polarizing film is used in a state where a transparent protective film is laminated on one or both sides of a polarizer made of polyvinyl alcohol to which a dichroic dye is adsorbed and oriented via a transparent adhesive. For example, in a liquid crystal display device using a polarizing film, in the transmissive type, unevenness due to shadows and pixels of the backlight occurs, and in the semi-transmissive type, light interference occurs due to unevenness on the surface of the reflecting plate. Bleeding and blurring may occur, preventing good visibility. In order to improve this, a light diffusion layer made of a transparent resin mixed with fine particles has been arranged.

  On the other hand, in an image display device including a liquid crystal display device, in order to display a finer image, higher definition of a pixel which is a minimum component of the image is progressing. For example, in the case of a small-sized image display device having a display screen having a diagonal size of 3.5 inches (about 9 cm), in addition to the conventional 200,000 pixels, those having more than 800,000 pixels are being developed.

  FIG. 1 is a plan view schematically showing the relationship between individual pixels that display the three primary colors red (R), green (G), and blue (B) and the pixel pitch in the color image display device. Red (R), green (G), and blue (B) pixels 1R, 1G, 1B (also referred to as sub-pixels) are arranged one by one to constitute a set of pixels. Each of the pixels 1R, 1G, and 1B has a rectangular shape in plan view, each of which has a short side length a that is approximately ３ of the long side length b, and a set of three primary color sub-pixels arranged in a row. This pixel has a substantially square planar shape. The smallest a among the vertical and horizontal dimensions a and b of each sub-pixel is called a pixel pitch. Note that when referring to the number of pixels, a set of pixels in which sub-pixels of the three primary colors are arranged is counted as one pixel. In an image display device having a diagonal size of 3.5 inches and approximately 200,000 pixels, the pixel pitch a indicating the distance between adjacent sub-pixels is approximately 60 μm. However, in an image display device having the same size and approximately 800,000 pixels. The pixel pitch a is approximately 25 μm.

  In addition, an antiglare layer having surface irregularities is generally provided on the outermost surface on the viewing side of the image display device in order to prevent reflection of external light and glare. As a result, the unevenness of the antiglare layer interferes with the repetition of the pixels, and the display screen may be glaring. Japanese Patent Application Laid-Open No. 2000-314875 (Patent Document 1) discloses a liquid crystal display device including a liquid crystal cell having a pixel pitch of 75 μm or less and an antiglare layer having unevenness provided on the outermost surface. A technique for preventing such glare by disposing a light diffusion layer having a specific internal haze on the side is disclosed. However, even when a light diffusion layer as disclosed in this document is provided, the pixel pattern of the image display element and the scattered light of the light diffusion layer interfere with each other as the image display device is further refined. As a result, the problem that glare occurs and the sharpness of the image decreases has become apparent. In order to eliminate this, for example, if the addition amount of fine particles in the light diffusion layer is increased and the diffusion of light is increased, glare is suppressed, but since the polarization is eliminated by diffusion, the black luminance increases, As a result, there arises a problem that the contrast is lowered.

  On the other hand, Japanese Patent Laid-Open No. 2000-338309 (Patent Document 2) has an antiglare layer having unevenness on the outermost surface, and an average of unevenness constituting the antiglare layer in an image display device having a pixel pitch of 70 μm or less There has been disclosed a technique for preventing the above-described glare by making the interval and the pixel pitch satisfy a specific relationship. Even if this technology is adopted, glare prevention and contrast are still insufficient in an image display device with higher pixel definition and higher definition.

JP 2000-314875 A JP 2000-338309 A

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an optical film that has little glare and does not reduce contrast even when mounted on an image display device with a pixel pitch of 50 μm or less and further refined. As a result of intensive studies, the present inventor has found that an optical film provided with a pressure-sensitive adhesive containing a light diffusing agent as a light diffusing layer has a glare even when mounted on an image display device having a pixel pitch of about 30 μm. As a result, the inventors have found that the contrast is small and the contrast is small, and have reached the present invention.

  That is, the present invention is an optical film with a pressure-sensitive adhesive in which an optical film and a pressure-sensitive adhesive layer are laminated, and the pressure-sensitive adhesive layer includes an adhesive resin having an acrylic polymer as a main component, an average Containing fine particles made of an acrylic resin having a particle size of 0.1 to 4 μm and a refractive index difference of 0.01 to 0.05 with respect to the polymer constituting the adhesive resin. The present invention provides an optical film with a pressure-sensitive adhesive that exists at a ratio of 10 to 40 parts by weight per 100 parts by weight of an adhesive resin.

  In this optical film with a pressure-sensitive adhesive, the pressure-sensitive adhesive layer preferably has a haze in the range of 20 to 80%. The pressure-sensitive adhesive layer preferably has a transparency of 90% or more. Further, this pressure-sensitive adhesive layer preferably has a thickness in the range of 1 to 40 μm. The optical film with a pressure-sensitive adhesive generally includes one or both of a polarizing film and a retardation film.

  The present invention also provides a laminated optical member comprising a laminate of the above-mentioned optical film with a pressure-sensitive adhesive and an optical layer exhibiting another optical function.

  The present invention further provides an image display device comprising the above optical film or laminated optical member with a pressure-sensitive adhesive and an image display element, and the image display element has a pixel pitch in the range of 10 to 50 μm.

  The optical film with a pressure-sensitive adhesive of the present invention gives good visibility when mounted on an image display device. Specifically, by sticking the optical film with a pressure-sensitive adhesive of the present invention to an image display element having a pixel pitch of 10 to 50 μm, an image display having good visibility that satisfies all the following four items: A device is obtained.

(1) The display image does not blur or blur.
(2) No glare occurs.
(3) Contrast does not decrease.
(4) Give a fine image.

  Hereinafter, the present invention will be described in detail. In the present invention, an optical film such as a polarizing film or a retardation film and a pressure-sensitive adhesive layer are laminated to obtain an optical film with a pressure-sensitive adhesive. This pressure-sensitive adhesive layer has a refractive index difference between an adhesive resin mainly composed of an acrylic polymer and an average particle diameter of 0.1 to 4 μm and a polymer constituting the adhesive resin. And fine particles made of an acrylic resin in the range of 0.05. The fine particles are blended at a ratio of 10 to 40 parts by weight per 100 parts by weight of the above-mentioned adhesive resin. By blending the fine particles, the pressure-sensitive adhesive layer also functions as a light diffusion layer. Then, by forming a pressure sensitive adhesive layer containing a predetermined amount of fine particles made of a specific resin having a refractive index difference with a polymer constituting the adhesive resin in a predetermined range, the pixel pitch is 50 μm or less. Even when applied to a certain high-definition image display device, blurring and blurring are hardly generated in the display image, glare is hardly generated, contrast is not easily lowered, and good visibility is obtained.

[Pressure sensitive adhesive]
In the present invention, the pressure-sensitive adhesive layer is composed of an adhesive resin containing fine particles made of an acrylic resin as a light diffusing agent.

[Adhesive resin]
The adhesive resin is mainly composed of an acrylic polymer. Although it does not specifically limit as an acryl-type polymer, For example, (meth) acrylic acid butyl, (meth) acrylic acid ethyl, (meth) acrylic acid isooctyl, (meth) acrylic acid 2-ethylhexyl (meth) ) Acrylic ester base polymer and a copolymer base polymer using two or more of these (meth) acrylic esters are preferably used. These base polymers are copolymerized with polar monomers. Examples of polar monomers include (meth) acrylic acid, 2-hydroxypropyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, (meth) acrylamide, and 2-N, N-dimethylaminoethyl (meth). Examples thereof include monomers having a polar functional group such as a carboxyl group, a hydroxyl group, an amide group, an amino group, and an epoxy group, such as acrylate and glycidyl (meth) acrylate.

  These acrylic polymers can of course be used alone, but a crosslinking agent is usually blended in order to accelerate curing or control curing. As the crosslinking agent, a divalent or polyvalent metal ion that forms a carboxylic acid metal salt with a carboxyl group, a polyamine compound that forms an amide bond with a carboxyl group, Examples thereof include polyepoxy compounds and polyol compounds that form an ester bond with a carboxyl group, and polyisocyanate compounds that form an amide bond with a carboxyl group. Of these, polyisocyanate compounds are widely used as organic crosslinking agents.

  The pressure sensitive adhesive may contain a silane compound in order to improve the adhesion between the pressure sensitive adhesive layer and the glass substrate. Examples of the silane compound include monomer types such as vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris (2-methoxyethoxy) silane, and co-oligomer types such as 3-mercaptopropyltrimethoxysilane-tetramethoxysilane copolymer. Etc.

  In order to form a pressure-sensitive adhesive layer, in addition to the acrylic polymer, cross-linking agent, and silane compound, the adhesive force, cohesive force, viscosity, elastic modulus, glass transition temperature, etc. are adjusted as necessary. For example, appropriate additives such as resins that are natural products or synthetic products, tackifier resins, antioxidants, ultraviolet absorbers, dyes, pigments, antifoaming agents, corrosion inhibitors, photopolymerization initiators, etc. It can also be blended.

[Light diffusing agent (fine particles)]
In the present invention, fine particles comprising an acrylic resin as a light diffusing agent are blended in the adhesive resin having the acrylic polymer as a main component as described above. As the fine particles, those having an average particle diameter in the range of 0.1 to 4 μm are used. The average particle diameter of the fine particles is preferably 1 μm or more, and preferably 3 μm or less. When the average particle size of the fine particles exceeds 4 μm, when added in an amount of 10 to 40 parts by weight per 100 parts by weight of the adhesive resin defined in the present invention, it becomes difficult to uniformly disperse. As a result, the size of the partially agglomerated fine particles approaches the pixel size, so that a luminance distribution occurs between the pixels and glare is likely to occur. On the other hand, when the average particle size of the fine particles is less than 0.1 μm, the scattering efficiency increases, so that the above-described addition amount gives haze more than necessary.

  The fine particles are assumed to have a refractive index difference of 0.01 to 0.05 with respect to the polymer constituting the adhesive resin, that is, the acrylic polymer. When the difference in refractive index from the acrylic polymer is less than 0.01, the internal scattering effect due to the fine particles becomes small. Therefore, in order to eliminate the glare by giving the light diffusion layer predetermined scattering characteristics and haze, a large amount of fine particles It is necessary to add to the adhesive resin, but in that case, the adhesiveness is lowered, which is not preferable. On the other hand, if the difference in refractive index exceeds 0.05, the reflectance at the interface between the adhesive resin and the fine particles increases, so that backscattering increases and the total light transmittance decreases, which is not preferable. Since the acrylic polymer constituting the adhesive resin often shows a refractive index of around 1.50, the fine particles satisfy the above refractive index difference from those having a refractive index of about 1.40 to 1.60. It can be selected as appropriate.

  As resin fine particles for blending in a pressure-sensitive adhesive layer and imparting light diffusibility, for example, the following are known.

Melamine beads (refractive index 1.57),
Polymethyl methacrylate beads (refractive index 1.49),
Methyl methacrylate / styrene copolymer resin beads (refractive index 1.50 to 1.59),
Polycarbonate beads (refractive index 1.55),
Polyethylene beads (refractive index 1.53),
Polystyrene beads (refractive index 1.6),
Silicone resin beads (refractive index 1.43) etc.

  In the present invention, fine particles made of acrylic resin are used in order to make the difference in refractive index from the polymer constituting the adhesive resin in the range of 0.01 to 0.05. Here, the acrylic resin means a polymer having an acrylic ester or methacrylic ester as a main monomer, and a polymer having a methacrylic ester, particularly methyl methacrylate as a main monomer is preferable. The term “main monomer” as used herein generally means that 50% by weight or more, preferably 80% by weight or more, more preferably 90% by weight or more of all monomers is acrylic acid ester or methacrylic acid ester, preferably methacrylic acid. It means an acid ester, more preferably methyl methacrylate. Typically, polymethyl methacrylate, copolymers of methyl methacrylate with up to 10% by weight of other methacrylic acid esters or acrylic esters, copolymers of methyl methacrylate with up to 10% by weight of styrene Etc. Of these, polymethyl methacrylate beads that have a refractive index difference of 0.01 to 0.05 are preferred regardless of the type of adhesive resin.

  The fine particles made of the acrylic resin are preferably substantially spherical, and particularly those having a substantially uniform particle size, that is, a particle size distribution that is substantially monodispersed.

  The blending amount of the fine particles takes into consideration the haze required for the light diffusable pressure-sensitive adhesive layer in which it is blended, the brightness of the image display device to which the optical film having the pressure-sensitive adhesive layer is applied, and the like. Thus, the amount is in the range of 10 to 40 parts by weight per 100 parts by weight of the adhesive resin constituting the pressure-sensitive adhesive layer. Preferably, the above-mentioned fine particles are blended at a rate of 20 parts by weight or more per 100 parts by weight of the pressure-sensitive resin constituting the pressure-sensitive adhesive layer. Here, the pressure-sensitive adhesive layer constituting the pressure-sensitive adhesive layer includes not only the acrylic polymer that is the main component of the pressure-sensitive resin as described above but also a crosslinking agent blended therein, The solid content other than the fine particles constituting the adhesive layer is meant.

[Pressure sensitive adhesive layer]
The pressure-sensitive adhesive layer is formed by mixing a pressure-sensitive adhesive mainly composed of an acrylic polymer described above and fine particles made of an acrylic resin in an organic solvent to form a pressure-sensitive adhesive composition. After coating on the material, it can be formed by a method of drying and removing the organic solvent. As the organic solvent, various solvents such as esters represented by ethyl acetate and butyl acetate and ketones represented by acetone can be used.

  The light diffusable pressure-sensitive adhesive layer in which the fine particles are blended has a haze of 20 to 20 from the viewpoint of ensuring the brightness of the image display device to which the optical film is applied and making the display image less likely to bleed or blur. It is preferable to be in the range of 80%. The haze is a value defined by JIS K 7105 and represented by (diffuse transmittance / total light transmittance) × 100 (%).

Moreover, it is preferable that the light diffusable pressure-sensitive adhesive layer containing fine particles has a transparency of 90% or more from the viewpoint of maintaining the sharpness of the display image. The transparency is preferably 95% or more. Clarity is an index expressed by the BYK-Gardner (Germany) BYK-Gardner that expresses the angle of light scattered at a narrow angle, and enters the transparent sample in the form of a sheet or film from the normal direction. The intensity of the scattered light observed within 2.8 ° (0 ° ± 1.4 °) around the incident direction (normal direction) of the light transmitted through the sample is expressed as I _C 3.2 ° to 4.0 ° centered on the incident direction (normal direction) of light (If the incident direction of light is 0 °, the entire circumference is 1.6 ° to 2.0 °) The intensity of the scattered light observed in the ring-shaped portion of (below) is defined by the following formula (1) as I _R.

If the transparency is close to 100%, the transmitted scattered light becomes a component in almost the same direction as the incident light, meaning that there is almost no scattering even in the included angle range, whereas if the transparency is low, I in the above formula (1). It means that _R is large and scattering is large in the included angle range. The transparency can be measured using “Haze Guard Plus” manufactured by Bic Gardner (sold by Toyo Seiki Seisakusho Co., Ltd. as an import agent in Japan). When the transparency is low, the outline of the image is distorted, and in particular, the sharpness of the display image in an image display device with high definition is affected. In this invention, high transparency is maintained, providing a haze by mix | blending microparticles | fine-particles with a pressure sensitive adhesive layer.

  Furthermore, the thickness of the light diffusable pressure-sensitive adhesive layer in which the fine particles are blended is determined according to the adhesive force and the like, but is usually in the range of 1 to 40 μm. The thickness of the light diffusive pressure-sensitive adhesive layer should be in the range of 3 to 25 μm, maintaining good processability and high durability, and when the image display device is viewed from the front or obliquely. This is preferable from the viewpoint of maintaining the brightness of the image and making the display image less likely to bleed or blur.

[Optical film]
The optical film used for the optical film with a pressure-sensitive adhesive of the present invention is a film having an optical function, and examples thereof include a polarizing film and a retardation film.

  A polarizing film is an optical film having a function of emitting polarized light with respect to incident light such as natural light. The polarizing film absorbs linearly polarized light having a vibrating surface in a certain direction and transmits linearly polarized light having a vibrating surface perpendicular to the polarizing film, and reflects linearly polarized light having a vibrating surface in a certain direction. In addition, there are a reflection type linearly polarized light separating film having a property of transmitting linearly polarized light having a vibration plane orthogonal to it, an elliptically polarizing plate in which a linearly polarizing film and a retardation film described later are laminated. As a preferred specific example of a polarizing film, particularly an absorption linear polarizing film (sometimes called a polarizer or a polarizer film), two colors such as iodine and a dichroic dye are applied to a uniaxially stretched polyvinyl alcohol resin film. And the like, in which the organic dye is adsorbed and oriented.

  A retardation film is an optical film that exhibits optical anisotropy, such as the function of rotating the direction of linearly polarized light, the function of changing linearly polarized light into elliptically or circularly polarized light, and the function of changing elliptically or circularly polarized light into linearly polarized light. have. A retardation film whose in-plane retardation is ¼ of the wavelength λ of visible light is called a λ / 4 plate, and a retardation film whose in-plane retardation is ½ of the wavelength. Is called a λ / 2 plate. The λ / 4 plate has a function of changing the linearly polarized light having the wavelength λ to elliptically polarized light or circularly polarized light and changing the elliptically polarized light to linearly polarized light. For example, a plate having an in-plane retardation of about 90 to 160 nm can be used. The λ / 2 plate has a function of changing the direction of linearly polarized light having a wavelength λ. For example, a plate having an in-plane retardation of about 200 to 300 nm can be used.

  The retardation film can be obtained by stretching a polymer film, for example, polyvinyl alcohol, polycarbonate, polyester, polyarylate, polyimide, polyolefin, cyclic polyolefin, polystyrene, polysulfone, polyethersulfone, polyvinylidene fluoride. / Polymethyl methacrylate, liquid crystal polyester, acetylcellulose, saponified ethylene-vinyl acetate copolymer, polyvinyl chloride, etc. are obtained by stretching about 1.01 to 6 times. Among these, a polymer film obtained by uniaxially stretching or biaxially stretching a polycarbonate film or a cyclic polyolefin film is preferable. Although there exist what is called a uniaxial phase difference film, a wide viewing angle phase difference film, a low photoelasticity phase difference film, etc., it is applicable to all.

  Moreover, the film which expressed optical anisotropy by application | coating and orientation of a liquid crystalline compound, and the film which expressed optical anisotropy by application | coating of an inorganic layered compound can also be used as retardation film. Such retardation films include what are called temperature-compensated retardation films, and films with a twisted orientation of rod-like liquid crystals sold under the trade name “LC film” by Nippon Oil Corporation. Also, a film with a tilted orientation of a rod-shaped liquid crystal sold under the trade name “NH film” by Shin Nippon Oil Co., Ltd., and a disk-shaped liquid crystal sold under the trade name “WV film” by FUJIFILM Corporation. Is a film with a tilt orientation, a fully biaxially oriented film sold under the trade name “VAC film” by Sumitomo Chemical Co., Ltd., and also sold under the trade name “new VAC film” by Sumitomo Chemical Co., Ltd. There are biaxially oriented films.

  Among the optical films described above, the absorptive linearly polarizing film is used in a state where a protective film is attached to one or both sides of a polarizer constituting the polarizer, for example, a polarizer film made of polyvinyl alcohol resin. It is often done. The elliptically polarizing plate described above is a laminate of a linearly polarizing film and a retardation film, and the linearly polarizing film is also in a state where a protective film is attached to one or both sides of the polarizer film. There are many. When forming the pressure-sensitive adhesive layer according to the present invention on such an elliptically polarizing plate, a pressure-sensitive adhesive layer may be formed on the retardation film side, or between the polarizing film and the retardation film. A pressure sensitive adhesive layer may be formed.

  The above-mentioned protective film is a film excellent in transparency, for example, an acetyl cellulose resin typified by triacetyl cellulose or diacetyl cellulose, a methacrylic resin typified by polymethyl methacrylate, a polyester resin, or a polyolefin resin. And a film made of polycarbonate resin, polyether ether ketone resin, polysulfone resin, and the like, and among them, an acetylcellulose-based resin film such as a triacetylcellulose film is preferably used. Moreover, additives, such as an ultraviolet absorber, may be blended with the resin constituting the protective film, if necessary, for the purpose of improving durability. Examples of the ultraviolet absorber include salicylic acid ester compounds, benzophenone compounds, benzotriazole compounds, triazine compounds, cyanoacrylate compounds, nickel complex compounds, and the like.

[Optical film with pressure sensitive adhesive]
The optical film with pressure-sensitive adhesive is, for example, by applying the pressure-sensitive adhesive composition described above on a release film and drying to form a pressure-sensitive adhesive layer. Further, a method of laminating an optical film, on the optical film, the pressure-sensitive adhesive composition described above is applied, dried to form a pressure-sensitive adhesive layer, and a release film is bonded to the pressure-sensitive adhesive surface It can be manufactured by a method of protecting it. Here, as the release film, for example, a film made of various resins such as polyethylene terephthalate, polybutylene terephthalate, polycarbonate, and polyarylate is used as a base material, and a silicone treatment is performed on a bonding surface with the pressure-sensitive adhesive layer of the base material. And the like that have been subjected to a mold release treatment. When sticking an optical film with a pressure-sensitive adhesive to an image display element or another optical film, the release film is peeled off from the optical film with a pressure-sensitive adhesive, and the pressure-sensitive adhesive layer is attached to the image display element or other optical film. What is necessary is just to affix on an optical film.

  FIG. 2 is a schematic cross-sectional view showing an example of the layer structure of the optical film with a pressure-sensitive adhesive of the present invention. In the example shown in FIG. 2, the protective films 3 and 3 are bonded to both sides of the polarizer 2 to form the polarizing film 11, and the pressure-sensitive adhesive layer 6 is provided on the opposite side of the protective film 3 from the polarizer 2. The polarizing film 12 with a pressure sensitive adhesive is laminated. Usually, a release film 10 for temporarily protecting the surface of the pressure-sensitive adhesive layer 6 is provided.

  FIG. 3: is a cross-sectional schematic diagram which shows another example of a layer structure about the optical film with a pressure sensitive adhesive of this invention. In the example shown in FIG. 3, the protective film 3 is laminated on one side of the polarizer 2 to form the polarizing film 11, and the pressure sensitive adhesive layer 6 is laminated on the other side of the polarizer 2, so that the pressure sensitive adhesive is used. The attached polarizing film 13 is provided. Also in this example, a release film 10 that temporarily protects the surface of the pressure-sensitive adhesive layer 6 is provided. As in this example, the protective film 3 is disposed only on one side of the polarizer (the protective film on the other side is omitted), thereby further reducing the thickness.

  FIG. 4 is a schematic cross-sectional view showing another example of the layer structure of the optical film with a pressure-sensitive adhesive of the present invention. In the example shown in FIG. 4, a pressure sensitive adhesive layer 6 is laminated on the phase difference film 4 to form a pressure sensitive adhesive-attached phase difference film 14. Also in this example, a release film 10 for temporarily protecting the surface of the pressure-sensitive adhesive layer 6 is provided.

  FIG. 5: is a cross-sectional schematic diagram which shows another example of a layer structure about the optical film with a pressure sensitive adhesive of this invention. In the example shown in FIG. 5, a protective film 3 is laminated on one side of the polarizer 2 to form a polarizing film 11, and a retardation film is provided on the other side of the polarizer 2 via a first pressure-sensitive adhesive layer 7. 4 is laminated, and a second pressure-sensitive adhesive layer 8 is further laminated on the outer side thereof to form an elliptically polarizing plate 15 with a pressure-sensitive adhesive. In this case, the light diffusable pressure-sensitive adhesive layer in which the fine particles are blended is preferably the second pressure-sensitive adhesive layer 8, but may be the first pressure-sensitive adhesive layer 7. On the surface of the second pressure-sensitive adhesive layer 8 located outside the retardation film 4, a release film 10 is usually provided for temporary protection until it is bonded to an image display element or the like. In this example, if the retardation film 4 is composed of a λ / 4 plate and is arranged so that its slow axis intersects the transmission axis of the polarizer 2 at an angle of approximately 45 °, a circularly polarizing plate is obtained.

  FIG. 6 is a schematic cross-sectional view showing another example of the layer structure of the optical film with pressure-sensitive adhesive of the present invention. In the example shown in FIG. 6, a first retardation film 4 and a second retardation film 5 are used, and both are laminated via a third pressure-sensitive adhesive layer 9. That is, in this example, the protective film 3 is laminated on one side of the polarizer 2 to form the polarizing film 11, and the first retardation is provided on the other side of the polarizer 2 via the first pressure-sensitive adhesive layer 7. The film 5 is laminated, the third pressure-sensitive adhesive layer 9 and the second retardation film 4 are laminated in order on the outer side, and the second pressure-sensitive adhesive is placed on the outer side of the second retardation film 4. The layer 8 is laminated to form an elliptically polarizing plate 16 with a pressure sensitive adhesive. Even when three or more retardation films are laminated, each retardation film is preferably bonded via a pressure-sensitive adhesive layer. Also in the example of FIG. 6, a release film 10 for temporary protection is provided on the surface of the second pressure-sensitive adhesive layer 8 located outside the second retardation film 4 in the same manner as in FIG. 5. Yes. In this example, the first retardation film 5 is composed of a λ / 2 plate, and is arranged so that the slow axis thereof intersects the transmission axis of the polarizer 2 at an angle of approximately 15 °. If the film 4 is composed of a λ / 4 plate and the slow axis of the film 4 is arranged so as to intersect with the slow axis of the first retardation film 5 at an angle of approximately 60 °, it can be used as a circularly polarizing plate over a wide wavelength range. It becomes a functional broadband circular polarizer.

[Laminated optical member]
When the optical film with pressure-sensitive adhesive of the present invention is used, one or more optical layers exhibiting other optical functions can be laminated to form a laminated optical member. Examples of other optical layers include surface treatment layers such as hard coat layers, antireflection layers, and antiglare layers, as well as reflection layers, transflective layers, diffusion layers, brightness enhancement films, light collectors, and the like. .

  The hard coat layer is formed to prevent scratches on the surface of the optical film. The hard coat layer is mainly composed of an ultraviolet curable resin such as an acrylic or silicone resin, and adheres to the optical film or hardness. Is excellently selected and can be formed on the surface of the optical film.

  The antireflection layer is formed for the purpose of preventing reflection of external light on the surface of the optical film, and can be formed by a known method such as sputtering of a metal oxide.

  The antiglare layer is formed to prevent deterioration in visibility caused by external light reflected on the surface of the optical film, for example, a roughening method such as a sandblasting method or an embossing method, In general, the surface of the optical film is formed to have a concavo-convex structure by, for example, a method of applying and curing a coating liquid in which transparent fine particles are mixed with an ultraviolet curable resin.

  The reflection layer can be formed by attaching a foil or a vapor deposition film made of a metal such as aluminum on the surface of the optical film. The transflective layer for making a transflective optical film is a method of using the reflective layer as a half mirror, or a reflective plate containing a pearl pigment or the like and exhibiting light transmittance as an optical film. It can be formed by a method of bonding.

  The diffusion layer is an optical member having a function of diffusing incident light, and includes various methods such as a method of performing a mat treatment on an optical film, a method of applying a resin containing fine particles, and a method of adhering a film containing fine particles. Using the method, a diffusion layer having a fine relief structure can be formed on the surface.

  The brightness enhancement film is an optical member having a function of transmitting a part of incident natural light as linearly polarized light or circularly polarized light and reflecting the remaining light for reuse, and is used for the purpose of improving brightness in a liquid crystal display device or the like. It is done. Examples include a reflective linearly polarized light separation film designed to produce anisotropy in reflectance by laminating a plurality of thin film films having different refractive index anisotropies, and an alignment layer of a cholesteric liquid crystal polymer. Examples include a reflective circularly polarized light separating film.

  The light collecting plate is used for the purpose of optical path control, and examples thereof include a prism array sheet, a lens array sheet, and a dot-attached sheet.

  The various optical layers as described above can be directly provided on the surface of the optical film by coating or vapor deposition. Moreover, the optical layer prepared in the form of a film can be integrated with the optical film using an adhesive. Examples of the adhesive include a pressure sensitive adhesive and an energy curable adhesive. The adhesive is not particularly limited, and can be appropriately selected according to the application and purpose, but from the viewpoint of simplicity of bonding work and prevention of optical distortion, a pressure sensitive adhesive is used. It is preferable to do. Examples of pressure sensitive adhesives include acrylic, urethane, silicone, and polyvinyl ether. Above all, like acrylic pressure-sensitive adhesives, it has excellent optical transparency, retains appropriate wettability and cohesion, has excellent adhesion to substrates, and has weather resistance and heat resistance. It is preferable to select and use one that does not cause peeling problems such as floating and peeling under the conditions of heating and humidification.

[Image display device]
The optical film or laminated optical member with pressure-sensitive adhesive of the present invention can be combined with various image display elements to form an image display device, and is applied to a high-definition image display device having a pixel pitch of 10 to 50 μm. Even if it does, it does not cause the glare that was seen when using a conventional optical film with pressure sensitive adhesive, performance such as display blurring prevention, clear image, glare suppression, contrast reduction suppression Will be combined. The image display element to which the optical film with pressure-sensitive adhesive or the laminated optical member of the present invention is applied is not particularly limited, and examples thereof include image display elements used for flat displays such as liquid crystal cells and organic EL display elements. The

  For example, the above-mentioned optical film with a pressure-sensitive adhesive or a laminated optical member can be arranged on one or both sides of a liquid crystal cell to obtain a liquid crystal display device. The liquid crystal cell used is arbitrary, for example, an active matrix drive type represented by each liquid crystal mode of VA (Vertical Alignment), IPS (In-Plane Switching), OCB (Optically Compensated Bend), ECB (Electrically Controlled Birefringence). Liquid crystal display using various liquid crystal cells, such as a simple matrix drive type represented by STN (Super Twisted Nematic) liquid crystal mode and a static drive type represented by TN (Twisted Nematic) liquid crystal mode A device can be formed. When disposing the optical film with pressure sensitive adhesive or laminated optical member of the present invention on both sides of the liquid crystal cell, the same optical film configuration may be disposed on both sides, or different ones may be disposed on both sides. . When the optical film with a pressure-sensitive adhesive or the laminated optical member of the present invention is applied to an organic EL display device, it can be used as a circularly polarized light or an elliptically polarizing plate having an antireflection function.

  FIG. 7 is a schematic cross-sectional view showing an example in which the elliptically polarizing plate 15 with pressure-sensitive adhesive shown in FIG. 5 is applied to a liquid crystal display device. In the example of FIG. 7, the state in which the release film 10 has been peeled off from the elliptically polarizing plate 15 with pressure-sensitive adhesive shown in FIG. 5 is provided on one side of the liquid crystal cell 30 via the second pressure-sensitive adhesive layer 8 ( 7 is a laminate in which another optical layer 20 is laminated on the protective film 3 side of the elliptically polarizing plate 15 in FIG. 5 on the other surface (lower side in FIG. 7) of the liquid crystal cell 30. The optical member 21 is also stuck via the second pressure-sensitive adhesive layer 8. The liquid crystal display device of this example is provided on the lower side of FIG. 7 when the upper side of FIG. 7 is the viewing side and the backlight is arranged. The other optical layer 20 in this case can be a reflective layer, a transflective layer, a brightness enhancement film, a light collector, or the like.

  FIG. 8 is a schematic cross-sectional view showing an example in which the elliptically polarizing plate 16 with pressure-sensitive adhesive shown in FIG. 6 is applied to a liquid crystal display device. In the example of FIG. 8, the state in which the release film 10 is peeled off from the elliptically polarizing plate 16 with pressure-sensitive adhesive shown in FIG. 6 is one side of the liquid crystal cell 30 via the second pressure-sensitive adhesive layer 8 ( 8 is bonded to the upper side of the liquid crystal cell 30, and another optical layer 20 is laminated on the protective film 3 side of the elliptically polarizing plate 16 of FIG. The optical member 22 is also adhered via the second pressure-sensitive adhesive layer 8. The liquid crystal display device of this example is provided on the lower side of FIG. 8 when the upper side of FIG. The other optical layer 20 in this case can also be a reflective layer, a transflective layer, a brightness enhancement film, a light collector, and the like.

  The image display device provided with the optical film with pressure-sensitive adhesive of the present invention can scatter incident light and blur the reflected image due to the light diffusibility exhibited by the pressure-sensitive adhesive layer, and has excellent visibility. To give.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples, but the present invention is not limited to these examples. In the examples, the parts representing the content or amount used are based on weight unless otherwise specified.

[Example 1]
(A) Preparation of light diffusive pressure-sensitive adhesive The solid content in an organic solvent solution of an adhesive resin in which an isocyanate-based crosslinking agent is added to a copolymer of butyl acrylate and acrylic acid (refractive index 1.47) Add 100 parts of polymethyl methacrylate beads (refractive index 1.49, commercially available) having a particle size distribution of approximately monodisperse and an average particle diameter of 2.6 μm per 100 parts as a light diffusing agent to obtain an adhesive composition. Prepared. Next, a release treatment surface of a 38 μm-thick polyethylene terephthalate film (“PET 3811” (trade name) obtained from Lintec Co., Ltd., which becomes the release film described above) subjected to a release treatment, The pressure-sensitive adhesive composition prepared above was applied so that the thickness after drying was 25 μm and dried to obtain a sheet-like light-diffusible pressure-sensitive adhesive.

(B) Formation of pressure-sensitive adhesive layer on transparent resin film On one side of a 40 μm-thick triacetylcellulose film, the surface opposite to the release film of the sheet-like pressure-sensitive adhesive prepared in (A) above (sensation The pressure adhesive surface) was bonded. As shown in the schematic cross-sectional view of FIG. 9, the laminate prepared here has a pressure-sensitive adhesive layer 6 containing fine particles bonded to one side of a transparent resin film (triacetyl cellulose film) 3, and further to the outside. A release film 10 is attached to form a transparent resin film 18 with a pressure sensitive adhesive.

(C) Formation of pressure-sensitive adhesive layer on retardation film Retardation film obtained by uniaxial stretching of cyclic polyolefin resin [Essina (trade name) obtained from Sekisui Chemical Co., Ltd., in-plane retardation of 140 nm The surface (pressure-sensitive adhesive surface) opposite to the release film of the sheet-shaped pressure-sensitive adhesive prepared in the above (A) was bonded to one side. The laminate obtained here is a retardation film 14 with a pressure-sensitive adhesive having the layer configuration shown in FIG.

(D) Production of elliptically polarizing plate with pressure-sensitive adhesive A protective film made of triacetylcellulose is bonded to one side of a polyvinyl alcohol polarizer on which iodine is adsorbed and oriented via an adhesive, and acrylic on the other side. A polarizing film provided with a pressure-sensitive adhesive layer (without fine particles) was prepared. The retardation film side of the retardation film with pressure-sensitive adhesive prepared in the above (C) was attached to the pressure-sensitive adhesive layer of the polarizing film. At this time, the transmission axis of the polarizer and the slow axis of the retardation film intersect at an angle of 45 °. The obtained laminate is an elliptically polarizing plate 15 with a pressure-sensitive adhesive having the layer configuration shown in FIG.

[Comparative Examples 1-3]
Instead of polymethyl methacrylate beads having an average particle size of 2.6 μm, the following were used as light diffusing agents.

Comparative Example 1: Polymethyl methacrylate beads having a particle size distribution of almost monodisperse and an average particle size of 5.5 μm (refractive index: 1.49, commercially available product).
Comparative Examples 2 and 3: Silicone resin beads having a particle size distribution of almost monodisperse and an average particle size of 4.5 μm (refractive index: 1.43, commercially available product).

  The addition amount of these light diffusing agents (per 100 parts of the adhesive resin) is as shown in Table 1, and the others are the same as in Example 1, and the transparent resin film with pressure-sensitive adhesive and the elliptically polarizing plate with pressure-sensitive adhesive are used. Produced.

[Comparative Example 4]
A transparent resin film with a pressure-sensitive adhesive and an elliptically polarizing plate with a pressure-sensitive adhesive were produced in the same manner as in Example 1 except that no light diffusing agent was added to the pressure-sensitive adhesive composition.

[Evaluation test]
Using the transparent resin film with pressure-sensitive adhesive or the elliptically polarizing plate with pressure-sensitive adhesive prepared in each of the above examples, the optical properties were evaluated by the following methods.

(Haze)
The haze of the pressure-sensitive adhesive layer was measured using a haze meter “HM-150” manufactured by Murakami Color Research Laboratory Co., Ltd. based on JIS K 7136. That is, the pressure-sensitive adhesive-attached transparent resin film produced by the method shown in Example 1 (B) was bonded to glass on the pressure-sensitive adhesive layer side in order to prevent the sample from warping, and in that state. Total haze was measured.

(Transparency)
Transparency was measured using “Haze Guard Plus” (purchased from Toyo Seiki Seisakusho Co., Ltd.) manufactured by Big Gardner. As in the case of the above haze measurement, the measurement was performed in a state where the transparent resin film with a pressure sensitive adhesive produced by the method shown in (B) of Example 1 was bonded to glass.

(Glitter)
The glare was evaluated by the following method. That is, first, a photomask having a pattern of unit cells 40 shown in a plan view in FIG. 10 was prepared. In this photomask, a chromium light shielding pattern 41 is formed on a transparent substrate, and a portion where the light shielding pattern 41 is not formed is an opening 42. The unit cell 40 has a size of 80 μm in length × 50 μm in width, and four openings 42 having a size of 25 μm in length × 18 μm in width are arranged therein. Each of the light shielding patterns separating the horizontal openings 42 and 42 (the light shielding pattern itself running vertically in the figure) has a line width of 7 μm. The line widths of the light shielding patterns that separate (the light shielding patterns themselves run horizontally in the figure) are 7 μm above the unit cell 40 and 23 μm at the center of the unit cell. A large number of unit cells 40 shown in the figure are arranged vertically and horizontally to form a photomask. FIG. 11 is a plan view schematically showing a state in which the unit cell 40 shown in FIG. 10 is arranged in six sets horizontally and three sets vertically, but in reality a state in which a larger number of unit cells 40 are arranged. It has become. In FIG. 11, a portion surrounded by a thick line on the upper right corresponds to one unit cell 40.

  Then, as shown in the schematic cross-sectional view of FIG. 12, the photomask 43 is placed in the light box 45 with the chromium light shielding pattern 41 facing upward. A light source 46 is disposed in the light box 45. The transparent resin film 18 with a pressure sensitive adhesive produced by the method shown in Example 1 (B), which is an object to be evaluated for glare, is bonded to the glass plate 47 on the pressure sensitive adhesive layer side, and this is an evaluation sample. And This sample is placed on the photomask 43 so that the glass plate 47 is on the photomask 43 side. In this state, the CCD camera 48 (“EyeScale-3W”, manufactured by Eye System Co., Ltd.) placed at a position approximately 30 cm away from the sample sets one section to 100 μm × 100 μm, and the brightness of each section is gray. The image was taken as an image expressed in 256 scales. The luminance distribution of this image was analyzed using image analysis software “ScnImage” obtained from Scicon Corporation. The standard deviation σ was determined from the obtained luminance distribution. If the standard deviation σ of brightness is 0.03 or less, no glare is recognized.

(Depolarization)
Two polarizing films “Sumikaran” sold by Sumitomo Chemical Co., Ltd. are placed so that their absorption axes are orthogonal to each other, and orthogonal transmittance is measured using a spectrophotometer [“V7100” manufactured by JASCO Corporation] T ₀ was measured. The orthogonal transmittance T ₀ is expressed by T ₀ = T _A · T _B using the transmission axis transmittance T _A and the absorption axis transmittance T _B of one polarizing film. On the other hand, a transparent resin film with a pressure-sensitive adhesive produced by the method shown in (B) of Example 1 is sandwiched between two polarizing films having absorption axes orthogonal to each other as described above on the pressure-sensitive adhesive layer side. What was bonded to glass was placed, and the orthogonal transmittance T ₁ was measured in this state. The orthogonal transmittance T ₁ obtained by arranging the light diffusing layer in this manner is obtained by depolarizing by the light diffusing layer, and obtained by placing only the two polarizing films. T ₀ is more increased, as the difference between T ₁ and T ₀ is small, it is determined that depolarization is small.

(Smear and blur)
An elliptically polarizing plate with a pressure-sensitive adhesive prepared by the method shown in Example 1 (D) was attached to the viewing side of a transflective liquid crystal panel having a pixel pitch of 25 μm on the pressure-sensitive adhesive layer side. A transflective liquid crystal display device was produced. By visually observing this transflective liquid crystal display device, the state of blurring and blurring was subjected to sensory evaluation.

  The results of the above evaluation tests are summarized in Table 2. In Table 2, (I) summarizes the optical characteristics of the transparent resin film with pressure-sensitive adhesive obtained in each example (which can be regarded as the optical characteristics of the pressure-sensitive adhesive layer itself), and (II) This is a summary of the visibility when an optical film with a pressure sensitive adhesive is applied to an image display device.

  As shown in Table 2, Example 1, which satisfies the requirements of the present invention, was free of glare, depolarization was small, no blurring or blurring, and showed excellent visual performance. In contrast, Comparative Example 1 has a small difference in refractive index between the fine particles and the base resin, and the amount of fine particles added is large, so there is no blurring or blurring in the display image. It was strong. In Comparative Example 2, since the addition amount of the fine particles was small, the display image was not blurred or blurred, but the glare was strong. In Comparative Example 3, since the amount of fine particles added was large, the display image did not bleed or blur, and there was no glare, but depolarization was great. In Comparative Example 4, no fine particles were added, so there was no glare and depolarization was small, but the display image was blurred.

It is a top view which shows typically the relationship between each pixel (sub pixel) which displays three primary colors of red (R), green (G), and blue (B), and a pixel pitch about a color image display apparatus. It is a cross-sectional schematic diagram which shows an example of a layer structure about the optical film with a pressure sensitive adhesive of this invention. It is a cross-sectional schematic diagram which shows another example of a layer structure about the optical film with a pressure sensitive adhesive of this invention. It is a cross-sectional schematic diagram which shows another example of a layer structure about the optical film with a pressure sensitive adhesive of this invention. It is a cross-sectional schematic diagram which shows another example of a layer structure about the optical film with a pressure sensitive adhesive of this invention. It is a cross-sectional schematic diagram which shows another example of a layer structure about the optical film with a pressure sensitive adhesive of this invention. It is a cross-sectional schematic diagram which shows the example in the case of applying the optical film with a pressure sensitive adhesive shown in FIG. 5 to a liquid crystal display device. It is a cross-sectional schematic diagram which shows the example in the case of applying the optical film with a pressure sensitive adhesive shown in FIG. 6 to a liquid crystal display device. It is a cross-sectional schematic diagram which shows the layer structure of the transparent resin film with a pressure sensitive adhesive produced in the Example. It is a top view which shows the unit cell of the pattern for glare evaluation. It is a top view which shows typically the photomask in which many unit cells of FIG. 10 were located in a line. It is a cross-sectional schematic diagram which shows the state of glare evaluation.

Explanation of symbols

1R: Red sub-pixel,
1G …… Green sub-pixel,
1B: Blue sub-pixel,
2 ... Polarizer,
3 ... Protective film (transparent resin film)
4. Retardation film (can also be a second retardation film and can be a λ / 4 plate),
5. First retardation film (can be a λ / 2 plate),
6 …… Pressure-sensitive adhesive layer containing fine particles,
7, 8, 9 ... Pressure-sensitive adhesive layer (sometimes fine particles are blended),
10 …… Peeling film,
11: Polarizing film,
12, 13 ... Polarizing film with pressure sensitive adhesive,
14 ... retardation film with pressure sensitive adhesive,
15, 16 ... Elliptical polarizing plate with pressure sensitive adhesive,
18 …… Transparent resin film with pressure sensitive adhesive,
20 ... an optical layer exhibiting other optical functions,
21, 22 ... Laminated optical member,
30 ... Liquid crystal cell,
40 …… Photomask unit cell,
41 …… Chrome shading pattern of photomask,
42 …… Opening of photomask,
43 …… Photomask,
45 …… Light box,
46 …… Light source,
47 …… Glass plate,
48 …… CCD camera for shooting brightness.

Claims (7)

An optical film with a pressure sensitive adhesive in which an optical film and a pressure sensitive adhesive layer are laminated,
The pressure-sensitive adhesive layer has a refractive index difference of 0.01 to 0 between an adhesive resin having an acrylic polymer as a main component and an average particle diameter of 0.1 to 4 μm and a polymer constituting the adhesive resin. Containing fine particles of acrylic resin in the range of .05,
The fine film is present in an amount of 10 to 40 parts by weight per 100 parts by weight of the adhesive resin.   The optical film with a pressure-sensitive adhesive according to claim 1, wherein the pressure-sensitive adhesive layer has a haze in the range of 20 to 80%.   The optical film with pressure-sensitive adhesive according to claim 1 or 2, wherein the pressure-sensitive adhesive layer has a transparency of 90% or more.   The optical film with a pressure-sensitive adhesive according to any one of claims 1 to 3, wherein the pressure-sensitive adhesive layer has a thickness in the range of 1 to 40 µm.   The optical film with pressure-sensitive adhesive according to any one of claims 1 to 4, wherein the optical film is selected from the group consisting of a polarizing film and a retardation film.   A laminated optical member comprising a laminate of the optical film with a pressure-sensitive adhesive according to claim 5 and an optical layer exhibiting another optical function.   An image display element having a pixel pitch in the range of 10 to 50 μm, and the optical film with a pressure-sensitive adhesive according to claim 1 or the laminated optical member according to claim 6. An image display device.

Images