JP5267925B2 - Hard coat film, method for producing the same, and polarizing plate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inexpensive hard coat film in which a hard coat layer is provided on at least one side of a transparent support and which has high hardness to prevent the hurt and blemish of its surface when arranged on the outermost surface of an image display apparatus and can obtain good visibility even when used outdoors when arranged on the outermost surface, a method for manufacturing the hard coat film, and a polarizing plate. <P>SOLUTION: The hard coat film has the transparent support, a hard coat layer which is formed on at least one side of the support to be 10-30 &mu;m in thickness and made of the cured product of a curable resin composition containing an ionizing radiation curable resin and a leveling agent, and a scattering reflectance Y of 0.2% or below. The method for producing the hard coat film and the polarizing plate are disclosed. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention is a hard coat film provided with a hard coat layer on at least one side of the transparent support, has a high hardness sufficient to prevent scratches and dirt on the surface when placed on the outermost surface, and An inexpensive hard coat film that can obtain good visibility even when used in a transflective method in which external light is taken in and displayed on a screen when placed on the outermost surface of an image display device, and a method for manufacturing the same . In addition, the present invention relates to a hard coat film having a hard coat layer, which sufficiently suppresses curling due to curing shrinkage that causes problems during handling or processing into an optical element, and a method for producing the same. Furthermore, this invention relates to optical elements, such as a polarizing plate using the hard coat film mentioned above.

  Image display devices such as liquid crystal displays, plasma display panels, cathode ray tube (CRT) displays, and organic electroluminescence (EL) displays are used in home appliances such as mobile phones, digital cameras, notebook personal computers, monitors, and televisions. Widely incorporated and used.

  A liquid crystal display widely used in recent years as an image display device has a configuration in which a polarizing film is bonded to the front and back surfaces of a liquid crystal cell in which liquid crystal molecules are sealed between two flat glass plates provided with transparent electrodes and color filters. . Mobile phones and digital cameras that are frequently carried around are more prone to scratches on the surface of the image display device compared to televisions, monitors, and notebook personal computers. Therefore, a cover made of a transparent resin plate or glass plate is installed on the image display device. In many cases, the surface was protected.

  In recent years, mobile phones and digital cameras may be used with the cover removed for the purpose of further miniaturization, weight reduction, and thickness reduction. There has been a problem that the visibility of the display is lowered due to the reflection of light. Therefore, the hard coat film is required to further improve the visibility.

  Hard coat film that is placed on the outermost surface of the image display device and used for the purpose of improving the visibility of the display has been subjected to non-reflective treatment using interference by an optical multilayer film in order to improve the visibility. In addition, there has been provided a film made of an anti-glare treatment that forms fine irregularities on the surface to scatter incident light and blur the reflected image. Among these, the former non-reflective film needs to form a multilayer film having a uniform optical film thickness, and thus increases the cost. The latter antiglare film can be manufactured at a relatively low cost, but has a rough surface due to unevenness and is rarely used in mobile phones and digital cameras for design reasons.

  Further, in the field where the surface cover is removed, a hard coat layer having a higher hardness and less scratching than before is demanded.

  As a method for increasing the hardness of the hard coat layer, for example, JP-A-9-254321 (Patent Document 1) discloses an ultraviolet curable resin composition containing a polyfunctional (meth) acrylate monomer and a reactive monomer having a nitrogen atom. A cured product layer is introduced. However, since the hardened | cured material layer disclosed by patent document 1 is coated with the film thickness of 3 micrometers, it is inadequate as hardness under the influence of a transparent support body.

Japanese Patent Application Laid-Open No. 9-113728 (Patent Document 2) proposes a hard coat film using dipentaerythritol hexaacrylate as an ultraviolet curable polyol acrylate resin. In this document, there is a description of a method of increasing the thickness of the hard coat layer in order to eliminate the influence of a transparent support having a low hardness as a base, and the pencil hardness is 4H by increasing the thickness of the hard coat layer to 10 μm or more. Although the above has been achieved, there has been a problem that curling tends to occur due to curing shrinkage.

  In order to improve the coating film hardness and suppress curling due to curing shrinkage, a method of putting a filler in the coating film has also been proposed. For example, in Japanese Patent Application Laid-Open No. 2000-052472 (Patent Document 3), two hard coat layers are provided, the first hard coat layer close to the transparent base material contains ultrafine particles, and the second is provided thereon. It is described that the hard coat layer does not contain ultrafine particles. The hard coat film disclosed in Patent Document 3 achieves a pencil hardness of 4H by setting the thickness of the hard coat layer to 10 μm or more. However, since it has a two-layer structure, productivity and economy are improved. There are disadvantages.

Japanese Patent Application Laid-Open No. 2000-112379 (Patent Document 4) discloses a hard coat layer forming material containing 20 to 80 parts by weight of inorganic fine particles per 100 parts by weight of resin forming the hard coat layer, and having a thickness of 10 μm or more. It is described that a hard coat film having a pencil hardness of 4H or more is formed by forming a coat layer. However, it is difficult for the coating liquid disclosed in Patent Document 4 to have an appropriate pencil hardness by suppressing curling due to curing shrinkage.

Further, JP 2007-46031 A (Patent Document 5) discloses a hard coat formed from a material containing urethane acrylate, polyol (meth) acrylate, and a (meth) acrylic polymer having an alkyl group containing two or more hydroxyl groups. A hard coat film having a layer is described. The hard coat film disclosed in Patent Document 5 achieves a pencil hardness of 4H by setting the thickness of the hard coat layer to 15 μm or more, and the hard coat layer forming material may contain a leveling agent. However, there is no description about the scattering reflectance Y value. As parameters affecting the scattering reflectance, it is known that the composition ratio of the additive and the manufacturing conditions at the time of forming the hard coat layer are affected, but in the example of Patent Document 5, the thickness is 15 to 35 μm. When the hard coat layer is formed, the scattering reflectance Y value is not necessarily 0.2% or less when the film thickness is 20 μm or more. It is also described that an antireflection film is formed on the outer surface of the hard coat layer to improve visibility. However, in this case, disadvantages such as deterioration in productivity and cost increase occur.
Japanese Patent Laid-Open No. 9-254321 Japanese Laid-Open Patent Publication No. 9-11728 Japanese Patent Laid-Open No. 2000-052472 JP 2000-112379 A JP 2007-46031 A

  The present invention has been made in view of the above circumstances, and its object is a hard coat film in which a hard coat layer is provided on at least one side of a transparent support, which is disposed on the outermost surface. Inexpensive hardware that has sufficient hardness to prevent scratches and dirt on the surface, and provides good visibility even when used outdoors when placed on the outermost surface of an image display device It is providing a coat film and its manufacturing method.

  Another object of the present invention is to provide a hard coat film having a hard coat layer that causes problems during handling and processing into an optical element and has curling due to curing shrinkage sufficiently suppressed, and a method for producing the same.

  Another object of the present invention is to provide an optical element such as a polarizing plate using the hard coat film.

  The present invention relates to a hard coat layer comprising a transparent support and a cured product of a curable resin composition containing an ionizing radiation curable resin and a leveling agent formed on at least one surface of the transparent support with a thickness of 10 to 30 μm. And a hard coat film having a scattering reflectance Y value of 0.2% or less.

  In the hard coat film of the present invention, the hard coat layer is formed from a curable resin composition containing a leveling agent in a proportion of 0.01 to 1 part by weight per 100 parts by weight of the ionizing radiation curable resin. preferable.

  The leveling agent in the hard coat film of the present invention preferably has at least one of a polysiloxane structure or a fluorine-containing group.

  The present invention is also a method for producing a hard coat film in which a hard coat layer comprising a cured product of a curable resin composition containing an ionizing radiation curable resin and a leveling agent is formed on the surface of a transparent support, A coating solution diluted with a solvent consisting of at least one of ethyl acetate, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone so that the concentration of ionizing radiation curable resin is 30 to 70% by weight on a transparent support. The present invention also provides a method for producing a hard coat film in which a hard coat layer is formed by applying the composition to a substrate and drying at a temperature in the range of 40 to 80 ° C., followed by curing by irradiation with ionizing radiation.

  The present invention further provides a polarizing plate in which the above-described hard coat film of the present invention is bonded to a polarizing film on the transparent support side.

  According to the present invention, a hard coat film on which a hard coat layer exhibiting good visibility even when used outdoors and having sufficient hardness to prevent scratches on the surface is formed at low cost. Can be provided. Further, it is possible to provide a hard coat film in which curling due to curing shrinkage, which causes problems during handling and processing into an optical element, is sufficiently suppressed.

  FIG. 1 is a cross-sectional view schematically showing a hard coat film 1 as a preferred example of the present invention. The hard coat film 1 of the present invention is a hard coat comprising a transparent support 2 and a cured product of a curable resin composition including an ionizing radiation curable resin and a leveling agent provided on at least one surface of the transparent support 2. Layer 3 is basically provided.

  The transparent support 2 used in the present invention may be a substantially optically transparent resin film. For example, the amorphous support having triacetyl cellulose, polyethylene terephthalate, polymethyl methacrylate, polycarbonate, norbornene compound as a monomer. A solvent cast film or an extruded film made of a thermoplastic resin such as a conductive cyclic polyolefin can be used. Among these, when using a (meth) acrylate-based material, which will be described later in the market, as the ionizing radiation curable resin, the refractive index difference from the ionizing radiation curable resin is reduced, and the cured product thereof is used. From the viewpoint of obtaining sufficient adhesion with a certain hard coat layer, it is preferable to use a resin film formed of triacetyl cellulose as the transparent support 2.

  In the present invention, examples of the ionizing radiation curable resin contained in the curable resin composition used for forming the hard coat layer 3 include an ultraviolet curable resin, a thermosetting resin, and an electron beam curable resin. From the viewpoints of productivity and hardness, an ultraviolet curable resin is preferably used. Examples of the ultraviolet curable resin include trimethylolpropane tri (meth) acrylate, trimethylolpropane tris (hydroxyethyl (meth) acrylate), tris (2-hydroxyethyl) isocyanurate tri (meth) acrylate, pentaerythritol tri ( Examples include (meth) acrylate resins mainly composed of (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol hexa (meth) acrylate, polyfunctional urethanized (meth) acrylate, and the like. Here, the polyfunctional urethanized (meth) acrylate is, for example, a polyisocyanate having at least two isocyanato groups (—NCO) in the molecule, such as isophorone diisocyanate or hexamethylene diisocyanate, and trimethylolpropane di ( A urethane bond and at least two compounds obtained by addition reaction of a compound having one hydroxyl group and at least one (meth) acryloyl group in the molecule, such as (meth) acrylate and pentaerythritol tri (meth) acrylate It is a compound having a (meth) acryloyl group. These ultraviolet curable resins can be used alone or in admixture of two or more. In the present invention, since the hard coat layer 3 is thickened to 10 to 30 μm, polyfunctional urethanized (meth) acrylate is used as an ultraviolet curable resin in order to maintain flexibility and ensure hardness. It is preferable. Furthermore, it is also effective to use a polyfunctional urethanized (meth) acrylate in combination with a polyfunctional (meth) acrylate having no urethane bond as described above.

  As the ultraviolet curable resin, a commercially available resin can be suitably used. Specific examples of commercially available UV curable resins include Kayrad DPHA (manufactured by Nippon Kayaku Co., Ltd.), Kayarad DPCA-20 (manufactured by Nippon Kayaku Co., Ltd.), Kayrad DPCA-30 (Nippon Kayaku ( Kayarad DPCA-60 (manufactured by Nippon Kayaku Co., Ltd.), Kayarad DPCA-120 (manufactured by Nippon Kayaku Co., Ltd.), Kayarad D-310 (manufactured by Nippon Kayaku Co., Ltd.), Kayarad D- 330 (Nippon Kayaku Co., Ltd.), Kayalad PET-30 (Nippon Kayaku Co., Ltd.), Kayalad GPO-303 (Nippon Kayaku Co., Ltd.), Kayarad TMPTA (Nippon Kayaku Co., Ltd.) Kayrad THE-330 (Nippon Kayaku Co., Ltd.), Kayarad TPA-330 (Nippon Kayaku Co., Ltd.), Aronix M-315 (Toagosei Co., Ltd.), Aronix M-325 (East Made of synthetic Co., Ltd.), and the like.

  The ultraviolet curable resin as described above is usually used by mixing with a photopolymerization initiator. As the photopolymerization initiator, for example, commercially available products such as Irgacure 907 (Ciba Specialty Chemicals), Irgacure 184 (Ciba Specialty Chemicals), and Lucillin TPO (BASF) are suitable. Can be used.

In the hard coat film 1 of the present invention have a sufficiently high hardness, from the viewpoint of obtaining a hard coat layer 3 which can sufficiently suppress the curl by curing shrinkage, as the addition of silica fine particles in the ultraviolet curable resin Also good. In this case, examples of the silica fine particles include powdery silica and colloidal silica, and those having an average particle diameter in the range of 0.01 to 20 μm are preferably used. Further, the silica fine particles are preferably those that do not affect the light transmittance of the hard coat film, and for that purpose, the primary particle diameter is preferably in the range of 10 to 350 nm, and in the range of 10 to 50 nm. More preferably, it is within. The average particle size of the silica fine particles described above can be measured, for example, by observing with a transmission electron microscope, and the primary particle size of the silica fine particles is, for example, dispersed in a solvent such as isopropyl alcohol, The dispersion can be measured by a Coulter particle size distribution measurement method, a laser diffraction scattering method, a dynamic light scattering method, or the like. Among these, the Coulter particle size distribution measurement method is general.

The shape of the silica fine particles may be spherical, hollow, porous, rod-like, plate-like, fiber-like, or indefinite, but in order to disperse the particles appropriately without agglomerating in the ultraviolet curable resin. Is preferably spherical. Further, from the viewpoint of maintaining the hardness and flatness of the hard coat layer 3, it is preferable that the specific surface area of the silica fine particles is in the range of 0.1~3000m ² / g, more 1 m ² / g or more, especially 10m More preferably, it is ² / g or more and 1500 m ² / g or less.

  Such silica fine particles are also commercially available. Examples of commercially available silica fine particles include methanol silica sol (manufactured by Nissan Chemical Industries, Ltd.), IPA-ST (manufactured by Nissan Chemical Industries, Ltd.), MEK-ST (manufactured by Nissan Chemical Industries, Ltd.). ), NBA-ST (manufactured by Nissan Chemical Industries, Ltd.), XBA-ST (manufactured by Nissan Chemical Industries, Ltd.), DMAC-ST (manufactured by Nissan Chemical Industries, Ltd.), ST-UP (Nissan Chemical Industries, Ltd.) ST-OUP (Nissan Chemical Industry Co., Ltd.), ST-20 (Nissan Chemical Industry Co., Ltd.), ST-40 (Nissan Chemical Industry Co., Ltd.), ST-C (Nissan Chemical Industry) ST-N (manufactured by Nissan Chemical Industries, Ltd.), ST-O (manufactured by Nissan Chemical Industries, Ltd.), ST-50 (manufactured by Nissan Chemical Industries, Ltd.), ST-OL (Nissan) Chemical Industry Co., Ltd.). Examples of powdered silica include Aerosil 130 (manufactured by Nippon Aerosil Co., Ltd.), Aerosil 300 (manufactured by Nippon Aerosil Co., Ltd.), Aerosil 380 (manufactured by Nippon Aerosil Co., Ltd.), Aerosil TT600 (manufactured by Nippon Aerosil Co., Ltd.). ), Aerosil OX50 (produced by Nippon Aerosil Co., Ltd.), Sildex H31 (produced by Asahi Glass Co., Ltd.), Sildex H32 (produced by Asahi Glass Co., Ltd.), Sildex H51 (produced by Asahi Glass Co., Ltd.), Sildex H52 (produced by Asahi Glass Co., Ltd.) Asahi Glass Co., Ltd.), Sildex H121 (Asahi Glass Co., Ltd.), Sildex H122 (Asahi Glass Co., Ltd.), E220A (Nihon Silica Industry Co., Ltd.), E220 (Nihon Silica Industry Co., Ltd.) , Silicia 470 (manufactured by Fuji Silysia Co., Ltd.), SG flake (manufactured by Nippon Sheet Glass Co., Ltd.), and the like.

  In the present invention, a leveling agent is added to the curable resin composition used for forming the hard coat layer 3 in order to ensure the surface smoothness of the obtained hard coat layer 3. A leveling agent is an agent having an effect of adding to a paint to reduce the surface tension of the paint and improving the surface smoothness of the paint film.

  Substances commonly used as leveling agents include polyacrylate polymers such as polyalkyl acrylates; polyvinyl ether polymers such as polyalkyl vinyl ethers; dimethylpolysiloxanes, methylphenylpolysiloxanes, as well as polyethers, polyesters, and aralkyls. Examples thereof include silicone-based polymers such as organically modified polysiloxane into which is introduced. These polymers can control the surface tension when added to the paint by changing the structure of the side chain. For example, in a silicone-based leveling agent, the ability to reduce the surface tension when added to a paint can be controlled by changing the alkyl chain length of the side chain. The shorter the alkyl side chain, the lower the surface tension. By adding such a leveling agent, the coating film surface tension in the coating film forming process can be lowered, and as a result, the unevenness of the coating film surface is reduced. In order to effectively reduce the surface tension of the coating film, the surface tension of the leveling agent is preferably made lower than the surface tension of the ionizing radiation curable resin.

  Among the above, it is preferable to use a leveling agent having at least one of a polysiloxane structure or a fluorine-containing group because the effect of reducing the surface tension of the paint is high. The above-mentioned silicone-based polymer itself becomes a leveling agent having a polysiloxane structure. In addition, the polyacrylate polymer and the polyvinyl ether polymer described above can be made into a polymer having a fluorine-containing group by copolymerizing a monomer having a fluorine-containing group in the production thereof, or a silicone polymer can be grafted. By polymerizing, a polymer having a polysiloxane structure can be obtained.

  Note that leveling agents using polyacrylate polymers and leveling agents using polyvinyl ether polymers tend to have higher surface tension than leveling agents using silicone polymers, but have fluorine-containing groups. By introducing the unit, the surface tension can be lowered. In addition, the leveling agent using a polyacrylate polymer and the leveling agent using a polyvinyl ether polymer have less wettability reduction on the surface of the coating film of the additive system compared to the leveling agent using a silicone polymer, and The compatibility is high, and the resulting coating film is excellent in transparency. By graft polymerizing (polymerizing) a polysiloxane polymer to these polymer main chains, it is possible to reduce the surface tension while maintaining compatibility with the resin. Commercial products of such graft polymer leveling agents include Cymac US-150 (manufactured by Toagosei Co., Ltd.), Cymac US-270 (manufactured by Toagosei Co., Ltd.), and Cymac US-350 (Toagosei Co., Ltd.). Manufactured), Symac US-450 (manufactured by Toagosei Co., Ltd.)

  In the present invention, the leveling agent is preferably blended so as to be a ratio of 0.01 to 1 part by weight per 100 parts by weight of the ionizing radiation curable resin in the curable resin composition. When the leveling agent is less than 0.01 part by weight per 100 parts by weight of the ionizing radiation curable resin in the curable resin composition, the smoothness of the hard coat layer surface is lost, and there is a possibility that a defect of the tin pattern may occur in the wave. This is not preferable. Further, when the leveling agent exceeds 1 part by weight per 100 parts by weight of the ionizing radiation curable resin in the curable resin composition, fine roughness will be present on the surface, and external light is taken into the display device for visual recognition. When the hard coat film is disposed on the outermost surface of the image display device used in the above, the visibility from the front of the image display device is lowered, which is not preferable. More preferably, by setting the blending amount of the leveling agent to 0.1 parts by weight or less per 100 parts by weight of the ionizing radiation curable resin in the curable resin composition, it is hard to increase the scattering reflectance Y value (described later). The surface state of the coated film surface can be kept smooth.

The hard coat film 1 of the present invention is prepared by applying a coating liquid containing a curable resin composition containing an ionizing radiation curable resin and a leveling agent as described above onto the transparent support 2 and ionizing radiation (ionizing radiation curable). When the resin is an ultraviolet curable resin, the curable resin composition is cured by irradiating ultraviolet rays), and a hard coat layer 3 that is a cured product of the curable resin composition is formed on the transparent support 2. It can manufacture by the method to do.

  In the present invention, the coating liquid used for forming the hard coat layer 3 has an ionizing radiation curable resin having a solid content of 30 to 70 weights using at least one of ethyl acetate, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone as a solvent. It can be obtained by diluting to a percentage. Here, when the solid content of the ionizing radiation curable resin in the coating solution is less than 30% by weight, the solvent concentration is too high when the coating solution is applied onto the transparent support, and the thickness is 10 to 30 μm. It is difficult to obtain a coating film, and when the solid content of the ionizing radiation curable resin in the coating liquid exceeds 70% by weight, the viscosity of the coating liquid is too high and unevenness occurs in the coating film, resulting in an appearance. This is because of loss.

  When using the coating liquid diluted with the solvent as described above, after coating the coating liquid on the transparent support 2, the coating liquid is dried before irradiating with ionizing radiation and curing the curable resin composition. It is preferable to evaporate most of the solvent so that only the solid content of the ionizing radiation curable resin composition is obtained. In this case, the drying temperature is preferably in the range of 40 to 80 ° C. When the drying temperature is higher than 80 ° C., the solvent and leveling agent component that evaporates become spot-like marks on the surface of the coating film, resulting in deterioration of the coating film appearance and contrast in a bright place when applied to an image display device. This causes an unfavorable ratio reduction and is not preferable. On the other hand, when the drying temperature is less than 40 ° C., the solvent cannot be sufficiently evaporated and the solvent remains in the coating film, which is not preferable. In addition, drying is performed stepwise within a range of 40 to 80 ° C., using a plurality of dryers from a low temperature to a high temperature, for example, heating at 40 ° C. for 30 seconds and then heating at 65 ° C. for 1 minute. It is preferable to apply a temperature to.

  Therefore, the present invention is a method for producing a hard coat film in which a hard coat layer comprising a cured product of a curable resin composition containing an ionizing radiation curable resin and a leveling agent is formed on the surface of a transparent support. A coating solution diluted to a concentration of ionizing radiation curable resin (solid content) of 30 to 70% by weight with respect to a solvent composed of at least one of ethyl acetate, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone. Also provided is a method for producing a hard coat film in which a hard coat layer is formed by coating on a transparent support, drying at a temperature in the range of 40 to 80 ° C., and then curing by irradiation with ionizing radiation. By the manufacturing method of the hard coat film of the present invention, the above-described hard coat film 1 of the present invention can be preferably manufactured.

In the hard coat film 1 of the present invention, the thickness of the hard coat layer 3 is set to 10 μm or more in order to eliminate the influence of the transparent support 2 as much as possible and to sufficiently develop the hardness of the hard coat layer 3. In particular, when the transparent support 2 itself is easily deformed, such as the transparent support 2 formed using a triacetyl cellulose film, polyethylene terephthalate, polymethyl methacrylate, or polycarbonate, the influence of the ease of deformation is affected. In order to remove the thickness, it is preferable that the thickness of the hard coat layer 3 is 15 μm or more. By increasing the thickness of the hard coat layer 3 in this way, it is possible to effectively express the original hardness of the hard coat layer 3 excluding the influence of the soft transparent support 2.

  On the other hand, the hard coat layer 3 has a thickness of 30 μm or less, more preferably 25 μm or less, and particularly preferably 20 μm or less. When the thickness of the hard coat layer exceeds 30 μm, the bending resistance due to the thickness of the hard coat layer is reduced, and cracks and cracks are likely to occur when the film is handled and processed.

  The hard coat film 1 of the present invention is designed so that the scattering reflectance Y value of the surface of the hard coat layer 3 is 0.2% or less. Here, the scattering reflectance Y value will be described. Normally, when a person visually observes the film surface in a bright place, he / she looks in the absence of specular reflection light, so in order to measure the reflected light intensity that is almost the same as that felt by humans, exclude specular reflection light. Therefore, it is necessary to measure only diffuse reflection light.

  Here, as an example of an illumination / reflection measurement method close to visual observation in a bright place, an optical system 11 schematically shown in FIG. 2 is exemplified. FIG. 2 shows a diffuse illumination optical system 11 as illumination close to visual observation. The diffuse illumination method is a method of illuminating a sample uniformly from all directions using an integrating sphere. In FIG. 2, the integrating sphere 12 (inner surface is coated with a white paint such as barium sulfate that diffuses and reflects light almost completely. A coated sphere) is installed. The light emitted from the light source 13 is diffused inside the integrating sphere 12 and reflected by the surface of the sample 14. A light trap 15 (in FIG. 2, a jig having a conical cavity is attached to the position of the integrating sphere in the specular reflection direction with respect to the light receiving unit. Is installed in the integrating sphere so that it does not return to the sample surface. An optical system using such a light trap is called an SCE mode (regular reflection removal mode). The luminous reflectance obtained from the reflection spectrum of the sample measured in the SCE mode according to the method described in JIS Z 8722 is referred to as the scattering reflectance Y value.

  In the hard coat film 1 of the present invention, the above-described scattering reflectance Y value is 0.2% or less. When the scattering reflectance Y value exceeds 0.2%, the back surface is treated with black, and the surface of the hard coat layer 3 is visually observed to be whitish. In addition, the hard coat film 1 is arranged on the outermost surface of an image display device that is used in a form in which external light is taken into the display device for visual recognition, and is obtained from each luminance value when a white image and a black image are displayed. From the viewpoint of sufficiently increasing the contrast ratio and obtaining good visibility, the scattering reflectance Y value is preferably 0.15% or less. When the scattering reflectance Y value is more than 0.15% and 0.2% or less, there is no white floating when the back surface is blacked, but the external light is taken into the display device to display an image. Visibility when used may be reduced.

  Such a hard coat film 1 of the present invention has a hardness high enough to prevent the hard coat layer 3 from being scratched or soiled when placed on the outermost surface, and is the most suitable for an image display device. When arranged on the surface, it is possible to obtain good visibility even when used in a transflective and semi-reflective method in which external light is taken in and an image is displayed, and can be obtained at low cost. Furthermore, the hard coat film 1 of the present invention has a hard coat layer 3 that causes problems during handling or processing into an optical element and curl due to curing shrinkage is sufficiently suppressed.

  The present invention also provides a polarizing plate in which the above-described hard coat film 1 of the present invention is bonded to a polarizing film on the transparent support 2 side. Here, a polarizing film is a film having the property of transmitting linearly polarized light that vibrates in a certain direction among light incident perpendicularly to the film surface and absorbing linearly polarized light that vibrates in a direction orthogonal to the film surface. A typical example is a film in which a dichroic dye composed of iodine or a dichroic organic dye is adsorbed and oriented on a polyvinyl alcohol-based resin. Such a polarizing plate of the present invention can be suitably used in an image display device in combination with image display means such as a liquid crystal display element, a plasma display panel, and an EL display. For example, a liquid crystal display device provided with the polarizing plate of the present invention using the above-described hard coat film of the present invention on at least one surface of a liquid crystal display is exemplified.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to these examples.

<Example 1>
An ultraviolet curable resin composition in which the following components were dissolved in ethyl acetate at a solid concentration of 60% by weight was prepared.

Pentaerythritol triacrylate 60 parts by weight Polyfunctional urethanized acrylate (reaction product of hexamethylene diisocyanate and pentaerythritol triacrylate) 40 parts by weight 5 parts by weight of photopolymerization initiator, lucillin TPO (manufactured by BASF, chemical name: 2,4,6-trimethylbenzoyldiphenylphosphine oxide) was added. Furthermore, 0.5 part by weight of Cymac US-150 (manufactured by Toagosei Co., Ltd.) is added as a leveling agent to 100 parts by weight of the solid content of the ultraviolet curable resin composition. A coating solution a for forming a hard coat layer was prepared by diluting with ethyl acetate so as to be 50% by weight.

The coating liquid a was applied onto a 80 μm thick triacetylcellulose (TAC) film so that the coating thickness after drying and curing was 17.7 μm, and dried for 3 minutes in a dryer set at 60 ° C. . Furthermore, the layer of the ultraviolet curable resin composition was cured by irradiating light from a high-pressure mercury lamp having an intensity of 20 mW / cm ^{2 so that} the amount of light converted to h-ray was 200 mJ / cm ² . Thus, as shown in FIG. 1, a transparent hard coat which is a laminate of the hard coat layer 3 which is a cured product of the layer of the ultraviolet curable resin composition and the transparent support 2 made of a TAC film. Film 1 was obtained.

<Example 2>
A hard coat film 1 was obtained in the same manner as in Example 1 except that the coating liquid a was applied so that the coating thickness after drying and curing was 15.1 μm.

<Example 3>
A coating solution b was prepared in the same manner as the coating solution a except that 0.1 part by weight of Cymac US-150 (manufactured by Toa Gosei Co., Ltd.) as a leveling agent was blended. A hard coat film 1 was obtained in the same manner as in Example 1 except that the coating film thickness after curing was 13.4 μm.

<Example 4>
A hard coat film 1 was obtained in the same manner as in Example 3 except that the coating liquid b was applied so that the coating thickness after drying and curing was 11.8 μm.

<Example 5>
A coating solution c was prepared in the same manner as the coating solution a except that 0.01 parts by weight of Cymac US-150 (manufactured by Toa Gosei Co., Ltd.) as a leveling agent was blended. A hard coat film 1 was obtained in the same manner as in Example 1, except that the coating film thickness after curing was 16.4 μm.

<Example 6>
A hard coat film 1 was obtained in the same manner as in Example 5 except that the coating liquid c was applied so that the coating thickness after drying and curing was 11.9 μm.

<Comparative Example 1>
A hard coat film was obtained in the same manner as in Example 1 except that the coating liquid a was applied so that the coating thickness after drying and curing was 35.0 μm.

<Comparative example 2>
A coating solution d was prepared in the same manner as the coating solution a except that Cymac US-150 (manufactured by Toa Gosei Co., Ltd.) as a leveling agent was not blended, and this coating solution d was used for drying and curing. A hard coat film was obtained in the same manner as in Example 1 except that coating was performed so that the coating thickness was 34.3 μm.

<Comparative Example 3>
A coating solution e was prepared in the same manner as the coating solution a except that 1 part by weight of Cymac US-150 (manufactured by Toa Gosei Co., Ltd.) as a leveling agent was blended, and after drying and curing using this coating solution e A hard coat film was obtained in the same manner as in Example 1 except that the coating film thickness was 8.3 μm.

<Comparative example 4>
A hard coat film was obtained in the same manner as in Example 1 except that the coating liquid a was applied so that the coating thickness after drying and curing was 7.1 μm.

<Comparative Example 5>
A hard coat film was obtained in the same manner as in Example 1 except that the coating liquid b was applied so that the coating thickness after drying and curing was 7.8 μm.

<Comparative Example 6>
A hard coat film was obtained in the same manner as in Example 1 except that the coating liquid c was applied so that the coating thickness after drying and curing was 8.2 μm.

<Comparative Example 7>
A hard coat film was obtained in the same manner as in Example 1 except that the coating liquid d was applied so that the coating thickness after drying and curing was 7.5 μm.

〔Evaluation test〕
The following evaluation tests were performed on the hard coat films obtained in Examples 1 to 6 and Comparative Examples 1 to 7 described above.

(1) Thickness of coating film (hard coat layer) About each hard coat film obtained as described above, the thickness of the transparent support alone and the hard coat film using a film thickness meter DIGIMICRO MH-15M (made by Nikon) And the thickness of the hard coat layer was calculated by the following formula.

(Thickness of hard coat layer)
= (Thickness of hard coat film)-(Thickness of transparent support alone)
(2) Haze value In accordance with JIS K 7136, using a haze meter HM-150 manufactured by Murakami Color Research Laboratory, light is incident from the transparent support side of the hard coat film, and emitted from the hard coat layer side. The haze value (%) was measured.

(3) Scattering reflectance Y value Each hard coat film obtained as described above is bonded to a black acrylic plate (Sumipex, manufactured by Sumitomo Chemical Co., Ltd.) on the transparent support side through an adhesive, and evaluated. A sample was used. About these evaluation samples, the scattering reflectance Y value was measured on condition of the following using the spectrocolorimeter CM2002 (made by Konica Minolta Sensing) as the optical system 11 typically shown in FIG.

Mode: SCE mode (with light trap)
Lighting: Diffuse lighting method
(According to JIS Z 8722-1982 4.3.1 (3) condition c)
Light receiving optical system: set angle of light receiving part and sample normal direction to 8 ° Light source: C light source (see JIS Z8720)
(4) Coating surface state The surface state of the hard coat layer on each hard coat film obtained as described above is visually confirmed in a normal indoor environment for defects such as waving and interference unevenness. It was evaluated as follows.

○: Almost mirror surface, no noticeable defects,
X: The defect of interference nonuniformity can be confirmed among waves.

(5) Pencil hardness The transparent support side of each hard coat film obtained as described above was placed on a glass plate, and the pencil hardness of the hard coat layer surface was measured according to JIS K-5400-1990. However, the test load was 500 g.

(6) Curl Each hard coat film obtained as described above was cut into 10 cm squares, placed on the glass plate so that the hard coat layer was on top, and the lifting length from the glass plate at the four corners (mm ) Was measured, the average value was obtained, and evaluated as follows.

○: The average value is 20 mm or less,
X: The average value exceeds 20 mm.

(7) Bending resistance Each hard coat film obtained as described above was cut into 10 cm square, wound around a cylinder having an outer diameter of 5 to 50 mm so that the transparent support was on the inside, and held for 10 seconds. The minimum diameter at which no cracks or cracks occur in the hard coat film was defined as bending resistance.

(8) Evaluation of reflection contrast ratio From FOMA N903i (manufactured by NEC Corporation), which is a mobile phone in a transflective liquid crystal drive mode, the polarizing plate bonded to the outermost surface is peeled off, and the position after peeling. On the phase difference film surface, Sumikaran SRW832 (manufactured by Sumitomo Chemical Co., Ltd.) was bonded via an adhesive so that the absorption axis coincided with the absorption axis of the original polarizing plate. Each hard coat film obtained as described above was bonded via an adhesive so that the hard coat layer was on the surface, and an evaluation sample was obtained.

  With respect to the evaluation sample thus obtained, the reflection contrast ratio was evaluated using a jig 21 having an integrating hemisphere and a light source unit as schematically shown in FIGS. 3 is a perspective view of the jig 21, FIG. 4 (a) is a bottom view, FIG. 4 (b) is a front view, and FIG. 4 (c) is a side view. The integrating hemisphere 22 is a diffusion surface with barium sulfate applied to the inner wall surface. The evaluation sample 24 is illuminated from the light source 23 through the integrating hemisphere 22, and the luminance of the surface of the evaluation sample 24 is measured by the luminance meter 25. As the luminance meter 25, a luminance meter “BM5A” type (manufactured by Topcon Corporation) was used. Here, the surface of the evaluation sample 24 is located at the center of the cross section of the integrating hemisphere 22, and the normal direction thereof is inclined by 8 ° with respect to the normal direction of the cross section. The normal direction of the evaluation sample 24 surface is designed to coincide with the measurement optical axis of the luminance meter 25. As shown in FIG. 4, the evaluation sample 24 was installed, the luminance in black display and white display in the reflection mode (the state where the backlight of the mobile phone was not turned on) was measured, and the contrast was calculated. However, at this time, the reflection contrast ratio is represented by the ratio of the luminance in the white display state to the luminance in the black display state.

  Table 1 shows the results of the evaluation tests described above for Examples 1 to 6 and Comparative Examples 1 to 7.

  From Table 1, in Examples 1-6 and Comparative Examples 1 and 2, it turns out that sufficient pencil hardness is obtained by the coating-film thickness (thickness of a hard-coat layer) being 10 micrometers or more. However, in Comparative Examples 1 and 2, since the coating thickness exceeds 30 μm, the curl is strong and the bending resistance is weak. In Comparative Examples 3 to 7, the coating thickness is less than 10 μm, and the desired hardness is not obtained. In Comparative Examples 1 and 3, since the scattering reflectance Y value exceeds 0.2%, the reflection contrast ratio is lowered, which is not preferable. Furthermore, since the leveling agent is not mix | blended in the comparative examples 2 and 7, the smoothness of a coating-film surface is inadequate and is not preferable.

<Example 7>
A coating solution f was prepared in the same manner as the coating solution a except that it was diluted so that the solid content concentration of the ultraviolet curable resin was 30% by weight. Using this coating solution f, the coating thickness after drying and curing A hard coat film 1 was obtained in the same manner as in Example 1 except that the coating was applied so as to be 12.1 μm.

<Example 8>
A coating solution g was prepared in the same manner as the coating solution a except that the solid content concentration of the UV curable resin was 70% by weight, and the coating thickness after drying and curing was prepared using this coating solution g. A hard coat film 1 was obtained in the same manner as in Example 1 except that the coating was applied so as to be 15.5 μm.

<Comparative Example 8>
A coating solution h was prepared in the same manner as the coating solution a except that the solid content concentration of the UV curable resin was 20% by weight, and the coating thickness after drying and curing was prepared using this coating solution h. A hard coat film was obtained in the same manner as in Example 1 except that the coating was applied so as to be 8.3 μm.

<Comparative Example 9>
The coating liquid i was prepared in the same manner as the coating liquid a except that the solid content concentration of the UV curable resin was 80% by weight, and the coating film thickness after drying and curing was prepared using this coating liquid i. A hard coat film was obtained in the same manner as in Example 1 except that the coating was applied so as to be 16.3 μm.

<Comparative Example 10>
A hard coat film was obtained in the same manner as in Example 1 except that the coating liquid a was applied so that the coating thickness after drying and curing was 15.5 μm and dried at 100 ° C. for 2 minutes.

For the hard coat film obtained respectively in Examples 7, 8 and Comparative Examples 8 to 10, film thickness in a similar manner as described above, the scattering reflectance Y value, coated surface state, the pencil hardness and the reflection co cement last ratio evaluated. The results of Examples 7 and 8 and Comparative Examples 8 to 10 are shown in Table 2 together with the results of Example 1.

From the results shown in Table 2, in Examples 1, 7, and 8, a hard coat layer having a coating film surface state with a thickness of 10 μm or more is obtained by setting the solid content concentration of the coating solution to 30 to 70 wt%. I understand that I was able to. On the other hand, in Comparative Example 8, since the solid concentration of the coating solution is as low as 20% by weight, a sufficient coating thickness cannot be obtained. In Comparative Example 9, the solid concentration of the coating solution is 80% by weight. Since it is high and%, streaky unevenness along the coating direction occurs after the coating solution is cured, resulting in a coating film that impairs the appearance. In Comparative Example 10, by making the drying temperature of the coating liquid and 100 ° C., whitening phenomenon was observed on the surface of the coating film, since the fine unevenness occurs, reflected co cement last ratio is degraded and undesirable .

It is sectional drawing which shows typically the hard coat film 1 of a preferable example of this invention. It is a figure which shows typically the optical system 11 used suitably in order to measure a scattering reflectance Y value. It is a perspective view which shows typically the jig 21 used for evaluation of reflection contrast ratio. It is a figure which shows typically the jig 21 shown in FIG. 3, Fig.4 (a) is a bottom view, FIG.4 (b) is a front view, FIG.4 (c) is a side view.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Hard coat film, 2 Transparent support body, 3 Hard coat layer, 11 Optical system, 12 Integrating sphere, 13 Light source, 14 Sample, 15 Light trap, 21 Jig, 22 Integral hemisphere, 23 Light source, 24 Evaluation sample, 25 Luminance meter .

Claims (5)

A transparent support;
A hard coat layer made of a cured product of a curable resin composition containing an ionizing radiation curable resin and a leveling agent, formed on a thickness of 10 to 30 μm on at least one surface of the transparent support;
The curable resin composition contains ethyl acetate as a solvent, an ionizing radiation curable resin, and a leveling agent having at least one of a polysiloxane structure or a fluorine-containing group, and the ionizing radiation curable resin 100 weight. A coating solution containing 0.01 to 0.5 parts by weight of the leveling agent per part and diluted so that the concentration of the ionizing radiation curable resin is 30 to 70% by weight;
The hard coat layer is formed by applying the coating solution on the transparent support, drying at a temperature in the range of 40 to 80 ° C., and then curing by irradiation with ionizing radiation.
A hard coat film having a scattering reflectance Y value of 0.2% or less. The hard coat layer, the pencil hardness of Ru der least 4H, hard coat film according to claim 1. Ionizing radiation-curable resin constituting the curable resin composition, Ru (meth) ultraviolet-curable resin der acrylate-based hard coat film according to claim 1 or 2. A method for producing a hard coat film in which a hard coat layer made of a cured product of a curable resin composition containing an ionizing radiation curable resin and a leveling agent is formed on the surface of a transparent support,
The solvent includes ethyl acetate as a solvent , ionizing radiation curable resin, and a leveling agent having at least one of a polysiloxane structure or a fluorine-containing group, and the leveling agent is added to 0.1 part by weight of 100 parts by weight of the ionizing radiation curable resin. 01 to 0.5 in a proportion of parts, a coating solution concentration of the ionizing radiation-curable resin is diluted to 30 to 70 wt%, it was applied onto the transparent support, 40 to 80 ° C. The hard-coat film manufacturing method of forming a hard-coat layer with the thickness of 10-30 micrometers by drying at the temperature within the range of this, and then making it harden | cure by ionizing radiation irradiation.   The polarizing plate with which the hard coat film in any one of Claims 1-3 is bonded by the polarizing film on the transparent support side.

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