JP2007152937A - Hard coat film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hard coat film excellent in adhesiveness with a base film, wear resistance, and the long-term preservation stability of a raw material coating agent. <P>SOLUTION: The hard coat film comprises a hard coat layer on at least one side of a base film, wherein the hard coat layer comprises a curing composition including three components: (i) a multifunctional acrylate, (ii) a melamine based cross linking agent, (iii) a low viscosity acrylate having at least two ethylene unsaturated double bonds in one molecule and having a viscosity of not more than 50 mPa s at 25°C and in which the difference (ΔSP) of a solubility parameter with the base film is not more than 3.0. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a hard coat film, and more particularly, the present invention relates to a hard coat coating material that has extremely good adhesion between a hard coat layer and a substrate, is excellent in wear resistance, and serves as a raw material for the hard coat layer. The present invention relates to a hard coat film excellent in long-term storage stability.

  In recent years, the market for monitors and large flat-screen TVs using technologies such as liquid crystal, plasma, and rear production has grown significantly. High performance films that meet the requirements of members applied to these have been developed. Among them, the antireflection film that prevents the reflection of the screen surface is provided with a hard coat layer for preventing scratches based on a triacetate film or a polyester film, a high refractive index layer, and a low refractive index layer on it. Most of them provide an antireflection function by canceling interfacial reflection between layers.

  In addition to the optical function, the hard coat film applied to these uses needs to satisfy properties such as adhesion between the hard coat layer and the base film and wear resistance.

  As a study for improving adhesiveness, for example, when a hard coat layer is laminated on a polyester film, a method in which a hard coat layer is provided on an easy adhesion treatment film provided with a primer layer has been performed. Adhesion is improved when a primer layer is provided, but the refractive index of the base polyester film and the primer layer is often different, and furthermore, a difference in refractive index between the hard coat layer and the primer layer is generated, which causes interference. Stripes occur, causing glare and partial iris reflection when viewed from a certain angle, which is extremely poor in visibility when used for display applications. In order to improve this phenomenon, the coating film thickness accuracy is improved, the refractive index of the hard coat layer is increased and the refractive index difference is reduced (see Patent Document 1), and the surface of the base film is subjected to hot pressing. A method of roughening the surface and providing a hard coat layer on the surface (Patent Document 2), applying a hard coat agent using a solvent that dissolves the base film, and dissolving or swelling the base film to make the reflective interface less A method for reducing interference fringes (Patent Document 3) has been proposed.

  However, there is a limit to the accuracy of the coating thickness, and there is a limit to increasing the refractive index with only the resin component. Moreover, even if the interference fringes can be reduced by the method using the hot press, the visibility becomes poor. Furthermore, in the dissolution and swelling methods, applicable resins are limited, and highly biaxially oriented polyester films are limited to special solvents such as orthochlorophenol, and the working environment is extremely bad.

  In order to improve the above-described drawbacks, there has been proposed a method (Patent Document 4) in which a hard coat layer is applied in a film-forming process without providing a primer layer and is directly cured by curing in a heat treatment process.

However, since this formulation uses a catalyst, the long-term storage characteristics of the hard coat coating liquid used in the production of the hard coat film are poor, and depending on the storage conditions, there is a concern that the viscosity of the coating liquid may increase and the occurrence of coating-derived foreign matter may occur. Further improvements have been expected in advanced display applications where a surface with extremely small thickness irregularities and defects due to foreign matters is being demanded.
JP 2002-241527 A JP-A-8-197670 JP 2003-205563 A JP-A-2005-41205

  An object of this invention is to provide the hard coat film which is excellent in adhesiveness with a base film, and shows favorable abrasion resistance. Another object of the present invention is to improve the long-term storage stability of a coating for producing a hard coat, which is currently a problem.

In the present invention, the hard coat layer is composed of (i) a polyfunctional acrylate, (ii) a melamine-based crosslinking agent, and (iii) a viscosity parameter at 25 ° C. of 50 mPa · s or less and a difference in solubility parameter from the base film (ΔSP) The hard which overcomes the above-mentioned problems by applying a curable composition whose main component is a low-viscosity acrylate having two or more ethylenically unsaturated double bonds in one molecule having a molecular weight of 3.0 or less A coated film is provided.

  With the constitution of the hard coat film of the present invention, it is excellent in adhesion between the base film and the hard coat layer and excellent in abrasion resistance without using an easy-adhesion layer that may adversely affect optical properties. Film can be obtained, and can be applied to a display film. Moreover, since the pot life of the hard coat coating agent for producing a hard coat film is greatly improved by the present invention, it is possible to provide a hard coat film production technique that is excellent in terms of production stability and cost performance.

  The hard coat film of the present invention has a structure in which a hard coat layer is laminated on at least one side of a base film.

  The base film in the present invention is a film that can be formed by melt film formation or solution film formation. Specific examples thereof include films made of polyester, polyolefin, polyamide and polycarbonate. Of these, a film made of a thermoplastic resin, particularly a polyester, particularly excellent in transparency, mechanical strength and dimensional stability, is preferably used.

  Examples of the polyester preferably used in the present invention include polyethylene terephthalate, polyethylene naphthalate, polypropylene terephthalate, polybutylene terephthalate, and polypropylene naphthalate, and a mixture of two or more of these may be used. Further, it may be a polyester in which these and other dicarboxylic acid components or diol components are copolymerized. In this case, in the film in which the crystal orientation is completed, the crystallinity is preferably 25% or more, more preferably Is preferably 30% or more, more preferably 35% or more. When the crystallinity is less than 25%, dimensional stability and mechanical strength tend to be insufficient. The degree of crystallinity can be measured by a Raman spectrum analysis method.

  When the above-described polyester is used, its intrinsic viscosity (measured in o-chlorophenol at 25 ° C. according to JIS K7367) is preferably 0.4 to 1.2 dl / g, more preferably 0.5 to 0.8 dl / g.

  The base film used in the present invention may be a composite film having a laminated structure of two or more layers. As the composite film, for example, a composite film that is substantially free of particles in the inner layer portion and provided with a layer containing particles in the surface layer portion, has coarse particles in the inner layer portion, and fine particles in the surface layer portion. And a composite film having a layer in which the inner layer portion contains fine bubbles. Further, the composite film may be a chemically different polymer or an identical polymer in the inner layer portion and the surface layer portion. When used for a display which is the intended use of the present invention, it is preferable in terms of optical properties such as transparency that the substrate film does not contain particles.

  The base film in the present invention has sufficient thermal stability of the film, particularly dimensional stability and mechanical strength, and from the viewpoint of improving the flatness, in the state where the hard coat layer is provided, biaxial stretching is performed. A crystal-oriented film is preferred. The crystal orientation by biaxial stretching means that the thermoplastic resin film before unstretched, that is, before the crystal orientation is completed, is preferably stretched about 2.5 to 5 times in the longitudinal direction and the width direction, respectively, and then subjected to heat treatment. A crystal orientation that has been completed and that shows a biaxial orientation pattern by wide-angle X-ray diffraction.

  The thickness of the base film used in the present invention is appropriately selected according to the use for which the hard coat film of the present invention is used. From the viewpoint of mechanical strength and handling properties, it is preferably 10 to 500 μm, more Preferably it is 20-300 micrometers.

  The base film of the present invention may contain various additives, resin compositions, cross-linking agents and the like within a range that does not impair the effects of the present invention. For example, antioxidants, heat stabilizers, ultraviolet absorbers, organic and inorganic particles (for example, silica, colloidal silica, alumina, alumina sol, kaolin, talc, mica, calcium carbonate, barium sulfate, carbon black, zeolite, titanium oxide, Metal fine powders), pigments, dyes, antistatic agents, nucleating agents, acrylic resins, polyester resins, urethane resins, polyolefin resins, polycarbonate resins, alkyd resins, epoxy resins, urea resins, phenol resins, silicone resins, rubber resins , Wax composition, melamine crosslinking agent, oxazoline crosslinking agent, methylolated, alkylolized urea crosslinking agent, acrylamide, polyamide, epoxy resin, isocyanate compound, aziridine compound, various silane coupling agents, various titanates And the like can be mentioned system coupling agent.

  In particular, when used for a plasma display, the base film preferably has an ultraviolet cut function, and preferably contains an ultraviolet absorber, in order to use a dye having a color correction or near infrared cut function.

  Preferred examples of the ultraviolet absorber include salicylic acid compounds, benzophenone compounds, benzotriazole compounds, cyanoacrylate compounds, benzoxazinone compounds, and cyclic imino ester compounds, but 380 nm to 390 nm. Of these, benzoxazinone compounds are most preferred from the viewpoints of UV-cutting property and color tone. These compounds may be used alone or in combination of two or more. Moreover, combined use of stabilizers, such as HALS (hindered amine light stabilizer) and antioxidant, is more preferable.

  Examples of benzoxazinone-based compounds that are preferable materials include 2-p-nitrophenyl-3,1-benzoxazin-4-one and 2- (p-bezoylphenyl) -3,1-benzoxazine-4. -One, 2- (2-naphthyl) -3,1-benzoxazin-4-one, 2-2'-p-phenylenebis (3,1-benzoxazin-4-one), 2,2 '-( 2,6-naphthylene) bis (3,1-benzoxazin-4-one) and the like can be exemplified. The amount of these compounds added is preferably 0.5 to 5% by weight, preferably 1 to 5% by weight, in the base film.

  Further, it is preferable to use a cyanoacrylate-based tetramer compound in combination in order to impart further excellent light resistance. The cyanoacrylate tetramer compound is preferably contained in the base film in an amount of 0.05 to 2% by weight. The cyanoacrylate-based tetramer compound is a compound based on a tetramer of cyanoacrylate, such as 1,3-bis (2′cyano-3,3-diphenylacryloyloxy) -2, 2-bis-. (2 'cyano-3,3-diphenylacryloyloxymethylpropane). When using together with this, it is suitable to add 0.3 to 3 weight% of the above-mentioned ultraviolet absorber in a base film.

  The hard coat film of the present invention preferably has a transmittance at a wavelength of 380 nm of 5% or less, and can be achieved by the addition of the above-described ultraviolet absorber. Thereby, when especially applying to the member for plasma displays, a base film, a dye pigment | dye, etc. can be protected from an ultraviolet-ray.

  The hard coat film of the present invention preferably has a total light transmittance of 85% or more and a haze of 2% or less, more preferably a total light transmittance of 90% or more and a haze of 1.5% or less. Is good. By having such characteristics, the visibility and sharpness of the image can be improved when used for a display member. For this purpose, it is effective not to contain inorganic or organic particles in the base film and the hard coat layer.

  Further, the hard coat film of the present invention preferably has a transmission b value of 1.5 or less, more preferably 1.0 or less. If the transmission b value exceeds 1.5, the film itself appears slightly yellowish, which may impair the sharpness of the image. This function can be achieved by adding the aforementioned UV absorber to the base film or hard coat layer, but in the case of addition to the hard coat layer, the surface hardness may be reduced depending on the amount added. Therefore, addition to the base film is preferable.

In the hard coat film of the present invention, a hard coat layer is laminated on at least one side of the base film, and this hard coat layer is formed by (i) a polyfunctional acrylate, (ii) a melamine-based crosslinking agent, (iii) ) Low viscosity having two or more ethylenically unsaturated double bonds in one molecule having a viscosity at 25 ° C. of 50 mPa · s or less and a difference in solubility parameter from the base film (ΔSP) of 3.0 or less Acrylate is used.
First, the polyfunctional acrylate will be described. The polyfunctional acrylate is a main component that forms the hard coat layer, and has a role of increasing the hardness of the hard coat layer. Here, the main component means that 50% by weight or more is contained in the hard coat layer forming composition.

  In the present invention, the polyfunctional acrylate refers to 4 or more, more preferably 5 or more (meth) acryloyloxy groups in one molecule (provided that “... (Meth) acryl ...” in this specification). Is a monomer, oligomer, or prepolymer having "... acrylic ... or ... meta acrylic ...". As monomers, oligomers and prepolymers having 4 or more (meth) acryloyloxy groups in one molecule, there are 4 hydroxyl groups of a polyhydric alcohol having 4 or more alcoholic hydroxyl groups in 1 molecule. The compound etc. which become the esterified substance of the above (meth) acrylic acid can be mentioned.

  Specific examples include pentaerythritol tetra (meth) acrylate, dipentaerythritol tetra (meth) acrylate, dipentaerythritol penta (meth) acrylate, dipentaerythritol hexa (meth) acrylate, and the like. These may be used alone or in combination of two or more.

  The polyfunctional acrylate component in the solid content of the hard coat layer is 40 to 95% by weight, preferably 50 to 80% by weight. If the use ratio is too small, the hardness of the hard coat film is low, and if it is too large, cracks are likely to occur.

  In the present invention, a melamine-based crosslinking agent is used as an essential component for the purpose of expressing extremely excellent adhesiveness. The type of melamine-based crosslinking agent is not particularly limited, but melamine, a methylolated melamine derivative obtained by condensing melamine and formaldehyde, a compound partially or completely etherified by reacting methylolated melamine with a lower alcohol, or these A mixture or the like can be used. As the melamine-based crosslinking agent, a monomer, a condensate composed of a multimer of two or more, or a mixture thereof can be used. As the lower alcohol used for etherification, methyl alcohol, ethyl alcohol, isopropyl alcohol, n-propyl alcohol, n-butanol, isobutanol and the like can be used. The functional group has an imino group, a methylol group, or an alkoxymethyl group such as a methoxymethyl group or a butoxymethyl group in one molecule, and an imino group type methylated melamine, a methylol group type melamine, or a methylol group type methylated melamine. And fully alkyl methylated melamine. Among them, methylolated melamine and fully alkylated melamine are preferable in terms of adhesiveness.

  The amount of the melamine-based crosslinking agent is not particularly limited, but is 2 to 50 parts by weight, preferably 5 to 40 parts by weight, and more preferably 10 to 35 parts by weight with respect to 100 parts by weight of the polyfunctional acrylate in the solid content of the hard coat layer. The part is preferable in terms of the balance between adhesion and hardness. When the addition amount is less than this range, the adhesiveness is lowered, and when it is more, the hardness is lowered.

Further, the present invention has a great feature in that an acid catalyst often used for the purpose of accelerating the curing of melamine is not added.
Examples of the acid catalyst include p-toluene sulfonic acid, dodecylbenzene sulfonic acid, dimethyl pyrophosphoric acid, styrene sulfonic acid and derivatives thereof. When a coating liquid containing these acid catalysts is used, When stored for a long period of time or at high temperatures, the viscosity of the coating liquid increases and the coating properties deteriorate, or a cured product is generated in the coating liquid and the hard coat layer is coated and cured. In some cases, foreign matter is generated and becomes a bright spot. In the conventional invention, these acid catalysts are blocked to make them inactive in the coating liquid, and activated in the heat curing process after coating, thereby eliminating bright spots caused by foreign matters that are problematic in optical applications. ing. Although the generation of foreign matters is suppressed by this method, the long-term storage stability and high-temperature stability of the coating liquid remain a problem. The present invention improves adhesion without using a catalyst.

  Specifically, in the present invention, as an adhesion improving component, two in one molecule having a viscosity at 25 ° C. of 50 mPa · s or less and a difference in solubility parameter from the base film (ΔSP) of 3.0 or less. The low viscosity acrylate having the above ethylenically unsaturated double bond is used. The viscosity at 25 ° C. can be measured using an apparatus capable of measuring a normal solution viscosity, such as a B-type viscometer.

  Such low viscosity acrylates include ethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, 1,4-butanediol di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth). ) Acrylate, tetraethylene glycol di (meth) acrylate, pentaethylene glycol di (meth) acrylate, hexaethylene glycol di (meth) acrylate, heptaethylene glycol di (meth) acrylate, octaethylene glycol di (meth) acrylate, nonaethylene Examples include, but are not limited to, glycol di (meth) acrylate, dipropylene glycol di (meth) acrylate, and polyethylene glycol di (meth) acrylate. Not. Particularly preferred is polyethylene glycol di (meth) acrylate.

  The amount of the low-viscosity acrylate is not particularly limited, but is 8 to 50 parts by weight, preferably 8 to 40 parts by weight, more preferably 16 to 25 parts by weight with respect to 100 parts by weight of the polyfunctional acrylate in the solid content of the hard coat layer. It is preferable in terms of the balance between adhesiveness and hardness. When the addition amount is less than this range, the adhesiveness is lowered, and when it is more, the hardness is lowered.

  The viscosity at 25 ° C. of the low viscosity acrylate of the present invention is 50 mPa · s or less, preferably 40 mPa · s or less, more preferably 30 mPa · s or less. When the viscosity is outside this range, the adhesive force with the base film is lowered.

  Further, the difference in solubility parameter (ΔSP) from the base film in the low viscosity acrylate of the present invention is 3.0 or less. When ΔSP is outside this range, the adhesion between the base film and the hard coat layer is lowered.

  The low-viscosity acrylate of the present invention has the effect of significantly improving the adhesion between the base film and the hard coat layer when used in combination with a melamine-based crosslinking agent. This is because the hard coat layer can only interact with the surface of the substrate in the melamine-based crosslinking agent system, whereas the substrate in the melamine-based crosslinking agent + low-viscosity acrylate (small ΔSP value) system. This is thought to be due to the interaction with the inside. That is, a low-viscosity acrylate with a small ΔSP is excellent in affinity with the base film, has low viscosity and excellent molecular flexibility and mobility, and therefore has high permeability to the base film, and the coating surface penetrates the base material layer. It is estimated that the adhesion is improved by the anchor effect. In addition, since the mobility is high and the acryloyl group is highly reactive, the effect of improving the adhesiveness by increasing the degree of crosslinking in the hard coat layer can also be considered.

In the present invention, (i) a polyfunctional acrylate, (ii) a melamine-based crosslinking agent, and (iii) a low-viscosity acrylate are used as main components, but various minor components can be used for the purpose of improving characteristics.
For example, the following (meth) acrylates can also be used for the purpose of reducing the viscosity of the coating liquid (improving coating properties) and improving the brittleness of the hard coat layer.

  (A) C2-C12 alkylene glycol (meth) acrylic acid diesters: neopentyl glycol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, and the like.

(B) Ethylene oxide of bisphenol A or hydride of bisphenol A and (meth) acrylic acid diesters of propylene oxide adducts: 2,2′-bis (4-acryloxyethoxyphenyl) propane, 2,2′-bis ( 4-acryloxypropoxyphenyl) propane, etc.
(C) Two or more in a molecule obtained by reacting a terminal isocyanate group-containing compound obtained by reacting a diisocyanate compound and two or more alcoholic hydroxyl group-containing compounds in advance with an alcoholic hydroxyl group-containing (meth) acrylate. Urethane (meth) acrylates having a (meth) acryloyloxy group.

  (D) Epoxy (meth) acrylates having two or more (meth) acryloyloxy groups in the molecule obtained by reacting a compound having two or more epoxy groups in the molecule with acrylic acid or methacrylic acid.

 (E) compounds having one ethylenically unsaturated double bond in the molecule: methyl (meth) acrylate, ethyl (meth) acrylate, n- and i-propyl (meth) acrylate, n-, sec-, and t-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate, methoxyethyl (meth) acrylate, ethoxyethyl (meth) acrylate, hydroxyethyl (meth) acrylate, polyethylene Glycol mono (meth) acrylate, polypropylene glycol mono (meth) acrylate, glycidyl (meth) acrylate, tetrahydrofurfuryl (meth) acrylate, N-hydroxyethyl (meth) acrylamide, N-vinylpyrrolidone, N Vinyl-3-methylpyrrolidone, etc. N- vinyl-5-methyl pyrrolidone. These monomers may be used alone or in combination of two or more.

  In the present invention, a reactive diluent can be used. A reactive diluent is a coating agent component having a group that reacts with a monofunctional or polyfunctional acrylic oligomer as well as serving as a solvent in the coating process as a coating medium. It will be.

  Specific examples of these acrylic oligomers and reactive diluents are as follows: Shinzo Yamashita, Tosuke Kaneko, “Crosslinking Agent Handbook”, Taiseisha 1981, pp. 267-275, 562-593. However, the present invention is not limited to these.

  Commercially available polyfunctional acrylates include Mitsubishi Rayon Co., Ltd. (trade name “Diabeam” series, etc.), Nagase Sangyo Co., Ltd. (trade name “Denacol” series, etc.), Shin-Nakamura Co., Ltd. (trade name). (“NK ester” series, etc.), Dainippon Ink and Chemicals Co., Ltd .; (trade name “UNIDIC” series, etc.), Toa Gosei Chemical Industries Co., Ltd. (trade name “Aronix” series, etc.), Nippon Oil & Fats Corporation; Names such as “Blemmer” series), Nippon Kayaku Co., Ltd .; (Product name “KAYARAD” series, etc.), Kyoeisha Chemical Co., Ltd. (Product names “Light Ester” series, “Light acrylate” series, etc.) can do.

  Further, in the present invention, as a hard coat layer modifier, a coating property improver, an antifoaming agent, a thickener, an antistatic agent, inorganic particles, organic particles, an organic lubricant, an organic polymer compound, Ultraviolet absorbers, light stabilizers, dyes, pigments or stabilizers can be used, and these are used as a composition component of the coating layer constituting the hard coat layer within a range not impairing the reaction due to active rays or heat. The characteristics of the hard coat layer can be improved depending on the application.

  In the present invention, as a method of curing the hard coat composition, for example, a method of irradiating ultraviolet rays as active rays or a high temperature heating method can be used. For this purpose, a so-called in-line coating method in which a hard coat layer is provided in the base film forming step and cured in a heat treatment step is more preferable. For example, when a biaxially stretched polyester film is used as a substrate, a higher adhesive force is expressed by applying a hard coat coating to a substrate film in a state of low crystallinity before heat setting. This is presumed to be because the permeability of the coating material into the base film is good.

  The hard coat layer forming composition used in the present invention has a thermal polymerization prevention such as hydroquinone, hydroquinone monomethyl ether or 2,5-t-butyl hydroquinone to prevent thermal polymerization during production and dark reaction during storage. It is desirable to add an agent. The addition amount of the thermal polymerization inhibitor is preferably 0.005 to 0.1 parts by weight with respect to the solid content of the hard coat layer.

  In forming the hard coat layer of the present invention, it is preferable to use a leveling agent to smooth the surface of the hard coat layer. Typical leveling agents include silicone-based, acrylic-based, and fluorine-based agents, but when only smoothness is required, silicone-based is effective with a small amount of addition. As the silicone leveling agent, polydimethylsiloxane as a basic skeleton and a polyoxyalkylene group added (for example, SH190 manufactured by Toray Dow Corning Silicone Co., Ltd.) is preferable.

  On the other hand, in the case where a laminated film is further provided on the hard coat layer, it is necessary that the coating properties and adhesiveness of the laminated film are not impaired. In that case, it is preferable to use an acrylic leveling agent. As such a leveling agent, “ARUFON-UP1000 series, UH2000 series, UC3000 series (trade name): manufactured by Toagosei Co., Ltd.” or the like is preferably used. The leveling agent is preferably added in an amount of 0.01 to 10 parts by weight in the hard coat layer forming composition.

  In the present invention, it is preferable not to interpose an adhesive layer between the base film and the hard coat layer. When the adhesive layer is interposed, interference fringes may be generated due to a difference in refractive index from the base film or the hard coat layer, or the adhesive layer may be deteriorated by ultraviolet rays or may have poor durability in high temperature and high humidity conditions. A hard coat composition coating agent is applied to at least one surface of a thermoplastic polyester film that has been uniaxially stretched and crystal orientation is incomplete, and then stretched in a direction perpendicular to the uniaxial stretch direction through a preheating step. In addition, a manufacturing method in which heat setting is performed and, if necessary, active ray irradiation treatment is preferable. By applying this method, the hard coat layer can be highly adhered to the base film without providing a primer layer on the base film. Further, the interference fringes can be reduced by applying before the crystal orientation is completed.

  Next, an example of the method for producing a hard coat film of the present invention will be described using polyethylene terephthalate (hereinafter abbreviated as PET) as an example of the base film, but is not limited thereto.

  A PET pellet (intrinsic viscosity 0.62 dl / g) containing 0.2% by weight of silica particles having an average particle diameter of 0.3 μm was vacuum-dried at 180 ° C. for about 2 hours to sufficiently remove moisture, and then an extruder. And melt extruded at a temperature of 260 to 300 ° C., and formed into a sheet form from a T-shaped die. The sheet-like material thus obtained is cooled and solidified on a mirror-like cooling drum to obtain an unstretched sheet. At this time, it is preferable to use an electrostatic application method for the purpose of improving the adhesion to the cast drum. Thereafter, the obtained unstretched sheet is stretched 3 to 4 times in the longitudinal direction with a roll group heated to 70 to 120 ° C. Next, a hard coat layer-forming coating comprising a polyfunctional acrylate, a melamine-based crosslinking agent, a low viscosity acrylate, a leveling agent, etc. is applied to the surface of the film thus uniaxially stretched, and then both ends of the film are applied. Guide to the tenter while gripping with the clip. After preheating to 70 to 110 ° C. in a tenter, the film is stretched about 3 to 4 times at 80 to 125 ° C. in the width direction. The laminated film stretched in the width direction is further subjected to a heat treatment for completing the crystal orientation of the base film and the coating film curing while performing a relaxation treatment of 3 to 10% in an atmosphere of 220 to 240 ° C.

  The hard coat film of the present invention thus obtained can be provided with a hard coat layer all at once in the film forming process, so that the productivity is high, the surface hardness is high, and the adhesion between the hard coat layer and the base film is achieved. It is excellent in visibility, has almost no foreign matter defects, and has excellent visibility, so that it can be used in a wide range of applications. In particular, it is suitably used as an antireflection film substrate for displays, a substrate for touch panels, a substrate for windowing, a substrate for nameplates, and the like.

  Various coating methods such as a reverse coating method, a gravure coating method, a rod coating method, a bar coating method, a die coating method, or a spray coating method can be used as a means for applying the hard coat layer forming coating agent.

  As the heat necessary for the thermosetting used in the present invention, air heated to at least 200 ° C. or inert gas using a steam heater, an electric heater, an infrared heater, a far-infrared heater or the like, an inert gas, a slit nozzle The heat | fever given by spraying on a base film and a coating film using is mentioned, The heat | fever by the air heated to 220 degreeC or more is especially preferable. Examples of the active rays used as necessary in the present invention include electromagnetic waves that polymerize acrylic vinyl groups such as ultraviolet rays, electron beams and radiation (α rays, β rays, γ rays, etc.). Ultraviolet light is convenient and preferred. As the ultraviolet ray source, an ultraviolet fluorescent lamp, a low pressure mercury lamp, a high pressure mercury lamp, an ultra high pressure mercury lamp, a xenon lamp, a carbon arc lamp, or the like can be used. Moreover, when irradiating actinic radiation, if it irradiates under a low oxygen concentration, it can harden | cure efficiently. Furthermore, the electron beam system is advantageous in that the apparatus is expensive and needs to be operated under an inert gas, but it is not necessary to include a photopolymerization initiator or a photosensitizer in the coating layer. is there.

  Although the thickness of a hard-coat layer should just be determined according to a use, 1 micrometers-20 micrometers are preferable normally, More preferably, they are 2 micrometers-10 micrometers. When the thickness of the hard coat layer is less than 1 μm, even if it is sufficiently cured, the surface hardness is not sufficient because it is too thin, and the surface tends to be scratched. On the other hand, when the thickness exceeds 20 μm, The cured film tends to crack due to curling during bending or stress such as bending.

  Moreover, you may provide printing layers, such as a pattern, in the outermost layer of a hard-coat layer in the range which does not impair the effect of this invention.

  Further, the obtained hard coat film can be used by being bonded to various functional films by various methods, and an adhesive layer can be laminated on the other surface, or a conductive layer can be provided.

  For example, the hard coat film of the present invention is bonded to a counterpart material using various adhesives on the opposite side of the hard coat layer, and the hard coat layer such as wear resistance and scratch resistance is attached to the counterpart material. It is also possible to use it with the above functions. The adhesive used at this time is not particularly limited as long as it is an adhesive that adheres two objects by its adhesive action, and an adhesive made of rubber, acrylic, silicone or polyvinyl ether is used. it can.

  Furthermore, the pressure-sensitive adhesive is roughly classified into two types, a solvent-type pressure-sensitive adhesive and a solventless pressure-sensitive adhesive. Solvent-type pressure-sensitive adhesives excellent in dryness, productivity, and processability are still mainstream, but in recent years, they are changing to solvent-free pressure-sensitive adhesives in terms of pollution, energy saving, resource saving, safety, and the like. Among these, it is preferable to use an actinic radiation curable pressure sensitive adhesive that is a pressure sensitive adhesive that is cured in seconds by irradiation with actinic radiation and has excellent properties such as flexibility, adhesion, and chemical resistance.

  Specific examples of the actinic radiation curable acrylic pressure-sensitive adhesive can be referred to the Japan Adhesive Society, “Adhesive Data Book”, published by Nikkan Kogyo Shimbun, 1990, pages 83 to 88. It is not limited to. Commercially available multifunctional acrylic UV curable paints, such as Hitachi Chemical Polymer Co., Ltd. (trade name “XY” series, etc.), Toho Kasei Kogyo Co., Ltd. (trade name “Hi-Rock” series, etc.), Three Bond Co., Ltd. ( Product names such as “Three Bond” series), Toa Gosei Chemical Industry Co., Ltd .; (Product name “Arontite” series, etc.), Cemedine Co., Ltd .; (Product name “Cemeloc Super” series, etc.) can be used. However, it is not limited to these.

  This type of pressure-sensitive adhesive may have insufficient adhesion when applied to a normal biaxially stretched polyester film. At that time, various primer treatments such as acrylic resin, polyester resin, urethane resin, etc. By providing such a laminated film, the adhesion between the polyester film and the pressure-sensitive adhesive layer can be improved.

  In the present invention, a hard coat layer can be formed on one side, and a primer layer for improving the adhesiveness with these pressure-sensitive adhesive layers can be formed on the opposite side. It goes without saying that when the coating solution containing the actinic radiation curable or thermosetting composition to be formed is applied, it may be applied to the back side of the coating solution at the same time, dried and optionally stretched.

  In addition, when the hard coat film of the present invention is used as an antireflection film for a plasma display or the like, it is preferably used by providing a high refractive index on the hard coat layer and further providing a low refractive index layer thereon. Can do.

  Although it does not specifically limit as a high refractive index layer, It is a thing with a refractive index of about 1.55-1.70, and it is preferable that a laminated thickness shall be 0.03-0.15 micrometer. Such a high refractive index layer can be obtained by finely dispersing metal compound particles in a binder component. The binder component is not particularly limited, and general-purpose resins such as polyester, acrylic, urethane, and epoxy can be used. The metal compound particle itself has a high refractive index, and specifically includes tin-containing antimony oxide particles, zinc-containing antimony oxide particles, tin-containing indium oxide particles, zinc oxide / aluminum oxide particles, antimony oxide particles, and oxidation. Although titanium particles, zirconium oxide particles, and the like can be used, compounds capable of adding an antistatic function are more preferable, and tin-containing indium oxide particles are particularly preferable. The metal compound particles having an average primary particle diameter (sphere equivalent diameter according to the BET method) of 0.5 μm or less, preferably 0.001 to 0.3 μm, are preferable in terms of maintaining transparency. Organic conductive materials such as polypyrrole, polyaniline, and polythiophene can be added to these metal compounds for the purpose of further improving the conductivity.

  The low refractive index layer preferably has a refractive index of about 1.30 to 1.40, and the lamination thickness is about 0.01 to 0.15 μm. As a material for forming the low refractive index layer, a known material can be applied, and a fluorine compound, a compound having a perfluoroalkyl group, and the like are preferable. It can also be achieved by filling hollow fine particles in the binder resin. Such hollow particles are disclosed, for example, in JP-A-2001-233611, J. Pat. AM. Chem. soc. 2003, 125, 316-317 and the like.

[Characteristic measurement method and effect evaluation method]
The characteristic measurement method and effect evaluation method in the present invention are as follows.

(1) Adhesion Peel test: Under normal conditions (23 ° C., relative humidity 65%), 100 crosscuts of 1 mm ² were put on the hard coat layer of the hard coat film, and cellophane tape (registered trademark) manufactured by Nichiban Co., Ltd. Is a test method in which the film is peeled in a 90-degree direction after being reciprocated three times with a load of 19.6 N using a rubber roller. Based on the number of remaining hard coat layers, evaluation is performed according to the following criteria.
○: After two peel tests, 80 or more hard coat layers remain Δ: After one peel test, 80 or more hard coat layers remain ×: One peel After the test, less than 80 hard coat layers remain.

(2) SW hardness The load on the surface of the hard coat layer was changed with steel wool # 0000 and rubbed 10 times (speed: 10 cm / s) under a constant load at each load, resulting in scratch resistance (not scratched). The maximum load was measured. 2 kg / cm ² was a practically acceptable level and was accepted.

(3) Long-term storage stability of the coating The coating 200CC is put in a 250 cc polyethylene jar and stored at 60 ° C. for 2 weeks. The storage stability is evaluated from the following criteria based on the change in viscosity before and after storage. Viscosity was measured using a B type viscometer (RB80 type viscometer: manufactured by Toki Sangyo Co., Ltd.).
○: η2 / η1 <1.2
×: η2 / η1> 1.2
η1: Viscosity of pre-storage coating at 25 ° C. (mPa · s)
η2: viscosity (mPa · s) of the coating after storage at 25 ° C.

(4) ΔSP (Difference in solubility parameter with substrate film)
ΔSP is calculated using Equations 1 and 2 according to the FEDOR method described in Reference 1, “Hideki Yamamoto, SP Value Basics / Applications and Calculation Methods, 2005, Information Organization, p. 66-67”. The values of Reference 1 are used for the cohesive energy and molar molecular volume.

Formula 1: <SP> = [(ΣEcoh / ΣV)] ^1/2
Formula 2: ΔSP = | <SP> s− <SP> h |
<SP>: Solubility parameter Ecoh: Cohesive energy of each substituent V: Mole molecular volume of each substituent ΔSP: Difference in solubility parameter with substrate film <SP> s: Solubility parameter of substrate film <SP> h: Solubility parameter of hard coat coating components.

(4) Haze It measured based on JISK-7105 using fully automatic direct reading haze computer HGM-2DP (made by Suga Test Instruments Co., Ltd.).

(5) Total light transmittance The total light transmittance of the hard coat film thickness direction was calculated | required using the fully automatic direct reading haze computer HGM-2DP (made by Suga Test Instruments Co., Ltd.), and it was set as the average value of 10-point measurement.

(6) Transmission b value Using a spectroscopic color difference meter SE-2000 type (manufactured by Nippon Denshoku Industries Co., Ltd.), the transmission b value was measured by the transmission method according to JIS-K-7105.

  Next, although this invention is demonstrated based on an Example, this invention is not necessarily limited to these.

Example 1
A polyethylene terephthalate (hereinafter referred to as PET, intrinsic viscosity 0.62 dl / g) chip containing 0.015% by weight of colloidal silica having an average particle size of 0.4 μm and 0.005% by weight of colloidal silica having an average particle size of 1.5 μm, After sufficiently drying in vacuum at 180 ° C for 3 hours, feeding to an extruder, melting at 285 ° C, extruding into a sheet from a T-shaped die, and a mirror cast drum having a surface temperature of 20 ° C using an electrostatic application casting method And then cooled and solidified to obtain an unstretched sheet. The unstretched sheet thus obtained was stretched 3.2 times in the longitudinal direction with a roll group heated to 85 ° C. to obtain a uniaxially stretched film. On one side of this uniaxially stretched film, a coating agent having a composition shown in Example 1 in Table 2 (mixture of dipentaerythritol hexaacrylate and dipentaerythritol pentaacrylate (KAYARAD-DPHA: manufactured by Nippon Kayaku Co., Ltd.)) 100 Parts by weight, 15 parts by weight of fully alkylated melamine (Cymel 350: manufactured by Nippon Cytec Industries, Ltd.), and 8 parts by weight of polyethylene glycol dimethacrylate (FA-220M: manufactured by Hitachi Chemical Co., Ltd.) to a thickness of 20 μm by a metabar system. While holding both ends of the film coated with the coating with clips, the film was guided to a preheating zone at 85 ° C., and subsequently stretched 3.3 times in the width direction in a heating zone at 100 ° C. Further, 5% continuously Heat treatment for 15 seconds in a heat treatment zone at 220 ° C. while performing a relaxation treatment in the width direction to cure the coating film and heat The hard coat film thus obtained was excellent in transparency with a total thickness of 125 μm and a hard coat layer thickness of 5 μm, as shown in Table 2, without using an adhesive layer. Nevertheless, the coating composition used in Example 1 had very good adhesiveness and excellent wear resistance (SW hardness), and the storage stability of the coating material used in Example 1 was very good. There was no increase.

(Examples 2 to 10)
A hard coat film was prepared in the same manner as in Example 1 except that the paint having the composition shown in Examples 2 to 10 in Table 2 was used instead of the hard coat paint used in Example 1. As shown in Table 2, the film was extremely excellent in adhesiveness and good in wear resistance (SW hardness) even though no adhesive layer was used. This is presumably because FA-220M, M-240, and M-245 have good permeability to the base film. Moreover, the long-term storage stability of the coating material used in each Example was very good, and almost no increase in viscosity was observed after storage at 60 ° C. for 2 weeks.

(Comparative Examples 1-8)
A hard coat film was prepared in the same manner as in Example 1 except that the hard coat paint used in Example 1 was changed to a paint having the composition shown in Comparative Examples 1 to 8 in Table 2.

  In Comparative Examples 1 to 3 using M-350, the viscosity of M-350 showed a slightly higher value of 60 mPa · s, which resulted in slightly inferior adhesion and insufficient wear resistance. In Comparative Examples 4 to 6 using M-408, the viscosity of M-408 showed a considerably high value of 500 mPa · s, and thus the adhesion was poor and the wear resistance was insufficient. In Comparative Examples 7 to 8 in which the content of the melamine-based crosslinking agent (Cymel 350) is 0 part by weight, the adhesion promoting effect of the melamine-based crosslinking agent cannot be obtained, or the adhesiveness is poor. Abrasion was also insufficient. Since the coating materials used in Comparative Examples 1 to 8 did not contain a catalyst, the long-term storage stability of the coating materials was extremely good.

(Comparative Example 9)
A hard coat film was prepared in the same manner as in Example 1 except that the hard coat paint used in Example 1 was changed to a paint having the composition shown in Comparative Example 9 in Table 2.

  At these levels, Catalyst 296-9 (manufactured by Nippon Cytec Industries Co., Ltd.), which is a curing catalyst for the melamine-based crosslinking agent, was added to the coating, resulting in extremely excellent adhesion and wear resistance. However, since the coating contains a catalyst, the long-term storage stability of the coating was extremely poor.

(Comparative Example 10)
A hard coat film was prepared in the same manner as in Example 1 except that the hard coat coating used in Example 1 was changed to a coating having the composition shown in Comparative Example 10 in Table 2.

  In Comparative Example 10, since the low-viscosity acrylate (M-240) in the coating composition was not added, adhesion and wear resistance were poor.

   The film of the present invention provides a hard coat film that is excellent in adhesion to the hard coat layer without substantially intervening the adhesive layer and also excellent in wear resistance, and is used for displays such as LCD and PDP. It can be used in various applications such as touch panels, window coverings, and nameplates.

Claims (7)

A hard coat film in which a hard coat layer is laminated on at least one surface of a base film, and the hard coat layer is formed of a curable composition containing the following three components.
(I) Multifunctional acrylate
(ii) Melamine crosslinking agent
(iii) having at least two ethylenically unsaturated double bonds in one molecule having a viscosity at 25 ° C. of 50 mPa · s or less and a difference in solubility parameter from the base film (ΔSP) of 3.0 or less Low viscosity acrylate. The hard coat film according to claim 1, comprising 8 to 50 parts by weight of a low-viscosity acrylate having two or more ethylenically unsaturated double bonds in one molecule with respect to 100 parts by weight of the polyfunctional acrylate. The hard coat film according to claim 1 or 2, wherein the low-viscosity acrylate having two or more ethylenically unsaturated double bonds in one molecule is polyethylene glycol diacrylate. The hard coat film according to any one of claims 1 to 3, wherein the polyfunctional acrylate is an acrylate having four or more ethylenically unsaturated double bonds in one molecule. The hard coat film according to claim 1, wherein no adhesive layer is interposed between the base film and the hard coat layer. The hard coat film according to claim 1, wherein the base film is a polyester film. The hard coat film according to claim 1, wherein the base film is a polyethylene terephthalate or polyethylene-2,6-naphthalate film.