JP2006231845A - Hard coat film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hard coat film excellent both in smoothness and recoating workability. <P>SOLUTION: In the hard coat film a hard coat layer is laminated with smoothness index of ≥0.01 and ≤0.07 and surface energy of ≥40 mJ/m<SP>2</SP>and ≤50 mJ/m<SP>2</SP>on at least one face of a film base material. Concretely, the object is attained by adding a specified quantity of a low molecular weight acrylic polymer with weight-average molecular weight of ≥1,000 and ≤5,000 and viscosity of ≥100 mPa s/25°C and ≤3,000 mPa s/25°C. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention has a hard coat layer cured by heat or light on a transparent substrate film, has high surface hardness, excellent scratch resistance, and excellent leveling properties (smoothness) and recoatability (recoating properties). The present invention relates to a hard coat film. By providing the hard coat layer of the present invention on a transparent substrate, it is possible to obtain a hard coat film excellent in leveling property, recoat property and scratch resistance, and further the transparent substrate provided with the hard coat layer of the present invention is It is suitable for the surface of displays such as PDP, LCD, organic EL, electronic paper, and antireflection films and protective films such as touch panels.

  In recent years, substrate films, especially biaxially oriented polyester films, have excellent properties such as mechanical properties, dimensional stability, heat resistance, transparency, and electrical insulation properties, so magnetic recording materials, packaging materials, Applications in various fields such as insulating materials and optical display materials (for example, antireflection films and touch panel films) have been made.

  The base films as described above have come to be used as substitutes for glass products in terms of weight reduction, workability, etc., but since the surface of these base films is easily damaged, so far In general, a hard coat layer is provided or a film provided with a hard coat layer is used for the purpose of imparting scratch resistance. Also, conventional glass products are often used by attaching a plastic film to prevent scattering in the event of glass breakage, and a hard coat layer is generally widely formed on the surface. ing.

  However, since the conventional hard coat layer has been added with a leveling agent that remarkably lowers the surface tension such as silicone oil and fluorinated polyolefin (see Patent Document 1) in order to improve the smoothness of the cured coating film. The leveling property (smoothness) was sufficient, but the recoating property (re-coating property) was insufficient. That is, when a leveling agent that lowers the surface tension is included in the hard coat layer, the surface energy of the hard coat layer is reduced. When an antistatic layer, a high refractive index layer, a low refractive index layer or the like is applied, application defects such as application repelling, application unevenness, and application stripes often occur, and the recoating property is not fully satisfactory.

  Here, the leveling property means the property of smoothing the surface of the coating film in the coating film curing process. If the leveling property is good, the time until the coating film is smoothed in the coating film curing process can be shortened. . Leveling agent refers to a material that orients on the surface of the coating during the coating curing process, uniforms the surface tension of the coating, prevents dullness and repellency, and improves wetting on the coating. Specifically, the above-mentioned silicone oil, fluorinated polyolefin and the like can be mentioned.

In addition, in order to prevent the above-mentioned problems such as coating unevenness and enable recoating on the hard coat layer, the wettability of the surface by a method in which the leveling agent itself is not added or by physical treatment such as corona treatment or plasma treatment. There is a way to improve. However, in the method without adding a leveling agent, there is a problem that the smoothness of the cured coating film becomes insufficient, and when applied as an antireflection film for a display, the appearance defect such as distortion of the transmission image, When an antireflection film (AR film) is applied on the hard coat layer, problems such as a desired reduction in reflectance cannot be obtained. Further, in the method using corona treatment or plasma treatment, the coatability with the base film is improved and uniform coating is possible, but there is almost no effect in smoothing the surface of the cured coating film. As a method for imparting leveling properties and recoatability, a mechanical method using ultrasonic waves without adding a leveling agent, and applying a slight vibration to the coating film to reduce the surface waviness of the coating film (Patent Document 2) See). However, in this case, there is a problem that the kind and viscosity of the coating material to be used are limited, expensive equipment is required, and further, the processing speed is lowered, so that the production efficiency is lowered.
JP 2002-267804 A JP-A-5-154441

  As described above, in the prior art, in order to improve the smoothness of the coating film, the leveling agent is used by adding a leveling agent having a remarkably low surface tension such as silicone or fluorine to the coating liquid. When applying a coating that imparts functionality, such as an antistatic layer, a high refractive index layer, or a low refractive index layer, on the hard coat layer, application defects such as repellency, unevenness, and streaks are often caused. However, there is a problem that recoating becomes difficult. On the other hand, in order to improve the recoating property, leveling properties cannot be obtained unless a silicone-based or fluorine-based leveling agent is added, and the transmission image is distorted. There was a problem such as deterioration of property. The present invention aims to achieve both smoothness and recoatability of the hard coat layer.

  In order to achieve the present invention, the present inventors have focused on the following points and have solved the above problems.

That is, the present invention
On at least one surface of the film substrate, smoothness index is 0.01 or more and 0.07 or less, surface energy, 40 mJ / ^{m 2} or more, that the hard coat layer is laminated at 50 mJ / ^{m 2} or less Features hard coat film,
Consists of.

  In the present invention, addition of a low molecular weight acrylic polymer is preferred as an efficient method for reducing the surface viscosity of the hard coat layer coating liquid, and more specifically, a weight average molecular weight of 1,000 to 5,000 and an absolute viscosity of 100 mPa · It is preferable to use a low molecular weight acrylic polymer of s / 25 ° C. or higher and 3000 mPa · s / 25 ° C. or lower.

  The present invention improves the smoothness of the surface of the hard coat layer and improves the applicability of the functional material provided on the hard coat layer surface, so that it has excellent wear resistance, recoatability and visibility, and an antireflection film for display. And can be suitably used for applications in which multiple layers are laminated.

  Examples of the best embodiment of the present invention will be described below.

  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, polyphenylene sulfide, triacetate and polycarbonate. Of these, a film made of a thermoplastic resin, particularly a polyester, particularly excellent in transparency, mechanical strength, dimensional stability and the like is preferably used.

  Examples of the polyester film 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, these may be copolymerized with other dicarboxylic acid components or diol components. 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 crystallinity can be measured by a Raman spectrum analysis method.

  When the above-described film is used, its intrinsic viscosity (measured in 0-chlorophenol at 25 ° C. according to JIS K7367) is desirably 0.4 to 1.2 dl / g, more preferably 0.5 to 0.8 dl / g. If the intrinsic viscosity is less than 0.4 g / dl, the strength is insufficient, which is not preferable. Further, even if the intrinsic viscosity exceeds this preferred range, not only is the quality excessive, but also the operability during film production is deteriorated, which is economically undesirable.

  Moreover, as a base film used for this invention, the composite film of a laminated structure of two or more layers may be sufficient. 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 body portion contains fine bubbles. In addition, the composite film may be a chemically different polymer or an identical polymer in the inner layer portion and the surface layer portion.

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

The base film of the present invention may contain various additive resin compositions, cross-linking agents and the like within a range not impairing the effects of the present invention. For example, antioxidants, heat stabilizers, UV absorbers, organic and inorganic particles, pigments, dyes, antistatic agents, nucleating agents, acrylic resins, polyester resins, urethane resins, polyolefin resins, polycarbonate resins, alkyd resins, Epoxy resin, urea resin, phenol resin, silicone resin, rubber resin, wax composition, melamine crosslinking agent, acrylamide, polyamide, epoxy resin, isocyanate compound aziridine compound, various silane coupling agents, various titanate coupling agents, etc. Can be mentioned.

  Among these, slipperiness is achieved when inorganic particles such as silica, colloidal silica, alumina, alumina sol, kaolin, talc, mica, calcium carbonate, barium sulfate, carbon black, zeolite, titanium oxide, and metal fine powder are added. In addition, scratch resistance and the like can be improved. Average particle diameter of inorganic particles (the particle diameter referred to here is a value obtained using a laser diffraction particle size distribution measuring apparatus. The average particle diameter is a 50% distribution particle diameter. 50% distribution) The particle size refers to the particle size where the particle size distribution is 50%, and the average particle size refers to this particle size unless otherwise specified.) Is about 0.005 to 5 μm, preferably about 0.05 to 1 μm. Is preferred. The addition amount is 0.05 parts by weight, preferably 0.1 to 10 parts by weight.

  The hard coat film of the present invention is obtained by laminating a hard coat layer on at least one surface of a base film, and the hard coat layer needs to have a smoothness index of 0.01 or more and 0.07 or less. . Preferably it is 0.01 or more and 0.05 or less, More preferably, it is 0.01 or more and 0.04 or less. When the smoothness index is less than 0.01, the slipperiness is insufficient and the handling property is deteriorated. On the other hand, if it exceeds 0.07, the distortion of the image and the uniformity of the layer applied on the hard coat layer become insufficient. For example, when applied to an antireflection film, there is a problem that a sufficient antireflection effect cannot be obtained. appear.

  Here, in the present invention, the smoothness index represents the degree of smoothness of the coating film surface. When the smoothness index is large, the smoothness of the coating film surface is insufficient, so that the distortion of the image becomes significant. A problem occurs. In addition, problems such as insufficient uniformity of the layer applied thereon occur. On the other hand, when the smoothness index is small, since the smoothness of the coating film surface is very excellent, comfortable visibility can be obtained without causing image distortion. In the present invention, the smoothness index is 0.01 or more and 0.07 or less, preferably 0.01 or more and 0.05 or less, more preferably 0.01 or more and 0.04 or less. It has a hard coat function like an antireflection film for use, and can be suitably used for the purpose of laminating multiple layers.

The surface free energy of the hard coat layer of the present invention is 40 mJ / ^{m 2} or more, 50 mJ / ^{m 2} or less, preferably 40 mJ / ^{m 2} or more, is required to be 45 mJ / ^{m 2} or less.

If the surface free energy of the hard coat layer is lower than 40 mJ / m ^2, it is not preferable because the coating liquid repels when the functional coating liquid is applied. Further, the surface free energy (50 mJ / m ² or more) is not preferable because the leveling property becomes insufficient.

  Regarding the smoothness index and the surface energy value within the above ranges, the following points were noted and achieved. It is generally known that when a coating liquid is applied to a substrate, the coating film surface has unevenness (film thickness non-uniformity), and this coating film surface unevenness is represented by a sine wave as shown in FIG. And represented by the Orchard-Rhodes equation as follows.

t _1/2 = k · η · λ ⁴ / (γ · h ₀ ³ )
Here, k = 0.001337 (constant), η: coating liquid viscosity, γ: surface tension of coating liquid, λ: wavelength of waviness, h: average film thickness of coating film. Further, t _1/2 indicates the time (half life) until the amplitude of the initial swell is halved.

The present inventors paid attention to the fact that in the above formula, if the coating liquid viscosity is small, t _1/2 is also small. However, the addition of several tens of percent or more of a new component having a low viscosity in order to reduce the viscosity of the coating liquid itself will lose the original physical properties of the coating liquid. For this reason, the present inventors reduced only the viscosity of the outermost surface of the coating film by adding a new component having a low viscosity at a very small amount of several percent and positively depositing this component on the surface. As a result, a low molecular weight polymer having a surface tension and viscosity smaller than those of the hard coat layer forming coating was deposited on the surface. By reducing the surface viscosity of the coating film, the smoothness index and the surface energy can be set to the above values.

When a low molecular weight polymer having a lower surface tension and lower viscosity than a hard coat layer-forming coating material is selected and contained, the component with a low surface energy (leveling agent) is on the air side to stabilize thermodynamically. The leveling agent moves spontaneously to the interface. The smoothness index and surface energy of the present invention can be obtained by changing the absolute viscosity of the leveling agent.
From these viewpoints, in the present invention, a hard coat layer containing an acrylic polymer as a leveling agent having a weight average molecular weight of 1000 or more and 5000 or less and an absolute viscosity of 100 mPa · s / 25 ° C. or more and 3000 mPa · s / 25 ° C. or less is laminated. A configuration is preferred.

  If the weight average molecular weight of the acrylic polymer is less than 1000, it may be unfavorable because it volatilizes during the thermal curing of the hard coat layer. On the other hand, if the weight average molecular weight is greater than 5000, the hard coat layer may be inhibited from being cured, resulting in a decrease in wear resistance.

  In the present invention, the acrylic polymer preferably has an absolute viscosity of 100 to 3000 mPa · s / 25 ° C. At 100 mPa · s / 25 ° C. or lower, the viscosity of the coating surface layer becomes too low and the fluidity increases, and when hot air necessary for curing the hard coat layer is blown onto the coated surface, the coating surface is disturbed. Smoothness may be impaired. Moreover, when the absolute viscosity of the acrylic polymer is 3000 mPa · s / 25 ° C. or more, the fluidity of the coating liquid surface layer portion may be lowered, and the surface leveling property may be insufficient.

  Here, the absolute viscosity is a viscosity obtained by measuring the coating liquid with a B-type viscometer, and the absolute viscosity is calculated from a resistance torque applied to the rotor rotated in the coating liquid.

  As the acrylic polymer used in the present invention having the above characteristics, a long-chain alkyl acrylic polymer, a hydroxy acrylic polymer, a polyester acrylic polymer, a urethane acrylic polymer, an epoxy acrylic polymer, a polyether acrylic polymer, and the like are preferable. Are Toa Gosei Co., Ltd. (trade name “ARUFON” series, etc.), Enomoto Kasei Co., Ltd. (trade name “Dispalon L-1980” series, etc.), Kyoeisha Scientific Co., Ltd. (trade name “Polyflow” series, etc.) It is done.

  The amount of the acrylic polymer added is preferably 0.01 to 10 parts by weight, more preferably 0.05 to 5 parts by weight, particularly preferably 0.1 to 1 part by weight based on 100 parts by weight of the hard coat layer forming composition. Parts by weight. If the amount is less than 0.01 parts by weight, the leveling effect may not be exhibited. On the other hand, if it exceeds 10 parts by weight, the surface hardness may be insufficient.

  The hard coat layer of the present invention is formed on at least one of the base films, and this hard coat layer can be composed of an acrylic, urethane, organic silicate compound, silicone or the like. In particular, from the viewpoint of hardness and durability, and further from the viewpoint of curability and productivity, an acrylic, particularly active ray curable acrylic composition, or a thermosetting acrylic composition is preferred.

  The actinic ray curable acrylic composition and the thermosetting acrylic composition contain a polyfunctional acrylate, an acrylic oligomer or a reactive diluent, and, if necessary, a photoinitiator or a photosensitizer. An agent, a thermal polymerization initiator or a modifier may be added.

  When the typical thing of the acrylic composition which comprises a hard-coat layer is illustrated, the polyfunctional acrylate which has 3 (more preferably 4 or 5) or more (meth) acryloyloxy groups in 1 molecule, and its modified polymer, Specific examples include pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol tri (meth) acrylate, dipentaerythritol tetra (meth) acrylate, dipentaerythritol penta (meth) acrylate, Dipentaerythritol hexa (meth) acrylate, trimethylolpropane tri (meth) acrylate, pentaerythritol triacrylate hexanemethylene diisocyanate urethane polymer, and the like can be used. These monomers can be used alone or in combination of two or more. Commercially available polyfunctional acrylic compositions include Mitsubishi Rayon Co., Ltd. (trade name “Diabeam” series, etc.), Nagase Sangyo Co., Ltd. (trade name “Denacol” series, etc.), Shin-Nakamura Co., Ltd .; (Product name “NK Ester” series, etc.), Dainippon Ink and Chemicals Co., Ltd .; (Product name “UNIDIC”, etc.), Toa Gosei Chemical Industry Co., Ltd. (“Aronix” series, etc.), Nippon Oils and Fats Corporation; Such as “Blenmer” series), Nippon Kayaku Co., Ltd .; (trade name “KAYARAD” series, etc.), Kyoeisha Chemical Co., Ltd .; (trade name “light ester” series, etc.), etc. be able to.

  The use ratio of the monomer having three or more (meth) acryloyloxy groups in one molecule is preferably 20 to 90% by weight with respect to the total amount of the constituent components of the hard coat layer, more preferably 30 to 80% by weight, most desirably 30 to 70% by weight.

  When the proportion of the monomer used is less than 20% by weight, it may be insufficient in terms of obtaining a cured film having sufficient wear resistance, and when the amount exceeds 90% by weight. May cause inconveniences such as large shrinkage due to curing, distortion in the cured film, and curling to the cured film side.

  Here, acrylic oligomers include polyester acrylates, urethane acrylates, epoxy acrylates, polyether acrylates, and the like including those in which a reactive acrylic group is bonded to an acrylic resin skeleton, and also melamine and isocyanuric acid. A material obtained by bonding an acrylic group to a rigid skeleton such as can also be used.

  In addition, the reactive diluent serves as a solvent for the coating process as a coating medium, and has a group that itself reacts with a monofunctional or polyfunctional acrylic oligomer. It becomes a polymerization component.

Specific examples of these acrylic oligomers, reactive diluents, photopolymerization initiators, photosensitizers, thermal polymerization initiators, etc. are Shinzo Yamashita, Tosuke Kaneko, “Crosslinking Agent Handbook”, Taiseisha 1981, Reference can be made to the paragraphs 267 to 275 and 562 to 593, but the present invention is not limited to these.

  In the present invention, as a method for curing the above hard coat composition, for example, a method of irradiating ultraviolet rays as active rays or a high temperature heating method can be used, and when these methods are used, It is desirable to add a photopolymerization initiator or a thermal polymerization initiator to the composition.

  In the present invention, as a modifier for the hard coat layer, a coating property improver, an antifoaming agent, a thickener, an antistatic agent, inorganic particles, organic particles, an organic lubricant, an organic polymer compound, an ultraviolet ray, Absorbers, light stabilizers, dyes, pigments, stabilizers, and the like can be used. These are used as a composition for the coating layer constituting the hard coat layer within a range that does not impair the reaction due to actinic rays or heat. The properties of the coat layer can be improved.

  Specific examples of the photopolymerization initiator include acetophenone, 2,2-diethoxyacetophenone, p-dimethylacetophenone, p-dimethylacetophenone, p-dimethylaminopropionone, benzophenone, 2-chlorobenzophenone, 4,4′-dichlorobenzophenone, 4,4′-bisdiethylaminobenzophenone, Michler's ketone, benzyl, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, methyl benzoyl formate, p-isopropyl-α-hydroxyisobutylphenone, Carbonyl compounds such as 2,2-dimethoxy-2-phenylacetophenone and 1-hydroxycyclohexyl phenyl ketone, tetramethylthiuram monosulfide, tetramethylthiuramdi Rufido, thioxanthone, 2-chlorothioxanthone, and the like can be used sulfur compounds such as 2-methyl thioxanthone. These photopolymerization initiators may be used alone or in combination of two or more. Moreover, as a thermal polymerization initiator, a peroxide compound such as benzoyl peroxide or di-t-butyl peroxide can be used.

  The use amount of the photopolymerization initiator or thermal polymerization initiator is suitably 0.01 to 10 parts by weight with respect to 100 parts by weight of the hard coat layer formed product.

  In the hard coat layer forming composition used in the present invention, thermal polymerization such as hydroquinone, hydroquinone monomethyl ether or 2,5-t-butyl hydroquinone is used to prevent thermal polymerization during production and dark reaction during storage. It is desirable to add an inhibitor. The addition amount of the thermal polymerization inhibitor is preferably 0.005 to 0.05% by weight with respect to the total weight of the hard coat layer forming composition.

  In the present invention, the pencil hardness of the hard coat layer is preferably 2H or more. The pencil hardness represents the hardness of the coating film, and in the present invention, the pencil hardness of the hard coat layer is preferably 2H or more. This is because when the pencil hardness is 2H or more, sufficient hardness can be obtained and the application can be sufficiently applied in applications (touch panel, portable information terminal) applied as an antireflection film.

In the present invention, the steel wool hardness is preferably ² kg / cm ² or more. The steel wool hardness is a standard value for evaluating the scratch resistance of the coating film. In the present invention, the steel wool hardness of the hard coat layer is required to be ² kg / cm ² or more. It is because it can fully apply in the application (touch panel, portable information terminal) applied as an antireflection film etc. similarly to pencil hardness by being ² kg / cm <2> or more.

As a means for applying a coating containing a composition for forming a hard coat layer, various application methods such as a reverse coat method, a gravure coat method, a rod coat method, a bar coat method, a die coat method, a spray coat method, etc. Can be used.

  Examples of the actinic rays used in the present invention include electromagnetic waves that polymerize acrylic vinyl groups such as ultraviolet rays, electron beams, and radiation (such as α rays, β rays, and γ rays). It is preferable.

  Examples of the heat source necessary for thermosetting used in the production of the present invention include a steam heater, an electric heater, an infrared heater, a far infrared heater, and the like. Air heated to at least 140 ° C. or higher using these, inert Gas is blown against the substrate and the coating film using a slit nozzle. Among these, air and nitrogen heated to 200 ° C. or higher are preferable, and nitrogen heated to 200 ° C. or higher is more preferable because curing speed is high.

  Although what is necessary is just to determine the thickness of a hard-coat layer according to a use, 0.1 micrometers-30 micrometers are preferable normally, More preferably, they are 1 micrometer-15 micrometers. When the thickness of the hard coat layer is less than 0.1 μm, the surface hardness is not sufficient because it is too thin even if it is sufficiently cured, and the surface tends to be easily scratched. On the other hand, when the thickness exceeds 30 μm Tends to crack in the cured film due to stress such as bending.

  Moreover, the obtained hard coat film can be used by bonding with various functional films by various methods, and an adhesive layer can be laminated on the other surface, or a conductive layer can be provided.

  As a preferred method for obtaining the hard coat film of the present invention, a coating material containing a hard coat composition is applied to at least one surface of a thermoplastic film that is uniaxially stretched and crystal orientation is incomplete, and then, A production method is preferred in which the film is stretched in a direction perpendicular to the uniaxial stretching direction through a preheating step, heat fixed, and further subjected to active ray irradiation treatment as necessary.

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

  PET pellets (extreme viscosity 0.62 g / dl) containing 0.2% by weight of silica particles having an average particle diameter of 0.3 μm were 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. Then, the obtained unstretched sheet is stretched 2 to 5 times in the longitudinal direction with a roll group heated to 70 to 120 ° C. Next, a coating containing the composition for the hard coat layer containing the acrylic polymer of the present invention is applied to the surface of the film stretched uniaxially in this manner, and then both ends of the film are held with clips. , Lead to the tenter. In the tenter, the film is stretched about 2 to 5 times in the width direction after preheating. The laminated film stretched in the width direction is subjected to a heat treatment (resin glass transition temperature to melting point temperature, PET in the case of PET) while further performing a relaxation treatment of 3 to 10% while completing the crystal orientation of the base film and the coating film curing. Then, 200 to 245 ° C. is preferable).

  The hard coat film of the present invention thus obtained has good productivity because the hard coat layer can be provided at a stretch in the film forming process, has high coating surface hardness, and excellent recoatability. Since the coating film surface is excellent in smoothness and visibility, it can be used in a wide range of applications. In particular, it is suitable as an antireflection film substrate or a touch panel substrate on the surface of a display such as PDP, LCD, organic EL, and electronic paper.

[Method for measuring characteristics and method for evaluating effects]
The characteristic evaluation method and the effect evaluation method in the present invention are as follows.

(1) Abrasion resistance (steel wool hardness)
The load on the surface of the hard coat layer was changed with steel wool # 0000 and rubbed 10 times under a constant load at a load of 0.5, 1, ² , 3, 4 kg / cm ² (speed 10 cm / s), and scratch resistance. The maximum load with (not scratched) was measured. 2 kg / cm ² or more was an excellent level, and was regarded as acceptable.

(2) Surface free energy Four types of liquids whose surface free energy and its components (dispersion force, polar force, hydrogen bonding force) are known (in the present invention, the method by Panzer (Japan Adhesion Association Journal, Vol. 15, No. 3) , P96, using water, ethylene glycol, formamide, and methylene iodide), and a contact angle meter CA-D type (manufactured by Kyowa Interface Science Co., Ltd.) at 20 ° C. and 50% RH. The contact angle of each liquid with respect to the hard coat surface was measured at 1. Each component was calculated using the following formulas introduced from the expanded Fowks formula and the Young formula.
(Γ _s ^d · γ _L ^d ) ^1/2 + (γ _s ^p · γ _L ^p ) ^1/2 + (γ _s ^h · γ _L ^h ) ^1/2 = γ _L (1 + cos θ) / 2
Here, γ _L ^d , γ _L ^p , γ _L ^h , and γ _L are the components of the dispersion force, polar force, and hydrogen bonding force of the measurement liquid, and the total surface free energy of each component (the numbers are vol. .15, No. 3, the water according to p96, ethylene glycol, formamide, indicates a) using the value of methylene ^{_{iodide, γ s d, γ s p}} , γ s h in the dispersion force of the hard coat surface, polar Each component of force and hydrogen bond strength is shown. Further, θ represents the contact angle of the measurement liquid on the measurement surface. Five points were measured on one measurement surface, and the average value was defined as θ. The known values and θ measurement was substituted into the above equation, 3 components of the measurement surface by simultaneous equations ^{_{(γ s d, γ s p}} , γ s h) was determined. The calculation was performed using a “Find Minimum” command of “Mathematical” which is numerical calculation software.

(3) Leveling (smoothness index)
In order to eliminate the influence of back surface reflection, the transmittance at a wavelength of 550 nm with black magic ink is used for the measurement surface of the hard coat film (the opposite surface of the hard coat layer side, or one of the surfaces in the case of a double-sided hard coat layer). 1 cm or less, and a sample of 6 cm * 6 cm is pasted on smooth Pyrex (registered trademark) glass with cello tape (registered trademark) (manufactured by Nichiban Co., Ltd.), using a rubber roller. Reciprocate three times with a load of 500 g and fix by pressing.

This sample was placed 20 cm directly under a three-wavelength fluorescent lamp (National Parook (registered trademark) three-wavelength daylight white (F.L.15EX-N 15W)), and the surface of the sample was inclined at an angle of 45 degrees from the horizontal plane on which the sample was placed. A reflected image of the fluorescent lamp was taken with a camera.
The sample placed on the horizontal plane was rotated 45 degrees and photographed a total of four times.

  The photograph image is taken into a Microsoft computer software power point of a personal computer using a scanner, and the boundary line of the reflected image of the fluorescent light is drawn by adjusting the gray scale of the image control. The boundary line was read by Digital Curve Tracer (freeware) and graphed (FIG. 1).

  From this graph, the degree of distortion (deviation from the straight line portion) of the reflected image of the fluorescent lamp was defined as the degree of smoothness and defined as the smoothness index. The smaller the smoothness index, the smaller the distortion, and the smoother the surface.

  The smoothness index was calculated by extracting 100 points from the graph at regular intervals within the actual length of 4.5 cm and calculating the standard deviation. The standard deviation was obtained from the average value of four times of taking a total of four photographs.

  As the smoothness index, 0.07 or less is an excellent level, which is regarded as acceptable.

(4) Visibility In order to eliminate the influence of back surface reflection, the measurement surface of the hard coat film (on the opposite side of the hard coat layer side, or one side in the case of a double-sided hard coat layer) is black with black magic ink. After coloring the transmittance at 550 nm to be 1% or less, a sample of 6 cm * 6 cm was pasted on smooth Pyrex (registered trademark) glass with cello tape (registered trademark) (manufactured by Nichiban Co., Ltd.), Using a rubber roller, reciprocate three times at a load of 500 g and fix by pressing.

This sample is placed 20 cm directly under a three-wavelength fluorescent lamp (National Parook (registered trademark) three-wavelength daylight white (F.L.15EX-N 15W)), and the fluorescence of the sample surface is measured at an angle of 45 degrees from the horizontal plane on which the sample is placed. The degree of distortion of the reflected image of the lamp was visually evaluated.
Visibility is a level where ◎ and ○ are excellent, and it was accepted.

The reflected image looks clear. : ◎
The reflected image is slightly distorted. : ○
Reflected image is distorted and difficult to see. : △
I can't see the reflection image. : ×.
(5) Recoating property A line of ² cm width and 5 cm length (area 10 cm ² ) is drawn on the hard coat surface of the hard coat film with black magic (magic ink manufactured by Teranishi Chemical Industry Co., Ltd.) at 25 ° C. and 65% RH. The degree of magic ink repellency after standing for 10 minutes was evaluated by the area where the magic ink remained.
The recoating property was an acceptable level because ◎ and ○ were excellent.

Area ^{9cm 2 ~10cm} 2: ◎
Area 8 cm ² or more and less than 9 cm ² : ○
Area 7 cm ² or more and less than 8 cm ² : Δ
Area less than 7 cm ² : ×

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

<Coating agent A>
60 parts by weight of dipentaerythritol hexaacrylate (DPHA; manufactured by Nippon Kayaku Co., Ltd.), 20 parts by weight of trifunctional trimethylolpropane EO-modified triacrylate (M-350: manufactured by Toagosei Co., Ltd.), polyisocyanate (N3300: Sumika) A mixed coating composition of 20 parts by weight of Bayer Urethane Co., Ltd. and 1 part by weight of a zirconium complex catalyst (XC4205: Enomoto Kasei Co., Ltd.) was prepared.

<Coating agent B>
A mixed coating composition was prepared by adding 0.2 parts by weight of acrylic polymer (UP-1000: manufactured by Toa Gosei Co., Ltd.) having a weight average molecular weight of 3000 and a viscosity of 1000 mPa · s / 25 ° C. to coating agent A.

<Coating C>
A mixed coating composition was prepared by adding 2 parts by weight of acrylic polymer (UP-1000: manufactured by Toa Gosei Co., Ltd.) having a weight average molecular weight of 3000 and a viscosity of 1000 mPa · s / 25 ° C. to coating agent A.

<Coating agent D>
A mixed coating composition was prepared by adding 4 parts by weight of acrylic polymer (UP-1000: manufactured by Toa Gosei Co., Ltd.) having a weight average molecular weight of 3000 and a viscosity of 1000 mPa · s / 25 ° C. to coating agent A.

<Coating E>
A mixed coating composition was prepared by adding 8 parts by weight of acrylic polymer (UP-1000: manufactured by Toa Gosei Co., Ltd.) having a weight average molecular weight of 3000 and a viscosity of 1000 mPa · s / 25 ° C. to coating agent A.

<Coating agent F>
A mixed coating composition was prepared by adding 12 parts by weight of an acrylic polymer (UP-1000: manufactured by Toa Gosei Co., Ltd.) having a weight average molecular weight of 3000 and a viscosity of 1000 mPa · s / 25 ° C. to coating agent A.

<Coating G>
A mixed coating composition was prepared by adding 0.2 part by weight of acrylic polymer (UP-1021: manufactured by Toa Gosei Co., Ltd.) having a weight average molecular weight of 1600 and a viscosity of 400 mPa · s / 25 ° C. to coating agent A.

<Coating agent H>
A mixed coating composition was prepared by adding 0.2 parts by weight of acrylic polymer (UP-1110: manufactured by Toagosei Co., Ltd.) having a weight average molecular weight of 2500 and a viscosity of 3500 mPa · s / 25 ° C. to coating agent A.

<Coating I>
A mixed coating composition was prepared by adding 0.2 parts by weight of acrylic polymer (UP-1080: manufactured by Toagosei Co., Ltd.) having a weight average molecular weight of 6000 and a viscosity of 5000 mPa · s / 25 ° C. to coating agent A.

<Coating agent J>
A mixed coating composition was prepared by adding 0.2 part by weight of a silicone copolymer (SH-190: Toray Dow Corning Silicone) to Coating A.

Example 1
A polyethylene terephthalate (hereinafter referred to as PET) (extreme 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 at 180 ° C. under vacuum, it is supplied to an extruder, melted at 285 ° C., extruded from a T-shaped die into a sheet shape, and applied to a mirror cast drum having a surface temperature of 20 ° C. using an electrostatic application casting method. It was wound and solidified by cooling to obtain an unstretched sheet. The unstretched sheet thus obtained was stretched 3.5 times in the longitudinal direction with a roll group heated to 95 ° C. to obtain a uniaxially stretched film. The above-mentioned coating agent B was apply | coated to the single side | surface of this uniaxially stretched film by the metabar system. While holding both ends of the film coated with coating agent B with clips, the film was guided to a preheating zone at 90 ° C., and subsequently stretched 3.3 times in the width direction in a heating zone at 100 ° C. Furthermore, heat treatment for 17 seconds was performed in a heat treatment zone at 230 ° C. while continuously performing a relaxation treatment in the width direction of 3%, and the coating film was cured and heat-set. The hard coat film thus obtained had excellent transparency with a total thickness of 107 μm and a hard coat layer thickness of 7 μm. The results are shown in Table 1. It exhibited excellent properties such as abrasion resistance of 3 kg / cm ² , good recoatability (（), leveling properties (smoothness index: 0.041), and good visibility (◎).

(Example 2)
In Example 1, a hard coat film was produced in the same manner as in Example 1 except that instead of the coating material B, a coating material G containing acrylic polymers having different molecular weights and viscosities was used. The results are shown in Table 1. As shown in Table 1, abrasion resistance is 3 kg / cm ² , recoatability is good (◎), leveling property is good (smoothness index: 0.046), and visibility is good (◎). showed that.

(Comparative Example 1)
In Example 1, a hard coat film was produced in the same manner as in Example 1 except that the coating material H was used instead of the coating material B. The results are shown in Table 1. As shown in Table 1, although the wear resistance was 3 kg / cm ² and the recoatability was good (（), the leveling property was poor (smoothness index: 0.124) and the visibility was poor (Δ). there were.

(Comparative Example 2)
In Example 1, a hard coat film was produced in the same manner as in Example 1 except that the coating material I was used instead of the coating material B. The results are shown in Table 1. As shown in Table 1, the wear resistance was 3 kg / cm ² and the recoatability was good (良好), but the leveling property was poor (smoothness index: 0.138) and the visibility was poor (x). there were
(Example 3)
In Example 1, a hard coat film was produced in the same manner as in Example 1 except that the coating agent C was used instead of the coating agent B. The results are shown in Table 1. As shown in Table 1, the wear resistance is 3 kg / cm ² , the recoatability is good (◎), the leveling property is good (smoothness index: 0.041), and the visibility is good (◎). Indicated.

Example 4
In Example 1, a hard coat film was produced in the same manner as in Example 1 except that the coating material D was used instead of the coating material B. The results are shown in Table 1. As shown in Table 1, the wear resistance is 2 kg / cm ² , the recoatability is good (◎), the leveling property is good (smoothness index: 0.042), and the visibility is good (◎). Indicated.

(Example 5)
In Example 1, a hard coat film was produced in the same manner as in Example 1 except that the coating E was used instead of the coating B. The results are shown in Table 1. As shown in Table 1, the wear resistance is 2 kg / cm ² , the recoatability is good (◎), the leveling property is good (smoothness index: 0.058), and the visibility is good (◎). Indicated.

(Example 6)
In Example 1, a hard coat film was produced in the same manner as in Example 1 except that the coating agent F was used instead of the coating agent B. The results are shown in Table 1. As shown in Table 1, the recoatability was good (）), the leveling property was good (smoothness index: 0.041), and the visibility was good (◎), but the wear resistance was 1 kg / cm ² or less. The hard coat property was inferior.

(Comparative Example 3)
In Example 1, a hard coat film was produced in the same manner as in Example 1 except that, instead of the coating material B, the coating material J containing no acrylic polymer was used. The results are shown in Table 1. As shown in Table 1, the wear resistance was 3 kg / cm ² , the leveling property was good (smoothness index: 0.065), and the visibility was good (◯), but the recoatability was poor (x). there were.

(Comparative Example 4)
A product made from UV curable organic / inorganic hybrid hard coat agent (JSR Co., Ltd.) on one side of a polyethylene terephthalate film (trade name Lumirror U42, manufactured by Toray Industries, Inc.) that has been treated with easy adhesion of aliphatic polyester resin on both sides of 188 μm. No. Desolite KZ7224) (Coating agent J) was coated with a die coater, dried, and then irradiated with UV light at an integrated light quantity of about 700 mJ / cm ² using a high-pressure mercury lamp, and cured to prepare a hard coat film having a film thickness of 8 μm. The results are shown in Table 1. As shown in Table 1, the wear resistance was 3 kg / cm ² and the recoatability was good (◎), but the leveling property was poor (smoothness index: 0.120) and the visibility was poor (Δ). It was.

  Since the hard coat film of the present invention is excellent in smoothness and has a surface free energy in a specific range, it is used for optical use, particularly for antireflection film base materials for flat-screen televisions such as CSR, liquid crystal, plasma, rear production, SED, etc. It can be suitably used for materials and the like.

It is the schematic showing the outline of the measuring method of a smoothness index.

Claims (4)

On at least one side of the base film,
The smoothness index is 0.01 or more and 0.07 or less,
Surface energy, 40 mJ / ^{m 2} or more, a hard coat film The hard coat layer is 50 mJ / ^{m 2} or less and wherein the stacked. 2. The hard coat film according to claim 1, wherein the hard coat layer contains an acrylic polymer having a weight average molecular weight of 1000 or more and 5000 or less and an absolute viscosity of 100 mPa · s / 25 ° C. or more and 3000 mPa · s / 25 ° C. or less. . The hard coat film according to claim 1 or 2, wherein the hard coat layer has a pencil hardness of 2H or more and a steel wool hardness of 2 kg / cm ² or more. The hard coat film according to claim 1, wherein the hard coat layer contains an actinic ray curable or thermosetting acrylate cured product.

Images