Hard coat film and method for producing the same

Abstract

To provide a hard coat film which has few flaw defects and does not cause appearance defects due to tight winding or the like.SOLUTION: The hard coat film has a base material film, an easily adhesive layer, and a hard coat layer in this order, wherein the base material film contains 1 mass% or less of particles having an average particle diameter of 0.5 μm or more and 2 μm or less, the content of the surface active agent (C) is 0.01 to 0.3 parts by mass with respect to 100 parts by mass of the total solids content of the resins (A) and (B), and the easily adhesive layer contains particles having a mean particle size of 20nm or more and 200nm or less in an amount of 0.2 parts by mass or more and 20 parts by mass or less with respect to 100 parts by mass of the total solids content of the resins (A) and (B).SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an easily adhesive polyester film and a method for producing the same. More specifically, the present invention relates to an easily adhesive polyester film that has few scratches or defects that occur during the film production process, has few appearance defects caused by winding tightening or the like that occurs during storage of the product roll, and has excellent adhesion to oxidative polymerization inks, UV-curable inks, hard coating resins, etc., and to an efficient method for producing the same. [Background technology]

[0002] In recent years, there has been a remarkable trend toward smaller and lighter notebook computers, tablet devices, and mobile phones. Furthermore, not only notebook computers but also a wide variety of other products using color LCD displays, such as LCD televisions and portable communication devices (e.g., tablet devices), have been put to practical use, and the display resolution is becoming increasingly higher.

[0003] As the resolution increases, the area of ​​the black matrix region increases, which reduces the aperture ratio of the pixels, making it important to adjust the brightness of the backlight unit.

[0004] As a method for improving the optical efficiency of a backlight unit, a backlight has been proposed in which a lens sheet, such as a lens sheet with a large number of prism-row lens units formed on one side, or a lens sheet with a large number of lenticular-row lens units formed on the light exit surface side of the light guide of the backlight.

[0005] These lens sheets refract light emitted from the backlight toward the front of the display, improving front brightness. Lens sheets typically use transparent plastic resins (base films) such as polycarbonate resins, acrylic resins, and polyester resins for their excellent formability. Polyester resins are widely used due to their excellent transparency, dimensional stability, and chemical resistance. However, there is a trend toward stricter control of film defects as brightness is adjusted.

[0006] Biaxially oriented polyester film is generally made by melt-extruding polyester resin into a sheet, which is then passed through conveyor rolls and biaxially stretched in the film's winding direction (MD) and width direction (TD). Sequential biaxial stretching and simultaneous biaxial stretching are commonly used for stretching, with sequential biaxial stretching being the most widely used. Sequential biaxial stretching utilizes the speed difference between conveyor rolls to stretch the film in the MD, and then stretches it in the TD using tenter clips.

[0007] When a film passes through a transport roll during the film-forming process, foreign matter on the transport roll may cause minute scratches on the film. These foreign matter are mainly caused by oligomers generated during the film-forming process, and measures such as periodic cleaning of the rolls and the use of low-oligomer raw materials as described in Patent Document 1 have been proposed to obtain high-quality films.

[0008] Additionally, the addition of protrusions to the film surface has been studied as a way to reduce micro-scratches. The effectiveness against scratches generally corresponds to SRa (center surface average roughness), an index of surface roughness, and it is known that the higher the SRa, the greater the effectiveness against scratches. One method of adding protrusions to the film surface is to make the film a three-layer structure and add inert particles to the surface layer of the film. However, when inert particles are added to the film, the difference in refractive index between the inert particles and the resin increases the haze, which is an index of film transparency, and transparency is impaired.

[0009] To address these problems, Patent Documents 2 and 3 propose using inert particles with different particle sizes to achieve both transparency and scratch resistance. Patent Document 4 also proposes making the surface layer of the three-layer structure very thin, thereby reducing the number of particles that do not contribute to protrusions and improving transparency.

[0010] Reducing scratches and foreign particles that are optical defects has been used without any problems in the past, thanks to proposals such as those disclosed in Patent Document 1. However, with the dramatic progress being made in increasing the resolution of displays, it was thought that minute scratches and foreign particles that were not previously considered problematic would come to be recognized as optical defects.

[0011] In addition, improvements in productivity have dramatically increased line speeds in processing and film-forming processes, making it necessary to reduce optical defects even under high-speed processing conditions. Therefore, attempts have been made to reduce optical defects caused by micro-scratches by providing protrusions on the film surface, as described in Patent Documents 2 to 4. However, when porous microparticles with an average particle size of 1 μm or less are used as described in Patent Documents 2 and 3, the microparticles aggregate, preventing uniform dispersion in the resin. The aggregated particles cause fish-eye defects, making it impossible to suppress optical defects to a level that would solve the above-mentioned problems.

[0012] Furthermore, as described in Patent Document 4, if the resin layer is made too thin compared to the particles, high-speed processing during processing and film formation can cause particles to fall off, raising concerns that this could become a cause of new optical defects. It has been found that, as in Patent Document 5, a method in which amorphous aggregate silica with a particle size of 2 μm or more is added to the film in an amount of 0.030 mass% or less, and particles of about 0.5 μm are added to the adhesion layer, does not cause scratches on the film production line, but that minute misalignments occur in the film due to roll tightening caused by changes in the product roll over time, causing particles in the adhesion layer to fall off, resulting in appearance defects such as white unevenness.

[0013] As described above, it has been found that no method has yet been established for stably obtaining high-quality optical films with few optical defects that can meet the demands for higher definition and improved productivity. [Prior art documents] [Patent documents]

[0014] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-130984 [Patent Document 2] Japanese Patent Application Publication No. 10-46012 [Patent Document 3] Japanese Patent Application Publication No. 8-73623 [Patent Document 4] Japanese Patent Application Laid-Open No. 2003-231229 [Patent Document 5] Japanese Patent Application Laid-Open No. 2011-5648 Summary of the Invention [Problem to be solved by the invention]

[0015] In view of the above-mentioned problems of the prior art, the problem to be solved by the present invention is to provide an easily adhesive polyester film that has few scratches and defects and does not suffer from appearance defects due to winding tightening during storage of the product roll, and an efficient method for producing the same. [Means for solving the problem]

[0016] That is, the present invention comprises the following: 1. An easily adhesive polyester film using a polyester film as a base film and having an easily adhesive layer on at least one side of the base film, wherein the base film contains particles having an average particle size of 0.1 μm or more and 2 μm or less in an amount of 1 mass % or less relative to the mass of the base film, and the easily adhesive layer is formed by curing a composition containing a copolymer polyester resin (A), a urethane resin (B) having a blocked isocyanate group, and a silicone surfactant (C). 2. The highly adhesive polyester film according to item 1 above, wherein the highly adhesive layer contains particles having an average particle size of 20 nm or more and 200 nm or less. 3. An easily adhesive polyester film as described in the above item 1 or 2, wherein the solid mass ratio (A) / (B) of the copolymerized polyester resin (A) to the urethane resin (B) having a blocked isocyanate group in the composition constituting the easily adhesive layer is 28 / 72 to 72 / 28. 4. A method for producing an easy-adhesion polyester film according to any one of the above items 1 to 3, in which a composition containing at least a copolymer polyester resin (A), a urethane resin (B) having a blocked isocyanate group, and a silicone surfactant (C) is diluted with a solvent to produce a coating liquid, the solvent containing water and alcohol, the water / alcohol mass ratio being 100 / 0 to 85 / 15, the coating liquid being applied by gravure coating or bar coating to at least one side of an unstretched film or a uniaxially stretched film during the production process of the base film, and then the film is stretched in at least the uniaxial direction in which it has not been stretched, and heat-treated to provide an easy-adhesion layer. [Effects of the Invention]

[0017] According to the present invention, it is possible to provide an easily adhesive polyester film that has few scratches and defects and does not suffer from appearance defects caused by winding tightness during storage of the product roll, and an efficient method for producing the same. DETAILED DESCRIPTION OF THE INVENTION

[0018] (Base film) Examples of polyester resins that can be used to form the polyester film, which is the base film of the present invention, include polyethylene terephthalate, polybutylene terephthalate, polytrimethylene terephthalate, polyethylene-1,2-diphenoxyethane-4,4'-dicarboxylate, and polyethylene-2,6-naphthalate, as well as copolymer polyesters in which the polymer components of these resins are used as the main component and any other ester structural unit is copolymerized.

[0019] The substrate film preferably contains 1% by mass or less of particles having an average particle size of 0.1 μm or more and 2 μm or less, based on the mass of the substrate film. By containing 1% by mass or less of particles with such an average particle size, the occurrence of scratches and defects on the stretching and / or drying rolls in the film-forming process is suppressed, which is preferable. An average particle size of 2 μm or less and a content of 1% by mass or less are also preferable because they allow the haze to be adjusted low and improve transparency. The average particle size is preferably 1.5 μm or less, more preferably 1.0 μm or less. The particle content is further preferably 0.2% by mass or less, particularly preferably 0.1% by mass or less, and most preferably 0.05% by mass or less. The lower limit of the particle content is preferably 0.001% by mass or more, more preferably 0.005% by mass or more, but is not limited to this range. The type of particles contained in the substrate film is not particularly limited, but may include organic particles such as siloxane copolymerized acrylic resin, cross-linked polystyrene, polystyrene-divinylbenzene, polymethyl methacrylate, methyl methacrylate copolymer, cross-linked methyl methacrylate copolymer, polytetrafluoroethylene, polyvinylidene fluoride, polyacrylonitrile, benzoguanamine resin, silicone resin, and acrylic resin, as well as inorganic particles such as silica, alumina, titanium dioxide, zirconium oxide, kaolin, talc, graphite, calcium carbonate, feldspar, molybdenum disulfide, carbon black, and barium sulfate. Core-shell particles with a multilayer structure, each composed of an inner and outer layer of a material with different properties, may also be used. Silica particles are particularly preferred due to their various favorable properties as a lubricant.

[0020] The substrate film may be a uniaxially stretched film or a biaxially stretched film, but a biaxially stretched film is preferred in terms of mechanical properties, etc. The stretching method may be simultaneous biaxial stretching, but a manufacturing process for a sequentially biaxially stretched film is preferably used.

[0021] The highly adhesive polyester film of the present invention preferably has a haze of 2% or less. A haze of 2% or less is preferable because it provides good optical properties and appearance when used in optical fields or when printed. It is more preferably 1.5% or less, and even more preferably 1.0% or less. A lower haze is preferable, but a haze of 0.1% or more, or even 0.3% or more, is acceptable.

[0022] (Easy adhesion layer) In the present invention, an easy-adhesion layer containing a copolymer polyester resin (A), a urethane resin (B) having a blocked isocyanate group, and a silicone surfactant (C) is provided on at least one side of the base film in order to improve the adhesion of inks, hard coating materials, etc. In the present invention, the expression "the easy-adhesion layer is formed by curing a composition containing a copolymer polyester resin (A), a urethane resin (B) having a blocked isocyanate group, and a silicone surfactant (C)" is used, but the above expression is used because it is extremely difficult to accurately describe the composition of the easy-adhesion layer after curing.

[0023] The glycol component (diol component) used in the polymerization of the copolymer polyester resin (A) preferably has a branched structure, and examples of the branched glycol component include 2,2-dimethyl-1,3-propanediol, 2-methyl-2-ethyl-1,3-propanediol, 2-methyl-2-propyl-1,3-propanediol, 2-methyl-2-isopropyl-1,3-propanediol, and 2-methyl-2-butyl-1,3-propanediol. Examples of suitable glycol components include diol, 2-methyl-2-n-hexyl-1,3-propanediol, 2,2-diethyl-1,3-propanediol, 2-ethyl-2-n-butyl-1,3-propanediol, 2-ethyl-2-n-hexyl-1,3-propanediol, 2,2-di-n-butyl-1,3-propanediol, 2-n-butyl-2-propyl-1,3-propanediol, and 2,2-di-n-hexyl-1,3-propanediol. The branched glycol component is preferably contained in an amount of 10 mol% or more, more preferably 20 mol% or more, of the total glycol components (total diol components). Ethylene glycol is the most preferred glycol component other than the above compounds contained in the copolymer polyester resin (A). Small amounts of diethylene glycol, propylene glycol, butanediol, hexanediol, or 1,4-cyclohexanedimethanol may also be used.

[0024] The dicarboxylic acid components contained as constituents of the copolymer polyester resin (A) are most preferably terephthalic acid and isophthalic acid. Small amounts of other dicarboxylic acid components, such as adipic acid, sebacic acid, and azelaic acid, and aromatic dicarboxylic acids such as diphenyldicarboxylic acid and 2,6-naphthalenedicarboxylic acid, may also be added and copolymerized.

[0025] In addition to the above dicarboxylic acid components, in order to impart water dispersibility, it is preferable to mix terephthalic acid having a sulfonic acid group or isophthalic acid having a sulfonic acid group in an amount of 1 to 10 mol % based on the total dicarboxylic acid components. For example, 4-sulfoisophthalic acid, sulfoterephthalic acid, 5-sulfoisophthalic acid, 5-sodiumsulfoisophthalic acid, 4-sulfonaphthalene-2,7-dicarboxylic acid, and 5-(4-sulfophenoxy)isophthalic acid can be preferably used.

[0026] The urethane resin (B) containing a blocked isocyanate group is preferably a thermally reactive water-soluble urethane in which the terminal isocyanate group is blocked (hereinafter referred to as blocked) with a hydrophilic group.

[0027] Examples of blocking agents for the isocyanate group include bisulfites, sulfonic acid-containing phenols, alcohols, lactams, oximes, and active methylene compounds. The blocked isocyanate groups hydrophilize or water-soluble the urethane prepolymer. When thermal energy is applied to the urethane resin (B) containing the blocked isocyanate groups during the drying or heat-setting process in film production, the blocking agent is released from the isocyanate groups, and the urethane resin (B) immobilizes the mixed copolymer polyester resin (A) in the self-crosslinked network and also reacts with the terminal groups of the copolymer polyester resin (A). When the coating solution is prepared, the urethane resin (B) is hydrophilic and therefore has poor water resistance. However, after application, drying, and heat-setting to complete the thermal reaction, the hydrophilic groups of the urethane resin (B), i.e., the blocking agent, are released, resulting in a coating film with good water resistance.

[0028] An example of the urethane resin (B) containing a blocked isocyanate group described above is Elastron (registered trademark) manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.

[0029] When preparing a coating solution by mixing the copolymer polyester resin (A) and the urethane resin (B) having blocked isocyanate groups used in the present invention, the mass ratio of the copolymer polyester resin (A) to the urethane resin (B) having blocked isocyanate groups is preferably (A):(B)=28:72 to 72:28. This range is preferable because it allows for a good balance of good adhesion to ink, good adhesion to hard coat materials, haze, and the like.

[0030] In the present invention, a silicone surfactant (C) is contained in the composition for forming the adhesion layer. The content of the silicone surfactant (C) can be, for example, 0.01 to 0.3 parts by mass per 100 parts by mass of the total solids content of the copolymer polyester resin (A) and the resin (B) containing a blocked isocyanate group. The silicone composition is not particularly limited, but the type and amount can be appropriately selected within the scope of the present invention to achieve a smooth and highly transparent film surface. Silicone surfactants manufactured by Shin-Etsu Silicones, Dow Corning Toray, and Momentive are suitable. The use of a silicone surfactant improves particle dispersibility in the coating layer and suppresses particle aggregation. Low-molecular-weight surfactants have a high diffusion ability in response to changes in surface tension of hydrophobic particles and hydrophobic resins, which facilitates maintaining the coating thickness around the particles and contributes to the resistance of particles to shedding.

[0031] The silicone surfactant (C) is preferably a nonionic silicone surfactant that is not easily affected by pH changes, and in particular, a polyoxyalkylene-modified silicone can be used. Specifically, it is represented by the following average composition formula (I): R 1 xR 2 ySiO(4-xy) / 2 (I) [In the formula, R 1 is an unsubstituted or substituted monovalent hydrocarbon group having 1 to 10, preferably 1 to 8, carbon atoms and no aliphatic unsaturated bond; R 2 is the general formula -CfH2fO(CgH2gOh)R 3 (R 3is a hydrogen atom, a monovalent hydrocarbon group such as an unsubstituted or substituted alkyl group having 1 to 8 carbon atoms, particularly 1 to 4 carbon atoms, which does not have an aliphatic unsaturated group, or an acetyl group, f is an integer of 2 to 12, particularly 2 to 6, g is an integer of 2 to 4, and h is an integer of 1 to 200, preferably 1 to 100, more preferably 1 to 50. It is an organic group represented by.). x and y are each 0 ≦ x < 3.0, 0 < y < 3.0, and are positive numbers satisfying 0 < x + y ≦ 3.0. Preferably, x is 0.1 to 2, y is 0.2 to 2, and x + y is 0.3 to 3.〕 Furthermore, the polyoxyethylene content in the polyoxyalkylene-modified silicone is preferably 30 to 80% by mass.

[0032] Examples of the silicone surfactant (C) include, but are not limited to, those having the following structural formulas (1) to (3).

[0033]

Chemical formula

[0034]

Chemical formula

[0035]

Chemical formula

[0036] By including the copolyester resin (A), the urethane resin (B) having a blocked isocyanate group, and the silicone surfactant (C) in the composition in the above-described contents, a film without defect can be obtained.

[0037] In the present invention, by incorporating particles having an average particle diameter of 20 nm to 200 nm in the adhesive layer, it becomes easier to produce a film with fewer scratches and defects. The average particle diameter of the particles is preferably 30 nm to 150 nm, more preferably 40 nm to 100 nm. Although it depends on the thickness of the adhesive layer to be applied, using particles with an average particle diameter of three times or more the thickness of the adhesive layer is undesirable because there is a high risk that the particles will fall off from the adhesive layer due to circumferential stress when the roll product is tightened. The type of particles contained in the adhesive layer is not particularly limited, but may include organic particles such as siloxane copolymerized acrylic resin, cross-linked polystyrene, polystyrene-divinylbenzene, polymethyl methacrylate, methyl methacrylate copolymer, cross-linked methyl methacrylate copolymer, polytetrafluoroethylene, polyvinylidene fluoride, polyacrylonitrile, benzoguanamine resin, silicone resin, and acrylic resin, as well as inorganic particles such as silica, alumina, titanium dioxide, zirconium oxide, kaolin, talc, graphite, calcium carbonate, feldspar, molybdenum disulfide, carbon black, and barium sulfate. Core-shell particles with a multilayer structure, each composed of an inner and outer layer of a material with different properties, may also be used. Silica particles are particularly preferred due to their various desirable properties as a lubricant, and colloidal silica, which is a spherical particle, is most desirable from the standpoint of dispersibility.

[0038] The average particle size of the particles in the substrate film and the easy-adhesion layer in the present invention was measured by observing the particles on the cross section of the film with a scanning electron microscope, observing 30 particles, and taking the average value as the average particle size.

[0039] As long as the objectives of the present invention are met, the particle size of irregularly shaped particles can be calculated as the equivalent circle diameter, which is calculated by dividing the observed particle area by π, calculating the square root, and then multiplying the result by two.

[0040] The content of particles in the easy-adhesion layer is preferably 0.3 parts by mass or more relative to 100 parts by mass of the total solid content of the copolymer polyester resin (A) and the urethane resin (B) containing a blocked isocyanate group. It is more preferably 0.5 parts by mass or more, and even more preferably 1.0 parts by mass or more. An amount of 0.3 parts by mass or more is preferable because it improves slipperiness and makes it easier to suppress scratches and other defects. The content of particles in the easy-adhesion layer is preferably 18 parts by mass or less relative to 100 parts by mass of the total solid content of the copolymer polyester resin (A) and the urethane resin (B) containing a blocked isocyanate group. It is more preferably 15 parts by mass or less, and even more preferably 8 parts by mass or less. An amount of 18 parts by mass or less is preferable because it reduces haze and improves transparency.

[0041] The thickness of the easy-adhesion layer is, for example, 5 nm to 500 nm, preferably 10 nm to 300 nm, and more preferably 20 nm to 150 nm.

[0042] The method for laminating the easy-adhesion layer in the polyester-based laminate film of the present invention is not particularly limited, and may be either so-called in-line coating or so-called off-line coating, in which processing is performed on a polyester film after biaxial stretching. Furthermore, any known coating method may be used for application. Preferably, an in-line coating method is used, in which a coating solution prepared by diluting a composition containing the copolymerized polyester resin (A), a urethane resin (B) having a blocked isocyanate group, and a silicone surfactant (C) with a solvent is applied to an unstretched or uniaxially oriented film during the manufacturing process of the base polyester film by gravure coating or bar coating, followed by stretching the unstretched film in at least one direction and heat setting. The resulting easy-adhesion polyester film exhibits excellent adhesion to various inks, particularly UV-curable inks and oxidatively polymerized (or solvent-based) inks, making it suitable for secondary processing such as labels.

[0043] The solvent used in the coating solution can be water or a mixed solvent of water and alcohol. The mass ratio of water to alcohol, expressed as water / alcohol, is preferably selected from the range of 100 / 0 to 85 / 15. A mass ratio of alcohol of 15 parts by mass or less relative to the total mass of water and alcohol is preferred because it allows for easy production using a conventional biaxially stretched film-making device. A mass ratio of water / alcohol in the range of 98 / 2 to 90 / 10 is desirable because the surface tension of the coating solution can be controlled by adding alcohol, making it easy to adjust the appearance of the easy-adhesion layer.

[0044] In the present invention, the gravure coating method or bar coating method can be suitably used as described above, and a highly transparent, easily adhesive film with few scratches or defects can be produced using a conventional biaxially stretched film-making apparatus.

[0045] From the viewpoint of preventing scratches during film formation, it is desirable to minimize the number of rolls used from coating to winding up, and therefore it is desirable to carry out the drying process from the coating process without using rolls, and to carry out the processes from drying to heat setting in a single drying oven. [Example]

[0046] The present invention will be described below with reference to specific examples, but the present invention is not limited to these examples. First, the evaluation methods used in the present invention will be described.

[0047] (Evaluation method) (1) Evaluation of ink adhesion On the adhesive layer of the adhesive polyester film obtained in the examples and comparative examples described below, a 250-mesh screen print was performed on the adhesive layer for oxidative polymerization (or solvent) type inks, followed by air drying for one day. Alternatively, a 300-mesh screen print was performed on the adhesive layer for UV-curing type inks, followed by UV exposure of 500 mJ / cm2 using a UV exposure device to cure the UV ink. Next, a cross-cut surface with 100 2mm squares was made on each ink surface with a utility knife, and Nichiban Cellotape (registered trademark) (25 mm wide) was adhered to the surface without trapping air bubbles, and then rubbed over the surface to ensure sufficient adhesion. The front and rear ends of the ink surface where the Cellotape (registered trademark) was not adhered were pressed down by hand, and the Cellotape (registered trademark) was rapidly peeled upward (at a 90-degree angle). The ink surface after peeling was observed, and adhesion was determined by the ink residue rate.

[0048] <Ink brand used> 1) Oxidative polymerization (or solvent) type ink (A) Seiko Advance KK RAM Black (a) Toyo Ink KK SS-8 White for PVC 2) UV curing type (c) Ink: Toyo Ink KK FDSS Black (D) Seiko Advance KK UVA Black <Evaluation method> After peeling off the cross-cut surface, the ink remaining rate was evaluated according to the following four-level scale. ◎: 100% residual rate and no peeling at all ○: 90% or more, can be used without any problems in practice △: Same as above 80% and can be used depending on the conditions. ×: Less than 80% and not suitable for use

[0049] (2) Evaluation of adhesion of hard coat resin The hard coat coating solution A described below was applied to the adhesive layer of the adhesive polyester film using a wire bar so that the coating thickness after drying would be 2 μm, and then dried with hot air at a temperature of 80°C for 60 seconds at an output of 120 W / cm. 2The film was passed at a speed of 10 m / min from a position 20 cm away from a high-pressure mercury lamp to obtain a hard-coated film. The refractive index of the hard-coated layer was 1.48. The coating solution was prepared by mixing the following materials in the mass ratio shown below and dissolving them by stirring for 30 minutes or more. Next, undissolved matter was removed using a filter with a nominal filtration accuracy of 1 μm, to prepare hard coat coating solution A. (Coating Solution A) Methyl ethyl ketone 64.48% by mass Pentaerythritol triacrylate 11.45% by mass (Shin Nakamura Chemical, NK ester A-TMM-3LM-N, number of functional groups: 3) Tripropylene glycol diacrylate 5.73% by mass (Shinnakamura Chemical, NK Ester APG-200, 2 functional groups) Dimethylaminoethyl methacrylate 5.72% by mass (Kyoeisha Chemical, Light Ester DM, functional group 1) Silica fine particles 11.45% by mass (Nissan Chemical Industries, MEK-ST-L, solid content: 30% by mass, average particle size: 50 nm) Photopolymerization initiator 1.14% by mass (Irgacure 184 manufactured by Ciba Specialty Chemicals) Silicone surfactant 0.03% by mass (Toray Dow Corning, DC57) Specifically, 100 grid-shaped cuts were made on the surface of the obtained hard coat layer using a cutter guide with a gap of 2 mm, penetrating the hard coat layer and reaching the base film. Next, cellophane adhesive tape (Nichiban Co., Ltd., No. 405; 24 mm wide) was attached to the grid-shaped cut surface and rubbed with an eraser to ensure complete adhesion. Then, the cellophane adhesive tape was peeled vertically from the hard coat layer surface of the hard coat film for molding, and the number of grids peeled from the hard coat layer surface of the base film was counted visually, and the adhesion between the hard coat layer and the base film was calculated using the following formula. Note that partially peeled grids were also counted as peeled grids, and the grids were ranked in four stages according to the following criteria. Adhesion (%) = (1 - number of peeled squares / 100) x 100 ◎: 100% ○: 90% or more but less than 100% △: 80% or more but less than 90% ×: Less than 80%

[0050] (3) Haze of highly adhesive polyester film The haze of the highly adhesive polyester film was measured in accordance with JIS K 7136:2000 using a turbidity meter (NDH2000, manufactured by Nippon Denshoku Corporation).

[0051] (4) Evaluation of scratches and defects The film provided with the easy-adhesion layer was cut into an A4 size piece, and bromine light was applied to it, and scratches of 0.5 mm or more were counted. The evaluation was made as follows. ◎:0 pieces ○:1~5 pieces ×:6 or more

[0052] (5) Evaluation of white unevenness defects In order to reproduce the pressurized state of the core, the film with the easy-adhesion layer was cut into 10cm squares, and 10 sheets were placed in a set, sandwiched between 5mm thick SUS plates on the top and bottom, and pressed with a pressure press at 50kgf / cm. 2 After keeping the film for 24 hours, the appearance of the film was evaluated. The evaluation was as follows: ◎: No change from before treatment. ◯: Whitening (white unevenness) is observed in an area of ​​5% or less. △: Whitening (white unevenness) is observed in 10% or less of the area. ×: Whitening (white unevenness) is observed in more than 10% of the area.

[0053] Example 1 (1) Preparation of coating solution The coating solution used in the present invention was prepared according to the following method. 95 parts by weight of dimethyl terephthalate, 95 parts by weight of dimethyl isophthalate, 35 parts by weight of ethylene glycol, 145 parts by weight of neopentyl glycol, 0.1 parts by weight of zinc acetate, and 0.1 parts by weight of antimony trioxide were charged into a reaction vessel and subjected to a transesterification reaction at 180°C for 3 hours. Next, 6.0 parts by weight of 5-sodium sulfoisophthalic acid was added, and an esterification reaction was carried out at 240°C for 1 hour. After that, a polycondensation reaction was carried out at 250°C under reduced pressure (10 to 0.2 mmHg) for 2 hours to obtain a copolymerized polyester resin (A) with a number average molecular weight of 19,500 and a softening point of 60°C.

[0054] 64 parts by mass of the obtained copolymerized polyester resin, 144 parts by mass of butyl cellosolve, and 114 parts by mass of water were stirred for 6 hours or more while heating to obtain a uniform, pale white aqueous dispersion with a solids concentration of 30%.

[0055] The copolymerized polyester resin (A) obtained by the above treatment, 11.3 parts by weight of a self-crosslinking polyurethane resin containing blocked isocyanate groups (Dai-ichi Kogyo Seiyaku, Elastron® H-3DF) (B), a silicone surfactant (Dow Corning Toray, 67 Additive) (C1), and colloidal silica (Nissan Chemical Industries, Snowtex OL; average particle size 40 nm) (P1) were dispersed in a solvent at a solids ratio of (A) / (B) / (C1) / (P1) = 50 / 50 / 0.1 / 5 to form a coating solution (X) with a solids content of 7% by weight. The solvent was a 95 / 5 mixture of water and isopropyl alcohol.

[0056] (2) Manufacturing of laminated polyester film Particle-free polyethylene terephthalate resin pellets with an intrinsic viscosity of 0.62 dl / g were used as the raw polymer and dried under reduced pressure (133.3 Pa) for 6 hours at 135°C. Next, the polyethylene terephthalate resin was fed into extruder I, and resin pellets prepared by adding 0.10% silica particles with an average particle size of 1.5 μm to the same polyethylene terephthalate were fed into extruder II. The mixture was melt-extruded at 285°C to a thickness ratio of II / I / II = 5 / 90 / 5, and then rapidly cooled and solidified on a metal roll with a surface temperature of 25°C to obtain a cast film.

[0057] The obtained cast film was heated to 95°C using a group of heated rolls and an infrared heater, and then the coating solution X was applied to one side of a uniaxially oriented PET film traveling at a speed of 40 m / min using a gravure coater. The coating amount was 0.08 g / m2 in terms of final solid content. 2 The film was then stretched transversely at 120°C to 4 times its original size in a tenter, and subsequently heat-treated in the tenter at 220°C while relaxing by 3% in the transverse direction to obtain an adhesive polyester film with a total thickness of 50 μm. The thickness of the adhesive layer was 80 nm.

[0058] Examples 2 to 5 Highly adhesive polyester films were obtained in the same manner as in Example 1, except that the solid mass ratio of copolymerized polyester resin (A) / urethane resin (B) having blocked isocyanate groups was changed to 30 / 70, 70 / 30, 25 / 75, and 75 / 25 as shown in Table 1.

[0059] (Examples 6 to 8, Comparative Example 1) As shown in Table 1, the silicone surfactant (C1) in the coating liquid was changed to KF-6012 (C2) manufactured by Shin-Etsu Silicones, L-77 (C3) manufactured by Momentive, or 502 Additive (C4) manufactured by Toray Dow Corning, or no surfactant was used, and other easily adhesive polyester films were obtained in the same manner as in Example 1.

[0060] (Comparative Example 2, Example 9) As shown in Table 1, the silicone surfactant (C1) in the coating solution was changed to a fluorochemical surfactant F-470 (C5) manufactured by DIC and the amount added was adjusted, and the silicone surfactant (C1) was used in an amount five times greater than that of the coating solution. Except for this, highly adhesive polyester films were obtained in the same manner as in Example 1.

[0061] (Examples 10 and 11) Highly adhesive polyester films were obtained in the same manner as in Example 1, except that the colloidal silica (P1) in the coating solution was changed to Snowtex ZL (P2, average particle size 100 nm) manufactured by Nissan Chemical Industries, Ltd., or MP2040 (P3, average particle size 200 nm) manufactured by Nissan Chemical Industries, Ltd., and the content was adjusted as shown in Table 1. Both P2 and P3 are silica particles, just like P1.

[0062] (Examples 12 and 13) As shown in Table 1, the amount of colloidal silica (P1) in the coating solution was changed to 20 parts by mass or 0.2 parts by mass relative to the total solid mass of the copolymerized polyester (A) and the urethane resin (B) having a blocked isocyanate group, respectively. Each highly adhesive polyester film was obtained in the same manner as in Example 1.

[0063] (Examples 14 to 17, Comparative Example 3) Highly adhesive polyester films were obtained in the same manner as in Example 1, except that the average particle size and content of the polyethylene terephthalate used as the base film were changed as shown in Table 1.

[0064] (Examples 18 and 19, Comparative Example 4) As shown in Table 1, the base film consisted of a layer in which resin pellets containing 0.10% silica particles with an average particle size of 0.5 μm were added to polyethylene terephthalate and fed into extruder II, a layer in which resin pellets containing 0.02% silica particles with an average particle size of 0.8 μm were added to extruder II, and a layer in which only polyethylene terephthalate resin was fed into extruder I. An easily adhesive polyester film was obtained in the same manner as in Example 1, except that each of the films was changed to a single layer containing only the layer containing the adhesive.

[0065] The film preparation conditions and evaluation results for each example and comparative example are summarized in Tables 1 and 2 below.

[0066] [Table 1]

[0067] [Table 2] [Industrial Applicability]

[0068] According to the present invention, it is possible to provide an easily adhesive polyester film that has few scratches and defects and does not suffer from appearance defects caused by winding tightness during storage of the product roll, and an efficient method for producing the same.

Claims

1. A hard coat film having a base film, an easy-adhesion layer, and a hard coat layer in that order, wherein the base film is a polyester film. The aforementioned base film contains 1% by mass or less of particles with an average particle diameter of 0.5 μm or more and 2 μm or less, relative to the mass of the base film. The easy-adhesion layer is formed by curing a composition containing a copolymerized polyester resin (A), a urethane resin having a blocked isocyanate group (B), and a silicone-based surfactant (C). The aforementioned silicone-based surfactant (C) is a polyoxyalkylene-modified silicone. The content of the silicone-based surfactant (C) is 0.01 to 0.3 parts by mass with respect to 100 parts by mass of the total solid content of the copolymerized polyester resin (A) and the urethane resin (B) having a blocked isocyanate group. The aforementioned easy-adhesion layer contains particles with an average particle diameter of 20 nm or more and 150 nm or less. The content of the particles in the easy-adhesion layer is such that, with respect to 100 parts by mass of the total solid content of the copolymerized polyester resin (A) and the urethane resin (B) containing the blocked isocyanate group, the solid content is 0.3 parts by mass or more and 8 parts by mass or less. Hard coat film.

2. The hard coat film according to claim 1, wherein the composition forming the easy-adhesion layer comprises a silicone-based surfactant (C).

3. A method for producing a hard coat film according to claim 1, comprising: diluting a composition containing the copolymerized polyester resin (A), the urethane resin having a blocked isocyanate group (B), and the silicone-based surfactant (C) with a solvent to produce a coating solution, wherein the solvent comprises water and alcohol, and the water / alcohol mass ratio is from 100 / 0 to 85 / 15; applying the coating solution to at least one side of an unstretched film or a uniaxially stretched film during the manufacturing process of the base film by gravure coating or bar coating; stretching in at least one uniaxial direction that is not stretched; heat treatment; and providing an easily adhesive layer.