Hard coat film

Abstract

To provide a hard coat film which is suitably usable for a cast film production step, and has a curable resin layer having extremely good surface smoothness.SOLUTION: A hard coat film for a cast film production step has a base material film, a curable resin layer (A) and a hard coat layer (B), wherein the base material film is a polyester film, the base material film and the hard coat layer (B) are stacked through the curable resin layer (A), the curable resin layer (A) contains a cured product of a resin composition containing one or more resin components selected from the group consisting of polyurethane, an acrylic resin and polyester, and a curable component, and the number of defects with a maximum diameter of 0.5 μm or more is 2 pieces / m2 or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] This invention relates to a hard coat film having a hard coat layer on a polyester film. [Background technology]

[0002] Polyester films are used in a wide range of fields due to their excellent transparency, optical properties, dimensional stability, mechanical strength, heat resistance, chemical resistance, and electrical properties. Specifically, they are used as magnetic recording materials, packaging materials, solar cells, separators for liquid crystal polarizers, substrates for dry film resists, release films for forming green sheets for multilayer ceramic capacitors, as well as optical films such as anti-reflective films, diffusion sheets, and prism sheets, and films for label printing. Furthermore, optical films and the like may have a hard coat layer on their surface to prevent scratches and improve the mechanical strength of the surface.

[0003] Incidentally, plastic films are susceptible to various foreign substances during the process of forming them from raw materials. For example, foreign substances may be introduced during the manufacturing or transportation of the raw materials, and if these foreign substances cannot be removed before the film is formed, they may remain inside the film. Furthermore, during the stretching and heat treatment of the film, dust is generated from inorganic substances resulting from the deterioration or damage of the molding machine, film fragments, organic compounds from thermal decomposition during film molding, and proteins from human work. These become airborne, settle on the film surface, and adhere to it, resulting in foreign matter on the film surface. As a method for removing this foreign matter adhering to the film surface, for example, Patent Document 1 discloses a web dust removal method that precisely removes foreign matter, dirt, dust, etc., particularly from the film surface. This method is characterized by continuously rubbing the moving web with an elastic body moistened with liquid, and then spraying the liquid onto the surface rubbed by the elastic body.

[0004] Furthermore, Patent Document 2 describes a cleaning method for removing foreign matter adhering to the surface of a polyester film, which exhibits a high foreign matter removal effect while suppressing film damage caused by cleaning, with a solubility parameter of 16-30 MPa. 1 / 2 A method for cleaning a polyester film is disclosed, characterized by vibrating an organic solvent, which has a boiling point in the range of 55 to 160°C, with ultrasound and bringing it into contact with the surface of a polyester film stretched in at least one direction. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2001-038306 [Patent Document 2] Japanese Patent Publication No. 2007-039494 [Overview of the project] [Problems that the invention aims to solve]

[0006] In recent years, in order to ensure high visibility and improve quality, there has been a demand for highly smooth films in components of various image display devices and in green sheets used when manufacturing multilayer ceramic capacitors. Therefore, it is considered necessary to remove foreign matter during film formation. However, it has become clear that the method described in Patent Document 1 does not have sufficient foreign matter removal capabilities and there is room for improvement, and that the method described in Patent Document 2 may cause the cured resin layer to dissolve when applied to a polyester film having a cured resin layer, depending on the type of cleaning agent.

[0007] Incidentally, polyimide films used as components of flexible displays require extremely high surface smoothness, and since these polyimide films are manufactured by the casting method, the transport films used during this manufacturing process also require extremely high surface smoothness.

[0008] Therefore, the object of the present invention is to provide a hard coat film having a cured resin layer that has extremely excellent surface smoothness, and in particular a hard coat film having a cured resin layer that can be suitably used for the casting process and has extremely excellent surface smoothness. [Means for solving the problem]

[0009] To solve the above problems, the present invention has the following configuration.

[0010] [1] The system comprises a base film, a cured resin layer (A), and a hard coat layer (B), wherein the base film is a polyester film, the base film and the hard coat layer (B) are laminated via the cured resin layer (A), and the cured resin layer (A) contains a cured product of a resin composition comprising one or more resin components selected from the group consisting of polyurethane, acrylic resin, and polyester, and a curing component, and the number of defects with a maximum diameter of 0.5 μm or more is 2 per square meter. 2 The following is a hard coat film for the casting process.

[0011] [2] The hard coat film for the casting process according to [1], wherein the water contact angle of the hard coat layer is less than 85°.

[0012] [3] The hard coat film for the casting process according to [1] or [2] above, wherein the hard coat layer (B) includes a cured product of urethane (meth)acrylate.

[0013] [4] A method for manufacturing a polyester film with a hard coat layer, comprising the following steps (1) to (4) in this order. (1) A process of forming a cured resin layer on at least one surface of a polyester film. (2) Step of applying an organic solvent to the cured resin layer. (3) A step of drying off the applied organic solvent. (4) A step of forming a hard coat layer on the hardened resin layer of the polyester film having the hardened resin layer after drying and removal.

[0014] [5] The solubility parameter (SP value) of the organic solvent is 16 to 30 MPa 1 / 2 and the boiling point thereof is within the range of 55 to 160°C, the method for producing a polyester film with a hard coat layer according to [4] above.

[0015] [6] The organic solvent contains methyl ethyl ketone, and the content of the methyl ethyl ketone is 50% by mass or less, the method for producing a polyester film with a hard coat layer according to [4] or [5] above.

[0016] [7] The organic solvent is a mixed solvent further containing toluene, the method for producing a polyester film with a hard coat layer according to [6] above.

[0017] [8] The formation of the hard coat layer is carried out by applying a hard coat agent, and the steps of drying and removing the organic solvent and applying the hard coat agent are continuously carried out, the method for producing a polyester film with a hard coat layer according to any one of [4] to [7] above.

[0018] [9] The cured resin layer obtained in the step (1) includes a cured product of a resin composition containing any one or more resin components selected from the group consisting of polyurethane, acrylic resin, and polyester and a curing component, the method for producing a polyester film with a hard coat layer according to any one of [4] to [8] above.

[0019]

[10] The hard coat layer obtained in the step (4) includes a cured product of urethane (meth) acrylate, the method for producing a polyester film with a hard coat layer according to any one of [4] to [9] above.

Advantages of the Invention

[0020] The hard coat film of the present invention can have extremely excellent surface smoothness by controlling the number of defects having a maximum diameter of 0.5 μm or more to 2 pieces / m 2 or less.

[0021] Furthermore, the hard coat film of the present invention can be cast while maintaining appropriate adhesion, and the number of defects with a maximum diameter of 0.5 μm or more is 2 per square meter. 2 The following control mechanisms allow for a high level of suppression of minute foreign matter and scratches transferred during casting, resulting in the advantage of producing highly smooth resin sheets. [Modes for carrying out the invention]

[0022] <Hard coat film for casting processes> The hard coat film for the casting process of the present invention comprises a base film, a cured resin layer (A), and a hard coat layer (B), wherein the base film is a polyester film. Furthermore, the base film and the hard coat layer are laminated together via the cured resin layer. Furthermore, the hard coat film for the casting process of the present invention has a defect count of 2 defects / m² with a maximum diameter of 0.5 μm or more. 2 The following applies:

[0023] The term "maximum diameter" refers to the maximum width of the defect size. If the defect is spherical, it is the diameter; if it is elliptical, it is the major axis; if it is plate-shaped, it is the diagonal length; and if it is polygonal, it is the longest line segment that passes through the center of the polygon and connects two points on the outer perimeter of the polygon. Furthermore, the maximum diameter of the defect can be measured by the method described in the examples.

[0024] The number of defects in the hard coat film of the present invention is 1.5 defects / m². 2 Preferably, the following is true: 0.8 pieces / m 2 The following is particularly preferable: The inventors of the present invention surmise that the formation of the hard coat layer causes defects to occur, with fine foreign matter adhering to the base film or foreign matter mixed in during the formation of the cured resin layer acting as nuclei. They believe that the hard coat film of the present invention has extremely excellent surface smoothness because the number of defects caused by such foreign matter is controlled.

[0025] <Base film> The polyester film used as the base film is not particularly limited as long as it is a film mainly composed of polyester, and the polyester may be homopolyester or copolymer polyester, or it may be a polymer blend mainly containing these polyesters. Furthermore, the term "primarily polyester" means that the component with the largest mass percentage among the components constituting the film is polyester, preferably with polyester accounting for 50% by mass or more, and more preferably with polyester accounting for 70% by mass or more.

[0026] (Polyester raw material) The homopolyester is preferably a polycondensation polymer of an aromatic dicarboxylic acid and an aliphatic glycol. Examples of aromatic dicarboxylic acids include terephthalic acid and 2,6-naphthalenedicarboxylic acid. Examples of aliphatic glycols include ethylene glycol, diethylene glycol, and 1,4-cyclohexanedimethanol. Typical polyesters include polyethylene terephthalate, polybutylene terephthalate, polyethylene-2,6-naphthalate, and polymethylene terephthalate.

[0027] The copolymerized polyester is preferably a polycondensation polymer of a dicarboxylic acid component and a glycol component. Examples of dicarboxylic acid components used in the copolymerized polyester include isophthalic acid, phthalic acid, terephthalic acid, 2,6-naphthalenedicarboxylic acid, adipic acid, sebacic acid, and oxycarboxylic acids (e.g., p-oxybenzoic acid). One or more of these can be used. Examples of glycol components include ethylene glycol, diethylene glycol, propylene glycol, butanediol, 4-cyclohexanedimethanol, and neopentyl glycol, and one or more of these can be used. The copolymerized polyester preferably contains terephthalic acid as the dicarboxylic acid component and ethylene glycol as the glycol component, with the terephthalic acid content being, for example, 50 mol% or more, preferably 70 mol% or more, and more preferably 90 mol% or more of the dicarboxylic acid component. Furthermore, the ethylene glycol content is 50 mol% or more, preferably 70 mol% or more, and more preferably 90 mol% or more, of the glycol component. Furthermore, the copolymer polyester may also contain structural units derived from difunctional compounds other than the dicarboxylic acid component and the glycol component. The amount of structural units derived from difunctional compounds other than the dicarboxylic acid component and the glycol component is preferably 20 mol% or less, and more preferably 10 mol% or less, relative to the total number of moles of all structural units constituting the polyester. Examples of difunctional compounds include various hydroxycarboxylic acids and aromatic diols.

[0028] (intrinsic viscosity) The intrinsic viscosity of the polyester is not particularly limited, but from the viewpoint of film-forming properties and productivity, it is preferably 0.45 to 1.0 dl / g, and more preferably 0.5 to 0.9 dl / g.

[0029] (Layer composition) The polyester film may have a single-layer structure or a multi-layer structure. In the case of a multi-layer structure, it may have two layers, three layers, four layers or more, and the number of layers is not particularly limited. Furthermore, the polyester film is preferably a uniaxially or biaxially oriented polyester film, and in particular, a biaxially oriented polyester film is preferred.

[0030] (Polymerization catalyst) Polyesters can be produced by dehydration polycondensation of a polycarboxylic acid such as an aromatic dicarboxylic acid and a polyol such as an aliphatic glycol, but they may also be produced by transesterification or other methods. Examples of polymerization catalysts for polyesters include antimony compounds, titanium compounds, germanium compounds, manganese compounds, aluminum compounds, magnesium compounds, and calcium compounds. Among these, it is particularly preferable to use at least one selected from titanium compounds and germanium compounds. In the case of polyester using the titanium compound as a polymerization catalyst, the titanium element content in the polyester film is preferably in the range of 50 ppm by mass or less, more preferably 1 to 20 ppm by mass, and even more preferably 2 to 10 ppm by mass. Furthermore, if the polyester film is multilayered, the titanium content of the entire film should be within the above range, but it is especially desirable that the titanium content of each layer be within the above range. By keeping the titanium compound content below the above upper limit, degradation of the polyester during the melt-extrusion process can be prevented, thus preventing the formation of a film with a strong yellowish tint. Furthermore, setting the content above the lower limit improves polymerization efficiency, lowers costs, and makes it easier to obtain a film with sufficient strength.

[0031] As described above, when using polyester containing titanium compounds derived from polymerization catalysts, it is preferable to blend a phosphorus compound into the polyester to reduce the activity of the titanium compounds in order to suppress degradation during the melt extrusion process. As the phosphorus compound, alkyl acid phosphates such as orthophosphoric acid and ethyl acid phosphate are preferred, considering the productivity and thermal stability of the polyester. The phosphorus content in the polyester film is preferably in the range of 1 to 300 ppm by mass, more preferably 3 to 200 ppm by mass, and even more preferably 5 to 100 ppm by mass. By keeping the phosphorus compound content below the above upper limit, it is possible to prevent phosphorus compounds from causing gelation or foreign matter. Furthermore, by setting the value above the lower limit mentioned above, the activity of the titanium compound can be sufficiently reduced, preventing the formation of a yellowish film. Furthermore, if the polyester film is multilayered, it is preferable that the phosphorus content in the layer containing titanium element be within the above range.

[0032] (Prevention of oligomer precipitation) The aforementioned polyester film can also be manufactured using polyester with a low ester cyclic trimer content as a raw material, in order to suppress the amount of ester cyclic trimer precipitation after heat treatment. Various known methods can be used to manufacture polyester with a low ester cyclic trimer content, such as a method of solid-phase polymerization after polyester production. Alternatively, the polyester film may be constructed with three or more layers, and the outermost layer of the polyester film may be made from a polyester raw material with a low ester cyclic trimer content to suppress the amount of ester cyclic trimer precipitated after heat treatment. Alternatively, polyester may be obtained by esterification or transesterification followed by further increasing the reaction temperature and melt polycondensation under reduced pressure.

[0033] (particle) The polyester film may also be compounded with particles primarily for the purpose of providing slipperiness and preventing scratches during each process. When compounding particles, the type of particles to be compounded is not particularly limited as long as they can provide slipperiness, and examples include inorganic particles such as silica, calcium carbonate, magnesium carbonate, barium carbonate, calcium sulfate, calcium phosphate, magnesium phosphate, kaolin, aluminum oxide, zirconium oxide, and titanium oxide, and organic particles such as acrylic resin, styrene resin, urea resin, phenolic resin, epoxy resin, and benzoguanamine resin. Furthermore, precipitated particles obtained by precipitating and finely dispersing a portion of metal compounds such as catalysts during the polyester manufacturing process can also be used. Among these, silica particles and calcium carbonate particles are particularly preferred because they are effective even in small amounts.

[0034] Furthermore, the average particle size is preferably 5.0 μm or less, and more preferably in the range of 0.01 to 3.0 μm. By setting the average particle size to 5.0 μm or less, it is possible to prevent the surface roughness of the film from becoming too large, which reduces the likelihood of problems occurring in various subsequent processing steps. Furthermore, by using particles with an average particle size within the above range, haze can be kept low, making it easier to ensure transparency for the entire laminated polyester film.

[0035] Furthermore, the particle content in the polyester film is preferably less than 5% by mass, more preferably in the range of 0.0003 to 1% by mass, and even more preferably in the range of 0.0005 to 0.5% by mass, relative to the total weight of the polyester film. By keeping the particle content below 5% by mass, it is possible to prevent a high haze and ensure transparency. Therefore, for example, it becomes easier to perform defect inspections such as foreign matter inspections during various inspections. When a polyester film contains no particles, or only a small amount, the transparency of the polyester film increases, resulting in a film with a good appearance. However, its slipperiness may be insufficient. Therefore, it is preferable to improve the slipperiness by adding particles. There are no particular restrictions on the shape of the particles used; they can be spherical, lumpy, rod-shaped, flattened, or any other shape. Furthermore, there are no particular restrictions on their hardness, specific gravity, color, etc. These series of particles may be used in combination of two or more types, as needed.

[0036] The method for adding particles to the polyester film is not particularly limited, and conventionally known methods can be employed. For example, the particles can be added at any stage in the production of the polyester that constitutes each layer of the polyester film, but it is preferable to add them after the esterification or transesterification reaction is completed. Furthermore, when performing melt polycondensation, solid-phase polymerization, etc., after esterification or transesterification, it is more preferable to add the particles after the esterification or transesterification reaction, and before melt polycondensation or solid-phase polymerization. When a polyester film is multilayered, it is preferable to include particles in at least one of the layers, but it is especially preferable to include particles in the outermost layer. For example, in a multilayer structure having an outermost layer, an intermediate layer, and another outermost layer in that order, it is preferable to include particles in each outermost layer.

[0037] (Other additives) In addition to the particles mentioned above, the polyester film of the present invention may contain, as needed, ultraviolet absorbers, antioxidants, antistatic agents, heat stabilizers, lubricants, dyes, pigments, and the like.

[0038] (Thickness of the base film) The thickness of the polyester film is typically in the range of 10 to 300 μm, preferably 15 to 250 μm, and more preferably 20 to 200 μm.

[0039] (Method of manufacturing the base film) As for the manufacturing method of the base film, any commonly known manufacturing method can be used, and there are no particular restrictions. For example, when manufacturing a biaxially oriented polyester film, the aforementioned polyester raw material is melt-extruded from a die using an extruder, and the molten sheet is cooled and solidified with a cooling roll to obtain an unstretched sheet. In this case, it is preferable to improve the adhesion between the sheet and the rotating cooling drum in order to improve the flatness of the sheet, and electrostatic application adhesion or liquid coating adhesion is preferably employed. Next, the obtained unstretched sheet is stretched in one direction using a roll or tenter type stretcher. The stretching temperature is usually 70 to 120°C, preferably 80 to 110°C, and the stretching ratio is usually 2.5 to 7 times, preferably 3.0 to 6 times. Then, in a direction perpendicular to the first stretching direction, it is stretched usually at 70 to 170°C, with a stretching ratio of usually 2.5 to 7 times, preferably 3.0 to 6 times. Subsequently, heat treatment is performed at a temperature of 180 to 270°C under tension or under relaxation of 30% or less to obtain a biaxially oriented film. In the stretching described above, a method can be adopted in which stretching is performed in two or more stages in one direction. In that case, it is preferable to perform the stretching so that the final stretching ratios in both directions fall within the above ranges.

[0040] Furthermore, a simultaneous biaxial stretching method can also be used for the production of polyester film. The simultaneous biaxial stretching method is a method in which the aforementioned unstretched sheet is simultaneously stretched and oriented in the machine direction and width direction under temperature control, usually at 70 to 120°C, preferably 80 to 110°C, with a stretching ratio of 4 to 50 times, preferably 7 to 35 times, and more preferably 10 to 25 times in area ratio. Subsequently, heat treatment is performed at a temperature of 180 to 270°C under tension or under relaxation of 30% or less to obtain a stretched and oriented film. Regarding the simultaneous biaxial stretching apparatus employing the above stretching method, conventionally known stretching methods such as screw type, pantograph type, and linear drive type can be used.

[0041] <Cured resin layer> The above-mentioned cured resin layer (A) is a layer obtained by curing the resin composition (a), and contains the cured product of the resin composition (a). Furthermore, the cured resin layer (A) is a layer that can improve adhesion with the hard coat layer (B), and from this viewpoint, it is preferable that the resin composition (a) contains one or more resin components selected from the group consisting of polyurethane, acrylic resin, and polyester, and a curing component. Polyurethane, acrylic resin, and polyester can each be used individually, or two or more of them may be used in combination.

[0042] [Resin components] (Polyurethane) Examples of polyurethanes include polymer compounds having urethane bonds within their molecules, which can be synthesized, for example, by the reaction of a polyol and a polyisocyanate. Examples of the aforementioned polyols include polycarbonate polyols, polyester polyols, polyether polyols, polyolefin polyols, and acrylic polyols. Examples of the aforementioned polyisocyanates include aromatic diisocyanates such as tolylene diisocyanate, xylylene diisocyanate, methylenediphenyl diisocyanate, phenylene diisocyanate, naphthalene diisocyanate, and tolidine diisocyanate; aliphatic diisocyanates having an aromatic ring such as α,α,α',α'-tetramethylxylylene diisocyanate; aliphatic diisocyanates such as methylene diisocyanate, propylene diisocyanate, lysine diisocyanate, trimethylhexamethylene diisocyanate, and hexamethylene diisocyanate; and alicyclic diisocyanates such as cyclohexane diisocyanate, methylcyclohexane diisocyanate, isophorone diisocyanate, dicyclohexylmethane diisocyanate, and isopropylidene dicyclohexyl diisocyanate.

[0043] (Acrylic resin) Examples of the acrylic resin include polymers composed of polymerizable monomers having carbon-carbon double bonds, such as acrylic monomers or methacrylic monomers. These may be homopolymers or copolymers. Furthermore, copolymers of these polymers with other polymers (e.g., polyester, polyurethane, etc.), such as block copolymers or graft copolymers, are also included. Furthermore, the product also includes polymers (and sometimes mixtures of polymers) obtained by polymerizing polymerizable monomers having carbon-carbon double bonds in a polyester solution or polyester dispersion. Similarly, polymers (and sometimes mixtures of polymers) obtained by polymerizing polymerizable monomers having carbon-carbon double bonds in a polyurethane solution or dispersion are also included. Similarly, polymers (and possibly polymer mixtures) obtained by polymerizing polymerizable monomers having carbon-carbon double bonds in other polymer solutions or dispersions are also included.

[0044] Examples of polymerizable monomers having carbon-carbon double bonds include various carboxyl group-containing monomers and their salts, such as acrylic acid, methacrylic acid, crotonic acid, itaconic acid, fumaric acid, maleic acid, and citraconic acid; various hydroxyl group-containing monomers such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, monobutyl hydroxyl fumarate, and monobutyl hydroxyitaconate; various (meth)acrylic acid esters such as methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, and lauryl (meth)acrylate; and (meth)acrylamide, diacetone acrylamide, and N-methylol acrylate. Examples include various nitrogen-containing vinyl monomers such as luamide or (meth)acrylonitrile; various styrene derivatives such as styrene, α-methylstyrene, divinylbenzene, and vinyltoluene; various vinyl esters such as vinyl acetate and vinyl propionate; various silicon-containing polymerizable monomers such as γ-methacryloxypropyltrimethoxysilane, vinyltrimethoxysilane, and Chisso Corporation's "Sylaplane FM-07" (methacryloyl silicon macromer); phosphorus-containing vinyl monomers; various vinyl halides such as vinyl chloride, pyridene chloride, vinyl fluoride, vinylidene fluoride, trifluorochloroethylene, tetrafluoroethylene, chlorotrifluoroethylene, and hexafluoropropylene; and various conjugated dienes such as butadiene.

[0045] (polyester) Examples of the aforementioned polyester include those having ester bonds in the main chain or side chains, such as polyesters obtained by polycondensation of a polycarboxylic acid component and a diol component.

[0046] Examples of the polycarboxylic acid components include terephthalic acid, isophthalic acid, orthophthalic acid, phthalic acid, 2,5-dimethylterephthalic acid, 5-sodium sulfisoisophthalic acid, 1,4-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, biphenyldicarboxylic acid, 1,2-bisphenoxyethane-p,p'-dicarboxylic acid, phenylindanedicarboxylic acid, succinic acid, adipic acid, sebacic acid, dodecanedionic acid, dimer acid, 1,3-cyclopentanedicarboxylic acid, 1,2-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, and other dicarboxylic acids, trimellitic acid, trimellitic anhydride, pyromellitic acid, pyromellitic anhydride, 4-methylcyclohexene-1,2,3-tricarboxylic acid, and trimesic acid. Examples of divalent or more polycarboxylic acids include 1,2,3,4-butanetetracarboxylic acid, 1,2,3,4-pentanetetracarboxylic acid, 3,3',4,4'-benzophenonetetracarboxylic acid, 5-(2,5-dioxotetrahydrofurfuryl)-3-methyl-3-cyclohexene-1,2-dicarboxylic acid, 5-(2,5-dioxotetrahydrofurfuryl)-3-cyclohexene-1,2-dicarboxylic acid, cyclopentanetetracarboxylic acid, 2,3,6,7-naphthalenetetracarboxylic acid, 1,2,5,6-naphthalenetetracarboxylic acid, ethylene glycol bistrimellitate, 2,2',3,3'-diphenyltetracarboxylic acid, thiophene-2,3,4,5-tetracarboxylic acid, and ethylenetetracarboxylic acid.

[0047] Examples of the diol component include ethylene glycol, diethylene glycol, polyethylene glycol, propylene glycol, polypropylene glycol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 2,4-dimethyl-2-ethylhexane-1,3-diol, neopentyl glycol, 2-ethyl-2-butyl-1,3-propanediol, 2-ethyl-2-isobutyl-1,3-propanediol, 3-methyl-1,5-pentanediol, 2,2,4- Examples include methyl-1,6-hexanediol, 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, 2,2,4,4-tetramethyl-1,3-cyclobutanediol, 4,4'-thiodiphenol, bisphenol A, 4,4'-methylenediphenol, 4,4'-(2-norbornylidene)diphenol, 4,4'-dihydroxybiphenol, o-,m-, and p-dihydroxybenzene, 4,4'-isopropylidenephenol, 4,4'-isopropylidenebinediol, cyclopentane-1,2-diol, cyclohexane-1,2-diol, and cyclohexane-1,4-diol.

[0048] [Curing component] Examples of the curing components include melamine compounds, oxazoline compounds, epoxy compounds, isocyanate compounds, carbodiimide compounds, and silane coupling compounds. Among these, oxazoline compounds, epoxy compounds, isocyanate compounds, and carbodiimide compounds are preferably used from the viewpoint of improving adhesion to the hard coat layer, with oxazoline compounds, isocyanate compounds, and carbodiimide compounds being particularly preferred. When using two or more crosslinking agents, combinations of melamine compounds and oxazoline compounds, or melamine compounds and epoxy compounds are preferably used from the viewpoint of further suppressing the precipitation of ester cyclic trimers.

[0049] (Melamine compound) Examples of the melamine compound include compounds having a melamine skeleton in the compound. For example, alkylolated melamine derivatives, compounds obtained by reacting alkylolated melamine derivatives with alcohol to partially or completely etherify them, and mixtures thereof can be used. Suitable alcohols for etherification include, for example, methyl alcohol, ethyl alcohol, isopropyl alcohol, n-butanol, and isobutanol. Furthermore, the melamine compound may be a monomer or a polymer of two or more commensals, or a mixture thereof may be used. Furthermore, melamine can be used in which urea or other substances are co-condensed with a portion of the melamine, and catalysts can also be used to increase the reactivity of the melamine compound.

[0050] (Oxazoline compounds) Examples of the oxazoline compound include compounds having an oxazoline group in the molecule, with polymers containing an oxazoline group being particularly preferred. These can be produced by polymerization of an addition-polymerizable oxazoline group-containing monomer alone or with other monomers. Examples of the addition-polymerizable oxazoline group-containing monomers include 2-vinyl-2-oxazoline, 2-vinyl-4-methyl-2-oxazoline, 2-vinyl-5-methyl-2-oxazoline, 2-isopropenyl-2-oxazoline, 2-isopropenyl-4-methyl-2-oxazoline, and 2-isopropenyl-5-ethyl-2-oxazoline. One or more of these can be used. Among these, 2-isopropenyl-2-oxazoline is preferred because it is readily available industrially. Other monomers are not limited as long as they are copolymerizable with addition-polymerizable oxazoline group-containing monomers, for example (meth)acrylic acid esters such as alkyl (meth)acrylates (alkyl groups include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, t-butyl, 2-ethylhexyl, and cyclohexyl groups); unsaturated carboxylic acids such as acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, crotonic acid, styrenesulfonic acid and their salts (sodium salt, potassium salt, ammonium salt, tertiary amine salt, etc.); unsaturated nitriles such as acrylonitrile and methacrylonitrile; (meth)acrylamide, N-alkyl(meth)acrylamide Examples of unsaturated amides include lylamide, N,N-dialkyl(meth)acrylamide (alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, t-butyl, 2-ethylhexyl, and cyclohexyl); vinyl esters such as vinyl acetate and vinyl propionate; vinyl ethers such as methyl vinyl ether and ethyl vinyl ether; α-olefins such as ethylene and propylene; halogen-containing α,β-unsaturated monomers such as vinyl chloride, vinylidene chloride, and vinyl fluoride; and α,β-unsaturated aromatic monomers such as styrene and α-methylstyrene. One or more of these monomers can be used.

[0051] The amount of oxazoline groups in the oxazoline compound is typically in the range of 0.5 to 10 mmol / g, preferably 2 to 9 mmol / g, and more preferably 4 to 7 mmol / g. Using the compound within this range improves adhesion to the hard coat layer and is also effective in preventing the precipitation of ester cyclic trimers on the film surface due to heating.

[0052] (Epoxy compound) Examples of epoxy compounds include compounds having epoxy groups in their molecules, such as condensates of epichlorohydrin with hydroxyl or amino groups of ethylene glycol, polyethylene glycol, glycerin, polyglycerin, bisphenol A, etc., and include polyepoxy compounds, diepoxy compounds, monoepoxy compounds, glycidylamine compounds, etc.

[0053] Examples of the polyepoxy compounds include sorbitol polyglycidyl ether, polyglycerol polyglycidyl ether, pentaerythritol polyglycidyl ether, diglycerol polyglycidyl ether, triglycidyl tris(2-hydroxyethyl) isocyanate, glycerol polyglycidyl ether, and trimethylolpropane polyglycidyl ether.

[0054] Examples of the aforementioned diepoxy compounds include neopentyl glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, resorcinol diglycidyl ether, ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, and polytetramethylene glycol diglycidyl ether.

[0055] Examples of the monoepoxy compound include allyl glycidyl ether, 2-ethylhexyl glycidyl ether, and phenyl glycidyl ether.

[0056] Examples of the glycidylamine compounds include N,N,N',N'-tetraglycidyl-m-xylylenediamine and 1,3-bis(N,N-diglycidylamino)cyclohexane.

[0057] (Isocyanate compounds) Examples of the isocyanate-based compounds include compounds having an isocyanate derivative structure, such as isocyanates or blocked isocyanates. Examples of the isocyanates include aromatic isocyanates such as tolylene diisocyanate, xylylene diisocyanate, methylenediphenyl diisocyanate, phenylene diisocyanate, and naphthalene diisocyanate; aliphatic isocyanates having an aromatic ring such as α,α,α',α'-tetramethylxylylene diisocyanate; aliphatic isocyanates such as methylene diisocyanate, propylene diisocyanate, lysine diisocyanate, trimethylhexamethylene diisocyanate, and hexamethylene diisocyanate; and alicyclic isocyanates such as cyclohexane diisocyanate, methylcyclohexane diisocyanate, isophorone diisocyanate, methylenebis(4-cyclohexyl isocyanate), and isopropylidene dicyclohexyl diisocyanate. Furthermore, polymers and derivatives of these isocyanates, such as biuretized, isocyanurateized, uretdioneized, and carbodiimide-modified products, are also mentioned. These may be used individually or in combination of multiple types. Among the above isocyanates, aliphatic isocyanates or alicyclic isocyanates are more preferred than aromatic isocyanates in order to avoid yellowing due to ultraviolet light.

[0058] When used in the form of the blocked isocyanate, the blocking agents include, for example, phenolic compounds such as bisulfites, phenol, cresol, and ethylphenol; alcoholic compounds such as propylene glycol monomethyl ether, ethylene glycol, benzyl alcohol, methanol, and ethanol; active methylene compounds such as dimethyl malonate, diethyl malonate, methyl acetoacetate, ethyl acetoacetate, and acetylacetone; mercaptan compounds such as butyl mercaptan and dodecyl mercaptan; lactam compounds such as ε-caprolactam and δ-valerolactam; amine compounds such as diphenylaniline, aniline, and ethyleneimine; acid amide compounds such as acetanilide and acetic acid amide; and oxime compounds such as formaldehyde, acetaldehyde oxime, acetone oxime, methyl ethyl ketone oxime, and cyclohexanone oxime. These may be used individually or in combination of two or more.

[0059] Furthermore, the isocyanate compounds may be used individually or as mixtures or binders with various polymers. In order to improve the dispersibility and crosslinking properties of the isocyanate compounds, it is preferable to use mixtures or binders with polyester resins or urethane resins.

[0060] (Carbodiimide compounds) Examples of the carbodiimide compounds mentioned above include compounds having a carbodiimide structure, and are used to improve adhesion to the hard coat layer and to improve the moisture and heat resistance of the cured resin layer. Carbodiimide compounds can be synthesized using conventionally known techniques, and generally, a condensation reaction of diisocyanate compounds is used. The aforementioned diisocyanate compound is not particularly limited, and both aromatic and aliphatic compounds can be used. Specifically, examples include tolylene diisocyanate, xylene diisocyanate, diphenylmethane diisocyanate, phenylene diisocyanate, naphthalene diisocyanate, hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, cyclohexane diisocyanate, methylcyclohexane diisocyanate, isophorone diisocyanate, dicyclohexyl diisocyanate, and dicyclohexylmethane diisocyanate.

[0061] The amount of carbodiimide groups contained in the carbodiimide compound is typically in the range of 100 to 1000, preferably 250 to 800, and more preferably 300 to 650, in terms of carbodiimide equivalents (weight [g] of the carbodiimide compound required to give 1 mol of carbodiimide groups). Using the compound within this range improves the durability of the cured resin layer.

[0062] Other components contained in the above resin composition (a) include, for example, defoaming agents, coating properties improvers, thickeners, organic lubricants, antistatic agents, ultraviolet absorbers, antioxidants, foaming agents, dyes, pigments, and the like.

[0063] The content of the resin component in the resin composition (a) is usually 5% by mass or more, preferably 10 to 80% by mass, more preferably 30 to 80% by mass, and particularly preferably 40 to 80% by mass, based on solid content. Furthermore, the content of the curing component in the resin composition (a) is usually 5% by mass or more, preferably 5 to 80% by mass, more preferably 10 to 70% by mass, and particularly preferably 10 to 60% by mass.

[0064] (Method for forming a cured resin layer) As a method for forming the cured resin layer (A), for example, a method of applying a coating liquid for forming a cured resin layer (hereinafter sometimes simply referred to as "coating liquid") containing the resin composition (a) onto a substrate film, drying it, and then curing it is preferred. As a coating method, conventionally known coating methods such as gravure coating, kiss coating, dip coating, spray coating, curtain coating, air knife coating, blade coating, reverse roll coating, bar coating, lip coating, etc. can be used. Among these, the gravure coating method, particularly the reverse gravure method, is preferred because it allows for coating in a roll-to-roll manner and enables uniform application.

[0065] Furthermore, a preferred method for dissolving or dispersing the curable resin composition (a) contained in the coating liquid in an organic solvent is to stir and disperse them under heating. By heating the coating liquid, the solubility of each component in the curable resin composition can be improved, and deterioration of the coating appearance due to undissolved substances can be suppressed.

[0066] The solid content concentration of the curable resin composition (a) contained in the coating solution is preferably in the range of 1 part by mass or more and 50 parts by mass or less when the total amount is 100 parts by mass. By adjusting the solid content concentration of the coating solution to 1 part by mass or more, it is possible to suppress the decrease in productivity due to the length of the drying time after coating. On the other hand, by adjusting the solid content concentration of the coating solution to 50 parts by mass or less, it is possible to prevent deterioration of leveling properties due to an increase in the viscosity of the coating solution and the resulting deterioration of the coating appearance.

[0067] (Thickness of the cured resin layer) The thickness of the cured resin layer (A) after curing is preferably 0.001 to 1 μm. Furthermore, the lower limit of the thickness of the cured resin layer (A) after curing is preferably 0.01 μm or more, and more preferably 0.02 μm or more. Furthermore, the upper limit of the thickness of the cured resin layer (A) is preferably 0.5 μm or less, more preferably 0.3 μm or less, and even more preferably 0.2 μm or less.

[0068] Furthermore, if pre-drying is required, such as when an organic solvent is incorporated into the coating solution, methods for coating and drying the solution on the substrate film include known methods such as hot air drying and infrared heaters, but hot air drying, which has a fast drying speed, is preferred. Furthermore, it is preferable to perform the drying after application under conditions of a temperature between 40°C and 120°C, and particularly preferably with a lower limit of 45°C and an upper limit of 80°C. By setting the drying temperature to 40°C or higher, it is possible to prevent problems such as insufficient removal of organic solvents contained in the coating solution or the occurrence of brushing. On the other hand, if the drying temperature does not exceed 120°C, it is possible to prevent the occurrence of minute defects in the cured resin layer, such as minute coating defects caused by bubbles, minute repellencies, and cracks, thereby preventing appearance defects. Furthermore, it is possible to prevent the film from shrinking strongly due to heat, which can lead to deterioration of the film's flatness due to heat wrinkles, inability to obtain uniform elongation during molding, and localized elongation that can cause the film to break.

[0069] The tension applied to the film during drying is preferably in the range of 50 to 300 N / m, and more preferably with a lower limit of 100 N / m or more and an upper limit of 250 N / m or less. When the tension of the film is 50 N / m or more, the film does not meander as it moves, making it easier to apply the coating liquid. On the other hand, if the tension of the film is 300 N / m or less, wrinkles will not form in the film, and there will be no deterioration in flatness or appearance of the wound film.

[0070] <Hard coat layer> The hard coat layer (B) described above is a layer obtained by curing the resin composition (b) (hereinafter sometimes referred to as "hard coat agent"), and has a higher surface hardness (JIS K 5600-5-4:1999) than the base film, and contains cured resin composition (b). Examples of resin components (polymerizable compounds) contained in the resin composition (b) include monofunctional (meth)acrylates, polyfunctional (meth)acrylates, and reactive silicon compounds such as tetraethoxysilane. Among these, active energy ray curable (meth)acrylates are particularly preferred.

[0071] Examples of the active energy ray-curable (meth)acrylate include active energy ray-curable monofunctional (meth)acrylate, difunctional (meth)acrylate, and trifunctional or more polyfunctional (meth)acrylate. These may be used individually or as a mixture of two or more types.

[0072] Examples of the monofunctional (meth)acrylates include alkyl (meth)acrylates such as methyl (meth)acrylate, n-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, stearyl (meth)acrylate, cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, hydroxyalkyl (meth)acrylates such as hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, hydroxybutyl (meth)acrylate, methoxyethyl (meth)acrylate, ethoxyethyl (meth)acrylate, methoxypropyl (meth)acrylate, and ethoxypropyl Examples include alkoxyalkyl (meth)acrylates such as (meth)acrylate, aromatic (meth)acrylates such as benzyl (meth)acrylate and phenoxyethyl (meth)acrylate, amino group-containing (meth)acrylates such as diaminoethyl (meth)acrylate and diethylaminoethyl (meth)acrylate, methoxyethylene glycol (meth)acrylate, phenoxyethylene glycol (meth)acrylate, ethylene oxide-modified (meth)acrylates such as phenylphenol ethylene oxide-modified (meth)acrylate, glycidyl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, and (meth)acrylic acid.

[0073] Examples of the aforementioned difunctional (meth)acrylates include alkane diol di(meth)acrylates such as 1,4-butanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, and tricyclodecanedimethylol di(meth)acrylate; bisphenol-modified di(meth)acrylates such as bisphenol A ethylene oxide-modified di(meth)acrylate and bisphenol F ethylene oxide-modified di(meth)acrylate; polyethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, urethane di(meth)acrylate, and epoxy di(meth)acrylate.

[0074] Examples of the three- or more-functional polyfunctional (meth)acrylates include dipentaerythritol hexa(meth)acrylate, pentaerythritol tetra(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, pentaerythritol tri(meth)acrylate, trimethylolpropane tri(meth)acrylate, isocyanuric acid-modified tri(meth)acrylate such as ethylene oxide-modified isocyanurate tri(meth)acrylate and ε-caprolactone-modified tris(acrooxyethyl)isocyanurate, as well as urethane (meth)acrylates such as pentaerythritol triacrylate hexamethylene diisocyanate urethane prepolymer, pentaerythritol triacrylate toluene diisocyanate urethane prepolymer, and dipentaerythritol pentaacrylate hexamethylene diisocyanate urethane prepolymer.

[0075] Among the above, urethane (meth)acrylate is particularly preferred from the viewpoint of hardness, toughness, and flexibility, and it is preferable that the hard coat layer contains a cured product of urethane (meth)acrylate.

[0076] Other components included in the above resin composition (b) include, for example, inorganic or organic fine particles, polymerization initiators, polymerization inhibitors, antioxidants, antistatic agents, dispersants, surfactants, light stabilizers, and leveling agents. The resin composition (b) may or may not contain a leveling agent, but in the present invention, even if a leveling agent is not included or is included in small amounts, the contact angle can be lowered while maintaining good surface smoothness. Examples of leveling agents include acrylic leveling agents, silicone leveling agents, and fluorine leveling agents, but acrylic leveling agents are preferred. The content of the leveling agent is, for example, 2 parts by mass or less, preferably 1.5 parts by mass or less, per 100 parts by mass of the resin component (polymerizable compound). Furthermore, the above content may be 0 parts by mass or more, but if a leveling agent is included, its content is preferably 0.1 parts by mass or more, and more preferably 0.3 parts by mass or more.

[0077] (Method for forming a hard coat layer) The method for forming the hard coat layer is not particularly limited, and it can be suitably formed by applying the above-mentioned resin composition (b) (hard coat agent). More specifically, general wet coating methods such as roll coating and die coating can be employed, and the formed hard coat layer can be subjected to curing reactions by heating or irradiation with active energy rays such as ultraviolet light or electron beams as needed.

[0078] (water contact angle) The hard coat layer of the hard coat film of the present invention preferably has a water contact angle of less than 85°, and more preferably 70° or less. The water contact angle is determined by the static droplet method described in JIS R3257:1999. The water contact angle is a value that can be determined by the following equation (1) when a water droplet is placed on the surface of a hard coat layer and is in equilibrium under that atmosphere. Generally, it is used as an indicator to judge the wettability of a solid surface. In other words, the smaller the value of the water contact angle, the better the wettability of the solid surface.

[0079] γS = γLcosθ + γSL (1) (In the above formula (1), γS represents the surface tension of the solid, γL represents the surface tension of the liquid, γSL represents the solid / liquid interfacial tension, and θ represents the contact angle.)

[0080] The above formula is called the "Young's formula", and the angle formed between the liquid surface and the solid surface is defined as the "contact angle". The water contact angle can be measured by widely commercially available devices. The specific numerical range and measurement method of the water contact angle will be described in the Examples section.

[0081] <Method for producing a polyester film with a hard coat layer, particularly preferred form> In the present invention, from the viewpoint of adjusting the number of defects having a maximum diameter of 0.5 μm or more to be 2 pieces / m 2 below, it is particularly preferable to produce a hard coat film by a method having the following steps (1) to (4) in this order.

[0082] <Step (1)> Step (1) is a step of forming a cured resin layer on at least one surface of the polyester film. Specifically, the method for forming the cured resin layer described above may be adopted. The cured resin layer obtained in step (1) preferably contains a cured product of a resin composition containing at least one resin component selected from polyurethane, acrylic resin, and polyester and a curing component. The resin component and the curing component are as described above.

[0083] <Step (2)> Step (2) is a step of applying an organic solvent to the cured resin layer. From the viewpoint of reducing the number of defects, particularly, an organic solvent having a solubility parameter (SP value) of 16 to 30 MPa 1 / 2 and a boiling point within the range of 55 to 160°C is preferably used. The solubility parameter (SP value) is 16 to 30 MPa 1 / 2Examples of organic solvents that meet the following criteria and have a boiling point in the range of 55 to 160°C include 2-propanol (SP value: 23.5, boiling point: 82.4°C), methyl isobutyl ketone (SP value: 17.2, boiling point: 115.9°C), cyclohexanone (SP value: 20.3, boiling point: 155.7°C), ethyl acetate (SP value: 18.6, boiling point: 77.1°C), methyl ethyl ketone (SP value: 19.0, boiling point: 79.6°C), and toluene (SP value: 18.2, boiling point: 110.6°C). These organic solvents can be used individually or in combination of two or more.

[0084] Among these, ethyl acetate, methyl ethyl ketone, and toluene are preferred from the viewpoint of coating suitability due to an appropriate evaporation rate and reduction of the number of defects, and it is particularly preferable to use two or more of these in combination. Furthermore, from the above viewpoint, it is preferable that the organic solvent contains methyl ethyl ketone, and it is preferable that the content of methyl ethyl ketone in the organic solvent is 50% by mass or less. If the content of methyl ethyl ketone is within this range, the occurrence of coating streaks due to the dissolution of the cured resin layer can be suppressed. The lower limit of the content of methyl ethyl ketone is not particularly limited, but it is preferably 20% by mass or more, and more preferably 30% by mass or more. Furthermore, the organic solvent is preferably a mixed solvent containing toluene in addition to methyl ethyl ketone, and the toluene content in the organic solvent is preferably 40% by mass or more and 80% by mass or less, and more preferably 50% by mass or more and 70% by mass or less. The term "SP value" refers to the "solubility parameter value," specifically the Hansen solubility parameter calculated using the formula shown in "A User's Handbook, Second Edition, CmHansen (2007), Taylor and Francis Group, LLC (HSPiP Manual)," and the SP value used is calculated using the following formula. (SP value)² = (δHd)² + (δHp)² + (δHh)² Hd: Distribution Contribution Hp: Polarity deviation Hh: Hydrogen bond contribution

[0085] The application of the organic solvent may be carried out by any of the methods listed above as methods for applying the coating liquid for hardening the resin layer, but it is preferable to apply the organic solvent by applying shear force. By applying the organic solvent by applying shear force, foreign matter can be easily swept away, and foreign matter can be efficiently removed by applying the organic solvent. Specifically, it is preferable to carry out the coating using one of the following methods: bar coating, gravure coating, or roll coating, with the gravure coating method being the most preferable.

[0086] <Process (3)> Step (3) is a step of drying off the applied organic solvent, and methods for drying off include known methods such as hot air drying and drying with an infrared heater. Among these, hot air drying, which has a fast drying speed, is preferred.

[0087] <Process (4)> Step (4) is a step of forming a hard coat layer on the cured resin layer of the polyester film having the cured resin layer after drying and removal, and specifically, the method for forming the hard coat layer described above may be used. The hard coat layer obtained in step (4) preferably contains a cured urethane (meth)acrylate. The cured urethane (meth)acrylate is as described above. Furthermore, in terms of productivity, it is preferable to perform steps (3) and (4) continuously in the method for producing the polyester film with a hard coat layer of the present invention.

[0088] <Film for the casting process> Because the hard coat film of the present invention has excellent surface smoothness, it can be suitably used as a support in the casting process. More specifically, it can be suitably used as a support in the casting process, in which a film is formed by applying a polymer-containing liquid onto a support and then removing the solvent. Furthermore, because the hard coat film of the present invention has excellent surface smoothness, it is particularly preferable to use it as a support for the polyimide casting process. [Examples]

[0089] The present invention will be described more specifically below based on examples and comparative examples, but the present invention is not limited in any way by the following examples and comparative examples.

[0090] [Measurement methods and evaluation methods] The measurement and evaluation methods used in the examples and comparative examples are as follows:

[0091] (1) Number of defects A 1000mm piece of hard coat film is cut, and defects are visually inspected while transmitting and reflecting a three-wavelength fluorescent light. The number of defects is then divided by the film width and calculated per square meter. 2 This was used as the value.

[0092] (2) Water contact angle The contact angle of the hard coat layer was determined by the droplet method using a CA-D·A contact angle meter manufactured by Kyowa Interface Science Co., Ltd.

[0093] (3) Appearance evaluation The hard coat film was evaluated for its appearance according to the following criteria. 《Judgment criteria》 ○: Number of defects ≤ 2.0 pieces / m 2 ×: Defect count > 2.0 pieces / m 2

[0094] The materials used in the examples and comparative examples are as follows:

[0095] (1) Raw materials for polyester film substrates Polyester (1) • Polyethylene terephthalate homopolymer chips (intrinsic viscosity: 0.6 dl / g) Polyester (2) • A polyethylene terephthalate homopolymer chip containing 3000 ppm by mass of amorphous silica with an average particle size of 2.3 μm (intrinsic viscosity: 0.6 dl / g)

[0096] (2) Raw materials for forming the cured resin layer (content ratio when the total mass is 100% by mass) [1] Resin component (65% by mass) • Polyester resin (35% by mass) • Acrylic resin (30% by mass) [2] Curing component (30% by mass) • Melamine compounds • Epoxy compounds • Oxazoline compounds [3] Other (5% by mass) • Surfactants • Silica particles

[0097] (3) Raw materials for forming a hard coat layer [1] Raw material for hard coat layer formation (coating liquid 1) • Urethane (meth)acrylate A: 27.01 parts by mass (Preparation method) In a four-necked flask equipped with a thermometer, stirrer, water-cooled condenser, and nitrogen gas inlet, 6.6 parts by mass of isophorone diisocyanate (a1-1), 94 parts by mass of a mixture of dipentaerythritol pentaerythritol and dipentaerythritol hexaacrylate (a1-2) with a hydroxyl value of 50 mg KOH / g (a1-1 / a1-2 = 0.28 / 0.72 (mol / mol)), 0.6 parts by mass of 2,6-di-tert-butylcresol as a polymerization inhibitor, and 0.05 parts by mass of dibutyltin dilaurate as a reaction catalyst were charged. The reaction was carried out at 60°C, and the reaction was stopped when the remaining isocyanate group was 0.3%, yielding urethane acrylate A with an acryloyl equivalent of 107 g / eq. The obtained urethane (meth)acrylate A had a mass-average molecular weight of 1,600 and a viscosity of 1,500 mPa·s at 60°C.

[0098] • Urethane (meth)acrylate B: 6.75 parts by mass (Preparation method) In a four-necked flask equipped with a thermometer, stirrer, water-cooled condenser, and nitrogen gas inlet, 29.3 parts by mass of an isocyanurate compound mainly composed of a trimer of hexamethylene diisocyanate (product name: Coronate HX, manufactured by Tosoh Corporation, isocyanate group content: 21.0%) (b1-1) and 70.7 parts by mass of a mixture of pentaerythritol triacrylate and pentaerythritol tetraacrylate (hydroxyl value 120 mg KOH / g; b1-2) (b1-1 / b1-2 = 0.25 / 0.75) were added. (mol / mol) 0.06 parts by mass of 2,6-di-tert-butylcresol as a polymerization inhibitor and 0.02 parts by mass of dibutyltin dilaurate as a reaction catalyst were charged and the reaction was carried out at 60°C until the residual isocyanate group was reduced to 0.3% or less, at which point the reaction was terminated to obtain a mixture of 70 parts by mass of a urethane (meth)acrylate compound (acryloyl equivalent 155 g / eq; mass-average molecular weight 10,500) and 30 parts by mass of pentaerythritol tetraacrylate (acryloyl equivalent 88 g / eq).

[0099] • Photopolymerization initiator (IGM Resins BV, product name "Omnirad127"): 1.17 parts by mass • (meth)acrylic copolymer (MMA copolymer, polymer mainly composed of alkyl methacrylate): 3.38 parts by mass • Organic solvent (methyl ethyl ketone: 41.70 parts by mass / propylene glycol monomethyl ether: 19.88 parts by mass)

[0100] [2] Raw materials for forming a hard coat layer (coating liquid 2) Urethane (meth)acrylate A: 25.86 parts by mass Urethane (meth)acrylate B: 7.54 parts by mass

[0101] • Photopolymerization initiator (IGM Resins BV, product name "Omnirad127"): 1.13 parts by mass • (meth)acrylic copolymer (MMA copolymer, polymer mainly composed of alkyl methacrylate): 3.23 parts by mass • Acrylic leveling agent (manufactured by Kyoeisha Chemical Co., Ltd., product name "Polyflow No. 75"): 0.11 parts by mass • Organic solvent (methyl ethyl ketone: 41.88 parts by mass / propylene glycol monomethyl ether: 20.25 parts by mass)

[0102] [3] Raw materials for forming a hard coat layer (coating liquid 3) Urethane (meth)acrylate A: 25.74 parts by mass Urethane (meth)acrylate B: 7.51 parts by mass

[0103] • Photopolymerization initiator (IGM Resins BV, product name "Omnirad127"): 1.13 parts by mass • (meth)acrylic copolymer (MMA copolymer, polymer mainly composed of alkyl methacrylate): 3.22 parts by mass • Acrylic leveling agent (manufactured by Kyoeisha Chemical Co., Ltd., product name "Polyflow No. 75"): 0.23 parts by mass • Organic solvent (methyl ethyl ketone: 41.93 parts by mass / propylene glycol monomethyl ether: 20.25 parts by mass)

[0104] [4] Raw materials for forming a hard coat layer (coating liquid 4) • (Meth)acrylate (manufactured by Aica Kogyo Co., Ltd., product name "Aica Aitron (registered trademark)", product number "Z-876AF")): 100 parts by mass (45% by mass of ethyl acetate, 15% by mass of propylene glycol monomethyl ether)

[0105] [Example 1] A blend of polyester (1) and polyester (2) in a weight ratio of 85 / 15 was used as the raw material for layer A, and polyester (1) alone was used as the raw material for layer B. Both were supplied to an extruder, heated and melted at 285°C, and layer A was divided into two to form the outermost layer (surface layer), and layer B to form the middle layer, resulting in a two-type, three-layer structure (A / B / A). The extrusion conditions were set so that the thickness composition ratio A / B / A = 1 / 15 / 1, and the film was co-extruded. The film was then cooled and solidified while in close contact with a mirror-cooled drum with a surface temperature of 40-50°C to produce an unstretched film.

[0106] This film was stretched 3.1 times in the longitudinal direction while passing through a group of heated rolls at 86°C to obtain a uniaxially oriented film. The above-mentioned raw material for forming the cured resin layer was applied as a solvent to one side of this uniaxially oriented film, and then this film was guided into a tenter stretcher and stretched 4.2 times in the width direction at 135°C, followed by heat treatment at 217°C, and then a 2% relaxation treatment in the width direction was performed to obtain a biaxially oriented film with a thickness of 188 μm, thereby obtaining a polyester film having a cured resin layer (A) (thickness: 0.1 μm).

[0107] Next, an organic solvent mixture of 40 parts by mass of methyl ethyl ketone and 60 parts by mass of toluene was applied to the cured resin layer surface of the polyester film using a #200 gravure coater. After drying at 30°C for 8 seconds to remove the organic solvent, the hard coat layer forming raw material (coating solution 1) was continuously applied using a #90 gravure coater and dried at 70°C for 48 seconds to remove the organic solvent. Next, using a high-pressure mercury lamp, 200 mJ / cm² was measured. 2 By irradiating with ultraviolet light, a hard coat film 1 having a hard coat layer with a thickness of 4.5 μm was obtained. The evaluation results for this hard coat film 1 are shown in Table 1.

[0108] [Example 2] A hard coat film 2 was obtained in the same manner as in Example 1, except that the hard coat layer forming raw material (coating liquid 1) was changed to a hard coat layer forming raw material (coating liquid 2). The evaluation results for this hard coat film 2 are shown in Table 1.

[0109] [Example 3] A hard coat film 3 was obtained in the same manner as in Example 1, except that the hard coat layer forming raw material (coating liquid 1) was changed to a hard coat layer forming raw material (coating liquid 3). The evaluation results for this hard coat film 3 are shown in Table 1.

[0110] [Example 4] A hard coat film 4 was obtained in the same manner as in Example 1, except that the hard coat layer forming raw material (coating liquid 1) was changed to a hard coat layer forming raw material (coating liquid 4). The evaluation results for this hard coat film 4 are shown in Table 1.

[0111] [Comparative Example 1] A hard coat film 5 was obtained in the same manner as in Example 1, except that the step of applying an organic solvent to the cured resin layer surface of the polyester film before forming the hard coat layer (coating step) was omitted. The evaluation results for this hard coat film 5 are shown in Table 1.

[0112] [Comparative Example 2] A hard coat film 6 was obtained in the same manner as in Example 2, except that the step of applying an organic solvent to the cured resin layer surface of the polyester film before forming the hard coat layer (coating step) was omitted. The evaluation results for this hard coat film 6 are shown in Table 1.

[0113] [Table 1] *This represents the number of parts of the leveling agent when the total amount of urethane acrylate A and B is 100 parts by mass. [Industrial applicability]

[0114] Despite having a cured resin layer formed to improve adhesion with the hard coat layer, the hard coat film of the present invention has an extremely low number of defects, which are controlled to a high level, resulting in extremely excellent surface smoothness. Furthermore, the hard coat film of the present invention can also provide excellent wettability. Therefore, the hard coat film of the present invention can be particularly suitable for use in the casting process.

Claims

1. A method for manufacturing a polyester film with a hard coat layer, comprising the following steps (1) to (4) in this order, (1) A step of forming a cured resin layer on at least one surface of the polyester film. (2) Step of applying an organic solvent to the cured resin layer. (3) A step of drying off the applied organic solvent. (4) A step of forming a hard coat layer on the hard resin layer of the polyester film having the hardened resin layer after drying and removal. The solubility parameter (SP value) of the aforementioned organic solvent is 16 to 30 MPa. １／２ A method for manufacturing a polyester film with a hard coat layer, wherein the boiling point of the film is in the range of 55 to 160°C.

2. The method for producing a polyester film with a hard coat layer according to claim 1, wherein the organic solvent contains methyl ethyl ketone, and the content of the methyl ethyl ketone is 50% by mass or less.

3. The method for producing a polyester film with a hard coat layer according to claim 2, wherein the organic solvent is further a mixed solvent containing toluene.

4. The method for producing a polyester film with a hard coat layer according to any one of claims 1 to 3, wherein the formation of the hard coat layer is carried out by applying a hard coat agent, and the steps of drying and removing the organic solvent and applying the hard coat agent are carried out in succession.

5. A method for producing a polyester film with a hard coat layer according to any one of claims 1 to 4, wherein the cured resin layer obtained in step (1) comprises a cured product of a resin composition containing one or more resin components selected from the group consisting of polyurethane, acrylic resin, and polyester, and a curing component.

6. A method for producing a polyester film with a hard coat layer according to any one of claims 1 to 5, wherein the hard coat layer obtained in step (4) includes a cured product of urethane (meth)acrylate.

Images