JPH0130622B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a film with improved adhesiveness, which is a polyester film provided with a non-coating layer. Biaxially oriented polyester film, especially biaxially oriented polyethylene terephthalate film, has excellent mechanical strength, friction and wear resistance, dimensional stability, heat resistance, chemical resistance, etc., and is widely used as a base material for magnetic recording materials. There is. The magnetic layer of magnetic recording media is divided into two types: one type in which magnetic metal is dispersed in a resin binder and coated on film, and the other type in which magnetic metal is vapor-deposited on film.
It is used in products such as magnetic disks.
However, the adhesiveness between the magnetic layer and the polyester film is weak, and at present various methods are being used to improve the adhesiveness of the polyester film. Methods for improving the adhesion of polyester films include adding polyethers, specific drying agents, and specific surfactants to the polyester film, physical treatments such as corona treatment, ultraviolet ray treatment, and plasma treatment, and methods for improving the adhesive properties of polyester films. Chemical treatments that treat the film surface with compounds are known. However, these methods suffer from changes in adhesive strength over time, and the adhesive strength itself is not very large, so they are auxiliary means, and the method of providing an undercoat layer on a polyester film is practically used. Various types of undercoat agents have been proposed as undercoat layers for polyester films, and they can be broadly classified into those using organic solvents and those using water. Recently, water-based primers have been in demand from the standpoint of occupational safety and health, pollution control, and resource and energy conservation. Examples of using water-soluble or water-dispersible polyester resins or acrylic resins as undercoating agents include JP-A-54-43017 and JP-B-Sho 49-10243.
No., JP-A-52-19786, JP-A-52-19787, etc. Water-soluble or water-dispersible polyester resins have excellent applicability to polyester films, adhesion to polyester films, adhesion to magnetic layers, and mechanical strength of the resin itself. However, when the film is wound into a roll,
The undercoat layer and the polyester film or the undercoat layer and the undercoat layer tend to block, which poses a practical problem. Water-soluble or water-dispersible polyester resins can be produced by dispersing or dissolving the resin obtained by melt polymerization in hot water, or by dispersing or dissolving a solution of the resin in an organic solvent in water. Methods are being taken to do so. However, since polyester resins are inherently hydrophobic, it is difficult to obtain stable aqueous dispersions or solutions. In order to solve this problem, the amount of copolymerization and the amount of hydrophilic groups in polyester resins have been increased, but this lowers the softening point of the resin and increases hygroscopicity, causing the blocking mentioned above. This makes it easier. As is well known, water-soluble or water-dispersible acrylic resins are relatively easy to manufacture, it is easy to incorporate various functional groups into their structures, and it is also relatively easy to manufacture products that are resistant to blocking. There is a characteristic that However, acrylic resins are often inferior to polyester resins in terms of applicability to polyester films, adhesion to polyester films, mechanical strength, and adhesion to magnetic layers. The present inventors investigated various resins as undercoating agents for improving the adhesion between polyester films and various laminates, especially magnetic layers, and found that water-soluble or water-dispersible polyester resins and acrylic resins The inventors have discovered that when used in combination, the drawbacks of each resin can be overcome, and a polyester film with superior coating properties, adhesive properties, and mechanical strength can be obtained compared to when used alone, leading to the present invention. That is, the present invention is made by applying a water-soluble or water-dispersible polyester resin containing a sulfonic acid group and a water-soluble or water-dispersible acrylic resin to at least one side of a polyester film containing polyethylene terephthalate as a main component. Regarding polyester film. Note that water-soluble or water-dispersible polyester resins and water-soluble or water-dispersible resins are hereinafter simply referred to as polyester resins and acrylic resins. The polyester film constituting the substrate in the present invention is a polyethylene terephthalate film in which 90 mol% or more of its constituent units are ethylene terephthalate. Examples of the polyester resin having a sulfonic acid group in the present invention include Japanese Patent Publication No. 47-40873;
Examples include polyesters known in JP-A-50-83497, JP-A-50-121336, JP-A-52-155640, and polyester resins similar thereto. For example, dicarboxylic acid components of polyester resins include terephthalic acid, isophthalic acid,
Aromatic dicarboxylic acids such as 2,5-naphthalene dicarboxylic acid and their ester-forming derivatives; aliphatic dicarboxylic acids such as adipic acid, azelaic acid, sebacic acid and their ester-forming derivatives; oxybenzoic acid and ester formation thereof; Oxymonocarboxylic acids such as chemical derivatives can be used, but are not limited thereto. The glycol components of the polyester resin include ethylene glycol, 1,4-butanediol, diethylene glycol, triethylene glycol, 1,4-cyclohexanedimethanol, p
-xylene diol, polyethylene glycol,
Aliphatic, alicyclic, aromatic diols such as polypropylene glycol and polytetramethylene glycol can be used, but are not limited thereto. The method for introducing a sulfonic acid group into a polyester resin uses a compound having an ester-forming sulfonic acid group together with the above-mentioned polyester forming component. Examples of compounds having sulfonic acid groups include:
Sulfoisophthalic acid, sulfoterephthalic acid, 4-
There are metal salts such as sulfonaphthalene-2,7-dicarboxylic acid and ester-forming derivatives thereof, and examples of the metal of the metal salt include lithium, sodium, potassium, magnesium, etc., but are not limited to these. It is not something that will be done. A very suitable compound having a sulfonic acid group is 5-sodiosulfoisophthalic acid or 5-sodiosulfodimethylisophthalate. Another method for introducing sulfonic acid groups into polyester resins is to sulfonate the unsaturated groups of polyester containing an ester-forming aliphatic unsaturated compound as a copolymerization component with a sulfonating agent such as sodium bisulfite or sodium metabisulfite. It is also possible to exemplify a method of The amount of aromatic dicarboxylic acid in the dicarboxylic acid component of the polyester resin is preferably in the range of 50 mol% to 100 mol%. This is to increase the softening point or glass transition temperature of the polyester resin and improve blocking properties. The sulfonic acid group in the polyester resin must be present in an amount necessary to make the resin water-soluble or water-dispersible, and when using a dicarboxylic acid having a sulfonic acid group, 2 of the total dicarboxylic acid components must be present. It is preferably used in a range of mol% to 20 mol%. If the amount of sulfonic acid base is less than 2 mol %, the water solubility or water dispersibility will be insufficient, and if the amount of sulfonic acid group is more than 20 mol %, there will be problems such as water resistance of the coating layer and blocking due to moisture absorption. Furthermore, as the polyester resin, not only the saturated linear polyester consisting of the above-mentioned ester-forming component, but also polyester consisting of a compound having an ester-forming component of trivalent or higher valence or polyester having a reactive unsaturated group can be used. can. The acrylic resin in the present invention is preferably one containing alkyl acrylate or alkyl methacrylate as a main component, and this component contains 50 to 50%
It is a water-soluble or water-dispersible resin containing 1 to 50 mol% of a vinyl monomer component copolymerizable with these and having a functional group. Vinyl monomers that can be copolymerized with alkyl acrylates or alkyl methacrylates and have a functional group can be used to impart hydrophilicity to the resin and improve its water dispersibility, or to bind the resin to a polyester film or to the undercoat layer. It is preferable to have a functional group that improves the adhesion with other coating layers or the affinity with the polyester resin blended as a coating agent, and the preferable functional group is a carboxyl group or a salt thereof. , acid anhydride group, sulfonic acid group, or salt thereof, amide group or alkylolated amide group, amino group (including substituted amino group) or alkylolated amino group or salt thereof, hydroxyl group, epoxy These are the basics. Particularly preferred are carboxyl groups or salts thereof, acid anhydride groups, epoxy groups, and the like. Two or more types of these groups may be contained in the resin. It is preferable that the alkyl acrylate or alkyl methacrylate in the acrylic resin be 50 mol% or more because of the coating formability, the strength of the coating film,
This is because blocking resistance is improved. The reason why the alkyl acrylate or alkyl methacrylate content in the acrylic resin is preferably 99 mol% or less is that by introducing a compound having a specific functional group into the acrylic resin as a copolymerization component, it can be made water-soluble or water-dispersible. This is to make it easier to use and to stabilize its state over a long period of time.Furthermore, it improves the adhesion between the coating layer and the polyester film layer, and improves the strength, water resistance, and chemical resistance of the coating layer due to reactions within the coating layer. Furthermore, it is possible to improve the adhesion between the film of the present invention and other materials. Examples of alkyl groups in alkyl acrylates and alkyl methacrylates include methyl group, ethyl group, n-propyl group, isopropyl group, n-
Examples include butyl group, isobutyl group, t-butyl group, 2-ethylhexyl group, lauryl group, stearyl group, and cyclohexyl group. As the vinyl monomer having a functional group copolymerizable with alkyl acrylate or alkyl methacrylate, the following compounds having functional groups such as a reactive functional group, a self-crosslinking functional group, and a hydrophilic group can be used. Examples of compounds having a carboxyl group or a salt thereof, or an acid anhydride group include acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid,
Examples include crotonic acid, metal salts of these carboxylic acids with sodium, ammonium salts, and maleic anhydride. Examples of compounds having a sulfonic acid group or a salt thereof include vinyl sulfonic acid, styrene sulfonic acid,
Examples include metal salts and ammonium salts of these sulfonic acids with sodium and the like. Examples of compounds having an amide group or an alkylolated amide group include acrylamide, methacrylamide, N-methylmethacrylamide,
Examples include methylolated acrylamide, methylolated methacrylamide, ureido vinyl ether, β-ureido isobutyl vinyl ether, and ureido ethyl acrylate. Examples of compounds having an amino group or an alkylolated amino group or a salt thereof include diethylaminoethyl vinyl ether, 2-aminoethyl vinyl ether, 3-aminopropyl vinyl ether, 2-aminobutyl vinyl ether,
Dimethylaminoethyl methacrylate, dimethylaminoethyl vinyl ether, methylolated amino groups thereof, alkyl halides;
Examples include those converted into quaternary chlorides with dimethyl sulfate, sultone, etc. Examples of compounds having a hydroxyl group include β-hydroxyethyl acrylate, β-hydroxyethyl methacrylate, β-hydroxypropyl acrylate, β-hydroxypropyl methacrylate,
Examples include β-hydroxy vinyl ether, 5-hydroxypentyl vinyl ether, 6-hydroxyhexyl vinyl ether, polyethylene glycol monoacrylate, polyethylene glycol monomethacrylate, polypropylene glycol monoacrylate, and polypropylene glycol monomethacrylate. Examples of compounds having an epoxy group include glycidyl acrylate and glycidyl methacrylate. Furthermore, in addition to the above compounds, the following compounds may be used in combination. i.e. acrylonitrile,
Methacrylonitrile, styrenes, butyl vinyl ether, maleic acid mono- or dialkyl esters, fumaric acid mono- or dialkyl esters, itaconic acid mono- or dialkyl esters, methyl vinyl ketone, vinylidene chloride, vinyl acetate, vinyl pyridine, vinyl pyrrolidone, vinyl trimethoxy Examples include, but are not limited to, silane. The acrylic resin may contain a surfactant. However, when the ratio of acrylic resin to polyester resin is high, the low molecular weight surfactant contained in the acrylic resin becomes concentrated during the film forming process and accumulates at the interface between particles. or migrate to the interface of the coating layer, etc.
Problems may arise in the mechanical strength, water resistance, and adhesion of the coating layer to the laminate. In such a case, a so-called soap-free polymerized aqueous dispersion containing no surfactant can be used. The method for producing acrylic resins that do not contain surfactants is described in "Water-soluble Polymers/Water-Dispersible Resins Comprehensive Technical Data Collection" No. 309, edited by Management Development Center Publishing Department, published by Management Development Center Publishing Department, January 1981. It is possible to use the method shown in the text of the lecture entitled ``Prospecting the future from the latest research results - New developments in emulsions and future technical issues'' sponsored by the Industrial Technology Research Group. For example, use of oligomers or polymeric surfactants instead of low molecular weight surfactants, introduction of hydrophilic groups into polymers by using polymerization initiators such as potassium persulfate or ammonium persulfate, and polymers containing hydrophilic groups. copolymerization of monomers,
Manufacturing technology for water-dispersible acrylic resins that do not contain so-called surfactants, such as the use of reactive surfactants and so-called shell-core polymers with different compositions of the inner and outer layers of dispersion particles. It can be used as For water-dispersible resins, the particle size of the water-dispersed particles is
It is 5μ or less, preferably 1μ or less, and more preferably 0.1μ or less. When the particle size is large, it is not only impossible to reduce the thickness of the coating layer, but also there are problems such as easy blocking. In particular, for magnetic recording materials, there is a demand for thinner films, and the thickness of the coating layer must also be thinner, and if the particles are large, the surface becomes rough and magnetic properties such as so-called dropouts deteriorate. There are cases where The ratio of polyester resin to the total amount of polyester resin and acrylic resin is 1% to 99% by weight as solid weight, preferably 1% to 95% by weight, more preferably 5% by weight. to 90% by weight. When the amount of polyester resin is small, there are problems with the adhesion of the aqueous dispersion to the polyester film and the mechanical strength of the coating layer, and when the amount of polyester resin is large, so-called blocking is likely to occur. Although the polyester resin and the acrylic resin can be used separately or in a mixture, it is preferable to use them in advance by mixing them. The method for coating polyester film is described in the "Coating Method" by Yuji Harasaki, published by Maki Shoten in 1979.
A reverse roll coater, a gravure coater, a rod coater, an air doctor coater, or other coating equipment can be used. The timing of coating is before biaxial stretching, after biaxial stretching, or immediately before coating a magnetic layer or the like. Particularly preferably, an aqueous dispersion or aqueous solution is applied to a uniaxially stretched polyester film by a roll stretching method, and the mixture is suitably dried or not dried.
In this method, a uniaxially stretched polyester film is immediately stretched in a direction perpendicular to the previous stretching direction, and then heat treated. According to this method, the coating layer can be dried simultaneously with stretching, and the thickness of the coating layer can be reduced in accordance with the stretching ratio. The thickness of the coating layer on the biaxially stretched polyester film is preferably in the range of 0.01μ to 5μ, more preferably in the range of 0.01μ to 1μ. If the thickness of the coating layer is less than 0.01 μm, it is difficult to apply the coating uniformly, resulting in uneven coating on the product or insufficient adhesion in various applications. Furthermore, if the thickness of the coating layer exceeds 5μ, the film may become difficult to handle due to mutual blocking or stiction, and the stiffness of the film may become low compared to the overall thickness of the film. or Anti-blocking agents, pigments, dyes,
Inorganic fine particles, antioxidants, ultraviolet absorbers, antistatic agents, etc. can be contained. Furthermore, since the coating liquid uses water as a medium, water-soluble resins such as gelatin, polyvinyl alcohol, silicone resins, epoxy resins, and vinyl resins, water-dispersible resins, or methylolated urea may be used as necessary.
A crosslinking agent such as methylolated melamine or alkylolated melamine may also be added to the coating solution. The biaxially stretched laminated polyester film of the present invention has improved adhesiveness and is useful as a base material for packaging materials, photosensitive materials, drafting materials, electrophotographic materials, magnetic recording materials, etc., and is particularly useful for coating materials and metal It is useful as a base material for vapor-deposited magnetic recording materials. The present invention will be explained below with reference to Examples. Note that the evaluation in the examples is based on the method described below. 1. Applicability The applicability when applying a coating agent to a polyester film was evaluated based on the following criteria. 〇: Can be applied uniformly, causing no practical problems. △: Leakage is poor, and some repellency is observed on the coated surface. ×: Poor leakage, repelling coating agent. 2 Transparency Transparency was evaluated based on the following criteria based on haze using an integrating sphere type light transmittance measuring device or by visual inspection. ○: There is no practical problem. △: There are uses that pose a practical problem. ×: Not practically usable. 3 Adhesion (A) The adhesion between the polyester layer and the coating layer of the biaxially stretched laminated polyester film of the present invention was evaluated by the following method. Width 18mm on the coated layer side of the film
A 7 cm length of cellophane tape made by Nichiban Co., Ltd. was applied to prevent air bubbles, and a constant load was applied to the tape using a 3 kg manual load roll. The film was fixed, one end of the cellophane tape was connected to a 500 g weight, and the peel test was performed in a 180° direction after the weight was allowed to fall naturally over a distance of 45 cm. Adhesiveness was evaluated using the following 5-level criteria, and a rating of 4 or higher was considered a pass. Evaluation 5: No peeling at all on the cellophane tape surface. Evaluation 4: Less than 10% peels off from the cellophane tape surface. Practically speaking, if the rating is 4 or higher, it can be used without problems. Evaluation 3: 10 to 50% of the area peels off to the cellophane tape side. Evaluation 2: 50% or more of the part peels off to the cellophane tape side. Evaluation 1: Completely peeled off to the cellophane tape side. Evaluations of 5 to 4 are evaluated as ○, evaluations of 3 as △, and evaluations of 2 to 1 as ×. 4 Adhesion (B) A magnetic layer was coated on the coating layer of the biaxially stretched laminated polyester film of the present invention, and the peel strength was measured.The composition of the magnetic paint forming the magnetic layer was 50 parts of polyurethane and 20 parts of nitrocellulose. , 30 parts of vinyl chloride-vinyl acetate resin, 7.5 parts of isocyanate compound, 12 parts of carbon black, 4 parts of lecithin, γ-
460 parts of Fe ₂ O ₃ was added to methyl ethyl ketone, toluene,
Solvent mixed with equal amounts of methyl isobutyl ketone
It was distributed over 900 copies. To measure peel strength, apply magnetic paint, dry at 80℃ for 1 minute,
Thereafter, a 17.7 mm wide Scotch tape manufactured by Sumitomo 3M Co., Ltd. was applied to the surface of the approximately 5 μm magnetic layer which had been aged at 80° C. for 24 hours, and a T-peel test was performed using a tensile tester. 6 Blocking property (adhesive property) Evaluation of blocking property is based on 2 without coating layer.
The coated layer surfaces of the axially stretched polyester film and the biaxially stretched laminated film of the present invention were stacked at a temperature of 40°C.
Testing was carried out for 20 hours at a humidity of 80%RH and a load of 100g/ ^cm2 .
The evaluation criteria is to visually observe how much of the total area of the film the blocking area is. If there is no blocking at all, it is ○, if there is partial blocking, it is △, 50
If more than % of the part is blocking, ×
And so. Reference example 1 Production example of polyester resin Dimethyl terephthalate, dimethyl isophthalate, 5-sodiosulfodimethyl isophthalate, ethylene glycol, diethylene glycol, triethylene glycol and calcium acetate as a transesterification catalyst were mixed, and the mixture was heated at 200 to 230°C. The transesterification reaction is carried out until a quantity of methanol is distilled off. After the transesterification reaction was completed, orthophosphoric acid was added, and then antimony trioxide was added as a polymerization catalyst, and the pressure was gradually reduced and the temperature was increased to finally carry out polymerization at 280° C. under a degree of vacuum of 1 mmHg or less. The obtained polyester resin contains 50 mol% of the terephthalic acid component, 43 mol% of the isophthalic acid component, and 7 mol% of the 5-sodiosulfoisophthalic acid component in the dicarboxylic acid, and ethylene glycol in the glycol,
The ratio of diethylene glycol to triethylene glycol is approximately 2:1:1. An aqueous dispersion of polyester resin is prepared by adding the above polyester resin to hot water and stirring to obtain a concentration of 30% by weight and a dispersed particle size of 0.1.
~0.01μ was obtained. Reference Example 2 Production Example of Polyester Resin In the same manner as in Reference Example 1, the terephthalic acid component in the dicarboxylic acid was 50 mol%, the isophthalic acid component was 40 mol%,
10 mol% of 5-sodiosulfoisophthalic acid,
obtaining a polyester resin in which the ratio of the ethylene glycol component and diethylene glycol component in the short chain glycol is about 2:1, the long chain glycol is polyethylene glycol with a molecular weight of 4000, and this polyethylene glycol is 18% by weight in the resin, This was poured into hot water and stirred to obtain a solution having a concentration of 30% by weight and a dispersed particle size of 0.1 to 0.01μ. Reference example 3 Production example of acrylic resin 51 parts of ethyl acrylate, 40 parts of methyl methacrylate
parts, 9 parts of methacrylic acid, dodecyl mercaptan
0.5 parts sodium lauryl sulfate dissolved in 1 part water
0.25 part was homomixed in a blender to obtain a monomer premix emulsion. This premix emulsion and 0.8 parts of ammonium persulfate dissolved in 1.5 parts of water were separately added to water at a temperature of 75°C.
The reaction was carried out by dropping the mixture into 187 parts over a period of 3 hours, during which time the reaction temperature was maintained at 75-80°C. After the dropwise addition was completed, the temperature was maintained at 80°C for an additional 3 minutes to complete the reaction and obtain a latex. Next, while maintaining this latex at 80℃, add 0.9 parts of magnesium oxide and water.
Pour in a magnesium oxide dispersion consisting of 26 parts,
Stir for 15 minutes at the same temperature, then add 28% ammonia water to adjust the pH of the reaction solution to 7.5, and continue to mature for 30 minutes.
A 0.1-0.01μ aqueous dispersion was obtained. Reference example 4 Production example of acrylic resin 55 parts of ethyl acrylate, 35 parts of isobutyl methacrylate, 10 parts of methacrylic acid, benzoyl peroxide
0.5 parts in 150 parts of isopropyl alcohol under nitrogen
Polymerization was carried out at 80°C for 7 hours, and then 85 parts of isopropyl alcohol was distilled off. Approximately 4 parts of 28% ammonia water and 200 parts of water were added to this, and after thorough mixing, the isopropyl alcohol remaining in the system was removed. Distilled away. Add water to the above aqueous dispersion to determine the solid content.
150 copies and 800 copies for water. This aqueous dispersion was heated to 70°C under nitrogen, and 108 parts of styrene, 270 parts of isobutyl acrylate, and 144 parts of methyl methacrylate were added.
parts, a mixture of 18 parts of glycidyl methacrylate;
27 parts of a 3.6% ammonium persulfate aqueous solution was added separately over a period of 3 hours to polymerize, and after further stirring at 70°C for 2 hours, further 27 parts of 3.6% ammonium persulfate was added and stirred for about 3 hours. The particle size of the obtained aqueous dispersion was 0.1 μm or less. Comparative Examples 1 to 6 The water-dispersible polyester resins and acrylic resins of Reference Examples 1 to 4 were separately mixed at a concentration of 5% by weight or
15μ thick with #3 bar coater at 10% by weight
It was applied to a biaxially stretched polyethylene terephthalate film. coating properties, transparency, blocking properties,
Adhesion between polyester film and coating layer (A), Adhesion between coated polyester film and magnetic layer
(B) is shown in Table 1. It can be seen that the polyester resins of Reference Examples 1 and 2 have problems with blocking properties.
It can be seen that the acrylic resin of Reference Example 3 has a problem in adhesiveness with the magnetic layer. It can be seen that the acrylic resin of Reference Example 4 has a problem in adhesiveness with the coatable polyester film. Examples 1 to 4 A coating agent with a concentration of 5% by weight, which is a mixture of the water-dispersible polyester resin of Reference Example 1 or 2 and the water-dispersible acrylic resin of Reference Example 3 or 4, was applied to a #3 bar coater. It was applied to a biaxially stretched polyethylene terephthalate film with a thickness of 15 μm. As shown in Table 1, the evaluation results show that the problems of each of the resins of Reference Examples 1 to 4 are solved and that the resins are useful as magnetic recording materials. Example 5 Polyethylene terephthalate with an intrinsic viscosity of 0.66
It was melt extruded at 285°C and cast onto a cooling drum at 60°C to obtain an amorphous film with a thickness of about 200μ.
This film was stretched 3.5 times in the machine direction at 95°C.
A coating agent having the same formulation as in Example 2 and having a concentration of 3% by weight was applied to one side of this longitudinally stretched film. This film was stretched 3.7 times in the transverse direction at 110°C and heat-set under tension at 220°C. 2 obtained in this way
The axially stretched polyester film had a polyethylene terephthalate film layer of about 15μ and a coating layer of about 0.05μ. The uniformity and appearance of the coating layer of this film,
The transparency and adhesion (A) were good, and the blocking property was also very good. The coefficient of friction is compared to the uncoated film for both the static friction coefficient and the kinetic friction coefficient.
It was a good value, if not better. The adhesion of this film to the magnetic layer was 107 g, there were no problems in workability in the magnetic tape manufacturing process, there were no problems in magnetic properties such as dropout, and it was suitable for practical use. 【table】

Claims (1)

[Claims] 1. A polyester film containing polyethylene terephthalate as a main component, coated on at least one side with a water-soluble or water-dispersible polyester resin containing a sulfonic acid group and a water-soluble or water-dispersible acrylic resin. Polyester film. 2 The polyester resin is a linear resin mainly composed of a dicarboxylic acid component and a glycol component, in which the aromatic dicarboxylic acid component accounts for 50 to 100 mol%, and the dicarboxylic acid component having a sulfonic acid group accounts for 2 to 100 mol%. The polyester film according to claim 1, characterized in that the content is 20 mol%. 3 The acrylic resin has an alkyl acrylate and/or alkyl methacrylate component of 50 to 50%.
Claim 1, characterized in that it is a water-soluble or water-dispersible resin containing 1 to 50 mol% of a vinyl monomer component copolymerizable with these and having a functional group. Polyester film as described in section.