JPH07287836A - White polyester film for magnetic card - Google Patents

Abstract

PURPOSE:To ensure superior adhesive property to UV ink and a magnetic coating material by forming a coating layer of a resin having a specified wt.% of phosphoric acid groups or phosphate groups in a process for producing a white polyester film. CONSTITUTION:A white polyester film based on polyester and a white pigment such as titanium oxide, contg. a stabilizer, etc., and having >=20mum thickness is formed through a process for producing a biaxially stretched film. In this process, a coating layer having 0.02-0.5mum thickness is formed on one side of the white polyester film by applying and drying a coating soln. contg. >=50wt.% resin having phosphoric acid groups or phosphate groups. The coating soln. is applied to the film after the film is stretched in a uniaxial direction and then the film is further stretched in a uniaxial direction. The coating layer adheres to the white polyester film with adhesion fit for practical use and superior adhesive property to UV ink and a magnetic coating layer is ensured.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a white polyester film for a magnetic card, and more particularly to a magnetic card having excellent antistatic properties as well as excellent adhesion to magnetic paints and printing inks. It relates to a white polyester film.

[0002]

BACKGROUND OF THE INVENTION Aromatic polyester white films mixed with white pigments such as titanium oxide are widely used in magnetic recording materials, printing materials and the like. It has a problem of poor adhesion of printing ink. In particular, a thick white polyester film is used for a magnetic card such as a telephone card and a prepaid card, but it has drawbacks in adhesive strength to a magnetic paint or UV ink, electrostatic property and the like. For example, since UV ink has a large stress strain during curing, the ink layer is liable to drop due to interface destruction with the polyester film. In addition, the sticking due to the electrification of the film significantly lowers the workability and causes a problem such as an ignition accident due to spark discharge.

Conventionally, a method of forming a primer layer of an easily-adhesive resin such as an acrylic resin, a urethane resin or a polyester resin has been proposed as a method of imparting an easily-adhesive property to the surface of a polyester film. Further, as a method of imparting antistatic properties, a method of kneading a low molecular weight anionic surfactant type compound such as an organic sulfonate, a method of depositing a metal compound, an anionic compound or a cationic compound, or so-called A method of applying conductive particles on the surface is known. The method of kneading an anionic compound has an advantage that it can be manufactured at low cost, but has a limit in the antistatic effect. Furthermore, since a low molecular weight compound is used, the water resistance is poor, and the deterioration of the adhesiveness over time due to blooming and the deterioration of the antistatic performance due to the transfer of the compound are likely to occur, resulting in a problem of durability.

The method of vapor-depositing a metal compound has excellent antistatic properties, and although its application as a transparent conductive film has been expanding in recent years, it is high in manufacturing cost and suitable for a specific application. It is difficult to use as a prevention film. The method of applying the conductive compound is a simple method since it can be applied simultaneously with the easily adhesive resin in the form of a mixture. Further, as a method for producing a biaxially stretched polyester film having a coating layer, there is a method called a coating stretching method (in-line coating method) in which a coating solution is applied to a sheet or film, and then the film is stretched and heat-treated. The use of is advantageous in that a wide product can be obtained at low cost because film formation and coating are performed at the same time. However, in order to obtain a coating layer that simultaneously satisfies easy adhesion, antistatic properties, etc., there are considerable difficulties in the formulation. For example, the method using conductive particles such as conductive carbon has the advantage that the antistatic effect is relatively good and can be manufactured at a relatively low cost, but it has the drawback of deteriorating the whiteness and glossiness of the white film surface. is there. Similar to the kneading method, the method using a low molecular weight anion compound or cation compound has the problems of deterioration in adhesiveness over time due to water resistance and blooming and deterioration of blocking.

As a high molecular weight anionic antistatic agent, a film coated with a high molecular weight antistatic agent such as polystyrene sulfonate sodium salt is known, but the polystyrene sulfonate sodium salt is used when applied to a coating stretching method. In many cases, the coating layer becomes discontinuous and the antistatic effect is not sufficiently exhibited in many cases. Further, since the coating layer has numerous cracks, the color tone of the film varies, which is not suitable for a white polyester film.
Further, since the high molecular weight anionic antistatic agent has a low static prevention ability, there is little room for blending a binder that easily adheres to the UV ink, and a coating layer having both static prevention and easy adhesion can be obtained by a single coating. Is difficult. Further, high molecular weight cationic antistatic agents are superior in static prevention ability as compared with anionic antistatic agents, but are inferior in thermal stability. Therefore, when coating stretching is carried out under normal conditions, stretching and heat treatment steps are carried out. In some cases, the expected antistatic effect may not be exhibited due to volatilization or thermal decomposition. Further, when the film scraps coated with the cationic antistatic agent are reused, the coloring due to the thermal decomposition of the cationic antistatic agent during the melting of the film is remarkable, and the value of the white film in which the color tone is important is significantly impaired.

[0006]

DISCLOSURE OF THE INVENTION The inventors of the present invention have made extensive studies in view of the above problems, and as a result, by adopting a specific constitution, excellent adhesiveness and water resistance particularly to UV ink and magnetic paint layers are obtained. It has been found that it has a certain excellent antistatic property, and in addition, the waste film can be reused to be an economically excellent white polyester film for magnetic cards,
The present invention has been completed.

That is, the gist of the present invention is to coat a polyester film containing a white pigment and having a thickness of 20 μm or more with a thickness of 0.02 to 0.5 μm on at least one surface of the polyester film in the manufacturing process. A white polyester film for a magnetic card, which has a layer and the coating layer contains 50% by weight or more of a resin having a phosphate group or a phosphate group.

The present invention will be described in more detail below. In the present invention, as the polyester constituting the base white polyester film, typically, for example, polyethylene terephthalate in which 80 mol% or more of the constituent unit is ethylene terephthalate, and 80 of the constituent unit
Polyethylene-2,6-naphthalate in which mol% or more is ethylene-2,6-naphthalate, poly-1,4-cyclohexanedimethylene terephthalate in which 80 mol% or more of structural units is 1,4-cyclohexanedimethylene terephthalate, etc. Other examples include polyethylene isophthalate and polybutylene terephthalate.

Examples of the copolymerization component other than the above-mentioned superior constituent components include diol components such as diethylene glycol, propylene glycol, neopentyl glycol, polyethylene glycol and polytetramethylene glycol, isophthalic acid, 2,7-naphthalenedicarboxylic acid,
Ester-forming derivatives such as 5-sodium sulfoisophthalic acid, adipic acid, azelaic acid, sebacic acid and oxymonocarboxylic acids can be used. Also,
As the polyester, in addition to a homopolymer or a copolymer, a blend with a small proportion of another resin can be used.

The polyester constituting the film of the present invention contains a white pigment, and as the white pigment,
Examples thereof include titanium oxide and barium sulfate, which contain at least one of these pigments. The content of the white pigment is usually in the range of 5 to 20% by weight. Further, in the film of the present invention, in addition to white pigments, inorganic fillers such as silicon oxide, aluminum oxide, magnesium oxide, calcium carbonate, kaolin, talc, polystyrene resin, acrylic resin, urea resin, melamine resin, etc. Such as an organic filler, a resin incompatible with polyester, for example, a void forming agent such as polypropylene, a stabilizer, a lubricant, a cross-linking agent, an antiblocking agent, an antioxidant, an ultraviolet absorber,
A light ray blocking agent, a coloring agent and the like can be contained as necessary.

The polyester film of the present invention may have a multi-layer structure, in which case some of the layers may be formed of a polymer other than polyester. In the present invention, the white polyester film is preferably a biaxially stretched film, and the thickness thereof is 20 μm or more, preferably 50 to 500 μm, particularly preferably 75 to 30.
It is 0 μm. If the thickness is less than 20 μm, the film is unsatisfactory and unsuitable, while if it exceeds 500 μm, the film-forming property tends to be poor.

As the coating liquid for obtaining the coating layer of the present invention, it is preferable to use a liquid containing water as a main medium from the viewpoint of safety and hygiene. The coating layer of the film of the present invention contains 50% by weight or more, preferably 65% by weight or more, of a resin having a phosphate group or a phosphate group. When the content is less than 50% by weight, sufficient antistatic property is not exhibited. Further, the phosphorus element content in the coating layer of the film of the present invention is preferably 1 to 15% by weight, and the phosphorus element is based on the above-mentioned resin having a phosphate group or a phosphate group. Is preferred. If the amount of elemental phosphorus is less than 1% by weight, the ability as an antistatic agent tends to be insufficient, and if it exceeds 15% by weight, water dispersibility, filterability, film-forming property, antistatic property and the like are deteriorated. I might get up. In the present invention, examples of the resin having a phosphate group or a phosphate group (hereinafter, abbreviated as a phosphorus-containing resin) used include, for example, an acrylic or vinyl-based monomer (a) having a phosphate group or a phosphate group. Or a copolymer comprising (a) as an essential component, having at least one unsaturated group and copolymerizable with (a), and / or a polymer (c) copolymerizable therewith. Examples thereof include polymers.

The monomer (a) is preferably acryloyloxyalkyl phosphate (for example, acryloyloxyethyl phosphate, acryloyloxypropyl phosphate, 1-acryloyloxypropyl-2-phosphate, 4-acryloyloxybutyl phosphate, acryloyloxyethoxy). Ethyl phosphate, 1-acryloyloxy-3-chloropropyl-2-phosphate, etc.), methacryloyloxyalkyl phosphate (for example, methacryloyloxyethyl phosphate, methacryloyloxypropyl phosphate, 1-methacryloyloxy-2-phosphate, 4-methacryloyloxybutyl). Phosphate,
2-methacryloyloxyethoxyethyl phosphate, 1-methacryloyloxy-3-chloropropyl-
2-phosphate, etc.), acrylamidoalkyl phosphate (eg, 2-acrylamidoethyl phosphate, etc.), methacrylamide amidophosphate (eg, 2-methacrylamidoethyl phosphate, etc.), vinylbenzyl phosphate, etc., but are not limited thereto. is not.

These monomers (a) may be used alone or in combination of two or more if necessary. Further, the counter ion forming a salt with these is not particularly limited, but preferably an alkali metal ion (eg, lithium ion, sodium ion, potassium ion, etc.),
Ammonium ions and the like can be mentioned. Of these, potassium ions are particularly preferable. Monomer (b)
Is not particularly limited as long as it can be copolymerized with (a), but acrylic acid esters, methacrylic acid esters, acrylamides, methacrylamides, allyl compounds, vinyl ethers, vinyl esters are preferred. , Vinyl heterocyclic compounds, styrenes, maleic acid esters, fumaric acid esters, itaconic acid esters,
Examples thereof include olefins, crotonic acid esters and unsaturated nitriles. These copolymerizable monomers may be used alone or in combination of two or more. Particularly preferred among these are acrylic acid esters, methacrylic acid esters, vinyl ethers and styrenes.

The polymer (c) is not particularly limited as long as it is a copolymer of (a) or (a) + (b) with a graft or block, and examples thereof include polyesters, polyurethanes and epoxies. Examples thereof include resins, acrylic resins, vinyl resins, silicone resins and the like.
Of these, polyesters and polyurethanes are particularly preferable. The phosphoric acid group of the monomer (a) used in the present invention is likely to polymerize with an adjacent or free phosphoric acid component during polymerization to easily form polyphosphoric acid in a side chain portion. Since the formation of polyphosphoric acid causes a decrease in water dispersibility, filterability, film-forming property, antistatic property, etc., the phosphoric acid group in the phosphorus-containing resin used in the present invention is a specific monovalent cation. When neutralized, the molar ratio of phosphorus to neutralizing ions (ion / phosphorus) is
It is preferably 1.5 or more.

The coating liquid for obtaining the coating layer of the present invention may contain at least one water-based resin which serves as a binder at the same time as the phosphorus-containing resin. The aqueous resin is not particularly limited, and examples thereof include polyesters, polyurethanes, epoxy resins, acrylic resins, vinyl resins and the like, and modified resins thereof. Of these, polyester resins and polyurethane resins are particularly preferable. These water-based resins may be those forcibly dispersed with a surfactant or the like, but preferably have a nonionic hydrophilic component such as polyethers or a hydroxyl group, and more preferably have an anionic hydrophilic group. It is preferable to use a water-soluble or water-dispersible resin coating agent such as a self-dispersion type.

The anionic group contained in the water-based resin serving as a binder is bound to the resin by copolymerization or the like, and its components are sulfonic acid, carboxylic acid, phosphoric acid and their lithium salts, sodium salts, potassium salts. , Ammonium salt and the like. The ratio of the anionic group to the resin solid content is preferably 0.05 to 8% by weight. When the amount of the anionic group is less than 0.05% by weight, the water solubility or water dispersibility of the resin tends to be poor, and when the amount of the anionic group exceeds 8% by weight, the water resistance of the coating layer is poor and the moisture absorption is low. Then, the films may stick to each other (blocking). Further, the coating liquid for obtaining the coating layer of the present invention may contain particles for improving the slipperiness of the coating layer. As the particles, inorganic particles such as colloidal silica, alumina, calcium carbonate, titanium oxide, etc. and fine particles containing a homopolymer or copolymer of polystyrene resin, polyacrylic resin or polyvinyl resin, or a composite of these and a crosslinking component Organic particles represented by crosslinked particles are exemplified.

Further, the coating liquid for obtaining the coating layer of the present invention contains a crosslinking agent in order to improve the adhesion (blocking resistance) of the coating layer, water resistance, solvent resistance and mechanical strength. May be. As the cross-linking agent, methylolated or alkylolated urea-based compounds, melamine-based compounds, guanamine-based compounds, acrylamide-based compounds, polyamide-based compounds, epoxy compounds, oxazoline compounds, aziridine compounds, blocked isocyanate compounds, silane coupling agents, titanium couplings. Agents, zirco-aluminate coupling agents, peroxides, heat- or photo-reactive vinyl compounds, photosensitive resins and the like. Further, the coating liquid for obtaining the coating layer of the present invention contains, if necessary, an antifoaming agent, a coating property improving agent, a thickener, a low molecular weight antistatic agent, an organic lubricant, an antioxidant, an ultraviolet absorber. , A foaming agent, a dye, a pigment, etc. may be contained.

When the coating liquid for obtaining the coating layer of the present invention contains water as the main medium, it may contain a small amount of an organic solvent for the purpose of improving the dispersion in water or the film forming performance. Good. When the organic solvent is used as a main medium mixed with water, it is necessary to use it in a range that dissolves in water. Examples of the organic solvent include aliphatic or alicyclic alcohols such as n-butyl alcohol, n-propyl alcohol, isopropyl alcohol, ethyl alcohol and methyl alcohol, glycols such as propylene glycol, ethylene glycol and diethylene glycol, n-butyl cellosolve, Ethyl cellosolve, methyl cellosolve, glycol derivatives such as propylene glycol monomethyl ether, ethers such as dioxane and tetrahydrofuran, esters such as ethyl acetate and amyl acetate, ketones such as methyl ethyl ketone and acetone, N
Examples include, but are not limited to, amides such as methylpyrrolidone. These organic solvents may be used alone or in combination of two or more if necessary.

The coating layer of the present invention has a final dry thickness in the range of 0.02 to 0.5 μm, preferably
0.03 to 0.3 μm, more preferably 0.0
It is in the range of 5 to 0.2 μm. Coating layer thickness is 0.5μ
If it is larger than m, the films are likely to be blocked with each other, and particularly when the coated film is re-stretched for the purpose of increasing the strength of the film, it tends to stick to the roll during the process, which is not preferable. The problem of blocking is particularly remarkable when the same antistatic layer is provided on both surfaces of the film. Coating layer thickness is 0.02
If it is less than μm, the effect of the present invention cannot be exhibited. A reverse roll coater, a gravure coater, a rod coater, an air doctor coater, etc. shown in "Coating Method" by Yuji Harazaki, published by Maki Shoten, 1979, can be used as a method for applying the above-mentioned coating liquid to a polyester film. .

In the present invention, a coating layer is provided in the production process of the polyester film by using the coating apparatus and the like exemplified above, but the coating film to be coated is stretched in at least uniaxial direction after coating, preferably. Usually, it is stretched in at least uniaxial direction before coating, and further stretched in at least uniaxial direction after coating. When the stretching treatment after coating is not carried out, the adhesion between the formed coating layer and the white polyester film which is the base film is weak, and there is a tendency that the adhesiveness suitable for practical use cannot be obtained. In order to achieve these industrially advantageously, it is preferable to apply them in the biaxially stretched film production process. As an example of such a method, a method of applying a film to a film uniaxially stretched in the longitudinal direction of the film forming step, stretching the film in a dry or undried state in a direction perpendicular to the uniaxial stretching direction, and then subjecting it to heat treatment is manufactured. It is adopted from the viewpoint of cost, but is not limited to these. The stretching step for obtaining the above-mentioned film is
It is preferably carried out at 120 to 180 ° C., and the stretching ratio is usually at least 4 times or more, preferably 6 to 2 in terms of area ratio.
It is 0 times. The stretched film is usually 150-250
Heat treated at ℃.

Further, a method of relaxing 0.1 to 20% in the longitudinal direction and the transverse direction in the maximum temperature zone of the heat treatment and / or the cooling zone at the heat treatment outlet is preferably adopted. In particular, the coating solution is applied to a uniaxially stretched white polyester film stretched 2 to 6 times in the longitudinal direction of the film by a roll stretching method at 120 to 180 ° C., and the coating solution is appropriately dried or not dried, and then the uniaxially stretched film. The film is stretched 2 to 6 times in the transverse direction at 120 to 180 ° C.
A method of performing heat treatment at 0 to 250 ° C. for 1 to 600 seconds is preferably adopted. According to this method, the coating layer can be dried at the same time as stretching, and the thickness of the coating layer can be thinned according to the stretching ratio, so that a film suitable as a white polyester film substrate can be prepared at a relatively low cost. Can be manufactured. The coating layer of the film of the present invention may be provided on only one side of the white polyester film or on both sides. When provided only on one surface, a coating layer other than the present invention may be formed on the opposite surface, if necessary, to impart other characteristics to the white polyester film of the present invention. In addition, in order to improve the coating property and the adhesive property of the coating agent on the film, the film may be subjected to a chemical treatment or a discharge treatment before the coating. Further, in order to improve the surface characteristics and the like of the coating layer of the biaxially stretched polyester film of the present invention, the coating layer may be subjected to a discharge treatment after the coating layer is formed.

[0023]

EXAMPLES The present invention will be described in more detail with reference to examples below, but the present invention is not limited to the following examples as long as the gist thereof is not exceeded. The measuring methods and definitions of various physical properties and characteristics in the present invention are as follows. In the examples and comparative examples, "parts" and "%" mean "parts by weight" and "% by weight", respectively. (1) Surface resistivity (antistatic property) Concentric circular electrode from Yokogawa / Hewlett-Packard "1
A sample was placed on the "6008A (trade name)" (inner electrode 50 mm diameter, outer electrode 70 mm diameter) in an atmosphere of 23 ° C and 50% RH, and a voltage of 100 V was applied. ) ”Was used to measure the surface resistivity of the sample. The criteria for judgment were as follows based on the logarithm of the surface resistivity. Less than 10: A (good) 10 or more, less than 13: B (normal) 13 or more: C (defective)

(2) Water resistance of antistatic property After immersing the sample film in warm water of 50 ° C. for 1 minute, the adhered water content is qualitative filter paper N made by TOYO Advantech.
o. The sample was lightly sandwiched between 2 and removed, and the sample was dried at room temperature for a whole day and night, and then the surface resistivity was measured and evaluated by the difference from the value before the treatment. This evaluation is a measure of the blooming property and durability of the antistatic agent. The judgment criteria are as follows. Less than 0.5: ○ (good) 0.5 or more and less than 1: △ (normal) 1 or more: × (bad)

(3) Adhesiveness with UV curable ink UV curable offset ink "FD" manufactured by Toyo Ink Mfg. Co., Ltd.
"OL indigo APN ro" was transferred to a film with a thickness of 2 µm by "RI tester RI-2", which is an offset printing tester manufactured by Akira Seisakusho, and this was irradiated by Ushio Electric Co., Ltd. "UVC-402". / 1HN: 302/1
Through MH ", the ink was cured under the conditions of a mercury lamp output of 120 W / cm, a line speed of 10 m / min, and a lamp-film interval of 100 mm, and a cellotape peeling test was immediately performed to evaluate the peeled area. The judgment criteria are as follows. No peeling: ○ (good) Some peeling spots: △ (normal) Full peeling: × (poor)

(4) Adhesiveness to magnetic paint The following evaluation paint was applied to a sample film with a wire bar so that the film thickness after drying was 5 μm, dried at 80 ° C. for 2 minutes, and then at 60 ° C. A sample was prepared by aging for 24 hours. Evaluation paint Magnetic fine powder X6000 (Titanium industry) 500 parts, polyurethane resin Nipporan 2304 (manufactured by Nippon Polyurethane)
30 parts, vinyl chloride vinyl acetate copolymer 1000GKT (manufactured by Denki Kagaku)
50 parts, lecithin (kishida chemical reagent) 5 parts, cyclohexanone 246 parts, methyl isobutyl ketone 246 parts and methyl ethyl ketone 738 parts were mixed and dispersed in a sand mill for 1 hour, and then 10 parts of a cross-linking agent, Coronate L, was added and well stirred.

The adhesive strength of the magnetic layer was fixed to a surface of the magnetic layer of the sample with a cellophane tape (18 mm width) manufactured by Nichiban Co., Ltd. in a length of 7 cm so as to prevent air bubbles from entering, and a constant load of 3 Kg was applied on the tape. After applying a load and adhering, fix the film and connect one end of the cellophane tape to the weight of 500 g,
The weight was evaluated by a method in which peeling in the 180 ° direction started after the weight naturally dropped at a distance of 45 cm. Adhesiveness was evaluated according to the following three-stage criteria. The paint does not peel at all: ○ The paint of less than 10% peels off: △ The paint of 10% or more peels off: ×

(5) Melt Coloring Property About 10 g of a sample was placed in a glass test tube having an internal volume of 50 ml, dried under high vacuum at 160 ° C. for 2 hours, and then recompressed to 100 mmHg with nitrogen gas to melt the glass test tube. After sealing,
Heat treatment was performed at 290 ° C. for 2 hours, and the sample was taken out into an aluminum pan having a diameter of 30 mm and formed into a disk shape to prepare a measurement sample. The sample was measured using a color analyzer TC-1800MK2 manufactured by Tokyo Denshoku Co., Ltd. according to JIS Z
The b value was measured according to the method of -8722. This value indicates the degree of yellowish color, and the lower the value, the more preferable.

The resins used in the following Examples and Comparative Examples are as follows. High molecular weight antistatic agent A Acrylic resin consisting of methacryloyloxyethyl phosphate potassium salt, ethyl acrylate and methyl acrylate (potassium / phosphorus ratio = 1.6 phosphorus element content 7
%). High molecular weight antistatic agent B Aqueous solution consisting of sodium polystyrene sulfonate Antistatic agent C Diphenyl ether disulfonic acid polyester resin Polyester consisting of terephthalic acid, isophthalic acid, 5-sodium sulfoisophthalic acid, ethylene glycol, diethylene glycol, 1,4-butanediol Resin Polyurethane resin Isophorone diisocyanate as the isocyanate component, polyester polyol composed of terephthalic acid, isophthalic acid, ethylene glycol, diethylene glycol as the polyol component, chain extender 2,
Polyurethane resin consisting of 2-dimethylolpropionic acid

Comparative Example 1 90% polyethylene terephthalate having an intrinsic viscosity of 0.72
And a composition of 10% titanium oxide, 280-300
It was melt extruded at a temperature of ° C and cast on a cooling drum while also using the electrostatic adhesion method to obtain an unstretched film. This film was stretched 3.3 times in the longitudinal direction at 95 ° C., further stretched 3.8 times in the transverse direction at 110 ° C., and heat-treated at 230 ° C. to obtain a 188 μm-thick biaxially stretched white polyester film. . The obtained film b value was 9.0.

Example 1 In Comparative Example 1, a coating liquid of an aqueous dispersion containing 8% of a high molecular weight antistatic agent A was applied to one side of the film after longitudinal stretching and before transverse stretching, and the coating amount was 4.7 g / m. ^A biaxially stretched white polyester film having a coating layer of 0.1 μm was obtained in exactly the same manner as in Comparative Example 1 except that coating was performed with ² (wet). The b value of the obtained film was 10.4. This value means that the film is well tolerated for recycling. Example 2 A biaxially stretched white polyester film was obtained in the same manner as in Example 1 except that the thickness of the coating layer was changed to 0.05 μm.

Example 3 Biaxially prepared in the same manner as in Example 1 except that an aqueous dispersion containing 70 parts of high molecular weight antistatic agent A and 30 parts of polyester coating agent was used as the coating liquid. A stretched white polyester film was obtained. Example 4 Biaxially stretched white polyester was prepared in the same manner as in Example 1 except that an aqueous dispersion containing 50 parts of a high molecular weight antistatic agent A and 50 parts of a polyester coating agent was used as the coating liquid. I got a film. Example 5 A biaxially stretched white polyester film was obtained in the same manner as in Example 3 except that the polyurethane coating agent was used instead of the polyester coating agent.

Comparative Example 2 A biaxially stretched white polyester film was obtained in the same manner as in Example 1 except that the coating liquid was changed to a polyester coating agent. Comparative Example 3 A biaxially stretched white polyester film was obtained in the same manner as in Example 1 except that the polyurethane coating agent was used as the coating liquid. Comparative Example 4 Biaxially stretched white polyester was prepared in the same manner as in Example 1 except that an aqueous dispersion containing 30 parts of high molecular weight antistatic agent A and 70 parts of polyester coating agent was used as the coating liquid. I got a film.

Comparative Example 5 A biaxially stretched white polyester film was obtained in the same manner as in Example 1 except that the thickness of the coating layer was changed to 0.01 μm. Comparative Example 6 A biaxially stretched white polyester film was obtained in the same manner as in Example 4 except that the polymer antistatic agent A was changed to the polymer antistatic agent B in Example 4. Comparative Example 7 A biaxially stretched white polyester film was obtained in the same manner as in Example 4, except that the polymer antistatic agent A was changed to the polymer antistatic agent C in Example 4. The results obtained above are summarized in Tables 1 and 2 below.

[0035]

[Table 1]

[0036]

[Table 2] In Tables 1 and 2 above, PES means polyester and PU means polyurethane.

[0037]

The white polyester film for magnetic cards of the present invention has excellent antistatic properties such as UV ink adhesiveness, magnetic paint layer adhesiveness and water resistance required for magnetic cards, and can be reused. It is economically superior and its industrial value is high.

Claims (1)

[Claims] 1. A thickness of 0.02 provided on at least one surface of a polyester film containing a white pigment and having a thickness of 20 μm or more, in the manufacturing process of the polyester film.
A white polyester film for a magnetic card, which has a coating layer of ˜0.5 μm, and the coating layer contains 50% by weight or more of a resin having a phosphate group or a phosphate group.