JP2674050B2 - Magnetic recording card - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a magnetic recording card using a polyester film as a base material, specifically, a cash card, various credit cards, a magnetic ticket, a telephone card, and a POS.
Card, hospital medical care card, microwave cooking card, ID
It concerns cards and the like.

[Prior Art] Conventionally, as a magnetic recording card, a laminate having (1) a magnetic recording layer, a white polyester film layer, and a printing layer optionally provided in this order is (2) a magnetic recording layer. In order to impart durability to the printing layer and the printing layer, a laminate further provided with an easy-adhesion layer such as urethane and acrylic between the polyester film and each layer, or (3) to improve the yield due to the adhesion of dust during processing. A polyester film or an easy-adhesion layer to which various surfactants and antistatic agents are added to impart antistatic properties is used.

[Problems to be Solved by the Invention] However, the magnetic recording card described above has the following problems. That is, in the case of (1), there is a drawback that the adhesiveness between the layers is not sufficient and durability is remarkably lacked.
Further, in the case of (2), the adhesiveness is considerably improved, so that the durability is considerably improved, but there is a drawback that foreign matter such as dust is easily attracted in the processing step and the product yield is poor, and in the case of (3), foreign matter such as dust is bad. The product yield is improved because it is hardly attracted in the processing step, but the adhesiveness is greatly reduced,
There is a drawback that durability deteriorates.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above problems and provide a magnetic recording card having excellent durability and product yield.

[Means for Solving the Problems] The present invention provides a compound represented by the general formula (However, R is hydrogen or methyl group, M is hydrogen, alkali metal, alkaline earth or ammonium, R ₁ , R ₂ , R ₃ and R ₄ are hydrogen, halogen, alkyl group or alkoxy group, respectively.) 5% by weight of a polymer having a repeating unit of
On the polyester layer B having an optical density of 0.5 or more, a whiteness of 80% or more, and a sulfonic acid or sulfonate concentration of 0.002% or more at the surface layer 10 nm, which has at least one layer A containing at least 95% by weight Alternatively, the present invention relates to a magnetic recording card in which a magnetic recording layer is provided via a layer A.

The polyester layer B in the present invention comprises ethylene terephthalate, ethylene α, β-bis (2-chlorophenoxy) ethane-4,4′-dicarboxylate, ethylene α, β-bis (phenoxy) ethane-4,4′-. The main constituent is at least one structural unit selected from dicarboxylate and ethylene 2,6-naphthalate units.

In addition, other components other than those described above may be copolymerized within a range not to impair the present invention, preferably within 10 mol%.

The polyester layer B in the present invention contains the above composition as a main component, but may be blended with another type of polymer within a range that does not impair the object of the present invention, and may further contain an antioxidant, a heat stabilizer, a lubricant, Inorganic or organic additives such as UV absorbers and nucleating agents may be added to the extent that they are usually added.

The polyester layer B in the present invention is required to have an optical density of 0.5 or more and a whiteness of 80% or more. Particularly, the whiteness is 85 to 150%, preferably 90 to 130%, and the optical density is
It is suitable in the case of 0.9 to 5.0, preferably 1.2 to 3.0. This is not preferable when a base material having a small whiteness is used, since coloring is observed when used as a magnetic recording card, while when the optical density is small, a sufficient amount of light reflection cannot be obtained with the naked eye. When viewed, it is not preferable because the whiteness is decreased, the opposite surface is affected, or trouble occurs depending on the measuring method at the time of reading the magnetic recording. Further, when the substrate having the whiteness and the optical density of the present invention is used, the adhesiveness is improved as compared with the case where a raw material is usually used.

The method for obtaining such optical density and whiteness is not particularly limited, but usually, it can be obtained by adding inorganic fine particles or a resin incompatible with polyester. The amount to be added is not particularly limited, but in the case of inorganic fine particles, it is 5 to 35% by weight, preferably 8 to 25% by weight. On the other hand, when an incompatible resin is added, it is 5 to 35 vol%, preferably 8 to 25 vol%.

The inorganic fine particles used are not particularly limited, but the average particle size
Inorganic particles of 0.1 to 4 μm, preferably 0.3 to 1.5 μm can be mentioned as a representative. Specifically, barium sulfate, calcium carbonate, calcium sulfate, silica, alumina, talc, clay and the like, or a mixture thereof, these inorganic particles, normal inorganic particles, for example, calcium phosphate, titanium oxide, mica, zirconia, You may use together with tungsten oxide, lithium fluoride, calcium fluoride, etc. Further, among the above-mentioned inorganic particles, the one having a Mohs hardness of 5 or less, preferably 4 or less is more preferable because the whiteness is further increased.

The resin which is incompatible with the polyester is not particularly limited. For example, in the case of mixing with polyethylene terephthalate, acrylic resin, polyethylene, polypropylene, modified olefin resin, polybutylene terephthalate resin, phenoxy resin, polyphenylene oxide. And the like, and may be used in combination with the above-mentioned inorganic particles.

Further, the polyester layer B of the present invention may have a whiteness and an optical density within the range of the present invention, and a white film and a film colored in another color (the coloring method is not particularly limited, but usually a pigment, It goes without saying that a laminate of two or more layers with a dye or a transparent film may be used.

In the present invention, the concentration of the sulfonic acid or sulfonate in the surface layer 10 nm of layer B needs to be 0.002% or more. Preferably 0.006% or more, more preferably 0.02%
That is all. If it is less than 0.002%, the coating strength is poor.

In the present invention, the method of adding the sulfonic acid or sulfonate is not particularly limited, but is in the form of a polymer, preferably a polymer having a weight average molecular weight of 1000 or more, more preferably 1
It is preferable to add it in the form of a polymer of 10,000 or more, more preferably 50,000 or more. The polymer having sulfonic acid or sulfonate is not particularly limited, but as a typical one, In the form of acrylic acid, acrylic acid ester, methacrylic acid, methacrylic acid ester, or copolymerized with styrene, or A polymer consisting of only Polymers obtained by using as a part or all of the dicarboxylic acid of various polyesters can be mentioned.

But among them When the polymer introduced in the form of is used, it is considered that the compatibility with the polyester as the base polymer is insufficient, but the improvement effect is more remarkable, which is preferable.

However, -X is not particularly limited, but is H ⁺ , Na ⁺ , K ⁺ , -N
H ₄ ^+, -Li ^+, a cationic ion such as -Ca ^++. Among them, NH ₄ ⁺ , Li ⁺ , Ca ⁺⁺ and K ⁺ are preferable, and Li ⁺ , K ⁺ and Ca ⁺⁺ are particularly preferable, from the viewpoint of thermal stability when mixed with polyester and extruded.

There are various methods for setting the concentration of the layer B in the surface layer of 10 nm within the range of the present invention, and the method is not particularly limited.
Examples thereof include a method in which necessary additives are kneaded, a method in which the kneaded layer and the substrate are combined, and a method in which a layer having necessary additives is applied. However, the manufacturing method is simple, and the physical properties of the polyester base material are not deteriorated,
Further, a method of kneading is excellent from the viewpoint of excellent toughness of the coating film, and in particular, a method of kneading using the method described below is excellent. That is, a compound having a sulfonic acid or a sulfonate such that the melt viscosity of the base film at the melt extrusion temperature is 1/2 or less of the base polyester, preferably 1/3 or less, more preferably 1/8 or less. Is mixed with a predetermined polyester using an extruder having a so-called compression ratio (ratio of the polymer filling amount in the feed part and the metalling part (cross-sectional area ratio)) of 3.8 or more, which is a parameter indicating the degree of kneading in the extruder. It is preferable to perform extrusion molding on a cooling drum followed by stretching and heat treatment with the time from polymer injection to discharge from the die set to 10 minutes or longer, preferably 15 minutes to 120 minutes. The film thus obtained has a particularly high concentration of sulfonic acid or sulfonate in the surface layer 10 nm as compared with the central portion of the film, and thus enhances coating film adhesion without deteriorating the characteristics of the substrate. This is preferable because it is possible.

However, the concentration of sulfonic acid or sulfonate in the surface layer of 10 nm in the present invention means Shimadzu X-ray photoelectron spectroscopy ESCA75.
C at the outermost surface 100Å under the following measurement conditions using 0
It is expressed by the relative intensity ratio of S _{2p to 1s} .

-Measurement condition-Excitation X-ray: MgKα _1,2 line (1253.6eV) X-ray output: 8kV, 30mA Temperature: 20 ° C Vacuum degree: 10 ^-5 Pa General formula in the present invention The polymer having the repeating unit as a main constituent is a polymer sulfonate or polymer sulfonic acid containing a polymer having different sulfone group introduction rates. Although there is no limitation on the introduction rate of the sulfo group, the introduction rate is 40 to 10 from the viewpoint of conductivity.
0 mol% is preferred. It is more preferably 75 mol% to 100 mol%, still more preferably 90 mol% to 100 mol%. Naturally, the copolymer of the compound having the above general formula and styrene, methacrylic acid (ester), acrylic acid (ester), or fumaric acid (ester) is also included in the present invention,
The compound represented by the above general formula is 40 mol% or more, preferably 60
% Or more, more preferably 90% or more and 100% or less, it is preferable from the viewpoint of conductivity.

The molecular weight is not particularly limited, but is preferably 10 to 5,000,000, more preferably 2000 to 1,000,000, and further preferably 10,000 to 500,000.

The coating layer provided on the base material has a general formula A polymer having the following repeating unit as a main constituent and a mixture with another resin are used.

The resin to be mixed is not particularly limited, but it is preferable to mix it with a water-soluble or water-dispersible resin from the viewpoint that it can be applied in the form of an aqueous paint and the dispersibility. As the water-soluble or water-dispersible resin, a polyester resin, an acrylic resin, a polyamide resin, a urethane resin, a vinyl resin, a butadiene resin, an epoxy resin, a silicone resin, or a mixture thereof is thermoplastic. , And thermosetting properties can be used.

Methylol- or alkylol-based urea-based, melamine-based, acrylamide-based, polyamide-based resins and epoxies as cross-linking agents to improve the adhesion (blocking), water resistance, solvent resistance, and mechanical strength of the coating layer Compound, aziridine compound, blocked polyisocyanate,
A reactive compound such as a vinyl compound may be contained in the coating layer. The coating layer of the present invention, if necessary, an antifoaming agent,
Coatability improver, thickener, organic lubricant, inorganic fine particles,
An antioxidant, an ultraviolet absorber, a foaming agent, a dye, a pigment and the like may be contained.

However, among them, water-dispersible or water-soluble acrylic is particularly preferable in terms of transparency.

The water-dispersible or water-soluble acrylic resin (hereinafter abbreviated as "acrylic resin") is preferably one having an alkyl acrylate or an alkyl methacrylate as a main component, and 30 to 99.9 mol% of the component is copolymerized with these. A water-soluble or water-dispersible resin containing 70 to 0.1 mol% of a vinyl monomer component which is possible and has a functional group is preferable.

Vinyl monomers copolymerizable with alkyl acrylate or alkyl methacrylate and having a functional group,
It is preferable to impart hydrophilicity to the resin to improve the water dispersibility of the resin, or to have a functional group that improves the adhesiveness between the resin and the polyester film, or another coating layer provided on the undercoat layer, Preferable functional groups include carboxyl group or salt thereof, acid anhydride group, sulfonic acid group, or salt thereof, amide group or alkylated amide group, amino group (including substituted amino group) or alkylolated group. And amino groups or salts thereof, hydroxyl groups, epoxy groups and the like. Particularly preferred are a carboxyl group or a salt thereof, an acid anhydride group, an epoxy group and the like. Two or more of these groups may be contained in the resin.

The reason why the content of the alkyl acrylate or alkyl methacrylate in the acrylic resin is preferably 30 mol% or more is because the coating formability, the strength of the coating film, and the blocking resistance are improved. Alkyl acrylate or alkyl methacrylate in the acrylic resin is preferably 99.9 mol% or less, by introducing a compound having a specific functional group as a copolymerization component into the acrylic resin, water-soluble, water-dispersed The purpose is to make it easier and to stabilize the state for a long period of time, further improve the adhesiveness between the coating layer and the polyester film layer, the strength of the coating layer by the reaction in the coating layer, the water resistance, the improvement of chemical resistance, Further, it is possible to improve the adhesiveness between the film of the present invention and other materials.

Examples of the alkyl group of acrylic acrylate or alkyl methacrylate include methyl group, ethyl group, n
-Propyl group, isopropyl group, n-butyl group, isobutyl group, t-butyl group, 2-ethylhexyl group, lauryl group, stearyl group, cyclohexyl group and the like.

As the vinyl monomer having a functional group copolymerizable with an alkyl acrylate or an alkyl methacrylate, the following compounds having a functional group such as a reactive functional group, a self-crosslinkable functional group, and a hydrophilic group can be used.

Examples of the compound having a carboxyl group or a salt thereof, or an acid anhydride group include acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, crotonic acid, metal salts of these carboxylic acids with sodium, ammonium salts, and the like. And maleic anhydride.

As the compound having a sulfonic acid group or a salt thereof,
Examples thereof include vinyl sulfonic acid, styrene sulfonic acid, metal salts of these sulfonic acids with sodium, and anomonium salts.

Examples of the compound having an amide group or an alkylolated amide group include acrylamide, methacrylamide, N-methylmethacrylamide, methylolated acrylamide, methylolated methacrylamide, ureido vinyl ether, β-ureido isobutyl vinyl ether, ureido ethyl acrylate, and the like. No.

Examples of the compound 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, and dimethylaminoethyl. Examples thereof include vinyl ethers, those obtained by converting their amino groups to methylol, those obtained by quaternary salification with an alkyl halide, dimethyl sulfate, sultone or the like.

Examples of the compound having a hydroxyl group include β-hydroxyethyl acrylate, β-hydroxyethyl methacrylate, β-hydroxypropyl acrylate, β-hydroxypropyl methacrylate, β-hydroxyvinyl ether, 5-hydroxypentyl vinyl ether,
Examples include hydroxyhexyl vinyl ether, polyethylene glycol monoacrylate, polyethylene glycol monomethacrylate, polypropylene glycol monoacrylate, and polypropylene glycol monomethacrylate.

Examples of the compound having an epoxy group include glycidyl acrylate and glycidyl methacrylate.

Further, in addition to the above, the following compounds may be used in combination. That is, acrylonitrile, methacrylonitrile, styrenes, butyl vinyl ether, maleic acid mono- or dialkyl ester, fumaric acid mono- or dialkyl ester, itaconic acid mono-or dialkyl ester, methyl vinyl ketone, vinyl chloride, vinylidene chloride, vinyl acetate, vinylipyridine, Examples thereof include vinylpyrrolidone and vinyltrimethoxysilane, but are not limited thereto.

The acrylic resin may contain a surfactant, but the low molecular weight surfactant containing the acrylic resin is condensed during the film formation process and accumulated at the particle-particle interface, or the coating layer. There is a case where problems occur in the mechanical strength, water resistance, and adhesiveness with the laminate of the coating layer due to migration to the interface. In such a case, a polymer obtained by so-called soap-free polymerization containing no surfactant can be used.

However, among them, a copolymer of methyl methacrylate and methyl acrylate of 35/65 to 65/35 (molar ratio) is used as a trunk polymer, and 1% to 5% by weight of each of -COOH and -CH ₂ OH is introduced to obtain a water-dispersible acrylic resin. It is particularly suitable.

In the coating layer A in the present invention, the general formula as described above is used. 5% by weight of a polymer having a repeating unit of
It is necessary that the content is not less than 95% by weight. When it is less than 5% by weight, the antistatic property is insufficient, which is not preferable, while when it is more than 95% by weight, the toughness of the coating film becomes poor, which is not preferable. Especially 10% by weight to 30
When the content is wt%, the balance between the toughness of the coating film and the antistatic property is good, which is preferable.

The thickness of the coating layer after stretching is not particularly limited, but usually
It is 0.001 to 5 μm. It is preferably 0.01 to 0.4 μm, and more preferably 0.04 to 0.2 μm from the viewpoint of antistatic property.

In the present invention, the coating layer A has at least one surface thereof,
It is necessary that it is preferably on the ink printing surface side. However, when it is provided on both sides, it is more preferable in terms of durability and product yield.

Inorganic particles may be added to the coating layer A, if necessary, but representative examples thereof include the above-mentioned inorganic particles having an average particle size of 1 μm or less, and more preferably 0.5 μm.
The following, particularly preferably 0.2 μm or less, specifically include kaolin, silica, silica sol, calcium carbonate, titanium oxide, barium salt, alumina, molybdenum sulfide, carbon black, zirconium, etc., but are not limited thereto. Not something.

However, among them, the use of a swelling layered silicate is preferable from the viewpoint of slipperiness and coating film toughness. Examples of the layered silicate exhibiting swelling property include montmorillonite, vermiculite, hectorite, teniolite, and tetrasilicic mica, but from the viewpoint of transparency, synthesized teniolite, hectorite, tetrasilicic mica. Is preferred.

The mixing ratio of the inorganic particles to be added to the solid content in the coating material is not particularly limited, but is preferably 0.05 to 8 parts by weight, more preferably 0.1 to 3 parts.

The magnetic recording layer in the invention is not particularly limited, but the following can be mentioned as typical examples. That is, as the magnetic powder, γ-Fe ₂ O ₃ , CrO ₂ , CO-γ-Fe ₂ O ₃ ,
Metal powder, and as a binder, vinyl acetate, polyvinyl chloride (PVC) and other vinyl resins, acrylonitrile / butadiene copolymer and other rubber resins, acetyl cellulose / nitrocellulose and other fibrin materials, epoxy resins, Phenolic resins, monomeric isocyanates, modified isocyanates, urethane prepolymers, polyurethane resins used in the form of blocked isocyanates and the like, and optionally added dispersants, lubricants, antistatic agents such as carbon, stabilizers, The thing which mixed the plasticizer can be mentioned.

In the present invention, a printing layer to which a color material such as an organic pigment, an inorganic pigment or a dye is added may be appropriately provided, if necessary. The method of providing these printing layers is not particularly limited, but it is possible to use a method such as letterpress, planographic printing, intaglio, screen, flat base, rotary printing, or thermal printing.

Next, a typical manufacturing method of the present invention will be described, but the present invention is not limited to this.

First, a compound having a sulfonic acid or a sulfonic acid salt, a whiteness, an additive for giving an optical density, and other various additives if necessary, are thoroughly dried, and then pellets of polyester are mixed. It is supplied to a melt extruder having a compression ratio of 3.8 or more, and melt-extruded into a sheet form from a slit die at a temperature not lower than a temperature at which pellets melt but not higher than a temperature at which a polymer decomposes, and then cooled and solidified to form an unstretched sheet. The unstretched sheet or the unstretched sheet is added in an amount of 80 to 10
After stretching 3 to 8 times at 5 ° C, at 80 to 130 ° C, when an unstretched film is used, it is 3 to 6 times in the machine direction and 3 to 6 in the transverse direction.
2 times, simultaneous biaxial stretching, and in the case of using a uniaxially stretched film, 3 to 6 times in the transverse direction. 150 if necessary
Heat treatment is performed at ~ 250 ° C for 0.1 to 10 seconds while giving 0 to 10% relaxation.

If necessary, it may be stretched 1.1 to 1.7 times in the longitudinal direction again.

Further, it goes without saying that the coating may be carried out on a composite of a polyester to which a compound having a sulfonic acid or a sulfonate is added and an ordinary polyester.

On at least one surface of the polyester layer B having the predetermined sulfonic acid or sulfonate concentration, optical density, and whiteness thus obtained, the general formula Layer A containing the following repeating unit as a main constituent component is provided. The method of providing is not particularly limited, but it may be applied onto a polyester film substrate having predetermined physical properties by using a known method such as gravure coating, reverse coating, bar coating, spray coating, or comma coating.

In order to improve the coating property of the coating agent on the film and the adhesiveness, the film may be subjected to chemical treatment or discharge treatment before coating, but in the present invention, the affinity with the base film is improved. There is no particular need. In addition, it is preferable to apply the coating material to the layer A, and then perform drying and stretching in at least uniaxial direction and heat treatment to apply the coating material in the substrate film forming step because the toughness and adhesion of the coating film are further improved. On the composite film thus obtained, a predetermined magnetic powder and a binder were dispersed using a ball mill, a vibration mill, an attritor, a homomixer, a sand mill, a triple roll or the like, and then a known method was used. Apply using. If necessary, various ink layers or various receiving layers, specifically, for example, a heat-sensitive transfer ink receiving layer may be provided on the opposite surface. Needless to say, an overcoat layer such as an acrylic resin layer may be provided on these.

[Evaluation method of characteristics and effects] (1) Thickness of coating film A cross-sectional photograph in the thickness direction of a biaxially stretched polyester film provided with a coating layer is taken by a scanning electron microscope (manufactured by Hitachi, Ltd.).
S800 type) and the thickness of the coating layer was measured. The thickness is
The average value was obtained by sampling 10 points in the width direction of the film.

(2) Antistatic property: Measured as an index of product yield, surface resistivity is 10 ¹² Ω / □ or less, charge decay is
If it is 30 seconds or less, the product yield is judged to be good.

(A) Surface resistivity super insulation resistance meter MODEL-VE-40 (Kawaguchi Electric Industry Co., Ltd.)
Manufactured), the surface specific resistance value (Ω / □) at 20 ° C. and 60% RH at an applied voltage of 100 V was measured.

(B) Charge decay After statically charging the coating surface of a biaxially stretched polyester film at a discharge voltage of 10 kV using a static neostometer type S-4104 (manufactured by Shishido Shokai), the charge decay at 20 ° C and 60% RH is halved. The value (second) was evaluated.

(3) Durability After coating and drying the following two types of paints on the coating film, the coating film is brushed 30 times by hand, and then peeled off at 90 ° C. using a commercially available cellophane adhesive tape (manufactured by Nichiban Co., Ltd.). Then, the peeled state was evaluated. The case where peeling did not occur at all was judged as "A", the case where peeling did not occur at all was judged as "○", and the other cases were judged as "X".

UV ink: Toyo Ink (coated) FDS (black) and FDO (black) were applied in an amount of 2 μm and processed for 30 seconds at an irradiation output of 80 W / cm and an irradiation distance of 10 cm.

Magnetic layer: 80% by weight of γ-Fe ₂ O ₃ was added to a binder in which diphenylmethane diisocyanate, adipic acid, isophthalic acid, 1,4 butanediol and neopentyl glycol were mixed in a ratio of 1: 1.9: 0.2: 3.0: 0.4. The adhesiveness with things was examined.

(4) Whiteness Measured according to JIS-L1015.

(5) Optical density It was measured using a transmission densitometer TD-504 manufactured by Macbeth.

[Examples] Next, embodiments of the present invention will be described based on Examples.

Examples 1 to 7 and Comparative Examples 1 to 5 In polyethylene terephthalate having an intrinsic viscosity of 0.61, 82 mol% of terephthalic acid, 8 mol% of isophthalic acid and 10 mol% of a sodium salt of 5-sulfoisophthalic acid were added as a diol component. Polyester copolymer with a molecular weight of about 30,000 and an average particle size of 0.3
The resin mixed with various addition amounts of titanium oxide of μm was melted at 285 ° C. with a screw having a compression ratio of 3,8 and extruded on a cooling drum having a surface temperature of 50 ° C. At this time, the time from polymer injection to polymer discharge was 18 minutes. The film thus obtained was stretched 4 times in the machine direction at 85 ° C. (concentration S _2p / C _1s of sulfonic acid or sulfonate in the surface layer of this film is shown in the table).

Then, while coating and drying the following paints on both sides of the film, stretch the film 3.5 times in the transverse direction at 100 ° C, and then draw at 5 ° C at 220 ° C.
The film was heat-treated while being relaxed to obtain a film having a thickness of 190 μm.

After providing a magnetic layer composed of the binder and γ-Fe ₂ O ₃ powder shown in the durability evaluation method on one surface of the film, FDO (black) and FDS (black) of Toyo Ink Co., Ltd. were provided on the opposite surface of the film. )
Was used to print. The magnetic recording card thus obtained was evaluated.

Water dispersible acrylic: 50:50 copolymer of methyl methacrylate and methyl acrylate. However, 2.5 mol% of each —COOH and —CH ₂ CH group was copolymerized. The water-dispersible acrylic has a number average molecular weight of 500,000.

Sulfonated polystyrene or its salt: Sulfonation rate 98
%, A sulfonated polystyrene having a number average molecular weight of 150,000 and having a sulfone group terminal of H ⁺ (indicated as —SO ₃ H in the table).

As can be seen from the table, good quality is exhibited only when the whiteness and optical density of the polyester film layer B and the concentration of the sulfonic acid or sulfonate in the surface layer of 10 nm are within the range of the present invention. That is, when the whiteness, the optical density, and the concentration of the sulfonic acid or the sulfonate in the surface layer of 10 nm are out of the range of the present invention, the adhesiveness is poor.

[Effect of the invention] General formula After the layer A containing a polymer having the following repeating unit as a main constituent is provided on the polyester layer B in which the whiteness, the optical density, and the concentration of the sulfonic acid or the sulfonate at the surface layer 10 nm are equal to or more than a certain value, Since the magnetic recording layer is provided, the following effects can be obtained.

(1) The durability during use is improved.

(2) The yield at the time of product manufacturing is improved.

Claims (1)

(57) [Claims] (1) General formula (Wherein R is hydrogen or methyl group, M is hydrogen, alkali metal, alkaline earth or ammonium, R ₁ , R ₂ , R ₃ and R ₄ are each hydrogen, halogen, alkyl group or alkoxy group) 5% by weight of polymer as main constituent
On the polyester layer B having an optical density of 0.5 or more, a whiteness of 80% or more, and a concentration of sulfonic acid or sulfonate in the surface layer of 10 nm of 0.002% or more having at least one layer A containing at least 95% by weight, or A magnetic recording card comprising a magnetic recording layer provided via a layer A.