JP2003080652A - Coating film for magnetic recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyester film excellent in flatness and blocking resistance at the time of roll taking-up and suitable as the base film of a ferromagnetic metal thin film type magnetic recording medium for recording digital data for a magnetic recording medium, especially for a digital video cassette tape, data storage or the like. SOLUTION: The coating film for the magnetic recording medium is a laminated film formed by laminating a coating film layer A to one surface of the polyester film. The coating film layer A is composed of a binder resin A, inert particles A and a surfactant A. The surfactant A comprises a first surfactant A with an HLB value of 10-14 and a second surfactant A with an HLB value of 16-20. The content on the basis of the weight of the coating film layer A of the first surfactant A is 0.5-15 wt.% and the content of the second surfactant A is 1-<10 wt.%. A magnetic recording tape is also disclosed.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a coating film for a magnetic recording medium. More specifically, it has excellent blocking resistance during roll winding, and has excellent electromagnetic conversion characteristics when used as a base film of a ferromagnetic metal thin film type magnetic recording medium for recording digital data such as digital video cassette tapes and data storage. The present invention relates to a polyester film that expresses.

[0002]

2. Description of the Related Art A consumer digital video tape put into practical use in 1995 has a metallic magnetic thin film of Co provided on one surface (magnetic surface side) of a base film and a diamond-like carbon film coated on the surface thereof. The back coat layer is applied to the other surface (nonmagnetic surface side) of the base film. Although this consumer digital video tape has a smoother surface than the conventional Hi8ME tape, it also has good durability and runnability. This consumer digital video tape is also used for computer data backup. For example, a data 8 mm computer data backup device with a tape width of 8 mm (product name "Mammoth" manufactured by Exabyte, Inc., product name "AIT system" manufactured by Sony Corporation)
Has been put to practical use, and it is extremely excellent in that it is small in size, has a large capacity, and has a high data transfer rate.

As a base film for such a consumer digital video tape, (1) a polyester film, a polyester consisting of a discontinuous film adhered to at least one side of the film and fine particles present in and on the film surface Film (for example, Japanese Patent Publication No. 62-3010)
No. 5), (2) A film which is a smooth polyester film and has a nonmagnetic surface side coated with a lubricant-based coating layer (see, for example, JP-A-57-195321, Japanese Patent Publication No.
No. 49116 or Japanese Patent Publication No. 4-33273) is used. The roughness of the surface of these base films on the side on which the metal magnetic film is formed is becoming smaller than that of the conventional base film for Hi8ME tape.

[0004]

However, even though these base films can secure the handling property in the film forming and processing steps, when they are wound in a roll state, blocking of the films is likely to occur, and the roll film is wound. There was a problem that the film would be cut or torn at the delivery stage.

It is considered that this blocking causes the film to be in an adhesive state because moisture in the air penetrates from the film surface or between the films and pressure is applied between the films in the presence of this moisture. As a countermeasure for this, it is possible to store the roll-shaped product after film production or before unwinding under low humidity. This storage method can prevent blocking to some extent, but in the case of a film having an extremely flat surface such as a polyester film for a vapor-deposited magnetic recording medium, it is very difficult to prevent blocking only by this method. Have difficulty.

When blocking occurs, the polyester film is likely to be charged when the film is peeled off. A highly charged film (1) tends to have a markedly deteriorated handling property when the film is formed or formed into a tape, and (2) sparks are easily generated due to charging,
There is a risk of ignition of the organic solvent used when forming the tape, and (3) it is easy to electrically adsorb floating dust in the air, and this dust causes errors and dropouts when it is used as a vapor deposition tape. There were problems such as being easy.

The object of the present invention is to solve these problems,
Excellent in flatness and blocking resistance during roll winding, suitable for magnetic recording media, particularly for digital video cassette tapes, suitable as a base film for ferromagnetic metal thin film magnetic recording media for recording digital data for data storage, A polyester film for a magnetic recording medium and a magnetic recording medium using the same.

[0008]

The object of the invention is, according to the invention, the coating layer A on one side of a polyester film.
Wherein the coating layer A comprises a binder resin A, inert particles A and a surfactant A, the surfactant A being a first HLB value of 10 or more and 14 or less.
A surfactant A and a second surfactant A having an HLB value of 16 or more and 20 or less, and based on the weight of the coating layer A,
The content of the first surfactant A is 0.5% by weight or more and 15% by weight or less, and the content of the second surfactant A is 1% by weight or more and 10% by weight or more.
It is achieved by a coating film for a magnetic recording medium which is less than wt%.

In a preferred embodiment of the coating film for a magnetic recording medium of the present invention, the first surfactant A has an HLB value of 11 or more and 13.5 or less and a coating layer A.
The content in the composition is 1% by weight or more and 10% by weight or less,
The second surfactant A has an HLB value of 16.5 or more and 18 or less and a content in the coating layer A of 1% by weight or more and 7% by weight or less, and the binder resin A is water-soluble or water-dispersible. Of at least one resin selected from the group consisting of polyester resin A, acrylic resin A, or acrylic-polyester resin A, the average particle diameter of the inert particles A is 3 nm or more and 50 nm or less, and the coating layer A On the surface not in contact with the polyester film, the frequency of protrusions by the inert particles A is 1 million pieces / mm ² or more and 30 million pieces / mm ² or less, and the surface of the coating layer A not in contact with the polyester film is AFM. The root mean square roughness (Ra) is 0.1 nm or more and 3 nm or less, and the 10-point average roughness (Rz) is 10 nm or more and 50 nm or less. The coating layer B is laminated on the other surface, and the coating layer B contains the cellulose derivative B in an amount of 5% by weight or more and 50% by weight or more.
The polyester film is made of polyethylene terephthalate or polyethylene-2,6-naphthalene dicarboxylate, and has a thickness of 2 μm.
It also includes a coating film for a magnetic recording medium having at least one of the above values of less than 7 μm and being used for a digital recording type magnetic tape.

Still another object of the present invention is, according to the present invention, the above-mentioned coating film for a magnetic recording medium of the present invention and the magnetic film formed on the surface on which the coating layer A is formed. Layer and a magnetic recording medium comprising a back coat layer formed on the surface on which the coating layer A is not formed,
In particular, it is achieved by a magnetic recording medium in which the magnetic layer is a ferromagnetic metal thin film layer.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The coating film for a magnetic recording medium of the present invention is a laminated film in which a coating layer A comprising a binder resin A, inert particles A and a surfactant A is laminated on one surface of a polyester film. . The greatest feature of the present invention is that the surfactant A contained in the coating layer A is a first surfactant A having an HLB value of 10 or more and 14 or less.
And a second surfactant A having an HLB value of 16 or more and 20 or less, and the content of the first surfactant A is 0.5% by weight or more and 15% by weight or less based on the weight of the coating layer A. Second
That is, the content of the surfactant A is in the range of 1% by weight or more and less than 10% by weight.

If only one kind of the surfactant A is used, it is impossible to prevent blocking of the film and solve problems such as omission of coating due to foam streaks and cissing.
If the HLB value of the first surfactant A is less than 10, foaming tends to occur when the coating liquid is applied and streak-shaped coating defects are likely to occur, and the content of the first surfactant A exceeds 15% by weight. In addition to the foam streak defect due to foaming, the film tends to cause blocking. On the other hand, H of the first surfactant A
If the LB value is more than 14 or the content of the first surfactant A is less than 0.5% by weight, the effect of lowering the surface tension of the coating solution is lowered, and coating omission such as cissing may occur during coating. Will occur. The HLB value of the first surfactant A is preferably 11 or more and 13.5 or less, more preferably 11.5 or more 1
It is 3 or less. The content of the first surfactant A in the coating layer A must be 0.5% by weight or more and 15% by weight or less, preferably 1% by weight or more and 10% by weight or less, more preferably 1% by weight or more. It is at least 7.5% by weight and at most.

When the HLB value of the second surfactant is less than 16 or the content thereof is less than 1% by weight, coarse projections are apt to occur due to aggregation of the coating agent. On the other hand, the second surfactant A
When the HLB value is more than 20, coating omission easily occurs due to a decrease in surface tension, and when the content is 10% by weight or more, blocking easily occurs. The HLB value of the second surfactant A is preferably 16.5 or more and 19 or less, more preferably 17 or more and 18.5 or less. The content of the second surfactant A in the coating layer A is 1% by weight.
It is necessary to be 10% by weight or more and less than 10% by weight, preferably 1% by weight or more and 7% by weight or less, and more preferably 1% by weight or more and 5% by weight or less.

The present invention is described in detail below.

[Polyester Film] The polyester film in the present invention will be described in detail. Polyester constituting the polyester film includes polyethylene terephthalate, polyethylene isophthalate, polytetramethylene terephthalate, poly-1,4-cyclohexylene dimethylene terephthalate, polyethylene-
Preferred examples include 2,6-naphthalenedicarboxylate. Of these, polyethylene terephthalate and polyethylene-2,6-naphthalene dicarboxylate are particularly preferred.

The above polyester may be a homopolyester or a copolyester. In the case of copolyester, examples of the copolymerization component of polyethylene terephthalate and polyethylene-2,6-naphthalene dicarboxylate include diethylene glycol, propylene glycol, neopentyl glycol, polyoxyethylene glycol, p-xylene glycol, 1,4-
Diol components such as cyclohexanedimethanol, adipic acid, sebacic acid, phthalic acid, isophthalic acid, terephthalic acid (in the case of polyethylene-2,6-naphthalenedicarboxylate), 2,6-naphthalenedicarboxylic acid (but not of polyethylene terephthalate) In the case), other dicarboxylic acid components such as 5-sodium sulfoisophthalic acid and oxycarboxylic acid components such as p-oxyethoxybenzoic acid may be mentioned. The amount of the copolymerization component is preferably 20 mol% or less, more preferably 10 mol% or less with respect to the total acid component. Further, a trifunctional or higher polyfunctional compound such as trimellitic acid or pyromellitic acid may be copolymerized. When the polyfunctional compound is copolymerized, the copolymerization amount is preferably in the range where the polymer is substantially linear, for example, in the range of 2 mol% or less.

The polyester film in the present invention is
It may contain inert particles. For convenience of explanation, the inert particles contained in the polyester film,
Hereinafter, it may be referred to as an inert particle C. Inert particle C
May be organic particles or inorganic particles. As specific organic particles, polystyrene, polystyrene-divinylbenzene, polymethylmethacrylate, methylmethacrylate copolymer, methylmethacrylate copolymer crosslinked product,
Particles made of polymers such as polytetrafluoroethylene, polyvinylidene fluoride, polyacrylonitrile and benzoguanamine resin, and core-shell structured particles made of a graft copolymer containing these polymers as components are preferable. Further, as specific inorganic particles, silica,
Particles made of an inorganic compound such as alumina, titanium dioxide, feldspar, kaolin, talc, graphite, calcium carbonate, molybdenum disulfide, carbon black, barium sulfate are preferred.

These inert particles C can be usually added at any stage from the step of producing a polyester to the step of extruding the polyester in an unstretched film state in a molten state. Specifically, it is preferably added as a slurry in glycol during the transesterification or polycondensation reaction in the transesterification method and during the polycondensation reaction in the direct polymerization method. The average particle size of the inert particles C is 0.03 μm or more.
It is preferably 0 μm or less, more preferably 0.05 μm or more and 0.3 μm or less, and the upper limit of the addition amount is 0.
It is preferably 5% by weight or less, and more preferably 0.2% by weight or less. If the average particle size exceeds 1.0 μm or the added amount exceeds 0.5% by weight, the electromagnetic conversion characteristics may deteriorate. On the other hand, if the average particle size is less than 0.03 μm, the particles are likely to aggregate, which is not preferable.

The polyester film in the present invention is
The film may have a single-layer structure or a multi-layer film having two or more layers formed by a coextrusion method or the like. In the case of a multilayer film, the surface on which the magnetic layer is formed (the magnetic layer side)
It is preferable that the polyester forming the composition contains substantially no inactive particles, or even if it contains, the content does not exceed 0.5% by weight. In particular, it is preferable that the content of the inert particles does not exceed 0.2% by weight. Also,
The opposite surface (nonmagnetic layer surface), that is, the polyester forming the surface on the side where the magnetic layer is not formed, is the inert particles C.
0.05 wt% or more and 0.8 wt% or less, further 0.1
It is preferable that the content is from 0.3% to 0.3% by weight.

[Coating layer A] In the present invention, the coating layer A laminated on one side of the polyester film comprises at least a binder resin A, inert particles A and a surfactant A.

Examples of the binder resin include alkyd resin, phenol resin, epoxy resin, amino resin, polyurethane resin, vinyl acetate resin, vinyl chloride-vinyl acetate copolymer, polyester resin, acrylic resin and acrylic-polyester resin. Among these, water-soluble or water-dispersible polyester resins, acrylic resins and acrylic-polyester resins are preferable from the viewpoints of adhesion to the polyester film, protrusion retention, slipperiness and the like. These resins may be homopolymers or copolymers, and may be a mixture.

The water-soluble or water-dispersible polyester resin will be described. The acid component constituting the polyester resin is terephthalic acid, isophthalic acid, phthalic acid, 1,4-cyclohexanedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 4,4′-diphenyldicarboxylic acid, adipic acid, sebacic acid, Dodecane dicarboxylic acid, succinic acid, 5-sodium sulfoisophthalic acid, 2
Examples of the polyvalent carboxylic acid include potassium sulfoterephthalic acid, trimellitic acid, trimesic acid, trimellitic anhydride, phthalic anhydride, p-hydroxybenzoic acid, and trimellitic acid monopotassium salt. The hydroxy compound component constituting the polyester resin is ethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, neopentyl glycol, 1,4-cyclohexanediene. Methanol, p-xylylene glycol, ethylene oxide adduct of bisphenol A, diethylene glycol, triethylene glycol, polyethylene oxide glycol, polytetramethylene oxide glycol,
Examples thereof include polyhydric hydroxy compounds such as dimethylolpropionic acid, glycerin, trimethylolpropane, sodium dimethylolethylsulfonate and potassium dimethylolpropanoate. The polyester resin can be prepared from these polycarboxylic acid and polyhydroxy compound by a conventional method. In particular, an aqueous polyester resin containing a 5-sodium sulfoisophthalic acid component or a carboxylate group is preferable from the viewpoint of producing an aqueous paint. Such a polyester resin can be a self-crosslinking type having a functional group in the molecule, or may be crosslinked using a curing agent such as a melamine resin or an epoxy resin.

The water-soluble or water-dispersible acrylic resin will be described. The acrylic component used for producing the acrylic resin is an acrylic acid ester (as the alcohol residue, a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a t-butyl group, a 2-butyl group, Examples thereof include an ethylhexyl group, a cyclohexyl group, a phenyl group, a benzyl group, and a phenylethyl group); methacrylic acid ester (alcohol residue is the same as above); 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl Hydroxy-containing monomers such as acrylate, 2-hydroxypropyl methacrylate, etc .; acrylamide,
Methacrylamide, N-methylmethacrylamide, N-
Amide group-containing monomers such as methyl acrylamide, N-methylol acrylamide, N-methylol methacrylamide, N, N'-dimethylol acrylamide, N-methoxymethyl acrylamide, N-methoxymethyl methacrylamide, N-phenyl acrylamide; N'-diethylaminoethyl acrylate,
Examples thereof include amino group-containing monomers such as N, N′-diethylaminoethyl methacrylate.
These monomers include monomers containing sulfonic acid groups or salts thereof such as styrene sulfonic acid, vinyl sulfonic acid and salts thereof (eg sodium salt, potassium salt, ammonium salt, etc.); crotonic acid, itaconic acid, acrylic acid, Monomers containing carboxyl groups or salts thereof such as maleic acid, fumaric acid, and salts thereof (for example, sodium salt, potassium salt, ammonium salt, etc.); Monomers containing anhydrides such as maleic anhydride, itaconic anhydride Other vinyl isocyanate, allyl isocyanate, styrene, vinyl methyl ether, vinyl ethyl ether, vinyl trisalkoxysilane, alkyl maleic acid monoester, alkyl fumaric acid monoester, acrylonitrile, methacrylonitrile, al Ruitakon acid monoester, vinylidene chloride, vinyl acetate, may be used vinyl chloride, a monomer such as allyl glycidyl ether combination. In this case, it is preferable that the component of the (meth) acrylic monomer such as the acrylic acid derivative or the methacrylic acid derivative is contained in an amount of 50 mol% or more, and particularly, the one containing the component of methyl methacrylate is preferable.

The water-soluble or water-dispersible acrylic resin can be self-crosslinked with a functional group in the molecule, or can be crosslinked with a crosslinking agent such as a melamine resin or an epoxy compound.

In the present invention, the water-soluble or water-dispersible acrylic-polyester resin includes an acrylic-modified polyester resin and a polyester-modified acrylic resin. Specifically, the acrylic resin component and the polyester resin component are bonded to each other in the form of a graft type or a block type. Acrylic-polyester resin, for example, adds a radical initiator to both ends of a polyester resin to polymerize an acrylic monomer, or adds a radical initiator to a side chain of a polyester resin to polymerize an acrylic monomer. It can be produced by carrying out the reaction, or by attaching a hydroxyl group to the side chain of the acrylic resin and reacting it with a polyester having an isocyanate group or a carboxyl group at the end to form a comb polymer.

The components constituting the acrylic-polyester resin may be the same as those exemplified for the water-soluble or water-dispersible acrylic resin or the water-soluble or water-dispersible polyester resin.

The content of the binder resin A in the coating layer A is preferably 50 to 90% by weight. If it is less than 50% by weight, the adhesion to the film will be reduced, while if it exceeds 90% by weight, other components (inert fine particles, surfactant, etc.) will be insufficient,
The overall characteristics cannot be satisfied.

In the present invention, the inert particles A constituting the coating layer A are polystyrene, polystyrene-divinylbenzene, polymethylmethacrylate, methylmethacrylate copolymer, methylmethacrylate copolymer crosslinked product, polytetrafluoroethylene, polyvinylidene. Preferable particles include organic substances such as fluoride, polyacrylonitrile, benzoguanamine, and silicone, and inorganic substances such as silica, alumina, titanium dioxide, kaolin, calcium carbonate, talc, and graphite. Further, a core-shell type particle having a multilayer structure in which the inside and outside of the particle are made of materials having different properties may be used. The average particle size of the inert particles A is preferably 3 nm or more and 50 nm or less, and more preferably 5 n.
It is m or more and 30 nm or less. If the average particle size is less than 3 nm, friction with the head becomes high when the magnetic recording medium is used, and stable running becomes difficult. On the other hand, if the thickness exceeds 50 nm, the electromagnetic conversion characteristics of the magnetic recording medium may be insufficient, or particles may fall off from the coating layer to cause an error or dropout.

The frequency of protrusions by the inert particles A on the surface of the coating layer A in the present invention which is not in contact with the polyester film (hereinafter sometimes referred to as the surface of the coating layer A) is as follows.
Preferably 1 million pieces / mm ² or more and 30 million pieces / mm ²
Or less, and more preferably 3 million pieces / mm ² or more 2
It is 10 million pieces / mm ² or less. If the frequency is less than 1 million pieces / mm ² , friction with the head becomes high when the magnetic recording medium is used, and stable running becomes difficult. On the other hand, if it exceeds 30 million pieces / mm ² , the electromagnetic conversion characteristics tend to be insufficient when used as a magnetic recording medium.

The surface roughness by AFM of the surface of the coating layer A in the present invention is preferably such that the root mean square roughness (hereinafter sometimes referred to as Ra) is 0.1 nm or more and 3 nm or less. If Ra is less than 0.1 nm, blocking tends to occur. On the other hand, if Ra exceeds 3 nm, problems such as deterioration of electromagnetic conversion characteristics when the magnetic recording medium is used, and easy film abrasion are likely to occur. The surface roughness of the surface of the coating layer A by AFM is 10-point average roughness (hereinafter, R
Sometimes referred to as z. ) Is preferably 10 nm or more and 50 nm or less. If Rz is less than 10 nm, blocking is likely to occur. On the other hand, if Rz is more than 50 nm, problems such as deterioration of electromagnetic conversion characteristics when the magnetic recording medium is used, and easy film abrasion are likely to occur.

The thickness of the coating layer A in the present invention is 0.2 to
20 nm is preferable, and 1 to 15 nm is more preferable.

The surfactant A constituting the coating layer A in the present invention will be described below. The surfactant A is composed of a first surfactant A and a second surfactant B which satisfy the above HLB value. The first surfactant A and the second surfactant B are preferably nonionic surfactants, and particularly preferably alkyl alcohols, alkylphenyl alcohols, and higher fatty acids to which (poly) ethylene oxide is added and bonded. . In particular, as the first surfactant, a nonionic NS206 (H produced by NOF CORPORATION) as a polyoxyethylene alkylphenyl ether compound is used.
LB10.9), NS208.5 (HLB12.6),
HS208 (HLB12.6), HS210 (HLB1
3.6), Sanyo Kasei Octopole 60 (HLB1
1.3), Octapole 80 (HLB12.4), Octapole 95 (HLB13.3), Octapole 100
(HLB13.6), Dodecapole 90 (HLB12.
0), Dodecapol 120 (HLB13.4), Nonion P-210 (HLB12.9) manufactured by NOF CORPORATION as a polyoxyethylene alkyl ether compound, Nonipol Soft SS50 (HLB10.5) manufactured by Sanyo Kasei, and Nonipol. Soft SS70 (HLB12.8), Nonipol Soft SS90 (HLB13.2), DO70 (HL
B12.3), DO90 (HLB13.4), nonionic L-4 (HLB13.1) and S-4 (H) manufactured by NOF CORPORATION as polyoxyethylene ester compounds of higher fatty acids.
LB11.6), S-6 (HLB13.6) and the like are preferable. Further, as the second surfactant, nonionic NS230 (HLB17.2) and NS2 manufactured by NOF CORPORATION are used as polyoxyethylene alkylphenyl ether compounds.
40 (HLB17.8), HS220 (HLB16.
2), HS240 (HLB17.9), Sanyo Kasei's Nonipol 200 (HLB16.0), Nonipol 400
(HLB17.8), Nonipol 500 (HLB18.
2), Octapole 400 (HLB17.9), nonionic E-230 (HLB16.6) and K-22 manufactured by NOF CORPORATION as polyoxyethylene alkyl ether compounds.
0 (HLB16.2), K-230 (HLB17.
3), nonionic S-15.4 (HLB1 manufactured by NOF CORPORATION) as a polyoxyethylene ester compound of higher fatty acid
6.7), S-40 (HLB18.2) and the like are preferable.

In the present invention, the coating layer A may optionally contain other components, such as stabilizers, dispersants, UV absorbers, thickeners and release agents, as long as the effects of the present invention are not impaired. Etc. may be contained.

[Coating layer B] The coating film for a magnetic recording medium of the present invention is a coating layer A of polyester film.
On the surface on the side where the film is not formed (hereinafter sometimes referred to as the B surface or the side surface of the non-magnetic layer), the coating layer B is provided for the purpose of preventing blocking and improving the handleability of the film.
Is preferably provided. The coating layer B contains a cellulose derivative in an amount of 5% by weight or more and 50% by weight or less, preferably 1% by weight or less.
0% by weight or more and 40% by weight or less, and 20% by weight of a surfactant (hereinafter, for convenience of description, the surfactant contained in the coating layer B may be referred to as a surfactant B).
Below, it is preferable that the content is 3% by weight or more and 15% by weight or less.

When the content of the cellulose derivative is less than 5% by weight, the surface of the coating layer B becomes flat and the handling property and blocking resistance of the film cannot be improved. Further, the surface tension of the coating liquid becomes high, and cissing tends to occur during coating. On the other hand, when the content of the cellulose derivative exceeds 50% by weight, the coating layer B is easily scraped. Further, from the viewpoint of coatability, the coating layer B preferably contains a surfactant, but if the content exceeds 20% by weight, blocking is likely to occur.

As the surfactant B, any of anionic type, cationic type and nonionic type may be used. Among them, the nonionic type is preferable. Examples of the nonionic surfactant include ester type, ether type and alkylphenol type.

The specific cellulose derivative is not particularly limited, but methyl cellulose or its derivative, ethyl cellulose or its derivative are preferable, and methyl cellulose, hydroxypropyl methyl cellulose, hydroxyethyl methyl cellulose, carboxy methyl cellulose, hydroxyl ethyl cellulose and the like are particularly preferable.

As the binder resin other than the cellulose derivative contained in the coating layer B, polyvinyl alcohol, tragacanth rubber, casein, gelatin, polyester, acrylic, polyester-ether copolymer, polyester-acrylic copolymer, polyurethane, epoxy and the like can be used. A polar polymer and a blend thereof can be preferably used. Particularly preferred binder resins include polyester, acrylic, polyester-acrylic copolymer and the like.

The surface roughness of the surface of the coating layer B in the present invention which is not in contact with the polyester film (hereinafter sometimes referred to as the coating layer B surface) by AFM is Ra = 3.
It is preferably not less than 20 nm and not more than 20 nm. This Ra
Is less than 3 nm, the handling property of the film may be difficult or blocking may occur easily. On the other hand, when Ra exceeds 20 nm, the coating layer B
Is easily scraped. In order to adjust the surface roughness of the coating layer B to such a range, the coating layer B may be provided with inert particles (hereinafter referred to as the coating layer B).
The inactive particles contained in may be referred to as inactive particles B. ) Is added. The average particle diameter of the inert particles B is preferably 10 nm or more and 100 nm or less, and particularly 15
It is preferably not less than 80 nm and not more than 80 nm. If the average particle diameter of the inert particles B is outside this range, it is difficult to obtain the desired surface roughness of the coating layer B surface. Coating layer B of inert particles B
The content ratio is preferably 3% by weight or more and 30% by weight or less, more preferably 5% by weight or more and 25% by weight or less. If the ratio is outside this range, it becomes difficult to achieve the desired roughness.

The thickness of the coating layer B is preferably 5 nm or more and 50 nm or less, and more preferably 10 nm or more and 40 nm or less. If the thickness is less than 5 nm, the slipperiness is poor and blocking is likely to occur. On the other hand, 50
If the thickness exceeds nm, the coating layer is easily scraped.

If desired, the coating layer B may further contain other components such as stabilizers, dispersants, UV absorbers, thickeners and release agents, as long as the effects of the present invention are not impaired. May be.

[Thickness] The thickness of the coating film for a magnetic recording medium of the present invention is preferably 2 μm or more and less than 7 μm, and more preferably 3 μm or more and 6 μm or less. If the thickness is 7 μm or more, the length of the magnetic tape that can be stored in the cassette is insufficient, and the storage capacity tends to be insufficient. On the other hand, when the thickness is less than 2 μm, the film forming stability during film production is lowered, and even if the film is formed, permanent force of the film is generated due to the force applied when the magnetic tape is started or stopped, and the durability is satisfied. In addition, since the tape has poor rigidity and causes poor head contact, it is not preferable.

[Magnetic Recording Medium] The magnetic recording medium of the present invention comprises the above-mentioned coating film for a magnetic recording medium of the present invention, a magnetic layer provided on one surface (surface of coating layer A) and the other surface. And a back coat layer provided. As the magnetic layer, a ferromagnetic metal thin film layer is preferable, and a layer known per se such as a vacuum vapor deposition method or a sputtering method can be preferably used for the formation thereof. The metal forming the ferromagnetic metal thin film layer is preferably made of a ferromagnetic material of iron, cobalt, nickel, chromium or an alloy thereof. The thickness of the metal thin film layer is preferably in the range of 50 to 300 nm.

The back coat layer in the present invention comprises solid fine particles and a binder, and is formed by applying a solution containing various additives as necessary. As the solid fine particles, the binder, and the additives, known ones can be used. The thickness of the back coat layer is preferably 0.3 to 1.5 μm.

[Production Method of Coating Film] The coating film for a magnetic recording medium of the present invention is produced by unidirectional stretching in the usual polyester film (base film) production process including melt molding, biaxial stretching and heat setting. Manufactured by applying the coating liquid for forming the coating layer A on one surface of the polyester film, and if necessary, applying the coating liquid for forming the coating layer B on the other surface, drying, and then stretching in the perpendicular direction and heat setting. it can. In the case of simultaneous biaxial stretching, it can be manufactured by applying a coating solution to an unstretched film, simultaneously biaxially stretching and heat-setting. A known method can be applied as a method of applying the coating liquid. For example, a roll coating method, a gravure coating method, a roll brushing method, a spray coating method, an air knife method, an impregnation method, a curtain coating method and the like can be applied alone or in combination. In the case of successive stretching, the solid content concentration of the coating liquid is preferably 0.1 to 10% by weight, more preferably 0.3 to 5% by weight. In the case of simultaneous biaxial stretching, 0.5 to 20% by weight is preferable. The stretching is preferably performed at least 3 times in the uniaxial direction, and the area magnification is 8 to 30 times, further preferably 12 to 25 times.

[0046]

EXAMPLES The present invention will be further described based on examples. The method of measuring the film characteristic value and the method of evaluating the effect in the present invention are as follows. (1) Average particle size of inert particles The average spherical particle diameter is defined as the equivalent spherical diameter of the particles at the 50 wt% point of all particles determined by the light scattering method.

(2) HLB value of surfactant "Oil Chemistry" (issued by Japan Oil and Fat Chemistry Association, 1964, No. 13,
The molecular weight is measured according to the method described on page 220) and determined by the following formula.

[0048]

[Formula 1] HLB = 20 × Mw / M However, M: molecular weight of surfactant Mw; molecular weight of hydrophilic group of surfactant Is.

(3) Thickness of coating layer A small piece of the film is fixedly molded with an epoxy resin, and an ultrathin section of about 60 nm thickness (cut parallel to the film forming direction) is prepared with a microtome. The sample is observed with a transmission electron microscope (H-800 manufactured by Hitachi Ltd.),
Obtain the layer thickness from the boundary line of the layers.

(4) Protrusion frequency Using a scanning electron microscope, 25 photographs with a magnification of 30,000 were taken, the frequency of protrusions due to inert particles was counted, and the average value was converted to the number per 1 mm ^2. To do.

(5) Surface Roughness Ra (root mean square roughness) and Rz (10-point average roughness) calculated under the following conditions using a J scanner of an atomic force microscope Nano Scope III AFM manufactured by Digital Instruments. Is measured under the following conditions. Probe: Single bond silicon sensor Scan mode: Tapping mode Number of pixels: 256 x 256 data points Scan speed: 2.0Hz Measurement environment: Room temperature, in air

(6) Coarse projection number Aluminum was vapor-deposited to a thickness of 0.5 μm, and it was magnified 400 times by a differential interference method using an optical microscope (manufactured by Nikon, Optiphoto) at a magnification of 2 μm × widthwise 5 μm.
The number of protrusions having a size of m or more is counted, converted into the number per 1 mm ² , and judged according to the following criteria. ◯: 0 to 5 Δ: 5 to 20 ×: 20 or more

(7) Repelling and coating streaks 0.5 μm of aluminum in an area of 30 cm × 30 cm
It is vapor-deposited to a thickness, and the presence or absence of spherical to elliptical coating cissing and coating streaks in the longitudinal direction is visually observed. Those that do not exist are judged as ◯, and those that exist are judged as ×.

(8) Two blocking-resistant coating films were prepared, the surface of the coating layer A of one film and the surface of the other film which was not the coating layer A surface were superposed, and an atmosphere of 50 ° C. × 70% RH was obtained. Under no load for 24 hours, then under a load of 15 N / mm ² for 100 hours, then cut into strips with a width of 5 cm, and peel strength of the applied load with a tensile tester ( mN / 5 cm) is measured. Obtained peel strength (mN
/ 5 cm) and evaluated according to the following criteria. ◯: 0 to 50 (mN / 5 cm) Δ: 50 to 100 (mN / 5 cm) ×: 100 (mN / 5 cm) to fracture occurrence

(9) Production of magnetic tape and evaluation of characteristics On the surface of the coating layer A of the coating film, a cobalt-oxygen thin film having a thickness of 110 nm is formed by vacuum vapor deposition, and then on the cobalt-oxygen thin film layer by a sputtering method. Forming diamond-like carbon with a thickness of 10 nm,
Further, a fluorine-containing carboxylic acid type lubricant is sequentially provided, and subsequently, a back coat layer made of carbon black, polyurethane, and silicone is provided on the surface of the coating film, which is not the surface of the coating layer A, to a thickness of 500 nm.
And slit it to 6.35 mm and wind it on a commercial reel to make a magnetic tape. The number of dropouts (DO) is obtained using a commercially available camera-integrated digital video tape recorder.

The measurement of the number of DO is 6.35 mm prepared.
After recording the tape with a commercially available camera-integrated digital video tape recorder, it is played for 1 minute and the number of block-shaped mosaics appearing on the screen is counted.

The running durability is determined by measuring the S / N after recording / reproducing 700 times at 40 ° C. and 80% RH, and deviating from the initial value. The S / N is provided by a signal from a TV test signal generator and measured using a video noise meter. ◯: +0.0 dB or more relative to the initial value Δ: −1.0 dB or more to less than +0.0 dB relative to the initial value X: Less than −1.0 dB relative to the initial value

[Example 1] Dimethyl 2,6-naphthalenedicarboxylate and ethylene glycol were added, manganese acetate was added as a transesterification catalyst, antimony trioxide was used as a polymerization catalyst, and phosphorous acid was added as a stabilizer. Polyethylene-2,6-naphthalenedicarboxylate, which is polymerized by the following method and contains substantially no inert particles (intrinsic viscosity 0.61, measurement solvent o-chlorophenol, measurement temperature 3
5 ° C) pellets were obtained. This pellet at 170 ℃ 6
After drying for an hour, it was fed to an extruder and melted at 305 ° C. This molten polymer was filtered by a known method, extruded into a sheet form from an extruder, and cooled and solidified on a casting drum to prepare an unstretched film. The unstretched film thus obtained is preheated at 120 ° C., further heated at a film temperature of 140 ° C. between low-speed / high-speed rolls, stretched 3.4 times in the machine direction, and then rapidly cooled. Each aqueous solution of the composition shown below to a polyester film,
The thickness after drying is 6 nm for coating layer A and 18 nm for coating layer B.
Was applied to the film. Composition of coating layer A: (1) Acrylic-polyester resin 84% by weight Polyester component: isophthalic acid (95 mol%), 5-sodium sulfoisophthalic acid (5 mol%) / ethylene glycol (92 mol%), diethylene glycol ( Acrylic resin component: methyl methacrylate (90 mol%), glycidyl methacrylate (10 mol%), weight ratio of polyester component / acrylic resin component = 5/5 (2) Acrylic fine particles (average particle diameter 21 nm ) 6% by weight (3) First surfactant A-Sanyo Chemical Co., Ltd. Octapol 80 (HLB = 12.4) 5% by weight (4) Second surfactant A-Sanyo Chemical Co., Ltd. Octapol 400 (HLB = 17) .9) 5% by weight Composition of coating layer B: (1) Acrylic-polyester resin 60% by weight Polyester component: TE Phthalic acid (70 mol%), isophthalic acid (18 mol%), 5-sodium sulfoisophthalic acid (12 mol%) / ethylene glycol (92 mol%), diethylene glycol (8 mol%)-Acrylic resin component: methyl methacrylate ( 80 mol%), glycidyl methacrylate (15 mol%), n-butyl acrylate (5 mol%)-Polyester component / acrylic resin component molar ratio = 3/7 (2) Cellulose derivative Methyl cellulose 20 wt% (3) Acrylic Resin fine particles (average particle size 50 nm) 10% by weight (4) Surfactant, NOF Nonionic NS-208.5 10% by weight Surface roughness (after drying) Ra; 8.5 nm Rz; 72 nm Supplied, stretched laterally 4.9 times at 150 ° C, then further stretched 1.14 times at 200 ° C. Conducted while to obtain a coating film which is biaxially oriented in the thickness 4.3 [mu] m. The binder resin is dried and polymerized by the heat applied during the transverse stretching and the heat treatment, and the Ra of the surface of the obtained coating layer B is 8.
5 nm and Rz were 72 nm.

A cobalt-oxygen thin film having a thickness of 110 nm was formed on the surface of the coating layer A of this coating film by vacuum vapor deposition, and then diamond-like carbon was formed at a thickness of 10 nm on the cobalt-oxygen thin film layer by a sputtering method. It was Further, a back coat layer made of carbon black, polyurethane, and silicone was provided on the surface of the coating layer B so as to have a thickness of 500 nm, slit by slitter to have a width of 8 mm, and wound on a reel to prepare a magnetic tape. The properties of the obtained polyester film and magnetic tape are shown in Table 1.

[Example 2] In Example 1, the coating layer A was used.
The same operation was repeated except that the composition was changed as shown in Table 1. The properties of the obtained coating film and magnetic tape are shown in Table 1.

Example 3 Dimethyl terephthalate and ethylene glycol were added, manganese acetate was used as a transesterification catalyst, antimony trioxide was used as a polymerization catalyst, and phosphorous acid was added as a stabilizer. Polyethylene terephthalate (P containing no inert particles)
ET, intrinsic viscosity 0.60) was obtained.

170% of this polyethylene terephthalate
After being dried at ℃ for 3 hours, it is fed to an extruder and melted at a temperature of 280-280
It was melted at 300 ° C., extruded into a sheet from a die, and rapidly cooled to obtain an unstretched film having a thickness of 82 μm.

The obtained unstretched film was preheated, further stretched 3.2 times in the machine direction at a film temperature of 95 ° C. between low-speed / high-speed rolls, and then rapidly cooled, and then one side of the machine-stretched film was longitudinally stretched. The coating layer of the coating layer A shown in Table 1 was provided on the other surface with the coating layer of the same coating layer B as in Example 1, and subsequently supplied to a stenter and stretched 4.1 times in the transverse direction at 110 ° C. did.
The obtained biaxially stretched film was heat set with hot air at 220 ° C. for 4 seconds to obtain a coating film having a thickness of 6.4 μm. The coating film thus obtained was subjected to the same operations as in Example 1 to obtain a magnetic tape. The properties of the obtained coating film and magnetic tape are shown in Table 1.

Example 4 The polyester film of Example 1 was prepared by adding the polyethylene-2,6-naphthalenedicarboxylate to polyethylene-2,6-naphthalenedicarboxylate containing substantially no inert particles. An inactive particle-containing polyethylene-2,6-naphthalene dicarboxylate polymer containing 0.18% by weight of silica having an average particle diameter of 220 nm is prepared, and the ratio of these polymers is 2: 1 in terms of thickness. Change to the laminated polyester film obtained by coextrusion in the laminated state,
The same operation as in Example 1 was repeated except that the coating layer of the coating layer A shown in Table 1 was formed on the surface layer made of polyethylene-2,6-naphthalenedicarboxylate containing no inert particles. The properties of the obtained coating film and magnetic tape are shown in Table 1.

[Examples 5 and 6] The same operation as in Example 1 was repeated except that the kind of the surfactant was changed as shown in Table 1. The properties of the obtained coating film and magnetic tape are shown in Table 1.

[Comparative Examples 1 to 9] A coating film and a coating film thereof were used by repeating the same operations as in Example 1 except that the composition of the coating layer A was changed to the content shown in Table 1. I got a magnetic tape. The properties of the obtained coating film and magnetic tape are shown in Table 1.

[0067]

[Table 1]

Here, in Table 1, PEN is polyethylene-2,6-naphthalenedicarboxylate, PET is polyethylene terephthalate, and the kind of the binder (A) is acrylic-polyester resin (polyester component: terephthalic acid (70 mol%)). ), Isophthalic acid (18 mol%), 5-sodium sulfoisophthalic acid (12 mol%) / ethylene glycol (92 mol%), diethylene glycol (8 mol%), acrylic resin component: methyl methacrylate (80 mol%), glue Sidyl methacrylate (15 mol%), n-butyl acrylate (5 mol%), polyester component / acrylic resin component weight ratio:
5/5), the kind of the binder (B) is polyester resin (terephthalic acid (95 mol%), 5-sodium sulfoisophthalic acid (5 mol%) / ethylene glycol (80
Mol%), diethylene glycol (20 mol%)), and the binder type (C) is an acrylic resin (methyl methacrylate (65 mol%), ethyl acrylate (28),
2-polyhydroxyethyl methacrylate (2 mol%),
n-methacrylic acid (5 mol%)), the type of surfactant (a) is Octapole 80 (HLB = 1, manufactured by Sanyo Kasei).
2.4), the type of surfactant (b) is Sanyo Kasei Nonipol Soft SS70 (HLB = 12.8), and the type of surfactant (c) is Sanyo Kasei Nonipol 100.
(HLB = 13.3), type of surfactant (d) is Sanyo Kasei Nonipol 200 (HLB = 16.0), type of surfactant (e) is Sanyo Kasei Emulmin 50
(HLB = 9.0), type of surfactant (f) is Sanyo Kasei Emarumin 180 (HLB = 15.1), type of surfactant (g) is Sanyo Kasei Octopole 400
(HLB = 17.9), the type (h) of the surfactant is NOF NS240 (HLB = 17.8) manufactured by NOF CORPORATION,
The type of surfactant (i) is Nonipol 70 manufactured by Sanyo Kasei.
0 (HLB = 18.7), the type (j) of the surfactant is Dodecapol 120 (HLB = 13.3) manufactured by Sanyo Kasei.
4).

As is clear from Table 1, the coating film for a magnetic recording medium according to the present invention is excellent in flatness and blocking resistance during roll winding, and has dropout characteristics and running durability when used as a magnetic recording medium. Excellent in. On the other hand, those which do not satisfy the requirements of the present invention cannot satisfy these characteristics at the same time.

[0070]

According to the present invention, a coating film having excellent blocking resistance and useful as a base film for a high recording density magnetic recording medium can be provided.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Hirofumi Murooka             3-37-19 Oyama, Sagamihara City, Kanagawa Prefecture             People DuPont Films Co., Ltd. Sagamihara Research Center             In the center F term (reference) 4F100 AJ06C AK01B AK25 AK41A                       AK42A AR00D BA02 BA03                       BA05 BA07 BA10A BA10B                       BA10C BA10D BA10E CA18B                       CA18C CA23B CC00E DD07B                       DE01B GB41 JG06D JK15                       JL00 YY00B YY00C                 5D006 BB01 CB01 CB07 CB08 EA03

Claims (10)

[Claims] 1. A laminated film in which a coating layer A is laminated on one surface of a polyester film, the coating layer A comprising:
The surfactant A is composed of a binder resin A, inert particles A and a surfactant A. The surfactant A is a first surfactant A having an HLB value of 10 or more and 14 or less and a second surfactant A having an HLB value of 16 or more and 20 or less.
It is composed of a surfactant A, and the content of the first surfactant A is 0.5% by weight or more based on the weight of the coating layer A. 15
A coating film for a magnetic recording medium, wherein the content of the second surfactant A is 1% by weight or more and less than 10% by weight or less. 2. The average particle diameter of the inert particles A is 3 nm or more and 5
The coating film for a magnetic recording medium according to claim 1, which has a thickness of 0 nm or less. 3. The surface of the coating layer A which is not in contact with the polyester film has a frequency of protrusions by the inert particles A of 10 or less.
The coating film for a magnetic recording medium according to claim 1, wherein the coating film has a number of from 0,000 pieces / mm ^{2 to} 30 million pieces / mm ² . 4. The surface of the coating layer A not in contact with the polyester film has a root mean square roughness (Ra) by AFM of 0.1 nm or more and 3 nm or less and a 10-point mean roughness (Rz) of 10 nm or more and 50 nm or less. A coating film for a magnetic recording medium according to claim 1. 5. A coating layer B is laminated on the other surface of the polyester film, and the coating layer B is a cellulose derivative B.
5. The coating film for a magnetic recording medium according to claim 1, which contains 5% by weight or more and 50% by weight or less and Surfactant B by 20% by weight or less. 6. The polyester film is a film made of polyethylene terephthalate or polyethylene-2,6-naphthalene dicarboxylate.
A coating film for a magnetic recording medium as described above. 7. The coating film for a magnetic recording medium according to claim 1, having a thickness of 2 μm or more and less than 7 μm. 8. The coating film for a magnetic recording medium according to claim 1, which is used for a digital recording type magnetic tape. 9. A coating film for a magnetic recording medium according to claim 1, and a magnetic layer formed on the surface on which the coating layer A is formed and a surface on which the coating layer A is not formed. A magnetic recording medium comprising a formed back coat layer. 10. The magnetic recording medium according to claim 9, wherein the magnetic layer is a ferromagnetic metal thin film layer.