JPH05135345A - Metal thin film type magnetic recording medium - Google Patents

Abstract

PURPOSE:To provide a magnetic recording medium excellent in rust preventing property and durability by applying a coating agent consisting of high molecular compd. containing phosphate group on a high molecular base substance of a magnetic recording medium provided with metal thin film magnetic body layer on a high molecular base substance. CONSTITUTION:Various kinds of films such as polyester or polyamid are used as a high molecular base substance, by the polyester film is preferable from the stand-point of price and performances. Metal thin film magnetic layer is provided on this high molecular base substance, and a coating agent consisting of high molecular compd. containing phosphate group is applied on the high molecular base substance. Thus, metal thin film type magnetic recording medium excellent both in rust preventing property and durability and, also, excellent in easily sliding property, smoothness, easily adhesive ability, resistance to guiding, traveling property, electromagnetic conversion characteristics is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a metal thin film type magnetic recording medium, and more specifically to rust prevention, slipperiness, smoothness, easy adhesion, transparency, abrasion resistance, running property and durability. The present invention relates to an excellent metal thin film magnetic recording medium.

[0002]

2. Description of the Related Art In recent years, magnetic recording media have been required to have high-density information recording in accordance with the reduction in size and weight or recording for a long time. In order to achieve high-density recording, it is necessary to shorten the recording wavelength and to reduce the spacing loss between the magnetic recording medium and the magnetic head as much as possible, and with this, the surface of the magnetic recording medium becomes smoother. Is desired. Among them, a metal thin film type magnetic recording medium obtained by forming a ferromagnetic thin film on a base film by a method such as vacuum deposition, sputtering and ion plating has a magnetic layer thickness larger than that of a conventional coating type magnetic recording medium. Since the thickness can be reduced to about 1/30 or less, the thickness loss due to the shortening of the recording wavelength can be reduced, and the surface of the magnetic recording medium can be made smoother by using a smooth base film. In addition, the spacing loss between the magnetic heads can be reduced, which is extremely effective for high density recording.

Research and development of such a ferromagnetic metal thin film type magnetic recording medium has been active, but a ferromagnetic metal thin film made of cobalt, nickel or a mixture thereof has a drawback that it is easily rusted. If the ferromagnetic metal thin film rusts, it will cause a serious deterioration of the electrical and magnetic properties of the magnetic recording medium. Regarding the rust prevention of the ferromagnetic metal thin film, for example, JP-A-53-88704 discloses a method of applying a surfactant to a metal magnetic layer, and JP-A-57-186230 discloses a silane coupling on the surface of a magnetic layer. Japanese Patent Application Laid-Open No. 57-191831 discloses a method of applying a perfluoroalkylcarboxylic acid salt to the surface of the magnetic layer, and a method of providing a film made of a hydrolyzate of the agent. It is also known to use a material for trapping corrosive gas in a tape cassette case.

[0004]

However, the above-mentioned conventional metal thin film type magnetic recording medium has the following problems. That is, JP-A-53-88704 and JP-A-5-
The method of coating a surface of a metal magnetic layer with a surfactant disclosed in JP-A-7-191831 has a problem in the persistence of the rust preventive effect, and as disclosed in JP-A-57-186230. The method of providing a film made of a hydrolyzate of a silane coupling agent on the surface has a problem in durability of the film layer. Further, the method of using a material that traps corrosive gas in the tape cassette case has no effect on the rust prevention of the magnetic layer due to water absorption.

The present invention eliminates these drawbacks of the prior art, and is excellent in both rust prevention effect and durability, and at the same time, in slipperiness, smoothness, easy adhesion, abrasion resistance, running property and electromagnetic conversion characteristics. Another object is to provide an excellent metal thin film type magnetic recording medium.

[0006]

A metal thin film type magnetic recording medium of the present invention which meets this object is a magnetic recording medium comprising a polymer thin film magnetic layer provided on a polymer substrate. It is formed by applying a coating agent containing a phosphate group-containing polymer.

Typical examples of the polymer base material in the present invention include, but are not limited to, various films such as polyester, polyamide, polyimide and polyamideimide. However, polyester film is particularly preferable in terms of cost and performance.

The term "polyester" as used herein is a general term for polymers having an ester bond as the main chain of the main chain.
Particularly preferred polyesters include polyethylene terephthalate, polyethylene 2,6-naphthalate, polybutylene terephthalate, polyethylene α, β-bis (2-chlorophenoxy) ethane 4,4-dicarboxylate and the like. Of these, polyethylene terephthalate is most preferable in consideration of quality, economy and the like. Therefore, polyethylene terephthalate (hereinafter abbreviated as PET) will be described below as a typical example of polyester.

PET is 80 mol% or more, preferably 9
Although 5 mol% or more contains ethylene phthalate as a repeating unit, other dicarboxylic acid components and diol components may be used within this limited amount range. Further, known additives such as heat resistance stabilizer, oxidation resistance stabilizer, weather resistance stabilizer, ultraviolet absorber, organic lubricant, pigment, dye, organic or inorganic fine particles, filler, antistatic agent, You may mix | blend a nucleating agent etc. The PET film has an intrinsic viscosity of 0.4 (measured in orthochlorophenol at 25 ° C.).
0 to 1.20 dl / g, preferably 0.50 to 0.80 d
Those in the l / g range are suitable for the context of the present invention. The polyester film in the present invention is preferably biaxially oriented in view of mechanical and thermal characteristics. For example, when the above PET is used as polyester, the biaxially oriented PET film is a non-stretched P film.
ET sheet or film in the longitudinal direction and the width direction,
Each is made by stretching about 2.5 to 5 times,
Wide angle X-ray diffraction indicates a biaxially oriented pattern.
Although the thickness of the PET film is not particularly limited, it is usually preferably in the range of 1 to 500 μm, and 5 to 100.
The range of μm is more preferable.

The phosphoric acid group-containing polymer referred to in the present invention is not particularly limited as long as it is a polymer having a phosphoric acid group in the molecule, but from the viewpoint of projection forming ability and rust preventive effect, 1
A compound having a phosphoric acid group or a phosphoric acid ester group ethylenically unsaturated bond in the molecule, for example, acid phosphooxyethyl methacrylate, 3-chloro-2 acid phosphoxypropyl methacrylate, acid phosphoxypropyl methacrylate. Rate, acid phosphoxyethyl acrylate, methacryloyloxyethyl acid phosphate monoethanolamine half salt, metacloyloxyethyl acid phosphate dimethylaminoethyl methacrylate half salt, methacroyloxyethyl Acid phosphite diethylaminoethyl methacrylate half salt, acid phosphooxypolyoxyethylene glycol monomethacrylate, acid phosphooxypolypropylene glycol monomethacrylate, etc. It can be. Among these compounds, a halogen-containing compound and a long-chain compound are particularly preferable in order to bring out the effect of the present invention more remarkably. The above compounds may be used alone or in combination with other compounds having an ethylenically unsaturated bond.

As the other compound having an ethylenically unsaturated bond which is copolymerized with the compound having an ethylenically unsaturated bond and the phosphoric acid group or the phosphoric acid ester group, there are alkyl acrylate and alkyl methacrylate. (As the alkyl group, 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, phenyl group, benzyl group. Group etc.)
Further, compounds having a functional group such as a reactive functional group, a self-crosslinking functional group, a hydrophilic group can be used. As the functional group, a carboxyl group and / or a salt thereof, an acid anhydride group, a sulfonic acid group and / or a salt thereof,
Examples thereof include an amide group or an alkyl group-based amide group, an amino group (including a substituted amino group), an alkylated amino group and / or a salt thereof, a hydroxyl group, an epoxy group and the like.

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

Examples of the compound having a sulfonic acid group and / or a salt thereof include vinyl sulfonic acid, styrene sulfonic acid, alkali metal salts and ammonium salts thereof. Examples of the compound having an amide group or an alkylated amide group include acrylamide, methacrylamide, N-methylmethacrylamide, methylol acrylamide, methylol methacrylamide, ureido vinyl ether, β-ureidoisobutyl. Examples thereof include vinyl ether and ureidoethyl acrylate.

The compound having an amino group or an alkylated amino group and / or a salt thereof is diethylaminoethyl vinyl ether, 2-aminoethyl vinyl ether, 3-aminopropyl vinyl ether,
2-Aminobutyl vinyl ether, dimethylaminoethyl methacrylate, dimethylamino vinyl ether, and those obtained by methylating their amino groups, quaternary chlorination with alkyl halides, dimethylsulfate, sultone, etc. The ones that have been done are listed. As the compound having a hydroxyl group, β-hydroxyethyl acrylate, β-hydroxymethacrylate, β-hydroxypropyl acrylate, β-hydroxypropyl methacrylate, β
-Hydroxyvinyl ether, 5-hydroxypentyl vinyl ether, 6-hydroxyhexyl vinyl ether, polyethylene glycol monoacrylate, polyethylene glycol monomethacrylate, polypropylene glycol monoacrylate, polypropylene glyco −
Examples thereof include rumonomethacrylate. Examples of the compound having an epoxy group include glycidyl acrylate and glycidyl methacrylate. 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, itaconic acid mono- or dialkyl ester,
Methyl vinyl ketone, vinyl chloride, vinylidene chloride, vinyl acetate, vinyl pyridine, vinyl pyrrolidone, vinyl trisalkoxy silane, etc., but are not limited to these. These compounds may be copolymerized alone, or may be copolymerized with two or more kinds.

The phosphate group-containing polymer of the present invention is a polymer which can be dissolved or dispersed in water, and such a copolymer is a copolymer with a monomer having a hydrophilic group (acrylic acid, methacrylic acid, acrylamide, etc.). It can be made by polymerization. For example, isopropyl alcohol is charged with a compound having the above-mentioned phosphoric acid group or phosphoric acid ester group and an ethylenically unsaturated bond, methyl methacrylate, butyl acrylate, and acrylic acid, and an appropriate amount of a polymerization initiator (for example, benzoylperoxide). The above-mentioned peroxide) is added and the polymerization is advanced under heating to prepare a quaternary copolymer. Next, aqueous ammonia is added to ammonify the carboxyl groups of acrylic acid. Then, it can be obtained by adding water and removing the alcohol content at a temperature not higher than the boiling point of water and not lower than the boiling point of isopropyl alcohol. Of course, the method is not limited to this, and any method can be adopted.

The compound (a) having a phosphoric acid group or a phosphoric acid ester group and an ethylenically unsaturated bond and the compound (b) having another ethylenically unsaturated bond are copolymerized at an arbitrary ratio. (A) / (b) is a weight ratio of 3/97 to 99/1, preferably 5/95 to 95/5, and more preferably 10/90 to
It is preferably 85/15. The phosphate group-containing polymer has an average particle size of 0.01 to 1 μmφ, preferably 0.01 to
It is more preferable for the smoothness of the protrusions to be in the range of 0.5 μmφ and have a uniform particle size distribution.

The phosphoric acid group-containing polymer of the present invention may be blended with another polymer at an arbitrary ratio and applied on a polymer substrate. Other polymers are not particularly limited, but rust preventive effect, projection forming ability, slipperiness, transparency, abrasion resistance and the like crosslinkable polymer, among which self-crosslinking acrylic copolymer is preferable. Used. In the present invention, the essence is to apply the above-mentioned aqueous coating solution, dry it, stretch it in at least one direction, and heat-treat it at high temperature. Also,
Other substances such as a surfactant may be appropriately added as long as the effects of the present invention are not impaired.

In the present invention, such protrusions are provided on at least one side of the polyester film. However, in the case where they are provided on both sides, the description of the nucleus-free protrusions described below applies to at least one side. is there. The cause of rust in the cobalt / nickel magnetic layer, which is most often used as a ferromagnetic thin film metal in magnetic recording media, is
It is considered to be the formation of cobalt hydroxide by water and oxygen gas, and the rust preventive mechanism of these magnetic layers of the phosphoric acid group-containing polymer of the present invention is not fully understood, but the phosphoric acid group is chelated. It is understood that cobalt hydroxide does not easily form because it acts as an agent and inhibits the ionization of metals such as cobalt.

In the present invention, the acrylic resin which may be blended with the phosphoric acid group-containing polymer in an arbitrary ratio means a functional group-containing vinyl polymerizable monomer, a hydrocarbon type vinyl polymerizable monomer and a hydrocarbon type non-polymerizable monomer. A copolymer compound such as a conjugated divinyl polymerizable monomer may be mentioned. In the present invention, a copolymer of a functional group-containing vinyl polymerizable monomer is preferably used.

As the functional group-containing vinyl polymerizable monomer,
For example, acrylic acid, methacrylic acid, acrylamide, methacrylamide, N-methyl acrylamide, N-
Butoxymethyl acrylamide, diacetone acrylamide, methyl diacetone acrylamide, 2-
Hydroxyethylmethacrylate, 2-hydroxyethyl acrylate, hydroxypropyl acrylate, 3-
Chloro-2-hydroxypropyl methacrylate and the like can be mentioned, and they are selected from these, but are not particularly limited. The average particle size of the water-dispersible self-crosslinking acrylic copolymer is 0.01 to 1 μmφ, preferably 0.0.
1 to 0.5 μmφ, more preferably 0.01 to 0.1
It is more preferable for the smoothness of the protrusions to be in the range of μmφ and have a uniform particle size distribution. Further, from the viewpoint of abrasion resistance and the like, it is preferable that the projections of the present invention do not contain inorganic particles, organic particles, inorganic colloids or the like, but a small amount may be added as long as the characteristics of the film of the present invention are not impaired. It doesn't matter. In that case, the addition amount of the particles is 10
The amount is preferably 10 parts by weight or less, more preferably 5 parts by weight or less, relative to 0 parts by weight. In addition, within a range not impairing the effects of the present invention, in order to improve the flatness and slipperiness of the protrusions, methyl self-crosslinking acrylic copolymer is added to methylcellulose.
Cellulose-based polymers such as cellulose and ethyl cellulose may be added. The addition amount is 5 with respect to the solid content of acrylic resin.
The range of -30%, preferably 10-20% is preferable.
If the amount of cellulose added exceeds 30%, the smoothness of the protrusions is deteriorated, which is not preferable. On the other hand, the addition amount is 5
If it is less than%, the effect of improving the smoothness and the slipperiness is not sufficient, which is not preferable.

In the present invention, it is preferable to form the protrusions only with the phosphate group-containing polymer and the self-crosslinking polymer in order not to impair the smoothness of the protrusions, the particle morphology, etc., but the effects of the present invention are impaired. If the amount is within the range, the projection may contain a cross-linking agent in order to improve the adhesion and mechanical strength. The cross-linking agent in the present invention, a functional group present in the acrylic copolymer, for example, a cross-linking reaction with a hydroxyl group, a carboxyl group, a glycidyl group, an amide group, etc., finally a nucleus having a three-dimensional network structure It is not particularly limited as long as it is a cross-linking agent for forming no protrusions,
Representative examples thereof include methylolated or alkylated urea-based, melamine-based, acrylamide-based, polyamide-based resins, epoxy compounds, isocyanate compounds, and aziridine compounds. Of these, methylolated melamine and isocyanate compounds are preferable from the viewpoints of adhesion to the base film and mechanical strength. These cross-linking agents may be used alone or in combination of two or more depending on the case. The amount of the cross-linking agent to be added is appropriately selected depending on the kind of the cross-linking agent, but the resin solid content is usually 100.
0.01 to 50 parts by weight is preferable, and 0.1 to 0.1 part by weight.
-30 parts by weight is more preferred. If the addition amount is less than 0.01 part by weight, the crosslinking effect is low, and if it exceeds 50 parts by weight, the adhesion of the projections is lowered, and further the coating property is deteriorated, and it is difficult to form a uniform layer. A crosslinking catalyst may be used in combination with the crosslinking binder. As the cross-linking catalyst, known ones such as salts, inorganic substances, organic substances, acid substances and alkaline substances can be used. The amount of cross-linking catalyst added is 100% resin solids.
0.001-10 parts by weight, preferably,
It is 0.1 to 5 parts by weight. The coating agent to which a crosslinking agent has been added is crosslinked by heating, ultraviolet rays, electron beams or the like after being applied to the substrate film, but a method by heating is generally used.

The protrusion in the present invention is made of a granular acrylic copolymer formed on the surface of the base polyester film, and the crosslinkable acrylic copolymer is adhered to the base polyester film by heat melting or heat softening. , The base polyester film is adhered to the base polyester film by adhesion or the like. The polyester film, which is the base film constituting the film of the present invention, may be uniaxially oriented, but is preferably biaxially oriented in terms of mechanical strength, dimensional stability, rigidity and the like. The thickness of the polyester film is not particularly limited, but 1 to 500
μm is preferable, and a range of 3 to 80 μm is more preferable,
Excellent handleability in terms of practical use as a base film. The surface roughness (Ra) and optical haze of the polyester film are not particularly limited, but the surface roughness (Ra) is 0.02 μm or less, preferably 0.01 μm.
It is preferably m or less. The protrusions forming the film of the present invention have a laminated thickness including the protrusions of 0.001 to 0.5 μ.
m is preferable, and the range of 0.005-0.25 μm is more preferable. If the layer thickness is less than 0.001, it is difficult to obtain a uniform layer, and it is difficult to obtain easily slippery protrusions. 0.5μ
If it exceeds m, the projections have a film-forming property, and it becomes difficult to form the projections, which is not preferable.

In addition, the above-mentioned protrusions have an epoxy compound as an adhesion promoter with the base polyester film or the magnetic layer,
A reactive compound such as an aziridine compound or a vinyl compound, a silane coupling agent, or the like may be contained. Further, if necessary, known additives in an amount that does not impair the effects of the present invention, for example, coatability improver, antistatic agent, antioxidant, ultraviolet absorber, rust preventive agent, dye, defoaming agent, You may make it contain a thickener etc. Further, the number of surface protrusions per unit area must be 1 × 10 ⁵ pieces / mm ² or more, preferably 1 × 10 ⁶ pieces / mm ² or more, more preferably 1 × 10 ⁷ pieces / mm ² or more. Is. When it is more than this value, the slipperiness on the forming surface becomes sufficient when the ferromagnetic thin film is formed, and the electromagnetic conversion characteristics become better.
Further, the film of the present invention, after the projections are oriented in one direction,
Furthermore, it is desirable that the film be stretched in the same direction (re-transverse stretching) to strengthen the orientation and then heat treated.
It is desirable that the projections can be made more uniform and finer by the heat treatment.

Next, a method of manufacturing the magnetic recording medium of the present invention will be described, but the method is not limited to this. First, polyester pellets polymerized by a conventional method are sufficiently dried, and then a known extruder, preferably a compression ratio of 3.
It is supplied to 8 or more melt extruders, melt-extruded in a sheet form from a slit die at a temperature not lower than the temperature at which pellets melt but not higher than the temperature at which polymers decompose, and then cooled and solidified to form an unstretched sheet. .. At this time, the intrinsic viscosity of the unstretched sheet is preferably 0.5 or more in view of film characteristics. Next, the unstretched sheet is 2.0 to 5.0 at 70 to 120 ° C.
A coating material prepared by coating the above composition in a predetermined amount is applied on a double-stretched film, and the coating film is dried to form a predetermined coating layer. Stretch. Further, if necessary, transverse stretching may be performed again. Further, the biaxially oriented film is heat-treated at 150 to 250 ° C. for 1 to 60 seconds while giving 0 to 10% relaxation. The coating method is not particularly limited and may be an extrusion lamination method or a melt coating method, but a gravure coating of a water-dispersed coating material is possible because a thin film coating can be performed at high speed. It is preferable to apply a known method such as a coating method, a reverse coating method, a kiss coating method, a die coating method or a metalling coating method. At this time, prior to coating, a known surface treatment such as corona discharge treatment in air or other various atmospheres may be performed on the film, if necessary, to improve not only the coating property but also the protrusions. It can be more firmly formed on the film surface. The coating material concentration and the coating film drying conditions are not particularly limited, but it is preferable that the coating film drying conditions be performed within a range that does not adversely affect various properties of the polyester film. In order to obtain the protrusion of the present invention, the coating amount is 0.00
03-0.05 g / m < ² >, preferably 0.0015-0.
026 g / m ² , more preferably 0.003 to 0.00
The range of 7 g / m ² (dry) is desirable. In the coating amount is 0.0003 g / m ² or less can not be imparted to less sufficient lubricity number projections, projections now have film-forming properties in the 0.05 g / m ² or more, the formation of projections Is difficult to do, which is not preferable. The laminated polyester of the present invention can be produced as described above, and the ferromagnetic thin film type magnetic recording medium can be produced by providing the ferromagnetic thin film layer on the projection forming surface of the laminated polyester.

Here, the ferromagnetic thin film is a ferromagnetic metal such as iron, cobalt or nickel, or Co-N.
i, Fe-Co, Fe-Ni, Fe-Rh, Fe-C
u, Fe-Au, Co-Cu, Co-Au, Co-Y,
Co-La, Co-Pr, Co-Gd, Co-Sn, C
o-Pt, Ni-Cu, Fe-Co-Nd, Mn-B
A magnetic alloy such as i, Mn-Sn, Mn-Al is formed on a film by a vacuum deposition method, an ion plating method, a sputtering method, an ion beam deposition method, an electrolytic deposition method, an electrolytic plating method, or the like. .. The ferromagnetic thin film applied to the magnetic recording medium of the present invention may be of course manufactured by any of the above-mentioned methods, but the vapor deposition direction is inclined in the longitudinal direction (90 ° to 30 °).
However, it is not inclined in the width direction, and the atmosphere is O ²
Alternatively, a material vapor-deposited at 1 × 10 ⁻⁴ Torr while introducing O ² and Ar is preferably used. The thickness of the ferromagnetic thin film is usually 0.01-1 μm, preferably 0.05-0.
3 μm is used.

[0026]

According to the metal thin film type magnetic recording medium of the present invention, the following excellent effects can be obtained. First of all, since the coating material consisting of the phosphate group-containing polymer was applied on the polymer substrate, the anticorrosion ability of the magnetic layer of the metal thin film provided on it can be greatly improved, and the magnetic layer with excellent anticorrosion effect can be obtained. It can be a recording medium.

Further, since the projections can be formed on the polymer base material by the above coating agent itself, a metal thin film type magnetic recording medium excellent in slipperiness, abrasion resistance, running property and electromagnetic conversion characteristics can be obtained. ..

[Measuring Method and Evaluation Method] The measuring method of the characteristic and the evaluating method of the effect in the present invention are as follows. (1) Anticorrosive property The coating material of the present invention was applied on a PET substrate, dried and heat treated, and then a metal material composition of Co / Ni = 80/20 was introduced while oxygen was introduced at a rate of 0.2 L / min. Oblique vapor deposition was performed to a thickness of 2 μm. After spin coating an anticorrosive agent on the surface of the magnetic layer of the obtained sample, 60 ° C, 90% R
The magnetic layer was left to stand under an atmosphere of H and the saturation magnetization of the magnetic layer was adjusted to V. S. MAGNETMETER (Model B
HV-3,5) and XY plotter (model F-42)
CP) was used for measurement and evaluation. The decay rate was calculated from the saturation magnetization over time. The occurrence of pitting corrosion on the surface of the magnetic layer was observed and evaluated with a microscope. The evaluation criteria are as shown in Table 1.

[0029]

[Table 1]

(2) Coating layer thickness Using a transmission electron microscope HU-12 manufactured by Hitachi Ltd., an ultrathin section of the laminated film is observed to determine the thickness.

(3) Surface Roughness (Ra) According to JIS-B-0601, a cut-off of 0.0 was used using a stylus type surface roughness meter BE-3E manufactured by Kosaka Laboratory Ltd.
The average surface roughness Ra (μm) was measured at 25 mm and a measurement length of 4 mm.

(4) Smoothness (Static friction coefficient μs, dynamic friction coefficient μk) The friction coefficient between films is ASTM-D-1894.
According to 63, the static friction coefficient μs was measured. Generally, the range of excellent slipperiness is 1.6 or less, preferably 1.2 or less in μs. The dynamic friction coefficient μk between the film and the metal post is measured using a dynamic friction coefficient device (TBT-300, manufactured by Yokohama System Research Institute) at 25 ° C. and 50% relative humidity in a coating surface or a ferromagnetic thin film forming surface. SUS420J2 with an outer diameter of 8mm2, surface roughness 0.2S
Contact the post with a wrap angle of 180 ° and 3.3 cm / s
After moving at a speed of ec, the tension is controlled so that the inlet tension T1 becomes 25 g, and the dynamic friction coefficient .mu.k is calculated from the value (g) of the outlet tension T2 by the following equation. μk = (2.303 / π) log (T2 / T1) = 0.733log (T2 / T1)

(5) Easy-adhesion property Belger-type high-vacuum deposition device (E manufactured by Nippon Vacuum Technology Co., Ltd.)
(BH-6 type) with a vacuum degree of about 1 × 10 ^-5 mmHg, a commercially available cellophane adhesive tape manufactured by Nichiban Co., Ltd. is attached to the aluminum vapor deposition surface, and a load of about 5 Kg is applied using a hand roller. After the pressure bonding, the surface on which the aluminum remained adhered after being forcibly peeled in the 180 ° direction was evaluated. The criteria for evaluation judgment are
90% or more of the remaining deposition area of the aluminum vapor deposition film layer was evaluated as good (∘), 75 to 90% as slightly inferior (Δ), and less than 75% as poor (x). The larger the remaining adhered area, the better the adhesiveness.

(6) Number of granular protrusions, SEM (scanning electron microscope, manufactured by Akashi Seisakusho Co., Ltd., DS
-130 type), magnification 10,000-30,000 times, angle 80
The number of the granular projections was counted by taking a photograph at ° and the number of projections per piece / mm ^{2 was} calculated by converting the area. Also,
Non-contact three-dimensional fine shape measuring instrument ET made by Kosaka Laboratory Ltd.
The protrusion height, average roughness and the like were measured using a -30HK type.

(7) Thickness of magnetic layer In the case of a magnetic layer formed by vacuum deposition, sputtering or the like. Fluorescent X-ray micrometer film thickness meter STF-15 manufactured by Daini Seikosha
6 was used for measurement.

(8) Runnability Coefficient of dynamic friction μ between the film and the metal post of the above (4)
In the same manner as in k, the initial μk of the base material of the base material after repeated running 300 times is measured. Next, in a magnetic recording medium in which a lubricant is not applied to the surface after forming the ferromagnetic thin film,
In a magnetic recording medium coated with a lubricant on the surface after forming a ferromagnetic thin film after repeating 0 times, one having a μk value after repeating 300 times smaller than a value increased by 25% of the initial μk value (running Good running), and other than that (running poor).

(9) Electromagnetic conversion characteristics When the output signal when the sample magnetic recording medium is reproduced is viewed on one screen, the output signal is strong and the signal waveform is flat (good), the output signal Weakness or deformation of the signal waveform was judged as (defective).

(10) Scraping resistance A laminated polyester film is 25 to 30 cm in length and 1 in width.
When sampled at 1/2 inch, the laser blade was applied to the coating layer surface at an angle of 90 ° and a depth of 0.5 mm, and was run at a load of 500 g / 0.5 inch and a speed of 6.7 m / sec. The width of the scraped powder adhering to the laser blade in the depth direction was determined by taking a photomicrograph (× 160). The width of the shavings in the depth direction was 3 μm or less (◯), 3 to 5 μm was (Δ), and 5 μm or more was (X). It goes without saying that the smaller the adhesion depth of the shavings, the better the shaving properties.

(11) Solution haze of chips To 20 ml of well-known polyethylene terephthalate solvent,
The chip 3g was melt | dissolved and it put in the quartz cell of thickness 20mm, and measured the solution haze.

[0040]

【Example】

Example 1 A homopolymer chip of polyethylene phthalate having a solution haze of 0.8% (intrinsic viscosity = 0.62) containing as little as possible internal particles and inactive particles based on a polymerization catalyst residue produced by a conventional method. , Melting point: 259 ° C.) to 180 ° C.
It was dried under reduced pressure (3 mmHg) for 2 hours. 280 ℃ this chip
To an extruder having a screw with a compression ratio of 3.8,
After filtering with a metal sintered filter of 10 μm cut, T
Melt extrude from die die and apply electrostatic force to the surface temperature 2
After winding around a 0 ° C. cooling drum to solidify by cooling to obtain an unstretched film, the obtained film was stretched 3.5 times in the longitudinal direction by roll stretching at 90 ° C., and the surface was subjected to corona discharge treatment. , Methyl methacrylate on the treated surface /
Butyl acrylate / acrylic acid / 3 chloro 2 acid phosphooxypropyl methacrylate (90/10/1
(5/15 weight ratio) quaternary copolymer aqueous solution (A) and methyl methacrylate / ethyl acrylate / acrylic acid /
A water-dispersible acrylic copolymer (manufactured by Nippon Carbide Industry Co., Ltd.) (B) consisting of N-methyl acrylamide (B) was set to 20/80 at a solid content ratio of (A) / (B) of 0.5. It was a water-based paint with a weight percentage.

This coating agent was applied to one side of the uniaxially stretched film by the metalling bar coating method, and then the coating layer was dried and stretched in the transverse direction by a factor of 3.6 at 100 ° C., and further 2 times.
After 5% re-stretching in the transverse direction at 00 ° C., heat treatment at 225 ° C. for 5 seconds while relaxing 2% in the transverse direction gives a coating amount of 0.015.
A laminated polyester film having a thickness of 10 μm in which g / m ² (dry) was laminated was obtained. The properties of this laminated polyester film are shown in Table 2. Then, a Co-Ni alloy (20% by weight of Ni) was obliquely vapor-deposited to a thickness of 200 nm on the film by an electron beam vapor deposition method. A perfluoropolyalkyl ether metal salt having trichlorotrifluoroethane dispersed therein was applied on the vapor-deposited surface of the vapor-deposited film at a solid content of about 30 mg / m ² and then slit to a 1/2 inch width to form a magnetic tape. Obtained. The results of evaluating the magnetic tape characteristics are shown in Table 3. Moreover, this magnetic tape is kept at 60 ° C, 90 ° C.
The degree of rust of the magnetic layer when left in an atmosphere of% RH was evaluated by observing the decay rate of saturation magnetization and the occurrence of pitting corrosion on the metal surface of the magnetic layer with a microscope. The results are also shown in Table 3.

Example 2 A laminated polyester film was obtained in the same manner as in Example 1 except that (A) / (B) was changed to 80/20 based on Example 1. Next, after oblique vapor deposition in the same manner as in Example 1,
A magnetic tape was obtained. The properties of the laminated polyester film and the magnetic tape are shown in Tables 2 and 3. Table 2 and Table 3
As can be seen from the above, when the laminated polyester film is within the range of the present invention, it is understood that a magnetic recording medium excellent in rust resistance, running durability and electromagnetic conversion characteristics can be obtained.

Example 3 Based on Example 1, the coating agent (A) component of Example 1 was 3chloro-2 acid phosphooxypropyl methacrylate.
A laminated polyester film and a magnetic tape were prepared in the same manner except that 2 acid phosphooxyethyl methacrylate was used in place of the film. Table 2 shows the characteristics of both
And shown in Table 3.

Comparative Example 1 Based on Example 1, methyl methacrylate / butyl acrylate / acrylic acid / 3chloro 2 acid phosphooxypropyl methacrylate (90/10/15/15)
(Weight ratio) quaternary copolymer aqueous solution (A) is not used at all,
Water-dispersible acrylic copolymer consisting of methyl methacrylate / ethyl acrylate / acrylic acid / N-methyl acrylamide (manufactured by Nippon Carbide Industry Co., Ltd.)
A coating material of 0.5% by weight was prepared using only (B) and applied to a substrate to obtain a laminated polyester film. Similarly Co / Ni
Diagonal vapor deposition was performed to prepare a magnetic tape and evaluated. The results are shown in Tables 2 and 3, but since the phosphate group-containing compound was not used, the magnetic layer was easily rusted.

Comparative Example 2 A polyethylene terephthalate homopolymer chip having an intrinsic viscosity of 0.65 dl / g and a melting point of 262 ° C., produced by a conventional method, was used as a main extruder and a particle size of 0.4 from the sub-extruder.
Intrinsic viscosity 0.62 containing 0.5% of wet silica of μm
A layer containing inorganic particles in the outer two layers by a composite method of a cap upper short tube having a structure in which three streams of polyethylene terephthalate having a dl / g and a melting point of 260 ° C. are supplied respectively and the three flows merge in the short tube. A layer containing no particles at the center of the slab was extruded into a sheet in a three-layer laminated state, wound around a cooling drum and rapidly cooled and solidified to obtain an unstretched three-layer laminated structure. This roll was stretched 3.5 times in the longitudinal direction at 95 ° C., then 3.5 times in the width direction at 105 ° C. in a tenter, and further subjected to a constant length heat treatment at 235 ° C. for 10 seconds in the same tenter. And both surface layers are 0.
A three-layer laminated film having a thickness of 2 μm and a total thickness of 10 μm was obtained. Since this three-layer laminated film was not coated with the coating liquid of the present invention, as shown in Tables 2 and 3, the magnetic layer was inferior in rust preventive effect and easy adhesion.

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[Table 2]

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[Table 3]

Claims (5)

[Claims] 1. A magnetic recording medium in which a magnetic material layer of a metal thin film is provided on a polymer base material, wherein a coating material comprising a phosphoric acid group-containing polymer is applied onto the polymer base material. Metal thin film magnetic recording medium. 2. The phosphate group-containing polymer is phosphite.
The metal thin film type magnetic recording medium according to claim 1, comprising a copolymer obtained by polymerizing tomonomers and acryl. 3. The metal thin film type magnetic recording medium according to claim 1, wherein a coating material in which an acrylic copolymer is mixed with the phosphoric acid group-containing polymer is applied. 4. The metal thin film type magnetic recording medium according to claim 1, wherein 1 × 10 ⁵ protrusions / mm ² or more of the coating material are formed on the polymer base material. 5. The metal thin film is made of Co, Ni or a mixture thereof.
2. The metal thin film magnetic recording medium according to any one of 1.