JPS629525A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve the adhesiveness to a magnetic layer and to improve durability, corrosion resistance and running property by providing a protective layer contg. a fluorine compd. having at least 1 isocyanate groups at the terminal of the molecule on the magnetic layer formed on a substrate. CONSTITUTION:The protective layer contg. the fluorine compd. having at least 1 isocyanate groups at the terminal of the molecule is provided on the magnetic layer formed on the substrate. The fluorine compd. is preferably obtd. by bringing a perfluoroalkyl polyether having a hydroxyl group or carboxyl group at one or both terminals of the molecule and isocyanate compd. such as diisocyanate compd. Since the isocyanate group at the terminal of the molecule binds with the hydroxyl group on the surface of the magnetic layer by reaction, the fluorine compd. is securely adsorbed via the isocyanate group to the surface of the magnetic layer. The skeletal part of the fluorine compd. has an excellent lubricating function and water repelleling function and contributes to the improvement of the durability, corrosion resistance and running property.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a magnetic recording medium, and more specifically:
The present invention relates to a magnetic recording medium that has good adhesion, excellent durability and corrosion resistance, and excellent running performance.

[Conventional technology]

In general, magnetic recording media are made by binding magnetic powder together with a binder component onto a base film, or by depositing ferromagnetic metals or their alloys on a base film by vacuum deposition, etc. The magnetic layer is easily worn out due to violent sliding contact with a magnetic head, etc., and in particular, ferromagnetic metal thin film magnetic recording media formed by vacuum deposition etc. and magnetic recording media made by bonding metal magnetic powder together with a binder component are susceptible to wear. Although it has excellent high-density recording characteristics,
It has a large coefficient of friction with the magnetic head, making it susceptible to wear and damage, and it also suffers from gradual oxidation in the air, deteriorating magnetic properties such as maximum magnetic flux density.

For this reason, fluorinated moisturizers such as tetrafluoroethylene telomer, perfluoroalkyl polyether, perfluoroalkyl polyether containing hydroxyl or carboxyl groups, fatty acids, fatty acid esters, aliphatic amines, fatty acids, etc. are used on the magnetic layer. A protective layer consisting of an aliphatic lubricant such as a group amide has been provided to improve durability and corrosion resistance. (Japanese Patent Publication No. 56-30609, Japanese Patent Publication No. 58-5763, Japanese Patent Application Publication No. 56-124127,
US Patent No. 377830, US Patent No. 4267238,
(U.S. Pat. No. 4,268,556, U.S. Pat. No. 3,490,946) [Problems to be Solved by the Invention] However, the fluorine-based lubricants and aliphatic lubricants that have been used conventionally have weak interaction with the surface of the magnetic layer. However, due to poor adhesion, it is easy to separate from the surface of the magnetic layer due to sliding contact with the magnetic head, and durability and corrosion resistance have not yet been sufficiently improved. In addition, aliphatic lubricants such as fatty acids, fatty acid esters, aliphatic amines, and aliphatic amides have insufficient lubrication effects and cannot sufficiently reduce the coefficient of friction, and are still insufficient in improving running performance. It's not satisfying.

[Means for solving problems]

This invention was made as a result of various studies in view of the current situation, and by providing on the magnetic layer a protective layer containing a fluorine compound having at least one isocyanate group at the end of the molecule, the magnetic layer can be It has improved adhesion to, durability and corrosion resistance, as well as sufficiently good running properties.

The fluorine compound used in this invention preferably has at least one isocyanate group at the end of the molecule, and when it has one or more isocyanate groups at the end of the molecule, this isocyanate Since the group reacts with and bonds with the hydroxyl group on the surface of the magnetic layer, the fluorine compound is firmly adsorbed to the surface of the magnetic layer via the isocyanate group. In addition, the part consisting of fluorocarbon that forms the skeleton of this type of fluorine compound has excellent lubricating and water- and oil-repellent functions, and this lubricating function and water- and oil-repellent function are sufficient on the surface of the protective layer. Therefore, the fluorine compound having at least one isocyanate group at the end of the molecule of rice seeds is firmly adhered to the surface of the magnetic layer, and the adhesion to the magnetic layer is sufficiently improved. A protective layer with excellent lubricity is formed, and the protective layer does not peel off due to sliding contact with the magnetic head, and durability, corrosion resistance, and runnability are sufficiently improved.

Such a fluorine compound having at least one isocyanate group at the end of the molecule can be prepared by reacting a perfluoroalkyl polyether having a hydroxyl group or a carboxyl group at one or both ends of the molecule with an isocyanate compound such as a diisocyanate compound. For example, perfluoroalkyl polyether (
However, in the general formula, n is an integer of 5 to 200, and m is an integer of 5 to 200. ) CF3- (CF2 )n (OCH2CH2)m
C00H (where n is an integer of 5 to 200, m is 5 to 2
It is an integer of 00. ) cnF2n+, CH2C00H cnF2. ,, CH2CH20H (however, n in the above general formula is an integer of 8 to 32), diphenylmethane-p,p-diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, 2.2.4- (2,4,4 -) Trimethylhexylylene diisocyanate, tolylene diisocyanate, 4,4'-methylene-bis-cyclohexyl isocyanate, xylylene diisocyanate, isovylidene-bis-4-cyclohexyl isocyanate, bis-2
-Isocyanate ethyl fumarate, bis-2-isocyanate ethyl carbonate, bis-2-isocyanate ethyl-4-cyclohexane-1°2-dicarboxylate, bis-2-isocyanate ethyl-1,4,5
,6,7,7-hexachloro-5-noporene-2.3
-dicarboxylate, tetramethylene diisocyanate, dimethyl-diphenylmethane-p,p'-diisocyanate, metaphenylene diisocyanate, naphthalene-1,5-diisocyanate, 3,3'-dimethyl-
Those obtained by reacting with a diisocyanate compound such as 4,4''-biphenylene diisocyanate are preferably used.

Such a fluorine compound having at least one isocyanate group at the end of the molecule is dissolved in a suitable solvent such as toluene, and the magnetic layer is immersed in the solution obtained by dissolution, or the solution is poured into the magnetic layer. The fluorine compound is deposited on the magnetic layer by coating or spraying on the surface of the fluorine compound, and when used, any one of the above fluorine compounds may be used alone or in a mixture of two or more. It is preferable that the coating amount be within the range of 3 to 90 .mu./i. If it is too small, the desired effect will not be obtained, and if it is too large, it will cause a decrease in output or dropout.

The magnetic layer formed on the substrate is made of r-Fe203 powder, F
In addition to magnetic powders such as e3O4 powder, Go-containing r-Fe203 powder, Co-containing Fe3O4 powder, and CrO2 powder,
Metal magnetic powder such as Fe powder, CO powder, Fe-Ni powder, etc. is coated on the substrate together with a binder resin and an organic solvent and dried, or CO1Ni, Fe, Co-N
It is formed by depositing a ferromagnetic material such as i, Co--Cr, Co--P, or Co--N1-P on a substrate by means such as vacuum evaporation, ion blasting, sputtering, or plating.

Further, the magnetic recording medium includes various types of structures that come into sliding contact with a magnetic head, such as a magnetic tape having a synthetic resin film such as a polyester film as a base, a magnetic disk or a magnetic drum having a disk or drum as a base.

〔Example〕

Next, embodiments of the invention will be described.

Example 1 A polyester film with a thickness of 12 μm was loaded into a vacuum evaporation apparatus, and cobalt was heated and evaporated under a vacuum of 5×1 OJ5) to form a 0.15 μm thick polyester film on the polyester film.
A ferromagnetic metal thin film layer made of cobalt was formed. Next, this was immersed in a 0.1% by weight Freon solution of α,ω-perfluoroalkylpolyether-bis-carboxyamide-toluene-isocyanate, dried, and cut into a predetermined width to make a magnetic tape. Ta. At this time, the amount of the fluorine compound having an isocyanate group was 5
It was 6■/d.

Example 2 Fe metal powder (average particle size 0.25 80 parts by weight μm
) VAGH (manufactured by tl, c, c company, vinyl chloride 12-
Vinyl acetate-vinyl alcohol copolymer) Takene) L-1007 (Take 1) 4 (manufactured by Yakuhin Kogyo Co., Ltd., urethane play polymer) Coronate Nippon Polyurethane 2 (manufactured by Yakuhin Kogyo Co., Ltd., trifunctional low molecular weight isocyanate compound) Cyclohexanone 6211 toluene
62〃This composition was mixed and dispersed in a ball mill for 60 hours to prepare a magnetic paint, and this magnetic paint was applied onto a polyester film with a thickness of 9 μm to a dry thickness of 13 μm, and dried to form a magnetic layer. did.

Next, in the same manner as in Example 1, this was immersed in a 0.1% by weight Freon solution of a fluorine compound having an isocyanate group, dried, and then cut into a predetermined width to produce a magnetic tape. At this time, the amount of the fluorine compound having an isocyanate group deposited was 76 μ/d.

Example 3 In the composition of the magnetic paint in Example 2, Co-containing rFe2O3 powder (average particle size 0) was used instead of Fe metal powder.
．． A magnetic tape was produced in the same manner as in Example 2, except that the same amount of 25 μm) was used. At this time, the amount of the fluorine compound having an isocyanate group deposited was 73 .mu./d.

Comparative Example 1 In the formation of the protective layer in Example 1, the product name: Fomblin Z25 (manufactured by Montefloras, perfluoropolyethyl) was used instead of the 0.1% by weight Freon solution of the fluorine compound having an isocyanate group. 0.1% by weight of
A magnetic tape was prepared in the same manner as in Example 1 except that a Freon solution was used. The amount of Vonprin Z25 deposited at this time was 64 .mu./d.

Comparative Example 2 In the formation of the protective layer in Example 2, 0.1% by weight of Fomblin Z25 (manufactured by Montefloras, perfluoropolyether) was used in place of the 0.1% by weight Freon solution of the fluorine compound having an isocyanate group. A magnetic tape was prepared in the same manner as in Example 2 except that a wt% Freon solution was used. The amount of Fomblin Z25 deposited at this time was 37 .mu./d.

Comparative Example 3 In forming the protective layer in Example 3, 0.1% by weight Freon solution of a fluorine compound having an isocyanate group was replaced with 0.1% Freon solution of Fonprin Z25 (manufactured by MonteFloas, perfluoropolyether). A magnetic tape was prepared in the same manner as in Example 3 except that the IM% Freon solution was used. The amount of Fomblin Z25 applied at this time was 39■/r+? Met.

Comparative Example 4 In the formation of the protective layer in Example 1, 0.1 wt. % Freon solution of the fluorine compound having an isocyanate group was replaced with 0.1 wt. A magnetic tape was prepared in the same manner as in Example 1 except that a wt% Freon solution was used. The amount of Pydax deposited at this time was 48■
/d.

Comparative Example 5 In forming the protective layer in Example 2, 0.1% by weight Freon of PIDAX (manufactured by DuPont, tetrafluoroethylene telomer) was used instead of the 0.1% by weight Freon solution of the fluorine compound having an isocyanate group. A magnetic tape was produced in the same manner as in Example 2 except that the solution was used. The amount of PIDAX deposited at this time was 51 .mu./d.

Comparative Example 6 In forming the protective layer in Example 3, 0.1% by weight Freon of PIDAX (manufactured by DuPont, tetrafluoroethylene telomer) was used instead of the 0.1% by weight Freon solution of the fluorine compound having an isocyanate group. A magnetic tape was produced in the same manner as in Example 3 except that the solution was used. The amount of PIDAX deposited at this time was 53 .mu./i.

Comparative Example 7 In the formation of the protective layer in Example 1, instead of using a 0.1% by weight Freon solution of a fluorine compound having an isocyanate group, TALITOX 157FS (trade name, manufactured by DuPont, perfluoroalkyl polyether containing a carboxyl group) was used. A magnetic tape was produced in the same manner as in Example 1, except that a 0.1% by weight Freon solution of (1) was used. At this time, the coating amount of TALITTOX 157FS was 68 ■/d.
Met.

Comparative Example 8 In the formation of the protective layer in Example 2, Krytx 157FS (manufactured by DuPont, Co., Ltd.,
A magnetic tape was prepared in the same manner as in Example 2, except that a 0.1% by weight Freon solution of (carboxyl group-containing perfluoroalkyl polyether) was used. The amount of Talytox 157FS deposited at this time was 72 .mu./d.

Comparative Example 9 In the formation of the protective layer in Example 3, Krytsox 157FS (manufactured by DuPont, Co., Ltd.,
A magnetic tape was produced in the same manner as in Example 3, except that a 0.1% by weight Freon solution of (carboxyl group-containing perfluoroalkyl polyether) was used. At this time, the coating amount of TALITOX 157FS was 72 .mu./d.

Comparative Example 10 Same as Example 1 except that in forming the protective layer in Example 1, a 0.1% by weight toluene solution of stearic acid was used instead of a 0.1% by weight freon solution of a fluorine compound having an isocyanate group. Magnetic tape was made in the same way. The amount of stearic acid deposited at this time was 41■/rr
It was f.

Comparative Example 11 Example 2 except that in forming the protective layer in Example 2, a 0.1% by weight toluene solution of stearic acid was used instead of a 0.1% by weight Freon solution of a fluorine compound having an isocyanate group. I made magnetic tape in the same way. The amount of stearic acid deposited at this time was 49■/d
Met.

Comparative Example 12 Same as Example 3 except that in forming the protective layer in Example 3, a 0.1% by weight toluene solution of stearic acid was used instead of a 0.1% by weight freon solution of a fluorine compound having an isocyanate group. Magnetic tape was made in the same way. The amount of stearic acid deposited at this time was 51 .mu./d.

Comparative Example 13 Same as Example 1 except that in forming the protective layer in Example 1, a 0.1% by weight toluene solution of stearylamine was used instead of a 0.1% by weight Freon solution of a fluorine compound having an isocyanate group. Magnetic tape was made in the same way. The amount of stearylamine deposited at this time was 44
■/d.

Comparative Example 14 Same as Example 2 except that in forming the protective layer in Example 2, a 0.1% by weight toluene solution of stearylamine was used instead of a 0.1% by weight Freon solution of a fluorine compound having an isocyanate group. Magnetic tape was made in the same way. The amount of stearylamine deposited at this time was 49
It was +11r/rrr.

Comparative Example 15 Same as Example 3 except that in forming the protective layer in Example 3, a 0.1% by weight toluene solution of stearylamine was used instead of a 0.1% by weight Freon solution of a fluorine compound having an isocyanate group. Magnetic tape was made in the same way. The amount of stearylamine deposited at this time was 47
■/rrl.

Regarding the magnetic tapes obtained in each example and comparative example,
Friction coefficient and jitter properties were measured, and durability, corrosion resistance and adhesion were tested. Friction coefficient is surface roughness 0.2
S, the obtained magnetic tape was wound around a cylindrical pin with an outer diameter of 41TllI+ at a winding angle of 150 degrees, a load of 21 g was applied, the tape was fed at a feed rate of 1.4 cm/sec, and the same point was repeatedly measured until the 100th wear. , the friction coefficient was determined. In addition, to measure the jitter characteristics, load the obtained magnetic tape into a video deck, record and play back the video signal, read the interval of the 15.75 KHz horizontal synchronization signal of the playback signal, and measure the horizontal synchronization signal for one second at that time. This was done by measuring the gap in the synchronization signal interval. Furthermore, a durability test was performed under the conditions of 25°C and 60% RH by running the obtained magnetic tape at a head load of 5 g and a running speed of 0.048 m/sec, and the output was 3 dB lower than the initial output. The number of times the vehicle was run was measured. In addition, the corrosion resistance test was conducted using the obtained magnetic tape at 6
The maximum magnetic flux density was measured after being left at 0° C. and 90% RH for 148 hours. Note that the measured values are expressed as values compared with the maximum magnetic flux density of the magnetic tape before being left as 100%. Furthermore, adhesion was determined by cleaning the obtained magnetic tape with a solvent that dissolves the lubricant used in the protective layer and measuring the varnish vector before and after cleaning. The adhesion force was calculated semi-quantitatively from the amount of decrease, and those in which no decrease in the spectrum was observed (○) and those in which a significant decrease in the spectrum was observed (△) were those in which the spectrum had decreased. Those that did not meet the criteria were evaluated as (x).

The table below shows the results.

〔Effect of the invention〕

As is clear from the table above, the magnetic tapes obtained by the present invention (Examples 1 to 3) have lower friction coefficients and jitters, and are more durable than conventional magnetic tapes (Comparative Examples 1 to 16). This shows that the magnetic recording medium obtained by the present invention has good adhesive properties, further improved durability and corrosion resistance, and excellent running properties.

Claims (1)

[Claims] 1. A magnetic recording medium characterized in that a magnetic layer is formed on a substrate, and a protective layer containing a fluorine compound having at least one isocyanate group at the end of the molecule is provided on the magnetic layer.