JPS5968822A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve wear resistance by using a resin obtd. by bringing a compd. is a higher aliphat. alcohol, higher fatty acid or the modified matter thereof and has a functional group reactable with an isocyanate group into reaction with a magnetic layer or protective layer. CONSTITUTION:At least one kind selected from a compd. which is higher aliphat. alcohol, higher fatty acid and the modified matter thareof and has a functional group reactable with an isocyanate group and a polyisocyanate compd. having >=2 isocyanate groups are brought into reaction with each other in the excess of the isocyanate groups, whereby a compd. A is obtd. A resin obtd. by bringing such compd. A into reaction with a compd. B having >=2 hydroxyl groups is used. With the compd. A, the higher aliphat. alcohol having 12-20C is preferable, for which there is lauryl alcohol, etc. The higher fatty acid having 12-20C is preferable, for which there is undecylic acid, etc. The functional group reactable with the isocyanate group is a hydroxyl group, etc. The compd. B is ethylene glycol, etc.

Description

[Detailed description of the invention] The present invention relates to a magnetic recording medium with improved wear resistance.

Conventionally, the magnetic layer of a magnetic recording medium is easily abraded because it comes into violent sliding contact with a magnetic head during magnetic recording or reproduction, and a material with excellent abrasion resistance is desired. Therefore, it has been proposed to provide a protective layer made of a lubricant such as wax or paraffin on the magnetic layer, but with this method it is possible to prevent wear of the magnetic layer due to the lubricity of the protective film. Since the protective coating is weak and has poor adhesion to the magnetic layer, it easily disappears due to sliding contact with the magnetic head, resulting in a problem that it cannot withstand long-term use.

Now, various methods have been proposed to improve these drawbacks. For example, mixture of phosphoric acid esters of higher aliphatic alcohols (JP-A-50-66206), HLB8
A combination of the following and a surfactant with an HLB of 13 or higher (% opening 55
-93533) and containing silicone oil (Japanese Unexamined Patent Publication No. 56-71825), but since these methods involve mixing or adding silicone oil, the head may become dirty due to bleed or the characteristics may deteriorate. A decline is inevitable.

A method in which a lubricant solution is applied to the magnetic layer and then heat-treated has also been reported (Japanese Patent Application Laid-Open No. 13527/1983). Although it may be expected that a reaction will occur, it cannot be said to be certain, and in the case of a twisted or vapor-deposited magnetic layer, no reaction can be expected at all, and the above-mentioned drawbacks have not been completely improved.

The higher aliphatic alcohol or higher fatty acid ester used in the present invention has good lubricity and wear resistance, as seen in JP-A-55-93533 and JP-A-56-68931. However, since these techniques use the above-mentioned lubricant alone, it cannot be said that they have necessarily improved the problem of dirt on the surface or deterioration of properties.

In order to improve such drawbacks, the present invention has been developed by reacting a compound having a functional group capable of reacting with an isocyanate group in the magnetic layer layer or retention layer with a higher aliphatic alcohol, a higher fatty acid type, or a modified product thereof. This objective was achieved by using the obtained resin.

That is, in the magnetic layer provided on the substrate or the protective layer provided on the magnetic layer, the following (A) and (13)
This is a magnetic recording medium with excellent abrasion resistance that uses a resin obtained by reacting.

(A) at least one selected from higher aliphatic alcohols, higher fatty acids, and modified products thereof having a functional group capable of reacting with inocyanate groups; and a polyisocyanate compound having two or more isocyanate groups; Since the compound (A) has an isocyanate group, it can be reacted with the compound (I3) having a hydroxyl group, and the result of the reaction is The resulting resin is strong and robust. Higher fatty acids, higher aliphatic alcohols - These modified products are fixed to the resin through urethane bonds, so they do not have the aforementioned drawbacks such as decreased wear due to bleeding, head stains, and decreased properties. Demonstrates stable effects over a long period of time.

The sintered compound (A) has good compatibility with polyurethane resins and other resins, and can also solve the problem of precipitation due to crystallization, which occurs when higher aliphatic alcohols are mixed alone.

The higher aliphatic alcohol (A) preferably has 10 to 26 carbon atoms, more preferably 12 to 2 carbon atoms.
0 is preferred. For example, Raul alcohol, tritethyl alcohol, myristyl alcohol, pentadecyl alcohol, cetyl alcohol, heftatecyl alcohol, stearyl alcohol, nonatecyl alcohol,
Examples include eicosyl alcohol. The higher fatty acid has 10 or more carbon atoms, preferably 2 to 20 carbon atoms. For example, undecylic acid, lauric acid, tridecylic acid, myristic acid, pentadecylic acid, palmitic acid, heptadecylic acid, stearic acid, nonadecanoic acid, arachidic acid, behenic acid, lignoceric acid, cerotic acid, heptacanoic acid, montanic acid, melisic acid,
rough cellic acid, 10-hydroxystearic acid, 12-hydroxystearic acid, 2-hydroxystearic acid,
These include 4.9-dihydroxystearic acid, 9.10-dihydroxystearic acid, oleic acid, elaidic acid, cetoleic acid, erucic acid, braidic acid, linoleic acid, linuric acid, and ricinoleic acid.

In addition, modified products of higher aliphatic alcohols or higher fatty acids include compounds that have a functional group that reacts with a hydroxyl group or a carboxyl group, and the result of this reaction produces a functional group that can react with an incyanate group. Alternatively, it can be obtained by reacting a compound having a functional group capable of reacting with an isocyanate with a higher aliphatic alcohol or a higher fatty acid. Examples of functional groups that can react with isocyanate groups include hydroxyl groups, amine groups, carboxyl groups, and ester groups. As an example, the compounds reacted with higher fatty acids include ethylene glycol, propylene glycol, 1,3-butanediol, ], 4-butanediol,
Neopentyl glycol, 1,6-hexanediol,
These are polyhydroxy compounds such as trimethylolpropane, glycerin, pentaerythritol, sorbitan, polyether polyol, and polyester polyol, and alcohol amines such as dimethylethanolamine, jetanolamine, triethanolamine, and aminomethylpropanol.

Examples of the polyisocyanate compound (A) having two or more incyanate groups include hexamethylene diisocyanate, tetramethylene diisocyanate, lysine diisocyanate-1, dimeryl diisocyanate, inphorone diisocyanate, 2,4-tri Diincyanate, 2.6-tolylene diisocyanate, 4.4
'-Diphenylmethane diisocyanate, m-phenylene diisocyanate, ■, 3-xylylene diisocyanate, ■, 5-naphthalene diisocyanate, hydrogenated tolylene diisocyanate, hydrogenated *4.4'
-diphenylmethane diincyanate, etc., and may also be dimers or trimers of the above-mentioned isocyanate compounds, as well as ethylene glycol, propylene glycol, 1.3-butanediol, neobutyl glycol, trimethylolpropane, glycerin, pentamer, etc. A polyisocyanate compound obtained by reacting a polyhydroxy compound such as erythritol, sorbitan, polyether polyol, or polyester polyol with the above-mentioned isocyanate compound may also be used. Of course, two or more of the above isocyanate compounds may be used in combination.

Higher aliphatic alcohols, higher fatty acids, or the above-mentioned modified products are reacted with isocyanate compounds in the presence of an excess of isocyanate groups, and the molar ratio for the reaction is in the range of 1:1 to 1:100. and more preferably in the range of 1:2 to 1:50. In the case outside the above range, in a range where the isocyanate group is not excessive, that is, in a range where the above molar ratio is 1:1 or less, two or more hydroxyl groups of (I3) are used to reduce the number of unreacted isocyanate groups. In the range where the reaction with the compound is no longer possible and the cleaved isocyanate groups are extremely excessive, that is, the above molar ratio is 1
: If it exceeds 100, the amount of higher aliphatic alcohol etc. that provides lubricity decreases, so that the effects of improving the lubricity and abrasion resistance of the film formed on the magnetic layer layer or the protective layer cannot be obtained.

The compound (B) having two or more hydroxyl groups to be reacted with the compound having an isocyanate group (I-) is ethylene glycol, propylene glycol, 1,3-butanediol, 114-butanediol, neopentyl glycol, etc. Recall, ■, polyhydroxy compounds such as 6-hexanediol, trimethylolpropane, glycerinol, pentaerythritol, sorbitan, polyether polyol, polyester polyol, cell openings such as acetylcellulose, nitrocellulose, methylcellulose, ethylcellulose, etc. Derivatives, vinyl chloride-vinyl acetate-alcohol copolymer, acrylic polyol, vinyl chloride-
These include various conventionally known resins having hydroxyl groups such as vinyl propionate copolymer, polyvinyl butyral, and mixtures thereof.

Non-magnetic films such as polyester films, polyolefin films, cellulose films, polyamide films, etc.
In a magnetic layer or a protective layer provided on various conventionally known substrates, the desired resin usually reacts with the body) and the desired resin is released.

For the reaction between (A) and (13), a catalyst used in ordinary urethane reactions is used. Examples of catalysts include organic tin compounds, organic zinc compounds, organic iron compounds, organic lead compounds, and amines. The catalyst is resin 10
It is used in a range of 0.001 to 5 parts by weight relative to 0 parts by weight, and in a range of 0.01 to 3 parts by weight. The compound (A), the compound (B) having a hydroxyl group, and the catalyst are usually used diluted with a solvent.

Although the resin obtained by the reaction of (A) and (B) according to the present invention can be used as a single resin in the magnetic layer, it is usually used together with a vehicle resin to form the magnetic layer. Ti is usually used as a single resin for the protective layer, but it does not preclude the use of other resins in combination. The magnetic layer or protective layer can be formed by various conventionally known methods. In the case of a magnetic layer, a magnetic layer in which magnetic powder is dispersed in a vehicle resin may be used, or a magnetic layer formed by vapor deposition may also be used. good. In the case of vapor deposition, a protective layer is always provided. To form the protective layer, it is coated on the magnetic layer so that the dry film thickness is about 01 to 5 μm.

Various conventionally known methods can be used as the coating means.

Hereinafter, the present invention will be explained based on examples.

In the examples, "parts" indicate parts by weight.

Resin synthesis example-1 Coronate L (polyincyanate compound manufactured by Nippon Polyurethane Co., Ltd. solid content 75%) 296.7 parts, K-3
23.3 parts of wax (12-hydroxystearic acid triglyceride manufactured by Yubin Fine Chemical Co., Ltd.) and 100 parts of toluene were placed in a 500" four-bottle flask, stirred and mixed thoroughly at room temperature, and heated to 90°C while stirring.
The temperature rose to .

After reacting at 90°C for 2 hours, resin A-1 (solid content approximately 57
．． Section 7) was obtained.

Resin Synthesis Example-2 284 parts of Coronae L, 5.9 parts of stearyl alcohol, and 100 parts of toluene were placed in a 500 CC four-bottle flask, thoroughly stirred and mixed at room temperature, and then heated to 90°C while stirring.

Resin A-2 (solid content approx. 55
．． Section 4) was obtained.

Example 1 110 parts of resin A-Vinyrite VAGH (manufactured by UCC,
Vinyl chloride-vinyl acetate-vinyl alcohol copolymer resin) 57.7 parts, methyl ethyl ketone-toluene (1:1
) A solution containing 571 parts of a mixed solvent was prepared. This solution was applied to the surface of the metal magnetic thin film of a magnetic tape in which a 02 μm thick metal magnetic thin film made of cobalt-nickel alloy (weight ratio 9:1) was formed by vapor deposition on a 12 μm thick poly-11-ester film. Apply to a coating thickness of 0.5μm and dry at 60°C.
, heat treatment was performed for 24 hours to form a cured film (protective layer).

Example 2 A cured film was formed in the same manner as in Example 1 except that a mixed solution containing the same amount of resin A-2 was used instead of resin A-1 in Example 1.

Comparative Example 1 A cured film was formed in the same manner as in Example 1 except that a mixed solution containing the same amount of Coronate L was used instead of resin A-1.

Each of the magnetic tapes obtained in Example 1.2 and Comparative Example 1 above was placed in a 3.8 mm width casing.

The finished product was made into a tote tag, placed in an audio cassette, and was run repeatedly to measure durability, running performance, and initial coefficient of friction.

12- (*: Tape that does not form resin repeats) In the table, durability was determined by the number of runs until the output decreased by 3 dB from the initial output level. In addition, the runnability is indicated by a mark ◯, which is good, and a mark △, which is slightly poor.

From the magnetic tape test results of the above examples and comparative examples,
It can be seen that the magnetic recording medium of the present invention forms a film containing a lubricating component bonded to a polymer compound, and has excellent durability and runnability.

Example 3 r -Fe 203 powder 60 parts Vinyrite VAGH 15 parts Carbon plastic resin 2 parts Dispersant (lecithin) 1.5 parts Methyl ethyl chloride 110 parts Toluene
70 parts These compositions were kneaded in a ball mill for 30 hours, then 6 parts of Resin A-1 was added and mixed in a ball mill for 1 part to prepare a magnetic paint.

This paint was applied onto a polyester film with a thickness of 12 μm, oriented on a permanent magnet, and after drying the M agent, a surface smoothing treatment was performed, and then the paint was placed in an oven kept at 60°C for 48 hours.
Heat treatment was performed for a period of time to form a hardened magnetic layer.

Example 4 A hardened magnetic layer was formed in the same manner as in Example 3, except that the same amount of resin A-2 was used instead of resin A-1 in Example 3.

Comparative Example 3 A hardened magnetic layer was formed in the same manner as in Example 3, except that 25 parts of Coronate L was used instead of resin A-1 in Example 3.

Comparative Example 4 In Comparative Example 3, 0.2 parts of K-3wax was added. All other conditions were the same as in Comparative Example 3 (a hardened magnetic layer was formed).

The magnetic tapes obtained in Examples 3 and 4 and Comparative Example 3 were made into cassette tapes with a medium size of 3.8 wIn, placed in an audio cassette and tape, and run repeatedly to determine durability, runnability, and initial performance. The friction coefficient was measured.

From the magnetic tape test results of the above examples and comparative examples,
It can be seen that the magnetic recording medium of the present invention has excellent durability and runnability.

patent applicant Toyo Ink Manufacturing Co., Ltd. 16 one

Claims (1)

[Claims] 1. Magnetic recording characterized by using a resin obtained by reacting the following substances and directions in a magnetic layer provided on a substrate or in a protective layer provided on the magnetic layer. Medium. <A) At least one selected from higher aliphatic alcohols, higher fatty acids, and modified products thereof having functional groups that can react with isocyanate groups, and a polyisocyanate compound having two or more incyanate groups. , a compound obtained by reacting with an excess of isocyanate groups (B) a compound having two or more hydroxyl groups