JPH1021535A - Magnetic recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To keep an excellent lubricity under various using conditions and to improve traveling property, wear resistance, durability, etc., while keeping lubricating effect over a long time by using a specified acid unhydride as lubricant. SOLUTION: The lubricant is an acid unhydride having one or two polyoxyethylene chain and three or four long chain hydrocarbon in a molecule. A total carbon number in the long chain hydrocarbon is 5-48. When the number of carbon is <5, friction wear durability are insufficient since the length of an alkyl group is too short, and when the number of carbons is >=48, a lubricating film is not formed since a solubility of the lubricant to a solvent at the time of coating of the surface of a tape is reduced. The melting point of the lubricant is lowered and a lubricating characteristic at low temp. is improved by introducing the polyoxyethylene chain. The polyoxyethylene chain is defined as 1-40 unit. When the unit is less <1, substantial effect is hardly caused, and the unit is >=40, the lubricating film is not formed on the surface of the tape since hydrophilic property is increased and the solubility to the solvent is lowered. In this way, the lubricating effect is kept over a long time.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording medium typified by a magnetic tape, a magnetic disk and the like. More particularly, the present invention relates to a magnetic recording medium having excellent lubricity under various conditions of use. , Runnability, wear resistance,
The present invention relates to a magnetic recording medium having excellent durability and the like.

[0002]

2. Description of the Related Art For example, a ferromagnetic metal material is deposited on a nonmagnetic support by a method such as vapor deposition, and this is used as a magnetic layer.
In a so-called metal thin film type magnetic recording medium or a so-called coating type magnetic recording medium in which a magnetic paint containing very fine magnetic particles and a resin binder is applied on a non-magnetic support, and this is used as a magnetic layer, Since the smoothness of the surface of the magnetic layer is extremely good, a substantial contact area with a sliding member such as a magnetic head or a guide roller is large, and therefore, the friction coefficient is large, and an adhesion phenomenon (so-called sticking) is easily caused. There are many problems such as lack of running property and durability.

In order to solve these problems, use of various lubricants has been studied. Conventionally, higher fatty acids and esters thereof have been added to the magnetic layer of the magnetic recording medium, or Attempts have been made to reduce the coefficient of friction by topcoating.

[0004] By the way, lubricants used for magnetic recording media are required to have extremely severe properties due to their properties, and at present, it is difficult for conventional lubricants to cope with them.

That is, the lubricant used for the magnetic recording medium includes (1) excellent low-temperature characteristics so as to ensure a predetermined lubricating effect when used in a cold region, and (2) a lubricant with a magnetic head. Since pacing poses a problem, it is required that the coating be able to be applied extremely thinly, that sufficient lubrication properties be exhibited even in such a case, and that (3) long-term or long-term use, and that the lubrication effect be maintained. Is done.

[0006]

However, the lubricant used in the conventional magnetic recording medium does not always satisfy the above-mentioned requirements. There is.

The present invention provides a magnetic recording medium that maintains excellent lubricity under various use conditions, maintains a lubricating effect for a long time, and is excellent in running properties, wear resistance, durability and the like. The purpose is to do so.

[0008]

Means for Solving the Problems As a result of intensive studies, the present inventors have found that the above objects can be achieved by using a specific acid anhydride as a lubricant. Was completed.

That is, the present invention relates to a magnetic recording medium comprising a magnetic layer formed on a non-magnetic support, and a carbon film formed on the magnetic layer. An acid anhydride having one or two polyoxyethylene chains and three or four long-chain hydrocarbon groups is applied.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The magnetic recording medium of the present invention has a characteristic feature in that a specific acid anhydride is applied as a lubricant on a carbon film formed on a magnetic layer.

The lubricant used in the present invention contains 1
An acid anhydride having one or two polyoxyethylene chains and three or four long-chain hydrocarbons, for example, a compound represented by the following chemical formula:

[0012]

Embedded image R ^1- (CH ₂ CH ₂ O) iR ² -CO-O-CO-R ^3- (CH ₂ CH ₂ O) jR ⁴

Wherein R ¹ represents CH ₃ (CH ₂ ) k;
R ² represents (CH ₂ ) ₁ ; R ³ represents (CH ₂ ) m; and R ⁴ represents CH ₃ (CH ₂ ) n;
= 1-20, j = 0-20, i + j = 1-
40, k = 3-22, n = 0-22, k + n = 5-40, l = 0-6, and m =
0-6, and l + m = 1-12.

Preferably, i = 2 to 10, j = 0 to 1
0, i + j = 2 to 20, k = 5 to 17, n = 0 to 17,
k + n = 5-34, l = 0-3, m = 0-3, l + m =
0 to 6 is preferable.

As can be seen from the above, the “long chain” in the present invention may have 1 carbon atom at the lower limit.
Further, in the above chemical formula, a situation in which both l and n are 0 in the R ² and R ³ groups can be considered, but in the present invention, three or more long-chain hydrocarbon groups must be present. ^At least one of the ^two groups and the R ³ group must be present.

Therefore, the total number of carbon atoms in the long chain hydrocarbon group is 5 to 48. If the number of carbon atoms is less than 5, the length of the alkyl group is too short, which causes a problem in friction / wear durability. If the number of carbon atoms exceeds 48, the solubility of the lubricant in the solvent when the lubricant is applied to the tape surface decreases, and a lubricant film cannot be formed on the tape surface, which is not preferable.

Further, by introducing a polyoxyethylene chain, the melting point of the lubricant is reduced, and the lubricating properties at low temperatures are improved. The polyoxyethylene chain can have from 1 to 40 units, as can be seen from the above chemical formula. 1
If it is less than the unit, no substantial effect is exhibited, while if it exceeds 40, on the other hand, the hydrophilicity is too large, so that the solubility in the solvent is reduced and a lubricating film cannot be formed on the tape surface in some cases.

The lubricant used in the present invention is held on the carbon film by a suitable means, for example, a top coat. The coating amount of the lubricant, it is preferably a 0.5 to 100 mg / m ^2, more preferably 1 to 20 mg / m ^2.

The non-magnetic support that can be used in the present invention can be selected from conventionally known ones, and is not particularly limited. For example, non-magnetic supports include polyesters such as polyethylene terephthalate and polyethylene-2,6-naphthalate; polyolefins such as polypropylene; celluloses such as cellulose triacetate and cellulose diacetate; vinyl resins; And a metal plate made of a polymer material typified by polycarbonates, an aluminum alloy, a titanium alloy, or the like, a support made of glass, ceramics, or the like. In this case, when a rigid substrate such as an Al alloy or a glass plate is used for the non-magnetic support, an oxide film such as alumite treatment or Ni-P
A film or the like may be formed to harden the surface. The form is not limited at all, and may be any form such as a tape form, a sheet form, and a drum form. Further, in order to control the surface property, the non-magnetic support may be subjected to a surface treatment for forming fine irregularities.

The magnetic layer can be formed as a continuous film of a metal magnetic material by a PVD technique such as plating, sputtering, or vacuum deposition. For example, Fe, Co, Ni
, A Co-Ni alloy, a Co-Pt alloy, C
o-Pt-Ni alloy, Fe-Co alloy, Fe-Ni
In-plane magnetization recording metal magnetic film or Co-Cr made of a base alloy, an Fe-Co-Ni-based alloy, an Fe-Ni-B-based alloy, an Fe-Co-B-based alloy, an Fe-Co-Ni-B-based alloy A system alloy thin film is exemplified.

In the case of an in-plane magnetization recording metal magnetic film,
Bi, Sb, Pb, Sn, Ga,
A base layer of a low-melting non-magnetic material such as In, Ge, Si, or Tl is formed, and a metal magnetic material is vapor-deposited or sputtered from a vertical direction to diffuse these low-melting non-magnetic materials into the metal magnetic thin film. The orientation may be eliminated to ensure in-plane isotropy, and the coercivity may be improved.

Further, the magnetic recording medium of the present invention is such that a carbon film is formed on such a magnetic layer.
In the magnetic recording medium of the present invention, a method for forming a carbon film is generally sputtering, but is not particularly limited thereto, and any other method can be used.

The carbon film has a thickness of 2 to 100 nm.
And more preferably 5 to 30 nm.

In the present invention, a rust preventive may be used in combination with the lubricant, if necessary. As the rust inhibitor, any one which is usually used as a rust inhibitor for this type of magnetic recording medium can be used, for example, phenols, naphthols, quinones, heterocyclic compounds containing a nitrogen atom, oxygen atoms And heterocyclic compounds containing a sulfur atom. The rust inhibitor may be used in combination with the lubricant, but the rust inhibitor is applied in two or more layers, such as applying a rust inhibitor layer on the carbon film and then applying a lubricant layer. Then the effect is high.

[0025]

When a carbon film is formed by sputtering, the pH of the carbon film is about 2, and it has been found that the carbon film has a considerably acidic surface. Therefore, the hydrophilic group site (-OH, -COOH, etc.) has a high acidity,
Hard to adhere on carbon film. On the other hand, the acid anhydride in the lubricant used in the present invention has lower acidity than carboxylic acid and the like, whereby the adhesion to the carbon film increases. Therefore, it is considered that the lubricant in the present invention adheres tightly to the carbon film surface, thereby reducing the friction coefficient and improving shuttle and still durability.

[0026]

EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited to these examples.

Example of Preparation of Sample Tape A Co—Ni alloy was applied to a 10 μm-thick polyethylene terephthalate film by an oblique deposition method,
A magnetic layer of a ferromagnetic metal thin film having a thickness of nm was formed. Next, a carbon film having a thickness of 15 nm was formed on the surface of the magnetic layer by sputtering, and cut into a width of 8 mm to obtain a sample tape. A sample tape without a carbon film was also prepared.

Examples 1 to 20 In the following chemical structural formulas, i, j, k, l, m and n
Were varied as shown in Table 1 to prepare a plurality of types of lubricants.

[0029]

Embedded image R ² — (CH ₂ CH ₂ O) i—R ² —CO—O
_{^{-CO-R 3 - (CH 2}} CH 2 O) j-R 4

Wherein R ¹ represents CH ₃ (CH ₂ ) k; R ² represents (CH ₂ ) ₁ ; R ³ represents (CH ₂ ) m; and R ⁴ represents CH ₃ (CH ₂₎ ) Represents n.

The coating amount of the lubricant on the carbon film is 1 to
It was 10 mg / m ² .

Next, with respect to each of the samples thus prepared, at a temperature of 25 ° C. and a relative humidity of 60%, at a temperature of 40 ° C. and a relative humidity of 80%, and further at a temperature of −5 ° C.
The coefficient of friction, still durability and shuttle durability at the time of were measured. Still durability is the output of the pause
The decay time up to 3 dB was evaluated. Shuttle durability
Shuttle run for 2 minutes each time, output -3d
Evaluation was made based on the number of shuttles required until B dropped.

Comparative Examples 1 to 5 Examples 1 to 20 were repeated, except that a lubricant having the following chemical structural formula was used.

[0034]

Embedded image CH ₃ (CH ₂ ) p COOH

In the formula, p is from 10 to 20 as shown in Table 1.
Was changed within the range.

[0036]

[Table 1]

The results obtained are shown in Tables 2 and 3. Tables 2 and 3 show that the magnetic recording medium of the present invention was much better in friction coefficient, still durability, shuttle durability, and the like than the comparative example even under various conditions at normal temperature or low temperature. I understand.

[0038]

[Table 2]

[0039]

[Table 3]

[0040]

According to the present invention, excellent lubricating properties can be maintained under various conditions of use, the lubricating effect is maintained for a long time, and magnetic recording excellent in running properties, abrasion resistance, durability and the like. A medium is provided.

Claims (5)

[Claims] 1. A magnetic recording medium in which a magnetic layer is formed on a non-magnetic support, and a carbon film is formed on the magnetic layer. A magnetic recording medium coated with an acid anhydride having two polyoxyethylene chains and three or four long-chain hydrocarbon groups. The acid anhydride is represented by the following formula: R ^1- (CH ₂ CH ₂ O) iR ² -CO-O-CO-R ^3- (CH ₂ CH ₂ O) jR ⁴ , R ¹ represents CH ₃ (CH ₂ ) k; R ² represents (C
R ₂ represents (H ₂ ) ₁ ; R ³ represents (CH ₂ ) m;
⁴ represents CH ₃ (CH ₂₎ n; a where i = 1 to 20, a j = 0 to 20, a i + j = 1~40,
k = 3 to 22, n = 0 to 22, k + n = 5
４０40, l = 0０〜6, m = 0６6,
And 1 + m = 0 to 12). 3. i is 2 to 10, j is 0 to 10, i + j is 2 to 20, k is 5 to 17, n is 0 to 17, and k + 1 is 5 to 3.
34, l is 0-3, m is 0-3, and l + m is 0-6
3. The magnetic recording medium according to claim 2, wherein 4. The amount of the lubricant applied on the carbon film is:
The magnetic recording medium according to any one of claims 1 to 3 is 0.5 to 100 mg / m ^2. 5. The magnetic recording medium according to claim 1, wherein the carbon film has a thickness of 2 to 100 nm.