JPH05210840A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a magnetic recording medium excellent in traveling property, wear resistance, durability, etc. CONSTITUTION:A lubricant formed by adding a hydrocarbon compound having a hydroxy group in the molecule at 5-80 % content in wt. to perfluoropolyether is applied on the magnetic layer surface of the magnetic recording medium such as magnetic tape, hard disk. Consequently, since the magnetic recording medium is extremely excellent in lubricity and can keep its lubricity in any using condition, the magnetic recording medium excellent in traveling property, wear resistance and durability is obtained.

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 such as a magnetic tape or a magnetic disk, and more particularly to a magnetic recording obtained by coating a lubricant containing perfluoropolyether with a hydrocarbon having a hydroxyl group in the molecule. It is about the medium.

[0002]

2. Description of the Related Art For example, a ferromagnetic metal material is deposited on a non-magnetic support by a method such as vapor deposition to form a magnetic layer.
In a so-called metal thin film type magnetic recording medium, the smoothness of the magnetic layer surface is extremely good, so that the 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 the adhesion is large. Phenomena (so-called sticking) are likely to occur and there are many problems such as lack of running performance and durability.

Therefore, use of various kinds of lubricants has been studied in order to improve these problems, and higher fatty acids, their esters, perfluoropolyethers and the like have been conventionally used for the magnetic layer of the magnetic recording medium. Attempts have been made to suppress the coefficient of friction by coating.

By the way, the lubricant used in the magnetic recording medium is required to have very strict characteristics, and it is difficult at present to deal with the conventional lubricant.

That is, the lubricants used for magnetic recording media are: Excellent low-temperature characteristics to ensure the desired lubrication effect when used in cold regions. Since the spacing with the magnetic head becomes a problem,
2. It can be applied extremely thinly, and in that case, sufficient lubrication characteristics can be exhibited. It is required to withstand long-term use and to maintain the lubricating effect.

[0006]

[Means for Solving the Problems] However, higher fatty acids and their esters, which have been conventionally used, are frozen and solidified under low temperature conditions such as 0 ° C. or lower, impairing the function as a lubricant. Or, it tends to lack long-term durability.

As described above, in the field of magnetic recording media, runnability,
I am still dissatisfied with practical characteristics such as durability. Therefore, the present invention intends to provide a magnetic recording medium which has excellent lubricity under various conditions of use, has a long-lasting lubrication effect, and is excellent in running property, wear resistance, durability and the like. It is a thing.

[0008]

As a result of intensive studies to solve the above-mentioned problems, the present invention provides a perfluoropolyether represented by the following general formula It has been found that a lubricant containing a hydrocarbon having a hydroxyl group is suitable, and the above-mentioned problems have been solved by coating this lubricant on the surface of the magnetic layer of the magnetic recording medium.

[0009]

[Chemical 1]

[0010]

[Function] A lubricant obtained by adding a hydrocarbon having a hydroxyl group in the molecule to perfluoropolyether exhibits a good lubricating effect and reduces the friction coefficient. Further, this lubricating action is not impaired even under severe conditions such as low temperature. Therefore, the magnetic recording medium having a lubricant containing a hydrocarbon having a hydroxyl group in the molecule in this perfluoropolyether has the above-mentioned properties of a lubricant containing a hydrocarbon having a hydroxyl group in the molecule in a perfluoropolyether. The lubrication effect improves runnability and improves durability.

[0011]

EXAMPLES Specific examples of the present invention will be described below, but it goes without saying that the present invention is not limited to these examples.

The hydrocarbon having a hydroxyl group in the molecule of the present invention can be selected regardless of the molecular weight, branched structure, unsaturated bond, isomer structure or alicyclic structure. Further, it may contain a hetero atom. Specifically, its structure is shown in [Table 1].

As the perfluoropolyether, monofunctional and polyfunctional perfluoropolyethers can be used. For example, as the monofunctional ones, those represented by the following [Chemical Formula 2] can be used. , That is,

[0014]

[Chemical 2] Further, as the polyfunctional, those represented by the following [Chemical Formula 3],

[0015]

[Chemical 3] However, the present invention is not limited to these.

Here, k, l, m, n, p and q in the chemical structural formula of the perfluoropolyether represent integers of 1 or more. Examples of X include a hydroxymethyl group, a carboxyl group, an alkoxycarbonyl group, a carboxylic acid amine salt, and an amide, but are not limited thereto.

The molecular weight is not particularly limited,
It is preferably about 600 to 5000. If the molecular weight is too high, the effect of the adsorbing group will be small, and if it is small, the effect of fluorine will be weak. In the case of a hydrocarbon having a hydroxyl group in the molecule, an alkyl group has a large effect on the structure of the hydrocarbon, and an alkyl group having 10 or more carbon atoms has a particularly large effect.

The coating method may be such that it is heated to a temperature higher than the melting point of the hydrocarbon compound having a hydroxyl group in the molecule, stirred with perfluoropolyether, and then dissolved in a solvent such as Freon for coating. Alternatively, the hydrocarbon compound and perfluoropolyether may be dissolved and applied in a solvent such as Freon.

The composition of the lubricant obtained by adding a hydrocarbon having a hydroxyl group in the molecule to the above-mentioned perfluoropolyether is shown in Table 1. In addition, Table 2 shows the perfluoropolyethers used for comparison.

Using the lubricants shown in [Table 1], magnetic recording media shown below were prepared. An example applied to a metal thin film type magnetic recording medium (vapor deposition tape) will be described.

1. Example 1 Co was deposited on a 14 μm-thick polyethylene terephthalate film by the oblique evaporation method to form a ferromagnetic metal thin film having a thickness of 200 nm. Next, on this metal magnetic thin film surface,
A solution obtained by dissolving the synthetic compound 1 in [Table 1] in a Freon solvent was applied so that the application amount was 5 mg / m ^2, and cut into 8 mm width to prepare a sample tape.

2. Examples 2 to 12 Sample tapes were prepared in the same manner as in Example 1 except that the compound 1 in Table 1 used as the lubricant in Example 1 was replaced with the compounds 2 to 14. Was produced.

For each sample tape prepared as described above, when the temperature is 25 ° C. and the humidity is 60%, the temperature is −5 ° C.
At that time, the friction coefficient, the still durability, and the shuttle durability at a temperature of 40 ° C. and a humidity of 80% were measured. For the still durability, the decay time of the output in the pause state up to -3 dB was evaluated. The shuttle durability was evaluated by performing shuttle travel for 2 minutes each time and counting the number of shuttles until the output decreased by 3 dB. In addition, as a comparative example, a blank tape containing no lubricant and a case of using perfluoropolyether alone as a lubricant were also measured. The results are shown in [Table 3].

As is clear from [Table 3], by using perfluoropolyether with a hydrocarbon having a hydroxyl group in the molecule, as compared with the case of using perfluoropolyether alone as the lubricant, The friction coefficient, still durability, shuttle durability, etc. did not deteriorate under various conditions, and very good results were obtained.

Next, the friction coefficient was investigated by changing the amount of the hydrocarbon having a hydroxyl group in the molecule to be added. The results are summarized in [Table 4].

As is apparent from [Table 4], by adding the amount of the hydrocarbon having a hydroxyl group in the molecule to preferably 5 to 90% by weight, better results can be obtained when used alone. ..

Incidentally, in the above-described embodiment, the magnetic recording medium is described as being applied to a so-called metal thin film type magnetic recording medium in which a magnetic material is formed as a magnetic layer on the surface of a non-magnetic support by vapor deposition. It can also be applied to a magnetic recording medium having a structure in which an underlayer is interposed between a magnetic support and a magnetic layer.

The non-magnetic support and the metal magnetic thin film of the applicable metal thin film type magnetic recording medium are not particularly limited, and any conventionally known one can be used. For example, as the non-magnetic support, the same one as the above-mentioned coating type magnetic recording medium can be used. In this case, when a rigid substrate such as an Al alloy plate or a glass plate is used as the non-magnetic support, an oxide film such as an alumite treatment or a Ni-P film is formed on the surface of the substrate to harden the surface. You may do so.

The metal magnetic thin film is formed as a continuous film by a PVD method such as plating, sputtering or vacuum deposition, and is made of a metal such as Fe, Co or Ni, or Co-Ni.
Alloys, Co-Pt alloys, Co-Pt-Ni alloys,
Fe-Co based alloy, Fe-Ni based alloy, Fe-Co-N
In-plane magnetization recording metal magnetic films and Co-Cr alloy thin films made of i-based alloys, Fe-Ni-B-based alloys, Fe-Co-B-based alloys, Fe-Co-Ni-B-based alloys, etc. can be listed.

Particularly, in the case of in-plane magnetization recording metal magnetic thin film,
Bi, Sb, Pb, Sn, Ga, on the non-magnetic support in advance
An underlayer of a low melting point non-magnetic material such as In, Ge, Si, Tl is formed in advance, and a metal magnetic material is vapor-deposited or sputtered from the vertical direction to diffuse the low melting point non-magnetic material in the metal magnetic thin film. It is advisable to eliminate the orientation to secure the in-plane isotropic property and to improve the anti-magnetism.

In the case of a hard disk, it is advisable to form a hard protective film such as a carbon film, a diamond-like or amorphous carbon film, a chromium oxide film and a SiO2 film on the surface of the metal magnetic thin film.

As a method of retaining a lubricant in which a hydrocarbon having a hydroxyl group in the molecule is added to the perfluoropolyether in such a metal thin film magnetic recording medium, the surface of the metal magnetic thin film or the surface of the protective film is lubricated. A method of topcoating the agent layer may be mentioned. In this case, the coating amount of the lubricant in which hydrocarbon having a hydroxyl group in the molecule is added to perfluoropolyether is preferably 0.5-100 mg / m ² , and 1-20 mg / m ^2. Is more preferable.

The lubricant obtained by adding a hydrocarbon having a hydroxyl group in the molecule to the above-mentioned perfluoropolyether may be used alone as a lubricant for a magnetic recording medium, but it may be used in combination with a conventionally known lubricant. Good.

Further, in order to cope with more severe conditions and to maintain the lubricating effect, it is preferable to use an extreme pressure agent together with a compounding ratio of about 30:70 to 70:30 by weight.

The extreme pressure agent reacts with the metal surface by frictional heat generated when a metal contact is partially generated in the boundary lubrication region, and forms a reaction product film, thereby performing a friction and wear preventing action. Which is a phosphorus-based extreme pressure agent,
Sulfur-based extreme pressure agent, halogen-based extreme pressure agent, organometallic extreme pressure agent,
Any of the composite extreme pressure agents can be used.

In addition to the above lubricant and extreme pressure agent, a rust preventive agent may be used in combination, if necessary. As the rust preventive, any rust preventive commonly used as a rust preventive for magnetic recording media of this type can be used, and examples thereof include phenols, naphthols, quinones, nitrogen atom-containing heterocyclic compounds, and oxygen atoms. And a heterocyclic compound containing a sulfur atom.

Incidentally, in the above-mentioned metal thin film type magnetic recording medium, a back coat layer, an undercoat layer and the like may be formed, if necessary, in addition to the metal magnetic thin film which is the magnetic layer. For example, the back coat layer is formed by coating a resin binder similar to that of the magnetic coating film with a carbon-based fine powder for imparting conductivity and an inorganic pigment for controlling the surface roughness.

In the present invention, a compound obtained by adding a long-chain hydrocarbon to the above-mentioned perfluoropolyether may be internally added as a lubricant to the back coat layer, or may be contained by a top coat. Alternatively, various combinations such as magnetic coating, metal magnetic thin film and back coat layer can be internally added as a lubricant in which hydrocarbon having a hydroxyl group in the molecule is added to perfluoropolyether and top coated. ..

[0039]

As is clear from the above description, the magnetic recording medium of the present invention has a weight ratio of hydrocarbons having hydroxyl groups in the molecule to perfluoropolyether having very excellent lubricity in a range of 5 to 90. % I added the added lubricant, so
Good lubricity can be maintained under any conditions of use, that is, even under severe conditions such as high temperature and high humidity or low temperature and low humidity, and the lubricity can be maintained for a long period of time. Therefore, the magnetic recording medium of the present invention is excellent in running property, wear resistance and durability.

[0040]

[Table 1]

[0041]

[Table 2]

[0042]

[Table 3] Durability measurement condition Conditions Friction coefficient Still shuttle Durability (min) Durability (times) Example 1 25 ° C, 60% RH 0.19>120> 150 40 ° C, 80% RH 0.23>120> 150 -5 ° C 0.20>120> 150 Example 2 25 ° C, 60% RH 0.21>120> 150 40 ° C, 80% RH 0.24>120> 150 -5 ° C 0.20> 120 > 150 Example 3 25 ° C, 60% RH 0.19>120> 150 40 ° C, 80% RH 0.23>120> 150 -5 ° C 0.20>120> 150 Example 4 25 ° C, 60% RH 0.20>120> 150 40 ° C, 80% RH 0.24>120> 150 -5 ° C 0.19>120> 150 Example 5 25 ° C, 60% RH 0.21>120> 150 40 ° C, 80 % RH 0.25>120> 150 -5 ° C 0.20>120> 150 Example 6 25 ° C, 60% RH 0.22>120> 150 40 ° C, 80% RH 0. 4>120> 150 -5 ° C 0.20>120> 150 Example 7 25 ° C, 60% RH 0.20>120> 150 40 ° C, 80% RH 0.23>120> 150 -5 ° C 0.20 >120> 150 Example 8 25 ° C, 60% RH 0.18>120> 150 40 ° C, 80% RH 0.21>120> 150 -5 ° C 0.19>120> 150 Example 9 25 ° C, 60 % RH 0.19>120> 150 40 ° C, 80% RH 0.23>120> 150 -5 ° C 0.20>120> 150 Example 10 25 ° C, 60% RH 0.19>120> 150 40 ° C , 80% RH 0.23>120> 150 −5 ° C. 0.20>120> 150 Example 11 25 ° C., 60% RH 0.21>120> 150 40 ° C., 80% RH 0.24>120> 150 -5 ° C 0.22>120> 150 Example 12 25 ° C, 60% RH 0.19>120> 150 40 ° C, 80% RH 0.23>120> 150 -5 ° C 0.19>120> 150 Example 13 25 ° C, 60% RH 0.19>120> 150 40 ° C, 80% RH 0.21>120> 150 -5 ° C 0.18>120> 150 Implementation Example 14 25 ° C, 60% RH 0.20>120> 150 40 ° C, 80% RH 0.25>120> 150 -5 ° C 0.20>120> 150 Comparative Example 1 25 ° C, 60% RH 0.9 2 3 40 ℃, 80% RH ー -5 ℃ ー ー Comparative Example 2 25 ℃, 60% RH 0.33 104 130 40 ℃, 80% RH 0.37 91 55 -5 ℃ 0.34 51 60 Comparative Example 3 25 ° C, 60% RH 0.34 95 120 40 ° C, 80% RH 0.40 76 46 -5 ° C 0.32 29 40 Comparative Example 4 25 ° C, 60% RH 0.31 94 121 40 ° C, 80% RH 0.39 85 54 -5 ° C 0.30 43 43 Comparative Example 5 25 ° C, 60% RH 0.31 97 124 40 ° C, 80% RH 0.37 81 65 -5 ° C 0.32 45 54 Comparison Example 6 25 ° C, 60% RH 0. 2 105 94 40 ° C, 80% RH 0.40 86 56 -5 ° C 0.32 39 50 Comparative Example 7 25 ° C, 60% RH 0.29 114 141 40 ° C, 80% RH 0.33 95 86 -5 ° C 0.30 54 65 Comparative Example 8 25 ° C, 60% RH 0.32 110 123 40 ° C, 80% RH 0.37 102 56 -5 ° C 0.32 65 73 Comparative Example 9 25 ° C, 60% RH 0.34 98 126 40 ° C, 80% RH 0.40 79 76 -5 ° C 0.35 39 50 Comparative Example 10 25 ° C, 60% RH 0.31 111 101 40 ° C, 80% RH 0.37 95 74 -5 ° C 0 30 53 63 Comparative Example 11 25 ° C, 60% RH 0.32 110 115 40 ° C, 80% RH 0.35 96 65 -5 ° C 0.33 67 71 Comparative Example 12 25 ° C, 60% RH 0.30 91 107 40 ° C, 80% RH 0.34 71 56 -5 ° C 0.32 31 46

[0043]

[Table 4] Lubricant composition Molar ratio Friction coefficient Perfluoropolyether / hydrocarbon ∞ 0.33 HOCH ₂ (CF ₂ CF ₂ O) p (CF ₂ O) q CF ₂ CH ₂ OH / C ₁₈ H ₃₈ 95/5 _0.29 90/10 0.29 80/20 0.26 70/30 0.24 60/40 0.23 50/50 0.21 40/60 0.20 30/70 0.21 20/80 0.22 10/90 0.24 5/95 0.25

Claims (2)

[Claims] 1. A magnetic recording medium comprising at least a magnetic layer on a non-magnetic support, wherein the surface of the magnetic layer is made of perfluoropolyether to which a hydrocarbon compound having a hydroxyl group in the molecule is added. A magnetic recording medium characterized by improving. 2. The magnetic recording medium according to claim 1, wherein the content of the hydrocarbon having a hydroxyl group in its molecule is 5 to 90% by weight.