JPH08129746A - Magnetic recording medium - Google Patents

Abstract

PURPOSE: To obtain a magnetic recording medium capable of ensuring satisfactory running performance, wear resistance and durability over a long period of time under various service conditions including high temp. and humidity or low temp. CONSTITUTION: A carbon protective film is formed on a magnetic layer and a titanium compd. having acyl, perfluoro-polyether acyl and alkoxy groups or a mixed lubricant prepd. by mixing the titanium compd. with trialkyl thiophosphate is stuck on the protective film.

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 particularly to running property, abrasion resistance,
Regarding improvement of durability.

[0002]

2. Description of the Related Art In recent years, with the increasing demand for high density recording, Co--Ni alloys, Co--Cr alloys, Co--Ni--
A magnetic metal material such as O or Co-O is directly coated on a non-magnetic support such as a polyester film, polyamide, or polyimide film by plating or a vacuum thin film forming means (vacuum deposition method, sputtering method, ion plating method, etc.). A magnetic recording medium of a so-called metal magnetic thin film type in which a magnetic layer is formed by attaching the magnetic recording medium has been proposed and attracts attention.

In particular, an oblique deposition type magnetic recording medium in which a magnetic layer is formed by obliquely depositing a metal magnetic material is excellent in electromagnetic conversion characteristics and a large reproduction output can be obtained. It is put to practical use in the form of a carbon protective film formed on top of it.

By the way, in these metal magnetic thin film type magnetic recording media, since the surface of the magnetic layer is extremely good, the substantial contact area with a sliding member such as a magnetic head or a guide roller is large, and the friction coefficient is large. Grows larger. For this reason, adhesion phenomenon (so-called sticking) with these sliding members
Is likely to occur, and there are many problems such as lack of running performance and durability.

Therefore, the use of various lubricants has been investigated in order to improve such problems. For example, a higher fatty acid or its ester is used as a lubricant to internally add or top coat the magnetic layer, thereby suppressing the friction coefficient.

[0006]

By the way, the lubricant used in the magnetic recording medium is required to have very strict characteristics, and it is difficult to deal with the above-mentioned conventional lubricants under the present circumstances. is there.

That is, the lubricant used in the magnetic recording medium is (1) excellent in low temperature characteristics so as to ensure a predetermined lubricating effect when used in cold regions, and (2) with a magnetic head. Since the spacing becomes a problem, it is required that the coating can be applied extremely thinly, sufficient lubrication characteristics can be exhibited even in that case, and (3) that it can be used for a long time and the lubrication effect continues.

However, the above-mentioned higher fatty acids and esters thereof have insufficient lubrication effect on a magnetic recording medium having a further improved smoothness in order to reduce spacing loss for the purpose of high-density recording, resulting in friction. The running property and durability cannot be sufficiently imparted. Further, there is also a problem that the lubricating performance is impaired particularly under high temperature and high humidity or low temperature of 0 ° C. or less, and the environment in which the effect is obtained is limited.

Therefore, the present invention has been proposed in view of such a conventional situation, and excellent lubricity is maintained under various usage conditions, and the lubricity is maintained for a long time. It is an object of the present invention to obtain a lubricant and provide a magnetic recording medium excellent in running property, wear resistance and durability.

[0010]

Means for Solving the Problems As a result of intensive investigations by the present inventors, it was found that an acyl group,
It has been found that a titanium compound having a perfluoropolyether acyl group and an alkoxy group, particularly a mixture of this titanium compound and trialkylthiophosphite is suitable as a lubricant.

The magnetic recording medium of the present invention has been completed on the basis of such knowledge, and it is obtained by forming a magnetic recording medium on a non-magnetic support.
At least a magnetic layer and a carbon protective film are formed, and a titanium compound having an acyl group, a perfluoropolyether acyl group and an alkoxy group is held on the carbon protective film.

Further, a lubricant mixture of a titanium compound having an acyl group, a perfluoropolyether acyl group and an alkoxy group and a trialkylthiophosphite is retained on the carbon protective film. .

In the magnetic recording medium of the present invention, a magnetic layer and a carbon protective film are formed on a non-magnetic support, and an acyl group, a perfluoropolyether acyl group and an alkoxy group are used as lubricants on the carbon protective film. A titanium compound having a group is deposited. This titanium compound is represented by the general formula of Chemical formula 11, for example.

[0014]

[Chemical 11]

In the titanium compound having such a functional group, the alkoxy group has an -OH group or -OH group on the surface of the carbon protective film.
Reacts with COOH groups at room temperature to form a strong covalent bond. For this reason, when it is slid on various sliding members, it is difficult to separate from the surface of the carbon protective film, and the lubricating performance is maintained for a long period of time.

Further, since the perfluoropolyether acyl group is introduced into the hydrophobic portion, for example, a temperature of 40
Excellent lubrication performance is exhibited even under high temperature and high humidity conditions of ℃ and relative humidity of 80%, and the friction coefficient of the medium can be greatly reduced.

Further, the melting point is controlled by the chain length of the acyl group, and the acyl group has such a chain length that the melting point becomes low, whereby good lubricating performance is exhibited even at a low temperature of 0 ° C. or lower.

Therefore, the magnetic recording medium using such a titanium compound as a lubricant is excellent even under various use conditions including high temperature and high humidity and low temperature where it is difficult to secure running properties and durability. Runnability and durability will be obtained.

In the above titanium compound, an acyl group Ar
Specifically, those having the structure represented by Chemical formula 12 are introduced.

[0020]

[Chemical 12]

In this acyl group Ar, the carbon number a is 5
Must be ~ 23. When the carbon number a is less than 5, the chain length is too short and it becomes difficult to dissolve it in a general-purpose solvent other than CFCs, such as toluene and hexane. When the carbon number a is 24 or more, the melting point increases, and the friction coefficient of the medium increases under low temperature conditions. The more preferable range of the carbon number a is 10 to 23, and when the carbon number a is in this range, a great effect can be obtained. However, the carbon number a of each acyl group Ar does not necessarily have to be the same as long as each is within the appropriate range as described above.

Further, the perfluoropolyether acyl group Rf preferably has a structure represented by any one of chemical formulas 13, 14, and 15.

[0023]

[Chemical 13]

[0024]

Embedded image

[0025]

[Chemical 15]

The molecular weight of these perfluoropolyether acyl groups Rf is not particularly limited, but from the viewpoint of practicality, it is preferably about 600 to 5000, and 100 is preferable.
0 to 4000 is more preferable. If the molecular weight of the perfluoropolyether acyl group Rf is too large, the effect of the terminal group becomes small, and, for example, the adsorption effect of the alkoxy group on the carbon protective film is weakened. Further, it becomes difficult to dissolve in a general-purpose solvent other than CFCs, such as toluene and hexane. On the contrary, if the molecular weight of the perfluoropolyether acyl group Rf is too small, the lubricating effect of the perfluoropolyether acyl group Rf is impaired.

As the alkoxy group RO, since it has an excellent adsorption effect on the carbon protective film,
Those having the structures represented by Formula 7 and Formula 18 are suitable.

[0028]

Embedded image

[0029]

[Chemical 17]

[0030]

Embedded image

The titanium compound has a degree of polymerization of 1
It is desirable that it is -20, more preferably 1-10.

The titanium compound having a functional group as described above alone sufficiently reduces the friction coefficient of the medium,
If a trialkylthiophosphite is further mixed with this titanium compound and used, the lubricating performance is further improved,
The shuttle durability and still durability of the medium are improved.
Examples of the trialkylthiophosphite include chemical formula 1
The one represented by 9 is used.

[0033]

[Chemical 19]

The carbon number n of this trialkylthiophosphite is preferably 9-15. Carbon number n is 1
When it is 6 or more, the solubility in a general-purpose solvent such as toluene and hexane deteriorates. Further, when the carbon number n is 8 or less, the hydrocarbon group becomes short, so that the effect of reducing the friction coefficient of the medium is insufficient.

As a method for holding such a titanium compound or a mixed lubricant of titanium compound and trialkylthiophosphite on the carbon protective film, a titanium compound or a mixed lubricant of titanium compound and trialkylthiophosphite is used as a solvent. A method may be mentioned in which a lubricant solution is prepared by dissolving it and topcoating it on the surface of the carbon protective film. In this case, 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. Further, when the trialkyl thiophosphite and the titanium compound are mixed, it is desirable that the titanium compound is mixed in an amount such that the molar fraction of the mixed lubricant is 0.1 to 0.9.

As described above, in the present invention, a titanium compound having a predetermined functional group or a mixed lubricant of the titanium compound and trialkylthiophosphite is used.
For example, the following materials are used for the non-magnetic support, the magnetic layer, and the protective film.

First, as the non-magnetic support, any of those usually used in magnetic recording media can be used. For example, polyesters such as polyethylene terephthalate, polyolefins such as polyethylene and polypropylene, cellulose derivatives such as cellulose triacetate, cellulose diacetate and cellulose butyrate, vinyl resins such as polyvinyl chloride and polyvinylidene chloride, polycarbonates, polyimides, polyamides. In addition to polymer materials such as, light metals such as aluminum alloys and titanium alloys, ceramics such as alumina glass, and the like. When a rigid substrate such as an aluminum alloy plate or a glass plate is used as the non-magnetic support, an oxide film such as alumite treatment or a Ni-P film is formed on the substrate surface to harden the surface. May be.

The magnetic layer is a metal magnetic thin film formed by depositing a metal magnetic material on a non-magnetic support by a PVD method such as plating, sputtering or vacuum deposition.

As the magnetic metal thin film, Fe, Co, Ni
And other metals, Co-Ni-based alloys, Co-Pt-based alloys, C
o-Pt-Ni based alloy, Fe-Co based alloy, Fe-Ni
Examples of the in-plane magnetization recording type metal magnetic film include a Fe-Co-Ni-based alloy, a Fe-Ni-B-based alloy, an Fe-Co-B-based alloy, and a Fe-Co-Ni-B-based alloy. To be Besides, a perpendicular magnetic recording type metal magnetic film made of a Co—Cr alloy or the like may be used.

Of these, in the case of the in-plane magnetization recording type metal magnetic thin film, Bi, Sb, Pb,
An underlayer of a low melting point non-magnetic material such as Sn, Ga, In, Ge, Si, Tl is formed in advance, and a metallic magnetic material is vertically vapor-deposited or sputtered on the underlayer to form a metallic magnetic thin film. It is good to form. When a metal magnetic material is deposited on the underlayer, the low-melting point nonmagnetic material diffuses in the metal magnetic thin film, the orientation of the metal magnetic thin film is eliminated, and the in-plane isotropic property is ensured. Anti-magnetism is improved.

Further, the carbon protective film to which the lubricant is applied is generally formed by sputtering, but it is not particularly limited and various PVD methods can be adopted. At this time, the thickness of the carbon protective film is preferably 2 to 100 nm, and more preferably 5 to 30 nm in order to obtain a sufficient protective effect while suppressing the spacing loss.

The above is the basic configuration of the present invention. The magnetic recording medium of the present invention is the same as a normal magnetic recording medium.
Further, various elements may be added to further improve the characteristics.

For example, a rust preventive agent may be top-coated with a lubricant on the carbon protective film. Examples of the rust preventive agent that can be used include phenols, naphthols, quinones, nitrogen atom-containing heterocyclic compounds, oxygen atom-containing heterocyclic compounds, and sulfur atom-containing heterocyclic compounds. These rust preventives may be mixed with a lubricant,
It may be a layer different from the lubricant layer, for example, such that it is applied on the protective film separately from the lubricant and then the lubricant is applied after applying the rust preventive agent.

Further, an undercoat layer may be formed on the surface of the non-magnetic support on which the magnetic layer is formed, or a back coat layer may be formed on the surface opposite to the side on which the magnetic layer is formed. May be. Among these, the back coat layer is formed by adding a carbon-based fine powder for imparting conductivity and an inorganic pigment for controlling the surface roughness to the resin binder and applying the same. The back coat layer may be internally added or top-coated with the above-mentioned lubricant mixture.

[0045]

In the titanium compound having an acyl group, a perfluoropolyether acyl group and an alkoxy group, the alkoxy group reacts with the -OH group or -COOH group on the surface of the carbon protective film at room temperature to form a strong covalent bond. For this reason,
When it is slid on various sliding members, it is difficult to separate from the surface of the carbon protective film, and the lubricating performance is maintained for a long period of time.

Further, since the perfluoropolyether acyl group is introduced into the hydrophobic portion, for example, a temperature of 40
Excellent lubrication performance is exhibited even under high temperature and high humidity conditions of ℃ and relative humidity of 80%, and the friction coefficient of the medium can be greatly reduced.

Further, the melting point is controlled by the chain length of the acyl group, and the acyl group has a chain length such that the melting point becomes low, whereby good lubricating performance is exhibited even at a low temperature of 0 ° C. or lower.

Therefore, in a magnetic recording medium using such a titanium compound as a lubricant, good running properties and durability can be obtained under various usage conditions.

When the titanium compound is further mixed with trialkylthiophosphite, the lubrication performance is further improved, and the shuttle durability and still durability of the medium are further improved.

[0050]

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

The titanium compound and trialkylthiophosphite used as the lubricant in this example are as follows.

That is, the titanium compound used in this example is represented by the general formula of Chemical formula 20, in which the acyl group Ar is CH.
₃ (CH _{2) a} COO-, alkoxy group RO is (C
H _{3) 2} CH-O- and is, also the type of perfluoropolyether acyl group Rf, carbon number a of the acyl group, the degree of polymerization b is titanium compounds as shown in Table 1 of the compound (titanium compound 1 Titanium Compound 30) and a general formula of Chemical formula 20, wherein the acyl group Ar is CH ₃ (CH ₂ ) _a COO—,
The alkoxy group RO is (CH ₃ ) ₂ CH—O—, the degree of polymerization b of the compound is 1, the kind of the perfluoropolyether acyl group Rf and the carbon number a of the acyl group are shown in Tables 2 and 3. The same titanium compound (titanium compound 31 to titanium compound 72).

[0053]

Embedded image

[0054]

[Table 1]

[0055]

[Table 2]

[0056]

[Table 3]

However, A, B and C described in the columns of perfluoropolyether acyl groups in Tables 1 to 3 represent the perfluoropolyether acyl groups represented by Chemical formula 21, Chemical formula 22 and Chemical formula 23, respectively. .

[0058]

[Chemical 21]

[0059]

[Chemical formula 22]

[0060]

[Chemical formula 23]

The trialkyl thiophosphite is represented by Chemical formula 24.

[0062]

[Chemical formula 24]

In Examples 1 to 240 below, magnetic tapes were prepared using these titanium compounds or a mixture of titanium compounds and trialkylthiophosphite as a lubricant, and the lubrication performance was examined.

Example 1 On a polyethylene terephthalate film having a thickness of 10 μm,
Co-Ni alloy is deposited by the oblique evaporation method to obtain a film thickness of 10
A 0 nm metal magnetic thin film was formed.

Next, a carbon protective film having a film thickness of 15 nm was formed on the surface of the metal magnetic thin film by sputtering.

Then, a lubricant solution in which the titanium compound 1 was dissolved was applied to the surface of the carbon protective film to form a lubricant film, which was cut into a width of 8 mm to produce a magnetic tape.

Examples 2 to 30 Magnetic tapes were produced in the same manner as in Example 1 except that the titanium compounds shown in Table 4 were used as the titanium compounds dissolved in the lubricant solution.

[0068]

[Table 4]

Examples 31 to 240 Examples 31 to 240 were carried out except that a mixture of the titanium compounds shown in Tables 5 to 11 and the trialkylthiophosphite represented by Chemical formula 24 was dissolved as the lubricant solution. Example 1
A magnetic tape was produced in the same manner as. The mole fraction of the titanium compound in the mixed lubricant is as shown in Tables 5-11.

[0070]

[Table 5]

[0071]

[Table 6]

[0072]

[Table 7]

[0073]

[Table 8]

[0074]

[Table 9]

[0075]

[Table 10]

[0076]

[Table 11]

Comparative Examples 1 to 3 As a lubricant solution, a lubricant solution in which a compound represented by the general formula of Chemical formula 25 and having a kind of perfluoropolyether acyl group Rf shown in Table 12 is dissolved is used. A magnetic tape was produced in the same manner as in Example 1 except that it was used.

[0078]

[Chemical 25]

[0079]

[Table 12]

Comparative Examples 4 to 6 As a lubricant solution, a lubricant solution in which a compound represented by the general formula of Chemical formula 26 and having a kind of perfluoropolyether acyl group Rf as shown in Table 13 is dissolved is used. A magnetic tape was produced in the same manner as in Example 1 except that it was used.

[0081]

[Chemical formula 26]

[0082]

[Table 13]

With respect to each of the magnetic tapes manufactured as described above, the friction coefficient and the still durability under the conditions of temperature 25 ° C. and humidity 60%, temperature 40 ° C. and humidity 80%, and temperature −5 ° C. And shuttle durability was measured.

The still durability was evaluated by measuring the time for the output to decay to -3 dB in the pause state. In addition, the shuttle durability is -3 dB when the shuttle run for 2 minutes is repeated as one shuttle run.
It was evaluated by measuring the number of shuttles until it decreased. The results are shown in Tables 14 to 30.

[0085]

[Table 14]

[0086]

[Table 15]

[0087]

[Table 16]

[0088]

[Table 17]

[0089]

[Table 18]

[0090]

[Table 19]

[0091]

[Table 20]

[0092]

[Table 21]

[0093]

[Table 22]

[0094]

[Table 23]

[0095]

[Table 24]

[0096]

[Table 25]

[0097]

[Table 26]

[0098]

[Table 27]

[0099]

[Table 28]

[0100]

[Table 29]

[0101]

[Table 30]

As can be seen from Tables 14 to 30, magnetic tapes of Examples 1 to 30 using a titanium compound having an acyl group, a perfluoropolyether acyl group and an alkoxy group as a lubricant, and The magnetic tapes of Examples 31 to 240 using such a lubricant mixture of a titanium compound and an alkyl thiophosphite as a lubricant, compared to the magnetic tape of Comparative Example 1, particularly under high temperature and high humidity conditions and low temperature conditions. The friction coefficient is low, and good still durability and shuttle durability are obtained.

From this, the titanium compound having an acyl group, a perfluoropolyether acyl group and an alkoxy group is suitable as a lubricant, and by using it, under various use conditions including high temperature and high humidity conditions and low temperature conditions. It was found that a magnetic recording medium exhibiting excellent runnability, wear resistance and durability can be obtained.

Further, in particular, the magnetic tapes of Examples 31 to 240 are magnetic tapes of Examples 1 to 30 using only a titanium compound having an acyl group, a perfluoropolyether acyl group and an alkoxy group as a lubricant. The still durability and shuttle durability are better than those of the tape.

From this, when a titanium compound having an acyl group, a perfluoropolyether acyl group and an alkoxy group is mixed with a trialkylthiophosphite,
It was found that the lubrication performance was further improved, and the wear resistance and durability of the medium were further improved.

[0106]

As is clear from the above description, in the magnetic recording medium of the present invention, a carbon protective film is formed on the magnetic layer, and an acyl group or a perfluoropolyether acyl group is further formed on the carbon protective film. Also, a titanium compound having an alkoxy group or a mixed lubricant in which a trialkylthiophosphite is mixed with this titanium compound is applied, so that good running can be achieved for a long period of time under various operating conditions including high temperature and high humidity and low temperature. , Wear resistance, and durability can be obtained.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Koichi Kawasaku 6-735 Kitashinagawa, Shinagawa-ku, Tokyo Sony Corporation

Claims (10)

[Claims] 1. A non-magnetic support, on which at least a magnetic layer and a carbon protective film are formed, and a titanium compound having an acyl group, a perfluoropolyether acyl group and an alkoxy group is retained on the carbon protective film. A magnetic recording medium characterized by being provided. 2. A lubricant mixture of a titanium compound having an acyl group, a perfluoropolyether acyl group and an alkoxy group and a trialkylthiophosphite is retained on the carbon protective film. The magnetic recording medium described. 3. The magnetic recording medium according to claim 1, wherein the titanium compound is represented by Chemical Formula 1. Embedded image 4. The magnetic recording medium according to claim 1, wherein the acyl group of the titanium compound has a structure represented by Chemical formula 2. Embedded image 5. The perfluoropolyether acyl group of the titanium compound has a structure represented by any one of Chemical formula 3, Chemical formula 4, and Chemical formula 5. Magnetic recording medium. Embedded image [Chemical 4] Embedded image 6. The magnetic recording medium according to claim 1, wherein the alkoxy group of the titanium compound has a structure represented by Chemical formula 6, Chemical formula 7, and Chemical formula 8. [Chemical 6] [Chemical 7] Embedded image 7. The degree of polymerization b of the titanium compound is from 1 to 20, wherein the titanium compound has a polymerization degree b of 1 to 20.
The magnetic recording medium described. 8. A trialkylthiophosphite is represented by the formula 9
The magnetic recording medium according to claim 2, characterized by: [Chemical 9] 9. A trialkylthiophosphite is represented by the formula 1.
The magnetic recording medium according to claim 8, which is represented by 0 and has a carbon number n of 9 to 15. [Chemical 10] 10. The mole fraction of the titanium compound in the lubricant mixture is 0.1 to 0.9.
The magnetic recording medium described.