JPH08287450A - Coating type magnetic recording medium - Google Patents

Abstract

PURPOSE: To obtain a coating type magnetic recording medium keeping superior lubricity under various service conditions, maintaining a lubricating effect over a long time and excellent in running performance, wear resistance and durability. CONSTITUTION: This magnetic recording medium has at least a magnetic layer on the nonmagnetic substrate. The surface of the magnetic layer is coated with a long chain hydrocarbon carboxylic acid anhydride lubricant having two long chain hydrocarbon groups represented by the formula R1 -CO-O-CO-R2 (where R1 is CH3 (CH2 )m , R2 , is CH3 (CH2 )n , (m) is 2-28, (n) is 2-28 and (m+n) is 10-40, preferably (m) is 6-22, (n) is 6-22 and (m+n) is 12-36) or the above lubricant is incorporated in the magnetic layer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coating type magnetic recording medium such as a magnetic tape or a magnetic disk, and in particular, it is coated with a long chain hydrocarbon anhydride type lubricant having two long chain hydrocarbon groups. Alternatively, it relates to a coating type magnetic recording medium internally added.

[0002]

2. Description of the Related Art In an 8-mm video deck, a tape inserted in the deck is guided by 10 or more guide pins and wound around a drum. At that time, the tape tension and the tape running speed are kept constant by the pinch roller and the capstan, the tension is about 20 g, and the running speed is 0.5 cm / s. In this running system, the magnetic layer of the tape is in contact with the stainless guide pin. Therefore, when the friction coefficient of the tape surface becomes large, the tape causes stick-slip,
A phenomenon called so-called tape squeaking may occur, which may cause the playback screen to be tight. Further, the relative speed between the tape and the head is very large, and especially in the paused state, the head slides at the same position on the tape at a high speed, which may cause a problem of wear of the magnetic layer and reduce the reproduction output.

Therefore, use of various kinds of lubricants has been studied in order to solve these problems, and higher fatty acids and their esters have been conventionally used as top coats or magnetic layers in the magnetic layer of the above-mentioned coating type magnetic recording medium. Attempts have been made to suppress the coefficient of friction by internally adding.

By the way, the lubricant used in the coating type magnetic recording medium is required to have very strict characteristics, and it is difficult to cope with the conventional lubricant.

That is, the lubricant used in the coating type magnetic recording medium is (1) excellent in low temperature characteristics so as to ensure a predetermined lubricating effect when used in cold regions.
(2) Spacing with the magnetic head poses a problem, so it can be applied extremely thinly, and in that case also sufficient lubrication characteristics can be exhibited. (3) Long-term use and long-term lubrication effect Is required, and so on.

In order to solve the problems of the increase of the friction coefficient and the durability, it is necessary to examine the lubricant to be applied or internally added to the surface, and the good lubricating performance with the head, the tape or the disk. Uniform and strong adhesion to the surface, good exudation of the lubricant internally added to the tape, and long-term (for example, 10 years) retention of these performances, etc. It is desired to realize it with a lubricating film applied to a film thickness or a lubricant added internally.

[0007] By the way, when classifying the lubricants which have been developed especially for the coating type magnetic recording medium up to the present, there are three kinds, that is, a silicon type, a hydrocarbon type and a fluorocarbon type.

The silicon-based lubricant is one of the lubricants often used in the coating type medium because of its good thermal stability and low vapor pressure. However, in the coating type medium having a very good surface property currently used, the silicon-based lubricant does not have sufficient lubricating performance.

Fluorine-based lubricants are currently the most widely used lubricants in thin film magnetic recording media.
Among the fluorinated lubricants, perfluoropolyether is widely used because it has better lubricating performance and surface protection action than other fluorinated lubricants. For this reason C
Since the ether bond of F ₂ —O—CF ₂ is flexible, its viscosity is lower than that of perfluoroalkane having the same molecular weight, and that the viscosity does not change in a wide temperature range. In addition, it is chemically inert, has low vapor pressure, has high thermal or chemical stability, has low surface energy, has good boundary lubrication properties, and has high water repellency. Is mentioned as a feature. However, since perfluoropolyether is chemically inert, it has a low compatibility with the binder and is difficult to internally add to the coating medium. Moreover, it is not suitable for a coating type medium because of its high cost.

Further, perfluoropolyethers are dissolved only in freons, which is a problem from the viewpoint of global environment protection.

Hydrocarbon-based lubricants are still the mainstream lubricants for coating type magnetic recording media. However, in terms of thermal or chemical stability, hydrocarbon-based lubricants are generally inferior to silicon-based or fluorine-based lubricants. For this reason, in a system using a hydrocarbon-based lubricant, a frictional polymer formed by reaction of molecules by friction is likely to be generated. This polymer reduces the lubricating properties and sometimes causes catastrophic failure. Further, the hydrocarbon-based lubricant has a drawback that the vapor pressure is high. Hydrocarbon lubricants have excellent friction characteristics, but since they have a high vapor pressure, they gradually volatilize, and therefore are difficult to use in thin film magnetic media in which lubricant cannot be replenished.

[0012] As described above, the properties required of the lubricant are extremely strict, and all the properties such as thermal or chemical stability, adsorbability with the medium surface, etc. are completely satisfied in addition to the lubrication performance. At present, what has been done has not been realized.

[0013]

As described above, in the field of magnetic recording media, due to the lack of ability of the lubricant used, the practical characteristics such as running durability of magnetic recording media are not satisfactory. I have left.

Therefore, the present invention provides a coating type 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 and durability. It is intended to provide.

[0015]

The above object of the present invention is achieved by the following constitutions. That is, a coating type magnetic recording medium having at least a magnetic layer on a non-magnetic support, wherein a long chain hydrocarbon anhydride type lubricant having two long chain hydrocarbon groups is coated on the surface of the magnetic layer. Or a coating type magnetic recording medium in which a long chain hydrocarbon anhydride type lubricant having two long chain hydrocarbon groups is internally added in the magnetic layer.

As the long-chain hydrocarbon anhydride type lubricant having two long-chain hydrocarbon groups of the present invention, the compound represented by the general formula (A) can be used, but the lubricant is not limited thereto.

R ₁ —CO—O—CO—R ₂ (A) where R ₁ : CH ₃ (CH ₂ ) _m , R ₂ : CH ₃ (C
_{H 2) n, m = 2~28} , n = 2~28, m + n = 10~
40, preferably m = 6-22, n = 6-22, m +
n = 12 to 36.

The alkyl group of the general formula (A) has m = 6 carbon atoms.
-22, n = 6-22, and m + n = 12-36, it can be selected regardless of the branched structure, unsaturated, presence or absence of aromatic ring, isomer or alicyclic structure.

Further, according to the present invention, a long-chain hydrocarbon acid anhydride type lubricant having two long-chain hydrocarbon groups is internally added or top-coated in the magnetic layer of the coating type magnetic recording medium to obtain high temperature and high humidity. Alternatively, even when it is used under severe conditions such as low temperature and low humidity, good durability is obtained, and its characteristics are not deteriorated.

The coating type magnetic recording medium of the present invention preferably has a tryptophan derivative lubricant containing a perfluoropolyether group and a hydrocarbon group having 6 or more carbon atoms.

As the magnetic recording medium to which the present invention is applied, a long-chain hydrocarbon anhydride lubricant having two long-chain hydrocarbon groups is used as a magnetic powder on a non-magnetic substrate using a polymer binder. It can be used for the coating type magnetic recording medium coated on. In that case, the lubricant may be top-coated on the surface of the magnetic layer, or may be internally added to the magnetic layer.

The above long-chain hydrocarbon anhydride type lubricant having two long-chain hydrocarbon groups may be used alone as a lubricant for a magnetic recording medium, but it is used in combination with a conventionally known lubricant. May be.

A rust preventive may be used in combination. 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 coating type magnetic recording medium, in addition to the magnetic layer, a back coat layer, an undercoat layer and the like may be formed if necessary.

For example, the back coat layer is formed by coating a carbon-based fine powder for imparting conductivity to a resin binder similar to the magnetic coating film and an inorganic pigment for controlling surface roughness. is there.

In the present invention, the long-chain hydrocarbon anhydride lubricant having two long-chain hydrocarbon groups described above may be internally added to the back coat layer or may be contained by a top coat. Alternatively, various combinations such as internally adding and top-coating a long-chain hydrocarbon acid anhydride-based lubricant having two long-chain hydrocarbon groups in both the magnetic coating film and the back coat layer are also possible.

[0027]

The long-chain hydrocarbon anhydride lubricant having two long-chain hydrocarbon groups exhibits a good lubricating action and reduces the friction coefficient. Further, this lubricating action is not impaired even under severe conditions such as low temperature. Therefore, the coating type magnetic recording medium in which the long-chain hydrocarbon anhydride type lubricant having two long-chain hydrocarbon groups is top-coated or internally added, the runnability is improved and the durability is improved.

[0028]

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 magnetic recording media shown below were prepared by using the lubricants of Examples 1 to 24 shown in Tables 1 and 2 as the compounds 1 to 24, respectively. Examples and comparative examples applied to a coating type magnetic recording medium (metal tape) will be described.

[0030]

[Table 1]

[0031]

[Table 2]

Example 1 Metal powder Magnetic powder 100 parts by weight Vinyl chloride-vinyl acetate copolymer 10.5 parts by weight Polyurethane resin 10.5 parts by weight Carbon (antistatic agent) 5 parts by weight Methyl ethyl ketone 150 parts by weight Cyclohexanone 150 parts by weight

The above composition was used as a basic composition, mixed in a ball mill for 24 hours, taken out through a filter, and further 4 parts by weight of Coronate L (polyisocyanate manufactured by Nippon Polyurethane Co., Ltd.) was added as a curing agent.
Stir for 0 minutes. This magnetic coating material was applied onto a polyethylene terephthalate base having a thickness of 12 μm so that the thickness after drying was 2 μm, magnetic field orientation was performed, and then the coating was dried and wound. This was calendered and then cut into a width of 8 mm. A long-chain hydrocarbon anhydride lubricant (synthetic product 1) having two long-chain hydrocarbon groups dissolved in toluene was applied thereon to give a coating amount of 5 mg / m ^2, and 8 mm A sample tape was produced by cutting into a width.

Examples 2 to 24 Samples of Examples 2 to 24 according to the procedure of Example 1 except using Compounds 2 to 24 in Table 1 respectively as lubricants for the top coat. A tape was made.

With respect to each of the sample tapes of Examples 1 to 24 produced as described above, the friction coefficient, the shuttle durability test and the still durability test were conducted at 25 ° C. 60%.
The test was conducted under the environment of RH, -5 ° C and 40 ° C 80% RH. The results are shown in Tables 3 to 5 together with the comparative examples.

[0036]

[Table 3]

[0037]

[Table 4]

[0038]

[Table 5]

When the temperature is 25 ° C. and the relative humidity is 60%, aging (temperature 40 ° C., relative humidity 80%, 7%
It was tested for its coefficient of friction and stick-slip, and dropout before and after storage. The results are shown in Table 6 and Table 7, respectively.

[0040]

[Table 6]

[0041]

[Table 7]

The stick-slip was judged by whether the coefficient of static friction during rubbing exceeds 0.6. For dropout, 3 μsec for 3 minutes, 1
It shows the number of times that output reduction of 0 dB or more occurs.

As is clear from the results of Tables 3 to 5, Table 6 and Table 7, in a magnetic recording medium having at least a magnetic layer on a non-magnetic support, a length having two long chain hydrocarbon groups was used. By internally adding the chain hydrocarbon anhydride type lubricant, the friction coefficient, stick slip and dropout were not deteriorated under various conditions, and very good results were obtained.

[0044]

As is apparent from the above description, the magnetic recording medium of the present invention has a long-chain hydrocarbon anhydride lubricant having two long-chain hydrocarbon groups having extremely excellent lubricity. Since it possesses, it is possible to maintain the lubricity under any use condition, and also to maintain the lubricity for a long period of time. That is, the magnetic recording medium of the present invention is excellent in wear resistance, durability, and especially running property.

Claims (3)

[Claims] 1. A coating type magnetic recording medium comprising at least a magnetic layer on a non-magnetic support, wherein a long-chain hydrocarbon anhydride type lubricant having two long-chain hydrocarbon groups on the surface of the magnetic layer. A coating type magnetic recording medium characterized by being coated with an agent. 2. A coating type magnetic recording medium comprising at least a magnetic layer on a non-magnetic support, wherein a long-chain hydrocarbon anhydride type lubricant having two long-chain hydrocarbon groups in the magnetic layer. A coating type magnetic recording medium characterized by internally adding an agent. 3. A long-chain hydrocarbon anhydride having two long-chain hydrocarbon groups is represented by the formula (A) R ₁ —CO—O—CO—R ₂ (A) R ₁ : CH ₃ (CH ₂ ) _m. , R ₂ : CH ₃ (CH ₂ ) _n , m = 2
The coating type magnetic recording medium according to claim 1 or 2, which is a compound represented by? 28, n = 2-28, and m + n = 10-40.