JPH064857A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve the electromagnetic transducing characteristics of a magnetic recording medium and to satisfactorily enhance the running durability. CONSTITUTION:When a lubricant layer consisting of a lubricant having a polar group at a terminal of each molecule and a lubricant having no polar group at the terminals of each molecule is formed on a magnetic layer to obtain a magnetic recording medium, the amt. of the lubricant having a polar group is made larger than that of the lubricant having no polar group in the surface side of the lubricant layer in the thickness direction.

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,
More specifically, it relates to a magnetic recording medium having good electromagnetic conversion characteristics and excellent running durability.

[0002]

2. Description of the Related Art Generally, a magnetic recording medium prepared by depositing a ferromagnetic material on a substrate by vacuum deposition or the like runs while contacting with a magnetic head or the like, so that the magnetic layer has a small friction coefficient and wear. It is required to be small and have excellent running durability.

Therefore, various lubricant layers have conventionally been provided on the magnetic layer to reduce the friction coefficient and improve the running durability. For example, carboxylic acid perfluoroalkyl ester and A lubricant layer made of perfluoropolyether is provided on the magnetic layer. (Japanese Patent Publication No. 62-236118)

[0004]

However, this kind of carboxylic acid perfluoroalkyl ester and perfluoropolyether do not have a polar group at the terminal of the molecule, and a lubricant layer made of them is placed on the magnetic layer. If formed, the friction coefficient is reduced and the running durability is improved, but since the interaction with the magnetic layer surface is not sufficient, the lubricant is likely to separate from the magnetic layer surface during sliding contact with the magnetic head, There is a problem that the slidable contact surface of the magnetic head is contaminated with the removed lubricant and the output during recording and reproduction is deteriorated.

[0005]

SUMMARY OF THE INVENTION The present invention has been made as a result of various investigations in view of the present circumstances. A lubricant having a polar group at the molecular end and a polar group at the molecular end on the magnetic layer are not provided. Provide a lubricant layer consisting of a lubricant, and make the lubricant having polar groups at the molecular ends more on the surface side than the magnetic layer side in the thickness direction of the lubricant layer than lubricants not having polar groups at the molecular ends. Prevents the lubricant from separating from the surface of the magnetic layer and prevents the separated lubricant from contaminating the sliding surface of the magnetic head. At the same time, the lubricant's excellent lubricating effect is fully exerted, and the output during recording and reproduction is improved. The running durability is sufficiently improved without deteriorating.

According to the present invention, since the lubricant layer provided on the magnetic layer is composed of a lubricant having a polar group at the molecular end and a lubricant having no polar group at the molecular end,
The external load stress on the lubricant that has a polar group at the molecular end and is adsorbed to the magnetic layer surface by this polar group is mitigated by the freely moving lubricant that does not have a polar end at the molecular end. . In addition, since the lubricant having a polar group at the molecular end is made to be more on the surface side than the magnetic layer side in the thickness direction of the lubricant layer than the lubricant not having a polar group at the molecular end, the polar group is added to the molecular end. The lubricants have a tendency to form multimers with each other, and serve as a barrier for preventing the lubricant having no polar group at the molecular end from being eliminated.

However, the barrier effect of the lubricant having the polar group at the molecular end and the stress relaxation effect of the lubricant having no polar group at the end of the molecule simultaneously occur, and the lubricant is released from the surface of the magnetic layer. Of the magnetic head, the dirt on the sliding contact surface of the magnetic head is also sufficiently suppressed, the output during recording and reproduction does not deteriorate, and the excellent lubricating effect of the lubricant used in combination is sufficiently exerted to improve running durability. Is sufficiently improved.

As described above, a lubricant layer having a polar group at the molecular end is formed more in the thickness direction of the lubricant layer than on the lubricant having no polar group at the molecular end on the surface side rather than the magnetic layer side. In order to do so, each of these lubricants is dissolved in an organic solvent such as methyl ethyl ketone, n-hexane, isopropyl alcohol, and Freon, and a solution having a polar group-free lubricant is first formed on the surface of the substrate. It is carried out by a method such as coating or spraying on the formed magnetic layer, and further coating or spraying on it a solution in which a lubricant having a polar group at the molecular end is dissolved.

In addition, a solution in which a lubricant having no polar group at the molecular end is dissolved is applied or sprayed on the magnetic layer formed on the surface of the substrate, while a lubricant having a polar group at the molecular end is applied. After coating or spraying the dissolved solution on the back surface of the substrate, the magnetic recording medium raw material is cured in a wound state, and on the magnetic layer coated with a lubricant having no polar group at the molecular end, It is also carried out by a method such as transferring a lubricant having a polar group to the molecular end attached to the back surface of the substrate,
The method is not particularly limited.

The lubricant layer thus formed contains 0.01 to 1 of a lubricant having a polar group at the molecular end on the magnetic layer.
It is preferable that the lubricant is applied in the range of 0 mg / m ^{2 and} a lubricant having no polar group at the molecular end is applied in the range of 0.01 to 10 mg / m ² , and the polar group is attached to the molecular end. If the amount of the lubricant contained is less than 0.01 mg / m ² , the running durability is insufficient, and if it exceeds 10 mg / m ² , the magnetic tape causes a sticking phenomenon when it is used as a magnetic tape. Also,
If the amount of lubricant that does not have a polar group at the molecular end is less than 0.01 mg / m ² , running durability is not sufficient and 10 mg / m ²
If it is more, the sliding surface of the magnetic head becomes dirty and the output deteriorates.

Examples of the lubricant having a polar group at the molecular end include fluorine-based lubricants such as commercially available products from DuPont; Krytox and Montecatini; Fomblin Z-DEAL and Fomblin Z-DOL. , Fomblin Z-DIAC, Fomblin Z-DISOC, Fomblin Z-AM2001 and the like are preferable, and examples of the hydrocarbon lubricant include fatty acids such as stearic acid and palmitic acid, and amides of these fatty acids,
Esters, alcohols and the like are preferred.

Further, as the lubricant having no polar group at the molecular end, carboxylic acid perfluoroalkyl ester,
Preferred examples include modified products of fluorine compounds and hydrocarbon compounds such as perfluorooctyl stearate, hydrocarbon compounds such as normal butyl stearate and oleyl oleate, and silicone oil.

The magnetic layer is formed of Fe, Co, Ni, Co
-Ni, Co-Cr, Fe-Ni, Fe-Co, Co-
P, Co-Pt, Fe-Co-B, Co-Ni-Fe-
B, Fe-Co-Ni, Co-Ni-Pt, Co-Ni
A ferromagnetic material such as -P, or a ferromagnetic material containing a trace amount of a rare earth metal, is deposited on the substrate by a method such as vacuum deposition, ion plating, sputtering or plating. It

When the above-mentioned lubricant is formed on the magnetic layer thus formed, a slight amount of water may be attached to the surface of the magnetic layer. It may be one coated with an agent or one provided with a protective film layer made of an organic compound, carbon, silicon oxide or the like by vacuum vapor deposition, sputtering, plasma or the like. Further, an extreme pressure agent or the like may be added to the protective film layer.

A back coat layer may be provided on the back surface of the substrate having a magnetic layer formed on the front surface. The back coat layer contains a non-magnetic powder such as carbon black or calcium carbonate and vinyl chloride- A coating material for a back coat layer is prepared by mixing and dispersing it with a binder resin such as a vinyl acetate copolymer, a urethane resin, a fibrin resin and an organic solvent, and the coating material for the back coat layer is magnetic on the surface. It is formed by coating and drying on the back surface of the layered substrate. This back cover
An extreme pressure agent or the like may be added to the coating layer.

As the magnetic recording medium, there are various magnetic tapes having a synthetic resin film such as a polyethylene terephthalate film as a base, a magnetic disk having a disk or a drum as a base, and a magnetic drum having a structure in sliding contact with a magnetic head. Including the form of.

[0017]

EXAMPLES Next, examples of the present invention will be described. Example 1 A polyethylene terephthalate film having a thickness of 10 μm was loaded in a vacuum vapor deposition apparatus, and a Co—Ni alloy was heated and evaporated under a residual gas pressure of 5 × 10 ⁻⁵ torr of oxygen gas to continuously evaporate the Co—Ni alloy. Obliquely incident on the surface of the polyethylene terephthalate film, and Co-Ni-O (Co: Ni = 8
0:20) to form a magnetic layer having a thickness of 0.2 μm.

Then, on the magnetic layer formed on the surface of the polyethylene terephthalate film, a 0.5% by weight freon solution of carboxylic acid perfluoroalkyl ester was added.
After coating so that the coating amount was 0.5 mg / m ² , a 0.5 wt% Freon solution of Fomblin Z-DOL was further coated on the back surface of the polyethylene terephthalate film so that the coating amount was 1.5 mg / m ² . To form a lubricant layer. Next, after the raw material of the magnetic recording medium was wound up, a curling treatment was performed at 60 ° C. for 24 hours, and then 8
A magnetic tape was produced by slitting it into a width of mm.

The surface of the obtained magnetic tape was subjected to ESCA analysis at 20 ° and 80 ° by an angle resolution method. As a result, it was found that Fomblin Z-DOL (a) was found on the surface side of the lubricant layer.
The ratio a / b of the carboxylic acid perfluoroalkyl ester (b) is 12 in the analysis at 20 ° and 3 in the analysis at 80 °.
4, and the proportion of Fomblin Z-DOL was high on the surface side of the lubricating layer.

Example 2 In the formation of the lubricant layer in Example 1, 0.5% by weight of normal butyl stearate was used instead of 0.5% by weight of Freon solution of perfluoroalkyl carboxylic acid.
The amount of isopropyl alcohol solution deposited is 0.5 mg / m ²
Fomblin Z-DAL was replaced with a 0.5 wt% Freon solution of Fomblin Z-DOL instead of Fomblin Z-DEAL.
A lubricant layer was formed in the same manner as in Example 1 except that the 0.5 wt% Freon solution was applied so that the coating amount was 1.5 mg / m ^2, and a magnetic tape was produced.

The surface of the obtained magnetic tape was subjected to ESCA analysis at 20 ° and 80 ° by an angle resolution method. As a result, it was found that Fomblin Z-DEAL was found on the surface side of the lubricant layer.
Ratio a between (a) and normal butyl stearate (b)
/ B was 7 in the analysis of 20 ° and 18 in the analysis of 80 °, and the proportion of Fomblin Z-DEAL was high on the surface side of the lubricating layer.

Example 3 In the formation of the lubricant layer in Example 1, the deposition amount of carboxylic acid perfluoroalkyl ester was 0.5 mg / m 2.
^A magnetic tape was produced in the same manner as in Example 1 except that the amount was changed from ² to 1.0 mg / m ² .

The surface of the magnetic tape thus obtained was subjected to ESCA analysis at 20 ° and 80 ° by an angle resolution method. As a result, it was found that Fomblin Z-DOL (a) was found on the surface side of the lubricant layer.
The ratio a / b of the carboxylic acid perfluoroalkyl ester (b) is 9 in the analysis at 20 ° and 17 in the analysis at 80 °.
And the proportion of Fomblin Z-DOL was high on the surface side of the lubricating layer.

Comparative Example 1 In the same manner as in Example 1, a magnetic layer was formed on the surface of the polyethylene terephthalate film. Then, a 0.5 wt% Freon solution of fomblin Z-DOL was applied on the magnetic layer formed on the surface of the polyethylene terephthalate film so that the applied amount was 1.5 mg / m ^2, and then polyethylene terephthalate was further added. A 0.5 wt% Freon solution of a carboxylic acid perfluoroalkyl ester was applied to the back surface of the tarte film so that the amount of coating was 0.5 mg / m ² to form a lubricant layer. Next, in the state in which this raw material of the magnetic recording medium was wound, a curling treatment was performed at 60 ° C. for 24 hours, and then a slit was formed into a width of 8 mm to produce a magnetic tape.

The surface of the obtained magnetic tape was subjected to ESCA analysis at 20 ° and 80 ° by an angle resolution method. As a result, on the surface side of the lubricant layer, Fomblin Z-DOL (a) was obtained.
The ratio a / b of the carboxylic acid perfluoroalkyl ester (b) was 1/38 in the analysis at 20 ° and 1/26 in the analysis at 80 °, and Fomblin Z- at the surface side of the lubricating layer.
The proportion of DOL was low.

Comparative Example 2 A magnetic layer was formed on the surface of a polyethylene terephthalate film in the same manner as in Example 1. Then, on the magnetic layer formed on the surface of the polyethylene terephthalate film, a 0.5 wt% Freon solution of fomblin Z-DEAL was applied so that the coating amount was 1.5 mg / m ^2, and then, On the back surface of the polyethylene terephthalate film, a 0.5 wt% isopropyl alcohol solution of normal butyl stearate was applied so that the amount of the adhered amount would be 0.5 mg / m ² , to form a lubricant layer. Next, in a state in which this raw material of the magnetic recording medium was wound up, a curling treatment was carried out at 60 ° C. for 24 hours and then a magnetic tape was produced by slitting it into a width of 8 mm.

The surface of the obtained magnetic tape was subjected to ESCA analysis at 20 ° and 80 ° by an angle resolution method. As a result, it was found that Fomblin Z-DEAL was found on the surface side of the lubricant layer.
Ratio a between (a) and normal butyl stearate (b)
/ B is 1/20 for 20 ° analysis and 1 / for 80 ° analysis
16 and Fomblin Z-DEA on the surface side of the lubricating layer
The proportion of L was low.

The magnetic tape obtained in each Example and Comparative Example
With respect to the magnetic tape, the still life, magnetic head contamination, and output deterioration were examined in the following manner.

<Still life> Using a still tester which is a remodeled commercial VTR deck, the magnetic tape is reproduced in still mode at room temperature and normal humidity, and the reproduction output level becomes half of the initial output level. The time required for the decrease was measured.

<Dirty magnetic head> The obtained 120-minute-long magnetic tape was observed for head dirt after running 100 times on a VTR, and when no dirt was observed (5), dirt was found. The evaluation was performed on a scale of 5 on the basis of (4) when slight stains were observed, (3) when stains were observed, (2) when stains were found to be slightly larger, and (1) when severe stains were observed.

<Output Deterioration> The obtained magnetic tape is VT
The reproduction output after running 100 times at R was measured, and the output reduction value with respect to the initial output was measured. Table 1 below shows the results.

[0032]

[0033]

As is apparent from Table 1 above, the magnetic tapes obtained in the present invention (Examples 1 to 3) are superior to the conventional magnetic tapes (Comparative Examples 1 to 2) in that The still life is long, the magnetic head is less contaminated, and the output is less deteriorated. From this, it is understood that the magnetic recording medium obtained by the present invention has good electromagnetic conversion characteristics and excellent running durability.

Claims (1)

[Claims] 1. A lubricant layer comprising a lubricant having a polar group at the molecular end and a lubricant having no polar group at the molecular end is provided on the magnetic layer, and the lubricant having the polar group at the molecular end is added to the molecule. A magnetic recording medium characterized in that the amount of lubricant on the surface side is larger than that on the magnetic layer side in the thickness direction of the lubricant layer than the lubricant having no polar group at the end.