JPH0550045B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a tape-shaped magnetic recording medium whose magnetic recording layer is a ferromagnetic metal thin film suitable for short wavelength recording. Structure of conventional example and its problems Figure 1 is a diagram showing a cross section of a conventional tape-shaped magnetic recording medium (hereinafter referred to as magnetic tape), in which 1 is a support,
2 is a magnetic recording layer, and 3 is a lubricant layer. Recording information using this magnetic tape is a well-known technique, but in recent years the magnetic recording layer 2 has become thinner and thinner in order to record at higher density. Along with this, it is important to protect the lubricant layer 3, especially to improve the scratch resistance when used in helical scanning magnetic recording devices (hereinafter referred to as VTRs), and the types of materials and construction methods have been studied. However, the scratch resistance and running stability under high temperature and high humidity conditions are not sufficient. Therefore, when used for magnetic recording, problems such as increased dropouts due to repeated use and screen fluctuations due to unstable running occurred. This problem arises because short wavelength recording requires the magnetic recording layer and magnetic head with a narrow gap to be brought into close contact with each other, making it impossible to increase the thickness of the lubricant layer to reduce friction. ,
Thickening the lubricant layer improves durability, but increases spacing loss and significantly reduces playback output, making high-density magnetic recording impossible. On the other hand, if the lubricant layer is set to a thickness within the range where the spacing loss is small, VTR This problem occurred because optimization through adjustment could not be performed, as the number of times the device could be used repeatedly was significantly reduced, making it unable to provide sufficient practical performance. Object of the Invention The object of the present invention is to improve the durability of a tape-shaped magnetic recording medium having a ferromagnetic metal thin film as a magnetic recording layer. Structure of the Invention The present invention has a structure in which the magnetic recording layer on the support is a ferromagnetic metal thin film, the lubricant layer on the magnetic recording layer is made of the same material in the width direction of the support, and the amount of lubricant is maximum at both ends. This is a tape-shaped magnetic recording medium (hereinafter referred to as magnetic tape) characterized by the following. DESCRIPTION OF THE EMBODIMENTS In the present invention, the end portions are defined as areas extending 1 mm, preferably 0.6 mm inward from both ends of the magnetic recording layer, as shown schematically in the cross section of the magnetic tape in FIGS. 2 and 3. say. When used in a VTR, this area is not used for recording and reproducing video signals, so increasing the amount of lubricant in this area will not increase spacing loss, but when used repeatedly in a VTR, both ends become magnetic. It is easy to be damaged by abnormal friction caused by occasional contact between heads and rotating cylinders, but by increasing the amount of lubricant in this area, it is thought that the frictional force can be significantly reduced, thereby improving durability. . In FIG. 2, a lubricant layer 5 is disposed on the surface of the magnetic recording layer 2 on the side that comes into sliding contact with the magnetic head and cylinder, and an end lubricant layer 4B and a center lubricant layer 4A (in the present invention, the parts other than the ends are referred to as the center part) In FIG. 3, the lubricant layer 7 consists of an end lubricant layer 6B on the surface of the magnetic recording layer 2, a central lubricant layer 6A, and a cut side lubricant layer 6C of the magnetic recording layer 2. It is completed. Note that the cut side surface lubricant layer 6C may be configured to cover the entire cut side surface of the support 1. The distribution state of the lubricant of the present invention may be a continuous film as schematically shown in FIGS. 2 and 3, or may be an island-shaped discontinuous film well known in the field of thin films. However, the lubricant amount distribution state schematically shown in FIGS. 2 and 3 is not step function-like as shown in FIG. 4a, but rather as shown as examples in FIGS. 4b to 4d. It is more likely that there will be continuous changes. Therefore, the present invention shall be considered including the case where there are more end portions than the average value per unit length in the width direction of the end portions and the center portion. In an even more extreme case, a lubricant is provided only at the ends within the scope of the present invention. The support used in the present invention is a flexible polymer film, and its materials include polyethylene terephthalate, polyethylene naphthalate, polypropylene, polyamide, polyimide, polyacrylamide, cellulose triacetate, polycarbonate, etc. A polymer film with an undercoat layer may also be used. Further, the undercoat layer can be made of either a nonmagnetic material or a soft magnetic material. The ferromagnetic metal thin film that becomes the magnetic recording layer in the present invention is
Fe, Co, Fe-Co, Co-Ni, Fe-Si, Fe-Rh,
Co-P, Co-B, Co-Si, Co-V, Co-Mo,
Co-W, Co-Y, Co-La, Co-Ru, Co-Ce,
Co−Mg, Co−Ca, Co−Sm, Co−Zr, Co−
Mn, Co-Ti, Co-Cr, Co-Ni-Cr, Co-Ni
−Mo, Co−Ni−Mg, Co−Ni−Re, Co−Cr−
These include vacuum-deposited films such as Pt, Co-Ni-Cr-Mg, and Co-Ni-Cr-Rh, vapor-deposited films in gas, sputtered films, ion plating layers, plating films, and chemical vapor plating films. The basic action and effect of the lubricants that can be used in the present invention is not limited to providing lubricity, but also includes those that can play the role of rust prevention by repelling water. The lubricant is fatty acid, fatty acid ester, mineral oil, higher alcohol, etc., and the coating method is to use a doctor blade, reverse roll, squeeze, kiss, etc. coating machine, or by plasma deposition, vacuum deposition, plasma polymerization, etc. It can also be done by Examples will be described in more detail, but it goes without saying that the present invention is not limited to these examples. The magnetic recording layer used in the example was a Co-Cr perpendicularly magnetized film containing 20.3% Cr and having a perpendicular coercive force of 660 [O¨e] formed on a polyethylene terephthalate film with a thickness of 11.5 μm using a high-frequency sputtering method.
The Co-Cr thin film has a thickness of 0.19 μm, and the surface roughness of the support used is 0.04 μm. The evaluation of the Examples and Comparative Examples was carried out by placing a test VTR with a cylinder diameter of 40 mm in various environments and checking the image quality in repeated runs. The tape width was 8 mm. Example 1 Myristic acid dissolved in methyl ethyl ketone was coated on the entire width of an 8 mm wide tape so that the dry thickness was 40 Å. In this state, on both ends within a range of approximately 0.6 mm from the end.
The solution was applied again. Overall thickness when dry
It was applied to a thickness of 90 Å. The lubricant distribution of this magnetic tape was partially redissolved during reapplication, and actual measurements showed that the average lubricant distribution was 80.
The thickness had increased to about 0.8 mm from the end. Example 2 A solution of myristic acid dissolved in methyl ethyl ketone was applied to the entire surface of a support having a 50 cm wide Co-Cr thin film arranged thereon to a dry thickness of about 40 Å. Next, a special process was applied to the coater head, and a solution of myristic acid dissolved in acetone was applied to the coater head at a distance of 8 mm between centers with a coating width of 1 mm to a dry thickness of 60 Å, which was then positioned and cut into 8 mm widths. The lubricant distribution of this magnetic tape is 0.6~0.8 at both ends
The average thickness of the mm region was 85 Å. Example 3 Zinc stearate dissolved in toluene was coated onto an 8 mm wide tape so that the dry thickness was 55 Å. Next, apply zinc stearate dissolved in mether ethyl ketone to both ends within a range of 0.3 mm from the end.
It was applied to a dry thickness of 55 Å. The lubricant distribution of this magnetic tape is approximately 0.5mm from both ends.
The average film thickness up to now was 95 Å. Comparative Examples Examples 1 to 3 in which the lubricant was not reapplied to the ends were designated as Comparative Example 1, Comparative Example 2, and Comparative Example 3, respectively. The evaluation results were as shown in Tables 1 and 2 below. The image quality evaluation ranks are: ◎...no problems at all, ○...dropouts are slightly noticeable, △...the screen sometimes shakes slightly, ×
...Displayed below the practical level.

【table】

【table】

[Table] It is clear from the above table that the magnetic tape of this example can withstand various practical environments compared to the conventional magnetic tape which could only have durability of about 50 passes.
It can be said that it has durability of 200 passes. Effects of the Invention The tape-shaped magnetic recording medium of the present invention maintains excellent reproduced image quality even after repeated use. Specifically, helical scanning VTR
During repeated use in recording experiments, the image quality can be maintained because there is no increase in jitter components, there is no hardness of the medium on posts, cylinders, etc., there is no increase in dropout, there is no change in high frequency output, etc. Therefore, according to the present invention, even higher density magnetic recording can be put to practical use.

[Brief explanation of drawings]

Figure 1 is a cross-sectional view of a conventional magnetic recording medium, Figure 2 is a sectional view of a conventional magnetic recording medium.
3 are cross-sectional views of the tape-shaped magnetic recording medium of the present invention, and FIGS. 4 a to 4 d are examples of lubricant amount distribution diagrams in the width direction of the tape-shaped magnetic recording medium. 1...Support, 2...Magnetic recording layer, 3, 5, 7
...Lubricant layer.

Claims (1)

[Claims] 1. The magnetic recording layer on the support is a ferromagnetic metal thin film, and the lubricant layer on the magnetic recording layer is made of the same material in the width direction of the support, and has a structure in which the amount of lubricant is maximum at both ends. A tape-shaped magnetic recording medium characterized by the following.