JPH0573902A - Production of magnetic recording medium - Google Patents

Abstract

PURPOSE:To decrease head clogging, uneven head wear and drop-out at the time of recording and reproducing of the magnetic recording medium having excellent high-density recording and reproducing characteristics and to provide the surface design of an excellent traveling property and durability. CONSTITUTION:The surface of the magnetic layer is subjected to three treatments; coating with a 1st lubricant directly or via a protective layer, polishing treatment and coating with a 2nd lubricant and these three treatments are executed in this order in the process for production of the magnetic recording medium. Further preferably, the coating of the above-mentioned 2nd lubricant is executed after the surface subjected to the above-mentioned polishing treatment is washed with an org. solvent.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a magnetic recording medium, and its object is to reduce head clogging, head uneven wear and dropout at the time of recording / reproducing, and to improve runnability. The present invention provides a manufacturing method for realizing a surface design of a high density recording medium having excellent durability.

[0002]

2. Description of the Related Art In recent years, magnetic recording / reproducing devices are becoming smaller and higher in density, and there is an urgent need to develop a magnetic recording medium having excellent high density recording / reproducing characteristics. In coating media, miniaturization of magnetic powder, control of shape and magnetic characteristics,
Alternatively, due to the progress of coating technology, the high-density recording / reproducing performance is definitely improving. Further, a metal thin film type medium has been attracting attention as one that exceeds the limit of high density of the coating type medium. In this regard, a metal thin film type medium composed of Co-Ni-O has already been put to practical use as a magnetic tape for VTR, and further, Co-Cr, Co-O, etc. are mainly used as a next-generation high-density magnetic recording medium. The development of a perpendicular magnetic recording medium as a component is also in progress.

In developing the above-mentioned high-density magnetic recording medium, the surface design technology of the medium occupies a very important position. For example, when used as a magnetic recording tape for a VTR, it is necessary to secure sufficient running property and durability in sliding with a metal post, a cylinder, a head, etc. in a running system. Therefore, in the current magnetic recording medium, a protective film containing carbon (C), CoO or the like as a main component is formed on the magnetic film to increase the surface strength (for example, JP-A-2-96).
No. 923), a fine protrusion is formed on the surface to reduce the coefficient of dynamic friction when sliding with each part of the traveling system.

The formation of the fine projections is performed by a method of dispersing and coating fine particles of SiO ₂ or the like on a non-magnetic substrate or filling the inside of the substrate, a method using an oligomer of a polymer substrate, a method by ion etching, etc. (For example, JP-A-1-158616).

On the other hand, as the recording wavelength becomes shorter as the recording density becomes higher, the reproduction output is more seriously deteriorated due to the spacing loss during recording and reproduction. In particular, when recording and reproducing using a ring head for a perpendicular magnetic recording medium, the spacing loss tends to be larger than that of a longitudinal recording medium,
The spacing between the head and the recording layer of the medium due to the protective layer and the minute protrusions should be minimized. Therefore, how to reduce the spacing while maintaining the running property and the durability is an issue in the development of the high density magnetic recording medium, and in this sense, the surface design technology of the medium is important. In the next-generation high-density VTR tape, the spacing should be 25 nm or less, preferably about 10 to 15 nm.

However, when it is attempted to provide minute protrusions on the medium surface with a spacing of 25 nm or less, the conventional surface design technique is insufficient, and protrusions with uniform height are formed with sufficient density and evenly. Is difficult to do. That is, in order to secure stable running performance and durability, the head,
It is necessary to have a density of about 10 or more minute protrusions per 1 μm ² that contributes to friction with the cylinder, traveling system parts, etc. However, if minute protrusions are formed at this density by conventional technology, the protrusion height becomes uneven, There are many protrusions that are higher than the average protrusion height by 5 to 10 nm or more. This is because when the formation of the fine protrusions is carried out by a method of dispersing and coating fine particles of SiO ₂ or the like onto a non-magnetic substrate or filling the inside of the substrate, the fine particles cause aggregation. Such protrusions are called abnormal protrusions, which increase the spacing during recording / reproduction, reduce the reproduction output, cause uneven wear of the head and dropout, and also cause the gap between the head, cylinder, and travel system parts. The dynamic friction coefficient μ _k is increased to deteriorate running performance and durability.

Therefore, at present, there has been proposed a technique for controlling the surface design of a magnetic recording medium on which fine protrusions are formed by polishing the surface (for example, Japanese Patent Application No.
240824, Japanese Patent Application No. 2-242129). Such surface polishing treatment is realized by bringing a blade or a wrapping tape into contact with the surface of the medium and running the medium.

[0008]

[Problems to be Solved by the Invention] According to our study,
In the medium whose surface was designed by the above-mentioned surface polishing treatment, there were some cases in which a sufficient medium life could not be obtained.
For example, in the case of a VTR tape, it is possible to obtain sufficient performance in various items such as recording / reproducing characteristics, running property, surface strength, head uneven wear, dropout, etc. in a medium immediately after surface polishing. After traveling over the range, occurrence of dropouts, clogging of the head, running failure, etc., which are considered to be due to deterioration of the medium, are observed.

The surface polishing treatment removes unnecessary abnormal protrusions on the medium by frictional force, and if appropriate treatment conditions are not satisfied, in some cases even in a region where such unnecessary protrusions do not exist. It is expected that there will be microregions that are subject to high pressure. In such a minute area, defects that are not recognized in the initial characteristics occur,
It is considered that such defects are magnified and the above-mentioned problems are caused by increasing the number of times of running.

Further, when the polishing powder from the surface polishing treatment remains on the surface of the medium, it mixes with the lubricant to become foreign matter on the medium. It is considered that these foreign matters adhere to the sliding surface of the head when the deck is running and cause clogging of the head, and also cause deterioration of the medium through friction with various parts of the running system.

Such deterioration of the medium is recognized in the special test as described above, and it is considered that there is almost no problem in normal use, but from the viewpoint of ensuring reliability, it is definitely solved. This is an issue that must be addressed.

[0012]

The present invention provides means for improving the above-mentioned problems, and in a method for manufacturing a magnetic recording medium having a magnetic layer formed on a non-magnetic substrate, the magnetic layer surface is formed. Directly or through a protective layer, three treatments of a first lubricant coating, a polishing treatment, and a second lubricant coating are performed, and the three treatments are performed in the order described above, and more preferably, the polishing is performed. It is characterized in that the surface after the treatment is washed with an organic solvent and then the second lubricant is applied.

[0013]

In order to solve the problem, we have studied various surface treatment conditions of the magnetic recording medium, and as a result, found that the manufacturing method of the above-mentioned structure can prolong the life of the medium and reduce head clogging due to polishing powder. It was

In the above structure, by applying an appropriate amount of lubricant to the medium before the surface polishing treatment, the damage to the medium during the surface polishing treatment can be minimized.
That is, it is considered that by applying the first lubricant, it is possible to suppress only unnecessary abnormal protrusions from being subjected to high pressure and being scraped off, and receiving unnecessary pressure to other regions.

On the other hand, it was found that the amount of lubricant on the surface of the medium was reduced by polishing the surface of the medium after applying the lubricant. Therefore, it is necessary to reapply the lubricant to an appropriate amount after the surface polishing treatment. That is, the second lubricant application suppresses the deterioration of the medium due to the insufficient lubricant amount after the surface polishing treatment.

Further, it was confirmed that the second lubricant application also has a function of removing abrasive powder on the medium generated by the surface polishing treatment. This is considered to be because the abrasive powder is washed off by the solvent when the lubricant is applied by a method such as gravure coating. Since the solvent is circulated by the pump, the polishing powder mixed in the solvent is less likely to be caught by the filter provided in the circulation system and applied again to the medium surface.

With respect to the removal of the above-mentioned polishing powder, preferably, after the surface of the medium after the surface polishing treatment is washed with an organic solvent,
Further remarkable effects can be obtained by applying the second lubricant. Cleaning of the medium surface with an organic solvent may be carried out by circulating an organic solvent such as isopropyl alcohol (IPA) in the same manner as the lubricant application by gravure coating, for example. In particular, when the first lubricant is applied after the protective layer containing carbon as a main component is formed, the effect of removing the polishing powder by the above cleaning is very large. Carbon is often used in forming a protective layer of a magnetic recording medium, and its effect is known. For example, when a carboxylic acid-based lubricant used as a lubricant of a magnetic recording medium is applied to the carbon protective layer, it is difficult for carbon to be adsorbed by a chemical bond and is physically adsorbed. Easily removed by solvent. At this time, since it is removed together with the polishing powder by the surface polishing treatment, the cleaning with the organic solvent is considered to be particularly effective.

[0018]

EXAMPLE As an example of the present invention, an application example of a magnetic recording medium having a Co—O film formed on a polymer substrate will be described together with a comparative example.

Using a web coater type continuous vapor deposition apparatus, oxygen was introduced into the vacuum vessel and Co was deposited by reactive vapor deposition.
An -O film was produced. The film thickness of the Co—O film was 200 nm. For some media, a high hardness carbon protective layer was formed by the CVD method. The thickness of the carbon protective layer was all 12 nm.

In the following, the produced magnetic recording medium was slit into a tape medium, and a VTR deck was used to apply a first lubricant, a second lubricant, a surface cleaning with an organic solvent,
The results of evaluation and examination of medium life and head clogging depending on whether or not a carbon protective layer is formed are shown.

In each medium in this study, minute protrusions having an average height of 15 nm are formed on the polymer substrate, and the medium surface after the formation of the magnetic layer reflects this shape. However, scanning tunneling microscope (ST
According to the surface observation using M), the presence of abnormal protrusions due to the aggregation of the fine protrusions is recognized as described above. In addition, only the lubricant is applied to the medium in this state and the VTR
When recording and reproducing were performed on the deck, remarkable uneven wear of the head was recognized.

In this study, the magnetic recording medium was surface-polished using a wrapping tape. As a result, head uneven wear was not observed in all media, regardless of the difference in the surface treatment conditions described below. It was also confirmed that dropouts were significantly reduced before and after the surface polishing treatment in each medium. That is, in this study, it was confirmed that the effect of the surface polishing treatment was sufficiently obtained.

In the first lubricant application and the second lubricant application, a carboxylic acid-based lubricant was applied by gravure coating. The amount of lubricant applied was controlled for each sample at the end of the second lubricant application to be optimal for use in the VTR deck used in the study. However, in the comparative example, in the case where the second lubricant application was not carried out, the VTR used for the study at the time when the first lubricant application was completed.
Controlled to be optimal for deck use. For this reason,
In these media, it is considered that the amount of lubricant is less than the optimum value due to the surface polishing treatment after applying the first lubricant.

The cleaning of the medium surface with the organic solvent was performed with isopropyl alcohol (IPA) in the same manner as the lubricant application by gravure coating.

A list of surface treatment conditions of each medium examined is shown in (Table 1). Each surface treatment is carried out in the order of forming a carbon protective layer, applying a first lubricant, polishing the surface, cleaning with an organic solvent, and applying a second lubricant, and ○ and × in (Table 1) respectively. Indicates the presence or absence of the corresponding surface treatment. Therefore, the media a, b, g, and h in (Table 1) are based on the manufacturing method having the configuration of the present invention, and the media marked with * are the comparative examples.

[0026]

[Table 1]

Next, (Table 2) shows the evaluation and examination results of the medium life and head clogging by the VTR deck of each medium shown in (Table 1). Regarding the medium life in the evaluation items, when the jitter amount or the cylinder load current exceeds the standard value, the number of times the deck has run until all running abnormalities such as audible noise are generated during running (unit:
Pass). As for the head clogging, the number of times of head clogging per fixed time after running 100 passes and 200 passes is shown as a relative value.

With respect to the medium having a medium life of 200 passes or less, the examination was continued up to 200 passes in the state where the abnormal running was recognized for the head clogging evaluation.

[0029]

[Table 2]

From (Table 2), all the media produced by the manufacturing method of the present invention have a life of 200 passes or more, while the head clogging is significantly improved as compared with the comparative example. I understand.

Further, when the media produced by the production method of the present invention are compared, the effect of cleaning with an organic solvent is more remarkable in the case where there is no carbon protective layer than in the case where there is no carbon protective layer. It is considered that this is because, as discussed in the section of action, when the carbon protective layer is present, the lubricant is easily removed together with the polishing powder by the organic solvent.

From the above results, in the medium manufactured by the manufacturing method of the present invention, while the effect of the surface polishing treatment is sufficiently exerted, it is possible to improve the medium life and head clogging which have been problems in the past. It became clear.

When the surface polishing treatment was carried out using a blade of sapphire, etc.,
The same result as above was obtained.

Further, when the same study was conducted using various lubricants other than those used in this study, the effect of the present invention was sufficiently obtained as in the above.

Further, in addition to the medium studied this time, various coating type media, metal thin film type media, tape-shaped media, and disk-shaped media were also examined in the same manner. Good enough.

[0036]

According to the present invention, the effect of the medium surface design technique by the surface polishing treatment can be sufficiently exhibited, while the medium life and head clogging, which have been problems in the past, can be improved.

Claims (3)

[Claims] 1. A method of manufacturing a magnetic recording medium in which a magnetic layer is formed on a non-magnetic substrate, wherein the surface of the magnetic layer is coated with a first lubricant directly or through a protective layer, a polishing treatment,
A method of manufacturing a magnetic recording medium, which comprises performing three treatments of applying a second lubricant, and performing the three treatments in the order described above. 2. The method for producing a magnetic recording medium according to claim 1, wherein the surface after the polishing treatment is washed with an organic solvent, and then the second lubricant is applied. 3. The method for producing a magnetic recording medium according to claim 1, wherein after the protective layer containing carbon as a main component is formed on the surface of the magnetic layer, three treatments are performed. ..