JPH03137821A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve CSS resistance characteristics and to additionally improve recording characteristics when a texturing treatment is executed by constituting the magnetic recording medium, for which a synthetic resin base body is used, of a magnetic recording layer which is formed on the base body and is provided with concentrical grooves on the surface and fine particles packed in the grooves. CONSTITUTION:The substrate 4 made of the synthetic resin, such as, for example, acrylic system, polycarbonate system or polyimide system, is used as the substrate and the square grooves 1 having 0.2mum depth and 0.4mum width are provided on this surface layer part while inter-groove intervals 3 are specified at 25mum. The grooves 1 are circumferentially turned in the surface layer part of the substrate 4. The parts exclusive of the grooves 1 are subjected to the texturing treatment, by which the circumferential fine ruggedness of 5nm average surface roughness is formed. The magnetic recording layer 6 consisting of a Cr underlying layer, a Co-Ni-Cr magnetic layer and a protective layer are provided on the surface layer part of the substrate 4 enclosing the grooves 1 and alumina particles 5 of a regulated projecting height 8 and 0.3mum grain size are packed into the grooves 1 while the particles are solidified by a binder 7 consisting of an epoxy resin.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a magnetic recording medium, and more particularly to a magnetic recording medium using a synthetic resin substrate as the substrate.

[Prior Art] In recent years, studies have been made to use synthetic resin substrates as substrates for magnetic recording media. This is because synthetic resin substrates are lighter than aluminum alloy substrates, more resistant to impact, and easier to process. In the synthetic resin base, the hardness of the base surface is improved to provide sufficient C.
In order to obtain SS characteristics and scratch resistance, attempts have been made to form a highly hard coating on the surface of the substrate. Conventionally, the following synthetic resin substrates having a highly hard coating formed on their surfaces have been known, for example.

■Technology disclosed in JP-A No. 59-213025 This uses a mixed composition of ABS resin and/or MBS resin and polycarbonate resin as the synthetic resin forming the base, and an alloy containing N1-P as the main component. A film is formed on the synthetic resin substrate by a wet plating method.

That is, by using a mixed composition of ABS resin or the like and polycarbonate resin as the synthetic resin that forms the base, the N1-P alloy coating, which has been known for a long time as a coating for improving the surface hardness of aluminum alloy bases, can be formed. This makes it possible to use it as a surface coating.

The alloy film containing N1-P as a main component has characteristics such as being highly hard and non-magnetic, and being wet-plated with excellent mass productivity.

(2) Technique disclosed in JP-A-61-187117 This is a technique in which a coating of Ti or a Ti compound is formed on the surface of a synthetic resin substrate using an ion-blating method. Such a method can also improve the hardness and roughness of the substrate surface.

[Problem B to be solved by the invention] However, in the conventional magnetic recording medium substrate as described above,
The following issues were encountered.

■The technology disclosed in Japanese Patent Application Laid-open No. 59-213025 has a technique in which the resin used to form the base is ABS resin and/or
Alternatively, since the composition is limited to a mixed composition of MBS resin and polycarbonate resin, there is a problem in that the use of resins with better moldability or resins with better heat resistance is restricted.

In addition, when ABS resin is mixed as a substrate raw material, the heat resistance of the substrate decreases, so there is a problem that it is difficult to use a method that requires heat resistance such as sputtering when forming a recording film. .

Furthermore, in this magnetic recording medium dormant substrate, the surface of the substrate is roughened during the formation of the plating layer to improve the adhesion between the substrate and the plating layer, but the adhesion obtained by this method is insufficient for magnetic recording. It cannot be said that this is sufficient for practical use as a recording medium, and improvements in adhesion have been desired.

■The technology shown in JP-A No. 61-187117 requires the formation of a Ti or Ti compound coating of several micrometers in order to obtain the necessary hardness when used as a magnetic recording medium. Forming a film using the ion blasting method requires a very long time, which poses a problem in that it causes high costs. Further, there is also a problem in that the resin magnetic recording substrate is subjected to considerable thermal damage during film formation, which may cause deformation of the substrate.

In addition, in the above techniques (1) and (2), texturing processing was sometimes performed to improve the magnetic recording characteristics and CSS resistance characteristics of the magnetic recording medium. Since the optimal shape and the optimal shape for texturing for improving C5S resistance characteristics are different, there is also the problem that a compromise between the two must be adopted.

The present invention has been made in view of the problems of the prior art as described above, and has been developed to provide CS resistance without impairing heat resistance or adhesion.
The object of the present invention is to provide a magnetic recording medium with improved S characteristics and scratch resistance.

[Means for Solving the Problems] The gist of the present invention is to provide a synthetic resin substrate; a magnetic recording layer formed on the synthetic resin substrate and having concentric grooves formed on its surface; The configuration of the present invention will be described in detail below.

(Synthetic resin base) As the synthetic resin base used in the present invention, for example, one formed of one or a mixed resin of two or more of acrylic, polycarbonate, polyimide, and epoxy resins can be used. be. It may also contain fillers such as glass fibers and alumina particles.

(Groove) In the present invention, a groove is formed on the surface of the synthetic resin substrate. Here, the grooves are formed concentrically for the following reason.

In the magnetic recording medium of the present invention, magnetic recording cannot be performed on the portion of the recording surface of the 6Ti recording medium where the grooves are formed. Therefore, in order to obtain the effects of the present invention while maintaining recording performance, it is necessary to minimize the number of intersections between the groove and the portion of the recording surface of the magnetic recording medium where the magnetic head runs (i.e., the portion where recording is performed). It's better. Here, if the grooves are formed concentrically, the number of intersections between the groove and the portion on which the magnetic head runs can be suppressed to a number that does not pose a problem in use. Therefore, it is most desirable that the grooves be formed in concentric circles.

In the present invention, since a synthetic resin substrate is used as the substrate, it is extremely easy to form the grooves. This is because when molding a synthetic resin substrate using a molding method such as injection molding or compression molding, it is sufficient to process the mold so that a synthetic resin substrate with grooves on the surface is molded. It is.

Of course, it is also possible to form the synthetic resin substrate using an ordinary mirror mold and then form the grooves using a stand bar such as that used in manufacturing optical disk substrates.

The cross-sectional shape of the groove may be any shape as long as it can hold the particles to be filled in the groove. The cross-sectional shapes of the grooves include, for example, rectangular, inverted triangular, and semicircular shapes as shown in FIGS. 1(a) to (C), but are not limited to these shapes.

“If the grooves of the magnetic recording layer are formed by forming the magnetic recording layer on a synthetic resin substrate having grooves on the surface, the width of the grooves must be slightly wider than the particle size of the fine particles. This is because the grooves formed in the magnetic recording layer are slightly narrower than the grooves in the synthetic resin substrate.According to the studies of the present inventors, the width of the grooves in the synthetic resin substrate is - It is most desirable that it be about 10 to 20% wider than the width.

The depth of the groove is desirably set so that the apex of the fine particles protrudes from the surface of the magnetic recording medium by 0.05 to 0.15 μm. For example, for a groove with a square cross section, the diameter is 0.
．． When using 3μm particles, the groove depth is 0.15~
It is desirable to set the thickness to 0.25 μm. This is because if the protrusion of the particles is less than 0.05 μm, the particles wear quickly, making it difficult to maintain C3S resistance over a long period of time. This is because it becomes large, making it impossible to achieve high-density recording.

The interval between the grooves is preferably 10 to 100 μm.

The reason why it is set to 10 μm or more is because magnetic recording cannot be performed in the groove portion, and if the groove interval is less than 10 μm, the recording performance as a magnetic recording medium will deteriorate.
The reason why the groove spacing is set to 0 μm or less is that if the groove spacing exceeds 100 μm, long-term C3S resistance performance cannot be exhibited.

(Magnetic Recording Layer) In the present invention, the magnetic recording layer may be formed of only a magnetic layer, or may have an underlayer or a protective layer. Further, the material, film thickness, formation method, etc. of the magnetic recording layer are not particularly limited. For example, examples of the magnetic layer forming material include Co-Cr, Co-Ni-Cr,
Iron oxide etc. can be used. Further, as a method for forming the magnetic layer, for example, a vacuum evaporation method, a sputtering method, an ion blasting method, a plating method, etc. can be used.

(Fine Particles) As the fine particles used in the present invention, it is desirable to use particles that are non-magnetic, have high hardness, and have high wear resistance.

As the material for forming the fine particles, for example, alumina, titanium oxide, silicon carbide, boron nitride, etc. can be used.

Further, the particle size of the fine particles is preferably 0.2 to 1 μm. This is because if the particle size is less than 0.2 μm, the particles will wear out quickly, making it difficult to maintain CSS resistance over a long period of time, and if it is larger than 1 μm, the groove width must be widened, resulting in a decline in recording performance. It is.

As a method for filling the grooves of the magnetic recording layer with fine particles, for example, there is a method of applying a paint consisting of fine particles, a small amount of binder resin, and a solvent onto the magnetic disk medium using a coating machine such as a spin coater. Available for use. After drying and curing the coating film, a puff finish is applied to remove excess particles, thereby making it possible to obtain a magnetic disk medium with a surface condition as shown in FIG. 3. The reason for using the binder resin here is to fix the fine particles to the grooves. The binder resin may be used in a small amount, and it is preferable to use a thermosetting resin or the like. Incidentally, in order to further improve the C5S resistance performance, a lubricant may be further applied to the surface of this magnetic disk medium.

[Function] The present invention improves C8S resistance and scratch resistance by forming grooves in the magnetic recording layer and filling the grooves with fine particles.

Furthermore, according to the present invention, since the C3S resistance characteristics can be improved by this method, when performing the above-mentioned texturing treatment, it is possible to obtain the optimum shape for improving the magnetic recording characteristics. Therefore, it is also possible to improve the magnetic recording characteristics.

The present invention will be explained in detail below.

The inventor of the present invention has conducted intensive studies on techniques for improving the CSS resistance and scratch resistance of magnetic recording media, and has found the following results:
When a coating film contains alumina particles in a coated magnetic recording medium, the alumina particles on the surface of the coating film act to prevent adhesion between the magnetic recording medium and the magnetic head, reducing the frictional force. It has been found that the C3S characteristics are improved as a result.

Therefore, the inventors of the present invention have been conducting intensive studies on technology that allows alumina particles to play a role in improving CSS resistance performance even in magnetic recording layer media in which the magnetic recording layer is formed using vacuum evaporation, sputtering, etc. I did it.

However, it was concluded that in the case of magnetic recording media using vacuum evaporation or sputtering, it is virtually impossible to fix alumina particles to the surface of the electromagnetic recording layer. In addition, there is a recent demand for higher recording density on magnetic recording media, and to meet this demand it is necessary to lower the flying height of the magnetic head, which requires extremely fine alumina particles. It was also found that such ultrafine alumina particles are extremely difficult to obtain.

In order to solve these problems, the present inventor attempted to form a coating film containing alumina particles as a base layer, but it was found that in this case, little contribution to improvement of C5S resistance performance could be expected. I understand. In other words, if no alumina particles are exposed on the surface of the magnetic disk medium, C
It is essential to improve the 8S characteristics.

Next, the present inventor investigated a case in which alumina particles were arranged randomly throughout the magnetic recording layer, but it was found that in this case, the magnetic recording performance deteriorated significantly.

Furthermore, based on these findings, the present inventors investigated the case where grooves were formed in the magnetic recording layer and filled with alumina particles, and as a result, they concluded that this method was useful, and further As a result of repeated studies, the present invention was completed.

[Example] Hereinafter, the present invention will be described in more detail using Examples and Examples of the present invention.

As an example of the present invention, a magnetic recording medium was formed as follows.

(2) As the substrate, a polyetherimide substrate with grooves formed by injection molding was used.

The cross-sectional shape of the groove on the substrate is 0.2 μm deep and 0.4 μm wide.
It was made into a square. The grooves were circumferential, and the interval between the grooves was 25 μm. In addition, on the surface of the magnetic recording layer other than the grooves, texturing treatment was performed to increase the average roughness in the radial direction to 5
A fine circumferential unevenness of nm size was provided.

■A 200 nm Cr underlayer is applied to this substrate.

Co-Ni-Cr magnetic layer (Co:Ni:Cr=75
:15:10) 80 nm, C protective layer 30 nm, D, C
, and were sequentially formed using a magnetron sputtering device to form a magnetic recording layer.

■Furthermore, 100 grams of alumina particles with a particle size of 0.3 μm and an epoxy resin binder 5 are added to the surface of this magnetic recording layer.
gram and 100 grams of solvent was applied by spray method.

(2) Thereafter, drying and curing was performed using a hot air dryer at 170 degrees.

(2) Next, excess alumina particles were removed using a tape polisher.

(2) Finally, a fluorine-based lubricant was applied by dipping to obtain the magnetic disk medium of the present invention.

A C3S test was conducted on the magnetic recording medium of this example obtained through the above steps, and an increase in the coefficient of dynamic friction was measured. For comparison, magnetic recording media prepared using a rietherimide substrate without any grooves and following the same steps as in (1) to (2) above were also evaluated.

The results of these evaluations are shown in Table 1.

In addition, for this C3S test, Track I! A mini monolithic type head with a diameter of 24 μm and a load of 9.5 g was used.

Table 1 As is clear from the evaluation results shown in Table 1, the magnetic recording medium of this example was able to significantly improve the coefficient of dynamic friction compared to the conventional one.

Next, a CSS test was conducted using the magnetic recording medium of this example, and an increase in the coefficient of static friction was measured. Also, for comparison,
Similar evaluation tests were also conducted for the conventional magnetic recording media as described above. Table 2 shows these evaluation results.

The wood CSS test also used a 3370 type mini monolithic type head with a track width of 24 μm and a load of 9.5 g, as in the evaluation test for the coefficient of dynamic friction.

Table 2 As is clear from the evaluation results shown in Table 2, the magnetic recording medium of this example was able to significantly improve the coefficient of static friction compared to the conventional one.

[Effects of the Invention] As described above in detail, according to the present invention, it is possible to obtain a magnetic recording medium with improved wear resistance and, in turn, improved CSS resistance.

Furthermore, according to the present invention, magnetic recording characteristics can also be improved by performing texturing processing.

[Brief explanation of the drawing]

FIGS. 1(a) to 1(c) are diagrams showing examples of cross-sectional shapes of grooves in a magnetic recording medium according to the present invention. FIG. 2 is a schematic cross-sectional view showing a state in which grooves are filled with fine particles in the magnetic recording medium of the present invention. FIG. 3 is a schematic perspective view showing a state in which grooves are filled with fine particles in the magnetic recording medium of the present invention. (Explanation of symbols)

Claims (7)

[Claims] (1) A synthetic resin substrate; a magnetic recording layer formed on the synthetic resin substrate and having concentric grooves formed on its surface; and fine particles filled in the grooves. magnetic recording medium (2) The magnetic structure according to claim 1, wherein the synthetic resin substrate has a groove, and the groove is formed in the magnetic recording layer by forming the magnetic recording layer on the synthetic resin substrate. recoding media (3) The magnetic recording medium according to claim 2, wherein the width of the groove of the synthetic resin base is 10 to 20% larger than the width of the fine particles. (4) The magnetic recording medium according to any one of claims 1 to 3, wherein the depth of the groove formed in the magnetic recording layer is 0.05 to 0.15 μm smaller than the particle size of the fine particles. (5) The interval between the grooves formed in the magnetic recording layer is 1
The magnetic recording medium according to any one of claims 1 to 4, characterized in that the magnetic recording medium has a diameter of 0 to 100 μm. (6) The magnetic recording medium according to any one of claims 1 to 5, wherein the particle size of the fine particles is 0.2 to 1 μm. (7) The magnetic recording medium according to any one of claims 1 to 6, wherein a texturing process is performed on a portion of the surface of the magnetic recording layer where the groove is not formed.