JPH0294111A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve wear resistance and scratching resistance and to obviate sticking of dust by static electricity by forming a photosetting coated film consisting of a specific photosetting resin on a synthetic resin substrate. CONSTITUTION:A film is provided on the resin substrate and since the photosetting coated film is used as the film thereof, a good adhesive property is obtd. between the photosetting coated film and the synthetic resin substrate. Further, carbon is incorporated into the photosetting resin so as to obtain <=10<9> ohms/square surface electric resistance value of the photosetting coated film and, therefore, an electrical conductivity is imparted to the photosetting coated film and the electrification of the magnetic recording medium is prevented. The wear resistance and scratching resistance are improved in this way and the generation of static electricity by friction, etc., and eventually the adsorption of dust, etc., are obviated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a magnetic recording medium, and particularly to a magnetic recording medium using a synthetic resin substrate and having excellent CSS characteristics.

[Prior Art] (Technical Background) Conventionally, magnetic recording media have been known to use magnetic disk substrates made of aluminum alloy substrates whose surfaces are alumite-treated or metal-plated, and whose surfaces are mirror-polished. There is.

However, in recent years, there has been a strong demand for magnetic recording media to be lighter and easier to process, and based on these demands, synthetic resin substrates that are lighter and easier to process than aluminum alloy substrates have been proposed. There is. However, synthetic resin substrates do not have sufficient hardness compared to aluminum alloy substrates, and as a result, the CSS characteristics of magnetic recording media using synthetic resin substrates are insufficient. Therefore, magnetic recording media having sufficient C8S characteristics are being sought, and several attempts have been made.

(Latest prior art) As one of the above attempts, Ti, T
A magnetic disk substrate in which a film of i-alloy or T1 compound is formed by means such as ion blasting has been proposed (Japanese Patent Application Laid-open No. 187117/1983).

Note that as a technique for increasing the hardness, improving the CSS characteristics of a magnetic recording medium, and increasing its reliability, the following technique is known, although one uses an aluminum alloy substrate.

■Thickness 5 to 2 with basic composition of N1-P alloy on the substrate
A technology that applies a 0 μm film using methods such as wet plating.

■By applying a methanol solution of aluminum nitrate on the substrate and baking it at high temperature, Al2O2 is formed on the substrate.
(Japanese Unexamined Patent Publication No. 62-252526).

[Invention or problem to be solved] However, the above conventional technology has the following problems.

■Disclosed in Japanese Patent Application Laid-open No. 187117/1983,
With the technique of forming a film of T1, T1 alloy, or TI compound on a synthetic resin substrate, it is extremely difficult to obtain a sufficient film thickness. Roughly Ti, Ti alloy or T
Since a single compound coating has poor adhesion to a synthetic resin substrate, there is a problem in that an intermediate layer such as silicon oxide must be provided, and even if an intermediate layer such as silicon oxide is provided, it does not necessarily have sufficient hardness. Therefore, sufficient CSS characteristics may not be obtained.

Furthermore, in the above-mentioned conventional technology using a synthetic resin substrate, static electricity is easily generated due to friction, etc., and dust in the air is attracted onto the magnetic disk substrate. If dust adheres to the surface of the magnetic disk substrate before forming the magnetic recording layer on the magnetic disk substrate, it may cause signal defects in the magnetic recording layer formed thereafter. This dust is not easy to remove and significantly degrades the performance of the magnetic recording medium.

■When applying the method of improving the substrate hardness by N1-P plating to a synthetic resin substrate, the plating layer and the synthetic resin substrate have poor adhesion, so peeling occurs at the interface, which causes practical problems. Difficult to use. Further, an alloy film having a basic composition of N1-P becomes more likely to have magnetism due to a slight change in composition, and such magnetism may impair the performance as a magnetic recording medium.

■The method of obtaining Aj2203 coating by firing, which is disclosed in JP-A-62-252526, is
Since the film formation process is required at a high temperature of °C, it cannot be applied to synthetic resin substrates at all.

An object of the present invention is to solve the above problems and provide a magnetic recording medium using a synthetic resin substrate, which has excellent wear resistance and scratch resistance, and does not attract dust due to static electricity, and
Another object of the present invention is to provide a magnetic recording medium that is lightweight, inexpensive, has excellent C5S characteristics, and has excellent reliability.

[Means for Solving the Problems] The gist of the present invention is to provide a synthetic resin substrate with an electric resistance value of 1.
A magnetic device comprising: a photocurable coating film made of a photocurable resin containing carbon such that the resistance is 0.09 Ω/min or less; and a magnetic recording layer is provided on the photocurable coating film. Exists on a recording medium.

Examples of the synthetic resin substrate used in the present invention include:
Substrates made of synthetic resins such as acrylic, polycarbonate, polyimide, and epoxy resins can be used. Examples include substrates made of resins such as polyetherimide, polyethersulfone, polyphenylene sulfide, polyarylate, polycarbonate, polyimide, and polyetherketone. Furthermore, if necessary,
Inorganic fillers such as glass fibers and alumina particles may be appropriately added to the synthetic resin. Note that the substrate made of synthetic resin may have a multilayer structure of two or more layers.

In the present invention, a photocurable coating film made of a photocurable resin is formed on this synthetic resin substrate, and this photocurable coating film is
Carbon is contained so that the electrical resistance value is 10 9 Ω/mouth or less.

The electrical resistance value varies depending on the carbon content contained, the distribution situation within the photocurable coating film, etc.
In order to set the resistance to 9Ω/mouth or less, the relationship between these values and the electrical resistance value may be determined in advance and determined as appropriate. - For boat fishing, the content may be 50 to 150 parts by weight per 100 parts by weight of the photocurable resin.

As a method for forming a photocurable coating film, for example, a dip method, a spray method, a spin coating method, and other methods can be used.

The thickness of the photocurable coating film is preferably 2 to 20 μm, more preferably 5 to 10 μm.

Examples of the photocurable resin include dipentaerythritol hexaacrylate, tetramethylolmethane triacrylate, tetramethylolmethanetetraacrylate, or mixtures thereof.

The form of carbon is not particularly limited, and may be, for example, powder, granules, scales, fibers (including whiskers), or lumps. Further, the distribution within the film is not particularly limited either, but it is preferable to have a high density near the surface. Furthermore, a portion thereof may be exposed on the surface.

In order to maintain the planar smoothness of the magnetic recording medium, this carbon should be in the form of particles with a diameter of 05 μm or less, or in the form of particles with a diameter of 1 μm.
It is desirable to have a scale-like shape with a thickness of 0.3 μm or less and a thickness of 0.3 μm or less.

Note that fine irregularities may be provided concentrically from the center on the surface of the photocurable coating film after curing by a method such as tape polishing.

In addition, corona discharge,
Treatment such as plasma irradiation may also be performed.

The magnetic recording layer on the photocurable coating film is a layer involved in recording and reproduction, and any layer may be used as long as it exhibits this function. For example, Co-Cr.

It may be made of Co-Ni-Cr, iron oxide, chromium oxide, etc., or it may be made of magnetic powder (for example, iron carbide powder, γFe2O3 powder, etc.) bonded with a resin. Note that a base film (for example, a Cr film) may be interposed between the photocurable coating film and the magnetic recording layer.

[Work] The present invention will be explained in detail below.

In the present invention, a coating is provided on a resin substrate and a photocurable coating is used as the coating (that is, a photocurable resin coating is applied onto a synthetic resin substrate and cured by light). It is possible to obtain good adhesion between the curable coating film and the synthetic resin substrate. Furthermore, since curing can be performed with light, it is possible to form a highly hard coating without applying excessive heat to the synthetic resin substrate.

Furthermore, in the present invention, since carbon is contained in the photocurable resin so that the surface electrical resistance value of the photocurable coating film is 109Ω/or less, the photocurable coating film has electrical conductivity. This prevents the magnetic recording medium from being charged.

In addition, when the film thickness of the photocurable coating film is 2 to 20 μm, the hardness becomes even higher, and when the film thickness is 5 to 10 μm, the hardness becomes even higher, and the C5S properties are further improved. do.

By creating fine irregularities concentrically from the center on the surface of the photocurable coating film after curing using a method such as tape polishing, it is possible to obtain a magnetic recording medium that is less prone to attracting magnetic heads. The adhesion between the magnetic coating film and the magnetic recording layer (or the photocurable coating film and the base layer if an underlayer is provided between the photocurable coating film and the magnetic recording layer) is also improved.

In addition, corona discharge,
By performing a treatment such as plasma irradiation, the photocurable coating film and the magnetic recording layer (if a base layer is provided between the photocurable coating film and the magnetic recording layer, the photocurable coating film and the magnetic recording layer) base layer)
It is possible to further improve the adhesion with.

[Example] Examples of the present invention will be described below along with manufacturing steps.

First, to 100 parts by weight of a photocurable oligomer consisting of a mixture of tetramethylolmethane triacrylate and tetramethylolmethanetetraacrylate (weight ratio 84:16), 5 parts by weight of photopolymerization initiator benzophenone and methyl methacrylate-1-hydroxy A photocurable paint consisting of 20 parts by weight of ethyl methacrylate copolymer and 100 parts by weight of carbon powder having a particle size of 0.3 μm was prepared using a sand mill type dispersing machine using methyl ethyl ketone and ethyl cellosolve as diluents. This paint was applied onto a 5.25-inch resin substrate 3 made of polyetherimide using a spin cord method so that the film thickness after drying and curing would be 10 μm.

After applying the photocurable paint, the diluent was removed by drying it for 30 minutes using a hot air dryer at 60°C, and then the paint was irradiated with a light beam of 50 J/cm2 using a mercury lamp. A magnetic disk substrate was obtained by curing to form a photocurable coating film.

In this example, after curing, the photocurable coating film was given concentric fine irregularities with a polishing tape using a tape polisher. At this time, the surface roughness of the magnetic disk substrate in the radial direction was 8 nm. Further, the surface electrical resistance of this magnetic disk substrate was 2×10 −7 Ω/hole.

For the magnetic disk substrate obtained through the above steps, Cr
The underlayer was 200 nm thick, and the Co-NiCr 6m recording layer (Co+Ni:Cr=7515:10) was 80 nm thick.
A carphone protective layer was sequentially formed to a thickness of 30 nm using a D and C magnetron sputtering apparatus to obtain a magnetic recording medium according to the present invention. The surface of this magnetic recording medium was lubricated with a fluororesin lubricant.

A CSS test was conducted on this 6n recording medium to measure the decrease in reproduction output. The results are shown in Table 1. For comparison, the evaluation results of a conventional magnetic recording medium in which the same underlayer, magnetic recording layer, and protective layer as in the above example were provided on a resin substrate without a photocurable coating and were subjected to lubrication treatment are also listed. do.

For CSS test, track width 24μm 1 load 9.5g 3
A 370 type mini monolithic type head was used.

Table 1 As is clear from Table 1, in the conventional magnetic recording medium, the output has already decreased by 5% after 10,000 CSS cycles, whereas the output of the magnetic recording medium according to the present invention has already decreased by 5% after 10,000 CSS cycles.
No decrease in output occurred even after 40,000 cycles, and a 5% decrease in output was finally measured after 40,000 cycles. That is, in the magnetic recording medium according to the present invention, the CSS durability is significantly improved, and the durability can be several times higher than that of the conventional magnetic recording medium.

Further, Table 2 shows the results of measuring the number of signal defects of the above two types of magnetic recording media.

It is possible to provide Table 2, and the flatness of the substrate is good.

■Containing carphone in the photocurable coating gives it conductivity, which eliminates the unique problems that occur when using synthetic resin substrates, such as the generation of static electricity due to friction, etc., and the adsorption of dust. It can be solved.

(2) It is possible to realize a magnetic recording medium using a synthetic resin substrate that has excellent wear resistance, scratch resistance, and CSS characteristics.

As is clear from Table 2, the magnetic recording medium according to the present invention can effectively eliminate static electricity charging and does not cause any dust build-up, so it completely eliminates the occurrence of signal defects caused by this. It can be prevented.

[Effect of the invention] The present invention provides various effects described below.

■Because it forms a photocurable coating film, it has high hardness without applying excessive heat to the synthetic resin substrate Patent applicant Hiroshi, Representative of Sekisui Chemical Co., Ltd. 1) Kaoru

Claims (1)

[Claims] A photocurable coating film made of a photocurable resin containing carbon is formed on a synthetic resin substrate so that the electrical resistance value is 10^9Ω/mouth or less, and a magnetic layer is applied on the photocurable coating film. A magnetic recording medium characterized by having a recording layer.