JPH02130718A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve wear resistance and CSS characteristics by providing a thermosetting coated film consisting of a thermosetting resin into which alumina and specified nonmagnetic particles are incorporated on a synthetic resin substrate and forming a magnetic recording layer on the thermosetting coated film. CONSTITUTION:The thermosetting coated film 1 consisting of the thermosetting resin into which the alumina 2 and the nonmagnetic particles 3 having <=1X10<6>OMEGAcm specific resistivity are incorporated is formed on the synthetic resin substrate 4. A Cr layer 5 as an underlying layer and a Co alloy layer 6 as the magnetic recording layer as well as a carbon layer 7 as a protective film are successively formed on the thermosetting coated film 1. Further, a lubricating layer 8 is formed on the carbon layer 7. The wear resistance and scratching resistance are enhanced in such a manner and the CSS characteristics are improved.

Description

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

[Prior Art] Conventionally, as a magnetic recording medium, one using an aluminum alloy substrate whose surface is alumite-treated or metal-plated and whose surface is mirror-polished is known.

However, in recent years, there has been a strong demand for magnetic recording media to be lightweight and easy to process, and based on these demands, synthetic resin substrates that are lighter and easier to process than aluminum alloy substrates have been proposed. However, synthetic resin substrates do not have sufficient hardness compared to aluminum alloy substrates, and therefore, magnetic recording media using synthetic resin substrates have insufficient CSS resistance, resulting in a problem of head crashes. Furthermore, synthetic resin substrates are generally insulative, and the substrate surface is charged with static electricity during handling and formation of a magnetic recording layer, which tends to cause foreign matter to adhere and cause many signal defects.

By increasing the hardness of the substrate, C3S of magnetic recording media can be improved.
As a technique for improving the characteristics and increasing the reliability, the following technique is known, which uses an aluminum alloy substrate.

■On the technical alloy substrate (An-Mg alloy) disclosed in JP-A No. 61-230618, a UV-cured film (0.1 μm ) will be established. 8. Furthermore, a sputtered magnetic film is formed as a recording layer.

The effect of this underlayer is to absorb stress during CSS and to reduce the frictional force against the head due to surface protrusions formed by fine particles, thereby preventing scratches on the magnetic film.

(2) Technique disclosed in JP-A-62-252526 This is a method of obtaining a coating of Au203 or Sin by firing. That is, AJ2 (NO
s)s 20% methanol solution, or S i (Q
Cs Hy ) A 415% methanol solution solution was coated with a tin coat, baked at 500°C for 1 hour, and a 7 μm thick Aj
A solidified film of ZOs or 5i02 is formed as a base layer. Alternatively, after forming A203, a solidified film is formed with a surface roughness R1,8 of 0.05 μm using an argon beam. A magnetic layer is provided on these bases to form a protective layer. This magnetic recording medium has no scratches on the surface of the magnetic recording medium even after 20,000 cycles of C3S, and has improved corrosion resistance.

However, the above conventional technology has the following problems.

(2) Technology disclosed in Japanese Unexamined Patent Publication No. 81-230618 The base layer made of silica and epoxy resin is an insulator and has a thin film thickness of 0.1 μm. Therefore, the substrate is required to have electrical conductivity and a hardness that is sufficiently effective for CSS resistance even with a base layer of about 0.1 μm. This substrate is limited to aluminum alloy and cannot be applied to synthetic resin substrates.

■Aj! by firing technique disclosed in JP-A-62-252526! The method for obtaining a coating of 500
Since the film formation process is required at a high temperature of °C, it cannot be applied to synthetic resin substrates at all.

[Problems to be Solved by the Invention] A synthetic resin substrate generally has insulation properties and low hardness. As a result, there have been problems in that foreign matter adhesion due to charging occurs, causing signal defects, and damage to the head occurs due to insufficient hardness in terms of C3S resistance.

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 C3S characteristics, and has excellent fidelity.

[Means for Solving the Problems] The gist of the present invention is to provide a synthetic resin substrate made of a thermosetting resin containing alumina and non-magnetic particles having a specific resistance of t x t o'Ωcm or less. A magnetic recording medium is provided with a thermosetting coating and has a magnetic recording layer on the thermosetting coating.

In the present invention, thermosetting resins include phenol resins, epoxy resins, urea resins, acrylic reaction resins, formal resins, melamine resins, etc. Also, mixtures thereof may be used.

The synthetic resin substrate used in the present invention includes polyetherimide, polyamide, polyimide, polyether sulfone, polyphenylene sulfide, etc., which have excellent heat resistance, in order to heat cure the thermosetting coating film. Among these, polyetherimide is preferred, and composite materials in which fillers such as glass fibers, carbon fibers, potassium titanate whiskers, and glass peas are added to these resins may also be used.

In the present invention, a thermosetting coating film made of a thermosetting resin containing alumina and nonmagnetic particles is formed on this synthetic resin substrate. Non-magnetic particles have a resistivity of txto
They are non-magnetic particles with a size of Ωcm or less.

Examples of non-magnetic particles include SiC and TiC.

Carbide such as CrC, BN, Si3 N4. Nitride such as TiN, TiB2. Examples include borides such as ZrBz, oxides such as 5n02, metals such as Ag and Cu, and carbon. Among these, metals whose resistance decreases significantly even in small amounts and SnO2 which is excellent in stability are preferred, and carbon is preferred because it is easy to adjust the surface roughness and disperse in the thermosetting resin. Further, the antistatic effect of the thermosetting coating film, which will be described in detail later as an effect, is such that the surface resistance of the thermosetting coating film is 10' to 10'. The effect appears at about Ω/mouth. Therefore, the specific resistance of the non-magnetic particles is I x 10'Ωcm
Anything below is sufficient.

To form a thermosetting coating, first, non-magnetic particles and a thermosetting resin are kneaded, and the thermosetting resin containing the non-magnetic particles is applied onto a synthetic resin substrate, and then subjected to a thermosetting process. All you have to do is apply. As a method for applying the thermosetting resin containing alumina and nonmagnetic particles, for example, a spin cord method is used.

The thickness of the thermosetting coating film made of alumina, nonmagnetic particles, and thermosetting resin is desirably 0.5 μm or more in order to sufficiently satisfy the hardness and antistatic effect. Further, in order to provide a suitable surface roughness (Ra of about 50 to 100), the average particle size of alumina is desirably equal to or less than the thickness of the thermosetting coating film. For example, the average particle size of alumina is 0.5 to 1.
If it is 0 μm, the surface roughness will be about Ra50 to 100λ, and adhesion between the head and the magnetic recording medium can be effectively prevented. Alumina may be spherical or crushed.

The magnetic recording layer on the thermosetting coating film is a layer that is involved in recording and reproduction, and any layer may be used as long as it has this function. For example, Co-Cr%Co-Ni-Cr, iron oxide, etc. may be used, or magnetic powder (for example, iron carbide powder, γ-Fe2
It may also be one in which O3 powder, etc.) is bonded with a resin.

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

In the present invention, a coating is provided on a synthetic resin substrate, and a thermosetting coating is used as the coating. That is, since the thermosetting resin coating is applied onto the synthetic resin substrate and cured by heat, good adhesion can be obtained between the thermosetting coating and the synthetic resin substrate. Furthermore, since curing can be performed at a much lower temperature than the high-temperature treatment such as 500°C baking described in the prior art, it is possible to form a highly hard coating without applying excessive heat to the synthetic resin substrate. It is possible.

This thermosetting coating film contains alumina. Thereby, the hardness of the synthetic resin substrate provided with the thermosetting coating can be increased. Furthermore, with this alumina,
Adjust the roughness of the surface of the magnetic recording medium to obtain an appropriate surface roughness (
50 to 100 people). If the surface roughness is set to Ra of about 50 to 100, the contact area between the head and the magnetic recording medium becomes small, and the coefficient of friction between the head and the magnetic recording medium also becomes small. This can prevent adhesion between the head and the magnetic recording medium.

Furthermore, in the present invention, non-magnetic particles having a specific resistance of lXl0'ΩCm or less are contained in the thermosetting resin so that the surface electrical resistance value of the thermosetting coating film is about 106 to 1010Ω/2 or less. Therefore, conductivity is imparted to the thermosetting coating film, and charging of the magnetic recording medium is prevented.

The surface resistance value of the thermosetting coating film varies depending on conditions such as the type of non-magnetic particles contained, the content, and the distribution within the thermosetting coating film, so it is 10' to 10'. In order to make it less than approximately Ω/mouth, the relationship between these conditions and the electrical resistance value may be determined in advance and determined as appropriate.

In the present invention, the above-described thermosetting coating film can impart sufficient hardness to the synthetic resin substrate, thereby improving C3S durability. Since it is a thermosetting coating, it has good adhesion to synthetic resin substrates, and since it prevents static electricity on synthetic resin substrates, it prevents foreign matter from adhering to the surface on which the magnetic recording layer is formed. Therefore, signal defects in the formed magnetic recording layer are significantly reduced. Furthermore, by providing the surface of the manufactured magnetic recording medium with an appropriate roughness, it is possible to prevent adhesion between the head and the recording medium during use.

[Example] Hereinafter, specific examples of the present invention will be given and explained in more detail together with the manufacturing process.

(Example 1) FIG. 1 is a cross-sectional view showing a magnetic recording medium according to an example of the present invention. In FIG. 1, 1 is a thermosetting coating film, 2 is alumina, 3 is a non-magnetic particle of SnO, , 4 is a synthetic resin substrate;
5 is a Cr layer, 6 is a Co alloy layer, 7 is a carbon layer, and 8 is a lubricating layer. The Cr layer 5 is a base layer, the co alloy layer 6 is a magnetic recording layer, and the carbon layer 7 is a protective film.

The composition of the coating material forming the thermosetting coating film 1 is as follows.

Alumina 50 plates S no=
501i parts epoxy resin
25 parts by weight Phenol resin 25 parts by weight Cyclohexanone 500 parts by weight Dispersant
After dispersing with a composition of 10 parts by weight or more using a sand mill type disperser for 10 hours, the mixture was filtered to prepare a paint. This paint was applied onto a 5.25-inch synthetic resin substrate 4 made of polyetherimide resin using a spin cord method so that the film thickness after curing would be 5 μm.

The film thickness was adjusted by changing the number of times the spin coating was spun off, overcoating, etc. Then in a clean oven for 20 minutes.
Heat treatment was performed for 2 hours at 0°C to harden the surface, and the surface roughness Ra
A thermosetting coating film 1 of lOO was obtained.

After that, 2000 Cr layers and 5800 Cr layers were formed by sputtering using a DC magnetron method.

An alloy layer 6.300 carbon layer 7 was formed.

Furthermore, a lubrication treatment using a lubricating layer 8 was performed to obtain a magnetic recording medium as an example of the present invention.

In addition to the above magnetic recording medium having a thermosetting coating 1 having a thickness of 5 μm, the thermosetting coating 1 having a thickness of 0.3 μm, 0.5 μm, 1
[mu]m magnetic recording media were prepared, and samples No. 001 to 4 were prepared in descending order of thickness. In addition, as a comparative example, a magnetic recording medium without a thermosetting coating was created. All conditions other than the thickness of the thermosetting coating film 1 are the same.

For the above samples Nos. 011 to 4 and the comparative example, signal defects were measured and CSS tests were conducted using a 3370 type head with a track width of 20 μm. The results are shown in Tables 1 and 2, respectively. Note that the thermosetting coating film may be simply referred to as a coating film below.

■Signal Defects As shown in Table 1, the comparative magnetic recording media without a coating film tend to attract foreign matter and cause signal defects due to static electricity generated on the substrate during handling and formation of the magnetic recording layer. On the other hand, sample No., which is an example of the present invention,
No signal defects were observed in magnetic recording media Nos. 1 to 4, which were extremely good.

Table 1 ■C3S test As shown in Table 2, the magnetic recording medium of the comparative example without a coating crashed after 2000 C3S cycles, whereas samples Nos. 1 to 4, which are examples of the present invention, crashed after 2000 C3S cycles. All of the magnetic recording media exhibited durability 10 times or more than that of the comparative example. Among these, sample N001 with a coating film of 0.3 μm has
When the surface was observed after 30,000 CSS cycles, scratches were found. From this result, it can be said that in order to obtain better hardness, it is desirable that the thickness of the coating film be 0.5 μm or more.

Table 2 O: No scratch, Δ: Scratch occurred, ×: Crash (Example 2) Next, an example using carbon as the non-magnetic particles will be shown. The structure is the same as that of the magnetic recording medium of Example 1 shown in FIG. 1, and in FIG. 1, 3 is a carbon particle which is a non-magnetic particle.

The composition of the coating material forming the thermosetting coating film 1 is as follows.

Alumina 75 parts by weight Carbon
10 parts by weight epoxy resin 2
5 parts by weight phenolic resin 25! i part by weight cyclohexanone 400 parts by weight dispersant
After dispersing with a ball mill type disperser for 5 hours at a composition of 21 parts or more, the mixture was filtered to prepare a paint. This paint was applied onto the same synthetic resin substrate 4 as in Example 1 using a spin code method. Adjustment of film thickness is in Example 1
The line was similar to that.

Subsequently, heat treatment was performed at 200° C. for 1 hour in a clean oven to cure the film to obtain a thermosetting coating film 1 with a surface roughness of RalOO.

Thereafter, as in Example 1, 2000 people (DCr layer 5, aOO people) were exposed using the DC magnetron method.

An alloy layer 6.300 carbon layer 7 was formed, and a lubrication treatment using a lubricant layer 8 was further performed.

The thickness of the thermosetting coating film 1 is 0.3μm%0.6μm, 1μm
Four types of samples were prepared, each having a diameter of m and a diameter of 2 μm, and named samples Nos. 005 to 8 in this order. In addition, as a comparative example, a magnetic recording medium without a thermosetting coating was created.

All conditions other than the thickness of the thermosetting coating film 1 are the same.

Tables 3 and 4 show the results of signal defect measurements and CSS tests performed on the above samples Nos. 5 to 8 and the comparative example using a 3370 type head with a track width of 20 .mu.m.

■Signal Defects As shown in Table 3, the comparative magnetic recording media without a coating film had many signal defects, whereas the magnetic recording media of samples Nos. 015 to 8, which are examples of the present invention, had no signal defects. It was not observed at all and was in very good condition.

Table 3 I can say yes.

Table 4 ■ C3S test As shown in Table 4, the magnetic recording medium of the comparative example without a coating crashed after 2000 C3S cycles, whereas samples Nos. 5 to 8, which are examples of the present invention, crashed after 2000 C3S cycles. All of the magnetic recording media exhibited durability 10 times or more than that of the comparative example. Among these, in sample No. 5 with a coating film of 0.3 μm,
When the surface was observed after 30,000 C3S cycles, scratches were found. From this result, it is desirable that the thickness of the coating film be 0.6 μm or more in order to obtain better hardness. ] The present invention has various effects described below.

■Thermosetting coatings are formed by applying them in the paint state and then curing them, so they have excellent adhesion to synthetic resin substrates and good flatness. Further, high hardness can be imparted to the synthetic resin substrate without applying excessive heat as in baking. As a result, it has excellent abrasion resistance and scratch resistance, and
It becomes possible to realize a magnetic recording medium using a synthetic resin substrate with excellent 3S characteristics.

(2) It is possible to provide a magnetic recording medium that can have an appropriate roughness on its surface and prevent adhesion to the head.

■Conductivity is imparted by incorporating inorganic non-magnetic particles with a specific resistance of 6 x 10'Ωcm into the thermosetting coating, which prevents static electricity from being charged due to friction, attracts dust, and prevents signal defects. It is possible to solve the problem of generation, which is unique to the use of synthetic resin substrates.

(2) In the present invention, since alumina imparts high hardness to the synthetic resin substrate, any hardness can be used as the nonmagnetic particles for imparting conductivity. For example, even materials with low hardness such as carbon can be used as non-magnetic particles.

Due to the various effects described above, the reliability and practicality of a magnetic recording medium using a synthetic resin substrate can be easily improved at low cost.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing a magnetic recording medium according to an embodiment of the present invention. 1... Thermosetting coating film, 2... Alumina, 3... Non-magnetic particles, 4... Synthetic resin substrate, 5... Cr layer,
6...CO alloy layer, 7...carbon layer, 8...lubricating layer. Patent applicant: Sekisui Chemical Co., Ltd. Representative Hiroshi 1) Kaoru

Claims (1)

[Claims] A thermosetting coating film made of a thermosetting resin containing alumina and non-magnetic particles having a resistivity of 1×10^5 Ωcm or less is provided on a synthetic resin substrate,
A magnetic recording medium comprising a magnetic recording layer on the thermosetting coating film.