JPS6220131A - Magnetic disk - Google Patents

Abstract

PURPOSE:To reduce weight so as to reduce the electric power consumption of a disk drive device and to improve durability and SN ratio by using a high- rigidity heat-resistant resin substrate for a substrate and using a resin curable by electron rays as a binder for a magnetic coated film. CONSTITUTION:This magnetic disk is formed by forming the magnetic coated film consisting of magnetic powder and the resin curable by electron rays on the high-rigidity heat-resistant resin substrate and curing the magnetic coated film by the irradiation of electron rays. A polyether imide, etc. are adequate for the substrate material. On the other hand, the resin curable by electron rays to be used as the binder for the magnetic layer has preferably a low viscosity and is preferably hard when cured. The phenol novolak epoxy acrylate or methacrythate expressed by the formula, etc. are used for such resin curable by electron rays. (In the formula, n denotes an integer, R1 denotes -H, -CH3, etc. and R2 denotes -H, -CH3, -Br, -Cl, etc.).

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a magnetic disk used as a storage medium in a magnetic storage device such as a magnetic disk device. The present invention relates to a so-called coated magnetic disk in which a magnetic layer is formed by coating.

[Summary of the invention]

The present invention aims to reduce the weight and power consumption of disk drive devices by using a high-rigidity, heat-resistant resin substrate for the substrate in a magnetic disk in which a magnetic layer is formed by applying magnetic powder together with a resin binder. At the same time, by using an electron beam curable resin as a binder for the magnetic coating, it is intended to improve durability and the signal-to-noise ratio.

[Conventional technology]

For example, disk-shaped magnetic disks that can be randomly accessed are widely used as storage media in combinators, etc., and among them, they have excellent responsiveness, large storage capacity, good storage stability, and reliability. Because of the high magnetic flux, magnetic disks whose substrates are made of hard materials such as A1 alloy plates, glass plates, plastic plates, etc., so-called hard disks, are now being used as fixed disks or external disks.

The hard disk has, for example, an A1 alloy substrate on which a magnetic layer involved in recording and reproduction is formed, and rotates at high speed to record and reproduce information on a large number of concentric tracks.

In this type of magnetic disk, an Al plate is used as the substrate material for -C, and a thermosetting resin is used as a resin binder in order to give strength to the magnetic disk coating film, which is the magnetic layer. In order to harden the thermosetting resin, baking is performed for several hours under curing conditions of 200° C. to 300° C. to form a magnetic layer.

[Problem that the invention seeks to solve]

By the way, for magnetic disks that use Al plates as substrates, (1) it is necessary to perform polishing processes such as diamond turn processing and grind polishing in order to obtain surface smoothness;
The number of steps increases and manufacturing costs also increase.

(ii) Since the specific gravity is heavy at about 2.7, the power consumption of the spindle motor for driving the disk is large, and the power consumption of the disk drive device or system is large.

(iii) A: Since the small amount of iron contained in the plate has magnetism, it becomes a major cause of noise generation during recording and reproduction.

It has the following drawbacks.

Alternatively, it is possible to use a resin substrate instead of the Ae substrate, but in this case, if high temperature baking is performed to harden the magnetic layer, there is a risk that the disk will be deformed. Furthermore, if the disk is cured for a long time at a low temperature that does not affect the shape of the disk, the cure will be insufficient and the surface durability will be poor.

Therefore, the present invention was proposed in order to eliminate the drawbacks of the above-mentioned conventional devices, and provides a magnetic disk that is lightweight, can reduce power consumption of the drive device, has excellent durability, and has low noise. Further, it is an object of the present invention to provide a magnetic disk in which the magnetic layer can be made thinner and the recording density can be improved.

[Means for solving problems]

In order to achieve the above object, the present invention provides a method in which a magnetic coating film made of magnetic powder and an electron beam curable resin is formed on a highly rigid heat-resistant resin substrate, and the magnetic coating film is cured by electron beam irradiation. It is characterized by the presence of

In the magnetic disk of the present invention, a highly rigid heat-resistant resin substrate is used as the substrate, but this substrate material is required to satisfy the following requirements.

In other words, (a) Distance from the clamp point on the inner circumference of the disk to the outer circumference of the disk! , when the thickness of the disk is d,
d/1>0.022.

(b) The heat distortion temperature is 120°C or higher.

(,c) The coefficient of thermal expansion is 7. It must be less than Ox l O-'7°C.

(d) Young's modulus is 240 k+r/+++m'' or more.

etc. For example, if the conditions (a) and (d) above are not met, the outer peripheral edge of the disk may become curved due to its own weight. Alternatively, unless the conditions (b) and (c) are met, the reproducibility of recording cannot be maintained.
The quality of the magnetic disk becomes insufficient.

From this viewpoint, polyetherimide, polycarbonate, polysulfone, polyethersulfone, polyacecool, polyphenylene sulfide, etc. are suitable as the substrate material for the magnetic disk of the present invention.

On the other hand, the electron beam curable resin used as the binder for the magnetic layer in the present invention preferably has a low viscosity so that the magnetic paint can be applied well, and is preferably hard when cured. Examples of such electron beam curable resins include the following.

(1) Formula (where n represents an integer, R1 represents -H, -CR3, etc., and R2 represents -H, -CH3, -Br.

- represents Cβ, etc. ) Phenol noboranoqueepoxoacrylate or methacrylate.

(2) Formula (wherein n represents an integer, R1 represents -H1 to CH3, etc., and R2 represents -H, CHy, Br.

- Represents C1 etc. ) Bisphenol A type epoxy acrylate or methacrylate.

(3) Alicyclic epoxy acrylate or methacrylate represented by (wherein, R1 represents -H, -CHff, etc., and R1 represents a divalent hydrocarbon group).

The above-mentioned epoxy acrylate or epoxy methacrylate preferably has a molecular weight of 400 to 5,000. If this molecular weight is too large, there is a risk that the strength upon curing will be insufficient. Further, the unsaturated bond equivalent per molecule is preferably within the range of 150 to 3,000.

These epoxy acrylates or epoxy methacrylates also contain polyfunctional acrylates (2
functional to hexafunctional) may be used in combination.

The above polyfunctional 7-acrylate (or methacrylate)
For example, oligoester acrylate (for example, manufactured by Toagosei Co., Ltd., M8060.M8030°M7100.M81
00), trimethylolpropane triacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, dipentaerythritol hexaacrylate, tetrahydrofuryl acrylate,
etc. In addition, as the above-mentioned bifunctional acrylate (or methacrylate), Examples include pentyl glycol diacrylate, and the product name is Viscoat #3700. #700 (manufactured by Osaka Fuki Co., Ltd.), product name MANDA (manufactured by Nippon Kapowder Co., Ltd.), and product name Aronifukus M6100. M6200. M6250゜M6300
．． M65QO (manufactured by Toagosei Co., Ltd.) and the like are commercially available. Furthermore, as the monofunctional acrylate (or methacrylate), hydroxyethyl acrylate, hydroxyethyl methacrylate, and product name HOA-MPE (
(manufactured by Kyoei Co., Ltd.), and Aroninox M'5700 (trade name, manufactured by Toagosei Co., Ltd.).

Coating films made of these epoxy acrylates or epoxy methacrylates are much harder than ordinary electron beam curable resins, and have a pencil hardness of about 6H to 8H. Furthermore, the resulting coating film has excellent abrasiveness, and therefore there is no risk of burning during polishing.

Furthermore, examples of the ferromagnetic powder used in the present invention include ferromagnetic iron oxide particles, ferromagnetic chromium dioxide, ferromagnetic alloy powder, and hexagonal ferrite particles.

Here, the above-mentioned ferromagnetic iron oxide particles are those whose X value is in the range of 1.33≦X≦1.50 when expressed by the general formula FeOx, that is, magnetite (γ-Fe2O3
50, magnetite (Fe, 0-x=1.33), and solid solutions thereof (FeOx1.33 <x<1.50
).

Cobalt may be added to these ferromagnetic iron oxides for the purpose of increasing coercive force. There are two types of cobalt-containing magnetic iron oxide: doped type and coated type. Co-doped iron oxide magnetic particles are reduced powder produced by hydrothermally treating ferric hydroxide containing cobalt hydroxide.・Manufactured by oxidation method or method of adsorbing Co compound on the surface of acicular goethite or maghemite and heat-treating it at relatively high temperature. Co-coated iron oxide magnetic particles are manufactured by acicular magnetic particles in an alkaline aqueous solution. It is obtained by mixing iron oxide and cobalt salt and heating to adsorb the cobalt compound, followed by washing with water, drying, taking out and heat-treating in a non-reducing atmosphere. Co
Adhesive iron oxide magnetic particles have superior transfer characteristics and demagnetization characteristics when formed into a tape, compared to CO-doped acid iron oxide magnetic particles.

Examples of the ferromagnetic chromium dioxide include Cry, and Ru and Sn for the purpose of improving coercive force.

A material to which at least one of Te+Sb, )'e, Ti, V, Mn, etc. is added can be used.

Examples of the ferromagnetic alloy powder include Fe, Co, and Ni.

Fe-Co, Fe-Ni or Fe-Co-Ni can be used, and A may be added to these to improve various properties.
j! , Si, Ti, Cr, Mn, Cu.

A material to which a metal component such as Zn is added can be used.

Furthermore, in the magnetic layer, non-magnetic pigments with a Mohs hardness of 6 or higher are added as reinforcing agents, fine inorganic powders such as molybdenum disulfide and tungsten disulfide, silicone oil, fine plastic powders, and unsaturated aliphatic compounds that are liquid at room temperature. Lubricants such as hydrocarbons, fatty acid esters, fluorocarbons, etc., with 12 to 1 carbon atoms
8 fatty acids.

Dispersants such as metal soaps such as alkali metal or alkaline earth metal salts of fatty acids, amides of fatty acids, alkyl phosphates, lecithin, and quaternary ammonium salts of trialkyl polyolefin oxy may be added.

A magnetic coating is prepared by dissolving each of these components in a solvent, and is applied onto a highly rigid heat-resistant substrate (on one or both sides) to form a magnetic coating. method, other coating techniques, etc. may be used.

The magnetic coating film thus applied is then irradiated with an electron beam to be cured. In this case, the electron beam irradiation dose is 1 to
It is preferably within the range of 10 Mrad, usually 2
~? Set to about Mrad. Further, the irradiation energy (acceleration voltage) is preferably 100 keV or more, and since the curing speed is extremely fast, the curing time can be significantly shortened.

Note that a thin layer of a lubricant commonly used in this type of media may be formed as a top coat layer on the surface of the magnetic layer cured in this manner.

[Effect]

By using a highly rigid heat-resistant resin substrate for the substrate, the weight of the magnetic disk can be significantly reduced. Further, there is no possibility that the resin substrate contains a magnetic material such as iron, and the signal-to-noise ratio is improved.

On the other hand, by using electron beam curable resin as the binder for the magnetic layer, there is no risk of deformation of the substrate due to heat.
A magnetic layer with excellent coating properties is formed.

[Example] ゛Hereinafter, Example 1 will explain a specific example of the present invention.
゜Co coated-Fe20. ...20 weight parts bisphenol A type epoxy acrylate (molecular weight 2000
)...80 parts by weight Trimethylolpropane triacrylate...20 parts by weight Cr, O,...20 parts by weight Cyclohexanone...240 parts by weight Diethylene glycol monoethyl ether...60 parts by weight or more A magnetic paint having the composition shown is prepared and applied to a polyetherimide substrate (manufactured by GE).

After uniformly coating it on a substrate (trade name: Ultem Substrate) by a spin code method, it was cured by irradiation with an electron beam of 5 Mrad, and a magnetic disk was produced according to a conventional method.

Example 2 A magnetic disk was prepared in the same manner as in Example 1 except that a polycarbonate substrate was used as the substrate.

Comparative Example 1゜Co adhesion r-F+, ○,...200 parts by weight Epoxy resin...80 parts by weight Phenol resin...20 parts by weight Cr, O,...
・20 parts by weight Cyclohexanone 240 parts by weight Diethylene glycol monoethyl ether 60 parts by weight or more A magnetic paint having the composition shown above was prepared, and this was applied to a polyetherimide substrate (manufactured by GE).

After uniformly coating it on a substrate (trade name: Ultem substrate) by a spin code method, it was cured at 150° C. for 6 hours, and a magnetic disk was prepared according to a conventional method.

The resulting magnetic disks often suffer from head crashes or track misalignment due to thermal deformation.
Yield was very poor.

Comparative Example 2゜The same magnetic paint as in Comparative Example 1 was applied to the β substrate, and 200
C. for 2 hours, and a magnetic disk was prepared according to a conventional method.

The surface roughness and CN ratio of the magnetic disks produced according to each of the above-mentioned Examples and Comparative Examples.

Linear recording density and C3S (contact start/stop) characteristics were examined according to conventional methods. The results are shown in the table below.

(Left space below) From this table, it can be seen that in each of the examples to which the present invention is applied, the signal-to-noise ratio is improved and noise is reduced. It can also be seen that the C3S properties were improved and the durability was significantly improved.

Furthermore, it can be seen that in the magnetic disks of each example, the thickness of the magnetic layer can be made thinner, and the recording density can also be improved.

〔Effect of the invention〕

As is clear from the above description, in the magnetic disk of the present invention, since a highly rigid heat-resistant resin substrate is used for the substrate, the weight of the substrate can be reduced, and the power consumption of the disk drive device can be reduced. This makes it possible to downsize the system.

In addition, by using this highly rigid heat-resistant resin substrate, it is possible to prevent the mixing of magnetic components in the substrate, improving the signal-to-noise ratio, making it possible to make the magnetic layer even thinner, and recording density This results in an improvement in

Furthermore, in the magnetic disk of the present invention, since electron beam curable resin is used as the binder for the magnetic layer, there is no effect on the shape of the disk during curing, and the yield is significantly improved. .

Further, by using this electron beam curable resin, the physical properties of the coating film of the magnetic layer can be improved, and the durability of the magnetic disk can be improved.

Claims (1)

[Scope of Claims] A magnetic coating film comprising a magnetic powder and an electron beam curable resin is formed on a highly rigid heat-resistant resin substrate, and the magnetic coating film is cured by irradiation with an electron beam. disk.