JPH11144226A - Information recording medium and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve flexibility and surface characteristic and to obtain a high density and high reliability by constituting a nonmagnetic base which supports a magnetic layer of a nonmagnetic metallic sheet having flexibility. SOLUTION: The sheet of a thickness having the prescribed flexibility is formed to a doughnut shape or disk shape by a nonmagnetic metal consisting essentially of aluminum, copper, etc. The thickness is specified to 15 to 100 μm to impart the flexibility and strength to the sheet and to facilitate handling. The magnetic layer consisting of the prescribed material is formed by using a binder, such as polyurethane resin, having a good adhesion property to the base and excellent wear resistance on this metallic sheet, by which the information recording medium is constituted. The metallic sheet surface may be subjected to a chemical treatment or may be provided with an intermediate layer between the magnetic layer and the metallic base in order to improve the adhesiveness of the nonmagnetic base and the magnetic layer. As a result, the disk having a high calendering effect, has excellent flatness and smoothness, maintains penetration and is dealable with a removable system is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a magnetic recording medium, and more particularly to a magnetic recording medium suitable for high-capacity, high-density recording.

[0002]

2. Description of the Related Art A disk-shaped or donut-shaped disk-shaped information recording medium having a magnetic layer containing a magnetic substance and a binder on a non-magnetic support is exemplified by a floppy disk and a hard disk. In the case of a floppy disk, as a non-magnetic support, polyesters such as polyethylene phthalate and polyethylene-2,6-naphthalate having a thickness of about 32 μm to 75 μm, polyolefins such as polypropylene, cellulose derivatives such as cellulose triacetate and cellulose diacetate, and aramid And plastics such as polycarbonate.

The form of the nonmagnetic support is a film. In order to improve the adhesiveness between the nonmagnetic support and the magnetic layer, for example, a corona discharge treatment or a surface treatment with a surface modifier such as an aqueous amine solution, trichloroacetic acid, or phenol may be performed. This is because when switching to a plurality of drives like a removable medium and using the same, the disk is given flexibility so as to give sufficient margin to the penetration so that the medium can be easily interchanged.

On a hard disk, 0.6 mm to 0.
A strong nickel aluminum plate or glass plate of about 8 mm is used. Since this is a fixed disk system, there is no need for compatibility with the media itself, and since the head is a floating type, it is necessary to stably maintain the spacing between the head and the media, so that the rigid support This is because a medium having a surface with good smoothness is required.

In recent years, the capacity of removable disks has been increased, and the technology of hard disks has been applied to flexible media. For example, in a ZIP drive with a storage capacity of 100 MB sold in the United States, the head is In the medium, a part of the head called a pseudo contact is in contact with the medium, and the other part operates in a floating state.

In such a type of drive, it is necessary to enhance the surface properties of the medium more than before in order to maintain the running stability. However, when the non-magnetic support is the above-mentioned plastic, it is a mirror finishing process of the medium surface. Even if the calendering is applied strongly, it is absorbed by the elasticity of the plastic, and the effect on the properties of the media surface is not sufficiently exhibited, and it is difficult to further improve the capacity and the recording density. In addition, the escape due to the elasticity of the support also affects the packing density of the magnetic layer, making it difficult to increase the strength of the magnetic layer and making it difficult to increase the durability. In addition, if a substrate used for a hard disk is used, a penetration margin cannot be sufficiently obtained, so that it is difficult to handle as a removable disk.

[0007]

SUMMARY OF THE INVENTION The present invention provides an information recording medium which retains flexibility enough to maintain penetration, has good surface properties, and can satisfy high density and high reliability. .

[0008]

DISCLOSURE OF THE INVENTION The present invention has been made as a result of intensive studies from such a viewpoint, and has a disk-shaped information comprising a magnetic layer containing a magnetic substance and a binder formed on a non-magnetic support. An object of the present invention is to provide an information recording medium in which the non-magnetic support is made of a flexible non-magnetic metal sheet, and a method of manufacturing the same.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION As a non-magnetic support of the information recording medium of the present invention, a flexible non-magnetic metal is used, and a metal mainly composed of aluminum such as aluminum and duralumin, copper, bronze, brass, A metal containing copper as a main component such as phosphor bronze can be used. When the disk-shaped information recording medium is used as the metal sheet, the metal sheet has a flexible thickness. The degree of flexibility is preferably such that when the central portion of the disc-shaped information recording medium is supported and leveled, the periphery of the information recording medium is slightly lower than the horizontal level due to the deflection of the non-magnetic support. When the information recording medium is in the form of a donut with a large hole at the center, the test can be performed by cutting the information recording medium into a disk shape having no holes and having the same material.

Generally, the thickness of the nonmagnetic support is preferably 15 μm or more and 100 μm or less. When the thickness is 15 μm or less, not only the strength as a disk is insufficient, but also the handling when forming a magnetic layer becomes extremely difficult. Also, 10
If it is 0 μm or more, the flexibility is poor, and it is difficult to obtain a sufficient penetration margin. In general, a long metal sheet is used as the nonmagnetic support, and after forming a magnetic layer on the metal sheet, punching is performed to obtain a disc-shaped information recording medium.

In order to improve the adhesiveness between the non-magnetic support and the magnetic layer, the surface of the metal sheet is chemically treated or an intermediate layer is provided between the magnetic layer and the metal support. Is also good. Hereinafter, a method of forming a magnetic layer on a metal sheet by way of example of the production of a coating type information recording medium is described,
It is not limited to this, as long as it does not exceed the scope of the gist.

The magnetic layer preferably contains a ferromagnetic acicular metal powder or a hexagonal ferromagnetic powder and a binder.
It is preferable that the thickness of the magnetic layer is 0.8 μm or less.
If the magnetic layer is thicker than 0.8 μm, it is not suitable for high-density recording in terms of self-demagnetization loss, overwrite characteristics, resolution characteristics, and the like. The thickness of the magnetic layer is 0.01-0.5 [mu] m, especially 0.1.
05-0.3 μm is preferred.

As the ferromagnetic acicular metal powder, a powder having a specific surface area of at least 40 m ² / g by the BET method is used. Especially 4
It is preferable to use one having a density of 5 m ² / g or more. When the specific surface area is less than 40 m ² / g, it is difficult to increase the filling amount of the magnetic powder in the magnetic layer. The magnetic properties of the ferromagnetic acicular metal powder are as follows: σs is 140 emu / g or more,
The holding force (Hc) is preferably 1500 Oe or more. The shape preferably has an average major axis length (L) of 0.20 μm or less, particularly preferably 0.12 μm or less. It is preferable that the aspect ratio (K) is 10 or less.

Further, as the hexagonal ferromagnetic powder, barium ferrite, strontium ferrite, lead ferrite,
Each substitute of calcium ferrite, cobalt substitute, etc.
Hexagonal cobalt powder can be used. Specific surface area by BET method is 40 to 70 m ² / g, plate diameter (L) is 0.02 μm
Hereinafter, the aspect ratio (K) is preferably 10 or less. The ferromagnetic acicular metal powder or the hexagonal ferromagnetic metal powder is preferably contained in the magnetic layer in an amount of 50 to 90% by weight, particularly 65 to 80% by weight. If the ratio of the magnetic powder is small, it is difficult to increase the recording density. Conversely, if this ratio is too large, the durability of the information recording medium tends to decrease.

As the binder, those having excellent adhesion to the support and abrasion resistance, having a glass transition point of -100 to 150 ° C. and a number average molecular weight of about 1,000 to 150,000 are preferably used. Examples of commonly used resins include, for example, polyurethane resins, polyester resins, cellulose acetate butyrate, cellulose diacetate, cellulose derivatives such as nitrocellulose, vinyl chloride-vinyl acetate copolymers, vinyl chloride-vinylidene chloride copolymers, Examples include vinyl chloride resins such as vinyl chloride-acrylic copolymers, various synthetic rubbers such as styrene-butadiene copolymers, epoxy resins, and phenoxy resins. These may be used alone or as a mixture of two or more. can do. The binder resin is preferably used so that the content in the magnetic layer is 2 to 50% by weight, particularly 5 to 25% by weight.

The binder reacts with a crosslinking agent such as a low molecular weight polyisocyanate compound having a plurality of isocyanate groups, for example, a trimethylol adduct of trizine diisocyanate to form a three-dimensional network structure in the magnetic layer. Is preferred. Thereby, the mechanical strength of the magnetic layer can be improved. Such a low molecular weight polyisocyanate compound is preferably used in a ratio of 10 to 50% by weight based on a resin as a so-called binder.

The magnetic layer may further contain various conventional additives such as dispersants, lubricants, abrasives, and antistatic agents. For example, it is preferable to use a dispersant having a phosphate group such as polyether phosphate, polyoxyethylene alkylphenyl phosphate and the like. Examples of such a dispersant having a phosphate group include phosphatidylcholine (lecithin), RE-610 (manufactured by Toho Chemical), and PW-36 (manufactured by Kusumoto Kasei). Further, in addition to the above-mentioned one containing a phosphate ester group as a dispersant, a fatty acid having 12 to 18 carbon atoms such as capric acid, lauric acid, myristic acid, oleic acid and linoleic acid, an alkali metal or alkali of this fatty acid An earth metal salt, that is, a metal soap may be used in combination. It is preferable that the content of the dispersant is usually in the range of 0.1 to 10% by weight, particularly 1 to 5% by weight in the magnetic layer.

As the lubricant, various lubricants such as aliphatic, fluorine, silicone, and hydrocarbon can be used. As the aliphatic lubricant, for example, fatty acids, fatty acid metal salts, fatty acid esters, fatty acid amides, fatty alcohols and the like are used. As fatty acids, for example, oleic acid, lauric acid, myristic acid, palmitic acid, stearic acid, behenic acid, and the like are used. As the fatty acid metal salt, for example, magnesium salt, aluminum salt, sodium salt, calcium salt and the like of these fatty acids are used.
As the fatty acid ester, for example, butyl ester, octyl ester or glyceride of the above fatty acid is used. As the fatty acid amide, for example, linoleic acid amide, caproic acid amide and the like are used in addition to the above-mentioned fatty acid amide. As the aliphatic alcohol, for example, lauryl alcohol, myristyl alcohol, palmityl alcohol, stearyl alcohol, oleyl alcohol and the like are used. As the fluorine-based lubricant, for example, perfluoroalkyl polyether, perfluoroalkyl carboxylic acid, or the like is used. As the silicone-based lubricant, for example, silicone oil, modified silicone oil and the like are used. In addition, solid lubricants such as molybdenum disulfide and tungsten disulfide, and phosphate esters can also be used. As the hydrocarbon lubricant, for example, paraffin, squalane, or the like is used. The content of the lubricant in the magnetic layer is usually 0.1
Preferably, it is used in an amount of 10 to 10% by weight, particularly 1 to 7% by weight. In the case of a magnetic recording medium having a multilayer structure, the content of the lubricant in each layer may be changed.

Examples of the abrasive include α-alumina,
β-alumina, γ-alumina, α-iron oxide, silicon nitride, boron nitride, titanium oxide, silicon dioxide, tin oxide, zinc oxide, calcium carbonate, calcium sulfate, barium sulfate, molybdenum disulfide, tungsten oxide, silicon carbide, Chromium oxide or the like is used alone or in combination. As a commercially available example, AKP manufactured by Sumitomo Chemical Co., Ltd.
-20, AKP-30, AKP-50, HIT-50,
HIT-100, Toda Kogyo TF-100, TF-12
0, TF-140, Ishihara Sangyo FT-1000, FT
2000, STT-4D, STT-3 manufactured by Titanium Industry Co., Ltd.
0, STT-65C, S-1, G5, manufactured by Nippon Chemical Industry Co., Ltd.
G7 and the like, among which those having relatively high hardness are preferably used. The average particle size of the abrasive is 0.
5 μm or less is preferable. The amount of the abrasive used is preferably in the range of 1 to 10% by weight in the magnetic layer.

As the antistatic agent, carbon black,
Metals and their conductive compounds are used. As carbon black, acetylene black, black for color, furnace black, thermal black and the like can be used. A commercially available example is BLA manufactured by Cabot Corporation
CKPEARLS2000, 1000, 900, 80
0, VULCANXC-72, Raven 8800, 8000, 7000 manufactured by Columbian Carbon Co., Ltd., # 3750B, # 3750, # 3250B, # 32 manufactured by Mitsubishi Chemical Corporation.
50, # 950, # 850B, # 650B, # 45, #
40, # 5, MA-77, MA-7 and the like. These carbon blacks can be used alone or in combination. Further, the surface of the carbon black may be treated with a dispersant or the like, or a part of the surface may be graphitized.

As the metal conductive compound, tin oxide,
Indium tin oxide or the like can be used. The amount of the antistatic agent used is usually in the range of 0 to 10% by weight in the magnetic layer. It should be noted that some additives simultaneously exert several effects. The magnetic recording medium according to the present invention is manufactured by kneading and dispersing each component constituting the magnetic layer together with an appropriate solvent to form a uniform coating, and applying this to a metallic nonmagnetic support.

Examples of the solvent include ketones such as methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone, alcohols such as methanol, ethanol, propanol and isopropyl alcohol, esters such as methyl acetate, ethyl acetate and butyl acetate, diethyl ether and tetrahydrofuran. And the like, aromatic hydrocarbons such as benzene, toluene and xylene, and aliphatic hydrocarbons such as hexane.

The preparation of the magnetic coating material for forming the magnetic layer can be carried out by a conventional method using a conventional kneading and dispersing apparatus. The formation of the magnetic layer can be performed by a conventional method using a conventional coating apparatus such as vapor deposition, sputtering, gravure coating, roll coating, blade coating, and extrusion coating.

The magnetic layer is usually applied with a magnetic field before drying. After drying, the surface is smoothed by calendering. The roll for calendering is usually used in combination of a metal roll and a heat-resistant synthetic resin roll, but it is also possible to use only a metal roll in combination. The processing temperature is preferably 70 to 120 ° C, and the linear pressure is 2
It is preferably from 00 to 500 kg / cm.

The metal sheet on which the magnetic layer has been formed in this manner is temporarily stored as a roll, or is used as it is in a punching process for a disk-shaped information medium. In the punching step, as shown in FIG. 1, a magnetic layer is formed, and the rolled metal sheet 1 is formed by a pair of punching dies 2a, 2a.
The information recording medium 4 is punched into a disk shape by b.

In the present invention, the disc-shaped information recording medium 4
May be in the shape of a disk, or may be in the shape of a donut in which a hole for mounting the disk drive is formed in the center of the disk. In FIG. 1, the punching die 2
rolls 3a, 3b, before being punched by
3b, the metal sheet 1 is subjected to a flattening process for removing bending, warping, curling and the like of the metal sheet 1. In FIG. 1, the flattening process is performed by a pair of rolls 3a and 3b. However, a plurality of rolls can be provided. Preferably, the rolls 3a and 3b are provided and the metal sheet 1 is tensioned. It is preferable to pinch.

As shown in FIG. 2, the flattening process may be performed by punching the disc-shaped information recording medium 4 using the rolls 3a and 3b. In FIG. 2, 5a and 5b are take-up rolls. As the rolls 3a and 3b, a roll formed of a combination of a metal roll and a heat-resistant synthetic resin roll, or a flat molding machine made of a combination of a metal roll alone can also be used. The treatment temperature is preferably from 70 to 120 ° C, and the linear pressure in the case of pressing with a roll is from 200 to 5
00 kg / cm is preferred. In addition, the above-mentioned rolls 3a,
In place of 3b, flattening can be performed using a press having a flat platen.

[0028]

According to the present invention, since a flexible metal sheet is used as a non-magnetic support, an information recording medium having a high calendering effect and excellent in flatness and smoothness can be obtained, and the penetration can be maintained. Thus, an information recording medium compatible with a removable system can be obtained.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing an example of a method for manufacturing an information recording medium of the present invention.

FIG. 2 is an explanatory view showing another example of the method for manufacturing the information recording medium of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Metal sheet with a magnetic layer 2 Punching die 3a, 3b roll 4 Information recording medium

Claims (8)

[Claims] 1. A disk-shaped information recording medium comprising a magnetic layer containing a magnetic substance and a binder formed on a non-magnetic support, wherein the non-magnetic support comprises a flexible non-magnetic metal sheet. An information recording medium characterized by being recorded. 2. The information recording medium according to claim 1, wherein the non-magnetic support is a metal sheet containing aluminum as a main component. 3. The information recording medium according to claim 1, wherein the nonmagnetic support is a metal sheet containing aluminum as a main component and having a thickness of 15 to 100 μm. 4. A method for producing an information recording medium by forming a magnetic layer containing a magnetic substance and a binder on a nonmagnetic support, wherein a nonmagnetic metal sheet having flexibility is used as the nonmagnetic support. And a step of flattening by pressing at a stage before or after the step of punching a metal sheet into a disk. 5. The method for manufacturing an information recording medium according to claim 4, wherein the clamping pressure is performed by a press having a flat surface. 6. The method for manufacturing an information recording medium according to claim 4, wherein the clamping is performed by a roll. 7. The method for manufacturing an information recording medium according to claim 4, wherein the nonmagnetic support is a metal sheet containing aluminum as a main component. 8. The method for producing an information recording medium according to claim 4, wherein the nonmagnetic support is a metal sheet containing aluminum as a main component and having a thickness of 15 to 100 μm.