JPS6338770B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a magnetic disk cartridge in which a magnetic disk is rotatably housed in a jacket, and an object of the present invention is to improve the abrasion resistance of the magnetic layer and provide a magnetic disk cartridge with excellent durability. In general, magnetic disk cartridges perform recording and reproduction by rotating the magnetic head at high speed while slidingly contacting the magnetic disk in the jacket.
When the magnetic disk rotates, it also comes into sliding contact at high speed with a liner made of nonwoven fabric attached to the inner surface of the jacket so that the disk surface is constantly cleaned, so wear due to this liner is likely to occur, especially in recording and reproducing devices. In order to stably fix a loaded jacket, the liner and disk make strong sliding contact at the part where the support members press from both sides of the jacket, so that an annular wear band that can be seen with the naked eye may occur in this clamping part. As described above, magnetic disk cartridges require higher wear resistance of the magnetic layer than other media such as magnetic tape, and to date, methods have generally been proposed to improve this wear resistance. . For example, by mixing non-magnetic powder with a Mohs hardness of 6 or more into the magnetic layer, or by mixing a lubricant such as liquid paraffin, higher fatty acid, higher alcohol, silicone oil, etc. into the magnetic layer, the above-mentioned methods can be used. Unable to fully satisfy requirements. According to the method of mixing non-magnetic powder with a Mohs hardness of 6 or more, the coating film becomes hard and the abrasion strength of the coating film itself increases, but on the other hand, there is a problem that the liner is abraded by this hard magnetic layer. However, this worn liner increases the sliding resistance with the magnetic layer and tends to induce abrasion of the magnetic layer, and the hard magnetic coating has the disadvantage of abrading the magnetic head. Furthermore, the method of mixing a lubricant such as liquid paraffin into the magnetic layer has the disadvantage that the lubricant tends to bleed out over time and transfer to the liner, making it difficult to maintain the lubricating function over a long period of time. There is. In view of the above circumstances, the inventors conducted various studies and found that when a non-magnetic powder with a Mohs hardness of 6 or more is used in combination with higher fatty acids and higher fatty acid esters that are solid at room temperature, the wear resistance of the magnetic layer itself is greatly improved. At the same time, abrasion of the liner (and magnetic head) is also suppressed, and as a result, there is no occurrence of an annular wear zone in the magnetic layer at the localized jacket clamping area, which was a problem in the past, resulting in extremely high durability. It has been discovered that a magnetic disk cartridge can be obtained. Specific examples of non-magnetic powders with a Mohs hardness of 6 or more used in this invention include α-iron oxide powder (Mohs hardness 6), aluminum oxide powder (Mohs hardness 9), silicon carbide powder (Mohs hardness 9), At least one selected from silicon oxide powder (Mohs hardness 7), garnet powder (Mohs hardness 7), and chromium oxide powder (Mohs hardness 9) is used. Note that even if a soft non-magnetic powder with a Mohs hardness of less than 6, such as calcium carbonate (Mohs hardness 4), is added to the magnetic layer, it will not work to harden the magnetic layer and increase its layer strength. Even if it is used in combination with the specific lubricant of the present invention, it is not possible to form a magnetic layer with highly improved wear resistance as the object of the present invention. The average particle diameter of such non-magnetic powder having a Mohs hardness of 6 or more is preferably 2 μm or less. The reason for this is that since the thickness of the magnetic layer is generally about 2.5 to 10 microns, if the average particle diameter exceeds 2 microns, the surface smoothness of the magnetic layer will be impaired. Within this range, as the particle size increases, better results are obtained in improving the wear resistance of the magnetic layer, and as the particle size becomes smaller, especially when it becomes smaller than the particle size of the magnetic powder, the wear resistance is improved. Therefore, it is particularly preferable to use particles with an average particle diameter of 0.5 to 2μ. Particularly suitable are α-iron oxide powder, aluminum oxide powder, and silicon carbide powder. Additionally, if too much of this non-magnetic powder is added, it tends to reduce the output and cause wear of the magnetic head or liner.
It is preferably within the range of 0.5 to 5 parts by weight per 100 parts by weight. In this invention, the higher fatty acid ester used in combination with the non-magnetic powder having a Mohs hardness of 6 or more is generally liquid at room temperature, but most of them have a relatively high freezing point.
Because it has a high viscosity, its leaching and migration to the surface of the magnetic coating film is smaller than that of other lubricants such as liquid paraffin, so it has excellent lubrication ability even when used alone. Addition of solid higher fatty acids further increases this effect. That is, in general, when the solvent is removed from a mixture of the two in an appropriate solvent such as cyclohexanone, a viscous crystalline structure in which the higher fatty acid ester is impregnated and retained in the higher fatty acid is formed. Even when both of the above substances are contained in the magnetic layer, those with the above crystalline structure are formed in the voids of the magnetic layer, and higher fatty acids with relatively good affinity with the magnetic layer are converted into higher fatty acid esters. A necessary and sufficient amount of is supplied to the surface of the magnetic layer. The ability to retain higher fatty acid esters with such a crystalline structure increases as the amount of higher fatty acids added increases, but if this retention ability becomes too large, the required amount of higher fatty acid esters will be retained in the magnetic layer. They tend to be difficult to leach out to the surface, and taking this into account, the blending ratio of higher fatty acid ester and higher fatty acid is preferably in the range of 70:30 to 99.5:0.5 by weight. The higher fatty acids used in this invention are solid at room temperature, and specifically myristic acid, palmitic acid, stearic acid, etc. having a melting point of 45° C. or higher are preferably used. Further, the higher fatty acid ester to be used in combination with this higher fatty acid may be any fatty acid ester of a higher fatty acid having 15 or more carbon atoms, and specific examples include stethulinate/n-butyl, propyl palmitate,
Examples include amyl palmitate and propyl oleate. In order to contain a nonmagnetic powder with a Mohs hardness of 6 or more, a higher fatty acid ester, and a higher fatty acid in the magnetic layer, the nonmagnetic powder is kneaded with the magnetic powder and a binder to form a magnetic layer, and the higher fatty acid is added to the magnetic layer. By coating or spraying the ester and higher fatty acid with or without diluting with a suitable solvent such as n-hexane, or by immersing the magnetic layer containing the non-magnetic powder in this lubricant solution. Although it can be done as appropriate, it may also be incorporated by kneading a nonmagnetic powder, a higher fatty acid ester, and a higher fatty acid together with a magnetic powder and a binder to form a magnetic layer. As for the content, the total amount of higher fatty acids and higher fatty acid esters is usually 0.1 parts by weight per 100 parts by weight of magnetic powder.
The amount is preferably 0.3 to 12 parts by weight. If the amount is too large, the surface condition of the magnetic layer tends to deteriorate and dropouts and noise tend to increase slightly, which is not preferable. Next, examples of this invention will be described. Example 1 γ-Fe ₂ O ₃ magnetic powder 68 parts by weight VAGH (hydroxyl group-containing vinyl chloride manufactured by UCC, USA)
(vinyl acetate copolymer) 26 N1432J (acrylonitrile-butadiene copolymer manufactured by Nippon Zeon) 5 Coronate L (polyisocyanate manufactured by Nippon Polyurethane) 2 α-iron oxide powder (cubic, average particle size 1μ)
1.5 〃 Methyl isobutyl ketone 75 〃 Toluene 75 〃 Carbon black 7 〃 A magnetic paint consisting of this composition was prepared, and this was coated on a polyester base film and dried to form a magnetic layer, and the following ratio was added to this as a lubricant. A solution of n-butyl stearate and stearic acid dissolved in 1,200 parts by weight of toluene was applied, about 6 parts by weight of lubricant was applied to 100 parts by weight of the magnetic powder, and after drying, it was punched out into a disk shape. to make a magnetic disk.

[Table] Example 2 Instead of using α-iron oxide powder as the non-magnetic powder in Example 1, aluminum oxide powder (average particle size 0.5μ) and silicon carbide powder (average particle size 0.7μ) were used as shown in the table below. Samples Nos. 2-1 to 3 were prepared in the same manner using stearic acid and n-butyl stearate in combination.
-4 magnetic disk cartridge was obtained.

[Table] Comparative Examples 1 to 2 The same procedure was carried out except that 100 parts by weight of n-butyl stearate (Comparative Example 1) and 20 parts by weight of stearic acid (Comparative Example 2) were used as lubricants and dissolved in 1200 parts by weight of toluene. Magnetic disks having the compositions shown below are prepared in the same manner as in Examples 1 and 2.

【table】

[Table] Comparative Example 3 The following sample magnetic disk was prepared in exactly the same manner as in Examples 1 and 2, except that no lubricant solution was applied to the surface of the magnetic layer. Sample No. Non-magnetic powder Comparison 3-1 α-iron oxide powder 3-2 Aluminum oxide powder 3-3 Silicon carbide powder 3-4 Calcium carbonate powder comparative example 4 No α-iron oxide powder added to magnetic paint, A magnetic disk was prepared in the same manner as in Example 1, except that 100 parts by weight of n-butyl stearate dissolved in 1200 parts by weight of toluene was used as the lubricant solution. Comparative Example 5 In Sample No. 4 of Example 1, α-
A magnetic disk was produced in the same manner as in Example 1 without adding iron oxide powder. Comparative Example 6 The same amount of calcium carbonate powder (Mohs hardness 4) was used in place of the α-iron oxide powder in Example 1, and magnetic disks of the following sample No. were prepared in the same manner.

[Table] The magnetic disk bodies obtained in the Examples and Comparative Examples were inserted into the jackets shown in Figs. The time until the cumulative number of dropouts reached 500 was measured while sliding the pads in sliding contact at a speed of about 1 m/sec with a pad pressure of 40 g/cm ² ). In the figure, 2 is a drive shaft insertion hole of the magnetic disk body 1, 3 is a jacket made of vinyl chloride resin, 4 is a drive shaft insertion window of the jacket 3, 5 is a magnetic head insertion window, and 6 is a polypropylene fiber, rayon fiber, etc. This is a liner made of the nonwoven fabric used. In addition, the magnetic disk cartridge was loaded into a playback device, and after being driven for 4 hours in the same atmosphere as above with local clamping pressure (pressing force 125 g/cm ² ) from both sides of the cartridge, the magnetic disk cartridge was was removed from the jacket and visually observed for the presence or absence of an annular wear zone. The table below shows the results.

【table】

[Table] As is clear from the above table, compared to each comparative example, this product, which uses a combination of non-magnetic powder selected from α-iron oxide powder, aluminum oxide powder, and silicon carbide powder, n-butyl stearate, and stearic acid, It is clear that the magnetic disk cartridge according to the invention has a long running time and excellent wear resistance, and particularly has excellent durability without causing an annular wear band even when subjected to local clamping pressure. be.

[Brief explanation of the drawing]

FIG. 1 is a partially cutaway plan view of a magnetic disk cartridge according to the present invention, and FIG.
It is a sectional view taken along the line -' in the figure.

Claims (1)

[Scope of Claims] 1. Non-containing powder with an average particle size of 2μ or less, consisting of at least one selected from α-iron oxide powder, aluminum oxide powder, silicon carbide powder, silicon oxide powder, garnet powder, and chromium oxide powder. 0.5 to 5 parts by weight of magnetic powder to 100 parts by weight of magnetic powder, higher fatty acids that are solid at room temperature, and fatty acid esters of higher fatty acids with carbon number of 15 or more in a weight ratio of 30:70 to 0.5:99.5.
A magnetic disk cartridge having a magnetic layer containing 0.1 to 15 parts by weight of a compound in the range of 0.1 to 15 parts by weight per 100 parts by weight of magnetic powder. 2. The magnetic disk cartridge according to claim 1, wherein the magnetic layer contains a higher fatty acid consisting of at least one kind selected from myristic acid, palmitic acid, and stearic acid. 3. The magnetic disk cartridge according to claims 1 and 2, wherein the magnetic layer contains a fatty acid ester of a higher fatty acid consisting of at least one selected from palmitic acid, stearic acid, and oleic acid.