JPH0253846B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a magnetic recording medium, and an object thereof is to provide a magnetic recording medium that improves the lubricity and wear resistance of a magnetic layer and has excellent running stability and durability. In general, magnetic recording media such as magnetic tapes are made by coating a magnetic paint consisting of magnetic powder, a binder, an organic solvent, and other necessary components on a substrate such as a polyester film.
Since the magnetic layer travels while contacting guide members, it is required to have a low coefficient of friction and excellent running stability.Also, since the magnetic layer comes into violent sliding contact with the magnetic head etc. during recording and playback, there is little wear on the magnetic layer, making it durable. Requires excellent sexual performance. Therefore, as a measure to improve the lubricity and wear resistance of the magnetic layer, lubricants such as silicone oil have traditionally been incorporated into the magnetic layer. It has been proposed that an organosilicone compound modified with a fatty acid represented by the following formula is mixed into a magnetic layer. (However, in the formula, R ₁ and R ₂ are saturated or unsaturated hydrocarbon groups having 7 to 21 carbon atoms, and n is an integer of 0 to 50.) (However, in the formula, R ₁ , R ₂ and R ₃ are saturated or unsaturated hydrocarbon groups having 7 to 21 carbon atoms, m is an integer of 1 to 100, n is an integer of 0 to 250, and m+n≦300 ,
m≧n/5. ) However, although silicone oil has excellent lubricity, it has poor compatibility with the binder, which makes the magnetic layer inhomogeneous, causing pinholes, and tends to leak excessively onto the surface of the magnetic layer. The fatty acid-modified organosilicone compounds represented by ) and () have fatty acid residues that have excellent affinity with binders at both ends or both ends and in the main chain, improving compatibility with binders and providing lubrication. Although the effect is exhibited and the lubricity and wear resistance of the magnetic layer are improved, it is still not fully satisfactory. In view of these circumstances, the inventors conducted various studies and found that the general formula (However, in the formula, R ₁ and R ₂ are -CH ₃ or -
R ₃ OPO(OM) ₂ , R ₃ is a hydrocarbon group having 1 to 26 carbon atoms, M is -H or a monovalent metal element or -
Represents NH ₄ , where n ₁ and n ₂ are 0≦n ₁ <1000, 1≦
It is an integer of n ₂ ≦500, n ₄ +n ₂ ≦1000. ) When the modified organic silicone compound shown in ) is contained in the magnetic layer, the compatibility with the binder becomes moderately good, and the lubrication of the magnetic layer is achieved without excessive exudation or formation of pinholes on the surface of the magnetic layer. The present inventors have discovered that the properties and abrasion resistance can be sufficiently improved, leading to the present invention. The modified organosilicone compound used in this invention has -
R ₃ OPO (OM) ₂ (R ₃ is a hydrocarbon group, M is -H or a monovalent metal element or -NH ₄ ), which has a highly polar modified group with excellent affinity with binders. Therefore, it is well compatible with the binder, and accordingly, it oozes out to the surface of the magnetic layer appropriately, and does not excessively ooze out to the surface of the magnetic layer or cause pinholes. In addition, these highly polar modified groups have good lubricity, and together with the main chain consisting of an organic silicone compound with excellent lubricity, these modified groups also exhibit an excellent lubricating effect. Lubricity and wear resistance are further improved. This effect is particularly significant when these modified groups are present not only in the main chain but also at both ends of the main chain. Therefore, according to the present invention, the lubricant is not excessively exuded onto the surface of the magnetic layer. The lubricity and abrasion resistance of the magnetic layer are sufficiently improved without causing any scratches or pinholes, and a magnetic recording medium with excellent running stability and durability can be obtained. In the organosilicone compound of the present invention represented by the above general formula, R ₃ of the modifying group represented by —R ₃ OPO(OM) ₂ is

【formula】

An aromatic compound such as [Formula] or a saturated or unsaturated hydrocarbon group represented by the general formula CnH ₂ n or CnH _2o-2 , preferably having a carbon number of 1 to 26, and having a carbon number of 1 If it is less than 26, the improvement in wear resistance will not be sufficient, and if it exceeds 26, the lubricity may deteriorate even more. In addition, since the polarity of the modified group greatly affects the lubricating effect, M of the modified group must be a strongly polar one such as -H, a monovalent metal element such as -Na, -K, or _-NH4 . is preferred. Specific examples of such modifying groups include -C ₂ H ₄ OPO
(OH) ₂ , ―C ₂ H ₄ OPO (ONa) ₂ , ―C ₂ H ₄ OPO
(OK) ₂ , -C ₂ H ₄ OPO (ONH ₄ ) ₂ , -C ₅ H ₁₀ OPO
(OH) ₂ , ―C ₁₀ H ₂₀ OPO (OH) ₂ , ―C ₂₆ H ₅₂ OPO
Examples include (CH) ₂ , —C ₂ H ₂ OPO(OH) ₂ , and the like. R ₁ and R ₂ are a methyl group or the same modified group as above, and when R ₁ and R ₂ are the same modified groups as above, the compatibility with the binder becomes even better and moderate, and the magnetic The lubricity and wear resistance of the layer is also further improved. Note that R ₁ and R ₂
may be the same or different. Further, the degree of polymerization, that is, n ₁ and n ₂ in the above general formula is preferably an integer of 0≦n ₁ <1000, 1≦n ₂ ≦500, n ₁ +n ₂ ≦1000, and n ₁ and n ₂ are If it is too large, it becomes difficult to dissolve in organic solvents, making it difficult to form into a paint, and the lubricity and abrasion resistance cannot be sufficiently improved. Such modified organic silicone compounds of the present invention may be used alone or in a mixture of two or more, and may be present in the magnetic layer in an amount of 0.1% by weight or more based on the magnetic powder. The effect is exhibited when it is included, and the effect becomes more pronounced as the content increases. However, the content is higher than that of magnetic powder.
If it exceeds 10% by weight, it may leak excessively onto the surface of the magnetic layer, contaminating the magnetic head, and reducing the output. Therefore, it should be included in the magnetic layer in a range of 0.1 to 10% by weight based on the magnetic powder. is preferable. In order to incorporate the modified organic silicone compound of this invention into a magnetic layer, it is mixed and dispersed with magnetic powder, a binder, an organic solvent, etc. to prepare a magnetic paint, and this magnetic paint is coated on a substrate such as a polyester film. Alternatively, the modified organosilicone compound of the present invention may be dissolved in a suitable solvent, and the solution obtained by dissolution may be coated or sprayed on a previously formed magnetic layer. Alternatively, the magnetic layer may be immersed in the solution. The magnetic powder used here is, for example, γ-
Fe ₂ O ₃ powder, Fe ₃ O ₄ powder, Co-containing γ-Fe ₂ O ₃ powder,
Co-containing _Fe3O4 powder, _{CrO2 powder} other Fe powder, Co
Various conventionally known magnetic powders such as powder, Fe--Ni powder, etc. are widely included. Also, as a binder,
Vinyl chloride-vinyl acetate copolymers, vinylidene chloride resins, acrylonitrile-butadiene copolymers, vinyl butyral resins, polyurethane resins, cellulose resins, isocyanate compounds, etc., which are commonly used as binders for magnetic powders. Any of these may be used, and among them, vinyl chloride-vinyl acetate copolymers, cellulose resins, polyurethane resins, and the like are preferably used. The organic solvent is not particularly limited, and includes solvents suitable for dissolving the modified organic silicone compound and binder of the present invention, such as ketone solvents such as acetone, methyl isobutyl ketone, methyl ethyl ketone, and cyclohexanone, ethyl acetate, and acetic acid. Ester solvents such as butyl, aromatic hydrocarbon solvents such as benzene, toluene, and xylene, alcohol solvents such as isopropyl alcohol, acid amide solvents such as dimethylformamide, and ether solvents such as tetrahydrofuran and dioxane are used alone. Alternatively, two or more types may be used in combination. Incidentally, various additives commonly used in magnetic paints, such as dispersants, abrasives, antistatic agents, etc., may be optionally added. Next, embodiments of the invention will be described. Example 1 Structural formula Co-containing γ-Fe ₂ O ₃ magnetic powder 80 parts by weight VAGH (manufactured by UCC, USA, vinyl chloride-vinyl acetate-vinyl alcohol copolymer) 10 parts by weight Pandex T -5250 (manufactured by Dainippon Ink Co., Ltd., urethane elastomer) 8 Coronate L (manufactured by Nippon Polyurethane Industries, Ltd., trifunctional low molecular weight isocyanate compound)
A magnetic paint was prepared by mixing and dispersing a mixture of the following compositions in a ball mill for 70 hours: 2 cyclohexanone 50 methyl ethyl ketone 50 modified organic silicone compound 1. This magnetic paint was applied to a polyester film with a thickness of 11μ to a dry thickness of 5μ, dried, and surface treated.
I cut it into 3.8mm width pieces and made magnetic tape. Example 2 The composition of the magnetic paint in Example 1 was the same as Example 1 except that the same amount of a modified organic silicone compound represented by the structural formula shown below was used in place of the modified organic silicone compound having the structural formula shown in Example 1. He made magnetic tape in the same way. Comparative Example 1 In the composition of the magnetic paint in Example 1, the same amount of dimethylpolysiloxane type silicone oil represented by the following structural formula was used in place of the modified organic silicone compound having the structural formula shown in Example 1. A magnetic tape was made in the same manner as in Example 1. Comparative Example 2 Example 1 except that in the composition of the magnetic paint in Example 1, the same amount of myristic acid-modified organic silicone compound represented by the following structural formula was used in place of the modified organic silicone compound having the structural formula shown in Example 1. A magnetic tape was made in the same manner as in 1. The magnetic tapes obtained in each Example and each Comparative Example were tested for durability and measured for friction coefficient.
The durability test was performed by running each magnetic tape at a head load of 10 g and a running speed of 4.8 cm/sec under conditions of 35°C and 8% RH, and measuring the number of runs until the output decreased by 3 dB from the initial output. The friction coefficient was measured by running the magnetic tape under the same conditions as in the durability test described above and measuring the friction coefficient with the magnetic head after running 200 times. The table below shows the results.

[Table] As is clear from the above table, the magnetic tapes obtained by the present invention (Examples 1 and 2) have lower coefficients of friction and are more durable than conventional magnetic tapes (Comparative Examples 1 and 2). This shows that the magnetic recording medium obtained by the present invention has excellent running stability and durability.

Claims (1)

[Claims] 1. General formula (However, in the formula, R ₁ and R ₂ are -CH ₃ or -
R ₃ OPO(OM) ₂ , R ₃ is a hydrocarbon group having 1 to 26 carbon atoms, M is -H or a monovalent metal element or -
Represents NH ₄ , where n ₁ and n ₂ are 0≦n ₁ <1000, 1≦
It is an integer of n ₂ ≦500, n ₁ +n ₂ ≦1000. ) A magnetic recording medium having a magnetic layer containing an organic silicone compound represented by: