JPH058491B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a magnetic recording medium having a magnetic layer on a non-magnetic support, such as a magnetic tape or a magnetic disk. Magnetic tapes are particularly required to have various characteristics such as a low coefficient of friction, smooth and stable running properties, a small amount of powder falling off, and good sprite properties. That is, the magnetic tape
When used in magnetic recording and reproducing devices such as VTRs,
Since the tape runs at high speed while physically contacting tape guides, magnetic heads, etc., it is important that it has excellent wear resistance and can run stably for a long time. For example, if the coefficient of friction on the tape surface changes during recording or playback, the tape will vibrate at the guide or magnetic head. As a result, the frequency of the signals recorded and played back on the tape (for example, timbre signals) changes, resulting in a sound different from the original frequency, or the vibration sound of the tape (so-called Q sound) can be directly heard. be. In order to prevent this, various attempts have been made to impart lubricity to the tape. For example, a solid lubricant such as molybdenum disulfide, graphite, or wax is added to a magnetic paint containing magnetic powder and a binder. However, this solid lubricant is not desirable because it is not very effective in terms of durability, and if added in a large amount, it deteriorates the magnetic properties. On the other hand, higher fatty acids, higher fatty acid esters, paraffinic hydrocarbons, silicone oils (e.g. dimethyl silicone oil, diphenyl silicone oil), etc. are sometimes used as lubricants, but these also provide sufficient durability and lubricity. This is particularly inadequate for VTR cassettes.
Moreover, blooming, in which the lubricant oozes out onto the surface of the magnetic layer, is likely to occur, causing tape adhesion phenomena, stick slips, and the like. The present invention has been made to correct the above-mentioned defects, and an object of the present invention is to improve the running properties of a magnetic recording medium by using a new lubricant as the above-mentioned lubricant. That is, the present invention relates to a magnetic recording medium having a magnetic layer on a non-magnetic support, characterized in that the magnetic recording medium contains a phosphite represented by the following chemical formula. be.

[Formula] or

[Formula] (However, R ₁ , R ₂ and R ₃ represent an alkyl group having 8 to 18 carbon atoms.) In the triester or diester of phosphorous acid represented by the above chemical formula, R ₁ , R ₂ , R ₃ represents an alkyl group each having 8 to 18 carbon atoms, and R ₁ , R ₂ and R ₃ may be the same or different. Furthermore, R ₁ , R ₂ , and R ₃ may be a linear alkyl group or a branched alkyl group having a side chain, but the number of carbon atoms in the alkyl group is 8 to 18. is preferred. If the number of carbon atoms is less than 8, the lubricating property will be poor, while if the number of carbon atoms is more than 18, it will be difficult to obtain. When included in the magnetic layer, the amount of the lubricant used in the present invention is preferably 0.2 to 4 parts by weight (PHP) per 100 parts by weight of the magnetic powder in the magnetic layer. In addition, if it is included in the back coat layer (described later) on the back of the base, 100% of the binder in the back coat layer is added.
Preferably, the amount is 0.2 to 20 parts by weight (PHR). Furthermore, when forming a top coat layer or a coating layer (both described below) made of the above-mentioned lubricant, the amount of the lubricant applied is 1 to 1.
Desirably it is 1000 mg/m ² . Furthermore, it is also possible to use the lubricant according to the invention in combination with the other conventional lubricants mentioned above. A magnetic recording medium, such as a magnetic tape, according to the present invention is illustrated in FIGS. 1 to 5. FIG. 1 shows a non-magnetic base 1 on which a magnetic layer 2 containing the lubricant of the present invention is formed. In the following figures as well, the layer containing the lubricant according to the invention is shown in dotted cross-sections. Figure 2 shows
This figure shows a state in which a top coat layer 3 made of a lubricant according to the present invention is formed on the surface of a magnetic layer 2. FIG. 3 shows a state in which a coating layer 4 made of a lubricant according to the present invention is formed on the back surface of the nonmagnetic base 1.
FIG. 4 shows a state in which the lubricant according to the present invention is contained in the back coat layer 5 formed on the back surface of the non-magnetic base 1, and further, FIG. A state in which layer 6 is formed is shown. The back coat layer 5 is provided for various purposes, including stabilizing runnability by appropriately controlling the surface roughness of the back surface, and preventing static electricity. For this purpose, the back coat layer may be coated with a binder mixed with carbon black, or may further contain a nonmagnetic pigment such as α-Fe ₂ O ₃ , alumina, talc, etc. The magnetic recording medium of the present invention can be applied not only to such magnetic tapes but also to magnetic disks having magnetic layers on the front or back surfaces. Furthermore, the lubricant according to the present invention is held at a position in the magnetic layer 2 or on the surface of the magnetic layer 2 and/or
Or on the back side. Magnetic powders that can be used in the magnetic layer of the present invention include:
γ-Fe ₂ O ₃ , Fe ₃ O ₄ , mixed crystal of γ-Fe ₂ O ₃ and Fe ₃ O ₄ , γ-Fe ₂ doped or coated with cobalt
O ₃ or Fe ₃ O ₄ , CrO ₂ , barium ferrite,
Various alloy powder magnetic materials (e.g. Fe-Co, Co-
Ni, Fe-Co-Ni, Fe-Co-B, Fe-Co-Cr-
B, Mn-Bi, Mn-Al, Fe-Co-V, etc.), iron nitride, etc., and two or more of these may be used in combination. Binders that can be used in the magnetic layer include vinyl chloride-vinylacetate copolymer, vinyl chloride-vinyl acetate-vinyl alcohol copolymer, vinyl chloride-vinyl acetate-maleic acid copolymer, and vinyl chloride-vinylidene chloride. copolymer, vinyl chloride-acrylonitrile copolymer, acrylic ester-acrylonitrile copolymer,
Acrylic acid ester-vinylidene chloride copolymer,
Methacrylic acid ester-vinylidene chloride copolymer, methacrylic acid ester-styrene copolymer,
Thermoplastic polyurethane resin, phenoxy resin, polyvinyl fluoride, vinylidene chloride-acrylonitrile copolymer, butadiene-acrylonitrile copolymer, acrylonitrile-butadiene-methacrylic acid copolymer, acrylonitrile-butadiene-
Acrylic acid copolymer, polyvinyl butyral, polyvinyl acetal, cellulose derivative, styrene-butadiene copolymer, polyester resin, phenol resin, epoxy resin, thermosetting polyurethane resin, urea resin, melamine resin, alkyd resin, urea formaldehyde resin, etc. can be mentioned. When preparing magnetic paint, as an organic solvent,
Ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexane; alcohols such as methanol, ethanol, propanol, butanol; esters such as ethyl acetate, butyl acetate, ethyl lactate, glycol acetate, monoethyl ether; ethylene glycol dimethyl ether, ethylene glycol monoethyl ether,
Glycol ethers such as dioxane; aromatic hydrocarbons such as benzene, toluene and xylene; aliphatic hydrocarbons such as hexane and heptane; nitropropane and the like can be used alone or as a mixture. The magnetic base on which the magnetic paint prepared with this organic solvent is applied includes polyesters such as polyethylene terephthalate, polyolefins such as polypropylene, cellulose derivatives such as cellulose triacetate and cellulose diacetate, polycarbonate, polyvinyl chloride,
Examples include polyamide, polyimide, aluminum, metal materials such as copper, and paper. Further, as a solvent for coating the top coat layer and coating layer comprising a lubricant, a low boiling point solvent such as freon, hexane, ethanol, etc. can be used. Further, magnetic recording media to which the compound of the present invention is applied as a lubricant are not limited to so-called coated magnetic recording media in which a magnetic layer is formed by coating together with magnetic powder and a binder as described above, but also metal ferromagnetic thin film type magnetic recording media. It also applies to magnetic recording media. This metal ferromagnetic thin film magnetic recording medium has a magnetic metal such as Co, Fe, Ni, or an alloy thereof plated on a non-magnetic support.
It is formed by vapor deposition, ion plating, sputtering, or the like. This metal ferromagnetic thin film magnetic recording medium has a high magnetic flux density because it does not require the use of a binder, and is useful for short wavelength, high density recording because it is formed into a very thin layer. The present invention will be explained below with reference to Examples. Example 1 Part by weight Co-adhered γ-Fe ₂ O ₃ 100 Vinyl chloride-vinyl acetate copolymer 15.5 (VAGH manufactured by UCC) Polyurethane resin 6.5 (N-5033 manufactured by Nippon Polyurethane) Carbon (antistatic agent) 5 Lecithin (Dispersant) 1 Methyl ethyl ketone 150 Methyl isobutyl ketone 150 The above composition was used as a basic composition, 2 parts by weight of trilauryl phosphite was added to the basic composition, mixed in a Pall mill for 24 hours, and then taken out through a filter. Furthermore, 4 parts by weight of a curing agent was added before coating, and the mixture was stirred for 30 minutes. The thus obtained magnetic paint was applied onto a polyethylene terephthalate base having a thickness of 12 μm so that the thickness after drying would be 5 μm, and after magnetic field orientation, it was dried and wound up.
This was calendered and cut into 1/2 inch width to create a sample tape. Example 2 A sample tape was prepared in the same manner as in Example 1 using a magnetic paint to which 2 parts by weight of dilauryl phosphite of the basic composition of Example 1 was added. Example 3 A sample tape was prepared in the same manner as in Example 1 using the basic composition of Example 1 as a magnetic paint. A 1.0wt% n-hexane solution of phosphite trilauryl ester was added to the magnetic layer of the sample tape.
The application amount of phosphite trilauryl ester is 160
A sample tape was prepared by coating (top coat) so that the concentration was mg/cm ² . Example 4 A sample tape was prepared in the same manner as in Example 1 using the basic composition of Example 1 as a magnetic paint. A 1.0wt%/n-hexane solution of dilauryl phosphite was applied to the magnetic layer of the sample tape.
Application amount of phosphite dilauryl ester is 160mg/
A sample tape was prepared by applying it (top coat) so that it was ² m2. Example 5 A sample tape was prepared in the same manner as in Example 1 using the basic composition of Example 1 as a magnetic paint. A 1.0wt% n-hexane solution of trioleyl phosphorous ester was added to the magnetic layer of the sample tape.
The application amount of phosphite trioleyl ester is 160
A sample tape was prepared by coating (top coat) so that the concentration was mg/m ² . Example 6 A sample tape was prepared in the same manner as in Example 1 using the basic composition of Example 1 as a magnetic paint. A 1.0wt% n-hexane solution of phosphite dioleyl ester was added to the magnetic layer of the sample tape.
Application amount of phosphite dioleyl ester is 160mg/
A sample tape was prepared by applying it (top coat) so that it was ² m2. Example 7 Co was deposited on a polyethylene terephthalate base with a thickness of 12μ by an oblique evaporation method to form a metal ferromagnetic thin film with a thickness of 1000Å. 0.1wt% n- of dilauryl phosphite was applied to the surface of this metal ferromagnetic thin film.
A sample tape was prepared by applying a hexane solution (top coating) so that the coating amount of dilauryl phosphite was 2 mg/m ² . Comparative Example 1 A sample tape was prepared in the same manner as in Example 1 using the basic composition of Example 1 as a magnetic paint. Comparative Example 2 A sample tape was prepared in the same manner as in Example 1 using a magnetic paint obtained by adding 2 parts by weight of trilauryl phosphate to the basic composition of Example 1. Comparative Example 3 A 1.0wt% n-hexane solution of trilauryl phosphate was applied to the magnetic layer of the sample tape obtained in Comparative Example 1 so that the coating amount of trilauryl phosphate was 160 mg/m ² ( top coat)
A sample tape was created. Comparative Example 4 A 1.0wt% n-hexane solution of trioleyl phosphate was applied to the magnetic layer of the sample tape obtained in Comparative Example 1 so that the amount of trioleyl phosphate applied was 160 mg/m ² ( top coat)
A sample tape was created. The properties of the sample tapes prepared in the above Examples and Comparative Examples are shown in the following table.

[Table] In the table above, ◎ is extremely good, ○ is good, △ is poor,
× indicates extremely poor quality. Aging was carried out at 40° C. and 80% for 3 days. The table shows that the magnetic recording medium according to the present invention can suppress the coefficient of friction to an extremely small value and avoid stick slip.In particular, the running deterioration due to aging, which was a conventional problem with magnetic recording media using the top coating method, can be avoided. According to the invention, this problem can be solved.

[Brief explanation of drawings]

1 to 5 are cross-sectional views showing embodiments of magnetic recording media according to the present invention. 1 is the base, 2 is the magnetic layer, 3 is the top coat,
4 and 6 are lubricant coating layers, and 5 is a back coat layer.

Claims (1)

[Claims] 1. A magnetic recording medium having a magnetic layer on a non-magnetic support, characterized in that the magnetic recording medium holds a phosphite represented by the following chemical formula: . [Formula] or [Formula] (However, R ₁ , R ₂ , and R ₃ represent an alkyl group having 8 to 18 carbon atoms.)