JPH0566652B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a magnetic recording medium comprising a ferromagnetic metal thin film as a magnetic recording layer, and in particular to a metal thin film type magnetic recording medium that has excellent durability in a temperature environment higher than room temperature. be. [Prior Art] Conventionally, magnetic recording media have been made of γ-Fe ₂ O 3 , Co-doped γ-Fe 2 O ₃ , Co-doped γ-Fe ₂ O ₃ ,
Fe ₃ O ₄ , Co-doped Fe ₃ O ₄ , γ-Fe ₂ O ₃ and Fe ₃
Powdered magnetic materials such as bertolide compound of _O4 , magnetic powder such as _CrO2 , or ferromagnetic alloy powder are mixed in an organic binder such as vinyl chloride-vinyl acetate copolymer, styrene-butadiene copolymer, epoxy resin, polyurethane resin, etc. Paint-on type products have been widely used, in which a dispersed material is applied and dried. In recent years, with the increasing demand for high-density recording, vapor deposition methods such as vacuum evaporation, sputtering, and ion plating, or electroplating,
So-called metal thin film magnetic recording media, which do not use a binder and use a ferromagnetic metal thin film formed by a plating method such as electroless plating as a magnetic recording layer, are attracting attention, and various efforts are being made to put them into practical use. There is. Conventional coating-type magnetic recording media mainly use metal oxides, which have lower saturation magnetization than ferromagnetic metals, as magnetic materials, so the thinning required for high-density recording leads to a reduction in signal output, which has reached its limit. Moreover, the manufacturing process is complicated, and it has the drawback of requiring large auxiliary equipment for solvent recovery and pollution prevention. In metal thin film type magnetic recording media, a ferromagnetic metal having a saturation magnetization higher than that of the above-mentioned oxides is formed as a thin film without containing a non-magnetic substance such as a binder, so it can be made ultra-thin for high-density recording. Moreover, the manufacturing process is simple. As one of the requirements for magnetic recording media for high-density recording, high coercive force and thinness have been proposed both theoretically and experimentally. There are great expectations for metal thin film magnetic recording media, which can be easily made small and thin and have a high saturation magnetic flux density. In particular, the method using vacuum evaporation is very advantageous because it does not require drainage treatment as is the case with plating, the manufacturing process is simple, and the deposition rate of the film can be increased. As a method for manufacturing a magnetic film having coercive force and squareness desirable for magnetic recording media by vacuum deposition, the oblique deposition method described in US Pat. Nos. 3,342,632 and 3,342,633 is known. Furthermore, major problems concerning magnetic recording media made of ferromagnetic metal thin films include strength against corrosion and abrasion, and running stability. In the process of recording, reproducing, and erasing magnetic signals, magnetic recording media are subjected to high-speed relative motion with the magnetic head, but in this case, the traveling must be smooth and stable, and at the same time, contact with the head must be maintained. There shall be no wear or damage due to It is also required that recorded signals should not decrease or disappear due to changes over time due to corrosion or the like during storage of the magnetic recording medium. Providing a protective layer is being considered as a method of improving durability and weather resistance. JP-A-50-75001 or JP-A-56 discloses the provision of a monomolecular layer of fatty acid or its metal salt as one of the protective layers of a metal thin film magnetic recording medium.
-Disclosed in No. 41527. By providing a monomolecular layer of a fatty acid or a metal salt thereof (the metal being an alkali metal or an alkaline earth metal), weather resistance, durability, and runnability can be improved. However, the durability of metal thin film magnetic recording media in environments other than room temperature is insufficient, and improvements are still desired when putting metal thin film magnetic recording media into practical use. [Object of the Invention] An object of the present invention is to provide a magnetic recording medium that improves the above-mentioned drawbacks, that is, a new metal thin film type magnetic recording medium that has significantly improved durability in environments at temperatures higher than room temperature. It is. [Structure of the Invention] The present invention relates to a magnetic recording medium characterized in that at least one Langmiur-Blodget polymer film is provided on the surface of a ferromagnetic metal thin film provided on a nonmagnetic support. Furthermore, the present invention relates to the magnetic recording medium, wherein the Langmiur-Blodget polymer film is a film of at least one kind of polymer selected from vinyl stearate, ω-tricosenic acid, and diacetylene derivatives. That is, the present invention comprises forming at least one Langmiur-Blodget polymer film on the surface of a ferromagnetic metal thin film formed by a method such as electroplating, electroless plating, vapor phase plating, sputtering, vapor deposition, or ion plating. The present invention relates to a metal thin film magnetic recording medium. Langmiur-Blodgett polymerization film refers to a monomolecular condensed film formed on the water surface using the Langmiur-Blodgett method [Physical Review 51 ,
964 (1937)] on the surface of a ferromagnetic metal thin film, and then polymerized by irradiation with electron beams or electromagnetic radiation. That is, a fatty acid or the like having a polymerizable double bond in its molecule is dissolved in a volatile solvent such as benzene or chloroform, and this is dropped onto the water surface to form a monomolecular film on the water surface. It is also possible to form a monomolecular film of a metal salt by making an appropriate metal ion exist in water. After that, when the ferromagnetic metal thin film is immersed in water and pulled up, a monomolecular film is transferred onto the metal thin film surface.
By repeating this method, several monomolecular layers are formed on the surface of the ferromagnetic metal thin film. At this time, it is desirable to apply surface pressure from the side to the monomolecular film on the liquid surface in order to make the monomolecular film on the water surface more dense and to facilitate the transfer of the monomolecular film onto the surface of the ferromagnetic metal thin film. In the present invention, the surface pressure is generally 10~
40dynes/cm, particularly preferably 15~
It is 35dynes/cm. The monomolecular film on the surface of the ferromagnetic metal thin film thus obtained is irradiated with electron beams, gamma rays, ultraviolet rays, etc. to polymerize and form a polymer film. Preferred materials for obtaining the polymer film in the present invention include vinyl stearate CH ₃ (CH ₂ ) ₁₆ COOCHCH ₂ ,
ω-tricosenic acid CH ₂ CH (CH ₂ ) ₂₀ COOH, diacetylene derivative CH ₃ (CH ₂ ) _o-1 C ₄ (CH ₂ ) ₈ COOH
(n=8 to 15) A compound having a polymerizable double bond in the molecule. FIG. 1 shows an example of an apparatus for forming a protective lubricant layer according to the present invention. The original magnetic tape 1 on which the ferromagnetic metal thin film has been formed is guided by a guide roller 2 to a protective lubricant layer forming tank 3, where a protective lubricant layer composed of a monomolecular film is formed, and then passed to a take-up roll. 4. The tank 3 is filled with water 9 containing or not containing metal ions, and a monomolecular film 5 is formed on the water surface. The monomolecular film forming material is constantly supplied from a nozzle 8, and a constant surface pressure is applied to the monomolecular film 5 on the water surface by a float 6 and a spring 7. When the original magnetic tape 1 is moved below the water surface or from below the water surface to above the water surface, the monomolecular film 5 on the water surface is transferred onto the surface of the ferromagnetic metal thin film of the original magnetic tape 1. Water 9 containing metal ions is appropriately circulated through a water supply pipe 10 and a drain pipe 11. The original magnetic tape 1 on which the monomolecular film has been formed is irradiated with energy rays 13 from an irradiation source 12 to polymerize the monomolecular film. The number of monomolecular films to be provided as a protective lubricant layer is desirably one or more, up to about 100 layers, in a range where the influence of output reduction due to spacing cloth is small, and it has been found that up to about 10 layers is sufficient. The film thickness is preferably in the range of 15 Å to 2000 Å. In the present invention, the ferromagnetic metal thin film refers to iron, cobalt, nickel, other ferromagnetic metals, or Fe-
Co, Fe-Ni, Co-Ni, Fe-Rh, Co-P, Co
-B, Co-Y, Co-La, Co-Ce, Co-Pr, Co
−Sm, Co−Pt, Co−Mn, Fe−Co−Ni, Co−
Ni-P, Co-Ni-B, Co-Ni-Ag, Co-Ni-
Na, Co−Ni−Ce, Co−Ni−Zn, Co−Ni−Cu,
A ferromagnetic alloy such as Co-Ni-W, Co-Ni-Re, etc. is formed into a thin film by methods such as electroplating, electroless plating, vapor phase plating, vacuum deposition, sputtering, and ion plating. , the film thickness is 0.02 to 2μ when used as a magnetic recording medium.
m, particularly preferably a range of 0.05 to 0.4 μm. The above-mentioned ferromagnetic metal thin film may also include O, N, Cr, Ga,
Ae, Sr, Zr, Nb, Mo, Rh, Pd, Sn, Sb,
It may contain Te, Pm, Re, Os, Ir, Au, Hg, Pb, Bl, etc. Substrates used in the present invention include plastic bases such as polyethylene terephthalate, polyimide, polyamide, polyvinyl chloride, cellulose triacetate, polycarbonate, polyethylene naphthalate, and polyphenylene sulfide, or Al, Ti, and stainless steel. It will be done. [Example] Next, the present invention will be specifically explained with reference to Examples, but the present invention is not limited thereto. Example 1 Co-coat was applied to a 1/2 inch wide, 15 μm thick tape-shaped polyethylene terephthalate film using a continuous plating device using the following plating solution and plating conditions.
A P (Co: 98%, P: 2%) magnetic film was electrolessly plated to a thickness of 0.25 μm. As a pretreatment liquid for electroless plating, Schumer Sensitizer and Schumer Activator from Nippon Kanigen Co., Ltd. were used. Cobalt chloride (CoCl ₂ 6H ₂ O 9.58g/hypophosphorous acid leader (NaH ₂ PO ₂・H ₂ O)
5.3g / ammonium chloride 10.7g / citric acid 26.5g / boric acid 30.9g / [Plating conditions] PH: 7.5, liquid temperature: 80℃ Furthermore, the apparatus shown in Figure 1 was applied on the Co-P electroless plating magnetic film. A Langmiur-Blodget polymer film was formed using the following method. At this time, the surface pressure is 32dynes/
cm, and barium chloride was dissolved in water 9 in tank 3. Vinyl stearate, ω-tricosenic acid, and diacetylene derivatives were used as monomolecular film forming materials, and after forming three monomolecular films, γ
Polymerization was carried out by irradiation with beams, electron beams, and ultraviolet rays. Furthermore, for comparison, a sample in which three monolayers of barium salt of stearic acid were formed was also prepared. 40℃, 30% of the magnetic tape thus obtained
Table 1 shows the relative humidity and still durability of β-type VTRs in an environment of 40°C and 80% relative humidity.

【table】

[Table] Example 2 A 12.5 μm thick polyethylene terephthalate film was installed in a winding vacuum evaporation device, and Co75
% by weight and 25% by weight of Ni was evaporated from an electron beam evaporation source, and the vapor flow with an incident angle of 60° to 90° reached the polyethylene terephthalate film moving along the cooling can, so that it was evaporated to a thickness of 0.15 μm. I forced it. At this time, oxygen gas was introduced near the incident angle of 60° of the vapor flow. Various Langmiur-Blodget polymer films were formed on the vapor-deposited magnetic film thus obtained in the same manner as in Example 1. At this time, the surface pressure was 28 dynes/cm, and five monomolecular layers were formed. Furthermore, for comparison, a sample in which five monomolecular films of palmitic acid were formed was also prepared. 40 of the magnetic tape thus obtained
Table 2 shows the still durability of VHS type VTRs measured at 30% relative humidity at 40°C and 80% relative humidity at 40°C.

〔Effect of the invention〕

A magnetic recording medium in which at least one layer of Langmiur-Blodget polymer film is provided on a ferromagnetic metal thin film is a metal thin film type magnetic recording medium that has excellent durability under a temperature and humidity environment higher than room temperature.

[Brief explanation of the drawing]

FIG. 1 shows an example of an apparatus for manufacturing the magnetic recording medium of the present invention. DESCRIPTION OF SYMBOLS 1... Original magnetic tape, 2... Guide roller, 3... Water tank, 4... Winding roll, 5... Monomolecular layer, 6... Float, 7... Spring, 8... Nozzle, 9... ...Water, 10...Water pipe, 11...Drainage pipe, 12...Energy ray irradiation source, 13...Energy ray.

Claims (1)

[Claims] 1. A Langmiur-Blodgett polymer film of a compound having a polymerizable double bond in the molecule of at least one layer is provided on a ferromagnetic metal thin film provided on a non-magnetic support. magnetic recording medium. 2. The magnetic recording medium according to claim 1, wherein the Langmiur-Blodget polymer film is a film of at least one kind of polymer selected from vinyl stearate, ω-tricosenic acid, and diacetylene derivatives.