JPS6196513A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a magnetic recording medium having superior traveling performance and wear resistance especially in an atmosphere at high temp. and humidity by forming a monomolecular film of a fluorine substituted fatty acid or a metallic salt thereof on the surface of a thin ferromagnetic metallic film formed on a nonmagnetic support. CONSTITUTION:A fluorine substituted fatty acid represented by formula I (where 5<=l<=23, m+n=2l+1, and mnot equal to 0), preferably a fluorine substituted fatty acid represented by formula II (where 4<=n<=20) or a metallic salt thereof is fed from a nozzle 8 to form a monomolecular film on the surface of water or a metallic salt soln. 9 in a tank 3 for forming a protective lubricating layer. A magnetic tape 1 obtd. by forming a thin ferromagnetic metallic film on a nonmagnetic support such as a polyester film is introduced into the tank 3 with guide rolls 2 and passed across the monomolecular film plural times. The monomolecular film is kept under fixed surface pressure applied by a float 6 and a weight 7 connected to the float with a line. Thus, a thin metallic film type magnetic recording medium having high durability is obtd. This medium has superior traveling stability and wear resistance, and these properties are maintained even in an atmosphere at high humidity.

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 particularly relates to a metal thin film magnetic recording medium that has excellent runnability and wear resistance in a high humidity atmosphere. It is related to recording media.

[Prior art]

Conventionally, as a magnetic recording medium, γ-
Fe2O3, Co-doped r-Fe203, Fe
304, C, doped r-FexOa, Fe3O
4.d Application-type products, in which the dispersed material is dried on a cloth, have been widely used. In recent years, with the increasing demand for high-density recording, ferromagnetic metal thin films formed by ENO deposition methods such as vacuum evaporation, star/R stumbling, and ion blating, or plating methods such as electroplating and electroless plating have been developed. A so-called metal thin film type magnetic recording medium that does not use a binder as a recording layer is attracting attention, and various efforts are being made to put it into practical use.

Conventional coating-type magnetic recording media mainly use metal oxides, which have lower saturation magnetization than ferromagnetic metals, as magnetic materials, so the thinner layers required for high-density recording reduce signal output, and The manufacturing process is also complicated, and it has the disadvantage of requiring large auxiliary equipment for solvent recovery and pollution prevention. In metal thin film type magnetic recording media, a ferromagnetic metal with 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 is possible to make ultra-thin layers for high-density recording. Moreover, the manufacturing process is simple.

As one of the conditions required for magnetic recording media for high-density recording, high coercive force and thinner layers have been proposed both theoretically and experimentally. There are great expectations for metal thin film magnetic recording media, which can easily be made twice as thin and have a high saturation magnetic flux density.

In particular, the method using vacuum evaporation has great advantages because it does not require waste liquid treatment as in the case of plating, the manufacturing process is simple, and the deposition rate of the film can be increased. A method for manufacturing a magnetic film having coercive force and squareness desirable for magnetic recording media by vacuum deposition is disclosed in the US Patent JJ$JAjJ.
The oblique vapor deposition method described in No. 33, No. 33, No. 33, etc. is known. On the other hand, corrosion and wear are major problems associated with magnetic recording media made of ferromagnetic metal thin films. In the process of recording, reproducing, and erasing magnetic signals, the magnetic recording medium is subjected to high-speed relative motion with the magnetic head, but in this case, the movement must be smooth and stable, and at the same time, contact with the head and Abrasion or destruction must not occur. It is also required that the 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. Therefore, providing a protective layer is being considered as one method for improving durability and weather resistance.

JP-A-Sho proposed that a monomolecular layer made of a metal salt of sardine containing a fatty acid be provided as one of the protective layers for metal thin film magnetic recording. 0-7. t00/ issue or JP-A-74-1/7.2
It is disclosed in No. 7. By providing a monomolecular layer of a fatty acid or a metal salt thereof (the metal is an alkali metal or an alkaline earth metal), weather resistance, durability, and runnability can be improved.

However, the runnability of metal thin film magnetic recording media is insufficient in environments other than normal temperature and humidity, especially under high humidity, and improvements are still desired for the practical use of metal thin film magnetic recording media.

[Structure of the invention]

The present invention relates to a magnetic recording medium comprising at least one monolayer of a fluorine-substituted fatty acid or a metal salt thereof on the surface of a ferromagnetic metal thin film provided as a magnetic recording layer on a nonmagnetic support.

A monomolecular film is a film in which single molecules are regularly and densely arranged and attached to a liquid or solid surface.
The film thickness is equivalent to the length of one molecule. Methods for forming a monomolecular film on the surface of a ferromagnetic metal thin film include coating, vapor deposition, and precipitation on a solid surface from an amphoteric solvent, but Langmuir-Brosietz is particularly preferred! (PNys'?cal Re'vrewj
/ , F A 4! (/ri37)]. That is, a fluorinated fatty acid is dissolved in a volatile solvent such as benzene or chloroform, and the solution is dropped onto the surface of water or a salt solution containing Vi covalent metal ions (hereinafter referred to as the lower layer liquid). Form a monolayer. When a ferromagnetic metal thin film is immersed in a lower layer liquid and pulled up, fluorinated fatty acids are found on the surface of the metal thin film (if the lower layer liquid contains metal ions, some or all of the fluorinated fatty acids may be metal salts). ) is transferred. By repeating this method, many layers of monomolecular films are formed on 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 metal thin film.

In the present invention, the surface pressure is generally 1o-4t.

d y n e / cm, particularly preferred is /
! -37 dyne/cm.

The time for which the metal thin film magnetic recording medium material is immersed in the liquid underlying the monomolecular film is preferably 7 minutes or less, particularly preferably 20 seconds or less.

The fluorine-substituted fatty acid that can form a monomolecular layer is represented by the following general formula.

That is, ClF m Hn COOH where l, m, n' are! ≦l≦-J, m+n=, 2A
+/, is a positive integer that satisfies the relationship m−O.

Specific examples of the compound represented by the above general formula include monofluorocaprylic acid, l-fluoroslargonium perfluorocapric acid, monofluoroundecylic acid, perfluorolauric acid, and monofluoro-fluorocaprylic acid. tridecylic acid, monofluoromyristic acid, monofluoropentadecyl acid, monofluoropalmitic acid, perfluoropalmitic acid, perfluoroheptadecylic acid, perfluorostearic acid, perfluorononadecanoic acid,
Flea-fluoro fatty acids such as no-fluoroaracic acid, perfluorobenhenic acid, no-fluoroundecylenic acid, and perfluorooleic acid, co, λ,! ,! , daytime, ≠,! ,
j.

A, 4, 7, 7. r, r, ri, ri, 10,10°//,
//, /co, 12-docosafluorolauric acid, 44,
4! , j, j, A, 4, 7, 7. , r, r.

Ri, Ri, 10,10,10-pentadecafluorocapric acid, Hiro, Hiro, j, j, lx, t, 7,7゜r, r, y
,ri,10,10. // , I/ , /2°/co, /cohebutadecafluorolauric acid y.

Ir, 9. ? , 10,10,10-hep fi 7 k
Fatty acids such as O-O-capric acid in which some of the hydrogen atoms in the alkyl groups are replaced with fluorine are used.

Among the above compounds, preferred ones are further represented by the following general formula.

That is, CFa　(CF2　)nCOOH Here, n is an integer that satisfies the relationship of ≠≦n≦20.

More preferred are fluorine-substituted saturated fatty acids having 7 to 17 carbon atoms, and preferably those in which the ratio of the number of hydrogen atoms to fluorine atoms in the molecule is within a range of 2:I-0:/.

FIG. 7 shows an example of a device for forming a retained lubricant layer according to the present invention. The original magnetic tape on which the ferromagnetic metal thin film is formed is transferred to the protective lubricant layer forming tank 3 by a guide roller.
After forming a protective lubricant layer made of a monomolecular film, the material is wound onto a take-up roll. Tank 3 contains water or Ca.

A salt solution containing gold ions such as Cd, C0% Mnb Pb% Nix Fe, etc. is filled, and a monomolecular film j of fluorinated fatty acids is formed on the liquid surface.

The fluorinated fat rrl is constantly supplied from the nozzle t, and a constant surface pressure is applied to the monomolecular HHs K on the liquid surface by the float 6 and the weight 97 connected to the float by a thread. When the original magnetic tape is moved below the water surface or from below the water surface to above the water surface, the monomolecular film on the water surface is transferred onto the thin ferromagnetic metal surface of the original tape. It will be relocated. Water or a salt solution containing metal ions is appropriately circulated through the water supply pipe 10 and the drain pipe. It has been found that a range in which the effect of output reduction due to spacing loss is small up to about 0 layers is preferable, and it is sufficient to have up to about 10 layers.

The film thickness is /,! A range of nnm-100n is preferred.

When providing a monomolecular film with multiple layers, different types of molecules can be used for each layer. In this case, the bottom layer is a monomolecular layer consisting of molecules other than fluorinated fatty acids or their metal salts,
It can also be used in combination as an intermediate layer or top layer.

In the present invention, the ferromagnetic metal thin film refers to iron, cobalt, nickel and other ferromagnetic metals, fiFe-C0, Fe-
Ni, Co-Ni, Fe-RhbCo-P% Co-8
%Co-Y, Co-La.

Co-Ce, Co-Pi, Co-8m, Co-Mn,
Fe-Co-Ni%Co-Ni-P, C
.

-Ni-B, Co-N, i-Ag, Co-Ni -Nd
% Co-Ni -Ce% Co-N 1-ZnbCo
- Electroplating, electroless plating, vapor phase plating, etc. of ferromagnetic alloys such as Ni-Cu, Co-N1-W, Co-Ni-Re, etc.
It is formed by methods such as snottering, vapor deposition, and ion blating, and its film thickness is in the range of O6O λμ when used as a magnetic recording medium, especially in the range of Q, θj -0, and hiμm. is desirable.

The above ferromagnetic metal thin film also has 0. N.cr.

G a b As y S r % Z r % N
b, M O% Rh %pd, Sn, Sb, Tes
Pmb le, 08% I r, Au, Hg% Pb, B
etc. may be included.

Non-magnetic supports used in the present invention include plastic bases such as polyethylene terephthalate, polyimide, polyamide, polyvinyl chloride, cellulose triacetate, polycarbonate, polyethylene naphthalate, and polyphenylene sulfide, as well as ViAI, Ti, stainless steel, etc. be done.

〔Example〕

EXAMPLES Next, the present invention will be specifically explained with reference to Examples, but the present invention is not limited thereto.

Example 1 A cobalt-nickel (Ni:, 20 wt%) magnetic film (thickness: 061! μm) was obliquely deposited on a 20 μm thick polyethylene terephthalate film to prepare a raw material for a magnetic recording medium. An electron beam evaporation source is used as the evaporation source.
Cobalt-nickel alloy (Co:JrOwt%,
Ni: 2c%) was charged and the degree of vacuum was j-1z10(-j
) Oblique vapor deposition was performed in Torr so that the incident angle was 70 degrees. Monomolecular films of various fluorinated fatty acids or metal salts thereof were deposited in three layers on the magnetic metal thin film of the obtained magnetic recording medium using the apparatus shown in FIG. Shown in Table/ as samples A/~7.

At this time, the surface pressure was J Odyne/cm, and the temperature of the lower liquid in tank 3 was 0°C. Further, a comparison sample prepared by dissolving iMEK chili-fluorocaprylic acid and coating it on the above magnetic recording medium original fabric and drying it to give a total fabric weight of 7.5 m1iI/7FL2 was designated as "IT".

The friction coefficient μ of the magnetic tape thus obtained against a stainless steel bar at 4co 0c and 0 RH, and the durability of repeated running on a VH8 type VTR were investigated, and the results are shown in Table 1.

Here, the repeated running durability is 0m long tape.
8WV'rR (Matsushita Kisangyo NY, R, 200 type) is used to repeatedly play the data, and the number of plays is shown in the trenches where the screen is disturbed due to unstable running and the running stops due to an increase in the coefficient of friction.

In this way, metal thin film magnetic recording, which is formed by providing a monomolecular film of fluorinated fatty acid or its metal salt on the surface, has a μ value,
It is clear that it has excellent repeatability.

〔Effect of the invention〕

A magnetic recording medium comprising at least one monolayer of a fluorinated fatty acid or a metal salt thereof on a ferromagnetic metal thin film is a metal thin film type magnetic recording medium that has excellent running durability in an atmosphere with higher humidity than normal humidity. be.

[Brief explanation of drawings]

FIG. 1 shows an example of an apparatus for manufacturing the magnetic recording medium of the present invention. /...Magnetic tape material...Guide roller 3...Water tank Hiroshi...Take-up roller j...Monolayer 6...Float 7...Weight r...Nozzle...・Water or water containing metal ions (lower layer liquid) 10
... Water supply pipe // ... Drain pipe patent applicant Fuji Photo Film Co., Ltd. Figure 1 Procedure Amendment Showa! December 2nd year t2-day

Claims (4)

[Claims] (1) A magnetic recording medium characterized in that at least one monomolecular film of a fluorine-substituted fatty acid or a metal salt thereof is provided on the surface of a ferromagnetic metal thin film provided on a nonmagnetic support. (2) The magnetic recording medium according to claim (1), wherein the monomolecular film is formed by a Langmuir-Blodgett method. (3) The magnetic recording medium according to claim (1), wherein the fluorinated fatty acid is represented by the following general formula. C_lF_mH_nCOOH where l, m, n are 5≦l≦23, m+n=2l+1
, m≠0. (4) The magnetic recording medium according to claim (1), wherein the fluorinated fatty acid is represented by the following general formula. CF_3(CF_2)_nCOOH Here, n is an integer that satisfies the relationship 4≦n≦20.