JPS6295733A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a medium film having a high grade by using coating compd. prepd. by incorporating a fluorine surface active agent into an alcohol solvent and/or benzene solvent is used as an overcoat of a magnetic recording medium of a thin ferromagnetic metallic film. CONSTITUTION:An Co-Ni content contg. 20wt% Ni is deposited by evaporation to about 1,000Angstrom thickness on a substrate consisting of a PE terephthalate, etc. and the coating compd. consisting of the solvent into which the potassium salt of a peralkyl carboxlic acid is dissolved to 0.15% concn. is coated on the surface thereof. The coating is dried to about 5mum wet film thickness in this stage to decrease the volume. The coating material may be pefluoroalkyl quaternary ammonium iodide in addition to the above-mentioned potassium salt. Generation of uneven coating is obviated in either case. Ethyl Cellsolve, toluene, etc. are used for the solvent.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a magnetic recording medium, and more specifically to a method for manufacturing a magnetic tape with high film quality of the medium constituent layers provided on the medium.

(Prior Art) Magnetic recording media such as magnetic tapes, magnetic sheets, and magnetic disks are widely used in the audio, video, and computer fields. For example, magnetic tapes have traditionally been coated with ferromagnetic powder dispersed in a binder, but as the demand for high-density recording has increased recently, the recording density has become smaller due to the binder. Instead of this coated type, thin film magnetic recording media are often used, which have a high saturation magnetization and can form a ferromagnetic metal thin film on a support by direct vapor deposition, sputtering, ion blasting, etc. without the need for a binder. It's starting to look like this.

However, the ferromagnetic layer of such a thin film type recording medium has a large coefficient of friction, so when it is run on, for example, a video deck, it may be rubbed by a magnetic head, producing a frictional noise called tape squeal. When this friction is severe, the tape may stop. Not only does it have poor running performance, but it is also prone to scratches due to friction with magnetic heads, idle rollers, liners, etc.

For this reason, the so-called still durability, which is when a videotape is played back on a deck and the fused image is viewed, and the so-called repeat durability, which is when this tape is played repeatedly and its durability is seen, are significantly inferior to those of the coated type, making it impractical for practical use. The current situation is that it cannot withstand use. Furthermore, when a thin metal film is exposed to the air, the metal is oxidized by the presence of oxygen and moisture, resulting in poor corrosion resistance and storage stability. For example, iron oxide no longer exhibits magnetism, which not only reduces the recording density as a recording medium, but also corroded or scratched areas can cause noise.

Furthermore, damage to the deck circuit member and the back coat layer itself has been a problem with the back foot layer in which filler is dispersed to improve running performance and lubricity.

To solve these problems, a ferromagnetic metal thin film, and if necessary, a coating film (overcoat layer) on the back coat layer.
However, in this case, it is necessary to reduce the film thickness in order to reduce so-called spacing loss, which accompanies loss of output when scanning the magnetic layer with a magnetic head.

In order to solve these problems, various inorganic or organic compounds have been conventionally attached to or overcoated on the surface of the magnetic layer. For example, JP-A-56-143
No. 540 discloses a magnetic recording medium in which a metal thin film layer is provided with a layer mainly composed of polyurethane resin. Furthermore, Japanese Patent Laid-Open No. 133631/1983 discloses a magnetic recording medium in which a sorbitan ester is deposited on a metal thin film layer. However, these materials are not practically sufficient in terms of durability, especially when rubbed by a magnetic head. Also, JP-A-5
No. 8-146027 discloses a magnetic recording medium in which a surface treatment film made of phosphate ester or its metal salt is provided on a metal thin film. The invention also states that metal salts of phosphoric acid esters are preferred. However, even with this metal salt of phosphoric acid ester, durability such as the above-mentioned tape squeal and still durability is not sufficient.

On the other hand, fluorine-based surfactants are known to be useful for meeting the above needs. Furthermore, when using the above-mentioned method, there is a problem in coating properties, and the coating liquid is repelled, impairing the homogeneity of the layer surface and causing problems in electromagnetic conversion.

This is especially true for fluorine-based surfactants.

If the uniformity of the coating is poor, the output will decrease, running performance and durability will deteriorate, and dropouts will also increase.

Recent trends in magnetic recording technology include, for example, in audio tapes, there is a shift from compact cassettes to microcassettes, and in the video field, from VH8 and β formats for manuscripts to 8mm video, With the shift to electronic cameras, all of them are becoming smaller, more dense, and more precise. There is a demand for magnetic tapes with good surface homogeneity, that is, high film quality.

(Object of the Invention) An object of the present invention is to provide a magnetic recording medium with good film quality, particularly in an overfooted ferromagnetic metal thin film type.

Another object of the present invention is to provide a magnetic recording medium that is free from dropouts, has good running properties, and has good corrosion resistance.

(Determination of the invention) According to the object of the present invention, on the layer surface of the constituent layers of the magnetic recording medium,
This is achieved by a magnetic recording medium coated with a coating containing a fluorine-based surfactant dissolved in an alcohol-based solvent and/or a benzene-based solvent.

When an alcohol solvent and a benzene solvent are used together, the fluorine surfactant according to the present invention may be dissolved in either solvent first or in a mixed solvent.

Next, the present invention will be explained in detail.

In the present invention, the paint containing the fluorine-based surfactant can be applied using a coating type in which a magnetic paint containing magnetic powder or the like as a binder is applied onto a support, or a coating type in which a ferromagnetic metal thin film is applied on a support by a method such as vapor deposition. Although it can be applied to any thin-film type magnetic recording medium provided directly on the magnetic recording medium, the effect is most pronounced in the thin-film type. Furthermore, it may be applied to the layer surface of a back coat layer containing a nonmagnetic filler.

When applied to a coating type, the applied magnetic layer or back coat layer may be dried or not dried.

When the fluorine surfactant paint according to the present invention is applied to the surface of the constituent layers of a recording medium, the undried coating thickness is 30 μm or less, preferably 10 μm or less, and more preferably 5 to 0.5 μm. If it is too thick, the homogeneity of the layer surface will be impaired, and if it is too thin, the film quality cannot be maintained and important effects such as lubricity, corrosion resistance, and durability will be lost.

In addition, in the above coating thickness, the amount applied to the layer surface is Q, 5-30
ng/m2, preferably 1 to 10+ag/m2.

Note that other lubricants soluble in the solvent according to the present invention may be used in combination.

Further, it is preferable that 50 to 300 rows of mechanical protrusion veins are formed per 100 μm on the surface of the magnetic layer.

Next, specific examples of the solvent according to the present invention will be given.

[Example aromatic solvent]

benzene toluene xylene etc. Among these, toluene is preferred.

[Example alcoholic solvent]

Examples include methyl cellosolve, methyl cellosolve, butyl cellosolve, methanol, ethanol, n-bunopanol, isopropanol, n-butanol, amyl alcohol, and the like, with methyl cellosolve, ethyl cellosolve, isopropanol, and the like being preferred.

The preferred mixing range is aromatic/alcoholic 20/80
~80/20, but aromatic systems are 70/20 from the viewpoint of solubility.
/ It is preferable not to exceed 30.

Examples of fluorine-based surfactants include perfluoroalkylcarboxylic acid or its metal salt or ammonium salt perfluoroalkylsulfonic acid or its metal salt or ammonium salt perfluoroalkyl quaternary ammonium halide perfluoroalkyl polyoxyethylene ether/- and fluorinated alkyl esters. These are FC-93 and FC-95 from 3M.
, FC-98, FC-129, FC-135, FC-1
It is commercially available as 70, FC-430, FC-431, etc.

Among these, perfluoroalkyl carboxylic acids or their metal salts or ammonium salts and perfluoroalkyl quaternary ammonium halides are particularly preferred.

The preferred concentration range is 0. Of~1.0%.

To apply this paint, there is a dipping method where the paint is immersed in the paint, a reverse roll method where the paint is applied,
The extrusion method, doctor blade method, gravure printing method, spray method, etc. are used, and the coating film applied by these methods is dried by ordinary means.

The ferromagnetic metal thin film in the present invention is Fe.

Metals such as Co%Ni or Fe-Co, Fe-old, C
o-old, Fe-C.

-Ni, Fe-Rh, Fe-Cu, Co-Cu5Co-
＾u%Co-Y, Co-La, Co-r'r.

Co-Gc1%Co-5m, Co-Pt, Ni-Cu,
Mn-B15Mn-Sb, Mn-^mi, Fe-Cr,
Co-Cr, Ni-Cr, Fe-Co-Cr5Fe-C
A ferromagnetic alloy such as o-Ni-Cr formed into a thin film by vacuum deposition is used. This metal
The thickness of the film is preferably between 500 and 5,000 degrees.

Furthermore, those deposited in an oxygen atmosphere exhibit better durability.

As for the coated magnetic layer and back coat layer, conventional techniques can be mainly used.

The support on which the metal thin film is formed may be a plastic base such as polyester, polyethylene terephthalate, polyimide, polyamide, polyamideimide, polyvinyl chloride, cellulose triacetate, polycarbonate, polyethylene naphthalate, or an A or AQ alloy, A metal plate such as T1, Ti alloy, or stainless steel is used.

(Example) Next, the present invention will be described in detail, but the present invention is not limited thereto.

Example 1 Co on polyethylene terephthalate with a thickness of 12μIn
-N1 (Ni 20% by weight) was deposited to a thickness of 1000^ while introducing oxygen to form a ferromagnetic metal thin film layer.

On this ferromagnetic metal thin film, a wet film was applied by dissolving 3M's FC-129, a type of potassium salt of perfluorofurkylcarboxylic acid, in a solvent as shown in Table 1 to a concentration of 0.15%. It was applied using a reverse roll coater to a thickness of 5 μm and dried.

The occurrence of coating unevenness was investigated by observing the magnetic surface before and after drying.

The results are shown in Table 1.

Table 1 Example 2 The occurrence of uneven coating was investigated in the same manner as in Example 1. However, instead of FC-129, perfluoroalkyl quaternary
FC-1 manufactured by 3M Company, which is a type of ammonium iodide
35 was used.

The results were similar to those in Example 1.

Claims (1)

[Claims] A magnetic recording medium characterized in that a paint containing a fluorine-based surfactant dissolved in an alcohol-based solvent and/or a benzene-based solvent is applied to the surface of the constituent layers of the magnetic recording medium.