JPS6262421A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve the repetitive running durability in a low humidity environment and corrosion resistance in high humidity or condensation state by forming a thin layer of a polyallylamine on a thin ferromagnetic metallic film contg. oxygen and forming a thin layer contg. a fluoroalkyl group-contg. carboxylic acid on the thin layer. CONSTITUTION:The thin polyallylamine layer 3 and the thin layer 4 contg. the fluoroalkyl group-contg. carboxylic acid are formed on the thin ferromagnetic metallic film 2. The polyallylamine used for the thin layer 3 of the polyallylamine is the allylamine polymer expressed by the formula (I). The fluoroalkyl group-contg. carboxylic acid used for the thin layer 4 contg. the fluoroalkyl group-contg. carboxylic acid is the carboxylic acid contg. straight chain or branched perfluoroalkyl groups of >=3C or straight chain fluoroalkyl group having one hydrogen group in the terminal carbon of >=3C within the same molecule.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention is suitable for magnetic recording media such as magnetic tapes and magnetic disks, and particularly relates to a magnetic recording medium suitable for rotary head type video tape recorders.

Conventional technology Iron, cobalt, esters, or alloys containing these as main components are made from polymer films such as polyester films, polyimide films, non-magnetic metal thin sheets, etc. using vacuum film forming methods such as vacuum evaporation, sputtering, and ion blasting. A ferromagnetic metal thin film magnetic recording medium formed on a substrate made of ferromagnetic metal can dramatically improve recording density compared to conventional coated magnetic recording media. It is necessary to make the surface of the magnetic recording medium as flat as possible to reduce the spacing loss between the magnetic head and the magnetic recording medium as much as possible.

However, if the surface is made too flat, head touch and running performance will be affected, so it is necessary to solve this problem by making the surface finely rough and at the same time providing a surface coating made of various organic lubricants or resins. Conventionally, such surface coating materials include lubricants such as various fatty acids, fatty acid esters, fatty acid amides, silico/oil, fluorine oil, etc.
Resins such as polyamide resins and epoxy resins have been used singly or in various composite forms.

In addition, ferromagnetic metal thin films tend to rust when they are left in high humidity for long periods of time or when subjected to humidity cycles and become condensed.To prevent this, ferromagnetic metal thin films In addition to making the ferromagnetic metal thin film contain oxygen by introducing oxygen gas during manufacturing, improvements have been made by adding a rust preventive agent that reacts with the magnetic metal to the surface coating material.

Problems to be Solved by the Invention None of the above-mentioned known surface coatings have any problems with repeated running at normal temperature and normal humidity (for example, 20°C, 60% R, H), but in addition, there is no problem in winter. As a result of studies conducted by the present inventors, it has become clear for the first time that when the humidity drops to 25% RH or less in a room or the like, the durability under repeated running is significantly reduced. To explain it in concrete numbers, a product with 60% RH and odor that could be used without any problem after 50 or more repeated runs, but with 25% RH, 1
After repeated running from 0 to 30 times, a decrease in output and an increase in output fluctuation occurred, and at 20% R, H, such a state occurred after 5 to 20 times. This phenomenon occurs very markedly in ferromagnetic metal thin films that do not have a surface coating, so it is thought that the cause is that adhesion tends to occur between the ferromagnetic metal thin film and the magnetic head when running in low humidity. It is believed that there is.

Furthermore, when adding the above-mentioned rust preventive agent to the surface coating, since the rust preventive agent usually has poor lubricity, it is necessary to sacrifice part of the running performance of the surface coating. Means for Solving the Problems The present invention involves forming a thin layer of polyallylamine on a ferromagnetic metal thin film containing oxygen, and forming a thin layer containing a fluoroalkyl group-containing carboxylic acid on the thin layer. The present invention relates to a magnetic recording medium characterized by the following characteristics, and it solves both of the above-mentioned problems at once with the above-mentioned double thin layer structure.

In other words, the amine group of polyallylamine provides strong adhesion to the oxidized layer on the surface of the ferromagnetic metal thin film, as well as its rust-preventing effect, and the reaction of the fluoroalkyl group-containing carboxylic acid with the above amine group improves the surface of the polyallylamine thin layer. As a result, the effect of improving the affinity with the thin layer containing the 70-roalkyl group-containing carboxylic acid present on its surface, as well as the lubricity and water repellency effects of the thin layer containing the fluoroalkyl group-containing carboxylic acid, etc. Durability for repeated running in low-humidity environments and corrosion resistance in high-humidity or dew condensation conditions are both improved.

EXAMPLES Hereinafter, examples of the present invention will be described with reference to the drawings.

The figure is a diagram showing the basic configuration of a magnetic recording medium in an embodiment of the present invention. In the figure, 1 is a substrate, 2 is a ferromagnetic metal thin film, 3 is a polyallylamine thin layer, 4 is a thin layer containing dust containing a fluoroalkyl group-containing carboxylic acid, and 3 and 4 form a surface broken layer. .

The ferromagnetic metal thin film No. 2 is, for example, Co or Ni formed by oblique evaporation or vertical evaporation.

Metal thin films mainly composed of Fe, etc., or metal thin films mainly composed of alloys thereof (e.g. CoNi, CoCr
etc.), which contains oxygen and is obtained when the atmosphere during film formation is dominated by oxygen gas. The oxygen content is suitably at least 3% or more, preferably 5% or more in terms of atomic ratio to the ferromagnetic metal. If it is less than 3%, the running durability and corrosion resistance in low humidity will deteriorate.As the polyallylamine used for the thin layer of polyallylamine of 03, for example, an allylamine polymer whose structural formula is represented by There is a form of polyallylamine hydrochloride sold by Nittobo Co., Ltd. Polyallylamine hydrochloride can be easily converted into polyallylamine by converting its aqueous solution into polyallylamine through a strongly basic ion exchange resin and then freeze-drying. The polyallylamine thin layer can be formed by dissolving the polyallylamine described above in a solvent such as methanol or ethanol, and applying and drying the solution onto a ferromagnetic metal thin film.

The coating amount is 0.1 per surface after drying.
-soq, more preferably 0.2 to 20 g is suitable.

The fluoroalkyl group-containing carboxylic acid used in the thin layer containing the 70-roalkyl group-containing carboxylic acid of 4 is a linear or branched per-70-roalkyl group having 3 or more carbon atoms, more preferably 5 or more carbon atoms in the same molecule, or , a linear fluoroalkyl group having one hydrogen atom on the terminal carbon having 3 or more carbon atoms, more preferably 5 or more carbon atoms (for example, HCF2CF
A carboxylic acid having one or more 2CF2CF2-), in which the molecular weight ratio of fluoroalkyl groups is 1Q to 80%.
, with a carboxyl group content of 3 to 40% and a molecular weight of 3
．． 000 or less, more preferably 2,000 or less. Note that if an aliphatic hydrocarbon group having 8 or more carbon atoms is included in these molecules, the still regeneration life at low temperatures of 5° C. or lower can be improved. Specific examples of these molecules are shown below.

(#1) n-C3F7COOH (#2) n-C9F19C○OH (#3) n-H(CF)COOH (#4) n-CF90C2H40C2H4CoOH On the polyallylamine thin layer, the 70-roalkyl group-containing carboxylic acid was applied. It is present in a thin layer at a ratio of 0.1 to 500, more preferably 05 to 200, per surface, either alone or as a composite with other lubricants, rust preventives, etc. The thin layer can be formed by directly applying the solution on the polyallylamine thin layer, or by vapor-depositing the polyallylamine itself. ) Sometimes a method of transferring it to the surface of a polyallylamine thin layer is also possible.

The substrate (1 in Figure 1) on which the ferromagnetic metal thin film is to be formed is suitably one that has good macroscopic surface smoothness and has minute protrusions, for example, a substrate with a height of 50 mm on the surface.
A polyester film with an average of 1×10 to 108 wavy or ridged protrusions per 1 mr for ~600 people is
This is particularly preferable.

The specifications and comparative results of the experimental examples and comparative examples will be described below.

Wavy protrusions (surface roughness 100 cycles) obtained by applying and curing a modified silicone emulsion containing a thickener to the surface of a polyester film containing almost no particulates due to polymerization catalyst residue during stretching and film formation. Target 0
A Co Ni ferromagnetic metal thin film (Ni=20%,
A film thickness of 10Q was formed in the presence of a trace amount of oxygen. The oxygen content in the film was 5% compared to the number of atoms. This sample is designated as A. There are several granular protrusions (average height, average diameter of 70 people, average diameter 1 μm) with a gentle slope created by fine silica particles added to the polyester film per 100 μm of surface, and relatively large protrusions caused by fine particles caused by polymerization catalyst residue. The above substrate was formed on the surface of a polyester film with a diameter of about 150 silica colloid particles as the core and about 10 million steep protrusions per 1 mJ using ultraviolet curing epoxy resin as a binder. Co Ni film (N=20%, film thickness 1000
B refers to the substance that formed the oxide (oxygen content: 7%).

Further, as a comparative example, C is a sample B in which no oxygen was introduced during vapor deposition (B in which only the oxygen content was set to be 2 or less). A predetermined amount of polyallylamine methanol solution was applied and dried on these deposited films, and then a predetermined amount of an ethyl acetate solution of various 70-roalkyl group-containing carboxylic acids or a solution prepared by adding stearic acid amide (lubricant) to the solution was applied and dried. Magnetic tapes were made by cutting them into specified widths, and these tapes were heated at 20°C, 20% R, H,
A test video recorder was run repeatedly in an atmosphere of 100 mL, and the number of runs until the playback output decreased by sdB from the initial value was determined. In addition, tapes recorded at 20°C and 60% R,H were heated to 30°C and 80% R,H.

The image was left standing for 10 days, and then the stability (clogging) of the image was examined when it was reproduced at 20° C. and 60% RH. The results are summarized in the table below. In addition, as a comparative example, there is no polyallylamine thin film.
・Low oxygen content in aoCo Ni film ・・
(2) One in which no fluoroalkyl group-containing carboxylic acid is used...Add 0 o'clock and b.

Effects of the Invention As is clear from the above results, the magnetic recording medium of the present invention has a long repeated running life in low humidity and still shows little deterioration in high humidity, making it very useful industrially.

[Brief explanation of drawings]

The figure is a sectional view of a magnetic recording medium according to an embodiment of the present invention. 1...Substrate, 2...Ferromagnetic metal thin film, 3
... Polyallylamine thin layer, 4 is a thin layer containing fluoroalkyl group-containing carboxylic acid. Name of agent: Patent attorney Toshio Nakao and 1 other person/-
-----Kisai anti 2------ G＊B Gen ni 7to residence All Sus 15 Usuzuki 1
3-----Polyallylamine book 1 4-----1 Book book

Claims (1)

[Claims] A magnetic recording medium characterized in that a thin layer of polyallylamine is formed on a ferromagnetic metal thin film containing oxygen, and a thin layer containing a fluoroalkyl group-containing carboxylic acid is formed on the thin layer.