JPS63281217A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve a traveling property, wear resistance and durability by forming a top coating layer contg. thiohypophosphate and fluorine lubricating agent on a thin ferromagnetic metallic film. CONSTITUTION:The thin ferromagnetic metallic film is formed on a nonmagnetic base and the top coating layer contg. the thiohypophosphate and fluorine lubricating agent is formed thereon. The thiohypophosphate is easily obtd. by bringing mercaptan and phosphorus trichloride into reaction in the presence of pyridine. The good adhesiveness to the thin ferromagnetic metallic film is thereby obtd.; in addition, a high lubricating effect is obtd. by the decreased coefft. of friction. Such adhesion and lubricating effect are obtainable even under conditions of a high temp. and high humidity or under conditions of a low temp. like under ordinary conditions.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a so-called magnetic layer in which a ferromagnetic metal thin film is formed as a magnetic layer on a non-magnetic support by vacuum thin film forming techniques such as vacuum evaporation and sputtering. The present invention relates to a ferromagnetic metal thin film type magnetic recording medium.

[Summary of the invention]

The present invention provides a magnetic recording medium in which a ferromagnetic metal thin film is formed as a magnetic layer on a non-magnetic support, and a top layer containing a thiophosphite and a fluorine-based lubricant on the ferromagnetic metal thin film as the magnetic layer. The objective is to provide a magnetic recording medium that has a coating layer and exhibits excellent running properties, wear resistance, and durability under all conditions of use.

[Conventional technology]

Conventionally, as a magnetic recording medium, 7-
7-Fe, O,, Fe5O containing Fe, O,, Co
i, Pe5o containing Co, 7 Fe*Os and F
Powder magnetic materials such as ferromagnetic powders such as ferromagnetic powders such as ferromagnetic powders such as ferromagnetic powders such as ferromagnetic powders containing e and 04, ferrolide compounds containing co, or alloy magnetic powders whose main components are Fe, Co, Ni, etc., are combined with vinyl chloride-acetic acid. BACKGROUND ART Coating-type magnetic recording media are widely used, which are manufactured by applying and drying a magnetic paint dispersed in an organic binder such as a vinyl copolymer, polyester resin, or polyurethane resin.

On the other hand, with the increasing demand for high-density magnetic recording, ferromagnetic metal materials such as Go-Ni alloys can be made into polyester by plating or vacuum thin film formation technology (vacuum evaporation method, sputtering method, ion blating method, etc.). 2. Description of the Related Art Magnetic recording media of the so-called ferromagnetic metal thin film type, which are directly deposited on a non-magnetic support such as a film or a polyimide film, have been developed and are attracting attention. This ferromagnetic metal thin film type magnetic recording medium not only has excellent coercive force and squareness ratio, and has excellent electromagnetic conversion characteristics at short wavelengths, but also has the ability to make the thickness of the magnetic layer extremely thin, making recording demagnetization possible. It has many advantages, such as extremely small thickness loss during playback and reproduction, and the ability to increase the packing density of the magnetic material since there is no need to mix an organic binder, which is a non-magnetic material, into the magnetic layer.

However, in the above-mentioned ferromagnetic metal thin film type magnetic recording medium, the surface smoothness of the magnetic layer is extremely good, so the substantial contact area is large, making it easy for adhesion phenomena (so-called sticking) to occur and friction. The coefficient becomes larger, etc.
It has many shortcomings in terms of durability, running performance, etc., and improving them is a major issue.

In general, a magnetic recording medium is subjected to high-speed relative motion with a magnetic head during the process of recording and reproducing magnetic signals, and must run smoothly and stably at this time. Further, it is better to minimize wear and damage caused by contact with the magnetic head.

For example, attempts have been made to improve the durability and runnability by coating the magnetic layer of the magnetic recording medium, that is, the ferromagnetic metal thin film, with a lubricant to form a protective film.

[Problem that the invention seeks to solve]

By the way, when a protective film is formed by applying a lubricant as described above, this protective film exhibits good adhesion to the ferromagnetic metal thin film that is the magnetic layer and exhibits a high lubrication effect. This is required.

Furthermore, these adhesion properties and lubrication effects must be excellent both under hot and humid conditions, such as in tropical and subtropical regions, and under low-temperature conditions, such as in cold regions.

However, the operating temperature range of conventionally widely used lubricants is limited, and in particular, many of them solidify or freeze at low temperatures such as θ to -5℃, so it is difficult to fully demonstrate their lubricating effect. I couldn't do that.

Therefore, the present invention improves runnability and durability by forming a top coat layer on a ferromagnetic metal thin film that maintains adhesion and lubricity under any usage conditions and maintains a lubricating effect over a long period of time. The purpose is to provide excellent magnetic recording media.

[Means for solving problems]

As a result of intensive research to achieve the above-mentioned objective, the present inventors have found that a lubricant containing a fluorine-based lubricant with a thiophosphite added exhibits a good lubricating effect over a wide temperature range. Heading This invention has been completed, which comprises forming a ferromagnetic metal thin film on a non-magnetic support, and forming a top coat layer containing a thiophosphite and a fluorine-based lubricant on the ferromagnetic metal thin film. It is characterized by the formation of

The thiophosphite used in the present invention has the general formula % formula % (1) This is a compound represented by

The hydrocarbon group R in the above formula (1) may be linear or branched, and may further contain a double bond, an aromatic ring, etc., but the number of carbon atoms in the above R is linear. In the case of 14~
30, preferably 6 to 30 in the case of a branched structure, and 3 to 30 in the case of a double bond.

The thiophosphite represented by (I) above can be easily obtained by reacting a mercaptan and phosphorus trichloride in the presence of pyridine.

On the other hand, the fluorine-based lubricants used include perfluoroalkyl carboxylic acid or its metal salt, perfluoroalkyl carboxylic acid ester, perfluoroalkyl ethylene oxide, perfluoropolyethers, perfluoroalkyl sulfonic acid or its ammonium salt, or Metal salts thereof, perfluoroalkyl carboxylic esters, perfluorothiol carboxylic esters, perfluoroalkyl dicarboxylic acids, perfluorodicarboxylic esters, perfluoroalkoxyalkyl carboxylic esters, perfluoroalkyl perfluorocarboxylic esters, fluorocarbons polyurethanes or polyureas containing chains, perfluorocarboxylic acid amides, sulfonic acid perfluoroesters, N-perfluorophenylcarboxylic acid amides, perfluorobenzoic acid esters, sulfonated N-alkyl perfluoroalkanamides, N-alkylper Examples include fluoroalkanamide, perfluoroalkylsulfonic acid tetraalkylammonium salt, N-perfluoroalkylalkanamide or alkenamide, polyperfluoroalkanamide compound, poly(N-perfluoroalkylcarbamoyl) derivative, perfluoroalkylthiophenol, etc. be done.

The lubricant contained in the protective film may be only the thiophosphite and fluorine-based lubricant according to the present invention, but by mixing it with a conventionally known lubricant, the temperature range of use can be further expanded. be able to.

Lubricants used for this purpose include resin acids or their metal salts, fatty acid amides, fatty acid esters, fatty alcohols or their alkoxides, fatty amines, polyhydric alcohols, sorbitan esters, manniratan esters,
Examples include sulfurized fatty acids, aliphatic mercaptans, modified silicone oils, higher alkylsulfonic acids or metal salts thereof.

Furthermore, in order to cope with more severe usage conditions and maintain the lubricating effect, a weight ratio of 30 (lubricant) is added to the protective film.
: 70 (extreme pressure agent) to TO: The extreme pressure agent can be contained at a blending ratio of about 30.

The extreme pressure agent mentioned above acts to prevent friction and wear by reacting with the metal surface due to the accompanying frictional heat when metal contact occurs partially in the boundary lubrication area, and forming a reaction product film. Among these, phosphorus-based extreme pressure agents, sulfur-based extreme pressure agents, halogen-based extreme pressure agents, organic metal-based extreme pressure agents, composite type extreme pressure agents, etc. are known.

The above-mentioned extreme pressure agents may be used alone, but it is also possible to use a mixture of two or more types.

A method for depositing a lubricant layer containing these thiophosphite and fluorine-based lubricant on a ferromagnetic metal thin film is to dissolve the above lubricant in a solvent and apply the resulting solution to the surface of the ferromagnetic metal thin film. The ferromagnetic metal thin film may be coated or sprayed on the solution, or conversely, the ferromagnetic metal thin film may be immersed in this solution and dried.

Here, the coating amount is 0.5B/a” to 1100a/
@” is preferable, and 1 a+g/m' to 2G+a
g/a" is more preferable. If the coating amount is too small, the effects of lowering the friction coefficient and improving wear resistance and durability will not be achieved. On the other hand, if it is too large, the strength of the sliding member A sticking phenomenon occurs between the magnetic metal thin film and the running performance becomes worse.

Alternatively, in addition to the above-mentioned lubricant and extreme pressure agent, a rust preventive agent may be used in combination as necessary.

In general, ferromagnetic metal thin films are easily rusted because they are formed of metal materials, and the use of the above-mentioned rust preventive agent greatly improves the corrosion resistance. Therefore, in combination with the lubricating effect of the top coat layer containing the thiophosphite and the fluorine-based lubricant, the durability of the magnetic recording medium can be improved.

Usable rust inhibitors include any that are normally used as rust inhibitors for this type of magnetic recording media, such as phenols, naphthols, quinones, diaryl ketones, and nitrogen. Examples include a heterocyclic compound containing an atom, a heterocyclic compound containing an oxygen atom, a heterocyclic compound containing a sulfur atom, a compound having a mercapto group, a thiocarboxylic acid or a salt thereof, a thiazole compound, and the like.

The above-mentioned rust preventive agent may be used in combination with the above-mentioned lubricant,
For example, the above-mentioned rust preventive agent is first applied to the surface of the ferromagnetic metal thin film, and then a lubricant containing the above-mentioned thiophosphite and fluorine-based lubricant is applied. Then it is highly effective.

When coating in two layers in this way, the amount of the rust preventive applied is 0.5 mg/m as with the previous lubricant.
Preferably “~100mg/a” % 1 m
It is more preferable that the coating amount is between 20a+g/m' and 20a+g/m'. If the coating amount is too small, the effect of improving corrosion resistance will be insufficient, and if it is too large, problems such as runnability will occur.

The magnetic recording medium to which the present invention is applied is one in which a ferromagnetic metal thin film is provided as a magnetic layer on a non-magnetic support, and the material for the non-magnetic support may include polyesters such as polyethylene terephthalate, Polyolefins such as polyethylene and polypropylene, cellulose derivatives such as cellulose triacetate, cellulose diacetate, and cellulose acetate butyrate, vinyl resins such as polyvinyl chloride and polyvinylidene chloride, plastics such as polycarbonate, polyimide, and polyamideimide, aluminum alloys, Examples include light metals such as titanium alloys and ceramics such as alumina glass.

The forms of this non-magnetic support include film, sheet,
It may be a disk, card, drum, etc.

The surface roughness of the non-magnetic support may be controlled by forming one or more types of protrusions such as mountain protrusions, wrinkle-like protrusions, and granular protrusions on the surface of the non-magnetic support.

For example, when forming a polymer film, the above-mentioned Yamabushi projections have a particle size of 5.
It is formed by internally adding inorganic fine particles of about 00 to 3000A, and the height from the surface of the polymer film is 100A.
~1000 people, density approximately 1 x 104 ~ 1° x 104
pieces/Iarn''.The inorganic fine particles used to form the Yamabushi projections include calcium carbonate (CaCO
S), silica, alumina, etc. are suitable.

The wrinkle-like projections are undulations formed by, for example, applying and drying a dilute solution of resin using a specific mixed solvent, and the height thereof is 0.01 to 10 μm, preferably 0.
．． 03~0.58m1 The shortest distance between protrusions is 0.1~20
Let it be μm. Examples of resins used to form these wrinkle-like projections include saturated polyesters such as polyethylene terephthalate and polyethylene naphthalate, polyamides, polystyrene, polycarbonates, polyacrylates, polysulfones, polyethersulfones, polyvinyl chloride, polyvinylidene chloride, and polyvinyl butyral. A single substance, a mixture, or a copolymer of various resins such as polyphenylene oxide, phenoxy resin, etc., and those having a soluble solvent are suitable. Then, to a solution in which these resins are dissolved in a good solvent with a resin concentration of 1 to 1000 ppa+, a solvent that is a poor solvent for the resin and has a higher boiling point than the previous good solvent is added at a concentration of 10 to 100 ppa+ for the resin. By applying twice the amount of the solution on the surface of the polymer film and drying it,
Thin layers with very fine wrinkle-like irregularities can be obtained.

The granular protrusions are formed by attaching organic ultrafine particles such as acrylic resin or inorganic fine particles such as silica or metal powder in a spherical or semispherical shape. The height of this granular protrusion is
50~500A, density is 1X10"~50X10" pieces/
am” or so.

The surface properties of the ferromagnetic metal thin film that is the magnetic layer can be controlled by forming at least one type of these protrusions, but the effect is enhanced by combining two or more types. By forming the protrusions and the protrusions, durability and running properties are greatly improved.

In this case, the overall height of the protrusion is 100 to 200
Preferably, the density is in the range of OA, and the density is l am
It is preferable that the average number per unit is I x 10' to I x 10'.

Further, the ferromagnetic metal thin film that is the magnetic layer is formed as a continuous film by a vacuum thin film forming technique such as a vacuum evaporation method, an ion blating method, or a sputtering method.

In the vacuum evaporation method described above, a ferromagnetic metal material is evaporated by resistance heating, high frequency heating, electron beam heating, etc. under a vacuum of 10-4 to 10'' Torr, and the evaporated metal (
Generally, in order to obtain a high coercive force, an oblique evaporation method is employed in which the ferromagnetic metal material is deposited obliquely to the substrate. or,
A method of performing vapor deposition in an oxygen atmosphere has also been proposed in order to obtain higher coercive force.

Ion blating method is also a type of vacuum evaporation method, and 1
DC in an inert gas atmosphere of O-4 to 1O-3 Torr
This method generates glow discharge or RF glow discharge and evaporates the ferromagnetic metal material during the discharge.

The above sputtering method uses 10"3 to 1G-'Torr.
This is a method in which glow discharge is caused in an atmosphere mainly composed of argon gas, and the generated argon gas ions are used to knock out atoms on the surface of the target film. Alternatively, there is a magnetron sputtering method using magnetron discharge. When using this sputtering method, Cr and W
A base film such as SV may be formed in advance.

In any of the above-mentioned methods, Bi, Sb, Pb, 5nSGa, and In are formed on the substrate in advance.

By pre-depositing a base metal layer such as Cd, Ge, 5tST/etc., and forming the film from a direction perpendicular to the substrate surface, a magnetic layer with excellent in-plane orientation without magnetic anisotropy orientation can be created. It is suitable for forming a magnetic disk, for example.

When forming a metal magnetic thin film using such vacuum thin film forming technology, the ferromagnetic metal materials used include Fe,
In addition to metals such as Co and Ni, Co-Ni alloy, Co-P
t alloy, Co-N1-Pt alloy, Fe-C0 alloy, F
e-Ni alloy, Fe-Co-Ni alloy, Fe-Co
-B alloy, Co -N i -F e -B alloy, Co
Examples include -Cr alloys or those containing metals such as (:, f, AI, etc.).In particular, when a Co-Cr alloy is used, a perpendicular magnetization film is formed.

The thickness of the magnetic layer formed by such a method is 0.
It is about 0.04 to 1 μm.

Furthermore, a so-called back coat layer may be formed on the side of the nonmagnetic support opposite to the side on which the magnetic layer is provided. The back coat layer consists of binder resin such as vinyl chloride-vinyl acetate, phenol resin or polyvinyl fluoride, polyurethane resin or butadiene copolymer, and carbon-based fine powder for imparting conductivity, or surface roughness control and It is formed by coating the surface of a non-magnetic support with a back coat paint in which a powder component such as an inorganic pigment added to improve durability is mixed and dispersed in an organic solvent such as acetone, methyl ethyl ketone or benzene.

A lubricant may be used in the aforementioned backcoat layer. In this case, there is a method of internally adding a lubricant to the back coat layer, or a method of depositing a lubricant on the back coat layer. In any case, the above-mentioned lubricants include fatty acids,
Conventionally known lubricants such as fatty acid esters, fatty acid amides, metal soaps, fatty alcohols, paraffins, and silicones can be used.

[For production]

According to the present invention, in the protective film constituting the magnetic recording medium,
By containing the thiophosphite and the fluorine-based lubricant, good adhesion to the ferromagnetic metal thin film is obtained, and the coefficient of friction is reduced, resulting in a high lubrication effect. Moreover, such adhesion and lubricating effects can be obtained under conditions of high temperature and humidity as well as under conditions of low temperature as under normal conditions.

〔Example〕

Hereinafter, specific examples of the present invention will be described, but the present invention is not limited to these examples.

First, a thiophosphite was synthesized according to the following synthesis example.

Tetradecyl mercaptan corresponding to Synthesis Example was dissolved in petroleum ether together with an equivalent amount of pyridine, and 1/3 equivalent of phosphorus trichloride was added dropwise over 30 minutes. After thoroughly washing the reaction product with water, it was recrystallized from petroleum ether to synthesize trimyristylthiophosphite.

According to the above synthesis method, six types of compounds were synthesized by changing the type of mercaptan.

Example 1 Co was deposited on a polyethylene terephthalate film with a thickness of 4 μm by an oblique evaporation method to form a ferromagnetic metal thin film with a thickness of 1000 Å.

Next, on the surface of this ferromagnetic metal thin film, the thiolite, phosphate ester and fluorine-based lubricant synthesized in the previous synthesis example were applied in an amount of 5 mg/m'', and the film was cut into 81 mm width. The type of thiophosphite and the name of the fluorine-based lubricant used in each example are shown in Table 1 as Examples 1 to 8.

Table 1 For each sample tape created, the relative humidity (RH) was 30% at a temperature of 40°C, and the relative humidity (RH) at a temperature of 25°C.
The dynamic friction coefficient and shuttle durability were measured under the following conditions: RH) was 50% and the temperature was 15°C. This dynamic friction coefficient was tested by using a guide pin made of stainless steel (SUS 304) and feeding it at a speed of 516 ml/sec with a constant tension applied. In addition, the shuttle durability was evaluated by running the shuttle for 2 minutes each time, and determining the number of shuttle runs until the output decreased by 13 dB. Still durability was evaluated by evaluating the decay time for the output to -3 dB in paused deafness.

The results are shown in Table 2. As Comparative Example 1, a blank tape without any top coat was also measured.

As is clear from Table 2, each of the examples of the present invention has a small coefficient of dynamic friction under the conditions of room temperature, low temperature, and high temperature and high humidity.
The running was extremely stable, and no damage was observed on the tape surface even after running back and forth 100 times. Furthermore, the durability was extremely good, and even after 150 shuttle runs, no decrease in output by 13 dB was observed. On the other hand, with the tape of Comparative Example 1 without a lubricant layer, the friction coefficient increased as the number of reciprocating runs increased, running was unstable, tape wear was observed, and durability was poor. .

〔Effect of the invention〕

As is clear from the above description, in the present invention,
A top coat layer containing thiophosphite and fluorine-based lubricant is formed on the ferromagnetic metal thin film type magnetic recording medium, so the coefficient of dynamic friction can be reduced under any temperature conditions, resulting in stable running. A magnetic recording medium with excellent properties and wear resistance can be obtained.

Claims (1)

[Claims] A magnetic recording medium comprising: a ferromagnetic metal thin film formed on a nonmagnetic support; and a top coat layer containing a thiophosphite and a fluorine-based lubricant formed on the ferromagnetic metal thin film.