JPS62236118A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve the traveling property, wear resistance, and durability of the titled medium by forming a topcoat layer consisting of the perfluoroalkyl ester of a carboxylic acid and perfluoropolyether on a ferromagnetic metallic thin film as the magnetic layer. CONSTITUTION:The topcoat layer consisting of the perfluoroalkyl ester of a carboxylic acid and perfluoropolyether is formed on the ferromagnetic metallic thin film-type magnetic recording medium as a lubricant layer. Accordingly, the coefficient of dynamic friction can be reduced under any temp. conditions, and a magnetic recording medium having excellent traveling stability and wear resistance can be obtained. Since the perfluoroalkyl ester of a carboxylic acid has a low solidifying point, the effect is especially enhanced when the medium is used at low temp.

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 in which a ferromagnetic metal Filli is formed as a magnetic layer on a ferromagnetic metal filli, a carboxylic acid perfluoroalkyl ester and a perfluoropolyether are formed on the magnetic layer. Forms a top coat layer that provides excellent runnability under all conditions of use.

The objective is to provide a magnetic recording medium that exhibits wear resistance and durability.

[Conventional technology]

Conventionally, as a magnetic recording medium, r
"" T-F containing F 13 * Os * CO
eso.

Fe5oar r F containing Fe, O,, Co
e Bertolide compound of @02 and Fe5Oa, Co
A powder magnetic material such as a ferromagnetic powder such as a ferromagnetic oxide powder such as a beltlide compound containing Coated magnetic recording media, which are manufactured by coating and drying a magnetic paint dispersed in an organic binder such as a resin, are widely used.

On the other hand, with the increasing demand for high-density magnetic recording, ferromagnetic metal materials such as Co-Ni alloys have been made into polyester by plating or vacuum thin film formation technology (vacuum evaporation, sputtering, ion blating, etc.). A so-called ferromagnetic metal thin film type magnetic recording medium, which is directly deposited on a non-magnetic support such as a film or a polyimide film, has been proposed and is 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 during this time, it must run smoothly and stably. It is better to minimize wear and damage caused by contact with the 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 fill 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 wetting effect. required to do so.

In addition, 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 O to -5℃, so it is difficult to fully demonstrate their lubricating effect. I couldn't do that.

Therefore, the present invention improves running performance by forming a top coat layer on a ferromagnetic metal thin film, which is made of a lubricant that maintains adhesion and lubricity under any usage conditions and maintains a lubricating effect over a long period of time. 5. The purpose of the present invention is to provide a magnetic recording medium with excellent durability.

[Means for solving problems]

As a result of intensive research, the present inventors have discovered that a lubricant containing perfluoropolyether added to carboxylic acid perfluoroalkyl ester, which is an ester of aliphatic carboxylic acid and perfluoroalcohol, has been developed to achieve the above-mentioned purpose. The present invention has been completed by discovering that a good lubricating effect is exhibited over a temperature range, and in which a ferromagnetic metal thin film is formed on a non-magnetic support, and a carboxylic acid is coated on the ferromagnetic metal thin film. It is characterized in that a top coat layer made of acid perfluoroalkyl ester and perfluoropolyether is formed.

The carboxylic acid perfluoroalkyl ester used as a lubricant in the present invention has the general formula % (1) (However, in the above general formula, m≦2n+1゜j≧0.
1≧4. ) is a compound represented by Here, the alkyl group (-C, H,) of the carboxylic acid may be either a straight chain or a soft monomer, and may also contain a double bond.

On the other hand, perfluoroalkyl group (-CbF ah-+)
The number of carbon atoms is preferably 4 or more, and more preferably 6 or more.

The carboxylic acid perfluoroalkyl ester is easily synthesized by, for example, the reaction of the corresponding acid chloride and a fluorine-containing alcohol, and the reaction formula is as follows.

Cl1HaCOCj! + ChF*h1 (CHz)
jOi1 base CnH-Coo(Clh) jc*hk, +...(1
) Formula The above acid chloride can be easily synthesized by chlorinating a commercially available aliphatic carboxylic acid with phosphorus pentachloride pct or 1 g of thionyl chloride SOC. In particular, for aliphatic carboxylic acids with small carbon number n, thionyl chloride S
The 0 reaction formula that can be synthesized by chlorination with OCl t is as follows.

pct.

Cl111. C00II -C,H,C0Cjl...
-For formula (2) fluorine-containing alcohol CkF□-+(CHt)JOH, perfluorocarboxylic acid obtained by the Simmons method etc. is chlorinated in the presence of dimethylformamide (DMF), and then reduced with a reducing agent. The reaction formula that can be easily synthesized is as follows.

5 oct.

DMF...Formula (3) On the other hand, the above perfluoropolyethers have the general formula % formula% or the general formula CFffi→0CJa)r→0CFt h-OCF3.
... ([[[] Polyethers and these polyethers have hydroxyl groups, carboxyl groups, and phosphoric acid groups at the molecular ends.

Examples include those into which polar groups such as sulfonic acid groups, salts thereof, and ester groups have been introduced, and have excellent lubricity and oxidation resistance. In addition, x in the above general formula,
y, q, and r are integers preferably in the range of 40 to 500.

By using the above perfluoropolyether, it is possible to cope with more severe usage conditions and maintain a lubricating effect.

The above-mentioned carboxylic acid perfluoroalkyl esters and perfluoropolyethers may be used in combination with conventionally known lubricants to further expand the usable temperature range.

The lubricants used include fatty acids or their metal salts;
Fatty acid amide, fatty acid ester, fatty alcohol or its alkoxide, fatty amine, polyhydric alcohol,
Sorbitan ester, manniratan ester, sulfurized fatty acid, aliphatic mercapcun, modified silicone oil, perfluoroalkyl ethylene oxide, perfluoropolyethers, higher alkyl sulfonic acid or its metal salt, perfluoro alkyl sulfonic acid or its ammonium salt, or its Examples include metal salts, perfluoroalkylcarboxylic acids or metal salts thereof, and perfluoroalkylcarboxylic acid esters.

In particular, perfluoroalkylcarboxylic acid esters represented by the general formula C1F, COOR (where n represents an integer of 6 to 10, and R represents a hydrocarbon group having 1 to 25 carbon atoms) are also used. Since it has good low-temperature properties, it is suitable for use in combination with the above carboxylic acid perfluoroalkyl ester.

Furthermore, in order to cope with more severe usage conditions and maintain a lubricating effect, the above carboxylic acid perfluoroalkyl ester is added! I amount ratio: 30 Near 0~To: 30
An extreme pressure agent may be used in combination at a certain mixing ratio.

When the extreme pressure agent makes partial metal contact in the boundary lubrication area, it reacts with the metal surface due to the accompanying frictional heat, forming a reaction product film to prevent friction and wear. In particular, phosphorus-based extreme pressure agents such as phosphate esters, phosphite esters or phosphate ester amine salts, sulfur-based extreme pressure agents such as sulfurized oils and fats, monosulfides or polysulfides, iodine compounds, bromine compounds or chlorine compounds, etc. Halogenated extreme pressure agents, organometallic extreme pressure agents such as thiophosphates, thiocarbamates, or metal alkyl dithiocarbamates, and complex extreme pressure agents such as dialkylthiophosphate amines, thiophosphates, or thiophosphites are well known. It is being

Moreover, in addition to the above-mentioned lubricants and extreme pressure agents, a rust preventive agent may be used in combination as required.

As the rust preventive agent that can be used, any rust preventive agent that is normally used as a rust preventive agent for this type of magnetic recording medium may be used, such as dihydric phenol.

Phenols such as alkylphenols or nitrosophenols, pure naphthols or naphthols such as nitro-, nitroocta-amino, and halogeno-substituted naphthols, methylquinone, hydroxyquinone.

Quinones such as aminoquinone, nitroquinone or halogen quinone, benzophenone and its derivatives hydroxybenzophenone, diarylketones such as aminobenzophenone, acridine, 4-quinolitool, heterocyclic compounds containing nitrogen atoms such as kynurenic acid or riboflavin, tocopherol or guanosine, etc. heterocyclic compounds containing an oxygen atom, heterocyclic compounds containing a sulfur atom such as sulfolane, sulfolene, or bithione, compounds having a mercapto group such as thiophenol, dithizone, or thiooxin, thiocarboxylic acids such as entathioic acid or rubeanic acid, or salts thereof , diazosulfide, benzothiazoline, and other thiazole compounds. The above-mentioned rust preventive agent may be used in combination with a lubricant, but for example, the above-mentioned rust preventive agent is first applied to the surface of a ferromagnetic metal thin film, and then a lubricant is applied thereon. It is more effective if applied separately.

A method for depositing a lubricant layer containing these carboxylic acid perfluoroalkyl esters and perfluoropolyethers on a ferromagnetic metal thin film is to dissolve the above lubricant in a solvent and add the resulting solution to the ferromagnetic metal TiJH. It can be applied or sprayed onto the surface, or conversely, a ferromagnetic metal thin film can be immersed in this solution and dried.

Here, the coating amount is 0.5■/d to 100■/IT
preferably from 1 mg/rd to 20 w/
rd 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 sliding member and the ferromagnetic metal thin film will be damaged. A sticking phenomenon occurs between the wheels, which actually worsens the running performance.

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, polycarbonate
Examples include plastics such as polyimide and polyamideimide, light metals such as aluminum alloys and 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-like protrusions or wrinkle-like protrusions on the surface of the non-magnetic support.

For example, the above-mentioned mountain-like protrusions have a particle size of 5 when forming a polymer film.
It is formed by internally adding inorganic fine particles of about 0.00 to 3000, and the height from the polymer film surface is 100 to 3000.
1000 people, density approximately 1XlO' to 1OX10'/2 cranes. As the inorganic fine particles used to form the mountain-like projections, calcium carbonate (CaCO,), silica, alumina, etc. are suitable.

The wrinkle-like protrusions 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.
．． 03~0.5μm, the shortest distance between protrusions is 011~20
The length shall be 8m. 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, a solvent that is a poor solvent for the resin and has a boiling point higher than the good solvent is added in an amount of 10 to 100 times the amount of the resin to a solution in which these resins are dissolved in the good solvent and the resin concentration is 1 to 11,000 pp. By applying this solution to the surface of a polymer film and drying it, a thin layer having 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 to 500 people, density 1×10b to 50XlO− pieces/
-1 is the degree.

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 within the range of 0 people, the density is 1 dragon 2
The average hit is I x 10' to 1 x 10? It is preferable that the number of

Further, the ferromagnetic metal thin film which is the above-mentioned magnetic layer can be formed using a vacuum deposition method, an ion blating method, a sputtering method, or the like. Formed as a continuous film using a forming technique.

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-' 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,
It also includes those in which the above-mentioned vapor deposition is performed in an oxygen atmosphere in order to obtain higher coercive force.

The above ion blating method is also a type of vacuum evaporation method, in which DC glow discharge and RF glow discharge are caused in an inert gas atmosphere of 10-4 to 1 O-' Torr, and the above @magnetic metal material is deposited during the discharge. It is evaporated.

The above sputtering method involves causing glow discharge in an atmosphere mainly composed of argon gas at 104 to 10 Torr, and using the generated argon gas ions to knock out atoms on the target surface. -tlt 2-pole or 3-pole sputtering method, high frequency sputtering method, magnetron sputtering method using magnetron discharge, etc.

In the case of this sputtering method, Cr or W is used.

A base film such as V may be formed in advance.

In any of the above methods, Bi, Sb, Pb, Sn, Ga, and In are preliminarily deposited on the substrate.

By pre-depositing a base metal layer such as Cd, Ge, Si, TI, etc., and depositing the film in a direction perpendicular to the substrate surface, excellent magnetic properties can be achieved in an in-plane manner without magnetic anisotropy orientation. It is suitable for forming a layer, for example, into a magnetic disk.

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, C0-Ni alloy, Co-P
t alloy, Co-N1-Pt alloy, Fe-Co alloy, Fe
Examples include -Ni alloy, Fe-Co-Ni alloy, Fe-Co-B alloy, CoN1-Fe-B alloy, Co-Cr alloy, and those containing metals such as Cr and A1. In particular, when a Co--Cr alloy is used, a perpendicularly magnetized 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, carbon-based fine powder for imparting conductivity, or surface roughness control. The above-mentioned backing is formed by applying a bank coating paint on the surface of a non-magnetic support, 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 coating layer. In this case, there are two methods: adding the lubricant internally into the back coat layer, or depositing the lubricant on the back coat layer. In any case, as the lubricant, conventionally known lubricants such as fatty acids, fatty acid esters, fatty acid amides, metal soaps, aliphatic alcohols, paraffins, and silicones can be used.

[Effect]

The lubricant layer made of carboxylic acid perfluoroalkyl ester and perfluoropolyether is made of ferromagnetic metal Fl.
By forming a top coat layer on the film, it exhibits a good lubricating effect and is J1! Reduce friction coefficient. In particular, carboxylic acid perfluoroalkyl esters exhibit good lubricating effects even at low temperatures.

〔Example〕

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

First, a carboxylic acid perfluoroalkyl ester was synthesized according to the following synthesis example.

Synthesis example Commercially available oleic acid, linoleic acid, lylunic acid.

Myristic acid and palmitic acid are each converted into phosphorus pentachloride (P).
CIs) or thionyl chloride (SOClg) to give the corresponding carboxylic acid chloride. Note that a commercially available butanoyl chloride was used.

On the other hand, after chlorinating pentadecafluorooctanoic acid or nonadecafluorodecanoic acid with thionyl chloride (SOCh) using dimethylformamide (DMF) as a catalyst,
Pentadecafluoro-1-octatool and nonadecafluoro-1-decanol were synthesized by reduction with lithium aluminum hydride.

Next, the above pentadecafluoro-1-octatool or nonadecafluoro-1-decanol was dissolved in chloroform together with triethylamine, and any one of the carboxylic acid chlorides synthesized earlier was added dropwise over 30 minutes under water cooling. After the addition was completed, the mixture was stirred at room temperature overnight. This was washed with water, 5% diluted hydrochloric acid, an aqueous NaHCOx solution, and water in this order, and then purified by vacuum distillation.

According to the above synthesis method, eight types of compounds were synthesized by changing the type of carboxylic acid chloride.

Confirmation of the product was performed using infrared spectroscopy (IR) and mass spectrometry (
For example, in the case of oleic acid pentadecafluorooctyl ester, 1360-1
100c+m-' absorption peculiar to CF bond is observed, ester C=0 absorption is observed at l760cm-', 3020c111-' and 2930c
Absorption due to stretching vibration of CH is observed in m+-',
Confirmed from etc. Also'! The presence of a molecular ion peak M° of 664 in the mass spectrum obtained by tl1 analysis also supports this structure. In addition, the above MW analysis is
Manufactured by JEOL.

The measurement was performed using a mass spectrometer DX303, and the measurement was performed after confirming that it was a single component using a gas chromatograph.

Table 1 shows the compounds synthesized in Synthesis Examples.

(Margin below) Table 1 Example 1 A 14 μm thick polyethylene terephthalate film was coated with Co by an oblique vapor deposition method, and a film was formed! 1000 people formed a ferromagnetic metal thin film.

Next, 0.48 g of carboxylic acid perfluoroalkyl ester (oleic acid pentafluorooctyl ester of compound 1 shown in Table 1) was placed on the surface of this ferromagnetic metal Ti film.
was dissolved in 800 g of Freon, and a 1:l amount of perfluoropolyether (trade name: Fonprin, manufactured by Montegisson) represented by the formula %() (in the formula, Xnia-40:l) t added in proportion
A sample tape was prepared by applying 8 liquids and cutting it into 8 strips.

Examples 2 to 8 Sample tapes were prepared in the same manner as in Example 1 except that Compounds 2 to 8 were used in place of Compound 1.

Example 9 A carboxylic acid perfluoroalkyl ester (compound 9 shown in Table 1) and a perfluoropolyether (trade name Fomblin, manufactured by Montegisson) were used, and both were added at a ratio of 2:1, and the other procedures were carried out. A sample tape was prepared in the same manner as in Example 1.

Example 10 A sample tape was prepared in the same manner as in Example 9 except that Compound 10 was used instead of Compound 9.

Example 11 Using carboxylic acid perfluoroalkyl ester (compound 11 shown in Table 1) and perfluoropolyether (trade name: Fonprin, manufactured by Montegisson), both were mixed in a ratio of 3:1.
A sample tape was prepared in the same manner as in Example 1, except that the sample tape was added at a ratio of .

Example 12 Compound 12 was used instead of compound 11, and the other conditions were as in Example 1.
A sample tape was prepared in the same manner as in Example 1.

Example 13 Using carboxylic acid perfluoroalkyl ester (compound 13 shown in Table 1) and perfluoropolyether (trade name: Fonprin, manufactured by Montegisson), both were mixed in l:2.
A sample tape was prepared in the same manner as in Example 1, except that the sample tape was added at a ratio of .

Example 14 Compound 14 was used instead of compound 13, and the other conditions were as in Example 1.
A sample tape was prepared in the same manner as in 3.

Example 15 Using carboxylic acid perfluoroalkyl ester (compound 15 shown in Table 1) and perfluoroboriether (trade name Fomblin, manufactured by Montegisson), both were mixed in l:3.
A sample tape was prepared in the same manner as in Example 1, except that the sample tape was added at a ratio of .

For each of the sample tapes produced, the dynamic friction coefficient and shuttle durability were measured under conditions of a temperature of 25°C, a relative humidity (RH) of 50%, and -5°C. This dynamic S friction coefficient was tested by using a guide pin made of stainless steel (SU3304) and feeding it at a speed of 5-■/see under a constant tension. In addition, the shuttle durability was determined by running the shuttle for 2 minutes each time, and the output was 13 times.
The evaluation was based on the number of shuttles until the dB decrease. Still durability was evaluated by evaluating the decay time for the output to -3 dB in a pause state. The results are shown in Table 2 (1) and Table 2 (2).
(Margins below) Table 2 (1) Table 2 (2) As is clear from this table, each example of the present invention has a small dynamic friction coefficient under both room temperature and low temperature conditions, and the running is extremely stable. Moreover, even after running back and forth 100 times, no damage was observed on the tape surface.

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 the comparative example without a lubricant layer, the coefficient of friction increases as the number of reciprocating runs increases, the running is unstable, tape wear is observed, and durability is poor.

[Effects of the Invention] As is clear from the above explanation, in the present invention,
Ferromagnetic gold I! Since a top coat layer made of carboxylic acid perfluoroalkyl ester and perfluoropolyether is formed as a lubricant layer on a thin film type magnetic recording medium, the coefficient of dynamic friction can be reduced under any temperature conditions. A magnetic recording medium with excellent running stability and wear resistance can be obtained.

In particular, since the freezing point temperature of carboxylic acid perfluoroalkyl ester is low, it is highly effective when used at low temperatures.

Claims (1)

[Claims] A magnetic recording medium comprising: a ferromagnetic metal thin film formed on a nonmagnetic support; and a top coat layer made of carboxylic acid perfluoroalkyl ester and perfluoropolyether formed on the ferromagnetic metal thin film.