JPH0447519A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain the metallic thin-film type magnetic recording medium which is less deteriorated in traveling property and wear resistance even after long-term use by providing an intermediate layer contg. a lubricant between a nonmagnetic base and a magnetic layer. CONSTITUTION:This recording medium has the intermediate layer contg. the lubricant between the nonmagnetic base and the magnetic layer consisting of a ferromagnetic metallic thin film. The lubricant is exemplified by a monovalent or polyvalent higher fatty acid having a satd. or unsatd. straight chain or branched structure, or the ester compd. thereof, compds. having fluorinated polymer chains on the surface of the magnetic layer, for example, compds. having a fluorinated alkyl group, fluorinated alkenyl group, fluorinated polyesther group, etc. The always stable and gradual supply of the lubricant to the surface of the magnetic layer from the intermediate layer through the magnetic layer is possible in this way and the magnetic recording medium having the traveling property, durability and wear resistance excellent over a long period of time under a wide range of environment is obtd.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a so-called metal full type magnetic recording medium comprising a ferromagnetic metal thin film as a magnetic layer, and particularly to a magnetic recording medium that can be used for a long time under a wide range of temperature and humidity conditions. The present invention also relates to a magnetic recording medium with extremely little deterioration in running performance.

[Conventional technology and its problems]

Conventionally, as magnetic recording media, so-called coated magnetic recording media have been widely used, in which a coating liquid in which ferromagnetic powder is dispersed in an organic binder is coated on a non-magnetic support and dried.

However, recently, due to the demand for high-density recording, vacuum deposition,
So-called metal thin film magnetic recording media, in which the magnetic layer is a ferromagnetic metal thin film formed by a paper deposition method such as sputtering or ion blasting, or a plating method such as an electroplating method or an electroless plating method, have been attracting attention. Some parts have been put into practical use.

In particular, the method using vacuum evaporation has great advantages as it has a simpler manufacturing process and can increase the deposition rate of the film compared to plating, which requires waste liquid treatment. As a method of imparting sex, US Patent Nos. 3,342,632 and 3,342
The oblique vapor deposition method described in No. 633 and the like is known. The structure of the magnetic layer of the metal thin film formed by this oblique evaporation method is formed of an aggregate of obliquely inclined columnar crystals on a nonmagnetic support.

While metal thin film magnetic recording media have extremely superior magnetic properties compared to coated magnetic recording media, there are major practical problems due to the fact that the magnetic layer is made of a thin metal film, such as weather resistance and runnability. , wear resistant.

That is, during 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 at this time, the traveling must be smooth and stable, and at the same time, the movement with the head must be smooth and stable. Contact, abrasion, or destruction must not occur, but in the case of metal thin film magnetic recording media, these requirements are not always fully met, and in fact, due to the background of 0 or more, which has become an obstacle in practical use. In order to improve running properties and durability, it has been considered to provide a lubricating layer or a protective layer on the surface of the magnetic layer of a metal thin film magnetic recording medium.

As protective layers for metal thin film magnetic recording media, there are those coated with thermoplastic resins, thermosetting resins, fatty acids, metal salts of fatty acids, fatty acid esters, alkyl phosphate esters, etc. dissolved in organic solvents (for example, Unexamined Japanese Patent Publication 1986-69
(See Japanese Patent Application Laid-open No. 824 and Japanese Patent Application Laid-open No. 85427/1983).

In addition, fluorine-containing ester compounds (for example, JP-A No. 6
2-236118), perfluoropolyether (hereinafter referred to as PFPE)) (USP 377830B), PFPE with terminal inorganic elements such as carboxylic acid groups and alkoxycarbonyl groups (US 384797 B), or the above two types. PFPE is used in combination (Unexamined Japanese Patent Publication No. 1986-
113126) and other technologies have been developed. Furthermore, as a method of forming a strong protective film with lubricating properties, a method of applying a silane coupling agent containing a fluorine atom to the surface has been used (for example, Japanese Patent Application Laid-Open No. 63-220420).

However, even in metal thin film magnetic recording media obtained by devising various lubricants,
When used for long periods in extreme environmental conditions such as low humidity, there are problems such as reduced running performance and reduced wear resistance, so improvements are still desired for metal thin film magnetic recording media. There is.

In other words, since the magnetic layer of metal thin film magnetic recording media is extremely thin and there are few voids in the magnetic layer, the magnetic layer cannot hold a sufficient amount of lubricant, so the lubricant may run out during use. As a result, the coefficient of friction increased.

It has also been proposed to provide a protective layer of resin containing a lubricant on the magnetic layer, but this is not preferred because it increases spacing loss with the head and reduces output.

[Problem that the invention seeks to solve]

The present invention has been made in view of the problems of the prior art, and it is an object of the present invention to provide a thin metal film type magnetic recording medium that exhibits little deterioration in running performance and wear resistance even after long-term use.

[Means for solving problems]

The present invention is a magnetic recording medium having a magnetic layer made of a ferromagnetic metal thin film on a non-magnetic support, characterized by having an intermediate layer containing a lubricant between the non-magnetic support and the magnetic layer. This is a magnetic recording medium that can solve the above problems and achieve the objectives.

In general, in metal thin film magnetic recording media, unlike coated magnetic recording media in which lubricant is stored inside the magnetic layer, lubricant is contained and stored inside the magnetic layer because the magnetic layer is extremely thin and has no air gaps. It is difficult because there are few structures.

For this reason, even if lubricant is present only on the surface of the magnetic layer as in the past, when the head is repeatedly rubbed against the head or when the running member repeatedly rubs against each other, the lubricant disappears from the surface of the magnetic layer, and the lubricant disappears downward. Without replenishment, the lubricating effect will be permanently lost.

In the present invention, an intermediate layer containing a lubricant is provided below a magnetic layer made of a thin metal film (hereinafter simply referred to as the magnetic layer), thereby producing a replenishing effect against the loss of the lubricant as described above. In other words, a metal thin film is macroscopically a continuous film, but microscopically it has a fine columnar crystal or fine grain structure.
In general, organic lubricants with low surface tension pass through the gaps in this microstructure from the intermediate layer of the present invention by the effect of capillary action, and gradually seep out onto the surface of the magnetic layer, improving runnability, durability, and wear resistance. Abrasion resistance can be improved. The above hypothesis is also supported by the fact that lubricants with particularly low surface tension are materials that are particularly likely to exhibit the effects of the present invention.

The means for forming the magnetic layer and its shape and structure in the present invention are not particularly limited.

Examples of means for forming the magnetic layer include electroplating, electroless plating, vapor phase plating, sputtering, vapor deposition, and ion blating.

Further, examples of the crystal structure of the magnetic layer include hexagonal crystal, orthorhombic columnar crystal, and the like.

In order to more effectively achieve the object of the present invention, an oblique evaporation method is preferable as a means for forming the magnetic layer, and a magnetic layer made of orthorhombic columnar crystals formed by this method is preferable. is preferable because it is an effective structure because the lubricant oozes out from the intermediate layer to the surface of the magnetic layer through the gap as described above.

Specifically speaking, the orthorhombic columnar crystals include those in which crystal columns are arranged diagonally overlapping each other in a scale-like manner.

The magnetic layer of the present invention may be composed of multiple layers having the same composition and different crystal structures, the same crystal structure but different orientations, and/or multiple layers having different compositions regardless of the crystal structure. When the magnetic layer is composed of two layers having the same composition and crystal structure in which the directions of the orthorhombic columnar crystal structures are crossed in opposite directions, differences in electromagnetic conversion characteristics and durability due to the running direction of the head can be reduced. This is preferable for reducing noise.

In the present invention, the structure of the intermediate layer (hereinafter simply referred to as intermediate layer) provided between the non-magnetic support and the magnetic layer basically stores and retains the lubricant and transfers it to the magnetic layer. There are no particular limitations as long as sustained release is possible.

Specific methods for forming the intermediate layer include the following method.

■ Lubricant as is or with filler particles, e.g.
Porous inorganic materials (metals, metal oxides, metal nitrides, etc.),
Prepare a paint by mixing with a film-forming resin and an organic solvent,
A method of coating this between a non-magnetic support and a magnetic layer to form an intermediate layer.

■ A layer made of a suitable carrier, such as a resin or a porous inorganic material (metal, metal oxide, metal nitride, etc.), is provided between the non-magnetic support and the magnetic layer, and lubrication is applied within or on this layer. A method in which an intermediate layer is formed by coating, impregnating, and adsorbing an agent.

■ A method in which only the lubricant itself is applied as it is or after being diluted with an organic solvent, etc., between the nonmagnetic support and the magnetic layer to form an intermediate layer consisting only of the lubricant.

Among the above methods (1) to (2), method (2) is most preferred, but these methods (1) to (4) may be used in combination.

Between the non-magnetic support and the magnetic layer where the intermediate layer is provided,
In addition to the case literally below the magnetic layer and on the non-magnetic support,
It includes the inside of the magnetic layer except on the surface of the magnetic layer, and one or more intermediate layers can be provided.

Therefore, the term "between the nonmagnetic support and the magnetic layer described in (1) to (1)" above means the surface of the nonmagnetic support or the surface of the magnetic layer provided on the nonmagnetic support, and the magnetic recording medium of the present invention To obtain this, after providing the intermediate layer, a magnetic layer is provided on the surface of the symbiotic interlayer.

The thickness of the intermediate layer is 0.02 to 0.3-2, preferably 0.02 to 0.3-2.
It is in the range of 0.05 to O, lpa, and if it is less than 0.02, it is not preferable because it cannot hold sufficient lubricant.
If it is larger than 0.3, surface roughness of the magnetic layer tends to occur, which is not preferable in terms of maintaining good electromagnetic conversion characteristics.

In addition, the layer thickness of the magnetic layer is 300 to 5000, preferably 500 to 5000, including the case where an intermediate layer is provided inside the magnetic layer.
The range of 3000 people is preferable, and if it is less than 300 people, good magnetic properties cannot be obtained sufficiently, so it is not preferable.
If it is larger than 0,000, it is difficult to sufficiently supply the lubricant from the intermediate layer to the surface of the magnetic layer, which is not preferable.

The lubricants used in the intermediate layer of the present invention include monovalent or polyvalent higher fatty acids having a saturated or unsaturated, linear or branched structure, or their ester compounds, and fluorinated molecular chains on the surface of the magnetic layer. For example, compounds having a fluorinated alkyl group, a fluorinated alkenyl group, a fluorinated polyether group, etc. can be mentioned.

As the fluorinated polyether, it is most preferable to use a fluorinated polyether that is unmodified at both ends or has a group selected from alkoxycarbonyl, acyloxy, and hydroxyl at at least one end, and has a remarkable effect of improving durability.
Particularly preferred are terminally unmodified perfluoropolyethers.

Examples of unmodified fluorinated polyethers include CF2-
0 (CFgO), -(CFtCh,), 1-CF
s to the compound CF, -0(CFt,), -(C
FzCF (CFff) 0), 1-CFff Compound BCFs-0 (CFtCFzCFzO), 1-CF
, Compound CCF+-0 (ChCF(C
Fs)O) and 1-CFx compounds.

Specific examples of alkoxycarbonyl and acyloxy groups in fluorinated polyethers having a group selected from alkoxycarbonyl, acyloxy, and hydroxyl at at least one end include CH,0CO-, C,H3OC0-
1C+JzsOCO-1HCOOlCHsCOO-,C
JsCOO-1C, JxsCOO-1C, H, 0CO-
1ChHsCOO- is mentioned.

Examples of fluorinated polyethers having these groups include the compounds CHiOCOCh-0(CFgO) s-(cFzcF
zO), -CFtCOOCF3 compound HOCF! -0(CFgO) a-(C1hCFχ0)
, -CF,OH compound C++Hz3COOCHzCFz-0(ChO)-(C
hChO)l1CI+HziCOOCHzCh Compound 2CJsOCOCFz-0(Ch,) s-(CFtCh
O) nCF, C00C&H5 compound hoCF3-0(CF,0), -(CF□CFtO)-CF
Ch-0(CFzO)--(CFzChO)--CF to tCOOCFs compound
Examples include tOH and the like. In addition, in the above compound, n and m
represents 5 to 10.

Examples of lubricants that can be contained in the intermediate layer include those with unmodified ends or alkoxycarbonyl, acyloxy,
Fluorinated polyethers having a small number of groups selected from hydroxyl (at both ends) are preferred, but other lubricants that can be mixed or used alone include fatty acids,
Metal soaps, fatty acid amides, fatty acid esters, higher aliphatic alcohols, monoalkyl phosphites, dialkyl phosphites, trialkyl phosphites, monoalkyl phosphates, dialkyl phosphates, trialkyl phosphates, alkanesulfonic acids, their amide compounds, or Salts thereof, paraffins, silicone oils, animal and vegetable oils, mineral oils, higher aliphatic amines; inorganic fine powders such as graphite, silica, molybdenum disulfide, tungsten disulfide; polyethylene, polybutyrene, polyvinyl chloride, ethene-vinyl chloride copolymers , fine resin powders such as polytetrafluoroethylene; chi-olefin polymers; unsaturated aliphatic hydrocarbons and fluorocarbons having a melting point of 40"C or lower, preferably liquid at room temperature.

The lubricant contained in the intermediate layer must be in a liquid state at least when the head is running, or must be able to become liquid due to frictional heat while the head is running, and when used at an environmental temperature in the range of -10 to 60"C. The melting point of the lubricant is 60°C
The temperature is preferably below 40°C. Incidentally, those having a melting point higher than 40°C can be used in the form of being dissolved in a substance having a lower melting point.

Film-forming resins used for forming the intermediate layer in the present invention include vinyl chloride, vinyl resins mainly based on vinyl chloride such as vinyl chloride-vinyl acetate copolymer, cellulose resins such as nitrocellulose, polyester, Condensation resins such as polyurethane can be used, and acrylates,
A curing agent such as isocyanate can be used in combination. The preferred weight average molecular weight range of these resins is 5000
-100,000, preferably 10,000-70,000.

When the intermediate layer contains filler particles, the particles include:
Specifically, those having an average particle size of 100 to 300 particles are preferable, and examples include inorganic particles, with silica being particularly preferable.

When the intermediate layer is composed of a lubricant and a resin (including a curing agent), the amount of the lubricant is preferably 2 to 80% by weight and the amount of the resin is 10 to 98% by weight based on the total weight of the intermediate layer. . In addition, when the intermediate layer contains filler particles, the amount of lubricant present is 2 to 50% by weight, and the amount of resin is 1% by weight based on the total weight of the intermediate layer.
The content of the filler particles is preferably 5 to 90% by weight, and 5 to 50% by weight.

Further, the organic solvent for preparing the intermediate layer forming paint by dissolving the above-mentioned resin or the like, or as a mere diluent for the lubricant, is not particularly limited as long as it can be volatilized along with forming the intermediate layer, and for example, Examples include methyl ethyl ketone, cyclohexanone, trichlorofluoroethane, and the like. Incidentally, if the lubricant itself has sufficient power to dissolve the resin, there is no particular need to use a separate organic solvent.

The outermost surface of the magnetic layer of the present invention is preferably coated with a protective layer consisting of a lubricant, and is usually coated with a lubricant.
It is applied as it is or diluted with the above-mentioned organic solvent or the like at a rate of 30 g/nf, preferably in the range of 3 to 20 Wg/rrf.

The material for the ferromagnetic metal thin film may be iron, cobalt, nickel or other ferromagnetic metals, or Fe-Co, Fe-Ni.
, Co-Ni, Fe-Rh, Co-P,
Co-B, Co-Y.

Co-L, Co-Ce, Co-Pt, Co-
5s, Co-Mn, Co-Cr.

Fe-Co-Ni, Co-N1-P% Co-N1
-BSCo-Ni-Ag, Co-Ni-Nd, Co
-Ni-Ce, Co-Ni-Zn, Co-Ni-C
u.

Examples include ferromagnetic alloys such as Co-N1-W and Co-Ni-Re, and ferromagnetic metal thin films are formed by methods such as electroplating, electroless plating, vapor phase plating, sputtering, vapor deposition, and ion blating. Here are some things that made me feel bad.

When forming a metal thin film, electromagnetic conversion characteristics and durability can be improved by introducing oxygen into the various ferromagnetic metal thin films, for example, by vapor deposition in an oxygen stream. In addition to oxygen, N, Cr, Ga
, As, St, Zr, Nb, Mo, Rh,
Pd.

Sn, Sb, Te, Pg, Re, O
s, rr, Au, Flg, Pb, Bi
etc. may be included.

In the present invention, when the magnetic layer is composed of orthorhombic columnar crystals, the specific method is as follows:
Using an eV electron beam, the vacuum level of the film forming chamber is
Introducing oxygen gas while maintaining the pressure in the film forming chamber at 10-'Torr or less,
An example of this method is to obliquely evaporate a ferromagnetic metal onto a nonmagnetic support placed in a film forming chamber at an incident angle of 0 to 50 degrees.

The surface shape of the above magnetic layer is not particularly defined, but 1 to 5
Especially when it has protrusions with a height of 00 nm, it has excellent runnability and durability.

Further, in order to improve the adhesion of the ferromagnetic metal TRH and improve the magnetic properties, an underlayer may be provided on the nonmagnetic support separately from the intermediate layer.

The base layer can contain the same resin as the resin constituting the intermediate layer and/or the inorganic particles that can be contained in the intermediate layer. That is, the intermediate layer of the present invention from which the lubricant has been removed can be applied to the magnetic recording medium of the present invention.

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, or AI, Ti, stainless steel, etc. used.

The thickness of the nonmagnetic support is preferably 4 to 5011 m.

In order to improve the running durability of the present invention, it is effective to provide minute protrusions on the surface of the non-magnetic support before forming the metal thin film, as this will result in appropriate unevenness on the surface of the magnetic layer. It is true. The density of microprotrusions is 2X10'~
2 x 10' 1 piece/layer set 2, the height of one protrusion is 1~5
Preferably, the thickness is 0 nm.

The shape of the magnetic recording medium may be tape, sheet, card, disk, etc., but particularly preferred are tape,
It is disc-shaped.

In order to further improve the running durability of the magnetic recording medium of the present invention, a back layer made of non-magnetic particles and a binder resin can be provided on the surface opposite to the surface on which the magnetic layer is located.

〔Effect of the invention〕

The present invention provides an intermediate layer containing a lubricant at the bottom of the magnetic layer, thereby eliminating the deterioration in durability and wear resistance caused by the disappearance of the lubricant as in the conventional method. This can be prevented by always stably and gradually supplying the agent, so it is possible to provide a magnetic recording medium that has excellent long-term running properties, durability, and abrasion resistance under a wide range of environments.

〔Example〕

The present invention will be explained in more detail below using Examples. It will be readily understood by those skilled in the art that the ingredients, proportions, order of operations, etc. shown herein may be modified without departing from the spirit of the invention.

Therefore, the present invention should not be limited to the following examples, and parts in the examples and comparative examples indicate parts by weight.

Example 1 Interlayer compositions A-D (where A-C are inventive examples, D
is a comparative example that does not contain a lubricant, details are listed in Table-1H,)
was coated with a bar coater to a dry film thickness of 0.64 to form intermediate layers for samples Nos. 1 to 7 (Sample No. 7 is a comparative example in which the composition was not used). Thereafter, a 30 KeV electron beam was used as an evaporation heating source, the vacuum level of the film formation chamber was set to 5X10-'Torr, oxygen gas was introduced until the film-forming pressure reached 1X10-3 Torr, and the film was placed in the film-forming chamber. On the intermediate layer of the film, a cobalt nickel magnetic layer (layer thickness 150 nm) was obliquely deposited at an incident angle of 50 degrees. Table 2 was printed on the magnetic layer of the obtained magnetic recording medium.
Forming a protective layer by applying the protective layer compositions a to C described above,
After that, samples NQ1 to 7 (Table 3) were cut into 8 mm pieces.
8 mm tapes described in (if) above were manufactured and subjected to the evaluation test described below.

(Evaluation) The coefficient of friction of each sample against a stainless steel rod at 45°C and 70% relative humidity, that is, the μ value (initial μ value and μ value after 500 runs), and repeated running on an 8 mm VTR at 23°C. The durability and still durability were investigated and the results are shown in Table 3.

Here, running durability means running a 5m long tape on an 8mm type VT.
R (Fuji Photo Film ■, FUJIX-8M6 type), this is the number of times the image is played until the screen is disturbed due to unstable running or the running stops due to an increase in the coefficient of friction.

In addition, the still durability was determined by pressing the pause button during image playback with the same type of VTR (but without the function to limit still playback time), and determining whether the image was rJ<tA 'j
”l=r＞Iil'iE'h 1fljLL1tj(
・-S”y.

Table 1: Intermediate layer composition In this way, the intermediate layer between the metal thin film magnetic layer and the non-magnetic support of the present invention has improved μ value, repeated running durability, and still life compared to the conventional lubricant-free type. It is clear that it has excellent durability and that this feature is realized under a wide range of conditions from high temperature and high temperature to low temperature and low humidity.

Claims (5)

[Claims] (1) A magnetic recording medium having a magnetic layer made of a ferromagnetic metal thin film on a non-magnetic support, characterized by having an intermediate layer containing a lubricant between the non-magnetic support and the magnetic layer. magnetic recording medium. (2) The magnetic recording medium according to claim 1, wherein the lubricant has a melting point of 40° C. or lower. (3) The magnetic recording medium according to claim 1 or 2, wherein the lubricant is a fluorine compound. (4) The magnetic recording medium according to any one of claims 1 to 3, wherein a protective layer is formed on the surface of the magnetic layer. (5) Claims 1 to 3, wherein the magnetic layer is made of orthorhombic columnar crystals.
4. The magnetic recording medium according to any one of 4.