JPH0628665A - Magnetic recording medium and its production - Google Patents

Abstract

PURPOSE:To improve a lubricating effect, to enhance traveling durability and to lessen head clogging by forming lubricating layers successively provided with a PFPE layer contg. polar groups and having a specific viscosity and an PFPE layer contg. non magnetic groups on a ferromagnetic metallic thin film. CONSTITUTION:The ferromagnetic metallic thin film 3 is formed on a nonmagnetic base and is subjected to a contact treatment in an environment kept at 50 to 80% relative humidity and 20 deg.C. The ferromagnetic metallic thin film 3 is provided thereon with the lubricating layers 4 successively provided with the perfluoropolyether PFPE 5 contg. the polar groups and having 200 to 1000cst at ordinary temp. and the PFPE 6 contg. no polar groups and having a viscosity of 50cst or lower. As a result, the stable boundary lubricating films are formed at the boundary with the ferromagnetic metallic thin film, by that, the lubricating effect is improved, the traveling durability is enhanced and the head clogging is ameliorated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ferromagnetic metal thin film for high density recording having excellent electromagnetic conversion characteristics, and more particularly to a magnetic recording medium having excellent running durability.

[0002]

2. Description of the Related Art A so-called ferromagnetic metal thin film type magnetic recording medium in which a magnetic layer of a ferromagnetic metal thin film is formed on a non-magnetic support by a vacuum deposition method such as a vacuum deposition method, a sputtering method, an ion plating method, Compared to the coating type magnetic recording medium in which the magnetic layer is mainly composed of ferromagnetic powder and binder resin, it has excellent electromagnetic conversion characteristics because there is no binder resin in the magnetic layer. It has attracted attention as a recording medium and has been partially put into practical use.

In particular, the vacuum vapor deposition method has advantages over other vacuum film forming methods in that it can be processed by a dry process, the film forming rate is relatively high, and the manufacturing process is relatively simple. Regarding the improvement of the ferromagnetic metal thin film type magnetic recording medium by the vacuum deposition method, for example, US Pat. No. 3,342,632 is known.
Various proposals have been made since ancient times, including No. 3342633 and the like.

A major problem in practical use of this ferromagnetic metal thin film type magnetic recording medium is the problem of running property and durability. In the process of recording, reproducing and erasing signals in magnetic recording, the magnetic recording medium and the magnetic head slide against each other at a high speed, but at that time, the magnetic recording medium must not be worn or destroyed. Not only that, but smooth and stable driving is required.

However, it is difficult to secure running durability of the ferromagnetic metal thin film type magnetic recording tape as compared with the coating type magnetic recording tape. This is because the coating type magnetic recording medium has a lubricant in the magnetic layer and therefore can be surface-lubricated for a long time, whereas the metal thin film type magnetic recording medium has a lubricant layer on its surface. This is because the magnetic layer is likely to be damaged once the lubricant is peeled off.

In order to meet this demand, thermoplastic resin, thermosetting resin, fatty acid, metal salt of fatty acid, fatty acid ester, and alkyl are used as a protective layer or a lubricating layer of the magnetic layer of the ferromagnetic metal thin film type magnetic recording medium. Methods for forming a phosphoric acid ester layer on the surface of a magnetic layer are disclosed in JP-A-60-69824 and JP-A-60-85427.

Various proposals have been made for methods of using a fluorine-containing compound as a protective layer material. For example, in JP-A-61-1107528, a compound having a branched perfluoroalkenyl group is used for improving durability, and in U.S. Pat. No. 3,778,308, a perfluoroalkyl polyether-based compound is used. Is proposed.

Further, in Japanese Patent Publication No. 60-10368, a compound for a protective layer is a terminal-modified perfluoroalkyl polyether in which one or both ends of a perfluoroalkyl polyether molecular chain is modified with a polar group such as a carboxyl group. Has been proposed. Further, as a lubricant for a disc-shaped ferromagnetic metal thin film type magnetic recording medium, a multi-chain type perfluoroalkyl obtained by dehydration condensation of a compound having a plurality of amino groups and a carboxylic acid having a perfluoroalkyl polyether chain. Research using polyetheramides has also been reported (Sugiyama et al .: 34th National Congress of the Lubrication Society of Japan, B.28; Proceedings, 42).
Page 5).

Further, JP-A-64-33713, JP-A-1-112516, and JP-A-3-102614.
JP-A No. 1-112528, JP-A No. 62-
Japanese Patent Publication No. 192029 discloses that a compound having a polar group such as isocyanate and oxo acid improves running durability. Further, JP-A-3-207021 discloses a method of improving still durability by forming a polar group-containing lubricating layer on a metal thin film by vapor deposition and then forming a liquid lubricant having a weaker polarity than that. Is disclosed.

Further, in Japanese Patent Laid-Open No. 63-237216, after forming a protective film on a magnetic layer, by coating perfluoropolyether on a coating film of a hydrophilic group-containing fluorinated compound, the magnetic field of a magnetic disk is reduced. It is described that the durability of the plated film magnetic layer with respect to the head is mainly improved.
Further, JP-A-61-113126 discloses that a polar group-containing perfluoropolyether and a polar group-free perfluoropolyether are mixedly provided on the surface of a magnetic layer,
We propose a metal thin film magnetic recording medium that eliminates the squeal phenomenon during running and the clogging of the magnetic head.

Further, in Japanese Patent Laid-Open No. 4-76816,
It is disclosed that the running property and durability of the metal thin film magnetic recording medium are improved by using a lubricant having a viscosity of 30 cSt or less and a lubricant having a viscosity of 30 cSt or more. To summarize the above conventional techniques, a magnetic recording medium using only perfluoropolyether having weak polarity has a drawback that the lubricant is easily peeled off during running. Moreover, a polar group-containing perfluoropolyether is used. In this type of medium, the stillness durability is insufficient due to the low fluid lubricity, and clogging often caused by unadsorbed lubricant occurs frequently. Frequently, these disadvantages are sought by using perfluoropolyethers having fewer groups.

That is, the techniques disclosed in Japanese Patent Laid-Open No. 63-23716 and Japanese Patent Laid-Open No. 3-207021 provide a fairly ideal system for improving running durability as a current lubricating technique. it is conceivable that. But the former is
It is limited to the protective film, and there is a problem that its effectiveness may not be sufficient unless the coating conditions are properly selected.The latter requires a vacuum deposition process, which complicates the process, and is particularly non-magnetic. There is a problem that it is difficult to control the vapor deposition film thickness when the support is broadly expanded.

In the method of coating the above-mentioned lubricant on the ferromagnetic metal thin film, its running durability is influenced by the adsorption amount and the quality of the adsorption state, which are also related to the surface state of the ferromagnetic metal thin film. Therefore, various surface treatment methods have been performed to improve the surface of the ferromagnetic metal thin film. For example, JP-A-57-138053 and JP-A-59-2
Japanese Patent No. 231 discloses a method of forming an oxide layer on the surface of the magnetic layer by contacting with water after forming the magnetic layer. Further, JP-A-59-229620 discloses a method of surface treatment with a mixed solution of water / organic solvent.

However, the former method has a problem that the strength of the magnetic layer is deteriorated and becomes brittle, which may deteriorate the durability. In the latter method, the treated organic solvent is adsorbed on the surface of the magnetic layer to cause lubrication. In order to prevent the agent from adsorbing to the magnetic layer,
Occasionally, the clogging characteristics deteriorated. And, an effective means for solving the above problem has not been found yet.

[0015]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art. The running durability is improved without lowering the electromagnetic conversion characteristics, especially the friction coefficient is low, and the still An object of the present invention is to provide a ferromagnetic metal thin film type magnetic recording medium having good durability and less head clogging, and a method of manufacturing the same with an easier method and at a lower cost.

[0016]

The object of the present invention is to provide a magnetic recording medium having a ferromagnetic metal thin film on a non-magnetic support, and a polar group-containing perfluoropolyether layer on the ferromagnetic metal thin film. A lubricating layer comprising a polar group-free perfluoropolyether layer and a polar group-containing perfluoropolyether layer in that order is provided, and the polar group-containing perfluoropolyether has a viscosity of 200 to 1000 cSt at room temperature and the polar group-containing perfluoropolyether. The viscosity of polyether at room temperature is 50
cSt or less, and after forming a ferromagnetic metal thin film on a magnetic recording medium and a non-magnetic support by a vacuum film forming method, the ferromagnetic metal thin film is subjected to relative humidity of 50 to 8
0%, contacting in an environment of 20 ° C. or higher, then coating and drying the polar group-containing perfluoropolyether on the ferromagnetic metal thin film, and then coating and drying the polar group-free perfluoropolyether Can be achieved by a method of manufacturing a magnetic recording medium characterized by:

The present invention has a viscosity of 200 to 400 at room temperature on a ferromagnetic metal thin film (hereinafter also referred to as a magnetic layer).
cSt polar group-containing perfluoropolyether (hereinafter,
It may be abbreviated as polar group-containing PFPE. ) Layer,
A polar layer-free perfluoropolyether having a viscosity at room temperature of 50 cSt or less (hereinafter sometimes abbreviated as polar group-free PFPE) is formed thereon to form a two-layered lubricating layer. To do.

Further, in the present invention, before the formation of the lubricating layer, a treatment of bringing the surface of the ferromagnetic metal thin film into contact with the environment of relative humidity 50 to 80% and 20 ° C. or higher (hereinafter referred to as high humidity treatment) is performed. A method for manufacturing a magnetic recording medium is provided. Since the polar group-containing PFPE has a high viscosity and a polar group and thus has a good affinity with a metal, it is firmly bonded to the surface of the ferromagnetic metal thin film to form a stable protective layer. Moreover, since the polar group is oriented toward the ferromagnetic metal thin film and the main chain or the non-polar part is aligned outward, the stable boundary lubricating film can be formed.

On the other hand, since the polar group-free PFPE behaves in a free state without being trapped by the ferromagnetic metal thin film, unlike the polar group-containing PFPE which performs boundary lubrication due to molecular orientation, it has a fluid action as a fluid. It can act lubriciously. Further, since PFPE having a basic skeleton is used for the lower layer and the upper layer of the lubricating layer, the amount of PFPE containing no polar group can be increased, probably because the affinity works, and the lubricating effect can be improved. .

The present invention is more effective than the case where a polar group-containing PFPE and a polar group-free PFPE are mixed on a ferromagnetic metal thin film to provide a single lubricating layer. Adsorption of PFPE to the magnetic layer does not include polar group-containing PFP
It is considered that E does not inhibit. In addition, the present invention provides a method for modifying the surface of a ferromagnetic metal thin film by subjecting the ferromagnetic metal thin film to high-humidity treatment so that the polar group-containing PFPE described above is obtained.
It has the effect of enhancing the adsorption action of.

Further, in the present invention, polar group-containing PF
PE has a high viscosity as described above, and polar group-free PFPE, on the other hand, has a low viscosity, so the friction coefficient is small,
The effect of effectively reducing head clogging was found for the first time, although the still durability was excellent and the details of the mechanism were unknown. In the present invention, the lubricating layers of the polar group-containing PFPE and the polar group-free PFPE, in particular, exhibit their respective functions as a lubricant sufficiently. That is, the polar group-containing PFPE acts as boundary lubrication by firmly adsorbing to the surface of the magnetic layer and orienting the molecules, and the polar group-free PFPE appears at the uppermost layer and acts as liquid lubrication. Non-containing PFPE is a lower layer polar group-containing PFPE
Since it has an affinity with, it is less likely to be peeled off from the surface or volatilized than it is on the surface of the magnetic layer alone, and thus may have a low viscosity advantageous as a liquid lubricant, and in terms of head clogging. It has a great effect.

The polar group-containing PFPE used in the present invention has a viscosity in the range of 200 to 1000 cSt (centistokes) at room temperature, preferably 200 to 600 cSt, more preferably 200 to 400 cSt. Although not regulated, it will be selected from the range of Q1000-5000, preferably 1000-3000.

The polar group-free PF used in the present invention
The viscosity of PE is 50 cSt or less at room temperature, preferably 3
The molecular weight is in the range of 0 to 50 cSt, and is not particularly limited as the molecular weight, but it is 1500 to 5000, preferably 150.
It may be selected from the range of 0-3000. Where cSt
Can be measured with an E-type viscometer manufactured by Tokyo Keiki Co., Ltd.

Polar group-free PFPE used in the present invention
Is arbitrary as long as it is a chemical structure of a normal perfluoropolyether (PFPE), and most of H of the polyether structure, usually 50% or more, may be replaced by F. , Does not necessarily mean that all of them must be replaced with F. Also, polar group-containing P
FPE is a structure in which a polar group is introduced into the basic structure of the polar group-free PFPE, and the meaning of PFPE is the same as the polar group-free PFPE.

Specific examples of the polar group-free PFPE include perfluoro n-propylene oxide polymer [(C
F ₂ CF ₂ CF ₂ O) _n ; n = 4 to 20], perfluoroisopropylene oxide polymer [(CF (CF ₃ ) C
F ₂ O) _n ; n = 4 to 20], perfluoroethylene oxide polymer [(CF ₂ CF ₂ O) _n ; n = 4 to ₂ ]
0], perfluoromethylene oxide polymer [(CF ₂
O) _n ; n = 8 to 40] and copolymers thereof.

The copolymer may be a perfluoroisopropylene oxide-perfluoromethylene oxide copolymer [(CF (CF ₃ ) CF ₂ O) _n- (CF
₂ O) _m ], perfluoroethylene oxide-perfluoromethylene oxide copolymer [(CF ₂ CF ₂ O) _n
- (CF ₂ O) _m], and the like. Polar group-free PFP
The molecular terminal of E is preferably composed of any one of trifluoromethyl, difluoromethyl, monofluoromethyl and methyl group.

The structure of PFPE of polar group-containing PFPE is
The polar group-free PFPE structure described above can be used. The polar group of the polar group-containing PFPE in the present invention is not particularly limited, and examples thereof include an oxo acid group, a sulfone group, a sulfoxide group, a diphenyl ether group, an epoxy group, an alcohol hydroxyl group, an ester group, a silane coupling group, and an alkene. Group, chelate group, heterocyclic group and the like.

Among them, preferable polar groups are oxo acid group, sulfone group, sulfoxide group and diphenyl ether group. Of these, an oxo acid group is particularly preferable. According to the physics and chemistry dictionary (published by Iwanami Shoten), for example, an oxo acid is an oxygen in which all the atoms bonded to the central atom are oxygen, and hydrogen is bonded to a part or all of the oxygen to form a hydroxyl group, and the hydrogen becomes an aqueous solution. A substance that produces hydrogen ions and exhibits the properties of an acid. However, a derivative in which a carbon atom is bonded to a central atom such as carboxylic acid or sulfonic acid is also included in this derivative.

The oxo acid group in the present invention includes oxo acid derivatives such as carboxyl group and oxo acid ester groups such as sulfuric acid ester. The position and number of polar groups in the perfluoropolyether molecule are not particularly limited. The bond between the polar group and the main chain perfluoropolyether may be through another molecular chain such as amide, benzene, or alkylene.

The size of the main chain perfluoropolyether preferably has 6 to 150 carbon atoms, and more preferably 9 to 50 carbon atoms. For _{example, (CF 2 CF 2 CF 2} O) n; n = 4~20, (C
F (CF ₃ ) CF ₂ O) _n ; n = 4 to 20, (CF ₂ C
F ₂ O) _n ; n = 4 to 20, (CF ₂ O) _n ; n = 8 to
40, also, combinations of the above monomeric units, for _{example, (CF (CF 3) CF} 2 O) n - is exemplified by (CF ₂ O) _m, etc. _{- (CF 2 O) m (} CF 2 CF 2 O) n .

If the number of carbon atoms is too small, the above conditions cannot be satisfied and the running property becomes problematic. On the contrary, if the number of carbon atoms is too large, the mobility of the molecules is large, so that the molecules interfere with each other during coating, It becomes difficult to adsorb. Since it is necessary to apply it to the surface of the magnetic layer in a short time at the time of application, the influence of the mobility is likely to be excessive. As a result, durability may not be sufficiently imparted, which is not desirable.

In the present invention, polar group-containing PFPE is used.
Is sufficiently adsorbed on the ferromagnetic metal thin film if the conditions of the present invention are satisfied, and the adsorption amount is 4 mg / m ^{2 as a} saturated adsorption amount that covers the entire surface of the ferromagnetic metal thin film with one molecular layer.
That is all. The specific measuring method is 25 using a fluorine-based solvent (for example, ZS100 manufactured by Montefluos Co., Ltd.) used when applying the polar group-containing PFPE to the ferromagnetic metal thin film.
It can be determined from the adsorption isotherm at ℃.

The molecular chain of the polar group-containing PFPE may be linear or branched. If the branched molecular chain is too large, the volume occupied in the space of the molecule becomes large, so that a dense protective layer cannot be formed, and at the same time, the orientation of the molecule becomes irregular. Therefore, in forming the upper polar group-free PFPE layer. Is not desirable. Specific examples of the polar group-containing PFPE include compounds 1 to 8 of chemical formulas 1 and 2. It goes without saying that the compounds that can be used as the polar group-containing PFPE in the present invention are not limited thereto.

[0034]

[Chemical 1]

[0035]

[Chemical 2]

Compounds 1 to 3 are EIDu Pont de
Commercially available from Nemours & Company (Inc.), Daikin Industries, Ltd. and Montecatini Company. Polar group-containing PF provided on the surface of the ferromagnetic metal thin film of the magnetic recording medium of the present invention
The amount of PE ^{is, 4.0mg / m 2 ~30mg / m} 2, preferably in the 10-20 mg / m ^2, the weight ratio of (coating weight / saturated adsorption amount) is 1 to 3 are preferred.

The coating amount referred to here is a fluorescent X-ray analyzer (manufactured by Shimadzu Corporation, SXF-1000) for the sample after coating.
Is a value obtained by quantifying fluorine on the ferromagnetic metal thin film of the magnetic recording medium. When the amount of the polar group-containing perfluoropolyether provided on the surface of the ferromagnetic metal thin film is small, the amount of the polar group-free PFPE formed on it is also small, and the above-mentioned functions of both layers can be sufficiently exhibited. It is not preferable because it disappears.

If the coating amount of the polar group-containing PFPE is within the above range, a sufficiently large amount of the polar group-free PFPE can be retained thereon, so that the coating amount of the polar group-free PFPE is 1.0.
To 10 mg / m ^2, preferably in the range of 2-5 mg / m ^2. The above polar group-containing PFPE or polar group-free PFPE
PE is basically used alone in each layer, but may be used in combination with other lubricants within the scope of the objects and effects of the present invention.

Other lubricants that can be mixed are fatty acids, metal soaps, fatty acid amides, fatty acid esters, higher aliphatic alcohols, monoalkyl phosphates, dialkyl phosphates, trialkyl phosphates, paraffins, silicone oils, animal and vegetable oils. , Mineral oil, higher aliphatic amine; inorganic fine powder of graphite, silica, molybdenum disulfide, tungsten disulfide, etc .; resin fine powder of polyethylene, polypropylene, polyvinyl chloride, ethylene-vinyl chloride copolymer, polytetrafluoroethylene, etc. An α-olefin polymer; an unsaturated aliphatic hydrocarbon which is liquid at room temperature and the like.

In the present invention, the formation of the lubricating layer is performed by using a ferromagnetic metal thin film at 20 ° C. or higher at 50 to 80% RH (relative humidity).
It is preferable to perform the treatment after exposing to the atmosphere, that is, the high humidity treatment. As a specific method of the high humidity treatment in the present invention, after the magnetic layer is formed, the magnetic layer is left to be exposed in an apparatus kept at a constant humidity, or if it is rolled, You just have to rewind.

At this time, the surface is, for example, a surface having a contact angle with water of 16 ° or less and a contact angle with methylene iodide of 25 ° or less. The temperature when performing the high humidity treatment of the present invention is 20 ° C. or higher, preferably 20 to 30 ° C., and the humidity is in the range of 50 to 80% RH. Also, the humidity can be used within a range where dew condensation does not occur on the surface of the magnetic layer.
0-80% is preferable. A few seconds is sufficient for the processing time, and there is no problem as long as the condensation does not occur for a long time. Drying may be performed after the treatment, but there is no problem if the drying is not performed.

The action mechanism of the high humidity treatment in the present invention will be briefly described as follows. When the metal thin film magnetic layer is brought into contact with water molecules in a high humidity treatment, a layer having a high affinity with the polar group of the polar group-containing PFPE is formed on the surface of the ferromagnetic metal thin film. It is presumed that the adsorption of the group-containing PFPE will become stronger.

In the high-humidity treatment of the present invention, the temperature conditions are remarkably milder than in the prior art. Therefore, the surface of the ferromagnetic metal thin film subjected to the high-humidity treatment has a protective layer having a constant thickness as in the prior art. However, the surface structure of the ferromagnetic metal thin film is simply modified, and the polar group-containing PF is used.
The interaction with PE is enhanced. It has been confirmed in the present invention that the protective layer having a certain thickness formed by the conventional method using water and oxygen is rather deteriorated or fragile in film quality, resulting in reduced durability.

Following this high humidity treatment, PFP containing polar groups
The formation process of the lower layer of the lubricating layer made of E is performed. Therefore, in the present invention, if the high-humidity treatment is performed immediately before the formation of the lubricating layer, an arbitrary ferromagnetic metal thin film treatment step may be included before the high-humidity treatment. For example, there are the following methods as such preferable processing steps. Method 1) Formation treatment of rust preventive agent: A non-magnetic support is vapor-deposited with a metal vapor stream mainly composed of Co, particularly Co, in an atmosphere containing oxygen gas to form a ferromagnetic metal thin film, and then a known anti-corrosion agent is formed. A step of forming a rust preventive layer by applying a solution containing a rusting agent such as benzotriazole, benzimidazole or the like and a derivative thereof on the ferromagnetic metal thin film. Method 2) Heat treatment of a ferromagnetic metal thin film: A ferromagnetic metal thin film is formed on a non-magnetic support by vapor deposition of a metal vapor stream containing a metal, particularly Co, in an atmosphere containing oxygen gas. A step of heat-treating the metal thin film at 80 to 180 ° C. for 1 to 60 seconds. And Method 3) Inert gas treatment of ferromagnetic metal thin film: After forming a ferromagnetic metal thin film on a non-magnetic support by vapor-depositing a metal vapor stream containing a metal, particularly Co, in an atmosphere containing oxygen gas. A step of performing a treatment for holding the ferromagnetic metal thin film in an inert gas.

After providing the magnetic layer, the above steps are optionally performed, and then the high humidity treatment of the present invention is performed, and then the lubricating layer forming treatment is performed. For example, when the step 1) is selected, the polar part of the rust preventive agent and the polar group-containing PFPE formed on the ferromagnetic metal thin film at this time interact with each other.
The amount of adsorption is less likely to decrease as compared with the case where no anticorrosive layer is provided.

In the present invention, as a method of forming a lubricating layer on a ferromagnetic metal thin film, that is, a method of forming a polar group-containing PFPE layer on a ferromagnetic metal thin film and a polar group-free PFPE layer on a polar group-containing PFPE. Is prepared by dissolving a material (polar group-containing PFPE or polar group-free PFPE) in an organic solvent, coating or spraying it on a substrate (a ferromagnetic metal thin film-supporting non-magnetic support or a polar group-containing PFPE layer forming body), and then drying. Method, rubbing the material-impregnated object on the substrate to apply, dipping the substrate in a solution of the material in an organic solvent to adsorb the material to the substrate surface, Langmuir-Blodgett method, etc. And a method of forming a monomolecular film of the material.

In the above method, the lower layer of the lubricating layer is preferably formed by a dip method, a coil bar method or a gravure method.
It is provided by coating and drying. After accelerating the adsorption, after drying, preferably at room temperature and atmospheric pressure for 1 hour or more, particularly preferably 5 hours or more, a solution in which polar group-free PFPE is dissolved is applied by the same method and dried to form an upper layer of the lubricating layer. obtain. The solvent of the polar group-containing PFPE is not particularly limited. Further, as the solvent of the polar group-free PFPE, a solvent capable of dissolving both the polar group-containing PFPE and the polar group-free PFPE such as a fluorine-based solvent is preferable. This is to prevent coating unevenness at the time of coating the upper layer and at the same time to remove excess polar group-containing PFPE in the lower layer at the time of coating the upper layer.

The reason why 5 hours or more is usually required from the lower layer coating to the upper layer coating is that the polar group-containing PFPE immediately after coating the lower layer is sufficiently adsorbed on the surface of the magnetic layer due to reasons such as mixed adsorption with a solvent. This is because the effect of the present invention cannot be sufficiently obtained if the upper layer is applied immediately after the application of the lower layer. According to the present invention, a lubricating film containing polar group-containing PFPE near the surface of the magnetic layer and a lubricating film containing polar group-free PFPE can be formed on the magnetic layer surface by the above manufacturing method. Therefore, as compared with the case where two kinds of PFPE are mixed and applied, the steric hindrance of the polar group-free PFPE can be eliminated, so that the adsorption amount of the polar group-containing PFPE can be increased. At the same time, the amount of unadsorbed polar group-containing PFPE existing on the outermost surface of the magnetic recording medium can be reduced, so that the occurrence rate of clogging can be reduced. In addition, since the conventional general coating device can be used for the preparation of the lubricating layer, stable production is possible without introducing new equipment.

Further, in the present invention, in order to improve the adhesion of the lubricating layer to the underlying metal thin film, UV is applied before the high humidity treatment.
The surface of the ferromagnetic metal thin film can be modified by a method such as irradiation glow or plasma. The material of the ferromagnetic metal thin film in the present invention is iron, cobalt, nickel or other ferromagnetic metals or Fe-Co, Fe-Ni, Co-N.
i, Fe-Rh, Co-P, Co-B, Co-Y, Co
-La, Co-Ce, Co-Pt, Co-Sm, Co-
Mn, Co-Cr, Fe-Co-Ni, Co-Ni-
P, Co-Ni-B, Co-Ni-Ag, Co-Ni-
Nd, Co-Ni-Ce, Co-Ni-Zn, Co-N
A ferromagnetic alloy such as i-Cu, Co-Ni-W, and Co-Ni-Re is formed by a vapor deposition method, and the film thickness thereof is in the range of 0.02 to 2 μm, particularly 0.05 to
The range of 1.0 μm is desirable.

The ferromagnetic metal thin film is made of O, N, C.
r, Ga, As, Sr, Zr, Nb, Mo, Rh, P
d, Sn, Sb, Te, Pm, Re, Os, Ir, A
It may contain u, Hg, Pb, Mg, Bi and the like. The ferromagnetic metal thin film of the magnetic recording medium in the method of the present invention is formed on the non-magnetic substrate by a vacuum film forming method such as a vacuum evaporation method or a sputtering method. Oxygen is simultaneously introduced into the film forming chamber so that the ferromagnetic metal thin film contains a predetermined amount of oxygen.

The oxygen content in the ferromagnetic metal thin film is AES
(Auger electron spectroscopy) Calculated by depth analysis. In the present invention, the oxygen content in the ferromagnetic metal thin film is 15 at.
% Or more, and preferably 20 at% or more, the object of the invention can be effectively achieved. That is, 15 at% or more is preferable in order to increase the saturated adsorption amount of the polar group-containing PFPE and to strengthen the adsorption.

If the oxygen content exceeds 30 at%, the nonmagnetic component increases and the characteristic of the electromagnetic conversion characteristics of the ferromagnetic metal thin film is lost, which is not preferable. Further, when the oxygen distribution in the ferromagnetic metal thin film is viewed in the thickness direction of the ferromagnetic metal thin film, it is desirable that the oxygen content in the vicinity of the non-magnetic substrate and in the vicinity of the surface of the magnetic layer is higher than that in the central portion.

That is, AES (Auger electron spectroscopy)
In depth analysis, when the ferromagnetic metal thin film is divided into five equal parts in the thickness direction, the region from the surface to the non-magnetic support up to ⅕ of the total thickness is near the surface, the non-magnetic support and the strong magnetic field. When the region up to ⅕ of the total thickness from the interface with the magnetic metal thin film is set near the non-magnetic support, oxygen in the ferromagnetic metal thin film is near the surface and near the non-magnetic support. The oxygen content in the central portion of the region other than that is preferably such that the oxygen distribution is smaller than either the oxygen content near the surface or the oxygen content near the non-magnetic support.

Further, it is desirable that the oxygen content near the surface of the ferromagnetic metal thin film and the oxygen content near the non-magnetic support are 5 at% or more, and the oxygen content in the central portion is 3 to 4 at%. Examples of the crystal structure of the ferromagnetic metal thin film of the present invention include hexagonal crystal and orthorhombic columnar crystal.

The orthorhombic columnar crystals include, for example, those in which the crystal columns are obliquely folded and arranged in a scale-like shape and in a scale-like manner, when the characteristic features of the structure are specifically described. The magnetic layer of the present invention may be composed of a plurality of layers having the same composition but different crystal structures or the same crystal structure but different orientations and / or different compositions regardless of the crystal structure. For example, when the magnetic layer is composed of two layers having the same composition and the same crystal structure in which the tilt directions of the orthorhombic columnar crystal structure are crossed in opposite directions, the electromagnetic conversion characteristics and the durability are different depending on the traveling direction of the head. It is preferable in reducing the noise and reducing the noise.

In the present invention, when the magnetic layer is composed of orthorhombic columnar crystals by the vacuum film-forming method, if a concrete method is shown, an electron beam of 30 KeV is used as an evaporation heating source and the vacuum of the film-forming chamber is used. degrees oxygen gas pressure in the deposition chamber by introducing while kept below 1 × 10 ^-3 Torr, on a nonmagnetic support placed into the deposition chamber as follows 1 × 10 ^-4 Torr, a ferromagnetic metal Is obliquely vapor-deposited at an incident angle of 0 to 50 degrees.

It is desirable that the film thickness of the ferromagnetic metal thin film is usually in the range of 500 to 3000 Å. Further, an undercoat layer may be provided between the non-magnetic substrate and the ferromagnetic metal thin film in order to improve the adhesion of the ferromagnetic metal thin film. Further, in the present invention, a function different from the undercoat layer is provided in either or both of the ferromagnetic metal thin film and between the ferromagnetic metal thin film and the non-magnetic support in order to impart desired properties to the ferromagnetic metal thin film. The non-magnetic intermediate layer may be independently provided. For example, the non-magnetic intermediate layer may contain the lubricant or the like used in the lubricating layer to more reliably control the lubricity and further improve the mechanical properties of the magnetic layer.

Examples of the non-magnetic intermediate layer include a layer made of a metal or a metal oxide, a layer made of a resin and / or an inorganic or organic filler, and the like. The thickness of the non-magnetic intermediate layer is in the range of 20 to 500Å, preferably 50 to 200Å. As the non-magnetic support used in the present invention, polyethylene terephthalate, polyimide, polyamide, polyvinyl chloride, cellulose triacetate, polycarbonate,
A plastic base such as polyethylene naphthalate or polyphenylene sulfide, or Al, Ti, stainless steel or the like can be used.

In order to improve the running durability, it is necessary to provide minute protrusions on the surface of the non-magnetic support before forming the ferromagnetic metal thin film, and as a result, appropriate irregularities are provided on the surface of the magnetic layer. It is effective. The existence density of the fine projections on the surface of the non-magnetic support is 2 × 10 ⁶ to 2 × 10 ⁸ pieces / mm ² , and the height of the projections is preferably 1 to 50 nm. The thickness varies depending on the application, but is usually 3 to 50.
μm.

Further, in order to improve the runnability of the magnetic recording medium of the present invention, fine powder such as carbon black and a binder resin are mainly formed on the surface of the non-magnetic substrate opposite to the surface having the ferromagnetic metal thin film. It is also possible to provide a back coat layer composed of a coating film. The shape of the magnetic recording medium is tape, sheet,
It may be either a card or a disk, but tape-shaped or disk-shaped is particularly preferable.

Next, preferred embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a diagram schematically illustrating a cross section of a magnetic recording medium of the present invention. 1 is a magnetic recording medium of the present invention, 2 is a non-magnetic support, 3 is a ferromagnetic metal thin film, 4 is a lubricating layer, a lubricating film containing a polar group-containing PFPE, and a lubricating film containing a polar group-free PFPE. The film 6 is formed, and 7 is a back coat layer.

The non-magnetic support 2 is not particularly limited,
A film made of polyethylene terephthalate, polyethylene naphthalate, polyimide, aramid or the like having a film thickness of 3 to 12 μm is preferable. In addition, an undercoat layer for controlling the surface shape of the magnetic layer may be formed on the surface thereof. The ferromagnetic metal thin film 2 is C deposited in oxygen by a continuous winding type vapor deposition machine.
It is an o-Ni-O, Co-O based metal thin film. The layer structure is not particularly limited, and examples thereof include a single layer, a multilayer of a plurality of layers, and a multilayer of a plurality of layers including a non-magnetic layer.

The polar group-containing PFPE forming the lubricating film 5 (lower layer) containing the polar group-containing PFPE has a polar group at at least one of the molecular ends, and the polar group is preferably a carboxyl group, a sulfone group or the like. . Polar group-free PF
Polar group-free PF forming the lubricating film 6 (upper layer) containing PE
It is preferable that PE does not have a polar group at both ends of the molecule and the end is composed of any one of trifluoromethyl, difluoromethyl, monofluoromethyl and methyl groups. Further, in order to reduce the occurrence rate of clogging, it is preferable to use a liquid that is liquid at room temperature and has a viscosity at 20 ° C. of 50 cSt or less.

The back coat layer 7 is usually used and is not particularly limited.

[0065]

EXAMPLES The novel features of the present invention will be described more specifically with reference to the following examples and comparative examples. Example 1 Worm-shaped projections, particle size 250Å, density 9 × 10 ⁶ pieces / mm
10 μm thick with minute protrusions consisting of ² silica particles
Co-Ni (80-20) alloy was obliquely vapor-deposited on the non-polyethylene terephthalate non-magnetic support of Example 1 using a continuous winding type vacuum vapor deposition machine while introducing oxygen gas so that the film thickness was 2000 Å. A coil bar was prepared by dissolving 0.44% by weight of a polar group-containing PFPE (KRYTOX 157FSL manufactured by DuPont, polar group: carboxyl group) having a viscosity of 400 cSt at 20 ° C. in a fluorine-based solvent (FOMBLIN ZS100) on the magnetic layer. Was applied, dried and wound up. Six hours after application of the first layer, PFPE containing no polar groups and having a viscosity of 40 cSt at 20 ° C. on the lubricating film.
(KRYTOX 143AZ, number average molecular weight by NMR 1850, structural formula is shown in Chemical Formula 3 below) in a fluorine-based solvent (FOMBLINZS100) in an amount of 0.11% by weight was applied by a coil bar and dried. Further, a back coat on the back surface of the support was applied to produce the film, and then the raw fabric was cut into 8 mm to form a tape.

[0066]

[Chemical 3]

Comparative Example 1 Polar group-containing PFPE (KRYTOX 157FSL, polar group: carboxyl group) and polar group-free PFPE (KRY).
TOX 143AZ, Chemical formula 3) is used as a fluorine-based solvent (FOMB
The concentration after mixing with LIN ZS100) is 0.4 each.
A tape was manufactured in exactly the same manner as in Example 1 except that the tape was dissolved and applied so as to be 4% by weight and 0.11% by weight.

Comparative Example 2 Except that the polar group-containing PFPE was changed to one having the same basic structure as KRYTOX 157FSL and a viscosity at 20 ° C. of 1100 cSt (KRYTOX 157FSM, polar group: carboxyl group), completely different from Example 1. A tape was produced in the same manner. Comparative Example 3 In Example 1, polar group-containing PFPE was added to KRYTOX.
Same basic structure as 157FSL, but viscosity at 20 ℃ is 1
800cSt (KRYTOX 157FS
A tape was prepared in exactly the same manner as in Example 1 except that H, polar group: carboxyl group) was used.

Comparative Example 4 In Example 1, polar group-free PFPE was used as KRYTOX.
Same basic structure as 143AZ, but viscosity at 20 ℃ is 15
Polar group-free PFPE (KRYTOX 1
43AY), and a tape was produced in exactly the same manner as in Example 1.

Example 2 Example 2 was repeated except that the surface of the magnetic layer was subjected to high humidity treatment so that it was exposed to air at 30 ° C. and 80% RH for 5 seconds immediately before the application of the polar group-containing PFPE. A tape was prepared exactly as in Example 1. As described above, Table 1 summarizes the amount of lubricant adsorbed, the friction coefficient with respect to the stainless steel guide pole, the still durability, and the number of paths of complete clogging when actually running at 8 mm VTR, which were examined by ESCA in Examples and Comparative Examples. It was

It should be noted that the amount of lubricant adsorbed is ES after tape formation.
The F peak of CA and the background ratio (F / BG) were evaluated. The F / BG ratio is an index of the adsorption amount, ESCA
This is because the non-adsorbed excess lubricant is volatilized from the thin ferromagnetic metal screen since the measurement by the method is performed under high vacuum.
The still durability was tested using an 8 mm VTR and a running tension of 20 g. The environment at this time is 23 ° C, 10% RH
And The pause button was pressed during image reproduction, and the time until the image disappeared was measured and evaluated.

The friction coefficient (μ) is the tension (T) of 50 g between the magnetic layer surface of the magnetic tape sample and the stainless steel pole.
₁ ), measure the tension (T ₂ ) required for running the tape at a constant speed of 10 mm / sec by contacting it at a wrapping angle of 180 ° C.
Was calculated. The running test of μ = (1 / π) ln (T ₂ / T ₁ ) VTR was performed at 8 ° V.
The test was carried out by running 120 minutes long 50 times in a 0% RH environment. The running test was conducted on two tapes per one sample to evaluate clogging. Output is 6d for complete clogging
It was assumed that the state in which B was lowered continued for 1 minute or more, and the evaluation was made by the number of traveling passes when the complete clogging occurred. Also,
For the samples in which complete clogging did not occur, the one in which the output reduction of 6 dB continued for 0.05 seconds or more during the 50-pass running was regarded as the instantaneous clogging, and the rate of occurrence per hour was evaluated.

The results are shown in Table 1.

[0074]

[Table 1]

As is clear from Table 1, the examples to which the present invention is applied can increase the amount of lubricant adsorbed with the same lubricant prescription amount as compared with the comparative examples, and therefore complete clogging occurs. It can be seen that this can be prevented. In the present invention, after the solution containing the polar group-containing PFPE is applied onto the ferromagnetic metal thin film, the solution containing the polar group-free PFPE is further applied onto the lubricating film after a lapse of 6 hours, whereby The amount of adsorption can be increased. The medium to which the present invention is applied is excellent in runnability and durability and can prevent clogging in particular.

[0076]

Industrial Applicability According to the present invention, a polar group-containing P having a viscosity of 200 to 1000 cSt at room temperature is formed on a ferromagnetic metal thin film.
A stable boundary lubrication film is formed at the interface with the ferromagnetic metal thin film by forming an FPE layer and then forming a two-layer structure lubricating layer on which a polar group-free PFPE having a viscosity at room temperature of 50 cSt or less is provided. Polar group-containing PFPE layer capable of forming a film and a polar group-free PFP that acts hydrodynamically
Since the E layer was able to share the functions, the absolute amount of each lubricant was increased and the adsorption power was improved, so the lubrication effect was improved, good running durability could be provided, and head clogging could be significantly improved. A metal thin film type magnetic recording medium can be provided.

[Brief description of drawings]

FIG. 1 is a diagram schematically showing a cross section of an example of a magnetic recording medium of the present invention.

[Explanation of symbols]

 1 Magnetic Recording Medium of the Present Invention 2 Nonmagnetic Support 3 Ferromagnetic Metal Thin Film 4 Lubricating Layer 5 Lubricating Film Containing Polar Group-Containing PFPE 6 Lubricating Film Containing Polar Group-Free PFPE 7 Backcoat Layer

Claims (3)

[Claims] 1. A magnetic recording medium having a ferromagnetic metal thin film on a non-magnetic support, comprising a polar group-containing perfluoropolyether layer and a polar group-free perfluoropolyether layer on the ferromagnetic metal thin film. Is provided in this order, the viscosity of the polar group-containing perfluoropolyether at room temperature is 200 to 1000 cSt, and the viscosity of the polar group-free perfluoropolyether at room temperature is 50 cSt or less. A magnetic recording medium characterized by: 2. The ferromagnetic metal thin film is formed on a non-magnetic support and before the lubricating layer is formed thereon, in an environment of relative humidity of 50 to 80% and 20 ° C. or higher. The magnetic recording medium according to claim 1, which has been subjected to a high-humidity treatment to bring it into contact with the magnetic recording medium. 3. A ferromagnetic metal thin film is formed on a non-magnetic support by a vacuum film forming method, and then the ferromagnetic metal thin film is brought into contact with an environment of relative humidity 50 to 80% and 20 ° C. or higher, and then, A method for producing a magnetic recording medium, characterized in that a polar group-containing perfluoropolyether is applied and dried on the ferromagnetic metal thin film, and then a polar group-free perfluoropolyether is applied and dried.