JPH08180385A - Magnetic recording medium and its production - Google Patents

Abstract

PURPOSE: To produce a magnetic recording medium having a low coeff. of friction of the surface and excellent in durability while satisfying glide height characteristics. CONSTITUTION: This magnetic recording medium has a substrate 11, a magnetic layer 13 disposed on the substrate 11, a protective layer 14 disposed on the magnetic layer 13 and a lubricant layer 15 disposed on the protective layer 14. The protective layer 14 contains a 1st protective layer consisting essentially of carbon and silicon and a 2nd protective layer based on carbon. The lubricant layer 15 is made of a polymer obtd. by vapor phase polymn. and consists of a fixed layer 15a stuck on the protective layer 14 and a free layer 15b formed on the fixed layer 15a.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording medium such as a magnetic disk having a low friction coefficient and excellent durability, and a method for manufacturing the same.

[0002]

2. Description of the Related Art Conventionally, a magnetic recording medium such as a magnetic disk is provided with a protective layer or a lubricant layer on the magnetic recording layer in order to improve its durability. It is widely practiced. With the recent increase in recording density and the like, there is a demand for a magnetic recording medium that satisfies the glide height characteristics and has improved durability.

Regarding the protective layer, JP-A-53-7601
Japanese Patent Publication No. 3 and Japanese Patent Publication No. 55-29500 propose a technique of providing a hard protective film of an oxide such as polysilicic acid or SiO ₂ on the magnetic recording layer by a coating means or a thin film forming means such as sputtering. . Although polysilicic acid and SiO ₂ are hard and resistant to abrasion, they have the drawback of being brittle.
Therefore, due to the impact of the magnetic head coming into contact with the magnetic disk, polysilicic acid or SiO ₂ may be chipped and the crushed particles may adhere to the surface of the magnetic disk or the magnetic head may be clogged.

Therefore, in order to deal with the above-mentioned drawbacks, Japanese Patent Laid-Open No.
In 2-97123, it is proposed to use a protective film made of SiC. However, with the demand for higher durability of the magnetic recording medium and the higher hardness of the magnetic head, it is gradually found that the surface hardness and lubricity of the magnetic recording medium are insufficient even if a protective film made of SiC is used. I've been

Further, JP-A-5-22555 and JP-A-5-22555 disclose a protective layer composed of a plurality of layers and containing a C element derived from glassy carbon as a main component. What is made of the material to be described is described.
However, the publication does not describe the use of the protective layer in combination with a specific lubricant layer to improve both the glide height characteristics and the durability of the magnetic recording medium.

On the other hand, regarding the lubricant layer, a layer of a fluoropolymer is directly formed on the protective layer by a surface polymerization method using a laser beam, and the lubricant layer fixed to the surface of the protective layer is formed. A forming method and the like have been proposed. However, in the above-mentioned method, since the lubricant layer is wholly fixed to the surface of the protective layer, the degree of adhesion between the lubricant layer and the protective layer is improved, but the required durability is still satisfied. It wasn't something to do.

On the other hand, a method has been proposed in which the lubricant layer has a two-layer structure consisting of a fixed layer and a free layer to improve durability. In this case, increasing the thickness of the free layer improves the durability to the required level. However, when the thickness of the free layer is increased so that the durability is improved to the required level, the surface roughness of the magnetic recording medium is small, so that the friction coefficient of the lubricant layer increases and There is a problem that the head sticks to the magnetic recording medium.

Therefore, an object of the present invention is to provide a magnetic recording medium having a low surface friction coefficient and excellent durability while satisfying the glide height characteristic, and a method for manufacturing the same.

[0009]

DISCLOSURE OF THE INVENTION As a result of intensive studies to solve the above problems, the present inventors have found that two protective layers formed of a specific substance and a specific compound are used. It was also found that a magnetic recording medium having a combination with a lubricant layer having a specific structure can achieve the above object.

The present invention has been made on the basis of the above findings, and includes a support, a magnetic layer provided on the support, a protective layer provided on the magnetic layer, and a protective layer provided on the magnetic layer. A magnetic recording medium comprising a lubricant layer provided on
The protective layer includes a first protective layer formed mainly of carbon and silicon and a second protective layer formed mainly of carbon, and the lubricant layer is formed by vapor phase polymerization. And a free layer formed on the fixed layer and formed on the protective layer, and a free layer formed on the fixed layer. It has achieved its purpose.

The present invention also provides, as a preferable method for producing the above magnetic recording medium, a first method containing carbon and silicon as main components.
And a second protective layer containing carbon as a main component are formed, and when forming the lubricant layer, vapor phase polymerization is performed under vacuum conditions, and a fluorocarbon-based compound and oxygen are polymerized to provide lubrication. After the first polymerization step of forming the agent layer and the introduction of steam,
A method for producing a magnetic recording medium, which comprises sequentially performing a vapor phase polymerization under a vacuum condition and polymerizing a fluorocarbon compound and oxygen to form a lubricant layer. It is provided.

The magnetic recording medium of the present invention will be described in detail below. The magnetic recording medium of the present invention comprises a support, a magnetic layer provided on the support, a protective layer provided on the magnetic layer, and a lubricant layer provided on the protective layer. It is a magnetic recording medium. The magnetic recording medium of the present invention is particularly useful as, for example, a magnetic disk.

The above-mentioned support used in the present invention is
Either a magnetic support or a non-magnetic support can be used, but a non-magnetic support is generally used. As the non-magnetic support, for example, carbon such as glassy carbon, tempered glass, crystallized glass, aluminum and aluminum alloys, titanium and titanium alloys, ceramics, resins, and substrates made of composite materials thereof are used. Among these, the substrate made of glassy carbon is particularly excellent in heat resistance, light weight and the like, and can be particularly preferably used in the present invention.

If necessary, the support may be subjected to various texture treatments. Examples of such a texture treatment include treatment using a polishing tape or abrasive grains, etching treatment with an acid, thermal oxidation or anodization treatment,
Examples thereof include a treatment for depositing a silicate compound on the surface by spin coating, a plasma ashing treatment, or a surface roughening treatment by sputtering texture or the like for forming irregularities on the surface by sputtering a metal.

In the present invention, the magnetic layer provided on the support may be, for example, a metal thin film type magnetic layer formed by a physical vapor deposition method. Examples of the material for forming the metal thin film type magnetic layer include CoCr, CoNi, CoCrX, and C.
oNiX and CoWX (where X is Ta, Pt, A
u, Ti, V, Cr, Ni, W, La, Ce, Pr, N
d, Pm, Sm, Eu, Li, Si, B, Ca, As,
Y, Zr, Nb, Mo, Ru, Rh, Ag, Sb and H
Preferable examples include Co-based magnetic alloys containing Co as a main component represented by (indicating one or more metals selected from the group consisting of f and the like). When using,
These can be used alone or as a mixture of two or more kinds. The thickness of the magnetic layer is preferably 20 to 50 nm, but is not limited to this range.

In the present invention, the protective layer provided on the magnetic layer is a first protective layer containing carbon and silicon as main components and a second protective layer containing carbon as main components. Including and

First, the first protective layer will be described. The first protective layer is mainly composed of carbon and silicon. The silicon content in the first protective layer is preferably 0.1 atomic% or more and less than 50 atomic%, and more preferably 10 to 30 atomic%. On the other hand, the ratio of carbon in the protective layer is 50 to 99.
It is preferably atomic%, and more preferably the ratio of carbon is 70 to 90 atomic%.

The carbon in the first protective layer is particularly preferably derived from glassy carbon.
By including carbon derived from glassy carbon in the first protective layer, it is possible to reduce defects in the protective layer, increase hardness, and improve CSS durability and corrosion resistance.

As described above, the first protective layer is formed mainly of carbon and silicon, but its form is like a film in which SiC particles are bonded to a carbon matrix.
In particular, when carbon derived from glassy carbon is used as the carbon, the form of the first protective layer becomes a form more like a film having a diamond structure.

In addition to carbon and silicon, the first protective layer may contain other elements as required. Examples of such other elements include oxygen, hydrogen, nitrogen and the like.

When oxygen is contained in the first protective layer,
The ratio is preferably 0.1 atom% or more and less than 50 atom%, and more preferably the ratio of silicon is 10 to 30 atom%.

The thickness of the first protective layer is 5 to 20 nm.
It is preferable, but not limited to this range.

Next, the second protective layer will be described. The second protective layer is formed mainly of carbon. Particularly preferably, the carbon in the second protective layer is derived from glassy carbon. The inclusion of carbon derived from glassy carbon in the second protective layer has a preferable effect of improving CSS durability.

As described above, the second protective layer is formed with carbon as the main component, but its form is like an amorphous film having a graphite structure. In particular, when carbon derived from glassy carbon is used as the carbon, the second protective layer has a form similar to an amorphous film having a diamond structure.

The second protective layer may contain other elements other than carbon, if necessary. Examples of such other elements include hydrogen, oxygen, nitrogen, and the like.

The thickness of the second protective layer is 3 to 10 nm.
It is preferable, but not limited to this range.

As described above, the carbon in the first protective layer or the second protective layer is preferably derived from glassy carbon, and particularly preferably, the first protective layer and the second protective layer. Both of the carbons in are derived from glassy carbon.

The ratio of the thickness of the first protective layer to the thickness of the second protective layer is preferably 1/1 to 5/1, but is not limited to this range. The total thickness of the first protective layer and the second protective layer is preferably 10 to 30 nm, but is not limited to this range.

In the present invention, either of the first protective layer and the second protective layer may be on top. That is, the first protective layer may be provided on the magnetic layer and the second protective layer may be provided on the first protective layer, or the second protective layer may be provided on the magnetic layer. You may provide the said 1st protective layer on it. However, it is preferable that the first protective layer formed mainly of carbon and silicon be the lower layer. As a further alternative, the first protective layer may be provided on the magnetic layer, the second protective layer may be provided thereon, and the first protective layer may be provided again thereon.

In the present invention, the lubricant layer provided on the protective layer is formed of a polymer obtained by gas phase polymerization. The method for forming the lubricant layer is not particularly limited, but the lubricant layer is preferably formed of a polymer obtained by vapor phase polymerization of a fluorocarbon compound and oxygen.

As the above-mentioned fluorocarbon compound, carbon-
Those having a carbon double bond are preferable, and particularly preferably selected from the group consisting of compounds represented by the following general formulas (I) to (III). CF ₂ = CFR _f ¹ ... (I) (In the formula, R _f ¹ is a fluorine atom, a perfluoroalkyl group, a perfluoroalkenyl group, a partially fluorinated alkyl group, a partially fluorinated alkenyl group, or perfluoroaryl. Group or a partially fluorinated aryl group) CF ₂ ═C (R _f ² ) (R _f ³ ) ... (II) (In the formula, R _f ² and R _f ³ are the same or different hydrogen atoms. , A fluorine atom, a perfluoroalkyl group, a perfluoroalkenyl group, a partially fluorinated alkyl group, a partially fluorinated alkenyl group, a perfluoroaryl group or a partially fluorinated aryl group) CF ₂ ═CFO (R _f ⁴ ) ... .. (III) (In the formula, R _f ⁴ is a fluorine atom, a perfluoroalkyl group, a perfluoroalkenyl group, a partially fluorinated alkyl group, a partially fluorinated alkenyl group, or perfluoroaryl. Group, a partially fluorinated aryl group or a perfluoroalkoxyalkyl group)

The above fluorocarbon compounds may be used alone or in admixture of two or more.
When two or more kinds are used, two or more kinds may be selected and used from any one of the general formulas (I) to (III), or among the general formulas (I) to (III). One or more types may be selected from at least two categories and used.

In the above general formula (I), preferable perfluoroalkyl groups are perfluoromethyl group (CF ₃ —) and perfluoroheptyl group (C ₅ F ₁₁ —).
And perfluorohexyl group (C ₆ F ₁₃ -) can be mentioned; Preferred perfluoroalkenyl group, perfluoro ethynyl group (CF ₂ = CF-) are exemplified; Preferred partially fluorinated alkyl group, 1H- perfluorobutyl group (C ₄ F ₈ H-) can be mentioned; preferred partially fluorinated alkenyl group, -CF ₂ -CF =
CH ₂ may be mentioned; a preferred perfluoroaryl group is a perfluorobenzyl group (—CF ₂ —C
₆ F ₅₎ can be mentioned; and Preferred partially fluorinated aryl group, -CFH-C ₆ F ₅ and -CF ₂ -
C ₆ H ₅ and the like.

Therefore, the compound of the general formula (I)
Of these, tetrafluoroethylene is preferable.
(CF₂= CF₂), Hexafluoropropene (CF₂=
CFCF₃), Perfluoroheptene-1 (CF₂= CF
C_FiveF₁₁), 6H-perfluorohexene-1 (CF₂
= CFC_FourF₈H), perfluorooctene-1 (CF
₂= CFC₆F₁₃), Hexafluoro-1,3-butadi
EN (CF₂= CF CF = CF₂), 3- (pentafluor
Rophenyl) pentafluoropropene-1 (CF₂= C
FCF₂C₆F_Five), CF₂= CFCHF-C₆F_Five, C
F₂= CFCF ₂-C₆H_Five, CF₂= CFCF₂CF
= CH₂Etc.

In the above general formula (II), preferred perfluoroalkyl groups include CF ₃ CF ₂ — in addition to those in the above general formula (I); preferred perfluoroalkenyl groups include the above general formula ( In addition to those in I), mention may be made of —CF ₂ —CF═CF ₂ ; preferred partially fluorinated alkyl groups are —CF ₂ H and —.
CF ₂ CF ₂ H is included; preferred partially fluorinated alkenyl groups include —CF═CH _{2 in} addition to those in the above general formula (I); and preferred perfluoroaryl groups and partially fluorinated aryl groups. as,
The same thing as the thing in the said General formula (I) is mentioned.

Therefore, the compound represented by the general formula (II)
Of these, CF is preferable. ₂= C (CF₃)₂,
CF₂= CH₂, CF₂= CHF, CF₂= CHC
F₃, CF₂= CHCF₂CF₃, CF₂= CHCF =
CF₂, CF₂= CHCF₂CF = CF₂, CF₂= C
HCF₂H, CF₂= CHCF₂CF₂H, CF₂= C
HCF₂CF = CH₂, CF₂= CHCF = CH₂, C
F₂= CHCFH-C₆F _Five, CF₂= CHCF₂-C
₆H_FiveEtc.

In the above general formula (III), preferable perfluoroalkyl groups and perfluoroalkenyl groups are the same as those in the above general formula (II); preferred partial fluorinated alkyl groups are:
CF ₂ H, —CF ₂ CF ₂ H and —C ₄ F ₈ H may be mentioned; preferred partially fluorinated alkenyl groups, perfluoroaryl groups and partially fluorinated aryl groups are those in the above general formula (II). like can be mentioned; and, as the preferred perfluoro alkoxyalkyl _{group, -CF 2 CF (CF 3)} OC 3 H 7 and the like.

Therefore, the compound represented by the general formula (III)
Of these, CF is preferable. ₂= CFOCF₃,
CF₂= CFOC_FiveF₁₁, CF₂= CFOC₆F₁₃, C
F₂= CFOCF₂CF₃, CF₂= CFOCF = CF
₂, CF₂= CFOCF₂CF = CF₂, CF₂= C_Four
F₈H, CF₂= CFOCF₂H, CF₂= CFOCF
₂CF₂H, CF₂= CFOCF₂-CF = CH₂, C
F₂= CFOCF = CH₂, CF₂= CFOCF₂-C
₆F_Five, CF₂= CFOCFH-C₆H_Five, CF₂= C
FOCF₂-C₆H_Five, CF₂= CFOCF₂CF (C
F₃) OC₃H ₇Etc.

The ratio of the fluorocarbon compound to oxygen used is such that the fluorocarbon compound / oxygen (molar ratio).
Is preferably 1 / 0.5 to 1/100, more preferably 1/1 to 1/10, and most preferably 1 /
It is 2-1 / 8. If the use ratio is lower than 1/100, the absorption efficiency of laser light or the like in the gas phase polymerization described below is lowered and the polymerization does not proceed sufficiently, and the use ratio is 1 /
When it is higher than 0.5, the amount of ether bond in the polymer is lowered and the durability property of the obtained lubricant layer is lowered, so that it is preferably within the above range.

The polymer obtained by gas phase polymerization of the above fluorocarbon compound and oxygen is mainly-(CF ₂ O)-.
The polymer having the structural unit of (1) and its molecular weight is preferably 1,500 to 30,000.

Although the structure of the above polymer is not always clear, for example, a polymer represented by the following structural formula is estimated. X- (CF ₂ O) _l- (CF ₂ CF ₂ CF ₂ O) _m- (CF (
CF ₃ ) CFO) _n X '[wherein l, m and n are positive integers (provided that
l >> m, l >> n), X and X ′ represent the same or different end portions containing alcohol, ether bond, ester bond, urethane bond or the like. ] Above in the polymer - (CF ₂ O) - the content of the structural units, is preferably at least 70% in the total structural units, for example, in polymer represented by the structural formula [l / It is preferable that (l + m + n)] × 100 is 70% or more.

The lubricant layer comprises a fixed layer fixed to the protective layer and a free layer formed on the fixed layer. Here, the fixed layer means a layer that is chemically or physically firmly fixed to the protective layer, and is washed off even if it is washed with a fluorine-based solvent such as a trade name “CFC 113”. It refers to the layer that does not exist. On the other hand, the free layer refers to a layer that is washed away when washed with the fluorine-based solvent.

The ratio of the thickness (weight) of the fixed layer to the thickness (weight) of the free layer is preferably (thickness of free layer) / (thickness of fixed layer). Is 1/10 to 10/1,
More preferably, it is 2/5 to 5/1.

The thickness of the fixing layer is preferably 5 to 30Å. When the thickness is less than 5Å, the wear resistance of the lubricant layer is insufficient and the durability is deteriorated. When the thickness exceeds 30Å, the structure of the fixed layer is disturbed and the wear resistance of the lubricant layer is deteriorated. Is decreased, so that it is preferably within the above range.

The thickness of the free layer is preferably 2 to 80Å. If the thickness is less than 2Å, the durability of the lubricant layer is insufficient, and if the thickness exceeds 80Å, the coefficient of friction of the lubricant layer increases, so it is preferable to set it within the above range.

As described above, in the magnetic recording medium of the present invention, the thickness of the free layer is set to the conventional free layer thickness (8
Even if it is thicker than 20 Å), the friction coefficient of the surface of the magnetic recording medium does not become high (it is difficult to adsorb),
The thickness of the free layer in the magnetic recording medium of the present invention is
It can be thicker than the thickness of the free layer in the conventional magnetic recording medium.

The thickness of the lubricant layer consisting of the fixed layer and the free layer is preferably 2 to 200Å, more preferably 10 to 100Å, further preferably 20 to 80Å,
Most preferably, it is 20 to 50Å. The thickness is 100
When it exceeds Å, the spacing loss becomes large, and when the thickness is less than 10 Å, the lubricating effect becomes poor, so that it is preferably within the above range.

In the magnetic recording medium of the present invention, an underlayer may be formed between the support and the magnetic layer. The underlayer can be provided by PVD such as sputtering using Cr, Ti, Al or alloys thereof. The thickness of the underlayer is preferably 10 to 100 nm.

Next, a preferred method for manufacturing the magnetic recording medium of the present invention will be described. A preferred method for producing a magnetic recording medium of the present invention is to form a first protective layer containing carbon and silicon as main components and a second protective layer containing carbon as main components,
At the time of forming the lubricant layer, gas phase polymerization is performed under a vacuum condition to polymerize the fluorocarbon compound and oxygen to form the lubricant layer, and after introducing steam. The second polymerization step in which vapor phase polymerization is performed under vacuum conditions to polymerize the fluorocarbon compound and oxygen to form the lubricant layer can be performed sequentially.

First, the formation of the protective layer will be described. As described above, the protective layer is obtained by forming the first protective layer containing carbon and silicon as the main components and the second protective layer containing carbon as the main component.

The formation of the first protective layer will be described. The method for forming the first protective layer is not particularly limited,
For example, the method described below can be appropriately selected.

(1) Chemical vapor deposition method in a mixed gas atmosphere containing methane, silane and the like. (2) A physical vapor deposition method (for example, vapor deposition, sputtering, ion beam sputtering, ion plating) using a carbon target containing silicon. (3) Reactive sputtering using a carbon target in a mixed gas atmosphere containing argon and silane.

Among the above methods (1) to (3), the preferred methods are (2) and (3).

As described above, the first protective layer preferably contains carbon derived from glassy carbon, but the carbon derived from glassy carbon is introduced into the first protective layer by a preferred method described below. can do.

Thin film forming means such as sputtering under an argon atmosphere, ion beam sputtering, vapor deposition or ion plating using glassy carbon containing silicon as a target or vapor deposition source. In this case, the silicon content in the target is preferably 0.1 to 50 atomic%.

As described above, it is preferable to form the first protective layer by sputtering using a target containing glassy carbon. The pressure in the chamber, which is a condition for sputtering, is preferably 2 to 15 mTorr. Particularly preferably, it is 2 to 10 mTorr.

Further, in this case, it is preferable to heat the support provided in the chamber, for example,
It is desirable to maintain the support at 25 to 300 ° C. In this way, sputtering is performed until the first protective layer having a desired thickness is formed.

Next, the formation of the second protective layer will be described. The method for forming the second protective layer is not particularly limited, and for example, the method described below can be appropriately selected.

(1) Chemical vapor deposition method in a gas atmosphere containing a carbon-containing compound such as methane. (2) A physical vapor deposition method using a carbon material target such as graphite (for example, vapor deposition, sputtering, ion beam sputtering, ion plating).

Of the methods (1) and (2) above, the preferred method is (2).

As described above, the second protective layer preferably contains carbon derived from glassy carbon, but carbon derived from glassy carbon is preferably an argon gas using glassy carbon as a target or a vapor deposition source. It is introduced into the second protective layer by a thin film forming means such as sputtering in an atmosphere, ion beam sputtering, vapor deposition or ion plating.

Thus, the second protective layer is preferably formed by sputtering using a target containing glassy carbon, and the pressure in the chamber, which is the condition for sputtering, is preferably 2 to 15 mTorr. Particularly preferably, it is 2 to 10 mTorr.

Further, in this case, it is preferable to heat the support provided in the chamber, for example,
It is desirable to maintain the support at 25 to 300 ° C. In this way, sputtering is performed until the second protective layer having a desired thickness is formed.

As described above, it is preferable to use the physical vapor deposition method using a target containing glassy carbon for forming the first protective layer or the second protective layer, and in particular, the first protective layer is used. It is preferable to use the physical vapor deposition method using a target containing glassy carbon for forming both the protective layer and the second protective layer.

In the physical vapor deposition method, in order to introduce carbon into the first protective layer and the second protective layer, it is preferable to use a carbon material as a target or an evaporation source as described above. . A crystalline carbon material such as graphite may be used as the carbon material, but it is particularly preferable to use glassy carbon as described above. Further, the carbon material is Si, Ti, W, Zr,
Carbide, nitride, etc. of Cr, Nb, Mo, Ta or Al,
It is also preferred to include particles of borides or oxides or ceramics such as BN or B ₄ C. The size of such particles is preferably 2 to 40 nm.

As described above, since either the first protective layer or the second protective layer may be above,
The order of formation can be appropriately selected depending on the purpose and the like.

Next, the formation of the lubricant layer will be described. In forming the lubricant layer, vapor phase polymerization is performed under vacuum conditions to polymerize the fluorocarbon compound and oxygen to form the lubricant layer, and steam is introduced. Then, vapor phase polymerization is performed under vacuum conditions, and the second polymerization step of polymerizing the fluorocarbon compound and oxygen to form the lubricant layer is sequentially performed.

Here, the first polymerization step is a step of mainly forming the fixed layer, and the second polymerization step is a step of mainly forming the free layer. That is, the free layer may be formed in the first polymerization step, and the fixed layer may be formed in the second polymerization step.

The gas phase polymerization carried out in the first and second polymerization steps will be described. The gas phase polymerization means a polymerization method in which the fluorocarbon compound and the oxygen are held in a gas phase in a gas state to carry out the polymerization to cause the polymerization reaction only in the gas phase. Examples of the method that can be used for the polymerization include CV such as plasma polymerization and photochemical vapor deposition (hereinafter referred to as “CVD”).
Although D can be adopted, in the present invention, photo-CVD is preferably adopted from the viewpoint that equipment and facilities are simple.

When polymerization is carried out by the above photo-CVD,
The surface of the deposit (that is, the surface of the protective layer) is not directly irradiated with the laser light, but is irradiated only in the mixed gas of the fluorocarbon compound and the oxygen.

Examples of the light source that can be used in the photo CVD include ultraviolet rays and infrared rays. Here, the reaction by an infrared laser using infrared light as a light source is basically a reaction by vibration excitation, and is essentially the same as a thermal reaction, and a side reaction occurs to generate a product other than the target product. In some cases, it may be difficult to control the structure of the lubricant layer formed. On the other hand, an ultraviolet laser using an ultraviolet ray as a light source causes a polymerization reaction by electronic excitation, has good selectivity in the reaction, and further, since the thermal reaction is extremely low in involvement, side reaction may occur. Low. Therefore, it is preferable to use ultraviolet rays as a light source used in the photo-CVD, and specifically, for example, excimer laser light of 193 nm can be preferably used.

The temperature of the deposit (that is, the magnetic recording medium provided with the protective layer and the magnetic layer) during the vapor phase polymerization is preferably set to 10 to 90 ° C., further 15 It is preferably -50 ° C. If the content is out of the above range, the lubricant layer may not be formed. Therefore, the content is preferably in the above range.

Next, the first and second polymerization steps described above will be described more specifically with reference to FIG. Here, FIG. 1 is a schematic diagram showing a photoreaction chamber that can be used when forming the lubricant layer.

The photoreaction chamber 1 shown in FIG. 1 is provided with a laser transmission window 2 for transmitting laser light, which is provided on both left and right side surfaces above it, and a magnetic disk 3 (which is a magnetic recording medium provided below). A medium setting member 4 on which the above-mentioned magnetic layer and the above-mentioned protective layer are provided on a support) can be erected at regular intervals, and decompression and atmospheric air inside the chamber provided above the chamber 1. And a valve 5 for performing the release.

In the first polymerization step, first, the valve 5 is connected to a vacuum pump (not shown), and the inside of the chamber 1 is temporarily depressurized to a vacuum (for example, 1 × 10 ^{−2). 5 to 1} Torr), and then the above-mentioned fluorocarbon compound and oxygen are introduced to obtain a vacuum condition described later. Next, excimer laser light or the like is irradiated in the direction of the arrow shown in FIG. 1 so as to pass through the center between the upper part of the magnetic disk 3 and the chamber ceiling and not hit the magnetic disk 3. The vacuum condition means a state in which the fluorocarbon compound and oxygen are introduced into the chamber 1 in a vacuum state, and the pressure in the chamber 1 in this state is 5 to 2
It is preferably set to 00 Torr. Further, in order to form the lubricant layer uniformly over the entire surface of the magnetic disk 3, the medium mounting member 4 can rotate each magnetic disk 3 in the circumferential direction. Has been done.

The above first polymerization step may be repeated several times.

Next, in the second polymerization step, after the completion of the first polymerization step, the valve 5 is opened to the atmosphere, and the vacuum condition in the first polymerization step is changed to the atmospheric pressure condition. After returning and introducing water vapor into the chamber 1, the pressure was reduced to a vacuum and then the fluorocarbon-based compound and oxygen were introduced to make the vacuum condition as in the first polymerization step. Irradiate with laser light. Here, the “vacuum condition” in the second polymerization step is the same as the “vacuum condition” in the first polymerization step.

In the present invention, the introduction of the water vapor is preferably carried out by introducing the atmosphere by setting the chamber 1 under the atmospheric pressure condition as described above. The relative humidity of the air introduced at this time is preferably 30 to 90%, more preferably 40 to 80%.

The above second polymerization step may also be repeated several times. The first polymerization step may be performed again after the second polymerization step.

The fluorocarbon compounds introduced into the chamber 1 in the first and second polymerization steps may be the same or different. Particularly, when the fluorocarbon compound used in the first polymerization step is a compound represented by the general formula (I), the fluorocarbon used in the second polymerization step is used. The system compound is also preferably a compound represented by the above general formula (I). Similarly, the fluorocarbon-based compound used in the first polymerization step is represented by the general formula (I
When the compound is represented by I) or (III), the fluorocarbon compound used in the second polymerization step is also a compound represented by the general formula (II) or (III), respectively. Is preferred. Most preferably, the fluorocarbon-based compounds used in the first and second polymerization steps are the same.

With respect to the steps other than the formation of the protective layer and the lubricant layer, the same method as a conventionally known method for producing a magnetic recording medium can be adopted without any particular limitation.

[0082]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited thereto.

[Example 1] Preparation of magnetic layer A disk support made of glassy carbon (size 1.8 inch, thickness 25 mil) having a density of 1.5 g / cm ³ was polished to obtain center line average roughness Ra. Was 1.0 nm. Then
Ar gas pressure 2 mTorr, temperature of the disk support 2
An Al-10 wt% Si alloy layer having a thickness of 20 nm is formed by DC magnetron sputtering at 60 ° C.,
A texture layer with Ra of 1.8 nm was obtained. Then A
Ar gas pressure 2mTo on the texture layer of 1-Si alloy
A first underlayer made of amorphous carbon having a thickness of 5 nm was provided by DC magnetron sputtering under the conditions of rr and the disk support temperature of 250 ° C. Further DC
A second underlayer made of Ti and having a thickness of 50 nm and a thickness of 50 nm in an Ar gas atmosphere by magnetron sputtering.
A third underlayer made of Cr (m) was provided, and a CoCrPt-based magnetic layer having a thickness of 40 nm was provided thereon. In addition, the above Ra (center line average roughness) is a stylus type roughness meter (TENCOR P
According to 2), it was measured under the following conditions.・ Stylus diameter: 0.6μm (needle curvature radius) ・ Stylus pressing pressure: 7mg ・ Measuring length: 250μm x 8 places ・ Trace speed: 2.5μm / sec ・ Cutoff: 1.25μm (low pass filter)

Preparation of First Protective Layer The above-mentioned disk support was placed in the chamber of an in-line type sputtering apparatus, and after the chamber was evacuated,
Ar (pressure: 2 mTorr) was introduced, and sputtering was performed by using glassy carbon containing silicon (ratio of silicon: 8 atomic%) described below as a target to include carbon and silicon in a thickness of 10 nm on the magnetic layer. A first protective layer (ratio of silicon: 8 atomic%) was provided. The disk support was maintained at 180 ° C. during sputtering.

Glassy carbon target containing silicon
Preparation of furfuryl alcohol (Kao Quaker Co., Ltd.) 10
5 parts by weight of 0.011N HCl aqueous solution was added to 00 parts by weight, reacted at 96 ° C. for 6 hours, and then dehydrated under reduced pressure to obtain a thermosetting resin. SiC having an average primary particle diameter of about 20 nm was added to this thermosetting resin, and the mixture was dispersed and mixed by a ball mill. To 100 parts by weight of the obtained furfuryl alcohol initial condensate resin, 1.5 parts by weight of a 70% by weight aqueous p-toluenesulfonic acid solution was added and sufficiently stirred. This was poured into a plate-shaped mold having a thickness of 4 mm and degassed under reduced pressure. Next, it was heated at 50 to 60 ° C. for 3 hours and further at 90 ° C. for 5 hours to obtain a plate-shaped composite cured resin. This composite cured resin was placed in a firing furnace, heated to 1200 ° C. at a heating rate of 10 ° C./hr in a nitrogen stream, held at this temperature for 2 hours, and then cooled to obtain a glassy carbon containing silicon. I got the material. This glassy carbon material was processed into a predetermined shape and used as a target.

Preparation of Second Protective Layer Subsequent to the preparation of the first protective layer, sputtering is carried out in an Ar atmosphere with graphite as the target to prepare the first protective layer.
A second protective layer having a thickness of 5 nm was provided on the protective layer. In addition, during sputtering, the disk support is placed 180
Maintained at 0 ° C.

Preparation of Lubricant Layer The disk supports on which the above-mentioned protective layer is formed are arranged in parallel as shown in FIG. 1 at a predetermined interval in the photoreaction chamber 1 shown in FIG. 1 which is a CVD apparatus. And chamber 1
After evacuating the inside to 5 × 10 ^-2 Torr, the partial pressure is 10To
hex hexafluoropropene (CF ₃ CF = CF ₂ )
And oxygen having a partial pressure of 60 Torr are introduced, and laser light (power of 1 nm) from the ArF excimer laser (wavelength 193 nm) is introduced.
The first polymerization step was performed once by irradiating 1500 pulses at 50 mJ and a repetition rate of 2 Hz for 12.5 minutes.

Next, the chamber 1 is leaked to remove humidity 6
Atmospheric pressure was introduced by introducing 0% air. After this, the chamber 1 was evacuated to 5 × 10 ^-2 Torr again, and then hexafluoropropene with a partial pressure of 10 Torr and oxygen with a partial pressure of 60 Torr were introduced to make the laser 1
The second polymerization step was performed once by irradiating 1500 pulses for 2.5 minutes. As a result, a thickness of 2 nm is formed on the protective layer.
Of the lubricant layer. Here, the laser was irradiated in the direction of the arrow shown in FIG. 1 so as not to directly irradiate the disk support. In the photo-CVD, the temperature of the disk support was room temperature (22 ° C).

In this way, the magnetic disk as the magnetic recording medium 10 shown in FIG. 2, that is, the support 11, the texture layer 16 provided on the support 11, and the texture layer 16 were provided. Underlayers 12a to 12c, magnetic layers 13 provided on the underlayers 12a to 12c, a protective layer 14 provided on the magnetic layer 13, and a lubricant layer 15 provided on the protective layer 14. And the lubricant layer 15 comprises
A magnetic disk comprising a fixed layer 15a having polymer molecules fixed to the surface of the protective layer 14 by chemical bonding and a free layer 15b formed on the fixed layer 15a was obtained.

The fact that the lubricant layer 15 is composed of the fixed layer 15a and the free layer 15b was confirmed by the following and. The above magnetic disk was ultrasonically cleaned with Freon 113 for 10 minutes and checked for weight change. After the above washing, ESCA (E manufactured by VG Science Co., Ltd.
SCALAB200C, using AlKα ray) was analyzed to confirm the presence or absence of residual molecules of the polymer on the surface of the magnetic disk. As a result, the fixed layer 15a had a thickness of 1.5 nm, and the free layer had a thickness of 0.5 nm.

The ESC of the lubricant layer 15 is also
According to the A analysis, a peak was observed around 294.7 eV for Cls, which is (CF) in a database prepared using a commercially available purple oropolyether lubricant.
₂ O) _n unit was in agreement with the Cls spectrum,
Lubricant molecules primarily - (CF ₂ O) _n - was found to be those having a structural unit. 292 and 289
Since a small peak is observed near eV,-(C
It is considered that a small amount of structural units other than the structural unit of F ₂ O) _n − also coexist.

Example 2 In the production of the first protective layer of Example 1, the following target of graphite containing silicon was used in place of the target of glassy carbon containing silicon, and the second protective layer was used. A magnetic disk was manufactured in the same manner as in Example 1, except that the glassy carbon target described below was used instead of the graphite target.

Preparation of Graphite Target Containing Silicon SiC powder and coke powder are mixed by a ball mill, the mixed powder is pressure-molded into a target, and the molded body is fired at about 2500 ° C. in an Ar atmosphere. A graphite target containing silicon was produced.

Preparation of glassy carbon target Furfuryl alcohol (manufactured by Kao Quaker Co., Ltd.) 10
After adding 5 parts by weight of 0.011N HCl aqueous solution to 00 parts by weight and reacting at 96 ° C. for 6 hours, B ₄ C particles having an average primary particle size of about 201 nm were added and dispersed and mixed by a ball mill. To 100 parts by weight of the obtained furfuryl alcohol initial condensate resin, 1.5 parts by weight of a 70% by weight aqueous p-toluenesulfonic acid solution was added and sufficiently stirred. This was poured into a plate-shaped mold having a thickness of 4 mm and degassed under reduced pressure. Next, it was heated at 50 to 60 ° C. for 3 hours and further at 90 ° C. for 5 hours to obtain a plate-shaped composite cured resin. This composite cured resin was placed in a firing furnace, heated to 1200 ° C. at a heating rate of 10 ° C./hr in a nitrogen stream, held at this temperature for 2 hours, and then cooled to obtain a glassy carbon material. . This glassy carbon material was processed into a predetermined shape and used as a target.

Example 3 Example 1 was repeated, except that the glassy carbon target used in Example 2 was used in place of the graphite target in the production of the second protective layer of Example 1.
A magnetic disk was manufactured by performing the same operation as in.

Comparative Example 1 A magnetic disk was manufactured in the same manner as in Example 1 except that the first protective layer of Example 1 was not manufactured.

[Comparative Example 2] A magnetic disk was produced in the same manner as in Example 1 except that the first protective layer of Example 2 was not produced.

Comparative Example 3 The first protective layer of Example 1 was not prepared, and instead of the graphite target in the preparation of the second protective layer, a graphite target containing silicon (ratio of silicon: A magnetic disk was manufactured by performing the same operation as in Example 1 except that 8 atomic%) was used.

[Comparative Example 4] The first protective layer of Example 2 was not produced, and instead of the glassy carbon target in the production of the second protective layer, a glassy carbon target containing silicon was used. A magnetic disk was produced in the same manner as in Example 1 except that (silicon content: 8 atomic%) was used.

Comparative Example 5 The same operation as in Example 1 except that the immersion method / plasma treatment method described below was used in place of the photo-CVD vapor phase polymerization in the preparation of the lubricant layer of Example 1. Then, a magnetic disk was manufactured.

Of the lubricant layer by the dipping method / plasma treatment method
The disk support on which the protective layer was formed was replaced with a perfluoropolyether lubricant (“Fomb” manufactured by Montecatini Co., Ltd.).
lin AM200l ”, trade name). After being taken out of the solution, the disk support was laid down in a box-shaped chamber in which a low pressure mercury lamp (150 W) was arranged, and the chamber was evacuated to 10T.
Ortho hexafluoroethane and 10 Torr fluorine were introduced, and further 3 Torr perfluoropropene was introduced. Continued ArF excimer laser (wavelength 193
nm) laser light (power 150 mJ, repetition rate 2 Hz) is condensed through a quartz lens and irradiated on the surface of the disk support, and induced destruction is performed for 5 minutes to perform radical treatment to obtain a lubricant layer. It was

Comparative Example 6 The same as Example 2 except that the immersion method / plasma treatment method in Comparative Example 5 was used in place of the photo-CVD vapor phase polymerization in the preparation of the lubricant layer of Example 2. The operation was performed to produce a magnetic disk.

Comparative Example 7 The same as Example 3 except that the immersion method / plasma treatment method in Comparative Example 5 was used in place of the photo-CVD vapor phase polymerization in the preparation of the lubricant layer of Example 3. The operation was performed to produce a magnetic disk.

[Comparative Example 8] In the production of the lubricant layer of Example 3, the CV described below was used instead of the photo-CVD vapor phase polymerization.
A magnetic disk was produced in the same manner as in Example 3 except that D surface polymerization was used. The thickness of the lubricant layer in this comparative example is 35Å, the fixed layer is 35Å, and the free layer is 0Å.
Was Å.

Preparation of Lubricant Layer by CVD Surface Polymerization A lubricant layer was prepared according to Example 1 described in JP-A-4-186524. That is, the disk support on which the magnetic layer and the protective layer are prepared is placed in a chamber,
After evacuation, a mixed gas of hexafluoropropene and oxygen (1: 1) was introduced at 100 Torr to cool the disk support to −20 ° C., and then an ArF excimer laser (wavelength: Laser light from 193 nm (power 150 mJ, repetition rate 2H
z) After irradiating 1500 pulses, while the chamber was evacuated, the disc support was returned to room temperature to remove a by-product, a low molecular weight fluorocarbon compound, from the disc support. In this way, a lubricant layer was formed on the protective layer.

[Performance Evaluation] Examples 1 to 3 and Comparative Examples 1 to 1
The CSS (contact start stop) test and the GHT (glide height) characteristic of the magnetic disk obtained in No. 8 were measured by the procedure described below. Table 1 shows the results.

CSS test Using an Al ₂ O ₃ .TiC slider head (weight: 3.5 g), a flying height of 2.8 micro inches and a magnetic disk rotation speed of 4500 rpm were driven for 5 seconds and stopped for 5 seconds. The number of times the coefficient of static friction exceeded 0.6 was measured.

GHT characteristics MG150T manufactured by PROQUIP was used, and a 50% slider head was used. S with a flying rate of 90% or more at a flying height of 1.3 micro inches, and a passing rate of 50-
A of 90%, B of 30% to 50%,
Those having a passage rate of 30% or less are indicated by C.

[0109]

[Table 1]

As is clear from the results shown in Table 1, the magnetic recording medium of the present invention is excellent in CSS characteristics even under the extremely severe glide height condition of 1.3 micro inches. That is, the magnetic recording medium of the present invention can reduce the spacing loss between the magnetic head and the magnetic layer, is excellent in electromagnetic conversion characteristics, and is also excellent in durability. . On the other hand, in Comparative Examples 1 to 4 in which the protective layer was formed by only one layer, it was found that the CSS characteristics were inferior to those in the above-mentioned Examples. The magnetic disks of Comparative Examples 5 to 7 further coated with a lubricant and then formed with a lubricant layer by plasma treatment and ultraviolet irradiation and the magnetic disk of Comparative Example 8 with a lubricant layer formed by CVD surface polymerization have CSS characteristics. However, it is found that is extremely inferior to the above-mentioned examples.

[0111]

The magnetic recording medium of the present invention has a low friction coefficient on the surface and excellent durability while satisfying the glide height characteristic. Further, according to the method of manufacturing the magnetic recording medium of the present invention, the magnetic recording medium of the present invention can be easily manufactured.

[Brief description of drawings]

FIG. 1 is a schematic view showing a photoreaction chamber as an example of a reaction container used in the method for producing a magnetic recording medium of the present invention.

FIG. 2 is a schematic sectional view showing an example of a magnetic recording medium of the present invention.

[Explanation of symbols]

 1 Chamber 2 Laser Transmission Window 3 Magnetic Disk 4 Medium Setting Member 5 Valve 10 Magnetic Recording Medium 11 Support 12 Underlayer 12a First Underlayer 12b Second Underlayer 12c Third Underlayer 13 Magnetic Layer 14 Protective Layer 15 Lubricant layer 15a Fixed layer 15b Free layer

Claims (9)

[Claims] 1. A magnetic recording comprising a support, a magnetic layer provided on the support, a protective layer provided on the magnetic layer, and a lubricant layer provided on the protective layer. In the medium, the protective layer includes a first protective layer formed mainly of carbon and silicon and a second protective layer formed mainly of carbon, and the lubricant layer is A magnetic recording medium comprising a fixed layer formed of a polymer obtained by gas phase polymerization and fixed on the protective layer, and a free layer formed on the fixed layer. 2. The magnetic recording medium according to claim 1, wherein the lubricant layer is formed by vapor phase polymerization of a fluorocarbon compound and oxygen. 3. The magnetic recording medium according to claim 2, wherein the fluorocarbon compound is selected from the group consisting of compounds represented by the following general formulas (I) to (III). CF ₂ = CFR _f ¹ ... (I) (In the formula, R _f ¹ is a fluorine atom, a perfluoroalkyl group, a perfluoroalkenyl group, a partially fluorinated alkyl group, a partially fluorinated alkenyl group, or perfluoroaryl. Group or a partially fluorinated aryl group) CF ₂ ═C (R _f ² ) (R _f ³ ) ... (II) (In the formula, R _f ² and R _f ³ are the same or different hydrogen atoms. , A fluorine atom, a perfluoroalkyl group, a perfluoroalkenyl group, a partially fluorinated alkyl group, a partially fluorinated alkenyl group, a perfluoroaryl group or a partially fluorinated aryl group) CF ₂ ═CFO (R _f ⁴ ) ... · (III) (In the formula, R _f ⁴ is a fluorine atom, a perfluoroalkyl group, a perfluoroalkenyl group, a partially fluorinated alkyl group, a partially fluorinated alkenyl group, a perfluoroaryl group, a moiety. Represents a fluorinated aryl group or a perfluoroalkoxyalkyl group) 4. The polymer is mainly-(CF ₂ O).
The magnetic recording medium according to claim 1, having a structural unit of-. 5. The magnetic recording medium according to claim 1, wherein carbon in the first protective layer and / or the second protective layer is derived from glassy carbon. 6. The method of manufacturing a magnetic recording medium according to claim 1, wherein a first protective layer containing carbon and silicon as main components and a second protective layer containing carbon as main components are formed, At the time of forming the lubricant layer, a gas phase polymerization is carried out under a vacuum condition to form a lubricant layer by polymerizing a fluorocarbon compound and oxygen, and a steam condition is introduced, followed by a vacuum condition. A method for producing a magnetic recording medium, characterized in that vapor phase polymerization is performed below to sequentially perform a second polymerization step of polymerizing a fluorocarbon compound and oxygen to form a lubricant layer. 7. The method according to claim 6, wherein the water vapor is introduced by returning the vacuum condition in the first polymerization step to an atmospheric pressure condition after the completion of the first polymerization step. A method for manufacturing the magnetic recording medium described. 8. The magnetic recording medium according to claim 6, wherein the fluorocarbon compound is selected from the group consisting of compounds represented by the following general formulas (I) to (III). Method. CF ₂ = CFR _f ¹ ... (I) (In the formula, R _f ¹ is a fluorine atom, a perfluoroalkyl group, a perfluoroalkenyl group, a partially fluorinated alkyl group, a partially fluorinated alkenyl group, or perfluoroaryl. Group or a partially fluorinated aryl group) CF ₂ ═C (R _f ² ) (R _f ³ ) ... (II) (In the formula, R _f ² and R _f ³ are the same or different hydrogen atoms. , Fluorine atom, perfluoroalkyl group, perfluoroalkenyl group, partially fluorinated alkyl group, partially fluorinated alkenyl group, perfluoroaryl group or partially fluorinated aryl group) CF ₂ ═CFO (R _f ⁴ ). · · (III) (wherein, R _f ⁴ is a fluorine atom, a perfluoroalkyl group, a perfluoro alkenyl group, a partially fluorinated alkyl group, a partially fluorinated alkenyl group, perfluoroaryl group Shows a partially fluorinated aryl group or a perfluoroalkoxy group) 9. The manufacturing method according to claim 6, wherein the first protective layer and / or the second protective layer are formed by a physical vapor deposition method using a target containing glassy carbon. .