JPH07235052A - Production of magnetic recording medium - Google Patents

Abstract

PURPOSE:To industrially advantageously obtain a magnetic recording medium with a lubricative layer more excellent in general purpose by unnecessitating the isolation and purification of a lubricative compd. as a metallic salt at the time of forming a lubricative layer contg. a host-guest complex type lubricant. CONSTITUTION:Each multidentate ligand 5 having function to take in a metallic ion and each lubricant molecule 7 contg. a metallic compd. and active hydrogen are stuck on the protective film 3 of a magnetic recording medium and a lubricative layer 4 is formed by producing a host-guest complex consisting of the multidentate ligand 5 as the host compd. and an anion of the lubricant molecule 7 bonded to the host compd. through a metallic ion 6 as the guest compd. The lubricative layer 4 is formed without previously isolating or purifying the lubricant molecule 7 as an alkali metallic salt.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a magnetic recording medium such as a thin film magnetic recording disk.

[0002]

2. Description of the Related Art A thin film magnetic recording medium, which is a typical example of a high recording density magnetic recording medium used in the information industry, is
Usually, it is manufactured by depositing a magnetic metal or its alloy on a non-magnetic substrate by plating, vapor deposition or sputtering. In actual use, the magnetic head and the magnetic recording medium come into contact with each other at high speed and slide, so that the magnetic head may be damaged by wear or the magnetic characteristics may be deteriorated.

As a method for solving such a drawback, it has been proposed to provide a protective film or a lubricating layer on the magnetic layer to reduce static / dynamic friction during contact sliding as much as possible and improve wear resistance. ing. A carbonaceous film, an oxide film, a nitride film, a boride film, or the like is used as the protective film. Liquid lubricants and solid lubricants are used as lubricants, and generally, a perfluoropolyether compound, which is a liquid lubricant, is applied to the disk surface.

[0004]

In recent years, a magnetic recording medium is required to have a low flying height of a head and a high speed of disk rotation in order to improve magnetic characteristics, and a medium substrate tends to be smoother. is there. It is very effective to provide a liquid lubricant film to reduce the dynamic friction coefficient, but as the liquid lubricant film is made thicker, a meniscus is formed between the head and the disk due to the surface tension of the liquid lubricant. It is known that the sticking phenomenon occurs. For this reason, it has been pointed out that the static friction coefficient increases, and the head is often inoperable while being stuck to the disk.

As the substrate is smoothed in order to reduce the flying height of the head, the liquid lubricant has a serious drawback that this adsorption phenomenon is very likely to occur, and the film thickness is reduced to prevent the adsorption. And there is a problem that sufficient durability cannot be obtained. In order to avoid these phenomena, a solid lubricant that does not form a meniscus is desired, and higher fatty acids and metal salts thereof have been proposed for some time.

However, since the solid lubricant is a stable phase in the solid state at room temperature, there is a problem that a part of the coating film is easily crystallized and agglomerated when applied on a disk.
Especially when the substrate is smoothed, the tendency of aggregation is remarkable. Due to the occurrence of agglomeration, the coating thickness becomes non-uniform, which increases the possibility of direct contact between the head and the disk, and may lead to head contamination and head instability.
In order to prevent the solid lubricant from aggregating and suppressing the spin-off, it is necessary to effectively bond and bond the lubricant molecules to the substrate.

As a method of fixing the molecules of the lubricating layer to the substrate, for example, a method of fixing a long chain alkyl group by a siloxane bond has been proposed (Japanese Patent Laid-Open No. 103721/1990).
No. 2, JP-A-2-103722). However, the methods of fixing the lubrication layer by covalent bonds such as these methods suppress the movement of molecules, and the lubricity is insufficient. This is because fixing the lubricant has a trade-off relationship with the lubricating performance.

As a fixing system, a reversible fixing method is ideal in which the lubricant molecules interact with the substrate with sufficient strength so as not to cause aggregation, and the fixing does not have a trade-off relationship with the lubricating performance. Target. The inventor
A host-guest complex type lubricating layer was found and applied as a lubricating system that can satisfy the above requirements (Japanese Patent Application No. 5-24).
8310, Japanese Patent Application No. 5-241472).

A lubricating layer containing a host-guest complex type lubricant is formed through a metal ion using a polydentate ligand having a function of taking in a metal ion as a host compound and a counter anion having a lubricating property as a guest compound. It is a thing. In the above proposal of the present inventor, when forming a lubricating layer containing a host-guest complex type lubricant, it was necessary to previously isolate and purify the lubricant compound as a guest compound as a metal salt. This isolation and purification requires a large amount of solvent and a lot of time, and the loss of the purified product cannot be avoided. Further, although there were some compounds that were difficult to isolate and purify, or were substantially unable to isolate and purify, the present inventor omits this step and is industrially advantageous. An object is to obtain a magnetic recording medium provided with.

[0010]

The present invention provides a multidentate ligand having a function of incorporating metal ions in a magnetic recording medium comprising a non-magnetic substrate on which a magnetic layer, a protective film and a lubricating layer are sequentially formed, A host guest in which a metal compound and a lubricant molecule having active hydrogen are attached to the surface of a protective film, a polydentate ligand is used as a host compound, and an anion of the lubricant molecule bonded to the host compound through a metal ion is used as a guest compound. The present invention relates to a method for manufacturing a magnetic recording medium in which a lubricating layer is formed by forming a complex. According to the present invention, a magnetic recording medium provided with a highly reliable lubricating layer for a long period of time can be obtained more easily, so that the flying height of the head can be reduced, and a disk system with an increased data recording density of the disk can be provided. It becomes possible to construct more easily.

The present invention will be described in more detail below. Figure 1
Shows a structure of a magnetic recording medium obtained by the manufacturing method of the present invention. In a magnetic recording medium in which a magnetic layer 2, a protective film 3, and a lubricating layer 4 are sequentially formed on a non-magnetic substrate 1, the lubricating layer 4 is composed of a host-guest complex type lubricant, and a lubricant compound is formed by a host compound adhered to a disk. Are fixed as guest compounds.

As the non-magnetic substrate, an aluminum alloy plate or a glass substrate on which a nickel / phosphorus layer is formed by an electroless plating method or a sputtering method is usually used, but a ceramics substrate, a resin substrate or the like can also be used. . The magnetic layer is, for example, cobalt or Co.
-Ni-Cr system, Co-Cr-Pt system, Co-Cr-T
It is a cobalt alloy such as a type, and is formed by a method such as an electroless plating method or a sputtering method after providing an undercoat layer on the non-magnetic substrate, if necessary. The film thickness of the magnetic layer is determined by the characteristics required for the magnetic recording medium, and is usually 100 to 1500Å, preferably 150 to 800Å. A carbonaceous film is preferable as the protective film, and a hydrogenated carbon protective film is particularly preferably used. The protective film is formed by a sputtering method, an ion plating method, a plasma polymerization method or the like, and the film thickness is usually 50 to 500.
Å, preferably 100-300 Å. Before forming the lubricating layer, the protective film may be subjected to an oxidation treatment or the like on its surface, if necessary.

The lubricating layer contains a host-guest complex type lubricant formed by using a multidentate ligand having a function of taking in metal ions as a host compound and a counter anion having a lubricating function as a guest compound through the metal ions. And is formed by separately using, as a raw material, a polydentate ligand having a function of incorporating a metal ion, a metal compound, and a lubricant molecule having active hydrogen.

FIG. 2 is a conceptual diagram showing the manner in which a host-guest complex formed by a derivative of 18-crown-6 and potassium stearate is fixed on the surface of a solid substrate. The cation K ⁺ in the guest compound is trapped in the inner hole of the crown ether, and the counter anion of K ⁺ , stearate, is transferred onto the crown ether with the terminal carboxyl group as an ion pair being trapped K ^+. Will be coordinated. Therefore, the alkyl chain portion of potassium stearate, which is a guest molecule, is oriented upward with respect to the substrate, and the orientation of the entire lubricating layer is improved.
Since the structure of the ideal lubricating layer is adopted, excellent lubricity and durability can be obtained even with a film thickness of almost a monomolecular layer.

For a review of the relationship between polydentate ligands and the metals incorporated therein, for example, representative crown ethers, cryptands and their analogs,
A detailed table of entrapped metals is given by JJ Christensen et al. In Chem. Revs., 74, 351 (1974). As the polydentate ligand, any compound having a function of effectively taking in a metal ion may be used, and a compound having three or more donor atoms is preferable. For example, as those having an oxygen atom and a nitrogen atom as donor atoms, cyclic esters, polyethers, polyols, polyamines, cyclic ethers collectively called crown ethers, cyclic ether amines generally called cryptands or cryptates, cyclic Examples thereof include amines, polypeptides, and chemically modified products thereof. Among them, cyclic ligands such as crown ethers and cryptands are particularly effective. Further, instead of the oxygen atom and the nitrogen atom in the above structure, a polydentate ligand having a sulfur atom similarly having a lone electron pair as a donor atom is also used.

As the metal compound, any compound capable of cation exchange between the active hydrogen (proton) at the terminal of the lubricant molecule and the metal ion may be used, and a compound soluble in water or an organic solvent is preferable. Examples thereof include salts such as alcoholates and phenolates, and preferred are alkali metal compounds such as hydroxides such as potassium hydroxide. The kind of metal may be appropriately selected depending on the size of the cavity of the polydentate ligand to be used, and an alkali metal such as potassium, an alkaline earth metal such as strontium, a transition metal such as silver or copper, and the like can be used. it can. For example, when 18-crown-6, which is a crown ether, is used as the polydentate ligand, potassium, barium or the like is suitable.

The counter anion may have a binding site for electrostatically interacting with the metal ion and a molecular skeleton responsible for the lubricating action. As the terminal functional group as a binding site, a carboxyl group, a phosphoric acid group, a sulfonic acid group, a hydroxyl group or the like can be used. The molecular skeleton following the binding site, for example, a branched or linear saturated or unsaturated higher aliphatic hydrocarbon chain, the higher aliphatic hydrocarbon chain containing an aromatic residue or a hetero atom, or the higher Any long-chain molecular skeleton in which a part or all of the aliphatic hydrocarbon chains form a polyether chain can be selected as long as it has a lubricating action regardless of the type of bond. It preferably has 8 or more carbon atoms, and more preferably 12 or more carbon atoms. Specifically, long-chain aliphatic carboxylic acids such as stearic acid, compounds containing a plurality of long-chain alkyls such as β- (N, N-diheptadecylaminocarbonyl) propionic acid, and phosphorus such as phosphoryl dioleyl ester. Acid long-chain aliphatic esters, dithiophosphoric acid long-chain aliphatic esters, or long-chain aliphatic sulfonic acids, long-chain aliphatic sulfates, long-chain aliphatic alcohols such as stearyl alcohol can be used. .

In the present invention, when forming a lubricating layer containing a host-guest complex type lubricant, a polydentate ligand having a function of taking in metal ions, a metal compound and a lubricant molecule having active hydrogen are individually provided. It is used as a raw material and applied on a solid substrate. The lubricating layer formed by such a method is
It exhibits the same performance as a lubricating layer formed by isolating and purifying a guest compound as a metal salt. The process of isolating and purifying the metal salt as the guest compound requires a large amount of solvent and a lot of time in the process of forming the lubricating layer. By omitting this isolation and purification step, it is very effective in terms of cost and time, and the problems associated with waste treatment of solvents, chemicals, etc. can be greatly reduced. Further, if there is a functional group capable of forming an ion pair with a metal ion, such as a carboxyl group, at the terminal of the lubricant molecule, a compound that is difficult to isolate and purify as a metal salt, or a compound that cannot be isolated and purified, It can be applied as a lubricant molecule of the host-guest complex type lubricating layer.

The host-guest complex type lubricating layer is prepared by dissolving a polydentate ligand having a function of taking in metal ions, a metal compound and a lubricant molecule having active hydrogen, individually or in appropriate combination, and dissolving them in a solvent to prepare a solution. It can be formed by preparing and coating on the surface of a solid substrate. When using an organic solvent as a solvent, for example, chloroform, halogenated hydrocarbons such as freon solvents, alcohols such as methanol and ethanol, ethers such as diethyl ether and tetrahydrofuran, acetone, ketones such as 2-hexanone, Aromatic hydrocarbons such as toluene and aliphatic hydrocarbons such as hexane are preferable. For example, in a system using 4,4′-diaminodibenzo-18-crown-6 as a polydentate ligand, potassium hydroxide as a metal compound, and stearic acid as a lubricant molecule, stearic acid and 4,4′-diamino are used. Dibenzo-18-crown-6
Were dissolved in chloroform or methanol, and potassium hydroxide was dissolved in methanol or water to prepare 4,4′-diaminodibenzo-18-crown-6 and potassium hydroxide. And a stearic acid mixed solution. In addition, when the solution is applied to a solid substrate, and when the three are used separately or in combination of two types to be dissolved in a solvent, the solution containing the polydentate ligand may be first applied to the solid substrate. preferable. When the lubricant molecule has a large molecular weight like a polymer, a dense lubricating film can be formed more reliably even when the molecular weight is relatively small.

As a method of applying the solution to a solid substrate,
Usually, it is carried out by immersing the solid substrate in the solution, but a method of forming a film by contacting the solid substrate surface with a tape or the like soaked with the solution under load, while rotating the pad on the solid substrate A method of attachment, a spray method, an LB film method or the like can be used. Although the concentration of the coating solution varies depending on the type of polydentate ligand, metal compound, lubricant molecule, and the type of solvent used, it is usually
Used as a concentration of total solutes in the solution of 0.1-5 g / l.

If the applied polydentate ligand layer is thicker than necessary, the excess polydentate ligand portion not directly fixed to the protective film may be rinsed with a suitable solvent. , Can be removed by subjecting it to physical treatment. Industrially, it is preferable to rinse the disk with the same solvent as the lubricant molecule solution. By removing the excess polydentate ligand portion, the film thickness of the entire lubricating layer becomes thinner, and the adhesive force between the lubricant molecule and the protective film through the polydentate ligand layer can be increased.

As a method of forming the lubricating layer, a method of attaching each compound onto a solid substrate by a dry process such as a vapor deposition method is also used. In this case, the polydentate ligand, the metal compound, and the lubricant molecule may be attached simultaneously or sequentially, and when they are attached sequentially, the metal compound is added to the polydentate ligand or the lubricant. There is also a method of forming the lubricating layer in two steps by introducing the molecules together in either process.

[0023]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to the following examples as long as the gist thereof is not exceeded. EXAMPLE 1 A chromium underlayer 2000Å, a cobalt alloy magnetic layer 400Å, and a carbon protective film 300Å were formed on a smooth aluminum alloy substrate by a sputtering method. Diameter 3.
A 5 inch magnetic disk was prepared by using a mixed solution of chloroform and methanol containing 4,4′-diaminodibenzo-18-crown-6, potassium hydroxide and stearic acid at a concentration of 1 mmol / l, respectively. A uniform lubricating layer having a thickness of 21 Å was formed by dipping.

A lubricity test and a cohesion test were conducted using a disk having a lubricating layer formed thereon. As a lubricity test, a thin film head AlTiC was used, a load of 9.5 gf, and a sliding linear velocity of 0.32 m / sec (radius 30 mm, 100 rpm).
The continuous sliding test was carried out, and the frictional force after 2 hours of continuous sliding was measured. As a cohesiveness test, temperature 25 ° C, humidity 40%
The disc was allowed to stand in the above environment, and the formation of aggregates and crystals was observed with an optical microscope. The results are shown in Table 1.

Example 2 Using the same disk as in Example 1, 4,4'-diaminodibenzo-18-crown-6, potassium hydroxide and β- (N, N-diheptadecylaminocarbonyl) propionic acid were added. A uniform lubricating layer having a thickness of 33Å was formed on the surface of the disk by a dipping method using a mixed solution of chloroform and methanol each containing at a concentration of 1 mmol / l. The lubricity test and the cohesiveness test were performed on the disc on which the lubrication layer was formed in the same manner as in Example 1. The results are shown in Table 1.

Example 3 Using the same disk as in Example 1, a chloroform solution containing 4,4'-diaminodibenzo-18-crown-6 at a concentration of 2 mmol / l was used to dip the disk surface. To form a uniform film with a thickness of 12Å, and then β-
(N, N-diheptadecylaminocarbonyl) propionic acid and potassium hydroxide were immersed in a mixed solution of chloroform and methanol containing each at a concentration of 1 mmol / l and then pulled up to give a uniform thickness of 33Å on the surface of the disk. A lubricating layer was formed. The lubricity test and the cohesiveness test were performed on the disc on which the lubrication layer was formed in the same manner as in Example 1. The results are shown in Table 1.

Example 4 Using the same disk as in Example 1, a chloroform solution containing 4,4'-diaminodibenzo-18-crown-6 at a concentration of 2 mmol / l was used to dip the surface of the disk. To form a uniform film having a thickness of 14Å, and then immersing it in a chloroform solution for 5 minutes, and then pulling up the disc at a speed of 2 mm / sec to leave a uniform film having a thickness of 8Å on the surface of the disc. Next, it was dipped in a mixed solution of chloroform and methanol containing β- (N, N-diheptadecylaminocarbonyl) propionic acid and potassium hydroxide at a concentration of 1 mmol / l, respectively, and then pulled up to obtain a thickness of 26Å. A uniform lubricating layer was formed. The lubricity test and the cohesiveness test were performed on the disc on which the lubrication layer was formed in the same manner as in Example 1. The results are shown in Table 1.

Comparative Example 1 Using the same disk as in Example 1, a mixed solution of chloroform and methanol containing 4,4'-diaminodibenzo-18-crown-6 and stearic acid at a concentration of 1 mmol / l, respectively. Was used to form a uniform lubricating layer having a thickness of 17Å on the surface of the disk by the dipping method. The lubricity test and the cohesiveness test were performed on the disc on which the lubrication layer was formed in the same manner as in Example 1. The results are shown in Table 1.

Comparative Example 2 Using the same disk as in Example 1, 1 mmol each of 4,4'-diaminodibenzo-18-crown-6 and β- (N, N-diheptadecylaminocarbonyl) propionic acid was prepared. Using a mixed solution of chloroform and methanol contained at a concentration of 1 / l, a uniform lubricating layer having a thickness of 31Å was formed on the surface of the disk by the dipping method. A lubricity test and a cohesiveness test were conducted in the same manner as in Example 1. The results are shown in Table 1.

Reference Example 1 Using the same disk as in Example 1, immersion was performed using a chloroform solution containing 4,4'-diaminodibenzo-18-crown-6 and potassium stearate at a concentration of 1 mmol / l. By the method, the thickness of the surface of the disc is 29
Å formed a uniform lubricating layer. A lubricity test and a cohesiveness test were conducted in the same manner as in Example 1. The results are shown in Table 1.

[0031]

[Table 1]

From the results of Examples 1 to 4, as in the case of Reference Example 1, the lubricant layer isolated and purified as the alkali metal salt was used as the guest compound to have the same excellent lubricity as the guest layer. It was confirmed that the aggregation of lubricant molecules was suppressed. That is, it can be seen that the use of the host-guest complex type lubricant does not cause a trade-off relationship between the adherence of the lubricant and the lubricating performance, and the lubricating layer has excellent lubricity and durability. Further, as in Comparative Examples 1 and 2, when the alkali metal is not present, the host-guest complex type lubricating layer is not formed, and therefore it is understood that the lubricant molecules are aggregated.

[0033]

EFFECTS OF THE INVENTION According to the present invention, a thin film (thickness of a monomolecular film) having excellent lubricity and wear resistance can be maintained for a long period of time without agglomeration of lubricant molecules. A magnetic recording medium provided with such a lubricating layer can be easily obtained by a general-purpose and simple method. Further, according to the forming method of the present invention, out of all the steps required to form the lubricating layer, one of the steps using a large amount of solvent can be excluded and the amount of chemical waste can be reduced. Extremely useful. A magnetic recording medium having a lubricating layer formed according to the present invention does not cause adsorption unlike liquid lubricants, especially when a smooth substrate corresponding to low flying height of a head is used, and is a very thin film. It is thick and has good lubricity and sufficient durability. Further, it is possible to obtain a magnetic recording medium having a high reliability for a long period of time, which is provided with a lubricating layer which does not have the problem of aggregation peculiar to solid lubricants.

[Brief description of drawings]

FIG. 1 is a conceptual cross-sectional view of a magnetic recording medium of the present invention.

FIG. 2 shows the constitution principle of the host-guest complex type lubricating layer of the magnetic recording medium of the present invention, for example, potassium stearate and 1
It is a conceptual diagram shown using the derivative of 8-crown-6.

[Explanation of symbols]

 1 non-magnetic substrate 2 magnetic layer 3 protective film 4 lubricating layer 5 polydentate ligand 6 metal ion 7 lubricant molecule

Claims (5)

[Claims] 1. A multidentate ligand having a function of taking in metal ions in a method of manufacturing a magnetic recording medium comprising a nonmagnetic substrate, a magnetic layer, a protective film and a lubricating layer sequentially formed on the nonmagnetic substrate,
A host guest in which a metal compound and a lubricant molecule having active hydrogen are attached to the surface of a protective film, a polydentate ligand is used as a host compound, and an anion of the lubricant molecule bonded to the host compound through a metal ion is used as a guest compound. A method for manufacturing a magnetic recording medium, characterized in that a lubricating layer is formed by forming a complex. 2. The method for producing a magnetic recording medium according to claim 1, wherein the lubricant molecule is a compound having an active hydrogen at one end and having 8 or more carbon atoms. 3. The method for producing a magnetic recording medium according to claim 1, wherein the polydentate ligand is a compound having 3 or more atoms of at least one kind of oxygen atom, nitrogen atom and sulfur atom. 4. The method for producing a magnetic recording medium according to claim 1, wherein the lubricating layer is formed by applying a mixed solution containing a polydentate ligand, a metal compound and a lubricant molecule having active hydrogen to the surface of the protective film. 5. The lubricating layer is formed by forming a polydentate ligand layer on the protective film and then binding the anion of a lubricant molecule to the polydentate ligand via a metal ion. Method for manufacturing the described magnetic recording medium