JPS63245492A - Lubricants and magnetic recording media using them - Google Patents

Abstract

PURPOSE:To provide a lubricant which is excellent in lubricity and less susceptible to dissipation when incorporated in a binder-contg. coating layer of a magnetic recording medium and exhibits a lubricating action for a long period of time, which comprises a polyfunctional org. isocyanate compd. and, bonded thereto, a particular fluorinated org. group. CONSTITUTION:A lubricant comprising as an active ingredient a lubricating compd. composed of a polyfunctional org. isocyanate compd. and, bonded thereto, an org. group. having a terminal perfluoroalkyl group through a urethane bond {e.g., a compd. of formula I [wherein X is a divalent or trivalent org. group comprising a residual group of a polyfunctional org. isocyanate compd.; R is a 2C or higher (substd.) alkylene; Rf is a 4-20C perfluoroalkyl; n is 1-21; and l is 2 or 3]}. Examples of the lubricating compd. include a compd. of formula II. These compd. is excellent in lubricity and less susceptible to dissipation when incorporated in a binder-contg. coating layer, such as a magnetic layer or a backcoat layer, of a magnetic recording medium and exhibits a lubricating action for a long period of time, so that it is possible to improve the durability of the magnetic recording medium.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a lubricant containing a fluorine-containing compound as an active ingredient, and a lubricant containing the lubricant in a magnetic layer and/or back coat layer, such as a magnetic disk or a magnetic tape. Related to magnetic recording media.

[Conventional technology]

Generally, in a magnetic recording medium formed by forming a magnetic layer containing magnetic powder and a binder on a non-magnetic support such as a polyester film, the surface of the magnetic layer comes into sliding contact with the magnetic head at a large relative speed during recording and reproduction. Easily causes performance deterioration and running problems due to abrasion of the magnetic layer.

Therefore, higher saturated fatty acids, fatty acid esters,
A lubricant such as silicone oil or fluorine oil is contained in the magnetic layer, or is applied to the surface of the magnetic layer by coating or transfer from other sources, and is applied to the sliding interface between the magnetic layer and the magnetic head during recording and reproduction. Measures have been adopted to improve durability and running performance by forming a lubricating film to reduce the coefficient of dynamic friction (unspecified literature).

[Problems to be Solved by the Invention] However, the above-mentioned conventional general-purpose lubricants generally have poor affinity for the binder of the magnetic layer, so when incorporated into the magnetic layer, excessive leaching to the surface occurs. Moreover, the lubricant that has leached out tends to easily separate from the surface of the magnetic layer and dissipate, resulting in the problem that the magnetic recording medium will deteriorate in performance or run poorly due to lack of lubricant in a relatively short period of time. Ta. The above-mentioned tendency is particularly remarkable in the case of fluorine oil, which has the greatest friction reduction effect among the lubricants, and its excellent lubricating performance cannot be fully utilized. On the other hand, in a structure in which a lubricant is deposited on the surface of the magnetic layer by coating, etc., even if the lubricant separates from the magnetic layer, it will not be newly leached from inside the magnetic layer and replenished, so the lubricating effect will continue. gender becomes even lower.

In view of the above-mentioned circumstances, this invention has excellent lubrication performance, and when incorporated into a coating layer containing a binder such as a magnetic layer or a back coat layer of a magnetic recording medium, it is difficult to dissipate and maintains a lubricating effect. The purpose of this invention is to provide a lubricant with high properties, thereby making it possible to significantly improve the durability of magnetic recording media.

[Means for solving problems]

As a result of intensive studies to achieve the above object, the inventors found that a fluorine-containing compound with a specific structure having at least two fluoroalkyl groups at the end of the molecule is equivalent to fluorine oil, a conventional lubricant. It has the above lubrication performance, and when it is blended into the magnetic layer or back coat layer, it does not cause excessive leaching unlike conventional general-purpose lubricants.
The present inventors have also discovered that it is difficult to separate from the layer surface, and therefore the above-mentioned excellent lubricating effect is stably exhibited over a long period of time, significantly improving the durability of the magnetic recording medium, leading to the present invention.

That is, the first aspect of the present invention relates to a lubricant containing as an active ingredient a lubricating compound formed by bonding an organic group having a terminal perfluoroalkyl group to a polyfunctional organic isocyanate compound via a urethane bond. Also, the second aspect of this invention
is a magnetic recording medium in which a magnetic layer and/or bank coat layer consisting of a coating layer containing a binder is formed on a non-magnetic support, in which a urethane bond is added to a polyfunctional organic isocyanate compound in the coating layer. The present invention relates to a magnetic recording medium characterized in that it contains a lubricant whose active ingredient is a lubricating compound formed by bonding an organic group having a terminal perfluoroalkyl group via a lubrication agent.

[Structure and operation of the invention]

The lubricating compound, which is an active ingredient of the lubricant of the present invention, is a polyfunctional organic isocyanate compound bound to an organic group having a terminal perfluoroalkyl group via a urethane bond, as described above, and has at least two Each of the molecular ends, that is, the number of ends corresponding to the number of isocyanate groups of the above-mentioned isocyanate compound, consists of a perfluoroalkyl group, and the molecular ends of this fluorocarbon chain exhibit an extremely excellent lubricating effect on the sliding interface. Provides low friction properties that are equal to or better than conventional fluorine oil lubricants. In addition, this compound has a bulky skeleton structure consisting mainly of hydrocarbons and urethane bonds in the middle part of the molecule. When blended into these layers, excessive leaching to the layer surface is suppressed and depletion of the lubricant within the layer is avoided, and separation from the layer surface due to sliding contact is prevented. In addition, lubricant leaches from the inside of the magnetic layer to the surface, albeit slowly, to compensate for the dissipated amount, and even if the layer surface is worn out due to a certain amount of use, the internal lubricant appears on the surface and provides lubrication. Since it forms a film, the above-mentioned excellent lubricating effect lasts for a long period of time.

Such lubricating compounds include those with various structures, but particularly preferred ones have the following general formula (
■); F(0 (wherein, 2
0 perfluoroalkyl group, n is an integer of 1 to 21, j
is an integer of 2 or 3). Further, in the above formula (1), those in which the perfluoroalkyl group of Rf has 6 to 18 carbon atoms have an excellent lubricating effect. In addition, one Rf and n R in the above (IJ formula) may be the same or different,
In particular, compounds in which one Rf is the same exhibit stable lubricity.

Here, specific examples of the ÷0R37 part in the above formula (I1) include ÷0CH2CH2 ÷0CH-CH2; OCHz CHz-H2C1 ÷OCH-CH2+; TOCH2CH, -CH3, and the like.

In order to synthesize such a lubricating compound, for example, a compound represented by H÷OR)n Rf (Rf, R, and n are the same as above) and a polyfunctional organic isocyanate compound are mixed for 1 mole of the latter. A suitable method is to heat the former to the number of moles corresponding to the number of isocyanate groups in the latter in a stream of dry nitrogen using toluene as a solvent and react for 2 to 3 hours. May be adopted.

As the above polyfunctional organic isocyanate, diisocyanate or triisocyanate is usually used. For example, as the diisocyanate, 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, 4,4-diphenyl diisocyanate, 4,4- diphenylmethane diisocyanate, metaphenylene diisocyanate, paraphenylene diisocyanate, 3.
3-dimethyl-4,4'-diphenylmethane diisocyanate, 2-chloro-1,4-phenyl diisocyanate, 3,3'-dimethoxy-4,4'-diphenyl diisocyanate, xylylene di-isocyanate, 1,5
- Naphthalene diisocyanate, hexamethylene diisocyanate, etc. are preferably used.

Further, as the above triisocyanate, R(+N G
A compound represented by O)3 (RC is a trivalent aromatic or aliphatic hydrocarbon group) may be used, but a triisocyanate compound produced by the following reaction between the diisocyanate and water described above is particularly suitable. That is, it is a triisocyanate compound produced by the reaction of 3.0CN-Y-NCO+H20 (Y is a divalent organic group).

The combination of the X component, R [component and ÷OR) component in the general formula (I) is selected depending on the purpose of use of the lubricant containing this as an active ingredient, that is, the magnetic layer of the magnetic recording medium or the back coat. When it is contained in the layers, it may be selected depending on the type and combination of binder components used in these layers.

The lubricant of the present invention as described above is particularly useful for magnetic recording media, but it can also be used for other lubricating applications. In addition to being included in the magnetic layer and/or back coat layer, it can also be coated on these layers, coated on the surface of a magnetic layer made of a ferromagnetic metal thin film such as a metal tape, and even coated on these surfaces during use. The lubricant of the present invention may be impregnated into the contacting member. However, due to its characteristic structure as described above, the lubricant of the present invention can be impregnated into a magnetic layer and/or a back coat layer consisting of a coating layer containing noise. In other words, by configuring the magnetic recording medium of the present invention, the effects of use are maximized.

In this way, when a lubricant containing the above-mentioned lubricating compound as an active ingredient is contained in the magnetic layer and/or back coat layer of a magnetic recording medium, the amount of the compound to be used is based on 100 parts by weight of the binder used in these layers. It is preferable to use 0.1 to 50 parts by weight, particularly preferably 0.2 to 20 parts by weight. If the amount is too large, the binding force of the binder will decrease, and if it is too small, the effect of use will be insufficient. Become.

In order to manufacture the magnetic recording medium of the present invention, it is sufficient to follow a conventional method. A magnetic paint containing magnetic powder, a binder, and the above-mentioned lubricant is prepared, and this paint is applied to one side of a non-magnetic support such as a polyester film. Alternatively, a magnetic layer may be formed by coating and drying on both sides, surface treatment such as calendering, and then punching or cutting into a desired size and shape. In addition, for those having a back coat layer, after or before forming the above magnetic layer or a magnetic layer consisting of a nonmagnetic metal thin film on the surface side, the required nonmagnetic powder and binder are added to the back side of the nonmagnetic support. A back coat layer may be formed by applying and drying a back coat paint containing a lubricant.

The binders used in the magnetic layer and bank coat layer include vinyl chloride-vinyl acetate copolymers, cellulose resins, polyurethane resins, acrylic resins, polyester resins, polyvinyl butyral resins, acrylonitrile-butadiene copolymers, etc. Examples include polymers, epoxy resins, phenol resins, and polyisocyanate compounds as crosslinking agents, and two or more of these can be used in combination.

As the magnetic powder, any of those conventionally known as recording elements of magnetic recording media can be used; for example, 7-F
e2O3, Fe3O4, intermediate oxide of the former two, Co-containing 7-Fe2O3, Co-containing Fe304, CrO
2. In addition to oxide magnetic powders such as Ba + Sr and Pb ferrite, Co s Fe SCr s Ni
Examples include metal magnetic powders such as alloys of these or alloys containing these and other metals or small amounts of nonmetallic elements.

Furthermore, additives conventionally known for magnetic coatings, such as abrasives, antistatic agents, dispersants, fillers, etc., can be appropriately blended into the above-mentioned magnetic coating composition as required.

Furthermore, a conventionally known lubricant may be included as long as the characteristics of the present invention are not impaired.

〔Effect of the invention〕

Since the lubricant of the present invention contains as an active ingredient a lubricating compound formed by bonding an organic group having a terminal perfluoroalkyl group to a polyfunctional organic isocyanate compound via a urethane bond, at least It exhibits an extremely excellent lubricating effect due to the action of the two perfluoroalkyl groups at the ends of the molecule, and moreover, the middle portion of the molecule exhibits strong affinity for the binder of the magnetic layer and back coat layer of a magnetic recording medium. Therefore, in the magnetic recording medium of the present invention containing this lubricant in the magnetic layer and/or back coat layer, excessive leaching of the lubricant to the layer surface is suppressed, and there is a risk that the lubricant will be depleted within the layer. The lubricant is not easily separated from the layer surface due to sliding contact, and a certain amount of the dissipated amount is replenished by slow leaching from inside the layer, and even when the layer surface is worn and renewed, the internal lubricant does not appear on the surface. Because it forms a lubricating film, the excellent lubrication effect on the surface of the layer is sustained over a long period of time, and it exhibits very good durability and running stability.

[Example 1] Hereinafter, the present invention will be specifically explained with reference to Examples. In addition, in the following, parts mean parts by weight. Further, the lubricating compounds used in each example are shown in Table 1 below.

Examples 1 to 16 3 parts of stearic acid n-butyl ester A magnetic paint was prepared by mixing and dispersing the above composition in a sand grinder mill, and this paint was dried on both sides of a 70/-" thick polyethylene terephthalate film, respectively. Apply so that the final thickness is 1.5μ.

After drying to form a magnetic layer and calendering, it was punched out into a 5-inch diameter circle to produce a floppy disk.

Comparative Example 1 Perfluoropolyether (trade name Fomblin Z- manufactured by Montegisson) was used in place of the lubricating compound listed in Table 1.
Floppy disks were produced in the same manner as in Examples 1 to 16, except that 3 parts of 25) were used.

Comparative Example 2 Silicone oil (
Floppy disks were produced in the same manner as in Examples 1 to 16, except that 3 parts of silicone oil F98 (trade name, manufactured by Shin-Etsu Chemical Co., Ltd.) were used.

The coefficient of friction of the surface of the magnetic layer was measured for the floppy disks of the above Examples and Comparative Examples.

In addition, these floppy disks are stored in special cartridges and recorded at 250 KH using a magnetic disk recorder.
After recording the z signal, the device was run in continuous rotation, and the number of runs until the playback output reached 50% of the initial output was measured, and this was taken as durability. These results are shown in the table below.

From the results shown in Table 2, the floppy disks of the present invention (Examples 1 to 16) using the lubricant of the present invention are superior to the floppy disks (Comparative Example 1) using fluorine oil, which is a conventional excellent lubricant. ), it is clear that the surface of the magnetic layer can provide stable running with the same or lower friction, and has significantly superior durability.

Claims (4)

[Claims] (1) A lubricant containing as an active ingredient a lubricating compound formed by bonding an organic group having a terminal perfluoroalkyl group to a polyfunctional organic isocyanate compound via a urethane bond. (2) The lubricating compound has the following general formula; ▲There are mathematical formulas, chemical formulas, tables, etc.▼ (In the formula, X is a divalent or trivalent organic group consisting of a residue of a polyfunctional organic isocyanate compound, and R is a Substituted or unsubstituted alkylene group having 2 or more carbon atoms, R_f has 4 to 4 carbon atoms
20 perfluoroalkyl groups, n is an integer of 1 to 21,
The lubricant according to claim 1, which is a fluorine-containing compound represented by the formula (l is an integer of 2 or 3). (3) In a magnetic recording medium in which a magnetic layer and/or a back coat layer consisting of a coating layer containing a binder is formed on a non-magnetic support, a urethane bond is bonded to a polyfunctional organic isocyanate compound in the coating layer. 1. A magnetic recording medium comprising a lubricant whose active ingredient is a lubricating compound formed by bonding an organic group having a terminal perfluoroalkyl group via a lubrication agent. (4) The lubricating compound has the following general formula; ▲There are mathematical formulas, chemical formulas, tables, etc.▼ (In the formula, X is a divalent or trivalent organic group consisting of a residue of a polyfunctional organic isocyanate compound, and R is a Substituted or unsubstituted alkylene group having 2 or more carbon atoms, R_f has 4 to 4 carbon atoms
20 perfluoroalkyl groups, n is an integer of 1 to 20,
The magnetic recording medium according to claim (3), which is a fluorine-containing compound represented by: (1 is an integer of 2 or 3).