JPH0334129B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a magnetic recording medium in which a magnetic layer is formed on a base material, and particularly to a magnetic recording medium with improved durability over a wide temperature range from low to high temperatures. [Prior Art] It is known that a lubricant is contained in a magnetic layer in order to improve the durability of magnetic recording media such as video tapes and floppy disks. Conventionally, silicone oil, fluorine oil, long chain fatty acid ester, hydrocarbon compound, long chain fatty acid, long chain fatty acid amide, etc. have been used as such lubricants. By the way, in recent years, it has become important to improve the reliability of magnetic recording media, and especially in digital recording such as floppy disks, the reliability of each bit is important, and even after long-term use, dropout of even a single bit has become a problem. A high degree of durability is required to prevent damage. As floppy disks have become more common, devices have become
It may be used under conditions such as high temperatures of ℃ or higher (for example, in an atmosphere of 50℃). Against this background, the level of durability required of floppy disks has become even more stringent.
It is desired to improve durability from low to high temperatures. In the prior art, long chain fatty acid esters, particularly monofunctional long chain fatty acid esters, are often used as lubricants for the purpose of increasing durability. For example, butyl stearate, butoxyethyl stearate, etc. are used, but although floppy discs using such long-chain fatty acid esters generally show good durability when used at room temperature, they have problems with durability in high-temperature atmospheres. There is. Also, 2-hexyldecyl behenate, 2-hexyldodecyl stearate, 2-octyldodecyl stearate,
Esters such as 2-hexyldecyl stearate have relatively good durability under high-temperature atmospheres, but they cannot be used with magnetic paints made by adding urethane binders, carbon black, lecithin, α-Fe ₂ O ₃ , etc. to magnetic powder. There is a problem with the compatibility of [Purpose of the Invention] The present inventor has developed a lubricant with excellent lubricity, a wide applicable temperature range, good durability, and good compatibility with magnetic paint, and found that We have obtained completely new knowledge regarding this, and have arrived at the present invention. Therefore, an object of the present invention is to provide a magnetic recording medium with improved durability over a wide temperature range from low to high temperatures. [Structure of the Invention] Basically, the object of the present invention is to provide a magnetic recording medium in which a magnetic layer containing magnetic powder, a binder, and a lubricant is formed on a base material, in which the lubricant has a carbon number of 12 to 12. 16 carboxylic acids and general formulas

[Formula] (However, R ₁ is an aliphatic group having 5 to 10 carbon atoms,
R ₂ is an aliphatic group having 1 to 7 carbon atoms. ) and the general formula (However, R ₃ is an aliphatic group having 8 to 22 carbon atoms,
R ₄ is an aliphatic group having 1 to 12 carbon atoms, R ₅ and R ₆
are H or CH ₃ -, respectively. Further, n is an integer of 1 or more. ) This is achieved by a magnetic recording medium characterized by containing at least an ester B represented by: The lubricant used in the present invention has 12 to 16 carbon atoms.
Carboxylic acid and general formula of

[Formula] (However, R ₁ is an aliphatic group having 5 to 10 carbon atoms,
R ₂ is an aliphatic group having 1 to 7 carbon atoms) It is necessary to contain an ester A with an alcohol as at least one component. The carbon number is 12 to 16
Preferred examples of the carboxylic acid include lauric acid, myristic acid, and palmitic acid.
Examples of the alcohol include 2-ethylhexyl alcohol, 2-pentylnonyl alcohol, 2-hexyldecyl alcohol, 2-pentylnonyl alcohol, 2-butylundecyl alcohol, 2-heptyldodecyl alcohol,
-hexyldodecyl alcohol and the like can be preferably mentioned. Preferred specific examples of the ester A include 2-hexyldecyl palmitate,
Examples include 2-hexylnonyl palmitate and 2-hexyldodecyl myristate. Such ester A is used in combination with another lubricious ester B. This lubricating ester has the general formula

〔Example〕

Next, examples of the present invention will be described. In addition, in the following examples and comparative examples, all "parts" indicate "weight." Example 1 70 parts of γ-Fe ₂ O ₃ Magnetic recording binder made of polyurethane elastomer, salt-vinyl acetate copolymer having hydroxyl groups, and epoxy resin 17 Carbon black 5 Dispersant 2 Crosslinking agent made of polyisocyanate 2 〃Tetrahydrofuran/cyclohexanone mixed solvent
180 parts Lubricant: 2-hexyldecyl palmitate 2.5
1.5 parts diethylene glycol monobutyl ether stearate The above composition is mixed and dispersed to prepare a magnetic paint. A portion of the mixture was placed in a container with a seal and allowed to stand at 25°C for 24 hours. Dry the remaining magnetic paint using a 75μm polyethylene terephthalate film as a base.
It was coated on both sides to a thickness of approximately 3 μm, and after drying, the surface was calendered, cross-linked by heating, and punched out into a disk shape to obtain a floppy disk. Example 2 In place of 2.5 parts of 2-hexyldecyl palmitate and 1.5 parts of diethylene glycol monobutyl ether stearate as lubricants in Example 1, 2 parts of 2-hexyldecyl palmitate, 1 part of diethylene glycol monoethyl ether stearate, and ester were used. A floppy disk was obtained in the same manner as in Example 1 except that part X1 was used. Here, ester X is a polyfunctional ester obtained by reacting a mixed acid consisting of 1 mole each of caprylic acid, capric acid, and lauric acid with 1 mole of trimethylolpropane. Example 3 In Example 1, 2.5 parts of 2-hexylnonyl palmitate and dipropylene glycol monobutyl ether stearate were used instead of 2-hexyldecyl palmitate and diethylene glycol monobutyl ether stearate as lubricants.
A floppy disk was obtained in the same manner as in Example 1 except that 1.5 parts were used. Example 4 In Example 1, 2 parts of isotridecyl myristate, 1 part of diethylene glycol monobutyl ether oleate, and 1 part of glycerin tricaprylate are used instead of 2-hexyldecyl palmitate and diethylene glycol monobutyl ether stearate as lubricants. A floppy disk was obtained in the same manner as in Example 1 except for this. Example 5 A floppy disc was obtained under the same conditions as in Example 1 except that the amounts of 2-hexyldecyl palmitate and diethylene glycol monobutyl ether stearate as lubricants were changed to 1.0 part each. Comparative Examples 1 to 8 Floppy disks were obtained in the same manner as in Example 1, except that the lubricants in Table 1 were used instead of 2-hexyldecyl palmitate and diethylene glycol monobutyl ether stearate. .

[Table] The magnetic paints of each Example and Comparative Example prepared in this way were placed in a glass container with a tightly closed stopper and allowed to stand at 25°C for 24 hours. Evaluation was made from three points of view: (2) Is there any layer separation? (2) Is the carbon separated and does it stand out on the surface? (3) Is the lubricant separated and does it stand out on the surface? The evaluation was divided into the following three ranks. (1) No change from immediately after preparation →〇(2) A slight black striped pattern of carbon is observed on the surface. →△ (3) Separated liquid layers are observed on the surface. Also, the entire surface is covered with separated carbon. →× The results are shown in Table 2. Furthermore, the durability of the floppy disks of the Examples and Comparative Examples manufactured in this way was evaluated as follows using an 8-inch commercially available floppy disk device. Perform a head load with a head tension of 30g,
The durability time of the medium was defined as the time when the output level became 80% or less of the initial value when the same track was rotated continuously. Note that the head tension of a typical floppy disk device is 10 to 20 g, and the 30 g head tension used in this method can be said to be quite severe. Also, the ambient temperature is 0℃ (low temperature).
The temperature is 50℃ (high temperature). Durability was indicated by the durability time in the above test. The durability evaluation results obtained in the above examples and comparative examples are shown in Tables 3 and 4.

【table】

【table】

〔Effect of the invention〕

The magnetic recording medium of the present invention has improved durability over a wide range of temperatures from low temperatures to high temperatures, and is particularly excellent in durability at low temperatures. The reason for this is that the lubricant used in the present invention has a moderate affinity with the polymer binder and has the ability to maintain its fluidity even at low temperatures, which creates a good lubricant film on the interface between the head and the magnetic layer. This is thought to be due to the formation of Furthermore, the general formula

By adding the ester of [Formula], monofunctional fatty acid ester, and mixed acid polyfunctional ester, the lubricity of the interface between the head and the magnetic layer at high temperatures is improved for the same reason, and durability is achieved over a wide range of temperatures. It has good elasticity and slipperiness.

Claims (1)

[Claims] 1. A magnetic recording medium in which a magnetic layer containing magnetic powder, a binder, and a lubricant is formed on a base material,
The lubricant is a carboxylic acid having 12 to 16 carbon atoms and the general formula [Formula] (wherein R ₁ is an aliphatic group having 5 to 10 carbon atoms,
R ₂ is an aliphatic group having 1 to 7 carbon atoms. ) and the general formula (However, R ₃ is an aliphatic group having 8 to 22 carbon atoms,
R ₄ is an aliphatic group having 1 to 12 carbon atoms, R ₅ and R ₆
are H or CH ₃ -, respectively. Further, n is an integer of 1 or more. ) A magnetic recording medium comprising at least an ester B represented by: 2. The magnetic recording medium according to claim 1, wherein the content of the ester A and the ester B as lubricants is in the range of 0.3 to 12% by weight of the magnetic layer. 3 In the magnetic layer, as a lubricant, a mixed fatty acid component of two or more of the above ester A and ester B and a fatty acid having 8 to 18 carbon atoms and 3 or 4 fatty acids in the molecule.
2. The magnetic recording medium according to claim 1, which contains ester C obtained by reaction with a polyhydric alcohol component having hydroxyl groups. 4 The above ester A and ester B as lubricants
and ester C content of the magnetic layer is 0.3.
4. A magnetic recording medium according to claim 3, wherein the amount is in the range of 12% by weight.