JPH03702B2 - - Google Patents

Description

[Detailed description of the invention]

(Field of Industrial Application) 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 at high temperatures. (Prior Art) It is known to include a lubricant in a magnetic layer for the purpose of increasing the durability of magnetic recording media such as video tapes and floppy disks. As such lubricants, silicone oil, fluorine oil, long chain fatty acid ester, hydrocarbon compound, long chain fatty acid, long chain fatty acid amide, etc. are known. 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, even one bit does not change. A high degree of durability is required to prevent dropouts. As floppy disks become more common, the devices can be used at temperatures as low as 10 degrees Celsius or below, or as high as 40 degrees Celsius or higher. On the other hand, the devices themselves are becoming thinner and smaller, and the temperature inside the devices is increasing due to heat generation from heating elements such as motors. Against this background, the level of durability required of floppy disk media has become even more severe, and in particular, significant improvements in durability under high temperatures are desired. Conventionally, long-chain fatty acid esters, particularly monofunctional long-chain fatty acid esters, have been frequently used as lubricants for the purpose of increasing durability, and for example, butyl stearate, butoxyethyl stearate, and the like are well known. A floppy disk using such a lubricant exhibits almost good durability when used at room temperature, but there is a serious problem in durability when used in a high-temperature atmosphere. Therefore, the present inventors investigated a lubricant with good lubricity and high temperature durability, and arrived at the present invention. (Structure and operation of the invention) The present invention provides a magnetic recording medium in which a magnetic layer containing magnetic powder, a binder, and a lubricant is formed on a base material, wherein the lubricant is a fatty acid ester represented by the following formula (). A magnetic recording medium characterized by comprising: However, R ₁ is an aliphatic group having 8 to 22 carbon atoms, R ₂ is an aliphatic group having 1 to 12 carbon atoms, R ₃ and R ₄ are H or CH ₃ n is an integer of 2 or more. In order to improve the high-temperature durability of magnetic recording media in which the magnetic layer is formed using at least one type of binder such as epoxy-based or epoxy-based binders, a novel lubricant containing fatty acid ester is dispersed in the magnetic paint that forms the magnetic layer. The magnetic layer may be contained by overcoating the surface of the magnetic layer. The fatty acid ester used as the lubricant of the present invention refers to the ester represented by the above formula (), and specifically, for example, diethylene glycol monobutyl ether stearate, diethylene glycol monobutyl ether oleate, diethylene glycol monobutyl ether palmitate,
Examples include diethylene glycol monobutyl ether laurate, diethylene glycol monoethyl ether stearate, diethylene glycol monophenyl ether stearate, triethylene glycol methyl ether palmitate, and dipropylene glycol monoethyl ether oleate. These include alcohols such as polyethylene glycol monoalkyl ethers represented by diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monopropyl ether, diethylene glycol monobutyl ether, etc., polypropylene glycol monoalkyl ethers represented by dipropylene glycol monomethyl ether, etc., and laurin. It can be synthesized by the reaction of long-chain carboxylic acids such as myristic acid, palmitic acid, stearic acid, isostearic acid, oleic acid, and linoleic acid. These fatty acid ester lubricants may be used alone or in combination with conventional lubricants. In all lubricant components when used in combination.
The content is preferably 15% or more, more preferably 30% or more. The amount of this lubricant added is 0.1 to 15% by weight, preferably 0.5 to 10% by weight, based on the total weight of the magnetic layer. If the amount added is less than 0.1%, the lubricant will not be effective in terms of durability, and if it exceeds 15%, there will be too much lubricant, which may cause problems such as softening of the coating film, resulting in poor durability. This is because it decreases. In the present invention, the binder is preferably composed of at least one of urethane-based, vinyl chloride-based, and epoxy-based components, but is not limited thereto. In addition to magnetic powder, conventionally known additives such as dispersants (lecithin, etc.), antistatic agents (carbon, etc.), reinforcing agents (α-Fe ₂ O ₃ , alumina, etc.) may be added. good. (Example) Next, an example of the present invention will be described. In addition, in the following Examples and Comparative Examples, all "parts" indicate "parts by weight." Example 1 70 parts of γ-Fe ₂ O ₃ A magnetic recording binder made of a polyurethane elastomer, a salt-vinyl acetate copolymer having a hydroxyl group, and an epoxy resin 17 Carbon black 5 Dispersant 2 Crosslinking agent made of polyisocyanate 2 〃 Tetrahydrofuran/cyclohexanone mixed solvent 180 〃 Lubricant diethylene glycol monobutyl ether stearate 4 〃 After mixing and dispersing the above composition, it was applied to a 75 μm polyester film substrate so that the dry thickness was about 3 μm, and after drying, the surface The material was calendered, cross-linked by heating, and punched out into a disk shape to obtain a floppy disk. Example 2 A floppy disk was obtained in the same manner as in Example 1 except that 5 parts of diethylene glycol monobutyl ether oleate was used instead of diethylene glycol monobutyl ether stearate. Example 3 A flask was prepared in the same manner as in Example 1 except that a mixture of 2.2 parts of diethylene glycol monoethyl ether stearate and 2.2 parts of diethylene glycol monoethyl ether palmitate was used instead of diethylene glycol monobutyl ether stearate as the lubricant in Example 1. Got a tupee disk. Example 4 A floppy disk was prepared in the same manner as in Example 1 except that, instead of diethylene glycol monobutyl ether stearate, a mixture of 3 parts of diethylene glycol monobutyl ether stearate and 1 part of olive oil was used as the lubricant in Example 1. I got it. Example 5 A floppy tube was prepared in the same manner as in Example 1 except that instead of diethylene glycol monobutyl ether stearate as the lubricant in Example 1, a mixture of 1 part of diethylene glycol monobutyl ether oleate and 1 part of trimethylolpropane tridecanoate was used. I got a disk. Comparative Example A floppy disk was obtained in the same manner as in Example 1 except that the lubricant diethylene glycol monobutyl ether stearate was replaced with that shown in Table 1.

[Table] The durability of these floppy disks was evaluated using an 8-inch commercially available floppy disk device. A head load was performed with a head tension of 30 g, the same track was rotated continuously, and the durability time was defined as the time during which the output level became 80% or less of the initial value. Note that the head tension of a typical floppy disk device is 10 to 20 g, and this method can be said to be quite strict as a condition for evaluating the durability of a floppy disk. The durability measurement temperature was 50°C. Classified into the following three ranks based on durability time. Durability rank A: Durability time 250 hours B: 150 to 250 hours C: 150 hours or less Table 2 shows the evaluation results of the durability of the floppy disks of the above Examples and Comparative Examples.

[Table] Example 6 A magnetic paint was prepared using 70 parts of cobalt iron oxide instead of 70 parts of γ-Fe ₂ O ₃ in Example 1.
m thick polyester film substrate with dry thickness of approx.
The film was coated to a thickness of 4.5 μm, and after drying, the surface was calendered, cross-linked by heating, and slit into 1/2 inch width to obtain a videotape. Comparative Example 7 A videotape was obtained in the same manner as in Example 6 except that a lubricant consisting of 4 parts of butyl stearate was used instead of diethylene glycol monobutyl ether stearate. Regarding the video tapes of Example 6 and Comparative Example 7,
40℃ according to the Japan Electronics Industry Association standard VHS standard method
Table 3 shows the results of evaluating the still characteristics in the atmosphere.

[Table] (Effects of the Invention) As mentioned above, the magnetic recording medium of the present invention has improved durability, especially durability at high temperatures, and the reason for this is that the lubricant used in the present invention has a moderate affinity with the polymer binder. This is thought to be due to the fact that a good lubricating film is formed at the interface between the head and the magnetic layer even in a high-temperature atmosphere. Furthermore, the lubricant of the present invention has lower volatilization than conventional lubricants, and the fact that the amount of loss in the lubricant in a high-temperature atmosphere is small also contributes to improved durability. In addition, in the present invention, the stability of the magnetic paint forming the magnetic layer is improved, resulting in a paint with good dispersion, so the separation phenomenon of the magnetic paint is less likely to occur, the quality of the magnetic layer is improved, and the product yield is increased. When improved, it can also bring about other effects.

Claims (1)

[Scope of 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, wherein the lubricant contains a fatty acid ester represented by the general formula (). A magnetic recording medium characterized by: However, R ₁ is an aliphatic group having 8 to 22 carbon atoms R ₂ is an aliphatic group having 1 to 12 carbon atoms R ₃ and R ₄ are H or CH ₃ n is an integer of 2 or more.