JPS598129A - Flexible magnetic disk - Google Patents

Abstract

PURPOSE:To improve the wear resistance and to prevent the bleeding of a lubricant by using a specified urethane prepolymer and a specified vinyl copolymer as constituents of a binder in the magnetic layer and by incorporating a specified lubricant. CONSTITUTION:The urethane prepolymer has superior wear resistance and improves the dispersibility of magnetic powder, yet when the mol. wt. is <20,000, the wear resistance is deteriorated. When the mol. wt. is >100,000, the dispersibility of the magnetic powder is deteriorated. The vinyl copolymer has hydroxyl groups in the molecule, and the average mol. wt. is 10,000-30,000. The copolymer improves the dispersibility of the magnetic powder, and since the copolymer has OH groups, it causes a cross-linking reaction with polyisocyanate and is useful to improve the wear and heat resistances. In case of <10,000mol. wt., the strength of a coated film is deteriorated, and in case of >30,000mol. wt., the solubility in a solvent is deteriorated.

Description

[Detailed Description of the Invention] The present invention relates to a flexible magnetic disk (hereinafter simply referred to as a disk) that is rotatably housed in a jacket, and its purpose is to improve the wear resistance of the magnetic layer. The objective is to provide a disc with excellent durability.

In general, disks are used for recording and reproducing by rotating at high speed while in sliding contact with a magnetic head, and are also subjected to severe use such as head seeking and head tapping, so the magnetic layer is much more difficult than that of conventional magnetic tape. A high degree of wear resistance is required. Another important problem with disks, which are different from magnetic tapes, is that the disk surface comes into contact with a liner made of rayon or polyester fibers welded to the inner surface of the jacket so that it is constantly cleaned during rotation, and the lubricating components of the magnetic layer are Over time, the magnetic layer oozes out onto the surface and is absorbed into the liner, preventing its lubrication function from being maintained over a long period of time.As the magnetic layer rotates at high speed in sliding contact not only with the head but also with the liner, the magnetic layer is extremely prone to wear and tear. This has the drawback of easily causing dropout and a decrease in output.

On the other hand, as a characteristic of the disk, it handles digital information processing, so compared to a magnetic boop that processes analog information,
Dropout tolerances are even stricter; for example, even if 30 dropouts are allowed on one roll of magnetic tape, dropouts are not allowed on disks, and the wear resistance of the magnetic layer of disks is also subject to higher requirements in terms of characteristics. will be done.

It is known for magnetic tapes that in order to improve the abrasion resistance of the magnetic layer, it is preferable to use a polyurethane resin or a mixture thereof with a vinyl chloride-vinyl acetate copolymer as a binder. In addition, higher fatty acids are used as binders,
It is known that wear resistance is improved by containing a lubricant such as a higher alcohol, fatty acid ester, or silicone oil.

However, even if these are combined, the wear resistance of the magnetic layer of the disk will not be satisfactory if the lubricant oozes out, resulting in dropouts and decreased output, and in the worst case, the wear of the magnetic layer will cause complete loss of υ. It has the disadvantage of becoming peeled off.

The inventors of the present invention conducted various studies to improve these drawbacks, and as a result, we used a specific polyurethane prepolymer and a vinyl copolymer thereof as a binder for the magnetic layer.
Furthermore, it has been found that by containing a specific lubricant, wear resistance is improved, the lubricant does not ooze out, and stable disk durability is maintained over a long period of time.

That is, in the present invention, the binder component has a urethane group and a hydroxyl group at the end and has an average molecular weight of 2.
A magnetic layer formed by adding a urethane prepolymer having a molecular weight of 0,000 to 100,000, a vinyl copolymer having a hydroxyl group in a side chain having an average molecular weight of 10,000 to 30,000, and a trifunctional polyisocyanate compound having a molecular weight of 1,000 or less,
Higher fatty acids having 12 to 18 carbon atoms and 12 to 18 carbon atoms
It contains an ester of a high Ml fat e and an alkyl ether.

The urethane prepolymer used in the present invention has a urethane group in one molecule and a hydroxyl group at the end and has an average molecular weight of 20,000 to 100,000. Nisoporan-2301, -2304,
-3113゜TU-271, Tl-7 manufactured by Sanyo Chemical ■
121.

T-62603, T-62 manufactured by Dainippon Ink Chemical Industry ■
o1. Such as T-IN1.

This type of urethane prepolymer has excellent wear resistance and good dispersibility of magnetic powder.

If the molecular weight is less than 20,000, the wear resistance will be poor and 10
If it exceeds 0,000, the dispersibility of the magnetic powder becomes poor, resulting in a magnetic film with poor magnetic properties.

The vinyl-based copolymer ζ remer used in combination with the present invention is a copolymer having an average molecular weight of 10,000 to 30,000 and having a hydroxyl group in the molecule, and specific examples include VAGH and vAGn manufactured by UCC Corporation in the United States.

Examples include VYHH, VMCH, Eslenoku table manufactured by Sekisui Chemical Co., Ltd., Eslec B, and Denkabinil manufactured by Denki Kagaku Kogyo (■).

This type of vinyl copolymer has excellent dispersibility of magnetic powder, and since it has an OH group, it can undergo a crosslinking reaction with polyethylene oxide, thereby improving wear resistance and heat resistance.

If the molecular weight is less than 10,000, the strength of the coating will be poor;
If it is more than 00, the solubility in the solvent will be poor, and the paint will thicken and the solution will become gel-like, making it inconvenient to handle.

The content ratio of the urethane prepolymer and vinyl copolymer 17-7 in the binder is desirably 10010 to 50150 from the viewpoint of wear resistance, and as the vinyl copolymer is increased, durability decreases. Note that other resin components can be further added to the mixture as necessary.

The incyanate compound used in combination with the present invention preferably has a trifunctional incyanate group and has a molecular weight of 1000 or less, and is preferably a compound obtained by reacting 1 mole of triol with 23 moles of bifunctional incyanate. used as something. Specific examples of trifunctional low molecular weight ino7anate compounds include Coronate L manufactured by Nippon Polyurethane Industries, Dismodul L manufactured by Bayer AG in West Germany, and Burnock DN-9 manufactured by Dainippon Ink and Chemicals.
50, etc.

In this isonoanate compound, the trifunctional incyanate group reacts with the terminal OH group of the urethane prepolymer and the ○H group of the vinyl copolymer to form a linear crosslink.
The strength of the magnetic layer is increased, heat resistance is improved, and durability is improved.

The total blending ratio of the urethane prepolymer and vinyl copolymer to the isocyanate compound is 98/2 to 7o/3.
A range of 0 is desirable; if the amount of the isonoanate compound is too small, there will be no effect and the heat resistance and abrasion resistance will decrease, and if it is too large, the magnetic layer will be poor in flexibility.

Specific examples of higher fatty acids having 12 to 18 carbon atoms used in the present invention include lauric acid and mininostic acid.

Examples include valmitic acid, stearic acid, and oleic acid. Examples of the alkyl ether with a higher fatty acid having 12 to 18 carbon atoms used in combination with the above fatty acid include esters such as methyl ether ether, monopropyl ether, and monoph9thyl ether.

The magnetic layer obtained by kneading the magnetic powder, solvent, and lubricant in step 11 before the combination of the polyurethane prepolymer, vinyl copolymer, and ino7anate compound can improve wear resistance and reduce the There is no tendency for lubricant to ooze out and the magnetic head will not get dirty or sticky. Furthermore, since there is no oozing over time, there is no transfer of lubricant to the liner, and the lubricating function is maintained over a long period of time.

As for the content, the total amount of higher fatty acids and esters of higher fatty acids and alkyl ethers is preferably 1 to 10 parts by weight per 100 parts by weight of the magnetic powder.

If the amount is too large, the surface condition of the magnetic layer deteriorates and dropouts tend to occur, which is not preferable.

Here, the methods of incorporating the higher fatty acids and esters of higher fatty acids and alkyl ethers into the magnetic layer are as follows: In addition to the method of kneading with a normal binder as described above, pre-formed polyurethane and vinyl copolymer The lubricant component dissolved in a solvent such as toluene, methyl ethyl ketone, or cyclohexanone may be coated or sprayed onto the magnetic layer containing as a binder, or the magnetic layer may be immersed in the lubricant solution. .

The magnetic powder used is γ-Fe203.

Fe304, Go-containing Fe2es, Go-containing F
esO4.

In addition to CRO 2, various conventionally known magnetic powders such as metal powders such as Fe and Go are widely included.

In order to manufacture the flexible magnetic disk of the present invention, it can be carried out according to the conventional method. [Bonding symmetry I] component consisting of a compound. Organic solvent. A magnetic paint containing other additives is applied, and lubricating components are added to the paint or sprayed onto the magnetic layer. Impregnate by immersion. Punch this out into a disk shape to make a disk.

Examples of the present invention will be described below.

(Example 1) A mixture consisting of this composition was heated in a ball mill for 60 minutes.

A magnetic paint was prepared by time mixing and dispersion. This magnetic paint is applied onto a 76 μm thick polyester reflex 4) rem so that M is about 2 μm, dried, punched out to the desired disc size, and then surface treated and polished to form a flexible magnetic disc. Had made.

(Example 2) In the composition of the magnetic paint in Example 1, KP-23
butoxyethyl ole, ate (13S1 in the US) instead of
A magnetic disk was produced in the same manner as in Example 1, except that the same amount of 8r (manufactured by Co., Ltd.) was used.

(Example 3) In the composition of the magnetic paint in Example 1, the same amount of N-2301 was used without adding VAGH.
I made a magnetic disk in the same way.

(Comparative Example) A magnetic disk was produced in the same manner as in Example 1, except that the binder component and lubricant component in the composition of the magnetic paint in Example 1 were replaced with those shown in Table 1.

The magnetic disks obtained in Examples 1 to 3 and Comparative Example were inserted into a jacket lined with a liner and loaded into a recording/reproducing apparatus. This recording/reproducing device has a head pressure of 16
! The rotation speed is 360 rpm with a double-sided magnetic head of No. 9. First, on the outermost periphery of the magnetic disk, 12
e; Record the Kuz signal, then turn the recording/playback device over 40
It was transferred to a constant temperature and humidity chamber at 80% RH and was subjected to a durability test in which it was continuously regenerated under these conditions. The average output and number of dropouts were measured every 500,000 buses, and the durability life was defined as the time when the output reached 80% or less of the initial value. When the disk reached the end of its service life, the surface, head, and liner were observed for dirt using a microscope, and the state of lubricant leakage was investigated. Table 2
is the result.

Margin Table 2 Below, as is clear from Table 2, a magnetic layer is formed by adding a vinyl copolymer and an isone anate compound to a high molecular weight urethane prepolymer, and containing higher fatty acids and esters of higher fatty acids and alkyl ethers as lubricant components. The disk according to the present invention has a long durable life and does not seep out of lubricant, so the head and liner do not become dirty, and dropouts do not occur, making it possible to obtain excellent performance and durability.

Such an effect cannot be obtained with a disc using only a polyurethane or -vinyl copolymer having a molecular weight of 20,000 or less as a binder, nor can it be obtained with a disc using only Noricon oil, fatty acid ester, or higher fatty acid as a lubricant.

Claims (1)

[Claims] As a binder component, a urethane prepolymer having an average molecular weight of 20,000 to 100,000 having a urethane group and a hydroxyl group at the end, and a vinyl copolymer having an average molecular weight of ioooo to 300o○ and having a hydroxyl group in the side chain;
The magnetic layer contains a trifunctional isone anate compound having an average molecular weight of 1Q00 or less, and the content in the binder of the urethane prepolymer is 60% or more. Flexible magnetic disk containing ester.