JPH0695433B2 - Flexible magnetic disk - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to improvements in flexible magnetic disks, and more particularly to flexible magnetic disks that are filled without eccentricity in write and read devices.

(Prior Art) Conventionally, a flexible magnetic disk sheet is housed in a jacket, and a sheet positioning member of a writing / reading device is engaged with a central circular hole provided in both the jacket and the sheet, and is rotated on the sheet. It is known to perform magnetic recording or magnetic reproduction from a sheet. In this type of magnetic disk, the sheets are stored in the jacket with some allowance, so when storing, handling or carrying, the inner sheet shifts to a biased position in the jacket,
When the device is loaded with a disk, the circular hole in the center of the sheet is eccentric to the position of the positioning member (collect) of the device,
The sheet may be held in an eccentric position during positioning.

FIGS. 1A and 1B show a flexible magnetic sheet of this type, in which a circular jacket 1 having a circular opening 1a in the center is formed into a circular shape in which the peripheral edge of a central circular hole 2a is exposed in the central circular opening 1a. The flexible magnetic sheet 2 is stored rotatably.

When the flexible magnetic disk is loaded into the writing and reading device, the rotary portion 3 of the positioning member is applied from below the sheet 2 as shown in FIG. Press into 3a.
At this time, the peripheral edge of the central circular hole 2a of the sheet 2 does not always coincide with the position of the circular recess 3a of the rotating portion 3,
Since it is often displaced, if the collet 4 is lowered as it is, part of the peripheral edge of the circular hole 2a of the sheet 2 is sandwiched between the collet 4 and the recess 3a of the rotating part 3 as shown in FIG. Will rotate. The magnetic disk sheet 2 must be prevented from being held in such a position because writing and reading cannot be performed correctly unless the center is properly rotated so as to coincide with the center axis of rotation. Also,
If the sheet 2 is held and rotated in such a state, the flatness of the sheet 2 is impaired, and there is also a problem of rattling at the time of rotation. When the collet 4 is lowered and the sheet 1 is sandwiched, in order for the sheet 1 to be properly loaded not as shown in FIG. 3 but as shown in FIG. 4, the peripheral edge of the central hole of the sheet has an appropriate hardness, In addition, it is necessary that the friction coefficient (μ) between the sheet 1 and the collet 4 and the rotating portion 3 is small.

For this purpose, JP-A-57-113422 discloses a protective layer containing a polyolefin resin and a fatty acid ester, which are polymerizable by ultraviolet rays, in the portion of the flexible magnetic disk which is in contact with the sheet positioning member around the central circular hole. Is provided to reduce the coefficient of friction.

However, the problem here is a practical problem due to the provision of the protective layer. That is, if the thickness of the protective layer is too thick, so-called track shift may occur during the operation, which is not preferable.

Also, the contribution of shrinkage (polymerization shrinkage) during curing becomes large,
The flatness of the flexible magnetic disk is impaired, the dimensional accuracy is deteriorated, and the track accuracy is adversely affected.

In addition to the above inventions, Japanese Patent Application Nos. 58-130438 and 58-
No. 130439 and Japanese Patent Application No. 58-219607 also disclose a method of reducing the friction coefficient by providing a protective layer containing a resin curable by ultraviolet irradiation and various lubricants.

However, there are cases in which the protective layer as described above cannot sufficiently exert the effect in a specific drive.

Therefore, as a result of intensive studies on the protective layer containing the radiation curable resin, the present inventors have shown that a more remarkable effect can be exhibited by thinning the protective layer and roughening the surface of the protective layer. And has reached the present invention.

(Object of the Invention) An object of the present invention is to provide a flexible magnetic disk in which friction between the flexible magnetic disk sheet and the positioning member is kept small, the apparatus is loaded without eccentricity, and there is no problem in track accuracy and dimensional accuracy. Especially.

(Structure of the Invention) That is, the above-mentioned object of the present invention is: (1) In a flexible magnetic disk in which a protective layer is provided around the central circular hole of a flexible magnetic disk sheet, the protective layer is provided on at least one of the main chain terminal and side chain of the molecule. A flexible magnetic disk comprising a composition containing a compound having an ester bond with acrylic acid or methacrylic acid, the protective layer being cured by irradiation with radiation, and having a thickness of 30 μm or less, and (2) the above Cut off the surface roughness of the protective layer
This can be achieved by the flexible magnetic disk described in (1) above, which has a center line average roughness (Ra) of 0.25 mm of 0.03 μm or more.

The compound that can be used in the present invention is a compound having an ester bond with acrylic acid or methacrylic acid on at least one of the terminal end and side chain of the molecule, and the number thereof is 1 to 10 per 1000 molecular weight, preferably 1 to 6 , And more preferably 2 to 4. The molecular weight is not particularly limited, but is preferably 500 to 30,000, more preferably 1,000 to 20,000 oligomers to polymers. The skeleton of the main chain is preferably a polyester skeleton, a polyurethane skeleton, a polyether skeleton, a polycarbonate skeleton, an epoxy resin skeleton, etc. Even if they are mixed skeletons, they may be used by mixing two or more kinds. Good.

In the present invention, the term "radiation" refers to ultraviolet rays which are low energy radiation, α rays, X rays, electron beams which are high energy radiation. Of these, an ultraviolet ray generator is particularly preferable because it is simple.

When ultraviolet rays are used as radiation, it is preferable to include an aromatic ketone as a photopolymerization initiator. Aromatic ketones
Although not particularly limited, those having a relatively large extinction coefficient at wavelengths of 254, 313, 365 nm, which generate a bright line spectrum of a mercury lamp usually used as an ultraviolet irradiation light source, are preferable.
Representative examples thereof include acetophenone, benzophenone, benzoin ethyl ether, benzyl methyl ketal, benzyl ethyl ketal, benzoin isobutyl ketone, hydroxydimethyl phenyl ketone, 1-hydroxycyclohexyl phenyl ketone, 2-2 diethoxyacetophenone, Michlers. There are ketones and the like, and various aromatic ketones can be used.

The mixing ratio of the aromatic ketone is 0.5 to 20% by weight, preferably 2 to 15 parts by weight, more preferably 3 to 10 parts by weight, based on 100 parts by weight of the compound.

In the present invention, it is preferable to add a lubricant to the composition to reduce the coefficient of friction.

As the lubricant, saturated fatty acids, unsaturated fatty acids and fatty acid esters, fatty acid amides, further lubricants such as silicone lubricants, mineral oils, food oils, fluorine compounds, graphite, molybdenum disulfide, tungsten disulfide, Solid lubricants such as boron nitride, graphite fluoride and gold oxide can be used. The mixing ratio of the lubricant is preferably 1 to 10 parts by weight with respect to 100 parts by weight of the compound.

When preparing the coating liquid, various organic solvents may be used as necessary.

In the present invention, the thickness of the protective layer may be 30 μm or less, preferably 15 μm or less, more preferably 7 μm or less. The surface roughness of the protective layer is preferably 0.03 μm or more, more preferably 0.1 μm or more.

When the thickness of the protective layer is larger than 30 μm, off-track is recognized, which is a problem in practical use, and there is a problem in that the flatness is distorted in appearance.

If it is 30 μm or less, off-track is recognized, but there is no problem in practical use, and if it is 15 μm or less, only off-track is recognized and there is no problem. Further, if the thickness is 7 μm or less, no off-track is noticed, and the best result is obtained especially when the thickness is 4 μm or less.

Screen printing, tampo printing, and offset printing are used as the printing method for providing the protective layer. Particularly, for thin layer coating, offset printing is the best and second best is tampo printing.

(Example) Hereinafter, the present invention will be described with reference to an example.

FIG. 5 shows an embodiment of the present invention. The protective layer 11 according to the present invention is applied by offset printing on both sides of the central circular hole 10a of the flexible magnetic sheet 10, and the protective layer 11 of 80 W / cm Ultraviolet rays were irradiated by a high pressure mercury lamp to polymerize and cure. The width of the protective layer was 3 mm.

The compositions of the protective layers of Examples and Comparative Examples were as follows.

Examples 1-6, Comparative Examples 1-2 Toa Gosei Synthetic Polyurethane Acrylate "M-1100" 100
Parts by weight butyl stearate 5 〃 benzyl dimethyl ketal 5 〃 where the thickness and surface roughness of the protective layer are changed as shown in Table 1,
Samples of Examples and Comparative Examples were prepared.

Comparative Example 3 A sample having no protective layer was used.

Table 1 The coefficient of friction with the positioning member and the loading test to the disk drive in the above-mentioned Examples and Comparative Examples were carried out at 25 ° C.
The results obtained under the condition of% RH are shown in Table 1.

The coefficient of friction was measured by rubbing the positioning member (rotating part) on the magnetic sheet at a feed rate of 0.8 mm / sec. And applying an additional load of 70 g weight. The surface roughness was measured using a surf coder Model SE-3E manufactured by Kosaka Laboratory.

The drives used for the loading test on the disk drive were YD-280 and 380 manufactured by Y-E Data, and Matsushita Tsuko.
JA751 and 561, and M-2894 and 4853 manufactured by Mitsubishi Electric Corporation. For the test, 10 magnetic disks were used for each drive, and repeated loading was performed 50 times for each drive. During all 50 continuous tests of the drive, a magnetic disk that failed even once was regarded as defective, and the number of failed disks The defective rate was calculated more.

That is, the defect rate is the ratio of the number of defective magnetic disks out of the total of 10 (6) = 60 = 10 disks in each of the six disk drives, as described above. Displayed at a rate of 100 minutes.

The results are shown in Table 1.

The results of practical characteristics are shown in Table 2.

As is clear from the above description, in order to load the flexible magnetic disk sheet into the disk drive without failure, it is necessary to reduce the coefficient of friction with the rotating portion, and to achieve this, A protective layer formed by UV curing is effective. By reducing the thickness of the protective layer, the size and track accuracy of the magnetic disk sheet can be maintained, and the thin layer does not cause adverse effects such as an increase in friction coefficient and an increase in defective loading.

Further, it is apparent that roughening the surface of the protective layer is effective for reducing the friction coefficient and the defective loading rate.

[Brief description of drawings]

FIG. 1A is a plan view showing an example of a flexible magnetic disk, FIG. 1B is its sectional view, FIG. 2 is a partial sectional view showing a state in which the flexible magnetic disk is mounted on the positioning member of the apparatus, and FIG. 3 is the same. FIG. 4 is a partial sectional view showing a state in which the sheet is held eccentrically, FIG. 4 is a partial sectional view showing a state in which the sheet is correctly positioned, and FIG. 5 is a sheet portion of one embodiment of the present invention. , 1 ... Jacket, 1a ... Jacket opening 2 ... Magnetic sheet, 2a ... Central circular hole 3 ... Positioning member (rotating part) 3a ... Circular recess, 4 ... Positioning member (collet) 10 ... Magnetic sheet, 10a ... Central circular hole 11 ... Protective layer

 ─────────────────────────────────────────────────── --Continued from the front page Judgment panel for referees Chief referee Takashi Fujita Referee Inquiry Hiroshi Inukai Referee Yoichi Yamada (56) References JP 57-113422 (JP, A) JP 56-25232 (JP, A) JP 58-146029 (JP, A)

Claims (1)

[Claims] 1. A flexible magnetic disk comprising a flexible magnetic disk sheet and a protective layer provided on the periphery of the central hole of the flexible magnetic disk, wherein the protective layer has an ester bond with acrylic acid or methacrylic acid at least at one of the main chain terminal and side chain of the molecule. And a protective layer which is cured by irradiation with radiation and has a thickness of 4 μm or more.
.mu.m or less, and the surface roughness of the protective layer is 0.03 .mu.m or more at the center line average roughness (Ra) with a cutoff of 0.25 mm.
A flexible magnetic disk having a thickness of 60 μm or less.