JPS60182575A - Flexible magnetic disk - Google Patents

Abstract

PURPOSE:To enable loading of a flexible magnetic disk to a driving device always without eccentricity by providing a protective layer of a specific thickness formed by curing a compsn. contg. a compd. having a (meth)acrylate bond by radiations on the peripheral edge of the central circular hole of said disk. CONSTITUTION:A radiation polymerizable and curable protective layer 11 consisting of a compd. which has a (meth)acrylate bond in at least one of the molecular principal chain terminal and side chain, of which the number of the ester bond is 1-10 pieces for each 1,000mol.wt. and in which the skeletone of the principal chain is polyester, polyurethane, polyether, polycarbonate, epoxy, etc. or the mixed skeletone thereof is formed to the peripheral edge of the central circular hole 10a of a flexible magnetic disk 10. The thickness of the protective layer is made <=30mu and the surface roughness thereof is made 0.03mu in the average roughness (Ra) of the centerline at cut off 0.25mm.. The friction of the disk 10 with a positioning member is thus decreased and the disk is loaded to the device without eccentricity. The disk having no problem in track accuracy is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to improvements in flexible magnetic disks, and more particularly to flexible magnetic disks that can be loaded into writing and reading devices without eccentricity.

(Prior art) A conventional flexible magnetic disk 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 the magnetic disk is rotated to remove the sheet. There are known devices on which magnetic recording is performed or magnetic reproduction is performed from the sheet. This type of magnetic disk makes noise because the sheet is stored in the jacket with some margin, so the sheet inside may shift to a lopsided position within the jacket during storage, handling, or banding, and when the disk is loaded into the device. The circular hole in the center of the sheet may be eccentric with respect to the position of the positioning member (collect) of the apparatus, and the sheet may be held by the eccentric apparatus during positioning.

Figures 1A and iB show this kind of flexible magnetic sheet tractor, which has a rectangular jacket/with a circular opening/a in the center, in which the periphery of a central circular hole 2a is exposed. Circular flexible magnetic sheet λ
is rotatably stored.

When loading this flexible magnetic disc writing and reading device, as shown in FIG.
44 is lowered and press-fitted into the four circular parts 3a of the rotating part 3. At this time, the periphery of the central circular hole core a of the GITCO is the rotating part 3.
The position of the circular recess 3a does not necessarily match, and is often misaligned, so the collet ≠
When lowered, a part of the periphery of the circular hole 2a of the shell J is sandwiched between the cholera shell 4t and the recess 3a of the rotating part 3, as shown in FIG. 3, causing it to rotate eccentrically.

Since writing and reading cannot be performed correctly unless the magnetic disk sheet 2 is rotated so that its center is always aligned with the rotation center axis, it must be prevented from being held in such a position. Also, it is kept in this state,
There is also the problem that when rotated, the flatness of the JITCO is lost, causing it to curl when rotated. When the collet 4L is lowered to clamp the sheet l, the sheet l is not as shown in FIG. It is necessary that the coefficient (μ) be small.

For this purpose, Japanese Patent Application Laid-Open No. 37-13 Hiroshi λλ
A method has been disclosed in which a protective layer containing a polyolefin material that can be photopolymerized by ultraviolet light and a fatty acid ester is provided on a portion of the periphery of a central circular hole of a flexible magnetic disk that comes into contact with a sheet positioning member to reduce the coefficient of friction.

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

The shrinkage during curing (polymerization shrinkage) increases,
This impairs the flatness of the flexible magnetic disk, worsens the dimensional accuracy, and has a negative effect on the tracking accuracy.

In addition to the above-mentioned inventions, we also have a patent application! ? -1soasr, patent application Sho 1t-IJOIA 3, patent application Sho zr-λl 1,
No. 07 and others also disclose a method of reducing the coefficient of friction by providing a protective layer containing fat and heel lubricant that can be cured by UV irradiation.

However, there are cases where the above-mentioned protective layer is still not sufficiently effective in certain drives.

Therefore, the present inventor S has made the protective layer thinner by making the protective layer thinner.
The inventors have discovered that by roughening the surface of the protective layer, even more remarkable effects can be achieved, leading to the present invention.

(Objective of the Invention) The object of the present invention is to provide a flexible magnetic disk that maintains low friction between the flexible magnetic disk sheet and the positioning member, can be loaded into a device without eccentricity, and has no problems in terms of track accuracy and dimensional accuracy. It's about doing.

(Structure of the Invention) That is, the above objects of the present invention are (1) In a flexible magnetic disk in which a protective layer is provided at the periphery of the central hole of a flexible magnetic disk sheet, the protective layer is formed of at least one of the main chain end and the side chain of the molecule. A flexible magnetic disk comprising a composition comprising a compound having an ester bond with acrylic acid or methacrylic acid, the protective layer being cured by radiation irradiation, and having a thickness of 30 μm or less; 2) The surface roughness of the protective layer is cut
offλ, j7rLrrL center line average roughness Ra)
This can be achieved by the flexible magnetic disk described in (1) above, which is characterized in that it has a value of 0.03 μTrL 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 at at least one of the terminal end of the main chain and the side chain of the molecule, and the number thereof is I, 10, preferably /-A per 1000 molecular weight. , more preferably 2 to φ. The molecular weight is not particularly limited, but preferably ranges from 0 to 30,00θ, /, 0
More preferred are those in the oligomer to polymer range of 0ON2Q, 000. The main chain skeleton is preferably a polyester skeleton, a polyurethane skeleton, a polyether skeleton, a polycarbonate skeleton, an epoxy resin skeleton, or the like. You may also use it as

In the present invention, radiation refers to low-energy radiation such as ultraviolet rays, high-energy radiation such as alpha rays, X-rays, and electron beams. Among these, I especially prefer ultraviolet rays because the generator is simple and convenient.

When ultraviolet rays are used as radiation, it is preferable to contain an aromatic ketone as a photopolymerization initiator. Aromatic ketones are
Although not particularly limited, 2JlA, 3/
3. A material having a relatively large extinction coefficient at a wavelength of J6jnm is preferable.

Representative examples include acetophenone, benzophenone, benzoin ethyl ether, benzyl methyl ketal, benzyl ethyl ketal, benzoin isobutyl ketone, hydroxydimethyl phenyl ketone, l-hydroxycyclohexylphenyl ketone, λ-2 jetoxyacetophenone, M i c Various aromatic ketones can be used, including hlers ketone.

The mixing ratio of the aromatic ketone is 0.15 to 20 parts by weight, preferably 2 to 1M parts, based on the weight of the compound lθO.
Even better is 3-10. Q: It's the limbus.

In the present invention, (1) it is preferable to add a lubricant to the composition to lower the coefficient of friction.

Examples of lubricants include saturated fatty acids, unsaturated fatty acids, fatty acid esters, fatty acid amides, silicone lubricants, mineral oil, food oil, fluorine compounds, graphite, molybdenum disulfide, and tungsten disulfide. Solid lubricants such as , boron nitride, graphite fluoride, and metal oxides can be used.

The mixing ratio of the lubricant is /- with respect to the weight of the compound ioo
A 10-layer similar portion is preferred.

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

In the present invention, the thickness of the protective layer can be 30 μm or less, preferably /jμ7FLy, more preferably 7
It is less than μm. The surface roughness of the retaining layer is preferably 0003 μm or more, and preferably 007 μm or more.

A protective layer! If the t difference is 30 μm or more, the off-track will be 9 points, which is a practical problem, and the flatness will be distorted, which will cause problems in terms of appearance.

If it is 30 .mu.m or less, off-track is recognized, but there is no practical problem; if it is 30 .mu.m or less, off-track is slightly recognized, but there is no problem. Furthermore, if the thickness is 7 μm or less, no off-track will be observed, and the best results will be obtained when the load is ≠ μm or less.

Screen printing, tampo printing, and offset printing are used as the printing method for providing protection 1i%. In particular, offset printing is best for thin layer coating, followed by tampo printing.

(Example) The present invention will be explained below using examples.

FIG. 5 shows an embodiment of the present invention, in which a protective layer 1/1 according to the present invention according to the present invention is applied by offset printing along the periphery of the central circular hole 10a of the flexible magnetic sheet lθ on both the front and back surfaces. The mixture was polymerized and cured by irradiation with ultraviolet light using a Tro'H7- high pressure mercury lamp.

The width of the protective layer was smm.

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

Example/, 4. Comparative Examples 1~λ Polyurethane acrylate manufactured by Toagosei "M-/100J/θO 1 part butyl stearate jz Benzyl dimethyl ketal j # Here, the thickness and surface roughness of the protective layer were changed as shown in Table 7,
Samples for implementation and comparative examples were created.

Comparative example 3 A sample without a protective layer was used.

/Measurement of the f friction coefficient with the positioning member in the example and comparison rows and loading test into the disk drive were carried out 2j.
The results obtained under conditions of 0.00% RH are shown in Table 7.

The friction coefficient was measured by moving the positioning member (rotating part) on the magnetic sheet at a feeding rate of 0.1 mm/sec and applying friction (7, an additional load M's near 0 g).

The surface roughness was determined by Koita Research Institute's Surfcorder ModeISE.
-3E was used for measurement.

The drives used for the disk drive loading test were YD-2ro Okubi 3fO1 manufactured by Y-E Data, JA7zi Orabi 3611 manufactured by Matsushita Tsuko, and M-2 manufactured by Mitsubishi Electric.
191A and III! ;3.

The test included a magnetic disk for each drive.

Each disk was repeatedly loaded 30 times in a row, and any magnetic disk that was defective even in 91 tests (50 consecutive tests for all drives) was considered defective, and the defective rate was calculated from the number of disks with defects [7].

The results are shown in Table 2.

Further, the results of practical characteristics are shown in Table 2.

Table 2 Practical characteristics *) Excellent: No off-track Good: No problem Possible Nionodorak is hindered, but no practical problem Impossible:
Practical Problems As is clear from the above-mentioned bearings, in order to successfully load a flexible magnetic disk sheet into a disk drive, it is necessary to lower the coefficient of friction with the rotating part. For the 7ζ to achieve 11+, protect by UV curing etc.'arf! I is valid. By reducing the thickness of the protective layer, the dimensions and tracking accuracy of the magnetic disk sheet can be maintained, and no adverse effects such as an increase in the coefficient of friction or an increase in the rate of defective loading due to the thin layer are observed.

Furthermore, it is clear that roughening the surface of the retention layer is effective in reducing the coefficient of friction and the rate of defective loading.

As is clear from the above, in order to load a flexible magnetic disk sheet into a disk drive without failure, it is necessary to reduce the coefficient of friction with the rotating part. In order to achieve this, a protective layer formed by UV curing is effective. By reducing the thickness of this storage M, the dimensions and tracking accuracy of the magnetic disk sheet can be maintained, and what's more! There are no discernible adverse effects due to the W layering, such as an increase in the coefficient of friction and an increase in the rate of defective loading.

It is clear that roughening the surface of the protective layer is effective in reducing the coefficient of friction and the rate of defective loading.

[Brief explanation of drawings]

Fig. 1A is a plan view showing the relay of the flexible magnetic disk, Fig. 113 is a sectional view thereof, Fig. 2 is a partial sectional view showing the state in which the flexible magnetic disk is loaded into the positioning member of the device, and the third factor is the same. Figure μ is a partial cross-sectional view showing the sheet being held eccentrically, and Figure μ is a partial cross-sectional view showing the sheet correctly positioned.'JX! The figure is a plan view showing the seat portion of an embodiment of the present invention, l... Jacket la... Jacket opening λ...
・Magnetic seat 1--2a...Central circular hole 3...Positioning member (rotation 1) 3a...Circular recess ≠...Positioning member (collet) IO...Magnetic sheet, / Q a ...Central hole l/...Protective layer Patent applicant Fuji Photo 7-1 Lum Co., Ltd. Drawings Jokichi (
No change in content) Figure 2 Figure 3 Figure 4 Procedural amendments Dear Commissioner of the Patent Office■, Small case display Showa! Patent Application No. 3T, ltO No. 2
, Title of the invention: Flexible magnetic disk 3, Relationship with the person making the amendment, Patent applicant contact information: 2-26-30-4, Nishi-Azabu, Minato-ku, Tokyo 106, Subject of the amendment: Description and drawings 5, Details of the content of the amendment We will provide you with an engraving of the calligraphy and drawings (with no changes to the contents). Procedural amendment document Showa to λ month/day, 1. +i'7'l"J't"A1. 1. Indication of the case: Showa!R Patent Application No. 31r, No. 160 2, Title of the invention: Flexible magnetic disk 3, Relationship with the person making the amendment: Patent applicant: Address: 210 Nakanuma, Minamiashigara City, Kanagawa Prefecture Name: (52
0) Fuji Photo Film Co., Ltd. 4. Subject of amendment: "Claims" column of the specification, "Detailed Description of the Invention" column 5, Contents of the amendment l) "Claims" column of the specification Correct as shown in the attached sheet. -2) "The present inventor S" on page 5, line 7 of the same book is amended to read "the present inventors." 3) Correct page 7-r line rcutoff-2, 7mj of the same book to [cutoff O', 2jvx]. (g) Ibid., page 1, table 1, column 3, line 3 r(cutoff-2,t,)j is corrected as [(cutoff=0,2jm)J. (Attachment) 2. Claims (11. Central circular hole layer i of flexible magnetic Guisfu sheet)
In a flexible magnetic disk provided with a K protective layer, the protective layer is a composition containing a compound having an ester bond with acrylic acid or methacrylic acid at at least one of the terminal end of the main chain and the side chain of the molecule), and the protective layer A flexible magnetic disk characterized in that the layer is υ hardened by radiation irradiation and the protective layer has a thickness of 3θ μm or less. ! 2. The flexible magnetic disk according to claim 1, wherein the centerline average roughness (Ra) of dew is 0.03 μnt or more.

Claims (1)

[Claims] (11) In a flexible magnetic disk in which a protective layer is provided around the central hole of a flexible magnetic disk sheet, the protective layer has acrylic acid or methacrylic acid at the end of the main chain and at least one of the side chains of the molecule. A flexible magnetic disk made of a composition containing a compound having an ester bond, characterized in that the protection 1- is cured by radiation irradiation, and the thickness of the protection layer is 30 μm or less. (2) The protection 1- The surface roughness of cut off, j
The flexible magnetic disk according to claim 1, wherein the center line average roughness (Ra) in mm is (7, (73 μm or more) or more.