JPS5828651B2 - Magnetic disk manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a magnetic disk or a magnetic sheet.

More specifically, the present invention relates to a method for orienting a coating layer containing a magnetic material coated on the surface of a support of a magnetic disk or magnetic sheet.

Generally, a magnetic disk or a magnetic sheet refers to a flat support with a magnetic layer provided on its surface.

In this case, if necessary, a protective layer may be provided on the surface of the magnetic layer, and further an antistatic layer, a running stabilizing layer, etc. may be provided on the support.

Among these, those using a less flexible support are usually called magnetic disks, and those using flexible ones are usually called magnetic sheets, but the distinction between the two is not very clear. Not clear.

Here, it is assumed that both are included in the magnetic disk.

The shape of the magnetic disk is usually donut-shaped, but elliptical, rectangular, square, or other irregular shapes may be used as necessary.

When used in donut shape, the outer diameter is 10cfIL
-50 cm, and the inner diameter is generally 3 mm to 250 mm.

The thickness of the magnetic layer of a magnetic disk varies depending on its use, but 0.05μ to 100μ is often used.

In addition, the thickness of the support used for magnetic disks is 3μ to 1μ.
There are many OTLrILs, and depending on the purpose, they are used ranging from extremely flexible to less flexible.

Further, the total thickness is often 3μ to 151n71L.

Such magnetic disks are manufactured by applying a coating solution containing a magnetic material onto a support, followed by drying and other treatments. Conventionally, a method called a spin code method has been exclusively used as the coating method. Ta.

In this spin code method, a magnetic layer is formed on the surface of the support by supplying a coating liquid through a nozzle from the upper or lower surface of the support while rotating the support.

(U.S. Patent No. 3,198,657, Japanese Patent Publication No. 1987-32
．． No. 006, JP-A-48-63,709, JP-A-49-Sho.
-113,608, JP-A-49-114,402, etc.

) However, magnetic disks manufactured by such a method do not have sufficient surface properties.

It had defects such as large noise and poor S/N ratio, insufficient output due to non-orientation, and poor squareness ratio of the magnetic layer in the recording direction.

As a method for removing such defects, Japanese Patent Application Laid-Open No. 50-43
, 902 has been proposed.

The method disclosed herein uses a metal disk as a support, and after applying a coating liquid containing a magnetic substance to the metal disk, a magnetic flux is generated that is parallel to the disk surface and parallel to the tangential direction of the disk. It is said that by orienting magnetic particles using an external magnetic field and forming a cured coating film by heating, a magnetic disk with a high squareness ratio and high reproduction output can be obtained.

It is true that with this method, it is possible to obtain a magnetic disk with a high squareness ratio and high playback output, but since the orientation is performed using a magnetic field, it has the drawback that the equipment becomes expensive. .

SUMMARY OF THE INVENTION An object of the present invention is to provide a method of manufacturing a magnetic disk with an excellent squareness ratio in the arrangement direction by eliminating such conventional defects.

Another object of the present invention is to provide a method for manufacturing a magnetic disk with excellent surface properties.

Another object of the present invention is to provide a method for manufacturing a magnetic disk with a high reproduction output.

Another object of the present invention is to provide a method for manufacturing a magnetic disk with low noise and improved S/N ratio.

Another object of the present invention is to provide a method for manufacturing a magnetic disk with less dropouts.

Another object of the present invention is to provide a method for manufacturing a magnetic disk with excellent magnetic recording characteristics using a simple and inexpensive apparatus.

Such an object of the present invention is to apply a flexible sheet to one part of the coating surface when applying a coating liquid containing a magnetic substance to the surface of a magnetic disk support, or after coating, while the coating liquid is not yet applied or solidified. This is achieved by bringing the magnetic disk and the flexible sheet into contact with each other and causing relative movement between the magnetic disk and the flexible sheet.

FIG. 1 is a road view of an orientation device showing a preferred embodiment of the present invention.

Reference numeral 1 denotes a circular magnetic disk support, on the surface of which a magnetic layer 2 made of a coating liquid containing a magnetic substance is provided, and is rotated in the direction of arrow A.

A flexible sheet 4 supported by a support 3 is brought into contact with the surface of the magnetic layer 2, and the unmounted and unsolidified magnetic layer 2
Orientation and smoothing are performed.

At this time, if the flexible sheet 4 is fixed, wrinkles are likely to occur in the flexible sheet 4, making it impossible to smooth the surface of the magnetic layer 2 and making it impossible to achieve good orientation. .

Therefore, it is necessary for the flexible sheet 4 to move circularly or linearly along the surface of the magnetic disk support 1.

This is intended to prevent the occurrence of wrinkles in the flexible sheet 4 by directing the direction of the force exerted by the magnetic layer 2 on the flexible sheet 4 in the longitudinal direction of the flexible sheet 4 as much as possible. .

Therefore, the manner in which the flexible sheet 4 is moved is not necessarily limited to the above-mentioned directions, as long as such conditions are satisfied.

When such a flexible sheet 4 is brought into contact with an unmounted, unsolidified magnetic layer 2, the magnetic ratio layer 2 is subjected to a large shearing force by the flexible sheet 1-4 and the support 1 due to the relative movement between the two. , the magnetic particles in the magnetic ratio layer 2 are oriented concentrically.

Furthermore, by bringing such a flexible sheet 4 into contact with the surface of the magnetic layer 2, the coating liquid constituting the magnetic layer 2 can be dispersed, thereby reducing noise on the magnetic disk and preventing agglomeration of the coating liquid. Since the small foreign particles caused by the magnetic disk are further loosened and dispersed, dropouts of the magnetic disk are reduced.

Furthermore, since the magnetic layer 2 is forcibly dispersed when it is not loaded or solidified, the surface of the magnetic layer 2 is smoothed.

As a result, a magnetic disk with low noise and an excellent S/N ratio can be obtained.

The shape of the flexible sheet 4 may be square, rectangular, polygonal, or various other shapes as illustrated in FIG.

The flexible sheet 4 may be brought into contact with the surface of the magnetic layer 2 at the time of coating or after the coating, as long as the magnetic layer 2 is not placed on or solidified.

It goes without saying that the present invention is not limited to the above-described embodiments, and that various modifications can be made.

For example, the shape of the support for the magnetic disk is not limited to circular, but as mentioned above, various shapes can be used.
In addition, the magnetic disk support 1 is fixed, and the flexible sheet 4 is
It is also possible to use only a dynamic model.

Furthermore, orientation by the flexible sheet 4 and magnetic field orientation can also be used together.

In the present invention, the magnetic material, that is, the ferromagnetic fine powder is γ-Fe2O3)F containing γ-Fe2035 Co.
e 304 , Co-containing Fe3O4, CrO2,C
Known ferromagnetic fine powders such as o-N1-P alloy and Fe-Co-Ni alloy can be used.
-14090 Publication, Special Publication No. 18372/1972,
Special Publication No. 47-22062, Special Publication No. 47-2251
Publication No. 3, Special Publication No. 46-28466, Special Publication No. 1973
-38755, Japanese Patent Publication No. 47-4286, Japanese Patent Publication No. 12422, Japanese Patent Publication No. 47-17284
Publication No. 18509, Special Publication No. 18509, Special Publication No. 18509, Special Publication No. 18509
The one described in Publication No. 18573 etc. can be used.

As for the shape of the powder, the higher the needle-like shape is, the more preferable it is, and the needle-like magnetic material is particularly desirable.

The magnetic material is dispersed in a binder, and various additives are added as necessary to form a coating liquid.

In the present invention, as the binder, conventionally known thermoplastic resins, thermosetting resins, reactive resins, and mixtures thereof are used.

As a hot plastic injection resin, the softening temperature is 150℃ or less, the average molecular weight is 1oooo~200,000, and the degree of polymerization is about 200~
500, such as vinyl chloride vinyl acetate copolymer, vinyl chloride vinylidene chloride copolymer, vinyl chloride acrylonitrile copolymer, acrylic ester (acryloni) copolymer, acrylic ester vinylidene chloride copolymer , acrylic acid ester styrene copolymer, methacrylic acid ester acrylonitrile copolymer, meccrylic acid ester vinylidene chloride copolymer, meccrylic acid ester styrene copolymer, urethane elastomer, polyvinyl fluoride, vinylidene chloride acrylonitrile copolymer, pig Genacrylonitrile copolymer, polyamide resin, polyvinyl butyral, cellulose derivative,
(cellulose acetate butyrate, cellulose diacetate, cellulose triacetate, cellulose propionate, nitrocellulose, etc.), styrene butylene copolymer, polyester resin, chlorovinyl ether acrylate copolymer, amino resin, various synthetic rubbers Netsucho plastic injection resin and mixtures thereof are used.

To form the magnetic recording layer, the above-mentioned composition is dissolved in an organic solvent and applied as a coating solution onto a support.

Examples of these resins are given in Japanese Patent Publication No. 37-6877, 39
-12528, 39-19282, 40-5349
No. 40-20907, No. 41-9463, 41-1
No. 4059, No. 41-16985, No. 42-6428,
42-11621, 43-4623, 43-152
No. 06, No. 44-2889, No. 44-17947, 44
-18232, 45-14020, 45-1450
No. 0, No. 47-18573, No. 47-22063, 47
It is described in publications such as No. 22064, No. 47-22068, No. 4722069, No. 47-22070, and No. 4727886.

The thermosetting resin or reactive resin has a molecular weight of 2×10 5 or less in the state of a coating solution, and when heated after coating and drying, the molecular weight becomes infinite due to reactions such as condensation and addition.

Also, among these resins, those that do not soften or melt before the resin is thermally decomposed are preferred.

Specifically, for example, phenol resin, epoxy resin, polyurethane curable resin, urea resin, melamine resin, alkyd resin, silicone resin, acrylic reaction resin, epoxy-polyamide resin, nitrocellulose melamine resin, high molecular polyester resin, and isocyanate. Mixtures of prepolymers, mixtures of meccrylate copolymers and diisocyanate prepolymers, mixtures of polyester polyols and polyisocyanates, urea formaldehyde resins, low molecular weight glycols/polymers, diols/triphenyls, mixtures of methane triincyanates, polyamines These include resins and mixtures thereof.

Examples of these resins are given in Japanese Patent Publication No. 39-8103, 40-
No. 9779, No. 41-7192, No. 418016, 41
-14275, 42-18179, 43-1208
No. 1, No. 44-28023, No. 45-14501, 45
-24902, 46=13103, 47-2206
No. 5, No. 47-22066, No. 47-22067, 47
-22072, 47-22073, 47-2804
It is described in publications such as No. 5, No. 47-28048, and No. 4728922.

These binders may be used alone or in combination;
Other additives may be added.

The mixing ratio of the ferromagnetic powder and the binder is in the range of 10 to 200 parts by weight of the binder to 100 parts by weight of the ferromagnetic powder.

Additives include dispersants, lubricants, and abrasives.

In the present invention, the magnetic disk supports include polyesters such as polyethylene tereclate and polyethylene 2,6-nuclate, polyolefins such as polyethylene and polypropylene, cellulose guaacetate,
Cellulose derivatives such as cellulose triacetate, cellulose acetate/butyrate, and cellulose acetate propionate, vinyl resins such as polyvinyl chloride and polyvinylidene chloride, plastics such as polycarbonate, polyimide, and polyamideimide, as well as aluminum and copper depending on the application. Non-magnetic metals such as glass, pottery, ceramics such as porcelain, paper, baryta or polyethylene,
Shore prime number 2 of polypropylene, ethylene butene copolymer, etc.
Papers such as those coated or laminated with α-polyolefins of 1 to 10 can also be used.

These supports may be transparent or opaque depending on the purpose of use.

Methods for applying the magnetic layer onto the support include air doctor coating, blade coating, air knife coating, squeeze coating, dip coating, reverse roll coating, transfer roll coating, gravure coating, kiss coating, cast coating, and spray coating. Other methods are also possible, and detailed explanations of these can be found in "Coating Engineering" published by Shokusen Shoten, pages 253-277.
(published on March 20, 1972).

In the present invention, the flexible sheet refers to a sheet that is highly flexible and has a thickness of about 1 μm to 1000 μm, and any material that is highly flexible can be used.

For example, polyesters such as polyethylene terephthalate and polyethylene-2,6-nuclate; polyolefins such as polyethylene and polypropylene; cellulose derivatives such as cellulose guiacetate, cellulose triacetate, cellulose acetate butyrate, and cellulose acetate flobionate; In addition to vinyl resins such as vinyl chloride and polyvinylidene chloride, plastics such as polycarbonate, polyimide, and polyamideimide, paper, baryta, or polyethylene, polypropylene, and ethylene-buden copolymers with 2 to 10 carbon atoms are used depending on the purpose. Paper such as paper coated or laminated with α-polyolefin can also be used.

These supports may be transparent or opaque depending on the purpose of use.

The shape of the flexible sheet may be a square, a rectangle, a polygon, a circle, a part of an arc, or a combination of these shapes, as illustrated in FIG.

Example 1 A coating solution having the composition shown in Table 1 was applied to a thickness of 6 μm by spin coating onto an aluminum substrate having a thickness L of 27 mrn, an outer diameter of 356 mm, and an inner diameter of 168 mm.

The coating conditions were as follows: rotation speed: 520 rlllm; coating liquid supply amount: 1.2 g/SeC.

A comparison was made between those in which a flexible sheet was brought into contact during application and those in which no such operation was performed.

All of the flexible sheets had a width of 78 ridges, were made of polyethylene terephthalate, and had a thickness of 36 μm.

The shape of the tip is shown in Table 2.

When bringing the flexible sheet into contact with the support, do so for 20 seconds after the coating liquid has been supplied to the support, and then shift the flexible sheet toward the outer periphery of the disk at a speed of 2 mm/sec to bring the disk into contact for about 40 seconds. I spoke more.

Afterwards, it was dried and the characteristics of the magnetic disk were investigated.

The measuring device used was an IBM 2311 type magnetic disk measuring device.

The results are shown in Table 2. The results show that the performance of the magnetic disk manufactured by the method according to the present invention is superior to that of a magnetic disk manufactured without using a flexible sheet.

Example 2 Using the disk substrate of Example 1, a coating solution having the composition shown in Table 3 was applied to a thickness of 4 μm by spin coating.

The coating conditions were as follows: rotation speed: 820 rp; supply rate of II11 coating liquid: 0.89/sec.

Those without a flexible sheet were dried immediately after application.

On the other hand, when a flexible injection sheet was used, orientation was performed using the flexible sheet after coating.

The width of the flexible sheet was 30 mm, the material was triacetylcellulose, and the thickness was 20 μm.

The shape of the tip is shown in Table 4.

Contact with the flexible sheet starts from the innermost diameter application area, 4
It was moved toward the outer periphery at a speed of 7IL/sec and released from the support in about 20 seconds.

The measurement was carried out using an IBM model 2311.

The results are shown in Table 4.

From these results, it was found that the magnetic disk manufactured by the method according to the present invention has superior performance compared to one that does not use a flexible sheet.

〔note〕

0 Circumferential squareness ratio...Disc after coating is 5m
It was cut into m×5 mm, a BH curve was determined using a B-H tracer, and the squareness ratio was determined from B r /Bm in the circumferential direction.

The closer the orientation is to 1.0, the better the orientation will be.

O Surface of the magnetic layer: The maximum value of the unevenness measured in units of roughness measured using a stylus type roughness needle with a stylus force of 0.1.9 on the coated area of the disk.

The smaller the disc, the better it is. ○Output...I recorded an 80Of (Hz signal on the outermost track using an IBM 2311 type device.
The output was compared in dB.

The larger the disc, the better the disc.

○) Isness: The integrated average noise after erasing was determined using the same device as above for samples 1 and 5, with OdB as OdB.

01. Dropout: A dropout is defined as a 6 dB drop from the average output over 60 microseconds over the disk surface.

This is a very good disc.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of a magnetic disk coating and orientation apparatus showing a preferred embodiment of the present invention. FIG. 2 illustrates the shape of a flexible sheet used in the present invention. 1...Support, 2...Magnetic ratio layer, 4...
...Flexible sheet.

Claims (1)

[Claims] 1. In a method of manufacturing a magnetic disk by applying a coating liquid containing a magnetic substance to the surface of a support to form a magnetic layer and further orienting the magnetic layer, a flexible sheet is not placed during or after the application, A method for producing a magnetic disk, which comprises orienting the magnetic layer by bringing the magnetic layer into contact with a part or the entire surface of the unsolidified magnetic layer and causing relative movement between the support and the flexible sheet. .