JPS6344313A - Production of magnetic disk substrate - Google Patents

Abstract

PURPOSE:To produce a magnetic disk substrate having excellent surface accuracy, heat resistance, strength, durability, etc., with good productivity at a low cost by laminating a thermosetting resin compsn. on the surface of a substrate consisting of an injection-molded heat resistant resin on the surface of a substrate. CONSTITUTION:The substrate is formed by using the thermosetting resin having >=180 deg.C thermal deformation temp. and by injection molding of said resin. The thermosetting compsn. consisting of an epoxy resin and polyparaphenyl phenolic resin is laminated on the surface of the substrate formed in such a manner and is cured to form the magnetic disk substrate. The magnetic disk substrate having the excellent surface accuracy (smoothness), heat resistance, strength, durability, etc., is thus produced with the good productivity at the low cost.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] Zero-Hatsu 11 #-i This invention relates to a method of manufacturing a magnetic disk substrate made of resin and having a smooth surface.

[Prior art]

Conventionally, aluminum alloys have been used for magnetic disk substrates because they are required to have strength and rigidity that can withstand high-speed rotation, ultra-precision machinability, heat resistance, and the like. However, surface accuracy (
In order to obtain smoothness, the finishing process by grinding and polishing was unnecessary, resulting in low productivity. Furthermore, since aluminum alloy substrates are heavy, there are problems such as load on the drive motor and heat generation, making it impossible to downsize the magnetic disk unit.

Recently, in order to solve the above-mentioned drawbacks, a substrate made of injection molded synthetic resin has been conventionally used, but the surface of the injection molded substrate has a drawback of low smoothness. In order to impart surface smoothness, for example, in Japanese Patent Publication No. 52-36684, the injection molded substrate is heated and pressed with a smooth metal pressure plate, and then a glass smooth plate with a smoothness of α1μ or less is used. It has been proposed to perform pressure molding while applying pressure, and JP-A-59-135133 discloses a method in which a crosslinkable material is applied to the surface of an injection mold, and a synthetic resin is injection molded into the crosslinkable material. is proposed.

However, the former method requires two sets of special smooth pressure plates, and the substrate must be heated and pressed twice after the injection FL shape, and the former method requires a mold with excellent smoothness. In addition, it is necessary to apply a crosslinking material to the inside of the mold each time the injection mold is formed, so both methods are difficult to manufacture and have low productivity.
It had the disadvantage of high production costs.

rProblems to be Solved by the Invention] In view of the above-mentioned drawbacks, the purpose of the present invention is to improve surface precision, @thermal property,
It is an object of the present invention to provide a method for manufacturing a lightweight magnetic disk substrate with excellent strength, durability, etc., with high productivity and at low cost.

[Means for solving problems]

The heat-resistant resin used in the present invention has a heat distortion temperature of 180°C.
Examples of the above materials that can be injection molded include polyetherimide, polyether sulfon, and the like.

In the present invention, a thermosetting resin composition is laminated on the surface of a substrate made of the heat-resistant resin and cured, and in order to obtain a magnetic disk from the obtained magnetic disk substrate, chromium, rhodium, etc. are added to the substrate surface. Since metal is vapor-deposited, sputtered, etc., it is preferable that the dimensional stability of the substrate heated in these processes is excellent and that the surface precision does not deteriorate.
limited to the above.

The above board is molded by injection molding,
Any conventionally known method may be used for injection molding, but
Since the surface of the substrate is preferably smooth, injection molding is preferably performed using a mold with a smooth surface.

Further, a filler may be added to the heat-resistant resin in order to impart strength, dimensional stability, heat resistance, etc. to the substrate.

Examples of the filler include powders such as carbon, alumina, silicon dioxide, mica, talc, calcium silicate, silicon carbide, calcium carbonate, carunium titanate, calcium sulfate, calcium titanate fiber, carbon fiber, aramid TA fiber, Examples include fibers such as cellulose fibers, and as the diameter and length of the wax powder and fibers increase, the surface smoothness of the substrate deteriorates, so the diameter is preferably 1 μm or less and the length is preferably 100 μm or less. Also, if the amount of filler added is small, it will not be effective, and if it is large, the surface smoothness will decrease, so heat resistant resin 10
It is preferable to add 5 to 100 parts by weight per 0 parts by weight.

In the present invention, a thermosetting resin composition is applied to the surface of the substrate. The resin layer is required to have excellent adhesion to the substrate, to be able to deposit or sputter chromium, rhodium, etc. on the surface of the resin layer, and to have good surface precision. A thermosetting resin composition consisting of an epoxy resin and a polyvarabinylphenol resin is used. As the epoxy resin, glycidyl ether type epoxy resins such as bisphenol A type, novolac type, and bisphenol F type are preferably used. .

The above-mentioned polyvinylphenol resin is one obtained by polymerizing paravinylphenol, parapropenylphenol, etc., and includes, for example, the product name Resin M manufactured by Maruzen Sekiyu Co., Ltd.

Regarding the ratio of the above epoxy resin and polyvarabinylphenol resin, as the ratio of epoxy resin increases, the heat resistance decreases, and as the ratio of polyvarabinylphenol resin increases, it becomes brittle, and the adhesion to the substrate and surface smoothness decrease. Therefore, it is preferable that the weight ratio is lO:1 to 10:12, and it is preferable that the epoxy group and the hydroxyl group are added in approximately equivalent amounts.

It is preferable to add a curing accelerator and a surfactant that lowers surface tension to the thermosetting resin composition in order to adjust the curing time and improve adhesion to the substrate, heat resistance, and surface precision.

Examples of the curing accelerator include imidazoles, amines, which are generally used as curing accelerators for epoxy resins,
Amides, boron compounds, etc., including tertiary amines such as tris(dimethylaminomethyl)phenol, dimethylaminomethylphenol, and boron trifluoride complex salts such as boron trifluoride piperidine complex salts and boron trifluoride dicyclohexylamine salts. is preferred. The amount of the curing accelerator to be added may be appropriately determined depending on the desired curing speed, curing temperature, etc., but generally 0.5 parts by weight per 100 parts by weight of the epoxy resin.
~3 parts by weight is added.

The above-mentioned surfactant may be one that lowers the surface tension of the thermosetting resin composition, and includes, for example, a fluorine-based surfactant, a silicone tea activator, etc., and the amount added is 100 parts by weight of the epoxy resin. In the present invention, the thermosetting resin composition is laminated and cured on the surface of the substrate, but it is generally not more than 2 parts by weight. , so that the surface smoothness after curing is excellent, the solid content is 20 ~ 20 with a solid solvent.
Preferably, it is diluted to 50 gb, viscosity (20°C), 20-200 cps.

Examples of the above-mentioned troweled solvents include methyl ethyl ketone,
Methyl isobutyl ketone, diacetone alcohol, ethyl cellosolve, ethyl cellolyl acetate, acetic acid glycol ether, succinic acid ester, toluene, xylene, etc.

Also thermosetting TS! Any method may be used to layer the fat composition, such as reverse roll coating, knife coating, spray coating, spin coding, dipping, etc., to ensure uniform film thickness and high surface precision. The spin code method is preferable for obtaining this.

In the spin cord method, the thermosetting resin composition may be dropped while rotating the substrate, or the thermosetting resin composition may be dropped onto the substrate and then the substrate may be rotated.

The rotation speed and rotation time may be appropriately determined depending on the viscosity of the resin composition to be laminated, the thickness of the layer, etc., but generally the rotation speed is 100 to 2000 rotations, and the rotation time is 20 seconds to 3.
The thermosetting resin composition is dripped onto a substrate rotating at a low speed of about 100 to 300 rpm from the outer circumference toward the inner circumference, and rotated for 10 to 30 seconds to coat the entire substrate surface. After dispersing with the resin composition, 500 rp
The thermosetting resin composition layer is formed by rotating at a high speed of m or higher for 20 to 60 seconds to remove excess resin composition.

In addition, thermosetting resin compositions are cured after lamination.
Curing is preferably carried out after the solvent has volatilized, that is, for example, after heating to 80 to 150°C to ignite the solvent,
It is preferable to heat and harden at a temperature of 0° C. or higher and lower than the heat deformation temperature of the substrate.

When the above-mentioned thermosetting resin composition becomes thick, the adhesion with the substrate decreases and pinholes and bubbles are likely to form.On the other hand, when the thermosetting resin composition becomes thin, the surface precision cannot be improved.
It is preferable that

〔Effect of the invention〕

The structure of the method for manufacturing a magnetic disk substrate of the present invention is as described above, and since a thermosetting resin composition is laminated and cured on the surface of an injection-molded substrate, it can be manufactured easily and with high productivity. . In addition, the obtained magnetic disk substrate is made of a heat-resistant resin with a heat deformation temperature of 180'C or more, and the substrate is made of a heat-resistant resin with a heat deformation temperature of 180'C or higher, and the surface of the substrate is laminated! Since the layer of the cured thermosetting resin composition is made of epoxy resin and polybarabinylphenol resin, the substrate and the layer of III compound are tightly adhered, and the heat resistance, strength, durability, etc. It has excellent surface precision (smoothness).

Therefore, by laminating metals such as chromium, rhodium, etc. by vapor deposition, sputtering, etc. on the hardenable resin composition layer of the magnetic disk substrate obtained in the present invention, it is possible to easily produce a magnetic disk that can handle high density. [Example] Next, the present invention will be described in detail.

Examples 1 to 5 Predetermined amounts of polyethersulfone, polyetherimide and potassium titanate fibers (diameter 0.2
~0.5μ, length 10~20μ) to create pellets, and the resulting pellets were fed to an injection molding machine to perform injection molding to form pellets with an outer diameter of 130M, an inner diameter of 40M+, and a thickness of 1.5μ. A 9m 5+1 board was obtained. The surface smoothness of the obtained substrate was measured using a stylus type surface roughness meter according to JIS B 0601-1970, and the average surface roughness Ra and maximum value Rmax are shown in Table 1.

After the obtained substrate was thoroughly degreased and washed and dried, it was fed to a spin cord machine, and thermosetting resin composition 10F having the composition shown in Table 1 was dropped onto the substrate, and the initial rotation speed was 20 Or
Rotate the substrate for 20 seconds at pm followed by 1000 rpm
It was rotated for 30 seconds and spin coded. Next, it was dried at 120°C for 1 hour and then cured at 170°C for 2 hours to obtain a magnetic disk substrate. In addition, the viscosity of the thermosetting resin composition and
Table 1 shows the thickness of the layer of the resin composition.

The surface smoothness of the obtained magnetic disk substrate and the adhesion between the substrate and the resin composition layer were measured and the results are shown in Table 1. Adhesion was measured according to JIS D 0202 using a cross-cut tape peeling force.

Further, in order to check the heat resistance of the obtained magnetic disk substrate, the obtained magnetic disk substrate was subjected to a heat resistance test at 160° C. for 6 hours, and the surface smoothness and adhesion were measured. The results are shown in Table 1. There was also no change in appearance.

(Left below) Table 1 (1) Manufactured by Sumira Chemical Co., Ltd., trade name Pictrex 360
0G (ri) Manufactured by Engineering Plastic Co., Ltd., product name: Ultem 1000 (3) Bisphenol-type epoxy resin, manufactured by Yuka Shell Co., Ltd., product name: Epicoat 828, epoxy fi190 (4) Novolac-type epoxy resin, manufactured by Yuka Shell Co., Ltd., product name: Epicoat 154, Epoxy 1 (6) Manufactured by Maruzen Petrochemical Co., Ltd., trade name Resin M1 hydroxyl group j1120 (6) Manufactured by Sumira 3M Co., Ltd., product name Florado C-
430

Claims (1)

[Claims] 1. A thermosetting resin composition made of an epoxy resin and a polyvinylphenol resin is laminated on the surface of an injection-molded substrate made of a heat-resistant resin with a heat distortion temperature of 180°C or higher. A method of manufacturing a magnetic disk substrate, which comprises curing the substrate. 2. The method for manufacturing a magnetic disk substrate according to claim 1, wherein the heat-resistant resin is polyetherimide or polyethersulfon. 3. The method for manufacturing a magnetic disk substrate according to claim 1 or 2, wherein the ratio of the epoxy resin to the polyvarabinylphenol resin is 10:1 to 10:12 by weight. 4. Claim 1 in which the lamination method is a spin coating method
3. A method for manufacturing a magnetic disk substrate according to item 2, item 2, or item 3.