JPS59180833A - Substrate for recording medium - Google Patents

Abstract

PURPOSE:To make the smoothening of the surfaces of a disk after working unnecessary by compression-molding ceramics or sintered metal into a substrate having a prescribed shape for a recording medium. CONSTITUTION:The cope 2 and the drag 3 of a metallic mold 1 have inner spiral grooves 7, 8, respectively. Steam or water is introduced from the inside inlets 9 of the grooves 7, 8, and it is discharged from the outside outlets 10. Alumina powder is kneaded with polyvinyl butyral and an adequate amount of an org. solvent, and the kneaded material is dried to obtain ceramic powder. This powder is filled into the cavity 4 in the mold 1, and it is compression- molded into a disk using the resin covering the alumina powder as a binder. The mold 1 is heated so as to allow the resin to act well as the binder during the pressing. Immediately before finishing the pressing, the mold 1 is cooled, and the strength is increased by sintering. A substrate having flat surfaces is obtd.

Description

Detailed Description of the Invention (a) Technical Field of the Invention The present invention relates to substrates for various recording media having a recording surface on the surface for recording and reproducing information using magnetism, light, and magneto-optics. The present invention relates to a substrate for a recording medium made of a substrate material such as ceramic or metal sintered body.

(b) Prior Art and Problems In a conventional magnetic disk substrate, a flat aluminum plate is processed into a predetermined disk shape, and then the surface is flattened using a lathe using a polynosy or a diamond cutting tool. This method has low material costs, but requires less polishing. Otherwise, the disks are set one by one on a lathe and processed, which requires a large number of processing steps and increases costs.

Also, this process is for the purpose of smoothing the disk surface.
It is not possible to pre-inject patterns such as servo information for track following onto the disk surface. Therefore, after the disk is made, all the tracks on the disk are written one by one using a servo track writer, which is a difficult task.

(C) Object of the Invention The object of the invention is to form a recording medium substrate into a predetermined shape using a ceramic or sintered metal by a compression and injection molding method or a compression injection molding method.

Another object of the present invention is to provide a recording medium substrate in which a servo information pattern is provided in advance on the substrate.

(d) Structure and object of the invention According to the present invention, there is provided a recording medium substrate on which a recording surface for recording and reproducing information is formed, the recording medium being formed of ceramic or sintered metal into a predetermined shape. This is achieved by using a board for

(e) Examples of the invention Embodiments of the present invention will be described in detail below with reference to the drawings.

Figure 1 shows the gold t used for molding the recording medium substrate of the present invention.
In the schematic diagram of <V, (A) is a cross-sectional view, and (→ is a plan view.

In the figure, 1 indicates a mold used in a compression molding machine, which is divided into an upper mold 2 and a lower mold 3, with a space (capity) 4 between the upper and lower molds 2 and 3. Oh,
5 is a lower mold surface, 6 is an upper mold surface, and 7 and 8 are grooves for passing steam and water for heating and cooling the mold, which are arranged in a spiral shape inside the upper and lower molds.

As shown in FIG. 1(B), the steam and water entering from the inner circumference 9 of the spiral grooves 7, 8 are discharged from the outer circumferential outlet 10 of the helical grooves 7, 8.

The cavity 4 formed between the upper and lower molds 2 and 3 is filled with ceramic powder made by the following method.

The description will be given by taking as an example a magnetic disk substrate manufactured by press molding (compression molding) under heating.

An appropriate amount of organic solvent is added to 97 parts by weight of alumina powder, 3 parts by weight of resin polyvinyl butyral which acts as a binder, and the mixture is kneaded in a ball mill for several days to produce a highly viscous paint. This paint is dried by a method such as vacuum drying to remove the solvent and obtain a ceramic powder whose surface is covered with 161 fat.

This powder is filled into the cavity 4 of the mold 1.

The resin covering the aluminum powder is used as a binder to compression mold it into a disk shape. A pressing force of 50 tons or more is required during molding. Further, in order for the resin to sufficiently act as a binder during pressurization, it is necessary to heat the mold 1. The heating temperature may be any number of times as long as the resin is denatured and the sintering time is affected.2 Heating is usually carried out at 100 to 140°C. It is better to cool down the mold 1 immediately before the end of the press for better product removal.

The final product that has been pressed in the manner described above is 150
It is sintered in a furnace at 0 to 1800℃ to increase its strength.
Obtain a peaceful substrate surface.

Furthermore, if a flat stamper with no information is placed on the mold surface, the life of the mold will be extended.

In addition, when creating a concavo-convex pattern on the substrate surface, the pattern is created on the surface of the mold, or a mold 11 having the same pattern on the surface as shown in FIG. 2 held in the upper mold 2 is used. and form it. This stamper 12 is made by transferring the original pattern on the master disc by a method such as plating. If this stamper 12 is further provided 7t on the lower mold 3, a substrate having an uneven pattern on both sides can be obtained. Note that in FIG. 2, parts common to those in FIG. 1 are designated by the same reference numerals.

The above embodiments of the present invention have been described by using the compression molding method used for molding plastics and the like in ceramic molding to obtain a substrate in a predetermined shape.

Injection molding methods other than compression molding, or compression/injection molding methods may be used. Furthermore, instead of ceramic molding, it is also possible to use a metal sintered body and obtain a substrate in a predetermined shape by the above molding method.

As mentioned above, a substrate formed by ceramic molding or sintered metal can be molded into a disk with an extremely smooth surface. It is inexpensive because it does not require processing. Furthermore, since a concavo-convex pattern such as servo information is preliminarily provided on the surface of the substrate by molding, there is no need to write patterns such as servo information using a servo trunk writer after making the disk as in the conventional method.

Furthermore, the aluminum used in conventional discs has two kinds of impurities added to it, such as wheat flour and magnesium Mg, in order to strengthen its mechanical strength. As shown in FIG. 3, there are holes (10 to 50 μm) 14 where iron Fl and magnesium Mg inclusions 13 remain or are removed, and these are all defects due to errors.The quality of the recording medium is improved. I was leaning against the wall. Since the mechanical strength of the substrate of the present invention is much greater than that of conventional substrates, these barriers to quality improvement are removed, and the quality of the recording medium can be improved by a t.

(1) Effects of the Invention As explained in detail above, the recording medium substrate of the present invention uses the method used for molding plastics, etc. to mold ceramics and metal sintered bodies to form a smooth and predetermined shape. Since we have obtained a disk, there is no need to process flat aluminum into a disk shape and smooth the disk surface as in the conventional method.
It's cheap.

Furthermore, since a concavo-convex pattern such as servo information can be previously provided on the surface by molding, there is no need to write patterns such as servo information using a servo track writer after making the disk as in the conventional method.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a mold used for molding the recording medium substrate of the present invention, in which (a) is a cross-sectional view, and (middle) is a plan view. FIG. 2 is a sectional view of a mold used for molding another recording medium substrate of the present invention, and FIG. 3 is a sectional view illustrating the surface condition of a conventional disc. In the figure, 1.11 is a mold, 2 is an upper mold, 3 is a lower mold, 4 is a cavity, 5 is a lower mold surface, 6 is an upper mold surface,
7 and 8 are grooves, 9 is an inlet, 10 is an outlet, 12 is a stamper,
13 and 14 are inclusions, 14 are holes, and 15 are disks. Figure 1 R Ino / Figure 21 Y, Figure 3

Claims (1)

[Claims] (A recording medium substrate formed from ceramic or sintered metal into a predetermined shape, on which a recording surface for recording and reproducing information is formed.)