JPS62238723A - Manufacture of disk base - Google Patents

Abstract

PURPOSE:To cover both surfaces of a core material with uniform thickness resin layer by preventing deformation of the core material, by a method wherein a positioning protrusion of a mold is inserted into a positioning hole of the disklike core material having a resin circulation hole on the central part and molten resin is charged into a cavity by pressing the core material from both the surfaces. CONSTITUTION:A positioning pin 25 of a stationary mold 11 is inserted into a positioning hole 32 of a core material 30. Sprue 17 is filled with molten resin through an injection machine in a mold clamping state, the molten resin arrives at the central part of a cavity 15, abuts against a bushing 18 and ejector pin 19 through a resin circulation hole 31 of the core material 30 and charged toward the fringe of the cavity 15 through a space among the core material 30 and each of mold surfaces 13a, 14a. Therefore, injection pressure is hardly applied to the surface of the core material 30 and a deformation can be prevented. As both surfaces of the core material 30 are pressed by press pins 26, 28, the core material 30 can maintain a state wherein the same runs parallel with both the mold surfaces 13a, 14a and a resin layer 52 covering both the surfaces of the core material can be made into a uniform thickness extending over the whole surface.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method of manufacturing a substrate such as a magnetic disk.

(Prior Art) Aluminum is generally used for the substrate of a magnetic disk. However, since the recording surface of a magnetic disk requires highly precise smoothness, aluminum substrates require a process of grinding and polishing to achieve a mirror finish, resulting in poor productivity.

Therefore, a technique for injection molding magnetic disk substrates using resin has been developed. The magnetic disk substrate made of Tate 1 resin obtains smoothness by transferring the mirror-finished surface of the mold to the molten resin, so high productivity can be achieved without the need for grinding and polishing.

However, this resin magnetic disk substrate is subject to thermal deformation.
It had a major drawback, probably due to moisture absorption and deformation.

Developed from the above perspective, Japanese Patent Application Laid-Open No. 60-1133
This is a technique described in Publication No. 24.

In this technique, a magnetic disk substrate is obtained by coating a core material of a non-magnetic metal such as aluminum with an It resin layer. This disk substrate has high productivity because it does not require grinding and polishing, and the core material prevents thermal deformation and moisture absorption deformation, so it has the advantages of both the aluminum and resin magnetic disk substrates mentioned above. We are prepared. The method for manufacturing the disk substrate described in the above publication will be described below with reference to FIGS. 6 to 9.
This will be explained with reference to the figures.

A mold 10' used for manufacturing a disk substrate has a pair of circular mold halves 11' and 12'. Circular recesses 13' and 14' of the shape yFi are formed on mutually opposing surfaces of these mold halves 1F and 12'. A runner 17' is formed in one half of the mold 11' at a position offset from the center. A circular convex part 100 is formed in the center of the concave part 14' of the mold half 12' on the main side, and four fixing pins 28' are provided around the convex part 100. A positioning pin 25' is provided on the top surface of the bottle 28'.

The core material 30' has a resin flow hole 31' having a diameter larger than the first convex portion 100 in the center, and has a positioning hole 32' around this hole 3B.

Then, with the mold half 12' placed horizontally, the positioning pin 25' is inserted into the positioning hole 32' of the core material 30'.
is inserted and this core material 30' is placed on the fixing pin 28'.

Next, the mold half 11' is placed on the mold half 12'.

In this state, the convex portion 100 of the mold half 11' is
It hits 2'. The core member 30' is in contact with the fixing pin 28' and the positioning pin 25', but the recesses 13', 14
' away from the inner surface of the cavity formed by.

Next, the cavity is filled with molten resin from the runner 17'. As a result, a molded article 40' shown in FIG. 7 is obtained. This molded product 40' has a disk shape with a hole 51' having a standard diameter in the center, and has a runner portion 42' corresponding to the runner 17'. Then, this runner section 42' is cut out to obtain a disk substrate 50' shown in FIG. 8. As shown in FIG. 9, this disk substrate 50' has a core material 30' and a resin layer 52' covering the core material 30'.

(Problems to be Solved by the Invention) The above technology has the following drawbacks. That is, a protrusion 100 for obtaining a hole 51' having the standard diameter of the disk substrate 50' is formed in the center of one mold half 12', and a protrusion 100 is formed in the center of one mold half 12'.
00 is applied to the mold half body 11' of the pond, the runner 17' must be formed at a position offset from the center of the cavity. The pressure of the resin is applied directly to the surface of the core material 30', and the core material 30
′ could be deformed. In addition, the molten resin flows from the runner 17', hits one surface of the core material 30', spreads here j), and merges on the other surface of the core material 30', so that a weld line is formed in the recording area of the resin layer 52'. It also had the disadvantage that it formed.

In addition, since the core material 30' is supported by simply inserting the positioning hole 32' into the positioning pin 25' and placing it on the fixing pin 28', the support is unstable, and when filling with the resin, The core material 30' is tilted and the resin layer 52 has a uniform thickness.
′ could not be formed in some cases.

Furthermore, since the fixing pin 28' comes into contact with the core material 30' during molding, the lower surface of the molded product 40' shown in FIG.
There is a portion of the core material 30' where the resin layer 52' is not formed and the core material 30' is exposed, which has the disadvantage of narrowing the area of the recording surface. Furthermore, it was difficult to flatten the area after cutting out the runner 42' with high precision, and this area could not be used as a recording surface either. In addition, these marks caused a poor appearance.

(Means for Solving the Problems) This invention has been made to solve the above problems, and its gist is to form a flat circular cavity in a pair of mold halves, and to form a flat circular cavity in one mold half. A runner is formed in each mold half that communicates with the central part of the cavity, and in the vicinity of the runner, both mold halves are provided with pressing convex portions facing each other, and at least one metal A mold is prepared in which a positioning convex portion is provided on the mold half, and a disc-shaped mold having a resin flow hole in the center and a positioning hole near the resin flow hole is prepared. Prepare a core material, insert the positioning convex part into the positioning hole of the core material, close the mold by pressing the core material from both sides with the pressing convex part, and insert the mold from the runner into the cavity. Forming is performed by filling the molten resin into the molten resin, and then a runner forms the shape IF1. The central part of the molded product including the molded runner part and the traces of the positioning convex part and the holding convex part is cut and removed to obtain a disk substrate having a hole of a standard diameter in the center. A method of manufacturing a disk substrate is provided.

(Operation) The mold is closed with the core material set in the cavity, and molten resin is filled into the cavity from the runner formed in one half of the mold. At this time, since the molten resin advances from the center of the cavity along the surface of the core material, almost no pressure of the resin is applied to the surface of the core material, and deformation of the core material can be prevented. Also,
Since the molten resin joins near the periphery of the cavity, it is possible to prevent weld lines from forming in the recording area of the resin layer. Furthermore, since the holding convex parts protruding from both mold halves hold down both sides of the core material, it is possible to prevent the core material from tilting during resin filling, and maintain a state parallel to the mold surfaces of both mold halves. Therefore, both sides of the core material can be coated with a resin layer of uniform thickness.

After the above molding, the central part of the molded product is cut and removed to obtain a disk substrate completely free of traces of the runners, positioning convexities, and pressing convexities formed by the runners. I can do it.

(Example) Hereinafter, the method of this invention will be explained with reference to FIGS. 1 to 5.

Reference numeral 10 in FIGS. 1 and 2 is an injection mold for carrying out the present invention, and this mold 10 has a fixed mold 11 (mold half) and a movable mold 12 (mold half). have. The mold 10 is of a so-called horizontal type, and a movable mold 12 moves horizontally with respect to a fixed mold 11 to open and close the mold 1, and parting surfaces 11a and 12a are vertical.

The fixed mold 11 and the movable mold 12 have shallow circular recesses 13 and 14, respectively. 1. This recess 13.14
has mold surfaces 13a and 14a that are mirror-finished with high precision. When the mold is clamped, a flat circular cavity 15 is formed by these recesses 13 and 14.

The fixed mold 11 has a sprue bush 1 in its center.
6, and this sprue bush 16 has a sprue 17 (runner) shaped like J&. Moreover, the blue 17 continues to the center of the cavity 15.

In addition, the movable mold 12 has an ejecting bush 18 in its center, and an ejecting pin 19 passes through this bushing 18.
are set back from the mold surfaces 13a, 14a, so that the central part of the cavity 15 is wider than the peripheral part, and steps 20 and 21 are formed at the boundaries thereof.

In the surface of the sprue bush 1G of the fixed mold 11, a total of three positioning pins 25 (positioning protrusions) are embedded and fixed at equal intervals around the blue 17,
These positioning pins 2S project horizontally in the direction of the movable mold 12. Moreover, there are a total of 3 pins between these positioning pins 25.
A book holding bottle 26 (holding convex portion) is embedded and fixed, and protrudes in the direction of the movable mold 12. Ikegata, the fixed mold 11 is attached to the surface of the protruding bush 1B of the movable mold 12.
An escape hole 27 is formed at a position facing the positioning pin 25 of the fixed mold 11, and a hole 3 is formed at a position facing the holding pin 26 of the fixed mold 11.
A book holding bottle 28 (holding convex portion) is embedded and fixed and projects horizontally in the direction of the fixed mold 11.

1 and 2 is a core material used in the method of the present invention, and this core material 30 is made of metal aluminum, ceramics, F
It is made of non-magnetic material such as RP and has a thin disk shape. A large hole 31 for resin flow is provided in the center of the core material 30.
are formed in the vicinity of this hole 31, three holes are formed at equal intervals.
Small positioning holes 32 are formed at certain locations.

A magnetic disk substrate is manufactured using the above-described mold 10 and core material 3θ. First, the positioning pin 25 of the fixed mold 11 is inserted into the positioning hole 32 of the core material 30. This results in
The core material 30 is accurately set in the fixed mold 11. Next, the movable mold 12 is moved in the direction of the fixed mold 11, and the mold 10i:
close. As a result, both sides of the vicinity of the central hole 31 of the core material 30 are attached to the holding pins 26 of the fixed mold 11 and the movable mold 12.
28. As a result, the core material 30 is vertically arranged in the cavity 15, and both mold surfaces 13a, 1
It is an equal distance away from 4a. Note that the positioning pin 25 enters into the escape hole 27.

In the mold clamped state, the blue 17 is again filled with thermoplastic or thermosetting molten resin from the injection machine.

This molten resin reaches the center of the cavity 15 and reaches the core material 30.
The bush 1 of the movable mold 12 passes through the hole 31 for resin flow.
8 and protruding pin 19, this cavity 1
5 is filled toward the periphery of the cavity 15 through between the core material 30 and each mold surface 13a, 14a.

In this way, melt the resin from the center of the cavity 15 to the core material 3.
Since the injection proceeds along the plane 0, almost no injection pressure is applied to the plane of the core material 30, and deformation of the core material 30 can be prevented.

In addition, since both sides of the core material 30 are held down by the holding pins 26 and 28, it is possible to prevent the core material 30 from tilting during resin filling, and to maintain a state parallel to both mold surfaces 13a and 14a. For this reason, the resin N52 covering both sides of the core material 30 is used as described below.
can be made to have a uniform thickness over the entire surface.

Furthermore, by inserting the positioning pin 25 into the positioning hole 32 of the core material 30, the core material 30 can be moved to the mold surface 13a,
Since movement in the direction parallel to the core material 14a is prohibited, the distance between the outer circumferential edge and the surface of the cavity 15 can be maintained constant, and as will be described later, the resin layer 5 covering the outer circumferential edge of the core material 30
2 can be made to have a uniform thickness over the entire circumference.

Since the molten resin travels from the center of the cavity 15 to both sides of the core material 30 and joins near the periphery of the cavity IS, it is possible to prevent weld lines from forming in the recording area of the resin layer 52. Comes off.

In addition, the molten resin passes through the positioning pin 25 and the holding pin 26.
．． Once I reached 28, I reached 1 minute! However, in this embodiment, the center of the cavity 15 is wide, and as it progresses from the center to the periphery, it passes through steps 20 and 21. At this time, shear heat generation occurs in the molten resin, so the pins 25, 26.
It is also possible to prevent the occurrence of weld lines caused by 281.

After the molten resin has solidified or hardened within the mold 10, the movable mold 12 is moved to open the mold, and the protruding ejecting pin 19
The molded product 40 shown in FIG. 3 is taken out by protruding. This molded product 40 has a disk shape, and includes a thick interior 41 formed in the center thereof, a sprue portion 42 (runner section) formed in the center of the thick interior 41, and a sprue joint in the thick interior 41. It has holes 43 formed at six locations around the portion 42. The thick interior 41 is formed by the wide central part of the cavity 15, the sprue portion 42 is formed up the sprue 17, and the hole 43 is that formed by the locating pin 25 and the hold-down pin 26,28.

Then, by cutting the periphery of the thick inside 41 of the molded product 40 into a circular shape using a laser beam (the diameter of the cut inside is slightly larger than the thick inside 41), this thick inside 41 is removed from the molded product 40, and the fourth A magnetic disk substrate 50 having a hole 51 with a standard diameter in the center as shown in the figure is obtained.

The obtained magnetic disk substrate 50 is as shown in Figure @5.
Both surfaces and the outer peripheral edge of the core material 30 are coated with a resin layer 52. There are no traces of the sprue portion 42, positioning pins 25, holding pins 26, 28, etc. on the disk substrate 5().

The method of the present invention is not limited to the above-mentioned embodiments and can be modified in various ways, and can be applied to, for example, the substrate of an optical disc.

This is achieved mainly by using a molding method such as transformer 77 molding instead of injection molding.

The positioning convex portion and the holding convex portion may be integrally formed on each mold half.

The positioning projection may be formed on the top surface of the holding projection. In this case, the height of the positioning projection is equal to or lower than the thickness of the core material.

The mold consists of two mold halves separated into upper and lower halves, and is also a so-called vertical mold.

The mold may have multiple cavities.

In this case, the runners are configured to branch in the middle and communicate with the center of the cavity.

(Effects of the Invention) As explained above, in the method of this invention, since the resin is filled from the center of the cavity, deformation of the core material can be prevented, and weld lines can be prevented from occurring in the recording area of the resin layer. . Mainly, since the core material is pressed from both sides by the pressing convex portions, it is possible to prevent the core material from tilting and to cover it with a resin layer of uniform thickness. By cutting and removing the central part of the molded product, including the traces of the runners, holding projections, and positioning projections, a disk substrate with a hole of a standard diameter is obtained. The surface area is wide and the appearance is good.

[Brief explanation of drawings]

1 to 5 show one embodiment of the present invention, FIG. 1 is an exploded perspective view of the mold and core material, FIG. 2 is a sectional view of the mold and core material during mold clamping, and FIG. The figure is a perspective view of a molded product obtained by injection molding, FIG. 4 is a perspective view of a disk substrate as a final product, and FIG. 5 is a sectional view of the same. 6 to 9 show conventional examples. FIG. 6 is an exploded perspective view of a mold and core material, FIG. 7 is a perspective view of a molded product obtained by injection molding, and FIG. 8 is a perspective view of a molded product obtained by injection molding. The figure is a perspective view of a disk substrate as a final product, and FIG. 9 is a sectional view thereof. 10... Mold, 11... Fixed mold (mold half), 12
...Movable mold (mold half), 15...Cavity, 1
7... Sprue (runner), 25... Positioning pin (
positioning protrusion), 26, 2f3... holding pin (holding protrusion), 30... core material, 31... hole for resin flow, 32... hole for positioning, 40... ·Molding,
41... Thick interior (center part) of molded product, 42... Part of sprue (runner formed by runner), 43... Hole (trace of positioning convex part and holding convex part) ), 50・
... Disk board, 51 ... Hole with standard diameter

Claims (1)

[Claims] (1) A flat circular cavity is formed between a pair of mold halves, a runner is formed in one mold half that communicates with the center of the cavity, and a runner is formed in the vicinity of this runner. A mold is prepared in which both mold halves are provided with holding convex parts facing each other, and at least one of the mold halves is provided with a positioning convex part, and the central part is provided with a resin distribution part. Prepare a disk-shaped core material that has a hole for resin flow and a positioning hole near the hole for resin flow, insert the positioning convex part into the positioning hole of this core material, and The mold is closed by pressing the material with the pressing convex parts from both sides, and the molding is performed by filling the cavity with molten resin from the runner. After this, the runner is positioned with the runner formed by the runner. 1. A method for manufacturing a disk substrate, comprising: obtaining a disk substrate having a hole of a standard diameter in the center by cutting and removing the central portion of a molded product including traces of a presser convex portion and a presser convex portion.