JPH0225311A - Mold of disc substrate for high density recording on both sides - Google Patents

Abstract

PURPOSE:To make it possible to simultaneously mold pit trains for tracking on both sides by a method wherein molding is done under the conditions that the inner edge of each stamper, which is held on the surface of a mirror platen is pinched by the outer peripheral flange of a fitting ring, while its outer peripheral edge is pinched by the flange of a press ring. CONSTITUTION:Each mirror platen 3 (or 15), onto which a stamper 7 (or 18) is mounted, is fixed through a sleeve 4 (or 16). Further, the inner peripheral edge of the stamper is pinched by the annular flange 8a (or 17a) of a fitting ring 8 (or 17), which is fitted onto the outer peripheral surface of the sleeve and, at the same time, the outer peripheral part of the stamper is pinched by the flange 9a (or 19a) of an outer peripheral press ring 9 (or 19) for molding. Accordingly, pit train signals can be produced by one process on both the sides of a disc substrate. In addition, the parallelism between the mirror platen and the sleeve face is preferably obtained by highly accurately finishing the large diametral part 4a (or 16a) of the sleeve and fitting said part normal to the mirror platen. And, the formation of a tapered stepped part 12 (or 21) on the opposed surfaces of the outer peripheral press rings of the stampers is preferable as the aligning means of the mirror platens on a fixed side 1 and on a movable side 4.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a mold for forming a disk substrate for high-density recording in which tracking reference signals are formed by pit rows on both sides of a magnetic disk.

(Prior art) When high-density recording and reproduction is performed on a magnetic recording medium such as a magnetic disk, it is necessary to accurately trace a magnetic head over a narrow recording band. A pit array for a capacitance change signal is formed by using a conventional method. (Unexamined Japanese Patent Publication No. 571,
67172, JP 61-22415, JP 61-131279) Conventionally, the following methods have been used to form pit rows on synthetic resin substrates.

(2) In the case of a capacitive video disk (VHD), a stamper is provided on both sides of the mold, and a disk substrate with signal pits formed is obtained by compression molding or injection compression molding on both sides simultaneously. That is, the gap between both stampers of the mold is made wider than the thickness of the disk substrate to be molded, molten synthetic resin is introduced there, and then the gap between both stampers is narrowed to the thickness of the disk substrate to be molded. This method involves cooling and solidifying the resin. However, with disks manufactured by changing the distance between the stampers when solidifying the resin, it is not possible to obtain a shape accuracy suitable for tracing with the magnetic head, and this molding method requires a long molding cycle. Furthermore, since a deburring process is required, productivity is low and it is unsuitable for manufacturing magnetic disk substrates.

■ Compact disc (CD), write-once optical disc,
Optical disks such as magneto-optical disks are molded by injection molding using a mold with a single-sided signal stamper specification.

This method uses a mold with a signal stamper on one side and a mirror surface on the other side. Then, a disk with signals formed on only one side is molded. In the case of an optical disc that can be used on both sides, it is generally made by bonding two discs together with the signal side facing inside. That is, in the case of optical discs, it is theoretically necessary to bond two discs together, and it is not possible to create an optical disc that can be used on both sides with -1 molding process. On the other hand, in the manufacture of magnetic disk substrates, the precision of the shape of the substrate is strictly required, and from the viewpoint of productivity, it is not appropriate to employ such a complicated process.

(Problem to be solved) The present invention provides a magnetic disk substrate that can be used on both sides.
This method was developed in view of the need for a molding method that can simultaneously form tracking pit rows on both sides and that can satisfy the positional accuracy of the pit rows and the shape accuracy of the disk substrate.

The present invention provides a stamper on both sides of a mold for forming a disk substrate.
To provide a mold for injection molding, which can be attached to mold tracking pits on both sides of a substrate at once when molding the substrate.

In order to accurately emboss and record pit patterns on both sides of the disk, the positions of the stampers attached to each of the fixed mold and the movable mold must be adjusted individually and relative to the shaft hole or the axis of the stamper signal. It is necessary to fix it accurately.

In addition, for magnetic disk boards, it is especially important that the surface of the disk board does not run out when it is attached to a rotation motor and the disk is rotated. (the surface to which the magnetic disk is fixed) must be finished with high precision.

(Structure) The mold of the present invention has an inner edge of a stamper supported on a surface of a mirrored plate attached to a mold base, which is held between an outer periphery flange of a fitting ring, and a presser which fixes the outer periphery of the stamper to the outer periphery of the mirrored plate. It consists of stamper-mounted mirror plates that are supported under pressure by the flanges of the ring, and are installed vertically facing each other with a common center axis, and the fitting sleeve on the fixed mold side has a sprue bush. A cut punch connected to a hydraulic cylinder is inserted into the stepped sleeve on the side of the movable mold, which is slidably inserted therethrough.

It is fitted with high precision into the inner circumferential side of the mirror plate and the inner circumferential side of the stamper holding fitting ring so that the mirror surface of the mirror plate and the end surface of the sleeve are parallel to each other.

The end surface of the sleeve is finished to the same level of surface roughness and flatness as a mirror surface.

The sleeve is located on the inner periphery of the mirror surface plate whose position is regulated with high precision in the mold, and is provided in order to obtain a surface with parallelism, area degree, and flatness equivalent to that of the mirror surface disk. This allows a flange surface with excellent flatness to be formed at the center of the magnetic disk substrate to be molded.

Furthermore, each opposing surface of the stamper outer peripheral edge presser ring has a first
The abutting surface and the second abutting surface are configured to abut each other via position regulating tapered steps. Note that the number of contact surfaces and the number of tapered steps are arbitrary.

Further, as another mirror surface plate position regulating means, one in which a plurality of taper pins and taper bushes are arranged around a flat surface holding ring can also be used.

Further, in order to prevent the stamper and each mirror plate supporting the stamper from moving in the direction of the rotating surface, a rotation preventing means is provided on the inner circumferential portion of the outer periphery presser link.

(Example) (1) is the fixed side base, (2) is the injection end surface that is in contact with the material injection nozzle (not shown), (3> is the mirror surface plate attached to the fixed side base (surface roughness RmaxO, 03 μm > , (
4> is a sleeve (nest) having a large diameter part (4a) and a small diameter part (4b). (5) is a sprue bush that moves axially, and has a resin flow path (6) bored in the center and slides within the sleeve (4).

The large diameter part of the sleeve is finished with high precision to ensure parallelism with the mirror surface, and is fitted into the mirror surface at right angles. This provides parallelism between the mirror surface and the sleeve surface.

(7) is an annular first skumper sheet that is tightly fixed to the surface of the mirror disc, and its inner edge is fitted with a fitting ring (8).
The outer peripheral edge is held under pressure by the flange (9a) of a retaining ring (9) which is fitted and fixed to the mirror plate. Note that the fitting ring (8) is fixed by fixing means from the side of the mirror plate.

The external shape of the retainer ring has a step (lO
) is provided to form a first abutment surface (11), and further a second abutment surface (13) is provided via a tapered step (12).

(14) is the movable base, (15) is the mirror plate, (16) is the sleeve, (16a) is the large diameter part, (16b) is the small diameter part,
(17) is a fitting ring and has the same shape as (8) above.

(18) is the second stamper sheet.

The inner edge of the second stamper sheet is attached to the flange (1) of the inset ring.
7a,), and the outer peripheral edge is held by a presser ring (19).

The outer surface shape of the holding ring corresponds to the surface of the first stamper sheet holding ring (9), and the shape corresponds to the surface of the first stamper sheet holding ring (9).
20) and a flange for holding the second stand bar (
19a), and a second contact surface (22) is formed via a tapered step (21).

(23) is a cut punch, which is a hydraulic cylinder bottom cover (
24) and a movable base (14), the piston (25) of a hydraulic cylinder is connected to the piston (25).

(26) is an extrusion pin that passes through the piston (25) and is inserted into the center hole (23a) of the center hole cut punch (23).

(27) and (28) are pressure oil inlets for cylinder operation.

The timing of punching the center hole can be adjusted by supplying hydraulic pressure during the resin filling and cooling steps during the molding cycle so as to obtain a suitable molded product.

In FIGS. 4 and 5, reference numeral (30) denotes a stamper rotation prevention jig, and a convex portion (31 ) and is fixed to either the mirror plate or the presser ring.

FIG. 6 shows another example of the alignment means for the fixed (lI!l) mirror plate (3) and the movable mirror plate (15), in which 3 to 4 pieces are installed on the circumference. A taper pin (40) and a taper bush (42) are provided, and the axis is defined by the taper shaft (41) of the taper pin fitting into the inner surface (43) of the taper bush.

In this case, stamper holding ring (9) (one)
The alignment steps (12) and (21) are not necessary on the surface of the contact surface, and the contact surfaces (44) and (45) can be formed as flat surfaces.

(Operations and Effects) In the present invention, the mirror plate to which the stamper is attached is fixed via the nest, and the inner circumferential edge of the stamper is further held between the annular flange of the fitting ring fitted to the outer circumferential surface of the nest. Since the outer periphery of the tamper is sandwiched and molded between the flanges of the outer periphery link, pit row signals can be formed on both sides of the disk substrate in one step.

The large diameter part of the removed sleeve is finished with high precision and is fitted into the mirror surface at right angles, so that parallelism between the mirror surface and the sleeve surface can be obtained.

In addition, as a means for aligning mirror surfaces on the fixed side and the movable side, a tapered stepped portion is formed on the opposing surface of the stamper outer circumferential ring, or a plurality of taper pins and taper bushes are provided around the stamper. There is little center position deviation, and the positional relationship of pit rows on both sides can be accurately determined.

Furthermore, since a recess is formed on the outer periphery of the stamper and a rotation prevention jig is used to prevent rotation of the stamper, pit rows on both sides are recorded while maintaining accurate relative relationships in the disk rotation direction.

As a result, even during double-sided synchronized reproduction, the axial deviation of the signal center can be made extremely small, and reproduction can be performed with high precision.

The molding die of the present invention can also be applied to a case where groups (grooves) are used instead of pit rows as tracking reference signals.

[Brief explanation of the drawing]

FIG. 1 is an overall cross-sectional view of the mold of the present invention, FIG. 2 is a partially enlarged cross-sectional view showing the relationship between the stamper and the presser ring, FIG. 3 is a partially enlarged cross-sectional view showing the relationship between the insert ring and the stamper, and FIG. 4 is a plan view of essential parts of the stamper rotation prevention mechanism, FIG. 5 is a sectional view taken along the line A--A in FIG. 4, and FIG. 6 is a partial sectional view showing the other side of the mold alignment means. (3) (15) are mirror surfaces, (4) (16) are sleeves,
(7) and (18) are stampers, (9) and (19) are presser rings, and (12) and (21) are taper steps for alignment. Patent applicant Denki Kagaku Kogyo Co., Ltd. Representative Patent attorney Hiroshi Nakamura

Claims (5)

[Claims] (1) In a mold for molding a disk substrate with pit rows for tracking control on both sides of the disk, the inner edge of the stamper supported on the surface of the mirror plate attached to the mold base is held between the outer periphery flanges of the fitting ring, and The double-sided stamper is characterized in that the stamper-mounted mirror plate is configured such that the outer periphery of the stamper is supported under pressure by a flange of a presser ring fixed to the outer periphery of the mirror plate, and that the stamper-mounted mirror plate is installed vertically facing each other with a common center axis. Molding mold for high-density recording disk substrates. (2) On the inner diameter side of the mirror plate and on the inner diameter side of the fitting ring,
2. The molding die according to claim 1, wherein the sleeve is fitted in parallel to the mirror surface plate. (3) Each opposing surface of the stamper outer peripheral edge presser ring has at least a first abutting surface and a second abutting surface, and the first abutting surface and the second abutting surface are connected to each other through a tapered step. The molding die according to claim 1 or 2, wherein the molding die is arranged in series. (4) The molding die according to claim 1 or 2, wherein a plurality of pairs of taper pins and taper bushes are placed on the stamper outer peripheral edge press ring. (5) The molding die according to any one of claims (1) to (4), wherein rotation prevention means are provided on the outer peripheries of the stamper and the mirror plate, respectively.