JPH0768605A - Mold for molding recording disk - Google Patents

Abstract

PURPOSE:To provide a mold capable of taper-forming a center hole of a substrate for magneto-optical mini disks (MD-MO). CONSTITUTION:A cavity 23 of a form of a substrate 20 and a gate 63 of a ring form opened to a position corresponding to a side of the center hole 64 are formed between a closed fixed mold 21 and a movable mold 22. The fixed mold 21 has a sprue bush 33 with a function of a gate cutter to cut resin at a gate 63, which forms a side of the center hole 64. A tapered portion 65 is formed at a side of the sprue bush 65, and the formed center hole 64 is also tapered. A drive head of a playback system is also tapered in a matching form. In consequence, The tapered center hole helps its side closely contact the side of the drive head of the playback system and eliminate backlashes.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording disk molding die for injection molding a substrate of a recording disk such as a magneto-optical mini disk (MD-MO) with a resin.

[0002]

2. Description of the Related Art The MD-MO has a disk body built in a cartridge having a shutter, and is capable of both recording and reproduction. FIG. 8 shows the disc body 1
Is shown. The disc body 1 is a disc having a diameter of 64 mm, and has a center hole 2 in the center. A drive head 11 of the recording / reproducing apparatus is engaged with the center hole 2, and the disk body 1 rotates together with the drive head 11. Further, conventionally, the center hole 2 has a columnar shape, and the drive head 11 has a columnar portion 12 that enters the center hole 2 and a flange portion 13 on which the disk body 1 is placed. . Since the cylindrical portion 12 is inserted into the cylindrical central hole 2, the central hole 2 has a diameter slightly larger than that of the cylindrical portion 12, and the center hole 2 and the cylindrical portion 12 have side surfaces between them. A gap c is created. The recording / reproducing apparatus has a magnetic head 15 located above the disk body 1 and an optical pickup 16 located below the disk body 1. The magnetic head 15 and the optical pickup 16 are positioned so as to face each other in the vertical direction, and are integrally moved in the radial direction of the disk body 1 by driving a servo motor (not shown). The optical pickup 16 has an automatic focus adjustment mechanism.

Further, FIG. 7 shows a sectional structure of the disk body 1. As shown in the figure, from the bottom to the top, a 1.2 mm-thick substrate 3, which is a molded product of polycarbonate, a first dielectric film 4, a magnetic film 5, a second dielectric film 6, and a reflective film 7 are formed. And the protective film (sliding film) 8 form a layer. These films are formed by vapor deposition plating or the like. Further, in the disk body 1, a guide groove 9 is formed spirally from the center thereof as shown in FIG. The pitch p between the guide grooves 9 is about 1.6 μm. The guide groove 9 is formed by being transferred from the stamper when the substrate 3 is injection-molded in advance. A voice signal is recorded along the guide groove 9, but the guide groove 9 itself also forms an address signal.

The drive head 11 is used for both recording and reproduction.
The servo motor is controlled so that the disk body 1 is rotated by the driving of the disk drive and the continuously emitted laser light from the optical pickup 16 follows the guide groove 9. As shown in FIG. 6, the width of the guide groove 9 is narrowed or widened. This is a record of address information. That is, the intensity of the reflected light to be measured changes according to the difference in the ratio of the spot S of the laser light hitting the guide groove 9, and the address is read based on this. By reading this address, arbitrary access becomes possible. The recording is performed by magnetizing the magnetic film 5 with the N or S polarity along the guide groove 9 by the magnetic head 15 while performing the demagnetization in advance by heating with the laser beam. During reproduction, the optical pickup 16 reads the audio signal along the guide groove 9. This utilizes the fact that the polarization of the reflected light is different depending on the polarity of the magnetization.

[0005]

As described above, in the conventional MD-MO, the center hole 2 of the disk body 1 has a columnar shape, which causes the following problems.
That is, since the cylindrical portion 12 of the drive head 11 is inserted into the cylindrical central hole 2, the central hole 2 has a cylindrical portion.
The diameter must be slightly larger than 12. Therefore, radial rattling occurs between the disk body 1 and the drive head 11. This rattling is caused by the optical pickup 16
Is made to follow the guide groove 9. That is, the radial deviation of the disk body 1 is obtained from the reading of the guide groove 9, and this is corrected by the servo motor. However, this complicates the servo mechanism. At the same time, there is a restriction on making the pitch between the guide grooves 9 small, and therefore, a restriction on high density recording of audio signals.

The present invention is intended to solve such a problem, and by improving the shape of the central hole, the servo mechanism for driving the optical pickup can be simplified and the signal recording density can be increased. The improved shape of the central hole facilitates, and
It is an object of the present invention to provide a recording disk molding die that can be formed without adversely affecting a molded substrate.

[0007]

In order to achieve the above object, the present invention relates to a recording disk molding die for molding a disk-shaped recording disk substrate having a central hole, and a cavity having the shape of the substrate. And a fixed die and a movable die that open and close to each other when forming a ring-shaped gate that opens into the cavity at a position corresponding to the side surface of the center hole, and a surface that forms the cavity in the movable die. And a stamper attached to the fixed die, the gate cutter forming the gate and forming the side surface of the center hole by the outer side surface is provided to the fixed die so as to be movable in the opening and closing directions of the fixed die and the movable die. The movable die is provided with a receiving portion into which the tip end portion of the gate cutter that has advanced is fitted, and the side face of the center hole in the gate cutter is formed. In minutes, it is obtained by forming a tapered portion.

[0008]

In the present invention, during molding, the fixed mold and the movable mold are closed, and the cavity is first filled with resin while the gate cutter of the fixed mold is separated from the movable mold. In this state, a ring-shaped gate is formed between the gate cutter and the movable die, and the cavity is filled with the resin so as to spread radially from the gate. After this filling, before the resin in the cavity is solidified, the gate cutter is advanced, and its tip end is fitted into the receiving part of the movable die. As a result, the resin is cut at the gate, and the central hole of the substrate is formed simultaneously with the molding. That is, the side surface of the center hole is formed by the outer side surface of the gate cutter, but the center hole is also formed by the tapered portion of the gate cutter. Then, since the center hole of the molded substrate is tapered, when the center hole is fitted into the drive head of the recording device or the reproducing device, the side face of the center hole comes into close contact with the side face of the drive head, and the substrate The drive head and the drive head are accurately positioned on the same axis without rattling. This makes it easier to follow up when reading recorded signals, and
Higher signal density is also possible.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the recording disk molding die of the present invention will be described below with reference to FIGS. The recording disk of this embodiment is MD-MO, and the substrate 20 is molded. In the following description, the upper and lower expressions are based on the drawings in FIGS. 1 and 2. In FIG. 2, 21 is a fixed type and 22 is a movable type.
The mold 21 and the movable mold 22 are opened and closed in the vertical direction, and when the molds are closed, a cavity 23 having the shape of the substrate 20 is formed between them.

The fixed mold 21 has a fixed side mounting plate 25 which is mounted on a fixed side platen of a molding machine (not shown).
26 is supported so as to be vertically movable within a predetermined range, and the fixed-side mold plate 26 is constantly urged downward by a spring 27. Also, it is located inside the fixed-side template 26 and is fixed to the fixed-side mounting plate.
A fixed side receiving plate 28 is fixed to the lower surface of 26, and a cavity member 29 is fixed to the lower surface of the fixed side receiving plate 28. A pressing plate 31 is supported above the fixed-side receiving plate 28 and is movable in the fixed-side mounting plate 25 so as to be vertically movable within a predetermined range. The pressing plate 31 is driven in the vertical direction by a hydraulic cylinder 32 provided in the same fixed side mounting plate 25. The pressing plate 31 has a substantially cylindrical sprue bush 33 that also functions as a gate cutter.
Is fixed. The sprue bush 33 has a sprue 34 inside, and vertically penetrates a fixed side receiving plate 28 and an outer bush 35 fixed to the cavity member 29 in a penetrating state. A locate ring 36 is fixed to the upper surface of the fixed side mounting plate 25.

On the other hand, the movable die 22 has a movable side attachment plate 41 attached to the movable side platen of the molding machine. The movable side receiving plate 43 is fixed to the upper surface of the movable side mounting plate 41 via the first spacer block 42, and the second spacer block 44 is interposed on the upper surface of the movable side receiving plate 43. The movable side template 45 is fixed. The core member 46 is fixed in the movable side mold plate 45. A thin disk-shaped stamper 47 (shown in FIG. 1) is detachably attached to the upper surface of the core member 46 forming the cavity 23. The stamper 47 has a reverse shape of the guide groove 9 (shown in FIG. 6) formed on the lower surface. The stamper 47 has a substantially cylindrical inner peripheral stamper presser 48 detachably fixed to the upper central portion of the core member 46 so that the inner peripheral portion is fixed to the upper peripheral portion of the core member 46. The outer peripheral portions are pressed from above by the annular outer peripheral stamper presser 49. The outer peripheral stamper retainer 49 is configured such that a part of the cavity member 29 is fitted and the lower surface of the cavity member 29 forms the cavity 23.

The movable side mounting plate 41 and the movable side receiving plate
A first ejecting plate 51 is fixed between the first ejecting plate 51 and 43 so as to be vertically movable within a predetermined range, and an ejecting pin 52 is fixed to the first ejecting plate 51. A second protruding plate 53 is fixed between the movable side receiving plate 43 and the movable side mold plate 45 so as to be vertically movable within a predetermined range, and the protruding sleeve 54 is fixed to the second protruding plate 53. ing. The protruding sleeve 54 penetrates the movable side mold plate 45 and the core member 46, and has a tip end slidably fitted in the inner peripheral stamper holder 48. Further, an intermediate sleeve 55 fixed to the movable side receiving plate 43 is slidably fitted in the protruding sleeve 54, and the protruding pin 52 is slidably fitted in the intermediate sleeve 55. ing. Further, the first protruding plate
The interlocking pin 56 is fixed to 51, but this interlocking pin 56
Penetrates through the movable side receiving plate 43 and has a second protruding plate 53 at the tip.
Is facing.

Next, the structure near the tip of the sprue bush 33 which also serves as the gate cut pin will be described in detail with reference to FIG. The lower end portion of the sprue bush 33 is fitted in the concave receiving portion 61 formed in the movable die 22 so as to be freely inserted and removed in the mold closed state as the sprue bush 33 moves up and down. This receiving part 61 is an intermediate sleeve.
It is formed by the upper end surface of 55 and the inner side surface of the protruding sleeve 54, and this side surface is a cylindrical surface whose axial direction is the vertical direction. A disc-shaped runner 62 communicating with the sprue 34 is formed between the receiving portion 61 and the lower end surface of the sprue bush 33 in the mold closed state and the state where the sprue bush 33 is raised. Ring-shaped gate leading from the runner 62 to the cavity 23 between the upper end of the side of the sprue and the upper end of the outer side of the sprue bush 33.
63 is what is formed. The width t of this gate 63 is 0.4
It is about mm. Further, the sprue bush 33 forms the side surface of the center hole 64 of the substrate 20 by the outer side surface thereof. The side surface of the sprue bush 33 forming the side surface of the center hole 64 is tapered downward. Tapered part
65 are formed. The tapered portion 65 has a truncated cone shape having a vertical direction. However, the side surface of the same sprue bush 33 is below the tapered portion 65,
A cylindrical surface 66 having a diameter substantially the same as that of the receiving portion 61 and an axial direction being the vertical direction is formed, and the cylindrical surface 66 is fitted to the side surface of the receiving portion 61.

Next, the operation of the above configuration will be described. At the time of molding, first, the fixed mold 21 and the movable mold 22 are closed. In this mold closed state, the fixed mold plate 26 and the movable mold plate 45 abut each other. The molding machine is
The mold can be clamped in two steps. In the mold clamp in the first step, the fixed side mold plate 26 is pushed by the spring 47 and the fixed side mounting plate 25 is pressed.
It is still floating from below. Then, a part of the cavity member 29 of the fixed mold 21 is fitted into the outer peripheral stamper holder 49 of the movable mold 22, and as shown in FIG. 1A, the cavity member 29, the sprue bush 33 in the raised position, The cavity 23 is formed by the outer bush 35, the core member 46, the stamper retainers 48, 49, and the protruding sleeve 54 in the lowered position. At the same time, a runner 62 and a gate 63 are formed between the sprue bush 33 and the intermediate sleeve 55 and the protruding sleeve 54.

Then, the molten resin is injected from the nozzle of the molding machine connected to the sprue bush 33. The molten resin flows into the cavity 23 through the sprue 34 and the runner 62 so as to spread radially from the ring-shaped gate 63, and is filled in the cavity 23 (filling step). After this filling step, while the resin in the cavity 23 is still soft, the hydraulic cylinder 32 is driven to move the pressure as shown in FIG.
As shown in (b), the sprue bush 33 moves downward, and the cylindrical surface 66 of the sprue bush 33 has a receiving portion for the movable die 22.
Fit slightly inside 61. As a result, at the gate 63,
The resin in the runner 62 and the resin in the cavity 23 are cut (gate cutting step), and the sprue bushing is performed.
Due to 33, the central hole 64 of the substrate 20 is formed simultaneously with the molding. The resin is surely cut off by fitting the cylindrical surface 66 of the sprue bush 33 into the side surface of the receiving portion 61, which is formed of a cylindrical surface having substantially the same diameter.

Also, before the resin in the cavity 23 is solidified, the second stage mold clamping is performed in the molding machine. As a result, the fixed-side mounting plate 25 relatively moves down against the spring 27 until it abuts the fixed-side template 26. The cavity member 29 approaches the core member 46 together with the fixed-side mounting plate 25, whereby the resin in the cavity 23 is compressed (compression step). This compression process is performed from the stamper 47 to the substrate.
This is for improving the transferability of the guide groove 9 to the surface of 20. At the end of the gate cutting process and the compression process, the upper end of the tapered portion 65 of the sprue bush 33 is located at the same height as the lower end surface of the outer bush 35.

Then, after the resin in the cavity 23 is sufficiently cooled and solidified, the fixed mold 21 and the movable mold 22 are opened, and the molded substrate 20 is taken out. With the mold opening, the runner
Due to the undercut shape of the 62 part, the resin of the sprue 34 and the runner 62 part first separates from the fixed mold 21 and stops on the movable mold 22 side. The air is blown out on the fixed mold 21 side, so that the substrate 20 also first separates from the fixed mold 21 and stops on the movable mold 22 side. Then, the ejection rod on the molding machine side pushes the first ejection plate 51 upward. As a result, the protrusion pin 52 moves upward, and the resin in the sprue 34 and the runner 62 is separated from the movable die 22. The interlocking pin 56 pushes up the second ejection plate 53 shortly after the movement of the ejection pin 52 starts. Along with this, the protruding sleeve 54 moves upward, and the substrate 20 separates from the movable die 22.

As described above, at the time of molding the entire substrate 20, the tapered central hole 64 can be easily formed at the same time. Moreover, since the sprue bush 33 also serving as a gate cutter is operated to form the central hole 64 while the resin is still soft, the molded substrate 20 is not adversely affected. That is, if post-processing such as cutting the central hole 64 is performed, the substrate 20 may be distorted and its optical characteristics may be impaired, but this is not the case.

FIG. 3 shows a disk body 71 in which films 4, 5, 6, 7, 8 (shown in FIG. 7) are formed on a molded disk-shaped substrate 20. Note that the top and bottom of the substrate 20 in FIGS. 1 and 2 and the top and bottom of the disk body 71 in FIG. 3 are opposite. As shown in detail in FIG. 4, the center hole 64 of the disc body 71 has a cylindrical portion 64a at a part of the upper portion thereof, but has a tapered portion 64b at a lower portion thereof which becomes thinner upward. ing. This tapered portion 64b
Is formed by the tapered portion 65 of the sprue bush 33, and the cylindrical portion 64a is formed by the sprue bush 33.
It is formed by the cylindrical surface 66 of. The central hole
The angle θ formed by the generatrix of the side surface of the tapered portion 64b of 64 with respect to the vertical line is 10 °. This angle θ is not limited to 10 °, but is preferably set to 5 ° or more in order to prevent the drive head 96 from being bitten and not separated.

Further, the drive head 76 of the recording / reproducing apparatus
Has a tapered portion 77 having the same inclination as that of the tapered portion 64b of the central hole 64, and a collar portion 78 is located below the tapered portion 77. However, the diameter of the lower end of the tapered portion 77 is larger than the diameter of the lower end of the center hole 64.

Then, the tapered portion 64b of the center hole 64 of the disk body 71 and the tapered portion 77 of the drive head 76.
Due to this shape, when the center hole 64 is fitted into the taper portion 77 of the drive head 76 from above, the side surface of the taper portion 77 is brought into close contact with the side surface of the taper portion 64b of the center hole 64 and the disk body 71. The drive head 76 and the drive head 76 are accurately positioned coaxially without rattling.

As a result, when reading the guide groove 9 located spirally from the center of the disk body 71,
The follow up becomes easy. That is, it is not necessary to obtain the radial deviation of the disk body 71 due to the rattling between the disk body 71 and the drive head 76, and the servo mechanism for driving the optical pickup 16 in the radial direction is eliminated. Can be simplified. At the same time, the pitch between the guide grooves 9 can be reduced, and therefore, the audio signal recording can be made high in density.

Incidentally, the center hole of the disk body 71 is
If the side surfaces of the drive head 76 and the drive head 76 are tapered so as to be in close contact with each other, the height of the disk body 71 with respect to the drive head 76 may slightly vary, but the optical pickup 16 has an automatic focus adjustment mechanism. There is no problem because it is equipped.

Incidentally, the disk body 71
Instead of forming the cylindrical portion 64a in the central hole 64, the entire central hole 64 of the disk body 71 may be tapered as shown in FIG. This can be achieved by setting the dimensions of the entire cylindrical surface 66 of the sprue bush 33 in the receiving portion 61 in the molding die.

Furthermore, the present invention is not limited to the above-mentioned embodiment, but various modifications can be made. For example, although the recording disk of the above embodiment is MD-MO, the present invention can be applied to other recording disks such as a read-only mini disk and a compact disk. Also,
The structure of the molding die is not limited to that of the above embodiment.

[0026]

According to the present invention, after the resin is filled in the cavity and before the resin is solidified, the gate cutter provided in the fixed die is fitted into the receiving portion of the movable die, so that the resin is kept in the gate. While it is possible to cut and form the center hole of the substrate at the same time as molding, since the tapered portion is formed in the part that forms the side surface of the center hole in the gate cutter, the center hole can be tapered and the center hole can be formed. Is easy to form and does not adversely affect the substrate to be molded. Further, since the central hole of the substrate is tapered, when the central hole is fitted into the drive head of the recording device or the reproducing device, the side face of the central hole is closely attached to the side face of the drive head, and the substrate and the drive head are separated from each other. It can be accurately positioned coaxially without rattling. As a result, the recorded signal can be easily tracked during reading, the servo mechanism for driving the reading optical pickup can be simplified, and the signal recording can be performed at high density.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of the vicinity of a tip portion of a gate cutter showing an embodiment of a recording disk molding die of the present invention.

FIG. 2 is a sectional view of the same as above.

FIG. 3 is a cross-sectional view of a recording disk including a substrate formed by the same as above.

FIG. 4 is an enlarged cross-sectional view of the vicinity of the central hole of the recording disk.

FIG. 5 is a sectional view of the vicinity of a center hole of a recording disk according to another embodiment of the present invention.

FIG. 6 is a perspective view showing a guide groove of an MD-MO which is a recording disk.

FIG. 7 is an enlarged cross-sectional view of the same MD-MO.

FIG. 8 is a sectional view showing an example of a conventional recording disk.

[Explanation of symbols]

 20 Substrate 21 Fixed type 22 Movable type 23 Cavity 33 Sprue bush (gate cutter) 47 Stamper 61 Receiving part 63 Gate 64 Center hole 65 Tapered part

Claims (1)

[Claims] 1. A recording disk molding die for molding a disk-shaped recording disk substrate having a central hole, and a cavity having the shape of the substrate, and an opening at a position corresponding to a side surface of the central hole. A ring-shaped gate that is opened and closed when the mold is closed, and a fixed mold that is opened and closed, and a stamper that is attached to a surface of the movable mold that forms a cavity. And a gate cutter that forms the side surface of the center hole by the outer side surface is provided so as to be movable in the opening and closing directions of the fixed mold and the movable mold, and the tip of the gate cutter that has advanced into the movable mold is fitted. And a tapered portion is formed in a portion of the gate cutter that forms a side surface of the center hole. Disk molding die.