JP2005122803A - Disk substrate, disk like recording medium, metal mold device of disk substrate, manufacturing method of disk substrate, and manufacturing method of disk like recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To attach a clamping plate to a disk substrate without using an adhesive and to eliminate the warpage of the disk substrate even when the clamping plate having a coefficient of linear expansion different from that of the disk substrate is disposed. <P>SOLUTION: A center hole 2 is formed at the center of the disk substrate, an information area 5 is formed on one principal surface of the disk substrate, a projecting and recessed signal pattern is formed in the information area 5 and the one principal surface 1a is specified to be a loading standard surface. A rib 11 which constitutes a recessed part 13 in the inside of which the clamping plate 12 is housed is integrally formed on the other principal surface 1b and on the periphery of the center hole 2 and the tip side of the rib 11 is deformed inside to attach the clamping plate 12, after the clamping plate 12 is disposed. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an injection-molded disk substrate such as an optical disk, a disk-shaped recording medium, a disk substrate for molding the disk-shaped recording medium, a disk-shaped recording medium, a disk substrate mold apparatus, a disk substrate manufacturing method, and a disk The present invention relates to a method for manufacturing a recording medium.

  Conventionally, there are recording media such as an optical disc, a magneto-optical disc, and a magnetic disc on which control signals such as audio signals, video signals, and servo signals are recorded. In this type of recording medium, a control signal such as an audio signal, a video signal, or a servo signal is recorded on a disc substrate formed by injection molding a light-transmitting resin material with irregularities such as a pit pattern and a land / groove pattern. .

  In the case of an optical disk, in order to record an information signal at a high density, it is necessary to use a short wavelength light beam and an objective lens having a high numerical aperture (NA). Specifically, a compact disc with a standard recording density (hereinafter also simply referred to as a CD) uses a light beam with an objective lens wavelength of 780 nm and an objective lens with a numerical aperture (NA) of 0.45. On the other hand, in a digital versatile disc (hereinafter simply referred to as DVD) recorded at a higher density than a CD, a light beam having a wavelength of 630 nm and an objective lens having a numerical aperture (NA) of 0.6 are used.

  Further, as an objective lens having a high numerical aperture is used, the disk substrate constituting the light beam transmission layer is also made thinner in order to reduce the influence of aberration. For example, a disc substrate having a thickness of 1.2 mm is used for a CD, whereas a disc substrate having a thickness of 0.6 mm is used for a DVD. As described above, the disk substrate compatible with high-density recording is designed to be thin so that the warp of the disk substrate to be molded is minimized, and aberration is not generated.

  Furthermore, there are currently optical disks on which information signals are recorded at a higher density than DVDs. In this optical disc, a light beam having a wavelength of 400 nm is used, and an objective lens having a numerical aperture (NA) of 0.85 is used. When such a high numerical aperture objective lens is used, the thickness of the disk substrate needs to be reduced to about 0.1 mm, but in general injection molding, an ultra-thin condition that satisfies the conditions of warpage and birefringence is required. It is difficult to injection mold a mold disk substrate. Therefore, in an optical disc that realizes this high-density recording, a reflection layer, a dielectric layer, a recording layer, and a dielectric layer are arranged in this order on the signal transfer surface of the disc substrate on which a signal composed of fine irregularities is transferred. These problems are solved by laminating in the order opposite to the order and finally forming a light-transmitting layer of 0.1 mm. This type of optical disc has been proposed with a small diameter of 60 mm or less. Thus, the small-diameter optical disk is mounted on a disk rotation driving device and rotated at a high speed. The optical disc is irradiated with a light beam from the light transmission layer side while being rotated at a high speed, and an optical pickup is placed on a fine recording track provided on a signal recording layer formed on one main surface of the disc substrate. A desired information signal is recorded by illuminating the light beam emitted from.

  In order to accurately irradiate a fine recording track with a light beam while rotating at high speed in this way, the optical disk is reliably integrated with the disk table of the disk rotation driving device and positioned with high accuracy. Need to be installed. In addition, as described above, high-density recording of information signals is possible, and a recording and / or reproducing apparatus that uses an optical disk having a small diameter as a recording medium is also required to be downsized.

  Therefore, such a small-diameter disk substrate is securely integrated with the disk table and positioned and mounted with high accuracy, and the information signal is recorded on the disk substrate or the recorded information signal is reproduced and / or recorded. In order to reduce the size of the playback device, a magnetic plate for magnetic attraction such as a metal plate made of a magnetic material is provided on the optical disc side, and this optical plate is attracted by a magnet provided on the disc table side to thereby obtain the optical disc. There is a disk mounting method that employs a so-called magnet chucking method in which chucking is performed on a disk table.

  As shown in FIG. 6, the optical disk used in the magnet chucking method using the attractive force of the magnet has a disk substrate 101 formed by molding a synthetic resin material such as a transparent polycarbonate resin into a disk shape. ing. On the one main surface 101a side of the disk substrate 101, a signal recording layer 102 on which a desired information signal is recorded is deposited, and finally a light transmission layer 103 of about 0.1 mm is formed. A desired information signal is recorded or reproduced by irradiating the signal recording layer 102 with a light beam from the light transmitting layer 103 side.

  A center hole 104 is formed at the center of the disk substrate 101 to engage with a centering part 107 disposed on the disk rotation drive device side. Further, a clamping plate 106 formed of a magnetic plate is disposed so as to close the center hole 104 at the center portion on the other main surface 101 b side of the disk substrate 101.

  By the way, the clamping plate 106 of the disk substrate 101 is closely fixed to the disk substrate 101 using an adhesive 105 or the like as shown in FIG. If the clamping plate 106 is tightly fixed to the disk substrate 101 in this way, warping or the like on the disk substrate 101 due to a temperature change due to a difference in linear expansion coefficient between the clamping plate 106 and the disk substrate 101 made of a synthetic resin material. Cause deformation.

  As described above, when the disc substrate 101 is warped, when the recording track of the disc substrate 101 is scanned by irradiating the light beam, the focus control and tracking control of the light beam cannot be performed accurately, and the information signal Cannot be recorded or played back.

  In particular, when a magnetic plate is bonded to the disk substrate 101 using an ultraviolet curable adhesive, a predetermined time is required to cure the adhesive 105 and the productivity of the disk substrate 101 is improved. It has become difficult. Further, when a double-sided adhesive tape is used instead of the adhesive 105, it does not have sufficient adhesive strength, and therefore the reliability of the bonding strength of the clamping plate 106 to the disk substrate 101 is lacking.

  In addition, as a manufacturing method of the disk substrate 101, there is a method as described in Patent Document 1 below.

JP 2002-240101 A

  The present invention makes it possible to attach a clamping plate to a disk substrate without using an adhesive, and is provided with a clamping plate such as a metal plate having a linear expansion coefficient different from that of the disk substrate. The present invention also provides a disk substrate, a disk-shaped recording medium, a disk substrate mold apparatus, a disk substrate manufacturing method, and a disk-shaped recording medium manufacturing method that can prevent the disk substrate from warping. For the purpose.

  In the disk substrate according to the present invention, a center hole is formed in the center, an information area is formed on one main surface, an uneven signal pattern is formed on this information area, and this one main surface is connected to the disk rotation driving device. On the other main surface and around the center hole, a rib constituting a concave portion for accommodating the clamping plate is integrally formed on the other main surface.

  Further, the disc-shaped recording medium according to the present invention has a center hole formed in the center, an information area is formed on one main surface, an uneven signal pattern is formed on this information area, and this one main surface is mounted. The disc substrate, which is the reference surface and is the other main surface, around the center hole, with the ribs forming the recesses formed integrally inside, and the tip end side of the ribs are deformed inward to be placed in the recesses And a clamping plate to be provided.

  Further, the mold apparatus according to the present invention is an injection molding of a disk substrate in which a cavity is formed by a fixed mold and a movable mold, and molten resin is filled into a cavity for molding a disk substrate having a center hole through a gate. On the movable mold side, a gate cut pin for forming a center hole of the disc-shaped recording medium is provided at the movable mold center on the movable mold side. The gate cut pin is further outside the gate cut pin with respect to the outer fixed sleeve. An ejector sleeve is provided for moving forward and backward to eject the disc substrate from the movable mold. Before the molten resin is filled into the cavity, the end surface of the fixed sleeve is configured to have the same height as the movable side mirror surface, and the end surfaces of the outer periphery of the ejector sleeve and the gate cut pin are in a position retracted from the movable side mirror surface. . Then, after the resin is filled in the cavity, the gate cut pin advances when the resin is in a semi-molten state, and a rib that forms a recess is formed around the center hole. Eject the disk substrate that has been formed by moving forward.

  Also, in the disk substrate manufacturing method according to the present invention, a cavity for forming a disk substrate having a center hole is formed by the fixed mold and the movable mold, and the center hole of the disk-shaped recording medium is formed at the center of the movable side mirror. A disk substrate mold apparatus is provided with a gate cut pin to be formed and provided with an ejector sleeve on the outside of the gate cut pin, which is further moved forward and backward with respect to the outer fixed sleeve to eject the disk substrate from the movable mold. Use. Before filling the cavity with molten resin, the fixed sleeve end surface is set to the same height as the movable mirror surface, and the outer end surfaces of the ejector sleeve and the gate cut pin are in a position retracted from the movable mirror surface. Yes, after the resin is filled in the cavity, the gate cut pin moves forward when the resin is in a semi-molten state, and a rib that forms a recess is formed around the center hole. Advance and eject the disk substrate.

  Further, in the method for manufacturing a disc-shaped recording medium according to the present invention, a center hole is formed in the center, an information area is formed on one main surface, and an uneven signal pattern is formed on this information area. The surface is the mounting reference surface, and the other main surface, around the center hole, is a disk substrate on which ribs forming a recess are formed integrally, and a clamping plate is placed in the recess. After the clamping plate is disposed in the recess, the tip end side of the rib is deformed inward, and the clamping plate is attached in the recess.

  According to the present invention, a rib is provided around the center hole on the surface opposite to the mounting reference surface of the disk substrate, and a clamping plate having a linear expansion coefficient different from that of the disk substrate is disposed in the recess in the rib. Then, the clamping plate can be attached by deforming the leading end side of the rib inward to provide a locking portion. Since the clamping plate is not attached to the disk substrate by the adhesive but is attached by the locking portion, even if the linear expansion coefficients of the disk substrate and the clamping plate are different, they do not interfere with each other. Warpage of the disk substrate can be prevented.

  Hereinafter, an optical disc to which the present invention is applied, an optical disc substrate used for the optical disc, and a mold apparatus for injection molding the optical disc substrate will be described in detail with reference to the drawings.

  As shown in FIG. 1, an optical disk substrate 1 to which the present invention is applied is formed by injection molding a synthetic resin such as a polycarbonate resin. The optical disc substrate 1 has a center hole 2 formed in the center, a clamping area 3 formed around the center hole 2, and an inner peripheral non-signal recording area on the outer peripheral side of the clamping area 3. A transition area 4 is provided, and an information area 5 in which information signals such as audio signals, video signals and servo signals are recorded in a concavo-convex pattern such as a pit pattern or a land / groove pattern is formed on the outer periphery side of the transition area 4. A rim area 6 serving as an outer peripheral non-signal recording area is formed on the outer peripheral side of the information area 5.

  One main surface 1a of the optical disk substrate 1 serves as a mounting reference surface when mounted on a disk rotation drive device, and a signal recording layer on which an information signal is recorded on the information area 5 of the one main surface 1a. 7a is formed, and a light transmission layer 7b that transmits the light beam emitted from the optical pickup is formed on the signal recording layer 7a.

  In the signal recording layer 7a, a reflective layer for reflecting the light beam emitted from the optical pickup is formed on one main surface 1a of the optical disc substrate 1, and a recording layer for recording an information signal is formed on the reflective layer. ing. The reflection layer constituting the signal recording layer 7a is formed by depositing a metal thin film such as aluminum on the information area 5 on one main surface of the optical disk substrate 1 by vapor deposition or the like. The recording layer constituting the signal recording layer 7a is formed using a phase change material as a recording material when it is a rewritable type, and using an organic dye or the like as a recording material when it is a write-once type. Furthermore, in the case of magneto-optical recording, the recording layer is formed of a magneto-optical material. The light transmissive layer 7 b has a thickness of about 0.1 mm, and is formed, for example, by attaching a light transmissive cover film to one main surface 1 a of the optical disk substrate 1. As long as this light transmission layer 7b covers at least the signal recording layer 7a, the light transmission layer 7b is formed to the inside of the signal recording layer 7a even if the end is flush with the end of the signal recording layer 7a. May be.

  As described above, one main surface 1a of the optical disk substrate 1 is a signal recording surface on which a pit pattern or land / groove pattern of the information area 5 is formed and a light beam is irradiated from the optical pickup. It becomes a mounting reference surface when mounted on the disk table. In addition, one main surface 1a is formed flat except for the pit pattern and land / groove pattern of the information area 5, and the cover film constituting the light transmission layer 7b can be easily attached using a roller or the like. To be able to.

  The center hole 2 formed at the center of the optical disk substrate 1 is engaged with the centering portion 9 of the disk table 8 constituting the disk drive device, and the clamping area 3 is formed around the center hole 2. . As shown in FIGS. 1 and 2, the center hole 2 is a through hole extending from one main surface 1a of the optical disk substrate 1 to the other main surface 1b. As shown in FIG. 2, a straight portion 2 a having a first hole diameter parallel to the rotation axis direction of the optical disc substrate 1 is formed on the peripheral surface of the center hole 2 on the other main surface 1 b side of the optical disc substrate 1. On the one main surface 1a side, a tapered portion 2b is formed which is continuous with the straight portion 2a and gradually expands in diameter from the straight portion 2a. The center hole 2 improves the release characteristics by forming a tapered portion 2b continuous with the straight portion 2a. Here, the hole diameter φ1 of the other main surface 1b on the straight portion 2a side is, for example, 11.03 mm, and the hole diameter φ2 of one main surface 1a on the taper portion 2b side is 11.06 mm. is there. Moreover, the depth D of the straight part 2a is the length which can perform a gate cut reliably, for example, is 0.2 mm or more. Furthermore, the corner part of the center hole 2 which is an edge part of the taper part 2b, and one main surface 1a has the chamfer part 2c comprised by the curved surface (R surface) and the inclined surface (C surface), The mold release characteristics are improved, and burrs or the like protruding toward the one main surface 1a are not generated.

  Furthermore, a step portion 2d is formed at the opening end of the center hole 2 on the one main surface 1a side. The step 2d is formed so that the center side of the center hole 2 is one step lower. When releasing the mold, a burr that protrudes toward the one main surface 1a may occur at the opening end of the center hole 2, but this burr is prevented from protruding from the other main surface 1b. Can do. That is, the height of the step 2 d is set higher than the burr generated at the opening end of the center hole 2. Therefore, it is possible to prevent the clamping plate 12 disposed in the recess 13 from being inclined in the recess 13 due to the burr. In order to improve the mold release characteristics, the step 2d is formed so that the bottom surface is a flat surface and the side surface is an inclined surface inclined outward.

  Around the center hole 2 as described above, a rib 11 is formed on the other main surface 1b side. The rib 11 is formed on the other main surface 1b corresponding to the clamping area 3, for example. The rib 11 is formed in an annular shape so as to surround the center hole 2 integrally with the other main surface 1 b, and a concave portion 13 serving as a storage portion for storing the clamping plate 12 is formed inside the rib 11. It is formed. The rib 11 is formed of a vertical surface portion 11 a that is substantially perpendicular to the other main surface 1 b of the optical disc substrate 1 so that the inner surface side functions as a guide wall of the clamping plate 12 that rattles in the recess 13. Further, the rib 11 is formed with a taper portion 11b on the outer surface side so as to increase in thickness toward the base end so that the release characteristics are improved. Further, the rib 11 is formed so as to increase in thickness toward the proximal end, thereby ensuring strength and having a shape that easily deforms the distal end side inward by caulking using heat, ultrasonic waves, or the like. .

  Here, the clamping plate 12 will be described. The clamping plate 12 is formed of a magnetic plate made of a magnetic material so as to be magnetically attracted to a magnet built in the disk table 8 of the disk rotation driving device. Yes. As shown in FIGS. 1 and 3, the clamping plate 12 is composed of a substantially dish-shaped clamp portion 12a and a flange portion 12b formed around the clamp portion 12a. On the other main surface 1b side, the center hole 2 is disposed in the recess 13 so as to close it. That is, the clamping plate 12 is disposed so that the clamp portion 12a is as far away as possible from the disc table 8 with the opening side as the other main surface 1b side of the optical disc substrate 1. When the optical disk 10 is rotated by the disk table 8, in order to reduce eccentricity when the optical disk 10 is rotated, a taper part 9a that is reduced in diameter toward the front end side is provided around the centering part 9 of the disk table 8. ing. The taper portion 9a is preferably as long as possible in order to reliably engage the peripheral surface of the center hole 2 and minimize eccentricity when the optical disc 10 is rotated. Therefore, the substantially dish-shaped clamping plate 12 is arranged so that the clamp portion 12a is separated from the disc table 8, so that the taper portion 9a of the centering portion 9 of the disc table 8 can be made as long as possible. Further, when the clamping plate 12 is disposed in the recess 13, a space portion can be provided on the inner side, and deformation of the optical disc substrate 1 due to temperature and humidity changes can be prevented.

  An inner diameter R1 of the annular rib 11 constituting the recess 13 in which the clamping plate 12 is accommodated is formed to be larger than an outer diameter R2 of the clamping plate 12, and the inner surface of the rib 11 and the flange of the clamping plate 12 are formed. A gap C1 is provided between the outer peripheral surface of the portion 12b. When the clamping plate 12 is disposed in the recess 13, as shown in FIG. 3, the leading end side of the rib 11 is crushed inside the recess 13 by caulking using heat, ultrasonic waves, or the like. Deformed and becomes a locking portion 14 for locking the flange portion 12b of the clamping plate 12 housed in the recess 13. Here, the height of the locking portion 14 from the other main surface 1b is formed to be higher than the thickness of the flange portion 12b of the clamping plate 12, and between the flange portion 12b and the locking portion 14 is formed. , A gap C2 is provided.

  Therefore, when the clamping plate 12 is disposed in the recess 13, a gap C <b> 1 is formed between the inner surface of the rib 11 and the outer peripheral surface of the flange portion 12 b of the clamping plate 12, and the flange portion 12 b and the locking portion 14. Since the gap C <b> 2 is formed between the two, the recess 13 is loosely fitted and held. As a result, even if the optical disk substrate 1 and the clamping plate 12 having significantly different thermal expansion coefficients are repeatedly expanded or contracted in accordance with changes in the environmental temperature, the difference in expansion or contraction from each other resulting from the difference in thermal expansion coefficient. Are absorbed by the gap C1 and the gap C2 and are prevented from affecting each other, so that no distortion or the like occurs in the optical disc substrate 1, and warpage of the optical disc substrate 1 can be prevented.

  The ribs 11 forming the recesses 13 for accommodating the clamping plate 12 do not necessarily have to be continuous in an annular shape, and may be configured by arranging a plurality of ribs in an annular shape.

  The optical disk 10 in which the clamping plate 12 is attached to the optical disk substrate 1 as described above is mounted on a disk table 8 of a disk rotation driving device as shown in FIG. The disc table 8 is provided with a centering portion 9 that is engaged with the center hole 2 of the optical disc 10 at the center, and a disc support portion 8 a that supports the optical disc 10 in the clamping area 3 is provided around the centering portion 9. In addition, a magnet for magnetically attracting the clamping plate 12 is built in. The optical disk 10 is in a state where it can rotate integrally with the disk table 8 when the centering portion 9 is engaged with the center hole 2 and the clamping area 3 is supported by the disk support portion 8a. When the disk table 8 is rotated, the optical disk 10 rotates integrally with the disk table 8, and the information area 5 is irradiated with a light beam by an optical pickup, thereby reading out recorded information signals and information. A signal will be recorded.

  In the optical disc 1 as described above, the signal recording layer 7a and the light transmission layer 7b can be easily formed by forming one main surface 1a as a signal recording surface of the optical disc substrate 1 flat. In addition, the optical disk 10 is formed with a synthetic resin optical disk substrate 1 by forming a locking portion 14 by deforming the rib 11 formed on the other main surface 1b of the optical disk substrate 1 made of synthetic resin inward. Since the clamping plate 12 locked by a magnetic plate made of a material having a different expansion coefficient can be loosely fitted and held, an optical disk substrate produced by using an adhesive 105 such as an ultraviolet curable adhesive as in the prior art. Thus, it is possible to eliminate problems such as the occurrence of the warp 1 and to accurately record and reproduce information signals. Furthermore, since the clamping plate 12 is formed and held by the caulking of the rib 11 or the like, the clamping plate 12 can be easily attached to the optical disc substrate 1 and the productivity can be improved. Furthermore, since the clamping plate 12 is attached to the optical disc substrate 1 without using the adhesive 105, it is possible to prevent peeling from the optical disc substrate 1 due to insufficient adhesive strength of the adhesive 105 or deterioration of the adhesive. Furthermore, the optical disk 10 has no burrs at the edge of at least one main surface 1a side of the center hole 2, or even if burrs are generated, the burrs can be kept small. This can be performed with high accuracy, and the amount of eccentricity during rotation can be suppressed. Therefore, high-density recording of information signals can be stably performed on the optical disc 10.

  As shown in FIGS. 4 and 5, the mold apparatus 20 for injection molding the optical disk substrate 1 as described above includes a fixed mold 21 and a movable mold 22, and the fixed mold 21 and the movable mold 22 are A cavity 30 for forming the optical disk substrate 1 in the mold clamping state is configured. The fixed mold 21 molds one main surface 1a to be a signal recording surface of the optical disc substrate 1, and the movable mold 22 molds the other main surface 1b on which the rib 11 of the optical disc substrate 1 is formed.

  The fixed mold 21 has a fixed mirror 23, and the mirror surface of the fixed mirror 23 has irregularities such as pit patterns and land / groove patterns formed in the information area 5 on one main surface 1 a of the optical disk substrate 1. A stamper 24 for transferring the pattern is attached. Specifically, when the stamper 24 is positioned and fixed on the outer peripheral side by the stamper holder 25, the inner peripheral side is positioned and fixed by the step portion 24a formed on the fixed mirror 23, and the stamper 24 is positioned and fixed on the fixed mirror 23, It is flush with the mirror surface of the fixed mirror 23 to which the stamper 24 is not attached, so that one main surface 1a constituting the signal recording surface of the optical disk substrate 1 can be formed flat.

  A sprue bush 26 for forming the center hole 2 of the optical disk substrate 1 is provided in the central portion of the fixed mirror 23. A sprue portion 27 for injecting molten resin is formed in the central portion of the sprue bush 26. ing. Specifically, the sprue bush 26 is formed with a central convex portion 28 for forming the center hole 2 of the optical disc substrate 1, and the above-described sprue portion 27 is formed at the central portion of the central convex portion 28. The peripheral surface of the central convex portion 28 is a portion that forms the peripheral surface of the center hole 2, and a straight forming portion 28a is formed to form the straight portion 2a on the distal end side, and a tapered portion 2b is formed on the proximal end side. A taper forming portion 28b is formed. Further, the base end of the peripheral surface of the central convex portion 28 is chamfered to form a chamfered portion 2c formed at a corner portion between the center hole 2 which is an end portion of the tapered portion 2b and the one main surface 1a. A portion 28c is formed.

  A fixed ejector 29 for pushing out the optical disk substrate 1 from the stamper 24, the mirror surface of the fixed mirror 23, and the like is provided on the outer peripheral side of the sprue bush 26 as described above. When ejecting the optical disk substrate 1, the fixed ejector 29 advances into the cavity 30 by, for example, about 0.2 mm, and peels the optical disk substrate 1, which is a molded product, from the stamper 24 and the like.

  The fixed mold 21 configured as described above is for molding one main surface 1a of the optical disk substrate 1. The stamper 24 is disposed on the fixed mirror 23, and a pit pattern, land / An uneven pattern such as a groove pattern is formed. Further, the central convex portion 28 of the sprue bush 26 forms a straight portion 2a, a tapered portion 2b, and a chamfered portion 2c in which the center hole 2 is continuous by a straight forming portion 28a, a tapered forming portion 28b, and a chamfered forming portion 28c. The fixed mold 21 forms one main surface 1a which is a signal recording surface of the optical disc substrate 1 and serves as a mounting reference surface, and a straight forming portion 28a and a taper forming portion 28b are formed on the central convex portion 28 of the sprue bush 26. By providing the chamfer forming portion 28c, burrs protruding from one main surface 1a are prevented from being generated at the time of mold release or the like.

  On the other hand, the movable mold 22 has a movable mirror 31. The mirror surface 31 a of the movable mirror 31 forms the other main surface 1 b of the optical disk substrate 1. The movable mirror 31 is provided with a gate cut pin 32 for forming the center hole 2 of the optical disk substrate 1 at the center. The movable mirror 31 moves forward and backward with respect to the outer fixed sleeve 34 outside the gate cut pin 32. An ejector sleeve 33 for ejecting the optical disc substrate 1 from the movable mold is provided.

  The gate cut pin 32 is provided at a position facing the sprue bushing 26 on the fixed mold 21 side, and a central concave part 35 into which the central convex part 28 of the sprue bushing 26 is fitted is provided on the tip surface. Yes. The gate cut pin 32 is formed with a protrusion 36 for forming the step 2d of the center hole 2 of the optical disc substrate 1 on the other main surface 1b side, following the central recess 35. The inner surface of the projecting portion 36 is a vertical surface 36a that fits at least on the front end side of the straight forming portion 28a of the central convex portion 28 formed on the sprue bush 26. The front end surface of the projecting portion 36 is a stepped surface. The bottom surface forming portion 36b is formed of a flat surface for forming the bottom surface of the portion 2d flat, and the outer surface is an inclined surface for forming the side surface of the step portion 2d into an inclined surface inclined outward. It becomes the inclined surface formation part 36c comprised by these. Further, a flat surface forming portion 36 d that forms a flat region from the center hole 2 to the rib 11 of the other main surface 1 b of the optical disk substrate 1 is provided on the outer side of the protrusion 36 on the front end surface of the gate cut pin 32. ing.

  The gate cut pin 32 advances about 0.4 mm in the direction of the sprue bushing 26, for example, and the central concave portion 35 is fitted to at least the front end side of the straight forming portion 28a of the central convex portion 28 of the sprue bushing 26. One center hole 2 is formed. The center hole 2 formed here includes a continuous straight portion 2a, a tapered portion 2b, and a chamfered portion 2c by a continuous straight forming portion 28a, a tapered forming portion 28b, and a chamfered forming portion 28c of the central convex portion 28 of the sprue bush 26. Is formed. Further, on the other main surface 1b side of the optical disc substrate 1 and around the center hole 2, the bottom surface is flat by the bottom surface forming portion 36b and the inclined surface forming portion 36c formed in the protruding portion 36 of the gate cut pin 32. Thus, the step 2d having the inclined side surface is formed. Further, on the other main surface 1b side of the optical disc substrate 1, a flat region from the step 2d of the center hole 2 of the optical disc substrate 1 to the rib 11 is formed by the plane forming portion 36d. Further, the outer peripheral surface on the front end side of the gate cut pin 32 forms a vertical surface portion 11 a inside the rib 11 of the optical disc substrate 1 when it advances into the cavity 30 to form the center hole 2.

  A protrusion pin 37 for protruding the resin at a position corresponding to the center hole 2 from the central recess 35 is provided at the center of the central recess 35 of the gate cut pin 32.

  An ejector sleeve 33 for ejecting the optical disc substrate 1 from the movable mold 22 at the time of mold release is provided on the outer peripheral side of the gate cut pin 32 configured as described above. The tip end surface 33a of the ejector sleeve 33 is located at the same height as the plane forming portion 36d when the gate cut pin 32 is retracted from the cavity 30. The tip end surface 33 a of the ejector sleeve 33 forms at least a part of the flat top surface of the rib 11 of the optical disc substrate 1. Although the ejector trace remains at the position where the ejector sleeve 33 of the optical disk substrate 1 is in contact, the leading end side of the rib 11 is deformed inside the optical disk substrate 1 by caulking or the like, so that the appearance is deteriorated by the ejector trace. Can also be prevented.

  The fixed sleeve 34 provided on the outer peripheral side of the ejector sleeve 33 is formed with a taper forming portion 34 a for forming a tapered portion 11 b outside the rib 11 of the optical disc substrate 1 on the inner side of the front end surface thereof. Further, on the outside of the taper forming portion 34a, a flat surface forming portion 34b is formed which is flush with the mirror surface of the movable mirror 31 and forms a part on the inner peripheral side of the other main surface 1b of the optical disc substrate 1. In other words, the taper forming portion 34a has the outer end positioned at the same height as the mirror surface 31a of the movable mirror 31 and the inner end positioned backward from the cavity 30 and the tip end surface 33a of the ejector sleeve 33 and the gate cut. It is formed so as to be positioned at the same height as the flat surface forming portion 36d at the tip of the pin 32. When the rib 11 has a vertical surface without forming the taper 11b, the flat surface 34b may be provided up to the inner end without providing the taper 34a.

  The process until the optical disk substrate 1 is formed using the mold apparatus 20 as described above will be described. In the state where the movable mold 22 is moved in the direction of approaching the fixed mold 21, the sprue bushing is clamped. Before the molten resin is injected and filled into the cavity 30 from the sprue portion 26 of the 26, the fixed ejector 29 on the fixed mold 21 side retreats from the cavity 30, and the tip surface becomes flush with the stamper 24, so that the optical disk substrate 1 One main surface 1a is in a state of being formed flat. Further, the gate cut pin 32 is also retracted from the cavity 30, and the flat surface forming portion 36d on the outer peripheral side of the distal end surface of the gate cut pin 32 and the distal end surface 33a of the ejector sleeve 33 are continuously flush with each other. The inner peripheral side end of the taper forming portion 34 a of the fixed sleeve 34 and the flat surface forming portion 36 d of the gate cut pin 32 are located at the same height via the tip end surface 33 a of the ejector sleeve 33, and the flat top of the rib 11. The surface can be formed. Further, the flat surface forming portion 34b of the fixed sleeve 34 is flush with the mirror surface 31a of the movable mirror 31, and is in a state where the other main surface 1b can be formed.

  When the molten resin is injected and filled into the cavity 30 from the sprue portion 27, and the injected and filled resin is in a semi-molten state, the gate cut pin 32 moves forward to the position indicated by the dotted line in FIG. The central concave portion 35 at the tip portion is fitted with the straight forming portion 28a of the central convex portion 28 of the sprue bush 26, and the center hole 2 of the optical disc substrate 1 is formed. At this time, in the center hole 2 of the optical disk substrate 1, the continuous straight portion 2a, the tapered portion 2b, the chamfered portion 28c, the continuous straight forming portion 28a, the tapered forming portion 28b, and the chamfered forming portion 28c of the sprue bush 26 are provided. A chamfer 2c is formed. Further, around the center hole 2 of the optical disk substrate 1, the bottom surface is formed flat and the side surface is inclined by the bottom surface forming portion 36 b and the inclined surface forming portion 36 c formed on the protruding portion 36 of the gate cut pin 32. A step 2d is formed. Further, on the other main surface 1b side of the optical disc substrate 1, a flat region from the center hole 2 to the rib 11 of the optical disc substrate 1 is formed by the plane forming portion 36d. Further, a vertical surface portion 11 a inside the rib 11 of the optical disc substrate 1 is formed around the center hole 2 by the outer peripheral surface on the tip end side of the gate cut pin 32. The top surface of the rib 11 is formed by the tip end surface 33 a of the ejector sleeve 33, and the taper portion 11 b of the rib 11 is formed by the taper forming portion 34 a of the fixed sleeve 34. Further, a flat region on the outer peripheral side from the rib 11 is formed by the flat surface forming portion 34 b of the fixed sleeve 34 and the mirror surface 31 a of the movable mirror 31.

  When the resin injected and filled in the cavity 30 is cooled and solidified, the movable mold 22 is then moved away from the fixed mold 21 and opened.

  Then, the ejector sleeve 33 advances into the cavity 30 and peels off the other main surface 1b of the optical disk substrate 1 which is a molded product from the mirror surface 31a of the movable mirror 31 and the tip surface of the gate cut pin 32, and a fixed ejector. 29 also advances into the cavity 30 and peels off one main surface 1a of the optical disk substrate 1 which is a molded product from the stamper 24 and the like. Furthermore, the protruding pin 37 provided at the center of the gate cut pin 32 peels the resin located in the center hole 2 from the central recess 35.

  In the mold apparatus 20 as described above, one main surface 1a which is a signal recording surface of the optical disk substrate 1 and serves as a mounting reference surface is formed by the fixed mold 21, and the inner wall of the center hole 2 is the center of the sprue bush 26. Since it is formed by the straight forming part 28a, the taper forming part 28b, and the chamfering forming part 28c of the convex part 28, a burr protruding from one main surface 1a does not occur at the time of mold release. Therefore, the optical disk 10 using the optical disk substrate 1 can be mounted with high accuracy on the disk table 8 of the disk drive device. Further, in the mold apparatus 20 as described above, the gate cut pin 32 moves forward to the position indicated by the dotted line in FIG. 5 in the cavity 30, and the central concave portion 35 at the tip portion forms a straight line of the central convex portion 28 of the sprue bush 26. By fitting with the portion 28a, the rib 11 is formed on the other main surface 1b of the optical disc substrate 1 by the outer peripheral surface of the gate cut pin 32, the tip surface 33a of the ejector sleeve 33, and the taper forming portion 34a of the fixing sleeve 34. Can be formed. On the movable mold 22 side, burrs are likely to occur between the vertical surface 36a of the protruding portion 36 provided on the gate cut pin 32 and the straight forming portion 28a of the central convex portion 28 of the sprue bush 26, but at this position. Since the step portion 2d is formed by the bottom surface forming portion 36b and the inclined surface forming portion 36c of the protruding portion 36 of the gate cut pin 32, even if a burr is generated at this position, it is constituted by the rib 11. This burr can be prevented from protruding into the recess 13.

  In the optical disk substrate 1 formed as described above, the clamping plate 12 is disposed in the recess 13 formed by the rib 11 as described above, and thereafter, the tip end side of the rib 11 is deformed inward. It attaches by the latching | locking part 14 formed by this. The optical disk 10 manufactured as described above is made of synthetic resin by forming the engaging portion 14 by deforming the rib 11 formed on the other main surface 1b of the optical disk substrate 1 made of synthetic resin inward. Since the clamping plate 12 locked by a magnetic plate that is a material having a coefficient of thermal expansion different from that of the optical disk substrate 1 can be loosely fitted and held, an adhesive 105 such as an ultraviolet curable adhesive is used as in the prior art. Thus, problems such as the occurrence of warping of the optical disk substrate 1 can be solved, and accurate information signal recording and reproduction can be performed. Furthermore, since the clamping plate 12 is formed and held by the caulking of the rib 11 or the like, the clamping plate 12 can be easily attached to the optical disc substrate 1 and the productivity can be improved. Furthermore, since the clamping plate 12 is attached to the optical disc substrate 1 without using the adhesive 105, it is possible to prevent peeling from the optical disc substrate 1 due to insufficient adhesive strength of the adhesive 105 or deterioration of the adhesive.

  The optical disk, the optical disk substrate, the manufacturing method of the optical disk substrate, and the manufacturing method of the optical disk to which the present invention is applied have been described as examples. However, the present invention is not limited to a magnetic disk as long as it is a synthetic resin substrate molded by injection molding. It can also be applied to disk substrates and the like.

It is sectional drawing of an optical disk board | substrate. It is an expanded sectional view around the center hole of the optical disk substrate. It is sectional drawing which shows the state with which the optical disk with which the clamping plate was attached to the said optical disk board | substrate was mounted in the disk drive device. It is sectional drawing of the metal mold | die apparatus which shape | molds an optical disk board | substrate. It is an expanded sectional view of the above-mentioned metallic mold device. It is sectional drawing which shows the state with which the optical disk used as the premise of this invention was mounted in the disk drive device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Optical disk board | substrate, 1a One main surface, 1b The other main surface, 2 Center hole, 2a Straight part, 2b Tapered part, 2c Chamfered part, 2d Step part, 11 Rib, 11a Vertical surface part, 11b Tapered part, 12 Clamping Plate, 13 Concave part, 14 Locking part, 20 Mold device, 21 Fixed mold, 22 Movable mold, 23 Fixed mirror, 24 Stamper, 25 Stamper holder, 26 Sprue bush, 27 Sprue part, 28 Central convex part, 28a Straight forming portion, 28b Taper forming portion, 29 Fixed ejector, 30 cavity, 31 Movable mirror, 31a Mirror surface, 32 Gate cut pin, 33 Ejector sleeve, 34 Fixed sleeve, 34a Taper forming portion, 34b Bottom forming portion, 35 Central recess 36 Projection, 36a Vertical surface, 36b Bottom surface Forming part, 36c Inclined surface forming part, 36d Plane forming part, 37 Extrusion pin

Claims (16)

A center hole is formed in the center, an information area is formed on one main surface, an uneven signal pattern is formed on this information area, this one main surface is used as a reference surface for mounting on the disk rotation drive device,
A disc substrate, on the other main surface, around the center hole, integrally formed with ribs forming a recess for accommodating a clamping plate inside.   2. The disk substrate according to claim 1, wherein a stepped portion on the other main surface side of the substrate portion and having a lower center portion on the substrate portion is formed at an opening end of the center hole.   The disk substrate according to claim 1, wherein an inner diameter of the rib is larger than an outer diameter of the clamping plate.   The disk substrate according to claim 1, wherein the rib is deformed inward at a front end side and the clamping plate is accommodated in the recess.   5. The disk substrate according to claim 4, wherein a height of the rib whose tip side is deformed inward is larger than a thickness of the clamping plate. A center hole is formed in the center, an information area is formed on one main surface, an uneven signal pattern is formed on this information area, this one main surface is used as a mounting reference surface, and the other main surface is Around the center hole, a disk substrate in which a rib constituting a recess is integrally formed on the inside, and
A disc-shaped recording medium comprising: a clamping plate which is deformed inward on the tip side of the rib and disposed in the recess.   7. A signal recording layer is formed on the information area formed on one main surface of the disk substrate, and a light transmission layer through which a light beam is transmitted is formed on the signal recording layer. The disc-shaped recording medium described.   7. The disc-shaped recording medium according to claim 6, wherein a stepped portion is formed on the other main surface side of the substrate portion and at the opening end of the center hole.   The disc-shaped recording medium according to claim 6, wherein an inner diameter of the rib is larger than an outer diameter of the clamping plate.   The disc-shaped recording medium according to claim 6, wherein a height of the rib whose inner end is deformed inward is larger than a thickness of the clamping plate. In a disk substrate injection mold in which a cavity is formed by a fixed mold and a movable mold, and molten resin is filled into the cavity for molding a disk substrate having a center hole through a gate,
On the movable mold side, a gate cut pin for forming a center hole of the disc-shaped recording medium is provided at the center of the movable mirror, and the gate cut pin advances and retreats with respect to the outer fixed sleeve. And an ejector sleeve for ejecting the disk substrate from the movable mold.
Before filling the cavity with the molten resin, the end surface of the fixed sleeve is configured at the same height as the movable side mirror surface, and the outer end surfaces of the ejector sleeve and the gate cut pin recede from the movable side mirror surface. In the position
After the resin is filled in the cavity, the gate cut pin moves forward when the resin is in a semi-molten state, and a rib that forms a recess is formed around the center hole. A disk substrate mold apparatus for ejecting a disk substrate formed by advancing a sleeve.   12. The disk substrate mold apparatus according to claim 11, wherein a signal transfer stamper is disposed on the fixed mold side.   The fixed sleeve distal end surface is formed with a tapered portion so that the outer peripheral side is a flat surface having the same height as the movable mirror surface, and the inner peripheral side is equal to the height of the outer peripheral end surface of the gate cut pin. Item 12. A mold apparatus for a disk substrate according to Item 11.   One of the gate cut pin and the spool bush facing the gate cut pin is convex and the other is concave, and the gate cut pin advances and retreats to form a concave portion on the inner side around the center hole of the disk substrate. 12. The disk substrate mold apparatus according to claim 11, wherein a rib to be formed is formed. A cavity for molding a disk substrate having a center hole is formed by the fixed mold and the movable mold, and a gate cut pin for forming the center hole of the disk-shaped recording medium is provided at the center of the movable mirror. Using a disk substrate mold apparatus provided with an ejector sleeve that moves forward and backward with respect to the outer fixed sleeve and ejects the disk substrate from the movable mold, outside the pin,
Before filling the cavity with molten resin, the end surface of the fixed sleeve is set to the same height as the movable mirror surface, and the outer peripheral surface of the ejector sleeve and the gate cut pin recedes from the movable mirror surface. In the position
After filling the cavity with resin, when the resin is in a semi-molten state, the gate cut pin moves forward to form a rib that forms a recess inside the center hole,
A method of manufacturing a disk substrate, wherein the ejector sleeve advances to eject the disk substrate when the disk is released. A center hole is formed in the center, an information area is formed on one main surface, an uneven signal pattern is formed on this information area, this one main surface is used as a mounting reference surface, and the other main surface is Around the center hole, a disk substrate is integrally formed with a rib that forms a recess on the inside;
Place the clamping plate in the recess,
A method of manufacturing a disc-shaped recording medium in which after the clamping plate is disposed in the recess, the tip end side of the rib is deformed inward, and the clamping plate is attached in the recess.

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