JP2005329670A - Die assembly for molding disc substrate and method for molding disc substrate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a die assembly for molding a disc substrate which can flatten the main surface of a disc substrate, and thereby, make the thickness of a cover layer uniform in the manufacture of an optical disc and prevent air bubbles from being generated by an intermediate layer in the manufacture of a multilayer optical disc, and a method for molding the disc substrate. <P>SOLUTION: A molding die 10 is constituted of a cavity side half and a movable half, and the cavity side half has a cavity side mirror constituted of an inner peripheral mirror 11 and an outer peripheral mirror 18. On the other hand, the movable side die has a movable side mirror 14 and an outer peripheral ring 17 and the cavity side mirror surface mirror to which a stamper 11a is attached, is formed of an inner peripheral side mirror surface 11b and an outer peripheral side mirror surface 18a. In addition, the outer peripheral part of the cavity side mirror surface is bent by the outer peripheral side mirror 18 in a direction where the thickness of the outer peripheral part of the disc substrate to be molded becomes gradually thinner. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a disk substrate molding die apparatus and a disk substrate molding method, and more particularly to a disk substrate for molding a disk substrate having a flat main surface while suppressing swelling generated at the outer periphery during molding of the disk substrate. The present invention relates to a molding die apparatus and a disk substrate molding method.

  Computer storage devices and the like include disk-shaped recording media (hereinafter referred to as optical disks) on which information signals are written and read using light, such as read-only optical disks, magneto-optical disks, and phase-change optical disks. It is popular. In general, a resin-made disk substrate is used as a disk substrate for an optical disk.

  The disk substrate is manufactured by injection molding a heat-melted resin material. Here, after the pellet-shaped resin material is sufficiently removed of moisture by a dryer, it is put into an injection molding machine. The resin material charged into the injection molding machine is injected into a closed space (hereinafter referred to as a cavity) formed in the disk substrate molding portion. A stamper is disposed in the cavity, and a disk substrate on which the uneven pattern of the stamper is transferred is produced by solidifying the resin material.

  A molding die for molding a disk substrate includes a fixed-side mirror that molds one main surface of the substrate, a movable-side mirror that molds the other main surface of the substrate, and an outer ring that molds the outer peripheral portion of the substrate. It is configured. FIG. 8 is a cross-sectional view showing a conventional mold. The mold is composed of a fixed mold and a movable mold. The fixed side mold has a fixed side mirror 101, and the movable side mold has a movable side mirror 104 and an outer peripheral ring 107.

  The fixed side mold is provided in a state of being fixed to the injection molding machine main body. A sprue bush 102 having a molten resin material path is fitted into the fixed mold. The sprue bush 102 is provided with a resin injection port 102a. The resin injection port 102 a is located at the center of the molding cavity 103 and injects a synthetic resin material such as molten polycarbonate resin supplied from the injection unit side into the cavity 103.

  The movable side mold is provided so as to be movable in a direction approaching and separating from the fixed side mold (left and right direction in the drawing). In the movable side mold, the molding surface 104a of the movable side mirror 104 is disposed so as to face the stamper 101a that forms the molding surface of the fixed side mirror 101. The movable mold includes a center punch 105 for punching a center hole in the molded substrate, and a protruding member 106 for removing the molded substrate from the cavity 103 located on the outer peripheral side of the center punch 105. It is arranged.

  The outer peripheral ring 107 is formed in an annular shape and is slidably attached to the outer peripheral side of the movable mirror 104. A cavity 103 is formed between the stamper 101a that is the molding surface of the fixed-side mirror 101, the molding surface 104a of the movable-side mirror 104, and the outer peripheral ring 107 in a state where the fixed-side mold and the movable-side die are in contact with each other. .

  When a disk substrate is produced by an injection molding method using the disk substrate molding die configured as described above, the outer periphery of the produced disk substrate is swollen.

  In Patent Document 1 below, an outer peripheral ring that also serves to hold a stamper as well as molding a disk outer peripheral portion is formed on a concave / convex surface in which a holding surface that holds the stamper is dispersed in a plurality of strips. A disk molding apparatus is described in which the outer peripheral surface is held to disperse the filling pressure of the molten resin, and the occurrence of swelling of the outer peripheral edge due to pushing back of the outer peripheral ring can be minimized.

JP 11-48291 A

  Further, in Patent Document 2 below, a thin wall is formed in which a cavity is formed so that the substrate gradually becomes thinner toward the outside in the region of the periphery of the substrate to be molded, so that no bulging due to injection pressure occurs. A substrate injection molding method and apparatus are described.

JP-A-9-117927

  In these Patent Documents 1 and 2, it is possible to prevent the outer peripheral portion from bulging due to the injection pressure, and to suppress the thickness unevenness of the disk substrate to be molded.

  However, in the conventional mold for forming the disk substrate, the outer peripheral side is thicker than the inner peripheral side of the disk substrate due to the difference in the cooling rate of the resin, and as shown in FIG. The phenomenon that is formed occurs. Thus, when an optical disk is manufactured with a disk substrate having a raised outer periphery, there are the following problems.

  When an intermediate layer in a multilayer optical disk is formed by laminating sheet-like members, the sheet-like member is not uniformly pressed on the laminating surface, and the disc substrate 110 and the intermediate layer as in the optical disc 120 shown in FIG. The bubble 122 is generated between the sheet member 121 for use.

  In addition, when the cover layer is formed by applying an adhesive onto the main surface of the disk substrate by spin coating and bonding a sheet member to the disk substrate, the film thickness of the cover layer on the outer periphery of the disk substrate is partially There was a problem of becoming thick.

  Further, the conventional mold for forming a disk substrate has a problem that it is difficult to appropriately adjust the prevention of the swelling in accordance with the degree of swelling of the outer peripheral portion.

  Accordingly, an object of the present invention is to make it possible to flatten the main surface of a disk substrate to be molded, thereby making the cover layer thickness uniform in the production of an optical disk, and air bubbles caused by an intermediate layer in the production of a multilayer optical disk. An object of the present invention is to provide a disk substrate molding die apparatus and a disk substrate molding method capable of preventing the occurrence. Another object of the present invention is to provide a disk substrate molding die apparatus and a disk substrate molding method that can be easily adjusted in accordance with the swelling of the disk substrate to be molded.

  In order to achieve the above object, an invention according to claim 1 is directed to a disk substrate molding die device having a mirror having a mirror surface for molding a main surface of a disk substrate. And the mirror surface is bent in a direction in which the thickness of the outer peripheral portion of the disk substrate to be formed is gradually reduced by the mirror on the outer peripheral side. Type device.

  According to a sixth aspect of the present invention, in the disk substrate molding method using a mirror having a mirror surface for molding the main surface of the disk substrate, the mirror is divided into an inner peripheral side and an outer peripheral side of the mirror surface. In this disk substrate forming method, the mirror surface is bent in a direction in which the thickness of the outer peripheral portion of the disk substrate to be formed is gradually reduced.

  According to the present invention, since the mirror surface is bent in a direction in which the thickness of the outer peripheral portion of the disk substrate to be formed gradually decreases, the swelling of the outer peripheral portion generated in the disk substrate to be formed is eliminated by the thin portion. The main surface of the disk substrate to be molded can be flattened. In addition, the mirror is divided on the inner and outer peripheral sides of the mirror surface, and the mirror surface is bent by the outer mirror, so the bending angle can be easily changed by simply replacing the outer mirror. can do.

  Therefore, the thickness of the cover layer in the single-layer and multilayer optical disks can be made uniform, and the generation of bubbles due to the intermediate layer in the multilayer optical disk can be prevented. Thereby, there is an effect that a good optical disk can be manufactured. Moreover, adjustment according to the swelling of the disk substrate to be molded can be easily performed by exchanging the mirror on the outer peripheral side.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an example of a schematic sectional configuration of an injection molding machine to which a disk substrate molding die apparatus according to an embodiment of the present invention is applied. The injection unit side of the injection molding machine 1 includes a cylinder 2, a nozzle 3, a hopper 4, and the like, and the molding unit side includes a stationary platen 5, a movable platen 6, a molding die 10, and the like. The molding die 10 is composed of a fixed mold attached to the fixed platen 5 and a movable mold attached to the movable platen 6.

  The structure and operation of each element constituting the injection molding machine 1 such as the cylinder 2, the nozzle 3, the hopper 4, the fixed plate 5, and the movable plate 6 other than the molding die 10 are the same as those of the conventional injection molding machine for disk substrate molding. It is the same. That is, in a state where the movable mold is in contact with the fixed mold, the pellet-shaped resin material from which moisture has been sufficiently removed by the dryer is put into the hopper 4 of the injection molding machine 1. The hopper 4 communicates with the internal space of the cylinder 2, and the resin material charged into the hopper 4 is supplied into the cylinder 2. The resin material supplied into the cylinder 2 is pushed from the hopper 4 side to the nozzle 3 side while being heated and melted by a screw (not shown) and a heater (not shown), and is injected from the injection port of the nozzle 3. In addition, the temperature in the cylinder 2 and the nozzle 3 is controlled to 300 ° C. to 390 ° C., for example.

  The resin material injected from the nozzle 3 is injected into the cavity 13 formed between the fixed mold and the movable mold through the resin injection hole provided in the fixed platen 5 and the fixed mold. Is done. One injection time at this time is, for example, 0.2 seconds to 0.5 seconds. After the injection of the resin material, the molding die 10 is clamped. The mold clamping force of the molding die 10 at this time is, for example, 15 to 40 tons, and the mold temperature is, for example, 60 ° C. to 110 ° C. After the mold clamping, the disk substrate molded by the cavity 13 is manufactured by solidifying the resin material.

  Here, the structure of the mold of the disk substrate molding mold apparatus according to the embodiment will be described in detail. FIG. 2 is a cross-sectional view showing an example of the structure of a disk substrate molding die according to an embodiment. The molding die 10 is composed of a fixed side die and a movable side die.

  The stationary mold is provided in a state of being fixed to the stationary platen 5 of the main body of the injection molding machine 1. A sprue bush 12 having a molten resin material path is fitted into the fixed mold. The sprue bush 12 is provided with a resin injection hole 12a. The resin injection hole 12 a is located at the center of the molding cavity 13 and injects a synthetic resin material such as molten polycarbonate supplied from the injection unit side into the cavity 13.

  The movable side mold is provided in a state of being fixed to the movable platen 6 of the main body of the injection molding machine 1, and in a direction approaching and separating from the fixed side mold (left and right as viewed in the figure). It can be moved. The movable die has a center punch 15 for punching a center hole in the molded substrate, and a protruding member 16 located on the outer peripheral side of the center punch 15 for removing the molded substrate from the cavity 13. It is arranged.

  The fixed mold has a fixed mirror for forming one main surface of the disk substrate. The fixed side mirror is divided into an inner peripheral side mirror 11 for forming the inner peripheral side of one main surface of the disk substrate and an outer peripheral side mirror 18 for forming the outer peripheral side. That is, the mirror surface (fixed side mirror surface) for forming one main surface of the disk substrate is formed with the inner peripheral side mirror surface 11b on the inner peripheral side and the outer peripheral side mirror surface 18a on the outer peripheral side.

  The outer peripheral side mirror 18 is formed in an annular shape, and is attached to the outer peripheral part of the inner peripheral side mirror 11. The outer peripheral side mirror 18 is detachable from the inner peripheral side mirror 11.

  The outer peripheral side mirror surface 18a has an inclined surface such that the thickness of the outer peripheral part of the disk substrate to be molded becomes gradually thinner than the inner peripheral side mirror surface 11b perpendicular to the thickness direction of the disk substrate. Yes. Therefore, the outer peripheral portion of the mirror surface forming one main surface of the disc substrate is bent toward the direction in which the thickness of the outer peripheral portion of the disc substrate to be formed is gradually reduced, that is, toward the inside of the cavity 13.

  For example, when the outer diameter of the disk substrate to be molded is φ120 mm, the diameter D that is the starting point of the bending is preferably in the range of φ119 to φ120.5 mm for flattening the main surface. Here, the center of the diameter D is the same as the center of the outer diameter of the disk substrate to be molded. In addition, the bending angle α is appropriately determined depending on the type of resin material, temperature change, and the like. For example, when a disk substrate for a general optical disk is manufactured, 0.5 ° to 5 °. This range is suitable for the flattening of the main surface.

  A stamper 11a is curvedly attached along the bent fixed mirror surface. The stamper 11a is made of a metal master such as nickel, and has a concavo-convex shape for forming a signal layer on the surface facing the movable mold. This uneven shape is, for example, for pit formation in the case of a read-only optical disc disk substrate, and for land and groove formation in the case of a writable optical disc disk substrate.

  The movable side mold has a movable side mirror 14 for forming the other main surface of the disk substrate and an outer peripheral ring 17 for forming the outer periphery of the disk substrate. The movable side mirror 14 has a molding surface 14a (movable side mirror surface) for molding the other main surface of the disk substrate. The molding surface 14a of the movable side mirror 14 is disposed so as to face the stamper 11a constituting the molding surface on the fixed side mirror 11 side, and molds the other main surface of the disk substrate.

  The outer peripheral ring 17 is formed in an annular shape and is slidably attached to the outer peripheral side of the movable mirror 14. The outer periphery of the disk substrate is formed by the inner peripheral surface of the outer peripheral ring 17.

  The stamper 11a attached to the fixed-side mirror and the molding surface 14a of the movable-side mirror 14 and the outer periphery in a state where the fixed-side mirror composed of the inner-side mirror 11 and the outer-side mirror 18 and the movable-side mirror 14 are in contact with each other. A cavity 13 is formed between the ring 17. Therefore, in this molding die 10, a disk substrate is produced which is molded by the cavity 13 and to which the uneven shape of the stamper 11 a is transferred.

  By having a structure in which the outer peripheral part of the mirror surface forming one main surface of the disk substrate is bent, the swelling of the resin generated in the outer peripheral part of the disk substrate to be molded due to the difference in injection pressure and resin cooling rate, etc. However, it is absorbed by the thin part of the outer periphery of the disk substrate, and the disk substrate 20 having a flat main surface as shown in FIG. 3 can be formed. Moreover, adjustment according to the swelling condition of the outer peripheral part of the disk substrate to be molded can be easily performed only by replacing the outer peripheral mirror 18.

  In the example shown in FIG. 2, all of the outer peripheral side mirror surface 18 a is an inclined surface, but a structure in which an inclined surface is provided by being bent from the middle of the outer peripheral side mirror surface 18 a may be used. Further, high thickness accuracy is required on the signal reading surface side of the optical disc. Therefore, in this embodiment, only the fixed-side mirror surface to which the signal reading surface side stamper 11a is attached is bent, but the movable-side mirror surface, that is, the molding surface 14a is similarly molded disk substrate. The outer peripheral portion may be bent in a direction in which the thickness of the outer peripheral portion gradually decreases, and both main surfaces may be flattened.

  Here, some examples of the optical disk that can be manufactured using the disk substrate molded by the disk substrate molding die apparatus according to the embodiment will be described. FIG. 4 is an enlarged cross-sectional view showing an example of the configuration of a single-layer optical disc using a thin cover layer. Reference numeral 21 denotes an optical disc for single-layer high-density recording having a structure using a thin cover layer. The optical disc 21 is configured by sequentially laminating a reflective film or recording film 23 and a cover layer 24 on one main surface of a substrate 22.

  The substrate 22 is made of a low-absorbency resin such as polycarbonate (PC) or cycloolefin polymer. The laser beam condensed by the lens 25 having a high numerical aperture (NA) is applied to the reflection film or the recording film 23. For example, the lens 25 has a configuration in which two lenses are bonded together, and the NA is 0.85. In the case of a recordable disc, for example, a phase change film is used as the reflective film or the recording film 23.

  The optical disk 21 has a substantially disk shape with a center hole (not shown) opened at the center. As an example, the disk diameter is 120 mm, the center hole diameter is 15 mm, and the disk thickness is 1.2 mm. The thickness of the substrate 22 is 1.1 mm, for example, and the thickness of the cover layer 14 is 0.1 mm, for example.

  A laser beam through the lens 25 is irradiated from the cover layer 24 side to the reflective film or the recording film 23 of the optical disc 21. The distance of the lens 25 from the optical disk 21 is adjusted to focus on the reflective film or recording film 23, and recording or reproduction is performed on the reflective film or recording film 23. During reproduction, the return light reflected by the reflective film or recording film 23 is received by the light receiving element.

  The optical recording layer made of the reflective film or the recording film 23 forms a pit pattern with a fine uneven shape. The pit has a pit length modulated according to the recording data. The pit pattern is formed in the case of a read-only disc.

  In the case of a writable optical disk, the above-described fine uneven shape forms lands and grooves. For example, a portion close to the optical pickup is defined as a groove, and a portion far from the optical pickup is defined as a land. Grooves and lands are alternately formed, and a signal is recorded on one of the land and the groove or both of the optical recording layers. The land and groove are used for tracking, used for rotation control of the spindle motor, and further used for recording address information indicating a position on the disk by the wobbled groove. In a recordable disc, data is recorded at a desired position with reference to this address information.

  In the case of a writable optical disk, the reflective film or recording film 23 has a configuration in which a recording film such as a dielectric film and a phase change film, a dielectric film, and a reflective film are sequentially laminated from the upper layer side. The layer configuration and the number of layers vary depending on the type and design of the recording material.

  Here, an example of a method for manufacturing the read-only optical disc 21 will be described. First, in the substrate molding step, the substrate 22 is molded into a substantially disk shape having a center hole at the center by an injection molding method or the like. At this time, fine irregularities corresponding to recording data, that is, concave portions to be pits are formed on one main surface of the substrate 22 by the stamper attached in the mold. The pit has a pit length modulated according to the recording data, and a pit pattern composed of a pit and a plurality of pits is subjected to predetermined reproduction conditions (laser wavelength 405 nm, objective lens numerical aperture 0.85, etc.). It has a corresponding shape.

  After forming the substrate 22, a reflective film or recording film 23 is formed on the surface of the substrate 22 having pits, and an optical recording layer is formed. As the film material of the reflection film or the recording film 23, for example, aluminum, silver, gold, or an alloy containing these is used. This reflective film or recording film 23 is formed on the surface of the substrate 22 having pits by sputtering, vacuum deposition or the like in consideration of the film material, thickness and the like so as to have a desired reflectance. Here, the desired reflectance is a reflectance that enables at least the return light to be received by a light receiving element outside the optical disk and to detect the presence or absence of pits when the reproduction light is reflected.

  After the formation of the reflective film or recording film 23, a cover layer 24 is formed on the reflective film or recording film 23. The cover layer 24 is a reflective film or a recording film 23 by spin-coating a UV curable adhesive having light transmittance with a spin coater and bonding a light transmissive sheet member such as a polycarbonate (PC) sheet. Formed on. After the UV curable adhesive is coated and the sheet-like members are bonded together, ultraviolet rays are irradiated toward the coated UV curable adhesive to cure the UV curable adhesive. Thereby, the cover layer 24 is formed.

  Although not shown, a lubricant such as a hard coat is coated on the surface of the cover layer 24 as necessary. The lubricant is for protecting the surface of the cover layer 24 and smoothing the surface. The lubricant is applied with a uniform film thickness on the surface of the cover layer 24 by a spin coater.

  The optical disc 21 is manufactured as described above. By using the above-described injection molding machine 1 for forming the substrate 22, the main surface of the substrate 22 can be flattened, thereby eliminating the uneven thickness of the cover layer 24 and uniforming the film thickness to the outer periphery. Can be.

  Although the optical disk 21 has a single-layer structure, the present invention can be applied to the manufacture of an optical disk having a multilayer structure. FIG. 5 is an enlarged cross-sectional view showing an example of the structure of a multi-layered optical disk using a thin cover layer. In FIG. 5, reference numeral 31 is an optical disk for high-density recording having a two-layer structure. The optical disc 31 is configured by sequentially laminating a reflective film 33, an intermediate layer 36, a semi-transmissive reflective film 37 and a cover layer 34 on a substrate 32.

  The substrate 32 is made of a low-absorbency resin such as polycarbonate (PC) or cycloolefin polymer. The laser light collected by the lens 35 having a high numerical aperture (NA) is applied to the reflective film 33 or the semi-transmissive reflective film 37. For example, the lens 35 has a configuration in which two lenses are bonded together, and the NA is 0.85. In the case of a recordable disc, for example, a phase change film is used as the reflective film 33 or the semi-transmissive reflective film 37.

  The optical disc 31 has a substantially disk shape with a center hole (not shown) opened at the center. As an example, the disk diameter is 120 mm, the center hole diameter is 15 mm, and the disk thickness is 1.2 mm. The thickness of the substrate 32 is, for example, 1.1 mm, the thickness of the intermediate layer 36 is, for example, 25 μm, and the thickness of the cover layer 34 is, for example, 75 μm.

  As shown in FIG. 5, the laser light through the lens 35 is irradiated from the cover layer 34 side to the reflective film 33 or the semi-transmissive reflective film 37 of the optical disc 31. The distance from the optical disk 31 of the lens 35 is adjusted to focus on one of the reflective film 33 and the semi-transmissive reflective film 37, and recording or reproduction is performed on either the reflective film 33 or the semi-transmissive reflective film 37. The The semi-transmissive reflective film 37 is semi-transmissive, and the reflective film 33 is irradiated with laser light through the semi-transmissive reflective film 37 and the intermediate layer 36. At the time of reproduction, the return light reflected by one recording layer on which the reflective film 33 and the semi-transmissive reflective film 37 are focused is received by the light receiving element.

  The first optical recording layer (L0 layer) made of the reflective film 33 and the second optical recording layer (L1 layer) made of the semi-transmissive reflective film 37 form a pit pattern with a fine uneven shape. The pit has a pit length modulated according to the recording data. The pit pattern is formed in the case of a read-only disc.

  In the case of a writable optical disk, the above-described fine uneven shape forms lands and grooves. For example, a portion close to the optical pickup is defined as a groove, and a portion far from the optical pickup is defined as a land. Grooves and lands are alternately formed, and a signal is recorded on one of the land and the groove or both of the optical recording layers. The land and groove are used for tracking, used for rotation control of the spindle motor, and further used for recording address information indicating a position on the disk by the wobbled groove. In a recordable disc, data is recorded at a desired position with reference to this address information.

  In the case of a writable optical disk, each of the reflective film 33 and the semi-transmissive reflective film 37 has a configuration in which a recording film such as a dielectric film and a phase change film, a dielectric film, and a reflective film are sequentially laminated from the upper layer side. Have The layer configuration and the number of layers vary depending on the type and design of the recording material.

  Here, an example of a method for manufacturing a read-only optical disc 31 having two optical recording layers will be described. First, in the substrate forming step, the substrate 32 is formed into a substantially disk shape having a center hole at the center by an injection molding method or the like. At this time, fine irregularities corresponding to recording data, that is, concave portions serving as pits are formed on one main surface of the substrate 32 by the stamper attached in the mold. The pit has a pit length modulated according to the recording data, and a pit pattern composed of a pit and a plurality of pits is subjected to predetermined reproduction conditions (laser wavelength 405 nm, objective lens numerical aperture 0.85, etc.). It has a corresponding shape.

  After the formation of the substrate 32, the reflective film 33 is formed on the surface of the substrate 32 having the pits to form the first optical recording layer. As a film material of the reflective film 33, for example, aluminum, silver, gold, or an alloy containing these is used. The reflective film 33 is formed on the surface of the substrate 32 having pits by sputtering, vacuum deposition, or the like in consideration of the film material, thickness, and the like so as to have a desired reflectance. Here, the desired reflectance is a reflectance that enables at least the return light to be received by a light receiving element outside the optical disk and to detect the presence or absence of pits when the reproduction light is reflected.

  After forming the first optical recording layer, an intermediate layer 36 is provided on the first optical recording layer. The intermediate layer 36 is formed by bonding a UV sheet. The UV sheet is adhesive when uncured, and is cured when irradiated with ultraviolet rays. The sheet is excellent in shape transferability and excellent in light transmittance in the visible light region.

  After the formation of the intermediate layer 36, the stamper is pressed against the intermediate layer 36. This stamper is made of, for example, metal, and has fine irregularities corresponding to recording data on the surface in contact with the intermediate layer 36. As a result, a concave portion that becomes a pit of the second optical recording layer is transferred to the surface of the intermediate layer 36. This pit has a pit length modulated according to the recording data, and a pit pattern composed of a pit and a plurality of pits has predetermined reproduction conditions (laser wavelength 405 nm, objective lens numerical aperture 0.85, etc.) It has a shape corresponding to. After pressing the stamper against the intermediate layer 36, the intermediate layer 36 is cured, and the stamper and the intermediate layer 36 are peeled off.

  After the stamper is peeled off, a transflective film 37 is formed on the surface of the intermediate layer 36 having the pits to form a second optical recording layer. As the film material of the transflective film 37, for example, silicon or a compound containing silicon is used. The transflective film 37 is formed on the surface of the intermediate layer 36 having pits by sputtering, vacuum deposition, or the like in consideration of the film material, thickness, and the like so as to have a desired reflectance. Here, the desired reflectance is a reflectance that allows at least the return light to be received by the light receiving element outside the optical disk when the reproduction light is reflected, and to detect the presence or absence of pits. The reflective film 33 of the optical recording layer has a light-transmitting reflectivity that can obtain the above-described desired reflectivity.

  After forming the transflective film 37, the cover layer 34 is formed on the transflective film 37. The cover layer 34 is formed by spin-coating a light-transmitting UV curable adhesive with a spin coater and attaching a light-transmitting sheet member such as a polycarbonate (PC) sheet to the translucent reflective film 37. Formed on top. After the UV curable adhesive is coated and the sheet-like members are bonded together, ultraviolet rays are irradiated toward the coated UV curable adhesive to cure the UV curable adhesive. Thereby, the cover layer 34 is formed.

  Although not shown, a lubricant such as a hard coat is coated on the surface of the cover layer 34 as necessary. The lubricant is for protecting the surface of the cover layer 34 and smoothing the surface. The lubricant is applied on the surface of the cover layer 34 with a uniform film thickness by a spin coater.

  The optical disc 31 is manufactured as described above. By using the above-described injection molding machine 1 for forming the substrate 32, the main surface of the substrate 32 can be flattened, thereby eliminating the uneven thickness of the cover layer 34 and making the film thickness uniform to the outer periphery. Can be. Further, it is possible to prevent the generation of bubbles generated when the intermediate layer 36 is bonded to the substrate 32 and the stamper is pressure-transferred.

  FIG. 6 shows the result of measuring the film thickness of the cover layer of the optical disk when the disk substrate was formed by a conventional disk substrate forming mold apparatus. FIG. 7 shows the result of measuring the film thickness of the cover layer of the optical disk when the disk substrate is molded by the disk substrate molding die apparatus according to the embodiment. The horizontal axis X indicates the distance (mm) from the center of the disk substrate, and the vertical axis Y indicates the average film thickness (μm) of the cover layer.

  In addition, as an optical disk, the diameter was 120 mm, the center hole diameter was 15 mm, and the thickness was 1.2 mm (the thickness of the disk substrate was 1.1 mm). In addition, the shape of the die of the disk substrate molding die device according to one embodiment was such that the above-mentioned division starting diameter D was φ119.6 mm, and the mirror surface bending angle α was 1.2 °.

  As is clear by comparing the measurement result A shown in FIG. 6 and the measurement result C shown in FIG. 7, an optical disc manufactured using a disc substrate molded by the disc substrate molding die device according to one embodiment is: It can be seen that the bumps as in the outer peripheral portion B shown in FIG. 6 were not formed, and the film thickness was made uniform over the entire main surface. Therefore, the thickness error of the cover layer can be within ± 2 μm.

  As described above, according to the disk substrate molding die device according to the embodiment of the present invention, the main surface of the disk substrate to be molded can be flattened. Therefore, it is possible to satisfactorily manufacture a disk substrate of a high-density optical disk such as a Blu-ray Disc (trade name), which requires high thickness accuracy when forming a cover layer or an intermediate layer. Further, adjustment according to the swelling of the disk substrate to be molded is easy.

  The present invention is not limited to the above-described embodiments of the present invention, and various modifications and applications are possible without departing from the spirit of the present invention. For example, in the above-described embodiment, the disk substrate molding die device for molding the disk substrate of the optical disk has been described. However, the present invention is not limited to this, and the disk substrate is a disk substrate of another disk shape such as a disk substrate of a magnetic disk. It can be applied to molding.

It is sectional drawing which shows an example of the structure of the injection molding machine to which the metal mold | die apparatus for disk substrate shaping | molding by one Embodiment of this invention is applied. It is sectional drawing which shows an example of the structure of the disk substrate shaping die by one Embodiment of this invention. It is sectional drawing of an example of the disc board | substrate shape | molded with the die apparatus for disk substrate shaping | molding by one Embodiment. It is sectional drawing which shows an example of a structure of a single layer high density recording disk. It is sectional drawing which shows an example of a structure of a multilayer high-density recording disk. It is a figure which shows an example of the measurement result of the thickness of the conventional cover layer. It is a figure which shows an example of the measurement result of the thickness of the cover layer by one Embodiment. It is a basic diagram which shows an example of the cross-sectional structure of the conventional metal mold | die. It is sectional drawing of an example of the disc board | substrate shape | molded with the conventional metal mold apparatus. It is a figure for demonstrating the bubble produced in the case of formation of an intermediate | middle layer.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Injection molding machine 10 ... Mold for molding 11 ... Inner peripheral side mirror 11a ... Stamper 11b ... Inner peripheral side mirror surface 13 ... Cavity 14 ... Movable side mirror 14a ... Molding surface 18 ... Outer side mirror 18a ... Outer side mirror surface

Claims (6)

In a disk substrate molding die apparatus having a mirror having a mirror surface for molding the main surface of the disk substrate,
The mirror is divided into an inner peripheral side and an outer peripheral side of the mirror surface, and the mirror surface is bent in a direction in which the outer peripheral portion of the disk substrate to be formed is gradually thinned by the mirror on the outer peripheral side. A mold apparatus for molding a disk substrate, characterized in that: In claim 1,
A disk substrate molding die apparatus, wherein a stamper is attached along the mirror surface. In claim 1,
A disk substrate molding die apparatus, wherein an outer diameter of a disk substrate to be molded is φ120 mm, and the bending start point is in a range of φ119 mm to φ120.5 mm centering on the center of the outer diameter. In claim 1,
The disk substrate molding die apparatus, wherein the mirror surface has a bending angle of 0.5 ° to 5 °. In claim 1,
The disk substrate molding die apparatus, wherein the outer peripheral mirror is detachable. In a disk substrate molding method using a mirror having a mirror surface for molding a main surface of a disk substrate,
The mirror is divided into an inner peripheral side and an outer peripheral side of the mirror surface, and the mirror surface is arranged in a direction in which the thickness of the outer peripheral portion of the disk substrate to be formed is gradually reduced by the mirror on the outer peripheral side. A disk substrate molding method characterized by being bent.

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