JP2006031753A - Disk substrate, optical recording medium, and mold apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent the formation of a projection at the outer circumferential part of an optical recording medium. <P>SOLUTION: A mold apparatus is provided with a pair of molds disposed facing each other. A stamper for forming an information reading surface of a disk substrate is mounted on one of the molds. A slope gradually swelling toward the radial direction is provided on the side of the mold on which the stamper is attached. Accordingly, the disk substrate 2 in which the outer circumferential part is tilted so that the thickness is gradually reduced toward the radial direction can be molded. Thus, when an ultraviolet ray curing resin is applied on the disk substrate 2 by a spin coating method, the swelling of the ultraviolet ray curing resin at the outer circumferential part can be prevented. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a disk substrate, an optical recording medium, and a mold apparatus that can realize an information reading surface with excellent uniformity.

  2. Description of the Related Art Conventionally, optical recording media and magnetic recording media are widely known as disk-shaped recording media on which audio, video, various other information, servo signals, and the like are recorded. Specifically, as these recording media, phase change type disks that record information signals using the principle that reflectivity changes depending on the crystal state, and signals are read using the magneto-optical effect of the recording layer. There are magneto-optical disks, magnetic disks that magnetically write and read signals, and the like. More specifically, these recording media include CD (Compact Disc), CD-ROM (Random Access Memory), DVD (Digital Versatile Disc), Blu-ray Disc (registered trademark), MD (Mini Disc), and the like. There is.

  A disk substrate used for an optical recording medium is provided with fine irregularities such as pits and groups (guide grooves) corresponding to information signals, tracking servo signals, and the like. Synthetic resins such as polycarbonate (PC) are widely used as the disk substrate material. As a method of forming a disk substrate, a method of injection molding using a mold apparatus is widely used.

  Incidentally, in the optical recording medium, in order to increase the recording density, the wavelength of the laser light is mainly shortened and the NA of the condenser lens (objective lens) is increased (the lens magnification is improved). For example, the most popular CD uses a laser beam with a wavelength of 780 nm and a condensing lens with a NA of 0.45, whereas a DVD has a laser beam with a wavelength of 630 nm and a NA of 0.6. A condensing lens is used.

  In addition, in order to reduce the influence of aberration associated with the increase in NA of the condensing lens, the disk substrate serving as a laser light transmission layer is gradually made thinner. 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.

  Furthermore, in recent years, in order to further increase the recording density, a laser beam having a wavelength of 405 nm is condensed by an NA 0.85 condenser lens and applied to an optical recording medium to record information signals and It has been proposed to perform reproduction. When this high NA condensing lens is used, it is necessary to reduce the thickness of the disk substrate to about 0.1 mm. However, in general injection molding, the allowable range of warpage and birefringence is limited. It is difficult to mold an ultra-thin disk substrate that meets the requirements. Therefore, in order to solve this problem, on the disk substrate on which fine irregularities are transferred, for example, each layer in the order of the reflective layer, the dielectric layer, the recording layer, and the dielectric layer, that is, the order opposite to the conventional one. An optical recording medium is proposed in which a light transmission layer having a thickness of 0.1 mm is formed thereon after laminating the films.

  A conventional method for manufacturing an optical recording medium will be described below. First, the configuration of a mold apparatus used in a conventional method for manufacturing an optical recording medium will be described. FIG. 12 is a cross-sectional view schematically showing a configuration of a conventional mold apparatus 200. The mold apparatus 200 includes a fixed-side mold 201, a movable-side mold 202 disposed so as to face the fixed-side mold 201, and an outer peripheral ring 203 installed on the movable-side mold 202. A stamper 204 is mounted on the mold surface 201a of the stationary mold 201, and the mounted stamper 204 is sucked and held by a suction groove 205 provided on the mold surface 201a.

  The outer peripheral ring 203 is pressed against the fixed mold 201 with air at a predetermined pressure. A clearance 206 of 5 to 30 μm is secured between the outer peripheral ring 203 and the stamper 204 so that the stamper 204 does not become an obstacle when it expands and contracts due to heat.

  Next, a conventional method for manufacturing an optical recording medium will be described. First, in the above-described conventional mold apparatus 200, the fixed mold 201 and the movable mold 202 are abutted to form a cavity. Next, resin is injected into the cavity through a sprue bush (not shown) installed at the center of the mold apparatus 200, and the resin flows toward the outer peripheral side to fill the cavity with the resin. . Then, when the cavity is filled with the resin, the internal pressure in the mold apparatus 200 is rapidly increased, and as a result, the unevenness formed in advance on the surface of the stamper 204 is transferred to the resin. At this time, a force is applied in a direction in which the movable mold 202 is pushed back by the internal pressure. However, since the outer ring 203 is always pressed against the fixed mold 201 by the air, the fluctuation of the clearance 206 is prevented, and the variability in the disk substrate is prevented. Is prevented from occurring.

  Thereafter, the resin in the cavity is cooled to form a disk substrate, and then the center portion of the disk substrate is punched to form a center hole. Then, after the moving side mold 202 is separated from the fixed side mold 201, the disk substrate is released from the moving side mold 202.

  Thereafter, the information signal portion and the light transmission layer are sequentially laminated on the disk substrate molded as described above to form an optical recording medium. As a method for forming this light transmission layer, there is a method in which an ultraviolet curable resin is applied on a disk substrate by spin coating and then cured, or a separately formed transparent sheet is coated with an adhesive made of an ultraviolet curable resin. A method of bonding and integrating on a substrate has been proposed (for example, see Patent Document 1).

JP 2002-170279 A

  However, in the optical recording medium described above, since the distance between the objective lens for condensing recording or reproducing laser light and the optical recording medium is much closer than before, a disk substrate using a conventional mold apparatus is used. When the (protective plate) is molded, various problems occur. Hereinafter, this problem will be described.

  FIG. 13 is a cross-sectional view of the disk substrate formed by the molding process described above. When the disk substrate 210 is formed by the above-described forming process, protrusions 210a are formed on the outer peripheral portion as shown in FIG. When the disk substrate 210 is formed by the above-described forming process, the region that is abruptly cooled in the disk substrate 210 is mainly an area in contact with the mold apparatus 200. Therefore, since the outer volume reduction precedes the inside of the disk substrate 210, a protrusion 210a called a ski jump is formed in the vicinity of the outermost periphery of the disk substrate 210.

  When an optical recording medium is manufactured by forming a light transmission layer on the disk substrate 210, a portion corresponding to the protrusion 210a is raised. During recording and reproduction, the objective lens may collide with the swell. Therefore, a process such as cutting the protrusion 210a in advance is required, and the generation of dust and an increase in the number of processes lead to a decrease in yield and an increase in manufacturing cost.

  Also, this collision problem is difficult to avoid even if the disk substrate 210 can be formed completely flat. That is, for example, when a light transmissive layer is formed by applying an ultraviolet curable resin on a flat disk substrate 210 by spin coating, a liquid pool is generated at the outer peripheral edge portion, and the outer peripheral portion of the light transmissive layer is raised. Will be formed.

  Accordingly, an object of the present invention is to provide a disk substrate, an optical recording medium, and a mold apparatus that can prevent the occurrence of bulge in the outer peripheral portion.

In order to solve the above-mentioned problem, the invention according to claim 1 is a disk substrate used for an optical recording medium in which information signals are recorded and / or reproduced by irradiating light to the information signal portion.
The disk substrate is characterized in that the outer peripheral portion is inclined so that the thickness is gradually reduced toward the radial direction.

  According to a second aspect of the present invention, in the disk substrate according to the first aspect, the inclination is provided in a range of 0.975R to 1.0R (where R is a radius of the disk substrate). .

According to a third aspect of the present invention, in the disk substrate according to the first aspect, the height d ₁ of the inclination is set in a range of 0.020 mm ≦ d ₁ ≦ 0.2 mm.

The invention according to claim 4 is provided on a disk substrate,
An information signal unit configured to record and / or reproduce an information signal;
A protective layer for protecting the information signal part;
Have a configuration in which
The optical recording medium is characterized in that the outer peripheral portion of the disk substrate is inclined so that the thickness of the disk substrate gradually decreases in the radial direction.

  According to a fifth aspect of the present invention, in the optical recording medium according to the fourth aspect, the protective layer is a light transmission layer configured to transmit light used for recording and / or reproducing information signals. .

  According to a sixth aspect of the present invention, in the optical recording medium of the fourth aspect, the light transmission layer is formed by applying an ultraviolet curable resin onto the disk substrate, and then bonding the light transmissive sheet and the disk substrate through the ultraviolet curable resin. It is formed by combining.

  According to a seventh aspect of the present invention, in the optical recording medium according to the fourth aspect, the light transmission layer is formed by applying and curing an ultraviolet curable resin.

  According to an eighth aspect of the present invention, in the optical recording medium according to the fourth aspect, the inclination is provided within a range of 0.975R to 1.0R (where R is a radius of the disk substrate). To do.

The invention according to claim 9 is the optical recording medium according to claim 4, wherein the inclination height d ₁ is set in a range of 0.020 mm ≦ d ₁ ≦ 0.2 mm.

The invention according to claim 10 is provided on a disk substrate.
A first information signal unit configured to record and / or reproduce an information signal;
An intermediate layer configured to transmit light used for recording and / or reproducing information signals;
A second information signal portion configured to record and / or reproduce an information signal, and a protective layer protecting the second information signal portion;
Have a configuration in which
The optical recording medium is characterized in that the outer peripheral portion of the first disk substrate is inclined so that the thickness of the disk substrate gradually decreases in the radial direction.

  According to an eleventh aspect of the present invention, in the optical recording medium according to the tenth aspect, the intermediate layer is formed by applying an ultraviolet curable resin on the first information signal portion and then curing.

  According to a twelfth aspect of the present invention, in the optical recording medium of the tenth aspect, the protective layer is a disk substrate.

  According to a thirteenth aspect of the present invention, in the optical recording medium according to the tenth aspect, the inclination is provided in a range of 0.975R to 1.0R (where R is a radius of the disk substrate). To do.

According to a fourteenth aspect of the present invention, in the disk substrate according to the tenth aspect, the inclination height d ₁ is set in a range of 0.020 mm ≦ d ₁ ≦ 0.2 mm.

The invention according to claim 15 includes a pair of molds facing each other,
In a mold apparatus in which a stamper for forming an information reading surface of a disk substrate is attached to one of molds, and a cavity is formed by abutting a pair of molds,
A mold apparatus in which a mold for mounting a stamper is provided with an inclined portion for forming an inclination for gradually decreasing the thickness toward the outer periphery of a disk substrate in the radial direction. It is.

  The invention according to claim 16 is the mold apparatus according to claim 15, wherein the inclined portion is provided within a range of at least 0.975R to 1.0R (where R is a radius of the cavity). And

According to a seventeenth aspect of the present invention, in the mold apparatus according to the fifteenth aspect, the height d ₂ of the inclination is set in a range of at least 0.020 mm ≦ d ₁ ≦ 0.2 mm.

  As described above, according to the present invention, since the outer peripheral portion of the disk substrate is inclined so that the thickness gradually decreases in the radial direction, the resin is applied onto the disk substrate by a spin coating method. Moreover, the swelling of the resin in the outer peripheral portion can be suppressed. Therefore, the resin can be uniformly applied on the disk substrate.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In all the drawings of the following embodiments, the same or corresponding parts are denoted by the same reference numerals.

Embodiments of the present invention will be described in the following order.
(1-1) Configuration of optical recording medium according to first embodiment (1-2) Configuration of mold apparatus according to first embodiment (1-3) Manufacturing method of optical recording medium according to first embodiment ( 2-1) Configuration of optical recording medium according to second embodiment (2-2) Configuration of mold apparatus according to second embodiment (2-3) Manufacturing method of optical recording medium according to second embodiment

(1-1) Configuration of Optical Recording Medium According to First Embodiment FIG. 1 is a cross-sectional view showing a configuration example of an optical recording medium 1 according to the first embodiment of the present invention. As shown in FIG. 1, the optical recording medium 1 includes a disc substrate 2, an information signal portion 3 formed on one main surface of the disc substrate 2, and a light transmission layer formed on the information signal portion 3. 4.

  In the optical recording medium 1 according to the first embodiment, information signals are recorded and / or reproduced by irradiating the information signal unit 3 with laser light from the light transmission layer 4 side. For example, laser light having a wavelength in the range of 400 nm to 410 nm is collected by an objective lens having a numerical aperture in the range of 0.84 to 0.86, and irradiated to the information signal unit 3 from the light transmission layer 4 side. As a result, the information signal is recorded and / or reproduced. An example of such an optical recording medium 1 is Blu-ray Disc (registered trademark).

  The disk substrate 2 has an annular shape with a center hole 2a formed in the center. On one main surface of the disk substrate 2 on the side where the information signal portion 3 is formed, an uneven portion is formed for guiding an optical spot when recording and / or reproducing information signals. Examples of the shape of the uneven portion include various shapes such as a spiral shape, a concentric circle shape, and a pit row. The diameter of the disk substrate 2 is selected to be 120 mm, for example. The thickness of the disk substrate 2 is selected in consideration of rigidity, preferably from 0.3 mm to 1.3 mm, more preferably from 0.6 mm to 1.3 mm, for example, 1.1 mm. .

  As a material of the disk substrate 2, for example, a plastic material such as polycarbonate resin, polyolefin resin, acrylic resin, or glass is used. In consideration of cost, it is preferable to use a plastic material as the material of the disk substrate 2.

FIG. 2 is a schematic cross-sectional view showing an example of the shape of the disk substrate 2. On one main surface of the disk substrate 2, a signal region 2b for forming the information signal portion 3 is set. The signal region 2b has an annular shape centered on the center hole 2a. Further, the outer peripheral portion of the disk substrate 2 is inclined so that the thickness of the disk substrate 2 gradually decreases toward the outer periphery. The starting point 2d of the slope 2c is provided on the outer peripheral side from the signal region 2b. That is, the slope 2 c is provided in a range between the outer periphery of the signal area 2 b and the outer periphery of the disk substrate 2. Range and height d ₁ of the inclined 2c provided on the peripheral portion, for example, consider the rotational speed such as a disk substrate 2 at the time of the ultraviolet curing resin viscosity and coating applied by spin coating on the disk substrate 2 It is preferable to select. The inclination 2c is provided, for example, in the range of 0.975R to 1.0R (where R is the radius of the disk substrate 2). Further, the height d ₁ of the slope 2c is selected in the range of 0.02 mm ≦ d ₁ ≦ 0.2 mm, for example.

  The information signal unit 3 is a reflective film or a recording film. Examples of the material of the reflective film include metal elements, metalloid elements, compounds or mixtures thereof, and more specifically, for example, Al, Ag, Au, Ni, Cr, Ti, Pd, Co, Si, Examples thereof include simple substances such as Ta, W, Mo, and Ge, or alloys containing these simple substances as a main component. In consideration of practicality, it is preferable to use an Al-based material, an Ag-based material, an Au-based material, a Si-based material, or a Ge-based material among them. The recording film is selected depending on whether the optical recording medium 1 is a write once type or a rewritable type. When the optical recording medium 1 is a write-once type, examples of the recording film include a recording film formed by sequentially laminating a reflective film and an organic dye film on the disk substrate 2. In the case where the optical recording medium 1 is a rewritable type, the recording film is configured by, for example, sequentially stacking a reflective film, a lower dielectric layer, a layer change recording film, and an upper dielectric layer on the disk substrate 2. Recording film.

  The light transmissive layer 4 includes a light transmissive sheet (film) 4b having a planar annular shape and an adhesive layer 4a for bonding the light transmissive sheet 4b to the disk substrate 2 on which the information signal portion 3 is formed. It consists of. The adhesive layer 4a is made of, for example, an ultraviolet curable resin or a pressure sensitive adhesive (PSA).

  The light transmissive sheet 4b is preferably made of a material having a low absorbability with respect to laser light used for recording and / or reproduction, specifically, a material having a transmittance of 90% or more. Examples of the material of the light transmissive sheet 4b include a polycarbonate resin material and a polyolefin resin (for example, ZEONEX (registered trademark)).

  Further, the thickness of the light transmissive sheet 4b is preferably selected to be 0.3 mm or less, and more preferably selected from the range of 3 to 177 μm. For example, the thickness of the light transmissive sheet 4b is selected so that the total thickness of the light transmissive sheet 4b and the adhesive layer 4a is, for example, 100 μm. By combining such a thin light transmission layer 4 and an objective lens having a high NA of about 0.85, high density recording can be realized.

(1-2) Configuration of Mold Device According to First Embodiment FIG. 3 is a cross-sectional view showing a configuration example of the mold device according to the first embodiment of the present invention. As shown in FIG. 3, the mold apparatus includes a fixed mold 11 and a movable mold 21, and molding is performed by abutting the fixed mold 11 and the movable mold 21. A cavity 31 that is a space is formed. In this mold apparatus, the disk substrate is molded by filling the cavity 31 with molten disk substrate material.

  The fixed-side mold 11 includes a fixed-side mirror 12 disposed so as to face the movable-side mold 21, and a stamper 32 is attached to the surface on the side where the cavity 31 is formed. An inclined portion that gradually rises in the radial direction is provided on the outer peripheral portion of the surface of the fixed mirror 12 on the side where the stamper 32 is attached.

  In addition, the fixed-side mold 11 is provided with an outer peripheral stamper retainer 13 for attaching the stamper 32. The outer circumferential stamper retainer 13 has, for example, an annular shape, and is assembled to the fixed mold 11 with a mounting screw or the like.

  The stamper 32 is an annular shape having a center hole, and irregularities corresponding to, for example, lands and grooves of the disk substrate 2 are formed on one main surface 32a thereof. The stamper 32 is attached to the fixed-side mold 11 so that the one main surface 32 a side faces the movable-side mold 21. When the stamper 32 is attached to the fixed side metal 11, the outer peripheral portion of the stamper 32 is sandwiched between the outer peripheral stamper holder 13 and the fixed side mirror 12. Further, the stamper 32 follows the inclination provided in the fixed mold 11 by utilizing the elastic deformation of the stamper 32.

  Further, a sprue bush 14 is provided at a substantially central portion of the fixed side mold 11. The sprue bush 14 has a cylindrical shape, and a resin injection hole 15 is provided at the center thereof. The resin injection hole 15 is connected to a material supply device (not shown). The molten disk substrate material is supplied from the material supply device into the cavity 31 through the resin injection hole 15.

  On the other hand, the movable side mold 21 is disposed to face the fixed side mold 11 and can be moved close to and away from the fixed side mold 11 by guide means (not shown). The movable die 21 has a gate cut punch 24 that cuts the central portion of the disk substrate solidified in the cavity 31 at a substantially central portion thereof, and an extrusion pin 25 that pushes out the central portion cut by the gate cut punch 24. And an ejector 23 for releasing the disk substrate from the movable mold. Further, the movable side mold 21 includes an outer peripheral ring 16 on the outer peripheral portion on the side facing the fixed side mold 11.

  The gate cut punch 24 cuts the runner portion of the disk substrate material supplied from the sprue bush 14 into the cavity 31 and solidified, and has an outer diameter substantially the same as the center hole 1a of the disk substrate 1. have. The gate cut punch 24 can be moved in a direction protruding into the cavity 31 by guide means or drive means (not shown).

  The extrusion pin 25 is formed in a rod shape and is arranged at the center of the gate cut punch 24. The push pin 25 is movable in a direction protruding into the cavity 31 by a guide means and a drive means (not shown), and removes the portion cut by the gate cut punch 24 described above. Therefore, after the disk substrate material filled in the cavity 31 is solidified, the extrusion pin 25 is pushed out, whereby the runner portion and the sprue, that is, the disk substrate material accumulated in the supply portion of the runner portion and the sprue bush 14 are collected. And can be removed.

  The ejector 23 is configured to have a cylindrical shape having an inner diameter substantially the same as the outer diameter of the gate cut punch 24, and is disposed so as to surround the gate cut punch 24. The ejector 23 can be moved in a direction protruding into the cavity 31 by guide means and driving means (not shown). Therefore, after the disk substrate material is filled in the cavity 31 and the center hole of the disk substrate is formed as described above, the ejector 23 presses the inner peripheral side of the disk substrate to remove the disk substrate from the movable mold 21. Release.

  The outer ring 16 is pressed against the fixed mold 11 with a predetermined pressure by air. For example, a clearance of 5 to 30 μm is secured between the outer ring 16 and the stamper 32 so that the stamper 32 is not obstructed when it expands and contracts due to heat.

  Next, a processing method of the fixed side mirror 12 will be described with reference to FIGS. FIG. 4 is a cross-sectional view showing a configuration example of a processing apparatus for processing the fixed side mirror 12. FIG. 5 is a top view showing a configuration example of a processing apparatus for processing the fixed side mirror 12. FIG. 6 is a schematic cross-sectional view showing an example of the shape of the fixed-side mirror 12.

  First, pre-processing is performed on the fixed-side mirror 12 that is a workpiece (object). That is, the flat portion 12b corresponding to the signal region 2b of the disk substrate 2 and the inclined portion 12c corresponding to the inclination 2c of the disk substrate 2 are processed. At that time, it is preferable that the flatness of the flat portion 12b is 3 μm or less, and the surface roughness Rz of the flat portion 12b and the inclined portion 12c is 3 μm or less. Also, in the case of grinding, scratches (scratches caused by falling off of abrasive grains) cannot be removed in the final lap, so that there are few scratches. Also, the surface roughness should be uniform over the entire surface.

  What is necessary for the mold function is the outer diameter and flatness of the flat portion 12 b corresponding to the signal region 2 b of the disc substrate 2 and the height of the inclined portion 12 c corresponding to the tilt 2 c of the disc substrate 2. In the above-described pre-processing, it is preferable that the flat portion 12b and the inclined portion 12c are smoothly connected. However, when processed as described above, generally, the boundary between the flat portion 12b and the inclined portion 12c. A step will be formed in.

  FIG. 7 is a schematic diagram showing the inclined portion 12c starting from a position higher than the plane portion 12b. FIG. 8 is a schematic line portion showing the inclined portion 12c starting from a position lower than the plane portion 12b. As shown in FIG. 7, when the inclined portion 12c starts from a position higher than the flat surface portion 12b, when the stamper 32 is mounted on the stationary mold 11, the stamper 32 is lifted from the flat surface portion 11b in the vicinity of the boundary 11d. turn into. As a result, an outer diameter corresponding to the signal area 2b of the disk substrate 2 cannot be secured. Therefore, as shown in FIG. 8, it is preferable that the inclined portion 12c starts from a position lower than the plane portion 12b.

  Next, a finishing process (final process) is performed on the workpiece (object) that has been subjected to the previous process as described above. Table 1 shows an example of processing conditions when a finishing allowance of 0.01 mm is processed. The workpiece is a chrome alloy stainless tool steel quenched into HRc 52-54.

  First, the structure of the processing apparatus which processes a metal mold | die is demonstrated easily. The table 41 is configured to be able to fix a workpiece. Further, the table 41 is configured to be rotatable and driven at a rotational speed of 0.2 to 1 pm, for example, by a driving device (not shown) with the center as a rotation axis. A pad 3 is fixed to the end of the fixing jig 4. For example, diamond paste is infiltrated into the pad 3. The fixing jig 42 is configured to be rotationally driven at a rotational speed of, for example, 40 to 2000 rpm by a driving device (not shown) with the center as a rotational axis. Furthermore, the fixing jig 42 is configured to be movable in the directions of arrows c and b (see FIG. 5) by a driving device (not shown).

  Mirror surface processing is performed using the drive device having the above-described configuration. That is, the pad 42 and the fixed mold 41 that is a work are rotated. Then, the fixing jig 42 is pressed in the direction indicated by the arrow a so that the fixed die 41 is brought into contact with the fixed side mold 41 and a desired pad pressure is applied. Thereby, for example, the contact surface between the fixed-side mirror 12 and the pad 43 is mirror-finished by diamond abrasive grains in the diamond paste soaked in the pad. The smaller the size of the diamond abrasive grain, the finer the finished surface is obtained, and the larger the diamond abrasive grain, the rougher the finished surface is obtained. Further, the processing time becomes longer as the size of the diamond abrasive grain becomes smaller, and the processing time becomes shorter as the size becomes larger.

  Therefore, as described in Table 1, when a high-quality surface is not required as a mirror-finished surface, for example, diamond abrasive grains of 3 μm are used as a finishing process, and when a high-quality finished surface is required, As the finishing process, for example, diamond abrasive grains of 0.5 μm are used.

(1-3) Optical Recording Medium Manufacturing Method according to First Embodiment

(Disk substrate molding process)
Next, an example of a method for manufacturing the optical recording medium 1 according to the first embodiment of the present invention will be described.
First, the movable mold 21 is moved in a direction approaching the fixed mold 11, and the fixed mold 11 and the movable mold 21 are brought into contact with each other to form the cavity 31.

  Next, the melted disk substrate material is filled into the cavity 31. As the disk substrate material, for example, a synthetic resin material such as polycarbonate can be used. The disk substrate material is heated and melted in the material supply device, and is supplied into the cavity 31 through the resin injection hole 15 as a supply path.

  Next, the disk substrate material filled in the cavity 31 is cooled and solidified, and the disk substrate material is clamped. When clamping the disk substrate material, the movable mold 21 is moved in a direction closer to the fixed mold 11. As a result, the disk substrate material filled in the cavity 31 is pressurized, and irregularities such as grooves or pits formed on one main surface 32a of the stamper 32 are reliably transferred.

  Next, after the disk substrate material is sufficiently cooled and solidified, the gate cut punch 24 is moved in a direction approaching the fixed mold 11, that is, a direction protruding into the cavity 31. By moving the gate cut punch 24 in a direction protruding into the cavity 31, the runner portion and the spool portion of the solidified disk substrate material can be cut. As a result, the center hole is formed after the disk substrate material filled in the cavity 31 is solidified.

  Next, the movable mold 21 is moved away from the fixed mold 11. As a result, the solidified disk substrate is separated from the stamper 32 attached to the fixed mold 11 and one main surface is exposed to the outside.

Next, by moving the push pin 25 in the direction of protruding into the cavity 31, the portion cut by the gate cut punch 24 is removed. Next, the ejector 23 is moved in a direction protruding into the cavity 31, thereby pressing the inner periphery of the disk substrate and releasing the disk substrate from the movable mold 21.
Through the above steps, the disk substrate 1 according to the first embodiment of the present invention is formed.

(Information signal part formation process)
Next, the information signal portion 2 is formed on the disk substrate 1 by, for example, sputtering. Specifically, for example, when the optical recording medium as a final product is a read-only type, Al, on one main surface where the irregularities of the disk substrate 1 are formed, for example, by vacuum deposition or sputtering, A reflective layer made of Al alloy or Ag alloy is formed.

(Light transmission layer forming process)
Next, an ultraviolet curable resin is applied to one main surface of the disk substrate 1 on which the information signal portion 2 is formed, for example, by spin coating. Here, the viscosity of the ultraviolet curable resin is in the range of 1000 to 3000 cp, for example, 2000 cp. The rotation speed of the disk substrate 1 is in the range of 1000 to 10000 rpm, for example, 3000 rpm.

  Next, the light transmissive sheet 4b is placed on the surface of the disk substrate 2 on which the ultraviolet curable resin is applied, and the ultraviolet curable resin is irradiated with ultraviolet rays. As a result, the ultraviolet curable resin is cured, and the light transmissive sheet 4 b is bonded to the disk substrate 1 to form the light transmissive layer 4. Alternatively, the light transmission layer 4 may be formed by uniformly applying a resin such as an ultraviolet curable resin to the one main surface of the disk substrate 1 on which the information signal portion 2 is formed by spin coating and then curing the resin. .

In the method of adhering the light-transmitting sheet, since the requirements for the optical characteristics and thickness accuracy of the light-transmitting layer are severe, the manufacturing cost tends to increase. In addition, it has been pointed out that this method tends to deteriorate the electrical characteristics due to the adhesive. Considering this point, a method of forming the light transmission layer 4 by a spin coating method, which is relatively easy to satisfy the above requirement, is preferable.
Through the above steps, the optical recording medium 1 according to the first embodiment of the present invention can be obtained.

  In addition, the present inventor conducted the following examination in order to verify the position that is the starting point of the rising of the ultraviolet curable resin in the outer peripheral portion. FIG. 9 is a cross-sectional view schematically showing the outer periphery of the disk substrate before and after application of the ultraviolet curable resin.

  First, a disk substrate having a diameter of 120 mm and a thickness of 1.1 mm was produced by a conventional mold apparatus. Then, when the outer peripheral portion of the disk substrate was observed, as shown in FIG. 9, a bulge having a height of 7 μm was formed on the outer peripheral portion of the disk substrate, starting from a radius of 59 mm.

  Next, after forming an information signal portion on the disk substrate, an ultraviolet curable resin was applied by spin coating. The viscosity of the ultraviolet curable resin was 2000 cp, and the rotational speed of the disk substrate was 3000 rpm. Thereafter, when the outer peripheral portion of the disk substrate was observed, as shown in FIG. 9, a bulge having a height of 15 μm was formed on the outer peripheral portion of the disk substrate, starting from a radius of 59 mm.

  Then, when the viscosity of the ultraviolet curable resin was appropriately changed in the range of 1000 to 3000 cp and an optical recording medium was produced in the same manner as described above, the starting point of swell was 0.0975R to 1.0R (where R = 120 mm). Moreover, it was confirmed that the height of the swell is 0.02 to 0.20 mm.

  Considering the verification results described above, the inclination 2c of the disk substrate 2 is preferably provided in the range of 0.0975R to 1.0R (where R = 120 mm), and the height of the inclination 2c is 0.02 to 0.0. It is preferable to set in the range of 20 mm.

According to the first embodiment of the present invention, the following effects can be obtained.
An inclined portion 12c that gradually rises in the radial direction is provided on the outer peripheral portion of the surface on which the stamper 32 of the fixed mold 11 is mounted. The disk substrate 2 having an inclined portion can be formed. Therefore, when the ultraviolet curable resin is applied on the disk substrate 2 by the spin coat method, the bulge of the ultraviolet curable resin in the outer peripheral portion can be suppressed. Therefore, the light transmission layer 4 having excellent uniformity can be formed on the disk substrate 2.

(2-1) Configuration of Optical Recording Medium According to Second Embodiment FIG. 10 is a cross-sectional view showing a configuration example of an optical recording medium according to the second embodiment of the present invention. As shown in FIG. 10, the optical recording medium 101 includes a first disk substrate 102, a first information signal unit 103 formed on one main surface of the first disk substrate 102, and an information signal unit 103. Formed on the intermediate layer 104, the second information signal unit 105 formed on the intermediate layer 104, the protective layer 106 formed on the second information signal unit 105, and the protective layer 106. And a second disk substrate 107.

  In the optical recording medium 101 according to the second embodiment, the information signal is recorded by irradiating the first information signal unit 103 or the second information signal unit 105 with laser light from the first disk substrate 102 side. And / or playback is performed. For example, a laser beam having a wavelength in the range of 650 to 665 nm is condensed by an objective lens having a numerical aperture of about 0.65, and the first information signal unit 103 or the second information signal from the first disk substrate 102 side. The information signal is recorded and / or reproduced by irradiating the information signal unit 105.

  The first disk substrate 102 and the second disk substrate 107 have an annular shape with a center hole 102a formed in the center. On one main surface of the first disk substrate 102, an uneven portion for guiding an optical spot when recording and / or reproducing an information signal is formed. Examples of the shape of the uneven portion include various shapes such as a spiral shape, a concentric circle shape, and a pit row. The diameters of the first disk substrate 102 and the second disk substrate 107 are selected to be 120 mm, for example. The thicknesses of the first disk substrate 102 and the second disk substrate 107 are selected in consideration of rigidity, for example, 0.6 mm.

  As the material of the first disk substrate 102 and the second disk substrate 107, for example, a plastic material such as polycarbonate resin, polyolefin resin, or acrylic resin, glass, or the like is used. In consideration of cost, it is preferable to use a plastic material as the material of the disk substrate 2.

An information signal area for forming the first information signal unit 103 is set on one main surface of the first disk substrate 102. This signal area has an annular shape centering on the center hole 102a. Further, the outer periphery of the first disk substrate 102 is inclined so that the thickness of the second disk substrate 102 becomes thinner toward the outer periphery. The starting point of the inclination is provided on the outer peripheral side from the signal area. That is, the inclination is provided in a range between the outer periphery of the signal area and the outer periphery of the first disk substrate 102. The range and height of the inclination provided on the outer peripheral portion are, for example, the viscosity of the ultraviolet curable resin applied on the first disk substrate 102 by spin coating and the number of rotations of the first disk substrate 102 at the time of application. It is preferable to select in consideration of the above. The inclination is provided in the range of, for example, 0.975R to 1.0R (where R is the radius of the second disk substrate 102). Further, the height of the inclination is selected in the range of 0.02 mm ≦ d ₁ ≦ 0.2 mm, for example.

  The first information signal unit 103 and the second information signal unit 105 are reflection films or recording films. Examples of the material of the reflective film include metal elements, metalloid elements, compounds or mixtures thereof, and more specifically, for example, Al, Ag, Au, Ni, Cr, Ti, Pd, Co, Si, Examples thereof include simple substances such as Ta, W, Mo, and Ge, or alloys containing these simple substances as a main component. In consideration of practicality, it is preferable to use an Al-based material, an Ag-based material, an Au-based material, a Si-based material, or a Ge-based material among them. The recording film is selected depending on whether the optical recording medium 101 is a write once type or a rewritable type. When the optical recording medium 101 is a write-once type, examples of the recording film include a recording film formed by sequentially laminating a reflective film and an organic dye film on the first disk substrate 102. When the optical recording medium 101 is a rewritable type, as the recording film, for example, a reflective film, a lower dielectric layer, a layer change recording film, and an upper dielectric layer are sequentially laminated on the first disk substrate 102. And a recording film configured as described above.

  The intermediate layer 104 has a concavo-convex portion for guiding an optical spot when recording and / or reproducing an information signal. Examples of the shape of the uneven portion include various shapes such as a spiral shape, a concentric circle shape, and a pit row. The thickness of the intermediate layer 104 is selected from a range of 0.01 to 0.06 mm, for example, and is selected to be 0.04 mm, for example. The intermediate layer 104 is made of, for example, an ultraviolet curable resin.

  The protective layer 106 protects the second information signal unit 105 and is used to bond the first disk substrate 102 and the second disk substrate 107 together. The protective layer 106 is made of, for example, an ultraviolet curable resin.

(2-2) Configuration of the mold apparatus according to the second embodiment Except for appropriately adjusting the shape of the cavity and the like according to the shapes of the first disk substrate 102 and the second disk substrate 107 desired. Since this is the same as in the first embodiment, description thereof is omitted here.

(2-3) Optical Recording Medium Manufacturing Method (Disc Substrate Forming Process) According to Second Embodiment
The process of forming the first disk substrate 102 is substantially the same as that in the first embodiment described above, and thus the description thereof is omitted.

(First information signal portion forming step)
Next, the first information signal portion 103 is formed on the surface of the first disk substrate 102 on which the unevenness is formed, for example, by sputtering.

(Intermediate layer forming process)
Next, for example, an ultraviolet curable resin is applied by a spin coating method, and a stamper is pressed against the ultraviolet curable resin to irradiate ultraviolet rays. Thereby, the ultraviolet curable resin is cured, and the intermediate layer 104 having the uneven pattern is formed. Here, the viscosity of the ultraviolet curable resin is in the range of 1000 to 3000 cp, for example, 2000 cp. The rotation speed of the first disk substrate 102 is in the range of 1000 to 10000 rpm, for example, 3000 rpm.

(Second information signal portion forming step)
Next, the second information signal portion 105 is formed on the intermediate layer 104 by, for example, sputtering.

(Lamination process)
Next, an ultraviolet curable resin is uniformly applied on the second information signal portion 105 by, for example, a spin coating method. Then, the second disk substrate 107 is placed on the first disk substrate 102, the thickness of the ultraviolet curable resin is adjusted as appropriate, and ultraviolet rays are irradiated. As a result, the ultraviolet curable resin is cured, and the first disk substrate 102 and the second disk substrate 107 are bonded together to form the protective layer 106.
Through the above steps, the target optical recording medium 101 according to the second embodiment can be obtained.

  In addition, the present inventor conducted the following examination in order to verify the position that is the starting point of the rising of the ultraviolet curable resin in the outer peripheral portion. FIG. 11 is a cross-sectional view schematically showing the outer periphery of the disk substrate before and after application of the ultraviolet curable resin.

  First, a first disk substrate having a diameter of 120 mm and a thickness of 0.6 mm was produced by a conventional mold apparatus. Then, when the outer peripheral portion of the first disk substrate was observed, as shown in FIG. 11, a bulge having a height of 5 μm was formed on the outer peripheral portion of the first disk substrate, starting from a radius of 59 mm. It was.

  Next, after forming the first information signal portion on the first disk substrate, an ultraviolet curable resin was applied by spin coating. The viscosity of the ultraviolet curable resin was 2000 cp, and the rotation speed of the first disk substrate was 3000 rpm. Thereafter, when the outer peripheral portion of the first disk substrate 102 was observed, as shown in FIG. 11, a bulge having a height of 15 μm was formed on the outer peripheral portion of the disk substrate, starting from a radius of 59 mm.

  Then, when the viscosity of the ultraviolet curable resin was appropriately changed in the range of 1000 to 3000 cp and an optical recording medium was produced in the same manner as described above, the starting point of the protrusion was 0.0975R to 1.0R (where R = 120 mm). Moreover, it was confirmed that the height of the swell is 0.02 to 0.20 mm.

  Considering the verification results described above, the inclination 2c of the disk substrate 2 is preferably provided in the range of 0.0975R to 1.0R (where R = 120 mm), and the height of the inclination 2c is 0.02 to 0.0. It is preferable to set in the range of 20 mm.

According to the second embodiment of the present invention, the following effects can be obtained.
An inclined portion 12c that gradually rises in the radial direction is provided on the outer peripheral portion of the surface on which the stamper 32 of the fixed mold 11 is mounted. The first disk substrate 102 having an inclined portion can be formed. Therefore, when the ultraviolet curable resin is applied on the first disk substrate 102 by the spin coating method, the swell of the ultraviolet curable resin in the outer peripheral portion can be suppressed. Therefore, the intermediate layer 104 having excellent uniformity can be formed on the first disk substrate 102.

  The first and second embodiments of the present invention have been specifically described above. However, the present invention is not limited to the first and second embodiments described above, and is based on the technical idea of the present invention. Various variations based on this are possible.

  For example, the numerical values given in the first and second embodiments are merely examples, and different numerical values may be used as necessary.

  In the first and second embodiments described above, the case where the disk substrate having the outer peripheral portion inclined so as to gradually decrease in thickness in the radial direction is shown as an example. By appropriately adjusting the angle of inclination provided on the outer peripheral portion, a flat disc substrate having no protrusion on the outer peripheral portion is formed, and for example, an information signal portion, a light transmission layer, etc. are appropriately formed on the disc substrate. You may do it. In consideration of manufacturing an optical recording medium having an information reading surface with excellent flatness, an inclination is provided on the outer peripheral portion of the disk substrate as in the first and second embodiments described above. Is preferred.

It is sectional drawing which shows one structural example of the optical recording medium by 1st Embodiment of this invention. It is a typical sectional view showing an example of shape of a disk substrate by a 1st embodiment of this invention. It is sectional drawing which shows the example of 1 structure of the metal mold | die apparatus by 1st Embodiment of this invention. It is sectional drawing which shows the example of 1 structure of the processing apparatus for processing a fixed side metal mold | die. It is a top view which shows one structural example of the processing apparatus for processing a fixed side metal mold | die. It is typical sectional drawing which shows one example of a fixed side metal mold | die. It is a basic diagram which shows the inclination part which starts from a position higher than a plane part. It is a substantially line part which shows the inclination part which starts from a position lower than a plane part. It is sectional drawing which shows typically the outer peripheral part of the disc board | substrate before and behind ultraviolet curable resin application. It is sectional drawing which shows the example of 1 structure of the optical recording medium by the 2nd Embodiment of this invention. It is sectional drawing which shows typically the outer peripheral part of the disc board | substrate before and behind ultraviolet curable resin application. It is sectional drawing which shows the structure of the conventional metal mold apparatus typically. It is sectional drawing of the disc board | substrate shape | molded using the conventional metal mold apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Optical recording medium, 2 ... Disc substrate, 2a ... Center hole, 2b ... Signal area, 2c ... Inclination, 2d ... Starting point, 3 ... Information signal part, 4・ ・ ・ Light transmissive layer, 11 ・ ・ ・ Fixed side mold, 12 ・ ・ ・ Moveable side mold, 12b ・ ・ ・ Plane part, 12c ・ ・ ・ Inclined part, 12d ・ ・ ・ Boundary, 101 ・ ・ ・ Light Recording medium 102 ... first disk substrate 103 ... first information signal part 104 ... intermediate layer 105 ... second information signal part 106 ... protective layer 107 ... Second disk substrate

Claims (17)

In a disk substrate used for an optical recording medium in which information signals are recorded and / or reproduced by irradiating light to the information signal portion,
A disk substrate characterized in that the outer peripheral portion is inclined so that the thickness is gradually reduced in the radial direction.   2. The disk substrate according to claim 1, wherein the inclination is provided in a range of 0.975R to 1.0R (where R is a radius of the disk substrate). 2. The disk substrate according to claim 1, wherein the inclination height d ₁ is set in a range of 0.020 mm ≦ d ₁ ≦ 0.2 mm. On the disk substrate,
An information signal unit configured to record and / or reproduce an information signal;
A protective layer for protecting the information signal part;
Have a configuration in which
An optical recording medium characterized in that the outer peripheral portion of the disk substrate is inclined so that the thickness of the disk substrate gradually decreases in the radial direction.   5. The optical recording medium according to claim 4, wherein the protective layer is a light transmission layer configured to transmit light used for recording and / or reproducing the information signal.   5. The light transmissive layer is formed by applying an ultraviolet curable resin on the disk substrate and then bonding the light transmissive sheet and the disk substrate through the ultraviolet curable resin. Optical recording media.   5. The optical recording medium according to claim 4, wherein the light transmission layer is formed by applying an ultraviolet curable resin and then curing.   5. The optical recording medium according to claim 4, wherein the inclination is provided in a range of 0.975R to 1.0R (where R is a radius of the disk substrate). 5. The optical recording medium according to claim 4, wherein the height d _{1 of the} inclination is set in a range of 0.020 mm ≦ d ₁ ≦ 0.2 mm. On the disk substrate,
A first information signal unit configured to record and / or reproduce an information signal;
An intermediate layer configured to transmit light used for recording and / or reproducing information signals;
A second information signal portion configured to record and / or reproduce an information signal, and a protective layer protecting the second information signal portion;
Have a configuration in which
An optical recording medium, wherein the outer peripheral portion of the first disk substrate is inclined so that the thickness of the disk substrate gradually decreases as it goes in the radial direction. 11. The optical recording medium according to claim 10, wherein the intermediate layer is formed by applying an ultraviolet curable resin on the first information signal portion and then curing.   The optical recording medium according to claim 10, wherein the protective layer is a disk substrate.   11. The optical recording medium according to claim 10, wherein the inclination is provided in a range of 0.975R to 1.0R (where R is a radius of the disk substrate). 11. The optical recording medium according to claim 10, wherein the height d _{1 of the} inclination is set in a range of 0.020 mm ≦ d ₁ ≦ 0.2 mm. A pair of molds facing each other,
In a mold apparatus in which a stamper for forming an information reading surface of a disk substrate is attached to one of the molds, and a cavity is formed by abutting the pair of molds,
The mold to which the stamper is attached is provided with an inclined portion for forming an inclination on the outer peripheral portion of the disk substrate to gradually reduce the thickness in the radial direction. apparatus.   The mold apparatus according to claim 15, wherein the inclined portion is provided in a range of at least 0.975R to 1.0R (where R is a radius of the cavity). 16. The mold apparatus according to claim 15, wherein the height d _{2 of the} inclination is set in a range of at least 0.020 mm ≦ d ₁ ≦ 0.2 mm.

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