JP2001273676A - Optical disk substrate and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical disk substrate which a high density minute recording signal section necessary for constituting a high capacity high density optical disk can accurately be transferred onto the resin substrate. SOLUTION: This optical disk substrate 1 is formed by fusing a resin to be used for forming a resin substrate main body 4 and another resin to be used for forming the recording signal section 6 on the surface of the main body 4 to integrate them into one body. The resins different in physical properties, particularly in melting point are used. If the section 6 is formed by using the resin having the melting point lower than that of the resin to be used for forming the main body 4, the section 6 can be made in a lower viscosity state without raising the resin temperature or the die temperature. Therefore the minutely uneven shape constituting the section 6 can accurately be transferred by resin molding.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk substrate serving as a base of an optical disk such as a CD or a DVD, and more particularly to an optical disk substrate requiring a fine recording density such as a DVD. It is characterized by the following.

[0002]

2. Description of the Related Art Many CD products, such as CD-ROMs recording computer data and video CDs incorporating moving images, have been triggered by CDDA (Compact Disk Digital Audio), which appeared in place of LP records. It is well known that it has been commercialized. This CD cannot cope with long-time moving image recording such as a movie or recording of a large amount of computer data, and DVDs have been commercialized to meet such a demand for large capacity and high density. In addition, CD-R, DVD-R, DV that enables both recording and data writing and reading
D-RAM and the like have also been commercialized.

In these optical disks, as shown in FIG. 7, a recording signal portion 31 is formed on the surface and an optical disk substrate 3 is formed.
0 is basically manufactured by resin molding.
When the optical disk substrate 30 is a read-only type such as a CDDA or a DVD, that is, a ROM type, the recording signal section 31 is formed with pits indicating digital signals, and
In the case of a RAM that supports both reading and writing, such as R, DVD-R, and DVD-RAM, the recording signal portion 31 has a groove (groove).

When an optical disk substrate 30 is formed from a single material such as polycarbonate or acrylic resin by resin injection molding or injection compression molding, the recording signal portion is formed on the surface of the disk. 31 are formed. FIG. 8 shows a configuration of an injection compression molding die apparatus for resin-molding the optical disk substrate 30. A nozzle 37 is provided in a die having an upper die 33 and a lower die 34 provided with a stamper 35. The melted resin is injected through the gate 36, a pressure is applied to mold the disk, and at the same time, the recording signal portion 31 is formed on the disk surface by the stamper 35.

[0005] On the optical disc substrate 30 on which the recording signal section 31 is formed, an optical disc is formed by forming a reflection layer on the recording signal section 31 and further forming a protective layer thereon. This structure is basically common to ROM-type optical disks. In the optical disc of the RAM type, a recording layer is formed between the recording signal section 31 and the reflection layer, and reading and writing of a signal are enabled by irradiating the recording layer with a laser beam.

[0006]

The recording capacity of the optical disk has been remarkably increased, and the size of the pit or groove serving as the recording signal section 31 has been reduced. For example, in the current DVD, the minimum pit has a width of 0.3 μm and a height of 0.3 μm.
The track pitch is 1 μm and the track pitch is 0.74 μm, and these values are expected to be about 程度 in the future.

When the unevenness forming the recording signal portion 31 is reduced, the stamper 35 is formed by resin molding.
Therefore, it is difficult to accurately transfer the recording signal portion 31 to the surface of the optical disk substrate 30. In response, measures such as raising the resin temperature during molding to lower the viscosity of the molten resin and raising the mold temperature to delay the formation of a solidified layer of the resin in contact with the mold have been taken. The transfer property of the recording signal section 31 is ensured.

However, if the resin temperature is raised more than necessary,
The resin may be thermally decomposed and the material properties may be impaired. In addition, when the mold temperature is increased, the time required for cooling the resin is increased, and there is a problem that the molding cycle is lengthened.

An object of the present invention is to provide a configuration of an optical disk substrate capable of obtaining an optical disk substrate having a high recording density without raising the resin temperature or the mold temperature, and a method of manufacturing the same.

[0010]

According to a first aspect of the present invention, there is provided an optical disk substrate having a recording signal portion formed on a surface of a resin substrate, wherein the recording signal portion is formed on a resin substrate. The surface layer is formed of a resin having different physical properties from the resin constituting the resin substrate body.

According to this structure, the resin substrate main body is formed of a resin having physical properties capable of maintaining the strength and flatness required for the substrate, and the surface layer forming the recording signal portion on the surface thereof has a fine recording signal portion. It can be formed of a resin having physical properties suitable for accurately forming a rough uneven shape. Even for an optical disc substrate with a high recording density, the resin temperature and the mold temperature during resin molding are increased and the resin is molded. An optical disk substrate can be formed without any need.

The difference in the physical properties of the above configuration is that the surface layer of the resin substrate forming the recording signal portion can be applied to the formation of a resin having a melting point lower than the melting point of the resin forming the resin substrate body. Since the melt viscosity of the surface portion of the substrate decreases without increasing the resin temperature, it is possible to cope with the formation of a fine recording signal portion.

Further, the surface layer portion of the resin substrate forming the recording signal portion can be formed by using a resin of a different material from the resin forming the resin substrate body. By disposing it on the surface, the melt viscosity of the surface portion of the resin substrate having a low melting point decreases without increasing the resin temperature or the mold temperature, so that it is possible to cope with the formation of a fine recording signal portion.

The second invention of the present application is a method for manufacturing an optical disk substrate, wherein a recording signal portion is formed on the surface of the resin substrate by a stamper provided in a resin molding die, and the optical disk substrate is resin-molded. Disposing a resin film having a low melting point on the stamper side, injecting a resin having a melting point higher than the melting point of the resin film into a mold to form a resin substrate body, and fusing the resin film to the surface thereof. The recording signal portion is formed on a resin film by the stamper.

According to this manufacturing method, since the recording signal portion has a fine uneven shape, the recording signal portion can be formed as thin as a resin film. When the resin is melted by the applied resin, the viscosity is low and the fluidity is high, so that the concave and convex shape of the stamper can be accurately transferred, and it can be applied to a fine recording signal portion such as a DVD.

The third invention of the present application is a method for manufacturing an optical disk substrate, wherein a recording signal portion is formed on the surface of the resin substrate by a stamper disposed in a resin molding die, and the optical disk substrate is resin-molded. Injecting the low melting point resin into the mold from the stamper side, and injecting the resin forming the resin substrate body into the mold from the side facing the stamper side, forming the recording signal portion in the low melting point resin. The optical disk substrate is formed by molding the optical disk substrate.

According to this manufacturing method, the optical disc substrate is formed in two layers by the resin for molding the resin substrate body and the low melting point resin for molding the recording signal portion, and the recording signal portion is transferred from the stamper to the low melting point resin. You. The low melting point resin has a low viscosity and is rich in fluidity, can accurately transfer the concave and convex shape of the stamper, and can correspond to a minute recording signal portion such as a DVD.

Further, a fourth invention of the present application is a method for manufacturing an optical disk substrate in which a recording signal portion is formed on the surface of a resin substrate by a stamper disposed in a resin molding die and the optical disk substrate is resin-molded. By injecting a low-melting resin from the same gate into the mold and subsequently injecting a high-melting resin, a resin substrate is formed by sandwich molding in which the high-melting resin is covered with the low-melting resin, and the stamper is formed. The optical disc substrate is formed by forming the recording signal portion on a low melting point resin.

According to this manufacturing method, the low-melting-point resin is in a low-viscosity state, and flows so as to enclose the high-melting-point resin in the high-viscosity state. The recording signal is transferred from the stamper to the molded, low-melting resin that becomes the outer skin. The low melting point resin in a low viscosity state is rich in fluidity, and the heat of the internal high melting point resin delays the formation of a solidified layer. It is possible to correspond to a simple recording signal portion.

[0020]

Embodiments of the present invention will be described below with reference to the accompanying drawings to provide an understanding of the present invention.
The embodiment described below is an example embodying the present invention, and does not limit the technical scope of the present invention.

FIG. 1 shows a configuration of an optical disk substrate 1 according to a first embodiment of the present invention. As shown in a partially enlarged manner, the optical disk substrate 1 forms a resin substrate body 4. A transparent thermoplastic resin and a recording signal portion 6 on the surface layer
The transparent thermoplastic resin film 7 formed with the above is integrally fused by resin molding. Since the resin film 7 is formed of a transparent thermoplastic resin having a melting point lower than the melting point of the transparent thermoplastic resin forming the resin substrate body 4, the resin film 7 has good fluidity when melted, and has a resin temperature,
It is possible to accurately form the recording signal portion 6 having a fine uneven shape without increasing the mold temperature.

A method of manufacturing the optical disk substrate 1 having the above configuration will be described with reference to FIG. The resin molding apparatus shown in FIG. 2 is configured as an injection compression molding apparatus that injects a resin into a mold and then applies compression to mold the resin.

In FIG. 2, a lower die 1 constituting a forming die is shown.
A stamper 8 for transferring the recording signal portion 6 to the optical disk substrate 1 is provided on the optical disc substrate 1, and a resin film 7 made of a transparent thermoplastic resin (for example, polycarbonate) is disposed on the stamper 8. The space between the upper mold 9 and the lower mold 10 is closed.
Is injected into a mold and compressed, whereby the resin film 7 is pressed against the stamper 8 and melted and integrated by the injected resin to form the stamper 8. The fine irregularities formed on the substrate are transferred. The resin film 7
Is configured such that a long film can be intermittently fed from the supply roll 23a to the take-up roll 23b through the lower die 10, and is punched into a disk-shaped circle by closing the die.

For example, the resin film 7 is made of polycarbonate having a melting point of 200 ° C., the mold temperature is set to 110 ° C., and the melting point of 220 ° C. for forming the resin substrate body 4 in the mold is set.
When the polycarbonate is injected, the resin film 7 is melted by the heat of the injected resin and integrated with the injected resin, and is melted into a low viscosity state. Therefore, the uneven shape of the stamper 8 is accurately transferred.

Since the height of the pits or grooves serving as the recording signal portions 6 is about 150 nm, it is considered that the resin film 7 can be formed by an extremely thin film. When the resin forming the substrate main body 4 is injected, the resin main body 4 breaks when it is injected.
Does not cover the entire surface of the Therefore, the resin film 7 has a thickness of 0.05 to 0.1 mm,
As shown in FIG. 1, this is suitable for forming the recording signal portion 6 on the surface of the resin substrate main body 4.

Next, an optical disk substrate 2 according to a second embodiment of the present invention will be described. FIG. 3 shows the configuration of the optical disk substrate 2 according to the second embodiment, in which the recording signal layer 13 made of a resin having a melting point lower than the melting point of the resin forming the resin substrate body 12 forms the resin substrate body 12.
The recording signal portion 6 is formed on the recording signal layer 13 by two-layer molding covering one surface of the recording signal layer. Since the recording signal portion 6 is formed on the recording signal layer 13 made of a low melting point resin, the viscosity at the time of molding is low and the flowability is good, and the pits or grooves are finely formed as in DVD. In addition, the shape of the stamper 8 can be accurately transferred by easily following fine irregularities.

A method of manufacturing the optical disk substrate 2 will be described with reference to FIG. A stamper 8 is disposed on an upper die 14 constituting an injection compression molding die, and an upper nozzle 17 for injecting a low-melting transparent thermoplastic resin for forming a recording signal layer 13 into the die is provided on the upper die 14 side. Provided, lower mold 1
On the fifth side, a lower nozzle 19 for injecting a high melting point transparent thermoplastic resin forming the resin substrate body 12 into the mold is provided.

The space between the upper mold 14 and the lower mold 15 is closed, a low-melting resin (for example, polycarbonate having a melting point of 200 ° C.) is injected into the mold from the upper nozzle 17 through the upper gate 18, and the lower gate 19 is injected into the lower gate. Through 20, a high melting point resin (for example, polycarbonate having a melting point of 220 ° C.) is injected into a mold. When the injection timing from the upper nozzle 17 and the lower nozzle 19 is exactly the same, or when the injection from the upper nozzle 17 is earlier by 0 to 0.05 seconds, the two-layer molding is favorably performed. Since the low melting point resin comes into contact with the stamper 8, the unevenness of the stamper 8 follows the uneven shape of the stamper 8 in a state of low viscosity and good fluidity, and a compression operation is added to the mold, so that the uneven shape of the stamper 8 is accurately determined. Transcribed.

Next, an optical disc substrate 3 according to a third embodiment of the present invention will be described. FIG. 5 shows a configuration of an optical disc substrate 3 according to the third embodiment, in which sandwich molding is performed in which a high melting point resin 21 is used as a core material and the periphery of the core material is covered with a skin layer made of a low melting point resin 22. The recording signal portion 6 is formed on one surface of the low melting point resin 22. Since the recording signal portion 6 is formed of a low melting point resin, it can be accurately formed by resin molding even when pits or grooves are finely formed like a DVD.

A method for manufacturing the optical disk substrate 2 will be described with reference to FIG. A stamper 8 is provided on an upper mold 24 constituting an injection compression molding die, and a high melting point resin nozzle 26 for injecting a high melting point transparent thermoplastic resin on the upper mold 24 side and a low melting point thermoplastic resin are injected. And a low-melting-point resin nozzle 27.

The mold temperature is 130 ° C. or less (for example, 110 ° C.).
C.), the space between the upper mold 24 and the lower mold 25 is closed, and a low-melting resin (for example, polycarbonate having a melting point of 200 ° C.) 22 is first injected from a low-melting resin nozzle 27 through a gate 28 into a mold. Subsequently, while injecting the low melting point resin 22, the high melting point resin (for example,
Polycarbonate (melting point 220 ° C.) 21 is injected into a mold. Gate 28 is configured as a disk gate,
The high melting point resin 21 follows the low melting point resin 22 to form the gate 2
It flows concentrically around the center 8 and is filled in the mold while being wrapped in the low melting point resin 22. In sandwich molding,
Utilizing the property that a low-viscosity material flows so as to envelop a high-viscosity material, and under the same temperature conditions, a low melting point resin 22 is used.
5 has a lower viscosity than the high melting point resin 21, and as shown in FIG. 5, the high melting point resin 21 is used as a core material, and the core material is wrapped in a skin layer made of the low melting point resin 22. The low-melting resin 22 comes into contact with the stamper 8 and is applied with pressure in the compression direction, so that the fine irregularities formed on the stamper 8 are transferred to the surface of the low-melting resin 22.

Since the viscosity of the low melting point resin 22 is reduced and the fluidity is increased, the transfer of the fine unevenness of the stamper 8 is accurately performed. In addition, the heat of the high melting point resin 21 serving as the core material delays the development of the solidified layer when the solidified layer comes into contact with the stamper 8, and the contact is made in a state of high fluidity. In general, the higher the temperature in the outer circumferential direction of the disk, the faster the cooling progresses, so that the transferability deteriorates.
As shown in FIG. 5, since the outermost peripheral portion is made of the low-melting resin 22, a decrease in transferability is suppressed.

In the optical disk substrates 1, 2, and 3 of the embodiments described above, the resin substrates are formed of resins having different melting points. The surface on which the recording signal portion 6 is formed can be made of an abundant resin material. In this case, the resin material must be a resin material that is integrated with the resin material of the resin substrate body.

[0034]

As described above, according to the present invention, the surface layer portion of the resin substrate constituting the optical disk substrate on which the recording signal portion is formed is formed of a resin having different physical properties from the resin forming the resin substrate main body, particularly the melting point. Is formed of a different resin, the viscosity when melted is low, and the fluidity is improved.
Even in the case of an optical disk having a high recording density as described above, a fine recording signal portion can be accurately transferred.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a configuration of an optical disc substrate according to a first embodiment.

FIG. 2 is a configuration diagram showing a method for manufacturing the optical disc substrate according to the first embodiment.

FIG. 3 is a schematic diagram illustrating a configuration of an optical disc substrate according to a second embodiment.

FIG. 4 is a configuration diagram illustrating a method for manufacturing an optical disk substrate according to a second embodiment.

FIG. 5 is a schematic diagram illustrating a configuration of an optical disc substrate according to a third embodiment.

FIG. 6 is a configuration diagram illustrating a method for manufacturing an optical disc substrate according to a third embodiment.

FIG. 7 is a schematic diagram showing a configuration of an optical disk substrate according to a conventional technique.

FIG. 8 is a configuration diagram showing a method for manufacturing an optical disk substrate according to the related art.

[Explanation of symbols]

 1, 2, 3 Optical disk substrate 4 Resin substrate main body 6 Recording signal part 7 Resin film 8 Stamper 9, 14, 24 Upper die 10, 15, 25 Lower die 13 Recording signal layer 16 Nozzle 17 Upper nozzle 19 Lower nozzle 26 High melting point resin Nozzle 27 Low melting point resin nozzle

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Shinji Sakuriku 1006 Kazuma Kadoma, Kadoma-shi, Osaka Matsushita Electric Industrial Co., Ltd. F-term (reference) 5D029 KB07 KC11 5D121 AA02 DD05 EE27

Claims (6)

[Claims] 1. An optical disk substrate having a recording signal portion formed on a surface of a resin substrate, wherein a surface layer of the resin substrate forming the recording signal portion is formed of a resin having different physical properties from a resin constituting a resin substrate body. An optical disk substrate characterized by being formed. 2. The optical disc substrate according to claim 1, wherein the surface layer of the resin substrate forming the recording signal portion is formed of a resin having a melting point lower than the melting point of the resin forming the resin substrate body. 3. The optical disk substrate according to claim 1, wherein the surface layer of the resin substrate forming the recording signal portion is formed of a resin having a different material from the resin forming the resin substrate main body. 4. A method for manufacturing an optical disk substrate, wherein a recording signal portion is formed on a surface of a resin substrate by a stamper disposed in a resin molding die, and the optical disk substrate is resin-molded. A resin film having a melting point higher than the melting point of the resin film is injected into a mold to form a resin substrate main body, and the resin film is fused to the surface of the resin film. A method for manufacturing an optical disk substrate, wherein the recording signal portion is formed. 5. A method for manufacturing an optical disk substrate, wherein a recording signal portion is formed on a surface of a resin substrate by a stamper disposed in a resin molding die, and the optical disk substrate is resin-molded. A low melting point resin is injected into the mold, and a resin forming a resin substrate main body is injected into a mold from a side facing the stamper, and the recording signal portion is formed on the low melting point resin by the stamper to form an optical disc substrate. A method for manufacturing an optical disk substrate, comprising: 6. A method for manufacturing an optical disk substrate, wherein a recording signal portion is formed on a surface of a resin substrate by a stamper disposed in the resin molding die, and the optical disk substrate is resin-molded. By injecting a low-melting resin from the gate and then injecting a high-melting resin, a resin substrate is formed by sandwich molding in which the high-melting resin is covered with the low-melting resin, and the recording is performed on the low-melting resin by the stamper. A method for manufacturing an optical disk substrate, comprising forming a signal portion to form an optical disk substrate.