WO2005031724A1

WO2005031724A1 - Worm type optical disk

Info

Publication number: WO2005031724A1
Application number: PCT/JP2004/013923
Authority: WO
Inventors: Yoshihisa Suzuki; Hitoshi Noguchi; Masahiro Higuchi; Yoshiaki Maeno; Satoshi Sumi; Morio Nakatani
Original assignee: Sanyo Electric Co., Ltd.; Sanyo Mavic Media Co., Ltd
Priority date: 2003-09-26
Filing date: 2004-09-24
Publication date: 2005-04-07
Also published as: JPWO2005031724A1; KR20060089745A

Abstract

An environment-friendly WORM type optical disk not using organic materials. The disk comprises a light transmitting substrate (11) made of biodegradable resin, an absorption buffer layer (13) provided on this substrate (11), and a recording layer (12) provided on the absorption buffer layer (13), wherein the substrate (11) in an area irradiated with light is deformed or deteriorated to form a recording part (55).

Description

Specification

Write-once optical disc

Technical field

The present invention relates to a write-once optical disc, and more particularly, to a write-once optical disc having a low environmental load.

Background art

[0002] Not only information for computers but also information such as audio, still images, and moving images has been digitalized, and the information handled has become enormous. Write-once optical discs such as CD_R (Compact Disc-recordable) and DVD_R (Digital Versatile Disc-recordable) having a larger capacity than CD-R are frequently used to record and store powerful information.

[0003] Conventional write-once optical disks include, for example, a light absorbing layer made of a cyanine dye, an azo dye, a phthalocyanine dye, and a protective layer provided on a substrate made of a polycarbonate resin (PC). A shape-deformable optical disk used as a recording mark by melting and mixing a substrate adjacent to a light absorbing layer with heat of a laser beam is often used.

[0004] Incidentally, an optical disk has a single-plate type in which an information recording layer is formed on a transparent substrate such as a polycarbonate resin, and two single-plate-type disks in order to increase the recording capacity. There are a bonding type in which a recording layer is provided, and a type in which a dummy substrate is bonded to a substrate having an information recording layer formed on a transparent substrate such as a polycarbonate resin. However, in recent years, there has been an increasing demand for higher density of recording media, and a bonded structure type optical disk is often used, including when a transparent substrate is bonded.

[0005] When bonding optical disks, hot-melt adhesives or UV-curable adhesives are used, and methods for applying these adhesives include spin coating, roll coating, and screen printing. Has been adopted.

[0006] By the way, in the above-mentioned optical disc, when it is no longer necessary, it must be discarded by incineration or landfilling since a polycarbonate resin is used as a substrate, and there is a problem in waste disposal. . It is desirable to take some measures from environmental issues The

[0007] In view of such a problem, an optical disk using a biodegradable resin, which is a substrate that can be decomposed in nature as an optical recording medium substrate, has been proposed. (For example, see Patent Document 1). Patent Document 1: Japanese Patent Application Laid-Open No. 2000-11448

Disclosure of the invention

Problems to be solved by the invention

[0008] However, organic materials such as cyanine dyes are used in the above-mentioned conventional write-once optical disks, and among these dye materials, there are materials for which carcinogenicity, toxicity, etc. are concerned. include. For this reason, there is concern about the impact on the environment when discarded, and measures must be taken against this organic material.

[0009] In addition, when an optical disk using the above-mentioned biodegradable resin is bonded, if a hot-melt adhesive or an ultraviolet-curable adhesive is used as an adhesive as in the past, the substrate can be soil-reduced. Even if an environmentally friendly base material is used, the adhesive will not be reduced to the soil, and there is concern over the impact on the environment, and measures must be taken against this adhesive.

[0010] Therefore, an object of the present invention is to provide an environment-friendly optical disk capable of reducing soil.

Means for solving the problem

[0011] A write-once optical disc according to the present invention includes a light-transmissive substrate made of a biodegradable resin, and a recording layer provided on the substrate. The recording part is formed by deformation or alteration.

[0012] Further, a protective layer made of a biodegradable resin can be provided on the recording layer.

[0013] The recording layer may be made of a material selected from a single layer film or a multilayer film of aluminum or iron, or an alloy thereof.

[0014] Furthermore, it is preferable that an absorption buffer layer is provided on the recording layer and the substrate surface side or on the side of the recording layer opposite to the substrate.

[0015] Further, the write-once optical disc of the present invention is a write-once optical disc in which two substrates each having a recording layer on at least one side are bonded, wherein the base material is a translucent resin material made of a biodegradable resin. The substrate is deformed or irradiated by light irradiation. The recording portion is formed by altering the quality.

Further, a protective layer made of a biodegradable resin can be provided on the recording layer.

[0017] The recording layer may be made of a material selected from a single-layer film or a multi-layer film of aluminum or iron or an alloy thereof.

Further, an absorption buffer layer may be provided on the recording layer and the substrate side or on the side of the recording layer opposite to the substrate.

[0019] Further, the base material can be configured to be bonded by an adhesive layer containing a biodegradable adhesive as a main component.

[0020] The adhesive layer may contain degrading bacteria.

The invention's effect

According to the present invention, a recording portion can be formed by deformation or deterioration of a substrate using a biodegradable resin, so that a write-once optical disc can be constituted without using an organic material or the like. Therefore, an inexpensive disc that can be soil-reduced can be provided.

Brief Description of Drawings

FIG. 1 is a schematic cross-sectional view for explaining the structure of a write-once optical disc according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view for explaining recording according to the first embodiment of the present invention, wherein (a) shows a state where recording light is irradiated, and (b) shows a state after recording.

FIG. 3 is a schematic sectional view for explaining the structure of a write-once optical disc according to a second embodiment of the present invention.

FIG. 4 is a cross-sectional view for explaining recording according to a second embodiment of the present invention, wherein (a) shows a state where recording light is irradiated, and (b) shows a state after recording.

FIG. 5 is a characteristic diagram showing a result obtained by irradiating a write-once optical disc according to a second embodiment of the present invention with a semiconductor laser beam and measuring the recording power and the carrier level.

FIG. 6 is a schematic cross-sectional view for explaining a structure of a write-once optical disc according to a third embodiment of the present invention.

FIG. 7 is a cross-sectional view for explaining recording according to a third embodiment of the present invention, where (a) shows a state where recording light is irradiated, and (b) shows a state after recording. FIG. 8 is a schematic cross-sectional view for explaining the structure of a write-once optical disc according to a fourth embodiment of the present invention.

FIG. 9 is a cross-sectional view for explaining recording according to a fourth embodiment of the present invention, where (a) shows a state where recording light is irradiated, and (b) shows a state after recording.

FIG. 10 is a schematic sectional view for explaining the structure of a write-once optical disc according to a fifth embodiment of the present invention.

FIG. 11 is a schematic cross-sectional view for explaining the structure of a write-once optical disc according to a sixth embodiment of the present invention.

Explanation of symbols

[0023] 1, la, lb, lc, ld, le optical discs

11 Optically transparent substrate

12 Recording layer

13 Absorption buffer layer

14 Protective layer

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic cross-sectional view for explaining the structure of a write-once optical disc according to the first embodiment of the present invention.

[0025] The write-once optical disc 1 according to the first embodiment of the present invention is a CD-R type disc.

, Data can be recorded. The structure is such that a recording layer 12 as a reflection layer is provided on a disk-shaped light-transmitting substrate 11, and a protective layer 14 is provided on the recording layer 12.

As shown in FIG. 1, a tracking pregnolative 70 is formed concentrically or spirally on one side plane of the light transmissive substrate 11. In the present invention, the substrate 11 having such a pregnolave 70 is a so-called integrally formed injection-molded resin substrate made of a biodegradable resin that is a substrate that can be decomposed in nature in consideration of the environment and the like.

[0027] Resins that are degraded in nature are biodegradable resins that are degraded by microorganisms and resins that are degraded by moisture, ultraviolet rays, and the like. As a biodegradable resin having transparency, for example, Typical power is resin made mainly from polylactic acid to be extracted. For example, "Rattati (trade name)" manufactured by Toyota Motor, "Lashia (trade name)" manufactured by Mitsui Chemicals, and "Richia" (trade name) manufactured by Unitichika There is "Terramac (product name)". The CD-R type optical disc 1 has a substrate thickness of 1.2 mm. The wavelength of the laser used for recording and reproduction is 780 nm, and the track pitch is 1. The thickness of the substrate is not limited to 1.2 mm. It is possible to select the optimum thickness depending on the laser wavelength and intensity used. Even if the thickness is about 0.5 to 2 mm, good.

[0028] The recording layer 12 formed of a reflective layer formed on the substrate 11 is also toxic to the human body among materials decomposed in the natural world decomposed by oxygen and water and / or materials existing in the natural world. Do not use substances that require caution during disposal. Here, the term toxic refers to substances that clearly cause carcinogenicity's poisoning to the human body.In addition, pay special attention to substances that set a certain standard value in soil pollution, water quality standards, disposal, etc. It is desirable that this substance is not used as a material. As the recording layer 12, for example, a single layer film or a multilayer film of aluminum or iron or an alloy thereof is used. The thickness of the aluminum thin film is 40 nm, and the thickness of the thin film obtained by adding 1% by weight of titanium to aluminum is 35 nm. When iron is used, the reflectance is low. Therefore, a multilayer film in which a thin film of silicon oxide and a thin film of silicon are further stacked on an iron thin film may be used. For example, the thickness of a thin iron film is 150 nm, that of silicon oxide is 100 nm, and that of silicon is 45 nm. Other materials include relatively harmless minerals such as copper (Cu) alloy with silicon (Si) added, B-to-Ge (bismuth-germanium), Pd-Cu and Co-based, and Ag_Pd-Cu. By doing so, a write-once optical disc that is environmentally friendly can be provided.

The protective layer 14 formed on the recording layer 12 is also made of a biodegradable resin, which is a substrate that can be decomposed in nature as in the case of the substrate 11. The protective layer 14 can be formed, for example, by applying a biodegradable resin by spin coating and then curing the coating film. The thickness of such a protective layer 14 is usually about 0.1 to 100 zm.

As described later, in the present invention, since the light diffraction effect due to the deformation of the substrate is large, aluminum, iron, or an alloy thereof having low reflectance can be used as the recording layer.

[0031] The recording method of such a write-once optical disc will be described in detail below with reference to FIG. I will tell. First, recording light (semiconductor laser beam) is irradiated from the substrate side so as to be focused on a recording layer 12 provided on the substrate 11. Then, the recording layer 12 efficiently absorbs the recording light (semiconductor laser beam), converts it into thermal energy, and gives heat to the substrate 11. The biodegradable resin used as the substrate 11 has a low glass transition point of 100 ° C or less. For example, Mitsui Chemicals'"Lacea (trade name)" has a glass transition point of 60 ° C. For this reason, the substrate 11 in the area 55 irradiated with the recording light is greatly deformed, and a recording mark is formed. As a result, a recording portion can be formed in the recording light irradiation portion.

Next, a second embodiment of the present invention will be described. The second embodiment is configured to more reliably control heat generation and substrate deformation. FIG. 3 is a schematic sectional view illustrating the structure of a write-once optical disc according to a second embodiment of the present invention.

[0033] The write-once optical disc la of the second embodiment is a CD-R type disc and can record data. In the structure, an absorption buffer layer 13 is provided on a disk-shaped light-transmitting substrate 11, a recording layer 12 is provided as a reflection layer of the absorption buffer layer 13, and a protective layer 14 is provided on the recording layer 12. Is provided.

The second embodiment has the same configuration as the first embodiment except that the absorption buffer layer 13 is provided. Therefore, the same configuration is not described here to avoid duplication of description. .

The absorption buffer layer 13 reliably controls the heat applied to the substrate 11, and is made of silicon nitride (SiN), aluminum nitride (A1N), or silicon dioxide (Si〇2). A film having a thickness of about 30 nm is formed on the substrate 11.

[0036] A recording method for such a write-once optical disc will be described in detail below with reference to FIG.

First, the recording light (semiconductor laser beam) is irradiated from the substrate side so as to be focused on an absorption buffer 13 provided on the substrate 11. Then, the absorption buffer layer 13 efficiently absorbs the recording light (semiconductor laser beam), converts it into thermal energy, and gives heat to the substrate 11. Then, the substrate 11 in the area 55 irradiated with the recording light is greatly deformed, and a recording mark is formed. As a result, a recording portion can be formed in the recording light irradiation portion.

FIG. 5 shows that the write-once optical disc la of the second embodiment is irradiated with a semiconductor laser beam. FIG. 9 is a characteristic diagram showing the result of measuring the recording power and the carrier level of the recording medium. At this time

The recording mark length was 2. O z m.

FIG. 5 clearly shows that the carrier level increases with the recording power, and that the signal is recorded on the optical disk using the biodegradable resin.

In the write-once optical disc 1 of the second embodiment, a recording layer 12 is provided as a reflective layer on a disc-shaped light-transmitting substrate 11, and an absorption buffer layer 13 is formed on the recording layer 12. In the structure in which the protective layer 14 is provided on the absorption buffer layer 13, heat can be efficiently applied to the substrate 11.

Note that, in the above-described embodiment, recording by deformation of the substrate 11 has been described. However, a signal may be recorded by changing the phase of the substrate material. That is, a phase (amorphous / crystalline) different from the phase (crystalline / amorphous) of the substrate is formed by the recording light (semiconductor laser beam). When injecting and forming a substrate using biodegradable resin, the substrate temperature is rapidly cooled to form the substrate. Therefore, the phase of the substrate is in an amorphous state. Since the biodegradable resin has a low melting point, the substrate can be partially crystallized by recording with a recording technique equivalent to the technique used for CD-RW. Since the crystal and the non-crystal have different optical characteristics, reproduction can be performed by signal detection using a sum signal or the like.

Next, a third embodiment of the present invention will be described. In the third embodiment, a write-once optical disc is constituted by a DVD-R disc. FIG. 6 is a schematic sectional view illustrating the structure of a DVD-R type write-once optical disc lb according to a third embodiment of the present invention.

In the write-once optical disc lb according to the third embodiment, similarly to the first and second embodiments, a recording layer 12 as a reflection layer is provided on a disc-shaped light transmitting substrate 11, On this recording layer 12, a protective layer 14 is provided.

As shown in FIG. 1, a tracking pregnolative 70 is formed concentrically or spirally on one flat surface of the light-transmitting substrate 11. In the present invention, the substrate 11 having such a pregnolave 70 is a so-called integrally formed injection-molded resin substrate made of a biodegradable resin that is a substrate that can be decomposed in nature in consideration of the environment and the like. The resin substrate 20 is bonded to the protective layer 14 by the adhesive layer 44. Although not shown, a printed layer is provided on the resin substrate 20. This substrate 20 is also a so-called integrally formed injection-molded resin substrate made of a biodegradable resin that is a substrate that can be decomposed in nature in consideration of the environment and the like.

The write-once optical disc lb is, for example, a single-sided recording type DVD disc in which a substrate 11 having a thickness of about 0.6 mm and a substrate 20 having a thickness of about 0.6 mm are bonded together. Indicates a dummy substrate that does not affect recording and reproduction. Although the thickness of the substrate is about 0.6 mm, the thickness of the substrates 11 and 20 slightly differs depending on the refractive index of the resin used. That is, the thickness of the substrate varies depending on the refractive index of the resin used. This is because the thickness of the substrate when using polycarbonate as the resin is 0.6 mm, and compatibility is ensured by making it equal to the product of the refractive index (1.58) of this polycarbonate and the thickness of the substrate. Because it is. In the present embodiment using a biodegradable resin, the thickness of the substrate is preferably about 2% thicker than 0.6 mm because it is smaller than the refractive index of polycarbonate. Further, the DVD-R type optical disk in the present embodiment has a thickness of 1.2 mm for the bonded substrate. The wavelength of the laser used for recording and reproduction is 650 nm, and the track pitch is 0.74 / im. Note that the thickness of the substrate is not limited to the one described, but it is possible to select an optimum thickness depending on the laser wavelength, intensity, etc. used, and to have a structure in which the dummy substrate 20 is bonded. I just need. The substrate 20 is made of a biodegradable material like the substrate 11, and is formed by injection molding.

[0047] The substrate 11, the recording layer 12, and the protective layer 14 are made of the same material or the like as in the first embodiment. The description of the same configuration is omitted here to avoid duplication of the description.

[0048] The recording method of such a write-once optical disc will be described in detail below with reference to FIG. First, recording light (semiconductor laser beam) is irradiated from the substrate side so as to be focused on a recording layer 12 provided on the substrate 11. Then, the recording layer 12 efficiently absorbs the recording light (semiconductor laser beam), converts it into thermal energy, and gives heat to the substrate 11. The biodegradable resin used as the substrate 11 has a low glass transition point of 100 ° C or less. For example, Mitsui Chemicals'"Lacea (trade name)" has a glass transition point of 60 ° C. Therefore, the recording light The substrate 11 in the area 55 irradiated with is greatly deformed, and a recording mark is formed. As a result, a recording portion can be formed in the recording light irradiation portion.

[0049] In the above-mentioned bonded optical disk, the adhesive layer 44 may be made of a hot-melt adhesive or an ultraviolet-curable adhesive. When a gentle substrate is used, it is preferable to use an adhesive capable of reducing the soil. Therefore, a biodegradable adhesive is preferably used for the adhesive layer 44. As the biodegradable adhesive, an adhesive such as glue, gelatin, starch, or the like, or a lactic acid-based resin can be used. For example, when glue is used, a glue solution may be formed and applied on the protective film 14 by spin coating or the like, and then the protective layer 14 and the substrate 20 may be adhered to each other.

[0050] By configuring as described above, all the materials can be returned to the soil, the environmental load is reduced, and a simple disposal means can be provided.

When the degrading bacteria are contained in the adhesive layer 44 made of the above-mentioned biodegradable adhesive, soil reduction at the time of disposal is further promoted. As the degrading bacteria, for example, lactic acid bacteria and yeasts may be used.

Next, a fourth embodiment of the present invention will be described. The fourth embodiment is configured to more reliably control heat generation and substrate deformation. FIG. 8 is a schematic cross-sectional view for explaining the structure of a write-once optical disc lc according to a fourth embodiment of the present invention.

The write-once optical disc lc of the fourth embodiment is a single-sided recording type DVD-R type disc similarly to the third embodiment, and has an absorption buffer on a disc-shaped light-transmitting substrate 11. A layer 13 is provided, a recording layer 12 is provided as a reflection layer of the absorption buffer layer 13, and a protective layer 14 is provided on the recording layer 12. The resin substrate 20 is bonded to the protective layer 14 by the adhesive layer 44.

The fourth embodiment has the same configuration as that of the third embodiment except that the absorption buffer layer 13 is provided. Therefore, the description of the same configuration is omitted here to avoid duplication of description. .

[0055] The absorption buffer layer 13 reliably controls the heat applied to the substrate 11, and is made of silicon nitride (SiN), aluminum nitride (A1N), or silicon dioxide (Si 、 2). A film having a thickness of about 30 nm is formed on the substrate 11. [0056] A recording method for such a write-once optical disc will be described in detail below with reference to FIG. First, recording light (semiconductor laser beam) is irradiated from the substrate side so as to be focused on an absorption buffer 13 provided on the substrate 11. Then, the absorption buffer layer 13 efficiently absorbs the recording light (semiconductor laser beam), converts it into heat energy, and gives heat to the substrate 11. Then, the substrate 11 in the area 55 irradiated with the recording light is greatly deformed, and a recording mark is formed. As a result, a recording portion can be formed in the recording light irradiation portion.

In the bonding type optical disc of the fourth embodiment described above, a hot-melt adhesive or an ultraviolet-curable adhesive can be used as the adhesive layer 44, but the substrate can be reduced in soil. When an environment-friendly base material is used, it is preferable to use an adhesive capable of reducing the soil. Therefore, a biodegradable adhesive may be used as the adhesive layer 44. As the biodegradable adhesive, a lactic acid-based resin can be used in addition to an adhesive such as glue, gelatin, and starch. For example, in the case of using glue, a glue solution may be formed, applied on the protective film 14 by spin coating or the like, and then the protective layer 14 and the substrate 20 may be bonded to face each other.

Next, a fifth embodiment of the present invention will be described. The fifth embodiment has a configuration applied to a double-sided recording type DVD-R type. FIG. 10 is a schematic sectional view for explaining the structure of a write-once optical disc according to a fifth embodiment of the present invention.

The write-once optical disk Id according to the fifth embodiment is a double-sided recording type DVD-R type disk. The optical disk has a main surface on which pits or gnoles representing information are formed by fine irregularities. Outer periphery of a pair of light-transmitting substrates 11 and 11 having recording areas formed thereon, recording layers 12 and 12 formed on the recording areas of the pair of light-transmitting substrates 11 and 11, and a pair of light-transmitting substrates 11 and 11. And a protective film formed so as to cover the recording layer, the inner peripheral portion and the recording layer. Then, a pair of discs having the recording layers 12 and 12 and the protective films 14 and 14 formed on the translucent substrates 11 and 11 are bonded to each other with the protective films 14 and 14 facing each other. It is composed of

The substrate 11, the recording layer 12, and the protective layer 14 are made of the same material and the like as in the first embodiment. The description of the same configuration is omitted here to avoid duplication of the description. [0061] A recording method for such a write-once optical disc will be described in detail below with reference to FIG. First, recording light (semiconductor laser beam) is irradiated from the substrate side so as to converge on recording layers 12 and 12 provided on substrates 11 and 11, respectively. Then, the recording layers 12 and 12 efficiently absorb the recording light (semiconductor laser beam), convert the recording light into thermal energy, and apply heat to the substrates 11 and 11. The biodegradable resin used as the substrates 11 and 11 has a low glass transition point force S100 ° C or less. For example, Mitsui Chemical's “Lacea (trade name)” has a glass transition point of 60 ° C. Therefore, the substrate 11 in the area 55 irradiated with the recording light is greatly deformed, and a recording mark is formed. As a result, a recording portion can be formed in the recording light irradiation portion.

[0062] Also, in the bonding type optical disk that is strong in the fifth embodiment described above, a hot-melt adhesive or an ultraviolet-curable adhesive can be used as the adhesive layer 44, but the substrate is not used. When an environment-friendly substrate that can be soil-reduced is used, it is preferable to use an adhesive that can be soil-reduced. Therefore, a biodegradable adhesive is preferably used for the adhesive layer 44. As the biodegradable adhesive, lactic acid-based resins can be used in addition to adhesives such as glue, gelatin, and starch. For example, in the case of using glue, after forming a glue solution and applying the solution on the protective film 14 by spin coating or the like, the protective layers 14 may be bonded to each other so as to face each other.

[0063] By configuring as described above, all the materials can be returned to the soil, and it is possible to provide a simple disposal means with a low environmental load.

When the adhesive layer 44 made of the above-mentioned biodegradable adhesive contains degrading bacteria, the reduction of soil at the time of disposal is further promoted. As the degrading bacteria, for example, lactic acid bacteria and yeasts may be used.

[0065] When the biodegradable adhesive material contains the degrading bacteria as they are, there is a possibility that the adhesive layer 44 and the like are decomposed due to a change over time. Therefore, FIG. 11 shows an optical disc le with improved durability. FIG. 11 is a schematic sectional view showing an optical disk le according to the sixth embodiment of the present invention. The same components as those in FIG. 6 are denoted by the same reference numerals, and description thereof is omitted here to avoid duplication of description.

The optical disc le shown in FIG. 11 is different from the optical disc le of the third embodiment shown in FIG.

44 is mainly composed of biodegradable adhesive, and degraded bacteria are contained in the biodegradable adhesive layer. The microcapsules 41 enclosed in the section are mixed. For this reason, unless the microcapsule 41 is destroyed, the degradation by the degrading bacteria is not performed, and the durability is improved. When the optical disc is discarded, the capsule wall of the microcapsule 41 is broken by bending or otherwise breaking the optical disc, thereby promoting soil reduction.

The microcapsules 41 to be mixed may be formed by, for example, coating lactic acid bacteria with gelatin.

In the embodiment shown in FIG. 11, a single recording area is provided on one side. The present invention can be applied to the fourth and fifth embodiments, and is not limited to this. The present invention is also applicable to those having a plurality of recording layers, such as those having the following.

[0069] Furthermore, in the case of a bonded type optical disc, in which all the materials can be returned to the soil, if applied to a read-only DVD disc other than the write-once optical disc, it is possible to provide a simple disposal means with less environmental load. It becomes. As an optical disk having a powerful structure, the recording layers of the above-described fourth to fifth embodiments may have a structure of a recording layer exclusively for reproduction.

[0070] Also, in the write-once disk Id of Fig. 10 shown as the fifth embodiment, a case in which DVD-R structures are bonded together has been shown. However, the structure of the CD-R shown in the first and second embodiments may not be limited to the DVD-R, and one of them may be the first or second embodiment. The DVD-R, which is a part other than the dummy substrate shown in the third and fourth embodiments, may be bonded with the CD-R as in the embodiment. Furthermore, one may be a CD-R or DVD-R and the one to be attached may be a read-only ROM medium (DVD_R〇M, CD-ROM, etc.). As a result, it is possible to provide an optical disc with low environmental load, in which one side is a reproduction medium and one side is a write-once medium.

It is to be noted that not only the above-described DVD-R standard optical disk but also a substrate having a substrate thickness of 0.6 mm, which is the HD DV D standard of the next-generation DVD standard, is laminated to a thickness of 1.2 mm, and a laser wavelength of 405 nm The present invention can be applied to a disc having a track pitch of 0.34 zm.

[0072] The present invention also relates to a Blu-ray (Blu-ray is a registered trademark) type medium in which recording and reproduction are performed from the cover layer side by using a cover layer of 0.1 mm on the recording layer. Puriai It is possible to use a recording material of an R type or an R type recording material.

Claims

The scope of the claims

[1] A light-transmissive substrate made of a biodegradable resin, and a recording layer provided on the substrate, and a recording portion is formed by deforming or altering the substrate in an irradiated area by light irradiation. A write-once optical disc characterized by:

[2] The write-once optical disc according to claim 1, wherein a protective layer made of a biodegradable resin is provided on the recording layer.

3. The write-once optical disc according to claim 1, wherein the recording layer is made of a material selected from a single layer film or a multilayer film of aluminum or iron or an alloy thereof.

4. The write-once optical disc according to claim 1, wherein an absorption buffer layer is provided on the recording layer and on the substrate side or on the side of the recording layer opposite to the substrate.

[5] In a write-once optical disc in which two substrates each having a recording layer on at least one side are bonded, the substrate is made of a translucent resin material made of a biodegradable resin. A write-once optical disc, characterized in that a recording section is formed by deforming or altering the substrate in a designated area.

6. The write-once optical disc according to claim 5, wherein a protective layer made of a biodegradable resin is provided on the recording layer.

7. The write-once optical disc according to claim 5, wherein the recording layer is made of a material selected from a single layer film or a multilayer film of aluminum or iron or an alloy thereof.

[8] The write-once optical disc according to any one of claims 5 to 7, wherein an absorption buffer layer is provided on the side of the recording layer and the substrate or on the side of the recording layer opposite to the substrate.

9. The write-once optical disc according to claim 5, wherein the base material is bonded with an adhesive layer containing a biodegradable adhesive as a main component.

10. The write-once optical disc according to claim 9, wherein the adhesive layer contains degrading bacteria.