JP2001067726A - Optical disk - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a stuck optical disc diminished in properties to become mechanical problems after stuck without changing a sticking process by sticking substrates different in thickness after adjusting their thicknesses to a specified range according to stress and strength difference. SOLUTION: When two substrates, at least one substrate of which has an optical spot guiding groove and/or an uneven pattern consisting of address pits and emboss pits for recording information or the like on the surface, are adhered to each other to obtain the optical disk, the thickness of one substrate is made different from that of the other substrate in 5-100 microns thickness. Such a range can be made wider, that a radial tilt can be made smaller in the case that the substrates different in the thickness are used than in the case that the substrates having the same thickness are used. In order to make the substrates comparatively different in the thickness by using the same die, for example, the die is fastened by different pressures after resin is injected at injection molding.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a DVD-Video
o, read-only type such as DVD-ROM, write-once (appendable) type such as DVD-R, or DVD-RAM,
The present invention relates to various rewritable optical disks such as a DVD-RW.

[0002]

2. Description of the Related Art Conventional optical disk duplication methods employ optical head guide grooves and pits or sectors representing addresses and the like on the surface.
Having an uneven pattern such as marks or recorded information,
A stamper was prepared from a master with photoresist by nickel plating. A plastic substrate material (for example, polycarbonate) melted at a constant temperature was poured into a mold on which the stamper was installed, and then solidified and removed. The plastic substrate is completed. A reflective film or a recording film that is changed by laser light irradiation is formed on the substrate directly or through another layer, and a UV-curable resin is spin-coated and cured so that the film is not damaged. Audio, CD-, CD-RO
Optical disks such as M and CD-R are completed. On the other hand, there is an optical disk of a type in which two substrates are bonded. MO, PD, DVD-ROM, DVD-R, DVD
-RAM, DVD-RW, etc. MO, PD, and the like are hardly affected by curing shrinkage of the adhesive because two substrates having a thickness of 1.2 mm are bonded to each other. DVD
The series has a structure in which the thickness of the substrate is as thin as 0.6 mm, which is half, and the two sheets are bonded together to have the same thickness of 1.2 mm as the CD series. There are various types of adhesives for bonding such as a type which is cured by light, heat or moisture in the air.

[0003]

The above-mentioned prior art is a method of bonding two substrates having a thickness of 1.2 mm, and the two substrates have the same stress and strength. 1.2
When a substrate as thin as 0.6 mm is bonded as compared with a substrate having a thickness of 0.6 mm, it is difficult to suppress mechanically problematic characteristics such as warpage. When bonding two substrates having the same warpage, it is relatively easy to balance the mechanical properties of the two substrates via an adhesive. However, if one of the substrates has no film or a film with a small stress is formed, it is difficult to balance the mechanical properties of the two substrates by bonding together in the same manner as described above.

[0004] It is an object of the present invention to produce an optical disk with reduced mechanically problematic characteristics after bonding without changing the conventional bonding process.

[0005]

The above object can be attained by bonding substrates having different thicknesses within a range of 100 microns according to differences in stress and strength in an optical disk in which two substrates are bonded.

Generally, the two substrates have the same thickness. This is because the thickness of the substrate is fixed by the mold that is poured when producing a plastic substrate. Therefore, another mold must be prepared to produce substrates having different thicknesses.

[0007] The adhesive used for bonding the two substrates shrinks when cured. Therefore, it is necessary to perform bonding in consideration of the curing shrinkage. When two substrates having different stresses and strengths are bonded to each other, the weaker substrate is affected by the curing shrinkage of the adhesive, so that the mechanical characteristics balance between the two substrates cannot be maintained.

Therefore, the present invention has the following configuration.

(1) An optical disk in which at least one substrate has two substrates having a light spot guide groove and / or a concavo-convex pattern composed of embossed pits such as address pits and recorded information on the surface of the substrate using an adhesive. 2. The optical disk according to claim 1, wherein the two substrates have different thicknesses within a range of 5 to 100 microns.

(2) The optical disk according to (1), wherein the adhesive is cured by light, heat, moisture in air, or the like.

(3) In the optical disc described in (1), a reflection film or a recording film that changes by irradiation with a laser beam is formed on one substrate directly or via another layer, and the other substrate is formed on the other substrate. An optical disc characterized by not being formed.

(4) In the optical disc described in (1), a reflection film or a recording film that changes by irradiation with laser light is formed on one substrate directly or via another layer, and the other substrate is formed on the other substrate. An optical disc having a translucent reflective film formed thereon.

(5) In the optical disc described in (1), a reflection film or a recording film that changes by irradiation with laser light is formed on one substrate directly or via another layer, and the other substrate is formed on the other substrate. An optical disc characterized by forming a translucent recording film that changes by laser light irradiation.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION A stamper is formed by nickel plating from a master with a photoresist having an optical head guide groove, a pit representing an address, or a concavo-convex pattern such as recorded information on a surface, and a mold in which the stamper is installed. When a plastic substrate material (for example, polycarbonate or the like), which is melted at a constant temperature, is poured into the substrate and solidified, a plastic substrate having a concave and convex pattern replicated on the surface is obtained. On this substrate directly or through another layer,
A reflective film or a recording film that changes with laser light irradiation was formed. First 120nm and ZnS · SiO ₂ film as a lower protective layer on a polycarbonate substrate, C is the interfacial layer
After laminating the r ₂ O ₃ film to a thickness of 5 nm, a Ge—Sb—Te film was laminated to a thickness of 8 nm as a layer for recording information. Further, a Cr ₂ O ₃ layer serving as an interface layer is 5 nm thick, and ZnS · S is used as an upper protective layer.
An iO ₂ film was laminated to a thickness of 135 nm, and a Cr—O film was laminated to a thickness of 30 nm and an Al—Ti film was laminated to a thickness of 80 nm as a reflection layer and a heat diffusion layer.

An optical disk is completed when another substrate on which no film is formed is bonded using an ultraviolet-curable resin as an adhesive. The thickness of the adhesive layer after bonding was about 30 microns.

Table 1 shows the relationship between the thickness of the two substrates and the mechanical characteristics at this time. The mechanical properties are Radial T indicating warpage.
Indicated by ilt. The mechanical characteristics were measured using a DLD3000 device manufactured by Japan EM. The refractive index of the PC board is 1.58. The vertical axis in the table is the substrate on which the film is formed,
The horizontal axis is a transparent substrate without a film.

The evaluation criteria are as follows: ○ is <± 0.5 (de)
g), △ is ± 0.5 to ± 0.7 (deg), × is> ±
0.7 (deg).

[0018]

[Table 1]

As can be seen from the above results, the Radia has a different thickness as compared to the case where the two substrates have the same thickness.
The range in which l Tilt can be reduced has been widened.

In order to produce substrates having different thicknesses as described above, for example, when injecting a resin at the time of injection molding and then tightening a mold,
By making the pressure different, a substrate having a slightly different thickness can be produced with the same mold.

As a process other than the above, a hard coat may be provided in advance on the light incident side of the substrate, or a protective coat may be provided on a recording film or the like formed on the substrate in order to prevent the influence of the adhesive. Although it is necessary, in this case, the optimum conditions are determined by changing the substrate thickness. A similar experiment was conducted by forming a reflective film of Al, Al-Ti or Au on the polycarbonate substrate on the vertical axis with a thickness of 100 nm. Although the optimum conditions are slightly different, it is the same to determine the optimum conditions by changing the thickness of the substrate.

As a combination of two substrates, a polycarbonate substrate on the vertical axis has a reflection film of Al, Al—Ti or Au of 100 nm, and a polycarbonate substrate on the horizontal axis has a SiN film as a translucent reflection layer of 55 nm. A similar experiment was performed for Since the stress of the formed film is different from that of the substrate used in the previous measurement, the optimum conditions are slightly different, but it is the same to determine the optimum conditions by changing the thickness of the substrate.

Separately, a 120 nm ZnS.SiO ₂ film as a lower protective layer and a 5 nm Cr ₂ O ₃ film as an interface layer are laminated on a polycarbonate substrate on the vertical axis, and a Ge—Sb—Te film is recorded as a layer for recording information. 8 nm was laminated. Further, a Cr ₂ O ₃ layer serving as an interface layer is 5 nm thick, and ZnS is used as an upper protective layer.
An SiO ₂ film is laminated to a thickness of 135 nm, a Cr—O film is 30 nm as a reflection layer and a heat diffusion layer, and an Al—Ti film is 80 n.
A similar experiment was performed for a combination of m-layers and a 30-nm SiN film as a translucent reflective layer formed on a polycarbonate substrate on the horizontal axis. As for the combination, it is the same to determine the optimum conditions by changing the thickness of the substrate as described above.

Further, as a combination of two substrates, an Au film as a lower protective layer is 10 nm, a ZnS.SiO ₂ film is 100 nm as a lower protective layer, and a Ge—Sb—Te film is 10 nm as a layer for recording information on the polycarbonate substrate on the vertical axis. 20 nm ZnS.SiO ₂ film as upper protective layer, reflective layer Al-
An 80 nm Cr film was laminated. The polycarbonate substrate of the horizontal axis was 100nm laminated ZnS · SiO ₂ film a Ge-Sb-Te film of ZnS · SiO ₂ film 100nm, information as a layer for recording 8 nm, as the upper protective layer.

In this combination, it is the same to determine the optimum condition by changing the substrate thickness in the same manner as described above.

As still another laminated structure, a ZnS.SiO ₂ film is formed as a lower protective layer on the polycarbonate substrate on the vertical axis at a thickness of 100 nm, and a Ge-Sb-Te layer is formed as a layer for recording information.
A 25 nm thick film, a 20 nm thick ZnS.SiO ₂ film as an upper protective layer, and an Al-C
A similar experiment was performed on a substrate on which an r film was stacked to a thickness of 80 nm.

For this combination, it is the same to determine the optimum conditions by changing the substrate thickness as described above.

Further the ZnS · SiO ₂ film on the polycarbonate substrate of the vertical axis as the lower protective layer as another combination 100 nm, information as a layer for recording Ge-Sb-Te
A 25 nm thick film, a 20 nm thick ZnS.SiO ₂ film as an upper protective layer, and an Al-C
An r film was laminated to a thickness of 80 nm, and a 55 nm SiN film was formed as a transparent dielectric layer on the polycarbonate substrate on the horizontal axis.

In this combination, the optimum condition is determined by changing the substrate thickness in the same manner as described above.

[0030]

According to the present invention, by selecting the thickness of the substrates to be bonded without changing the conventional optical disk manufacturing process, it is possible to stably warp even in a difficult process of bonding two substrates having different stresses and strengths. An optical disk having excellent mechanical properties could be provided.

[Brief description of the drawings]

FIG. 1 is a diagram showing an optical disk according to an embodiment of the present invention.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Keikichi Ando 1-280 Higashi Koigakubo, Kokubunji-shi, Tokyo F-term in Central Research Laboratory, Hitachi, Ltd. 5D029 KB14 RA01 RA08 RA28

Claims (5)

[Claims] 1. An optical disc in which at least one substrate has at least two substrates having an uneven pattern composed of light spot guide grooves and / or embossed pits such as address pits and recorded information on the surface of the substrate using an adhesive. ,
An optical disc characterized in that the two substrates have different thicknesses within a range of 5 to 100 microns. 2. The optical disk according to claim 1, wherein the adhesive is cured by light, heat, moisture in the air, or the like. 3. The optical disk according to claim 1, wherein a reflection film or a recording film which is changed by laser light irradiation is formed on one substrate directly or via another layer, and the other film is formed on the other substrate. An optical disc characterized by not performing. 4. The optical disc according to claim 1, wherein a reflection film or a recording film that changes by irradiation with a laser beam is formed on one substrate directly or via another layer, and the other substrate is translucent. An optical disc characterized by having a reflective film formed thereon. 5. The optical disk according to claim 1, wherein a reflection film or a recording film that changes by irradiation with a laser beam is formed on one of the substrates directly or via another layer, and a laser film is formed on the other substrate. An optical disc characterized by forming a translucent recording film that changes with light irradiation.