JPH04219645A - Optical disk - Google Patents

Abstract

PURPOSE:To provide an optical disk obtainable long term reliability by preventing damage and peeling off of moisture protective diaphragm. CONSTITUTION:This optical disk consist of recording film 3 recording and reproducing information by light formed on a surface of transparent plastic substrate 1 and damage and moisture protective diaphragm 6 formed on opposite face of the above-mentioned recording diaphragm on the above-mentioned transparent plastic substrate and provided with protective diaphragm 7 formed as covering the above-mentioned protective diaphragm. Additionally, diaphragm for protecting damage and moisture absorption is formed as wider area than for utilization of this diaphragm for recording and reproducing and in the area where protective diaphragm is not applied for recording and reproducing, this layer is formed so as to covering boundary of the above-mentioned protective diaphragm.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disc for recording and reproducing information using light.

0002

2. Description of the Related Art FIG. 3 shows, for example,
4 is a sectional view showing a conventional optical disc disclosed in Japanese Patent Application Laid-Open No. 1-292639. In the figure, 1 is a plastic substrate made of polycarbonate, 2 is a Si3N4 enhancement layer, and 3 is a TbFeC
o magnetic layer, and 4 is a Si3 N4 protective layer. 5 is an epoxy resin protective layer, and 6 is, for example, a Si3 N4 dielectric film, which is a film that prevents damage to the substrate 1 and warping due to moisture absorption.

[0003] In general, a transparent plastic substrate 1 is often used as a substrate material for optical discs because it is excellent in mass production. However, in the case of the plastic substrate 1, if it is left in a humid state for a long period of time, it will warp due to hydrolysis of the substrate 1, or if the surrounding environment changes, it will warp due to a temporary moisture absorption process of the substrate. When large warpage occurs, the focus servo of the actuator cannot follow the focus stably, causing malfunctions and errors. There was also the problem that they were easily damaged. Therefore, the prevention film 6 was used to prevent damage and moisture absorption to the substrate 1.

0004

[Problems to be Solved by the Invention] However, in the long term, the surface of the plastic substrate 1 may be hydrolyzed by moisture inside the substrate and deteriorate, or the moisture absorption prevention film 6 itself may deteriorate and peel off easily. There was a problem.

The present invention has been made to solve the above-mentioned problems, and provides a damage and moisture absorption prevention film 6.
The object of the present invention is to provide an optical disc that can obtain long-term reliability by preventing peeling of the disc.

[0006]

[Means for Solving the Problems] An optical disc according to the present invention includes a recording film formed on one surface of a transparent plastic substrate for recording and reproducing information using light, and a recording film formed on the surface of the transparent plastic substrate opposite to the recording film. The device includes a film for preventing damage and moisture absorption of the substrate, and a protective film formed to cover the preventive film.

[0007] An optical disc according to still another aspect of the present invention includes a recording film formed on one surface of a transparent plastic substrate for recording and reproducing information using light; A film that is formed to be wider than an area facing the area used for reproduction and prevents damage and moisture absorption to the substrate, and a protective film that covers the boundary of the preventive film in an area facing the area not used for recording and reproduction. It is something.

[0008]

[Operation] The optical disc of the present invention has the following advantages: by further forming a protective film to cover the damage and moisture absorption prevention film formed on the surface of the substrate opposite to the surface on which the recording film is formed,
A highly reliable optical disc with no damage or peeling of the moisture absorption prevention film even after long-term use can be obtained.

Furthermore, in the optical disk according to another aspect of the present invention, the film for preventing substrate damage and moisture absorption is formed to be wider than the area opposite to the area used for recording and reproduction, and the film is formed to be wider than the area opposite to the area used for recording and reproduction. Since the protective film is provided to cover the boundary of the preventive film in the area where the protective film is removed, it is possible to protect the boundary of the preventive film, which is particularly likely to peel off, with the protective film so as not to affect recording and reproduction.

0010

[Example] Example 1. An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional view showing an optical disk according to an embodiment of the present invention. In the figure, 1 is a transparent plastic substrate, 2 is a Si3N4 enhancement layer, 3 is a TbFeCo magnetic layer, 4 is a Si3N4 protective layer, and 5 is an epoxy The system resin protective layer 6 is, for example, a Si3 N4 dielectric film, and is a damage and moisture absorption prevention film for the substrate 1, and 7 is a protective film formed to cover the damage and moisture absorption prevention film 6.

Next, the manufacturing method will be explained. Si3N is applied to the surface of the transparent plastic substrate 1 on which the guide groove is formed.
4 Enhancement layer 2, TbFeCo magnetic layer 3, Si3
A N4 protective layer 4 was formed in this order by magnetron sputtering, and an epoxy resin protective layer 5 was formed by spin coating to cover these layers. Next, a damage and moisture absorption prevention film 6 made of Si3N4 dielectric material was formed to a thickness of 2100 angstroms in an area wider than the area where the recording film 3 was formed on the opposite side of the substrate surface from the recording film 3.

When the recording and reproducing characteristics of the thus obtained optical disc were examined using a laser beam with a wavelength of 830 nm, it was found that it was almost the same as a disc on which the damage and moisture absorption prevention film 6 made of the Si3N4 dielectric was not formed. Recording and reproducing characteristics were obtained. This is generally the condition that minimizes surface reflectance.

Film thickness t=λ/2n×m

(λ: wavelength, n: refractive index, m: integer)

0
This corresponds to the case where m=1 in the relationship #015.

Next, an ultraviolet curing resin was formed as a protective film 7 by spin coating so as to cover the entire surface of the damage and moisture absorption prevention film 6 made of Si3N4 dielectric, and then cured using an ultraviolet irradiation device.

The protective film 7 is preferably made of polycarbonate having a refractive index similar to that of the polycarbonate used for the substrate 1, but other than ultraviolet curable resins, thermosetting resins such as epoxy resins can also be used.

[0018] This disk was heated at 80°C and 90%RH for 10 minutes.
After 00 hours of use, no damage to the Si3N4 dielectric or peeling of the moisture absorption prevention film 6 was observed, indicating good reliability.

Example 2. Si3 N4 Al2O3 with a refractive index of about 1.6 in place of the dielectric damage and moisture absorption prevention film 6
Example 1 except that a film of 2600 angstroms was used.
A disk prepared in the same manner as above was heated to 80℃ and 90%RH for 1000 minutes.
No peeling was observed in the Al2O3 film 6 during the test, indicating good reliability.

Example 3. Si3 N4 SiO film 2 with a refractive index of about 1.7 in place of the dielectric damage and moisture absorption prevention film 6
When a disk prepared in the same manner as in Example 1 except that a thickness of 500 angstroms was used was placed at 80° C. and 90% RH for 1000 hours, no peeling was observed in the SiO film 6, indicating good reliability.

Example 4. Si3 N4 SiO2 with a refractive index of about 1.5 in place of the dielectric damage and moisture absorption prevention film 6
When a disk prepared in the same manner as in Example 1 except that a film of 2800 angstroms was used was placed at 80° C. and 90% RH for 1000 hours, no peeling was observed in the SiO2 film 6.
It showed good reliability.

Example 5. A disk prepared in the same manner as in Example 1 except that a 2600 angstrom SiON film with a refractive index of about 1.6 was used in place of the dielectric damage and moisture absorption prevention film 6 was placed at 80° C. and 90% RH for 1000 hours. No peeling was observed in the SiON film 6, indicating good reliability.

Example 6. Si3 N4 Ta2O5 with a refractive index of about 2.1 in place of the dielectric damage and moisture absorption prevention film 6
Example 1 except that a film of 2000 angstroms was used.
A disk prepared in the same manner as above was heated to 80℃ and 90%RH for 1000 minutes.
No peeling was observed in the Ta2O5 film over time, indicating good reliability.

Example 7. Si3 N4 AlN film 2 with a refractive index of about 1.8 in place of the dielectric damage and moisture absorption prevention film 6
When a disk made in the same manner as in Example 1 except that 300 angstroms was used was placed at 80° C. and 90% RH for 1000 hours, no peeling was observed in the AlN film 6, indicating good reliability.

Example 8. Si3 N4 AlSiN with a refractive index of about 2.1 in place of the dielectric damage and moisture absorption prevention film 6
When a disk made in the same manner as in Example 1 except that a film of 2000 angstroms was used was placed at 80° C. and 90% RH for 1000 hours, no peeling was observed in the AlSiN film 6.
It showed good reliability.

Example 9. Si3 N4 SiAlO with a refractive index of about 2.0 in place of the dielectric damage and moisture absorption prevention film 6
Example 1 except that an N film of 2100 angstroms was used.
A disk prepared in the same manner as above was heated to 80℃ and 90%RH for 1000 minutes.
No peeling was observed in the SiAlON film 6 over time, indicating good reliability.

Example 10. A disk prepared in the same manner as in Example 1 except that a 1800 angstrom ZnS film with a refractive index of about 2.3 was used instead of the Si3N4 dielectric damage and moisture absorption prevention film 6 was placed at 80° C. and 90% RH for 1000 hours. No peeling was observed in the ZnS film 6, indicating good reliability.

Example 11. Except that a 2100 angstrom ZnS-SiO2 film with a refractive index of about 2.0 was used instead of the Si3N4 dielectric damage and moisture absorption prevention film 6.
When a disk prepared in the same manner as in Example 1 was placed at 80° C. and 90% RH for 1000 hours, no peeling was observed in the ZnS-SiO2 film 6, indicating good reliability.

Example 12. Si3 N4 ZnSe with a refractive index of about 2.0 is used instead of the dielectric damage and moisture absorption prevention film 6.
-A disk made in the same manner as in Example 1 except that a SiO2 film of 2100 angstroms was used was heated at 80°C and 90%RH.
When it was put in for 1000 hours, ZnSe-SiO2
No peeling was observed in the film 6, indicating good reliability.

Example 13. Si3 N4 AlGe with a refractive index of about 2.1 in place of the dielectric damage and moisture absorption prevention film 6
Example 1 except that an N film of 2000 angstroms was used.
A disk prepared in the same manner as above was heated to 80℃ and 90%RH for 1000 minutes.
No peeling was observed in the AlGeN film 6 over time, indicating good reliability.

In the above embodiment, the Si3N4 enhancement layer 2 and the Si3N4 enhancement layer 2 are provided on both sides of the TbFeCo magnetic layer 3.
Although the case where the protective layer 4 is provided has been explained,
It is obvious that the same effects as in the above embodiment can be obtained even in the case of only a magnetic layer.

Example 14. FIG. 2 shows a half cross section of an optical disc according to another embodiment of the invention. In this example, the preventive film 6 is formed wider on the surface of the substrate 1 opposite to the recording film 3 than the area facing the area used for recording/reproduction, and the protective film 7 is formed opposite the area not used for recording/reproduction. It is formed so as to cover the boundary of the preventive film 6 in the area where the protective film 6 is formed. Therefore, it is possible to protect the boundary of the prevention film 6, which is particularly susceptible to peeling, with the protective film 7 so as not to affect recording and reproduction.

Next, the manufacturing method will be explained. First, a Si3N4 enhancement layer 2, a TbFeC
o The magnetic layer 3 and the Si3N4 protective layer 4 are sputtered in this order with a radius of 18 mm to 43 mm by magnetron sputtering.
Films were formed in an area of 1.0 mm, and an epoxy resin protective layer 5 was formed by spin coating to cover these layers. Of these, the area used for recording and reproducing information has a radius of 23 mm ~
It is 40mm. Next, a damage and moisture absorption prevention film 6 made of Si3N4 dielectric material was formed to a thickness of 2100 angstroms in an area with a radius of 18 mm to 43 mm on the substrate surface on the side opposite to the recording film 3.

When the recording and reproducing characteristics of the thus obtained optical disc were examined using a laser beam with a wavelength of 830 nm, it was found that it was almost the same as a disc on which the damage and moisture absorption prevention film 6 made of Si3N4 dielectric was not formed. Recording and reproducing characteristics were obtained. This is generally the condition that minimizes surface reflectance.

Film thickness t=λ/2n×m

(λ: wavelength, n: refractive index, m: integer)

0
This corresponds to the case where m=1 in the relationship:

Next, a radius of 15 m was formed so as to cover the boundary of the damage and moisture absorption prevention film 6 made of Si3N4 dielectric.
A protective film 7 was obtained by gluing a film coated with a pressure-adhesive adhesive, cut out in advance into annular shapes of m to 22 mm and 41 mm to 44 mm.

[0039] This disc was heated at 80°C and 90%RH for 10 minutes.
After 00 hours of use, no damage or peeling of the moisture absorption prevention film 6 made of the Si3N4 dielectric was observed, indicating good reliability.

[0040]

As described above, according to the present invention, there is a recording film formed on one surface of a transparent plastic substrate for recording and reproducing information using light, and a recording film formed on the surface of the transparent plastic substrate opposite to the recording film. Equipped with a film that prevents warping of the substrate and a protective film formed to cover the damage and moisture absorption prevention film, the effect is that long-term reliability can be achieved by preventing the damage and moisture absorption prevention film from peeling off. There is.

According to another aspect of the present invention, there is provided a recording film formed on one surface of the transparent plastic substrate for recording and reproducing information using light; and a recording film formed on one surface of the transparent plastic substrate for recording and reproducing information using light; A film that is formed to be wider than an area facing the area to be used and prevents damage and moisture absorption to the substrate, and a protective film that covers the boundary of the preventive film in an area facing the area not to be used for recording and reproduction. In particular, it becomes possible to protect the boundary of the prevention film, which is easily peeled off, with a protective film so as not to affect recording and reproduction.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an optical disc according to an embodiment of the present invention.

FIG. 2 is a sectional view showing an optical disc according to another embodiment of the invention.

FIG. 3 is a sectional view showing a conventional optical disc.

[Explanation of symbols]

1 Transparent plastic substrate 3 Recording film 6 Damage and moisture absorption prevention film 7 Protective film

Claims (2)

[Claims] 1. A recording film formed on one surface of a transparent plastic substrate for recording and reproducing information using light; a film formed on a surface of the transparent plastic substrate opposite to the recording film for preventing damage and moisture absorption to the substrate; and an optical disc comprising a protective film formed to cover the above-mentioned prevention film. 2. A recording film formed on one surface of a transparent plastic substrate for recording and reproducing information using light, the area being wider than the area facing the area used for recording and reproducing on the surface of the transparent plastic substrate opposite to the recording film. An optical disc comprising a film formed to prevent damage and moisture absorption on the substrate, and a protective film covering the boundary of the preventive film in an area opposite to an area not used for recording and reproduction.