JPH02183441A - Optical disk - Google Patents

Abstract

PURPOSE:To eliminate the defective adhesion and corrosion generation of reflecting films to suppress the reflection in regions where there are no reflecting films by successively laminating the reflecting films consisting of metallic film patterns, a prescribed oxide film and a protective film on a transparent substrate. CONSTITUTION:The reflecting films 3 consisting of the metallic film patterns formed by forming a metallic film consisting of Al, etc., by an electron beam vapor deposition, etc., providing resist patterns on the film and etching the film are provided on the transparent disk-shaped substrate 1 to constitute the optical disk. The oxide film 5 formed by vapor-depositing Ti or Mg by a reactive vapor deposition method in gaseous oxygen and converting the same to titanium oxide or magnesium oxide is provided on the substrate 1 including the films 3. The protective film 6 consisting of silicon oxide, etc., is further provided on the film 5 by a sputtering method, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application 1] The present invention relates to an optical disc used in a CD-ROM or the like.

[Prior Art] In recent years, optical discs in which digital information for computers is recorded on compact discs, so-called CD-ROMs, have become popular, and are being actively used for searching for literature information. Basically, it has the same structure as a compact disc.

FIG. 2 is a radial cross-sectional view of a conventional optical disc. As shown in FIG. 2, a concavo-convex pattern corresponding to encoded recorded information is formed on the surface of a transparent substrate 1 made of thermoplastic resin such as polycarbonate. On the surface, an anti-eA film 2 made of a metal with high reflectivity such as Aβ is formed by vapor deposition or the like.
and a protective film 4 are sequentially laminated.

Here, the formation of the transparent substrate 1 having the above-mentioned uneven pattern is usually performed using an injection molding method.

This injection molding method is, for example, co-authored by Fujio Mari and Kenji Hayashi.
As disclosed in "Introduction to D Player", page 25 (Corona Publishing, 1983), softened polycarbonate resin is injected into a mother stamper formed through a mastering process, and after the polycarbonate resin is hardened, In this method, the mother stamper is peeled off and the uneven pattern of the mother stamper is transferred onto the injected polycarbonate resin to form a substrate having an uneven pattern.

[Problem to be solved by the invention 1 However, in the above-mentioned conventional optical disc,
There were problems as described below. That is, the uneven pattern formed on the substrate surface usually has a width of about 0.47#II,
It is an extremely fine uneven pattern with a length of 0.9 to 3.3 tm, and therefore, when transferring the uneven pattern from the mother stamper to the transparent substrate 1 made of polycarbonate resin using the index molding method, the uneven pattern may be chipped. , protrusions, cracks, etc. may occur, which has been a major problem in the manufacturing process of optical discs. In particular, CD-ROMs are required to be far more reliable than conventional compact discs, so the current challenge is how to solve the above-mentioned problems. be.

Furthermore, as already mentioned, in the conventional optical disc, the reflective film 2 is formed on the entire surface of the transparent substrate 1 having a concavo-convex pattern. By the way, according to the studies of the present inventors, most of the poor adhesion between the reflective film 2 formed on the uneven pattern and the transparent substrate 1 (lifting of the reflective film 2 from the transparent substrate 1) is caused by the uneven pattern. It has become clear that this phenomenon occurs at the boundary between concavities and convexities. Furthermore, as a result of evaluating the locations where corrosion occurred on the reflective film 2 when a conventionally structured CD-ROM was left for a long time, it was found that much corrosion of the reflective layer 2A2 occurred mainly at the boundaries between the concave and convex portions of the concavo-convex pattern. became clear.

Such poor adhesion or corrosion of the reflective film 2 naturally seriously impairs the reliability of the optical disc, and is similar to the aforementioned problems such as protrusions and cracks during injection molding.
This has become a big problem.

Improving the problem of poor adhesion and corrosion of the reflective film is also an extremely important problem for CD-ROMs, which require higher reliability. The causes of poor adhesion and corrosion of the reflective film are still largely unknown, but one reason for the poor adhesion is thought to be that the reflective film is subjected to a large force due to stress concentration at the boundary between the concave and convex portions. It will be done. Regarding corrosion of the reflective film, the film quality of the reflective film deteriorates at the boundary between concave and convex parts, and as in the case of poor adhesion, so-called stress corrosion occurs due to stress concentration, which accelerates corrosion. This is thought to be the cause. .

The present invention has been made in order to solve the conventional problems as described above, and has high reliability without adhesion failure 9 or corrosion in the reflective film, and is suitable for use with other than patterned reflective films. It is an object of the present invention to provide an optical disc with a high S/N ratio by suppressing unnecessary reflection in the area.

[Means for Solving the Problems] The present invention provides a reflective film made of a metal film pattern corresponding to predetermined digital information, and an oxide made of at least one of magnesium oxide or titanium oxide, on a transparent disc-shaped substrate. The optical disc is characterized in that a film and a protective film are sequentially laminated.

In the present invention, a metal film pattern corresponding to predetermined digital information is formed by forming a reflective film made of a metal film on a disc-shaped transparent substrate and then selectively etching this reflective film. be able to.

[Operation 1] In the present invention, a metal film pattern corresponding to predetermined digital information is formed on a disk-shaped transparent substrate having a flat surface. Therefore, the problems of poor adhesion and corrosion of the reflective film at the boundaries between the concave and convex portions of the concavo-convex pattern, which have been problems with conventional optical discs, do not occur.

Also, according to the studies of the present inventors, magnesium oxide or ditanium oxide thin films (all film thicknesses are 0.5 to 1.5 mm thick).
0tIIri) had an extremely small reflectance of 10 to 20% for laser light in the normal wavelength range of laser light used for reproduction in optical disk devices, for example, laser light with a wavelength of 780 nm. Therefore, by providing an oxide film made of either or both of these oxides on the surface of the transparent substrate containing the patterned reflective film described above, unnecessary unnecessary noise can be removed in areas where the reflective film does not exist. It becomes possible to suppress reflections, and an optical disc with a high S/N ratio is realized.

[Example] Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 1 is a radial cross-sectional view of an optical disk according to an embodiment of the present invention. The method for manufacturing the optical disc shown in FIG.
0.15tJ of membrane! A film is formed to a thickness of n. Af! The electron beam evaporation method was used to form the film, and the evaporation conditions were an ultimate vacuum of 3 x 10-7 Torr, an emission current of 85 mA, and a substrate temperature of 70°C during the evaporation. Next, a photoresist film having a pattern corresponding to the digital information is formed on the film in step 8 above, and the reflective film 3 is removed by ion etching using the photoresist film as a mask. Thereafter, the photoresist film is removed by solvent or oxygen ashing.

Li or M is then deposited by reactive vapor deposition in oxygen gas.
An oxide film 5 made of either titanium oxide or magnesium oxide is formed over the entire surface of the transparent substrate 1 including the fouling film 3 by evaporating CI. The conditions for forming the oxide film were an ultimate vacuum of 3 x 10-7 Torr, an oxygen gas pressure of 1 x 10-5 Torr during vapor deposition, a platinum port in the crucible, and a current of 2 A.
It is. Further, the substrate temperature during vapor deposition was 70'C, and the film thickness of the oxide film 5 was 0.5 to 1.0 degrees centigrade.

At that time, a protective film 6 made of a silicon oxide film is formed on the oxide film 5. A sputtering method is used to form the protective film 6, and the film forming conditions are Ar gas pressure of 5 x 10-3 Torr.
, the thickness of the film formed was 2 μm with an input power of 400 W.

In the optical disc obtained as described above, there is no need to form a fine concavo-convex pattern on the transparent substrate 1 by injection molding, so that chips, protrusions, etc. The problem of the occurrence of dust particles has been solved, and the yield rate in the optical disk manufacturing process has been significantly improved. In addition, since the patterned reflective film is formed and covered over a flat substrate surface, poor adhesion and corrosion of the reflective film at the boundaries between the concave and convex parts of the concave-convex pattern, which were problems with conventional optical discs, occur. I couldn't see either.

Furthermore, when the S/N of the optical disc according to this embodiment was measured, it was found that the S/N of the optical disc of the conventional structure was about 1.
The S/N ratio is 6 times higher, and is about 1.3 times higher than that of an optical disk having the same structure as this example except that the oxide film 5 made of titanium oxide or magnesium oxide was not formed. S/N is shown.

As described above, it was confirmed that the optical disc according to the present invention has higher reliability than conventional optical discs and has excellent characteristics as a CD-ROM for recording digital information for a computer.

At the same time, it also has a higher S/N than an optical disk with a conventional structure or a case where the oxide film 5 is not formed.
It was confirmed that it has.

Incidentally, in the above embodiment, an Al film was used as the material for the reflective film 3, but other high reflectance materials such as AU, Act, T
a, TiN, ZrN, etc. may also be used. Further, in the embodiments, only examples in which magnesium oxide or titanium oxide were formed alone as the oxide film 5 were described, but a mixture or a stack of these may be used as the oxide film 5. .

[Effects of the invention] Since digital information is recorded by patterning the film by etching, problems such as chipping of uneven patterns, protrusions, and cracks that often occurred during conventional index molding are solved, and the optical disk manufacturing process is improved. The yield is significantly improved.

In addition, since there is no need to form a reflective film on the uneven pattern previously formed on the substrate, poor adhesion and corrosion of the reflective film that conventionally occur at the boundaries between the concave and convex parts of the uneven pattern can be suppressed. This makes it possible to realize a highly reliable optical disc.

Furthermore, by forming an oxide film with an extremely low reflectance for laser light in the wavelength range used for reproduction of optical disk devices on the surface of the transparent substrate containing the reflective film, the patterned It becomes possible to suppress unnecessary fouling in areas where the anti-tJr1 film does not exist, resulting in high S
/N is realized.

[Brief explanation of the drawing]

FIG. 1 is a radial sectional view of an optical disc according to an embodiment of the present invention, and FIG. 2 is a radial sectional view of a conventional optical disc. 1... Transparent substrate 2.3... Reflective film 4.6... Protective film 5... Oxide film

Claims (1)

[Claims] (1) A reflective film made of a metal film pattern corresponding to predetermined digital information, an oxide film made of at least one of magnesium oxide or titanium oxide, and a protective film are sequentially laminated on a transparent disc-shaped substrate. An optical disc characterized by: