JPS63217546A - Production of optical disk - Google Patents

Abstract

PURPOSE:To improve adhesiveness to a transparent substrate so that the exfoliation and crack during use are decreased and reliability is improved by subjecting the substrate to a sputter etching treatment by an inert gas, then forming an underlying layer thereon. CONSTITUTION:The transparent glass substrate 1 of an optical disk is mounted to a rotary electrode part 5 of a sputtering device. An SiO2 target 6 for the underlying layer and a TbFeCo target 7 for a magneto-optical recording medium are mounted to a stationary electrode 8. The sputter etching is then executed by rotating the electrode 5, evacuating the inside of a vessel, introducing gaseous Ar therein and setting a bias power supply 9 at prescribed conditions. The conditions are changed over after this treatment and the SiO2 target 6 is sputtered to form the underlying layer; thereafter, a recording layer and a protective are formed thereon. The adhesiveness of the substrate 1 and the respective layers thereon is improved and the exfoliation and crack are prevented by executing the sputter etching in such a manner.

Description

[Detailed Description of the Invention] [Summary] As a method for improving the adhesion of an underlayer constituting an optical disk to a transparent substrate and eliminating defects such as peeling and clutter, a sputter etching treatment using an inert gas is applied to a transparent substrate. After that, a base layer, a recording layer, and a protective layer are formed to form an optical disc.

[Industrial application field]

The present invention relates to a method of manufacturing an optical disc with improved adhesion.

Ru.

Optical disks are memories that use laser light to record high-density information, and have excellent features such as large storage capacity, non-contact recording and playback, and being unaffected by dust. .

Here, optical disks include write-once memories that use low-melting point metals as recording media and record information with or without holes (pits).
In addition to this, it is also possible to utilize the difference in reflectance when a phase change occurs between crystals and crystals or between crystals and amorphous, or to form the recording layer from a ferrimagnetic material and apply a bias magnetic field. A rewritable memory (brasable memory) that records information by irradiating it with a laser beam and reversing magnetization as the coercive force decreases as the temperature rises at the irradiation position, and reproduces it using the Kerr effect. Memory
) is also available.

In this way, there are various types of optical discs, but
This composition is polymethyl methacrylate (abbreviated as PMMA)
A transparent substrate with a guide '18 (pre-group) is formed by molding a transparent resin such as polycarbonate (abbreviated as PC), or a photopolymer is coated on a disk-shaped glass plate and a photograph is printed on this. Using etching technology (photolithography), a transparent substrate 1 with concentric or spiral guide grooves formed thereon is made, and a base layer 2. Recording layer 3. It is made by sequentially forming the protective layer 4.

Here, the base layer 2 is for preventing moisture from entering through the transparent substrate l and from contaminating the recording layer 3 by impurities and monomers contained in the resin, and the protective layer 4 is for preventing moisture from entering from above. The recording layer 3 is provided to prevent oxidation of the recording layer 3 which occurs when the recording layer 3 comes into contact with air or the atmosphere.

Here, base layer 2. Recording layer 3. The protective layer 4 is made of inorganic material in most cases, and each of these layers is formed on a guide groove made of synthetic resin, so if they are used together for a long time, they may cause peeling or cracking due to the difference in expansion coefficient. Failures are likely to occur.

[Conventional technology]

The transparent substrate l of the optical disk is made of synthetic resin such as PMMA or PC formed by injection molding, or it is made of a glass substrate coated with photopolymer and then photo-etched to provide guide grooves. The latter type of substrate is often used because of its superior pattern accuracy and fewer defects.

Here, since the glass substrate and the photopolymer layer are bonded together using a silane coupling agent or the like, the adhesion is good and peeling is unlikely to occur between them.

On the other hand, base layer 2. The recording layer 3 and the protective layer 4 are formed continuously using a high frequency sputtering method, an electron beam evaporation method, etc., but since these inorganic layers and the transparent substrate 1 have significantly different expansion coefficients, 7JJ Xi and cranks are likely to occur.

In other words, the materials for forming the underlayer 2 and the protective layer 4 include silicon dioxide (Sin), zinc sulfide (ZnS), and nitride, but in the case of write-once optical discs, tellurium (Te) alone and arsenic/tellurium/germanium ( AsTeGe),
Amorphous mixtures such as arsenic, tellurium, and selenium (AsTeSe) are used.

In addition, for those that use phase change as the recording layer of rewritable optical discs, indium antimony (In
Metals such as Sb) and indium selenium (InSe), and those that use magnetization reversal such as terbium iron cobalt (Tb Fe Co) and gadolinium
Amorphous alloys made of rare earth-transition metals such as cobalt (Gd Co) are used.

In this way, the base layer 2. Recording layer 3. The materials forming the protective layer 4 are different.-1 These layers are 1100n~
Since the transparent substrate is made of a 200 nm thin film, it has good adhesion to each other (on the other hand, since the transparent substrate is made of a resin molded body or resin coating, it cannot be subjected to repeated temperature cycles or left in a high temperature and humid environment for a long time. In this case, phenomena such as peeling and clutter are likely to occur at the interface between the transparent substrate 1 and the underlying layer 2.

Conventionally, no measures have been taken to address this problem, but it is necessary to improve adhesiveness to ensure reliability.

[Problem that the invention seeks to solve]

As described above, optical discs are prone to peeling and cracking between the transparent substrate and the underlying layer, and the problem is how to improve this adhesiveness.

Measures to solve problem C] The above problem involves a base layer on a disk-shaped transparent substrate.

In an optical disc formed by forming a recording layer and a protective layer,
This problem can be solved by an optical disc manufacturing method in which the underlayer is formed after performing sputter etching treatment using an inert gas on the transparent substrate.

[Function] When forming an inorganic layer on an organic layer, a chemical method for improving adhesion is the use of a silane coupling agent as described above, but a physical method is plasma treatment. It has been known.

In this method, prior to film formation by vacuum evaporation, etc., plasma is generated by high-frequency discharge in a reduced pressure inert gas atmosphere, and the ions and electrons of this gas are made to collide with the substrate to activate the surface. , hydroxyl groups (O
11 groups) or carbonyl groups (CO groups), or generate plasma by discharging in an oxygen (or nitrogen) atmosphere and directly introducing polar groups into the glass substrate. A method is being taken.

When a film is formed with polar groups introduced in this way, it is possible to improve adhesion by forming coordination bonds with inorganic materials, metals, etc.

However, this method is not effective when the film formed on the plastic substrate is an oxide or nitride, even if polar groups are present, and therefore this method is not effective for optical discs.

Therefore, the present invention improves adhesion by forming a film after sputter etching in an inert gas atmosphere.

In this case, etching not only roughens the surface of the transparent substrate, but also removes adsorbed water, adsorbed gas, oil and fat, and the like.

In addition, X-ray photoelectron spectroscopy (Electron 5cop
y for Chemical Analysis Abbreviation E
According to observation by SCA), the number of polar groups on the substrate surface has decreased, and carbonization has progressed to some extent.

The present invention improves adhesion by performing conventional film formation after such sputter etching treatment.

〔Example〕

Example 1 (When using a photopolymer-coated substrate) A photopolymer was spin-coded onto a disk-shaped glass substrate with a diameter of 130 mm, which was selectively exposed and developed to form a transparent substrate 1 with concentric guide grooves. , was installed in the rotating electrode section 5 of the sputtering apparatus shown in FIG.

Next, a Si0g target 6 forming the underlayer 2 and a Tb Fe Co target 7 forming the magneto-optical recording medium were placed on the fixed electrode 8.

First, the rotary electrode 5 is rotated and evacuated to bring the degree of vacuum to 5.
After adjusting the voltage to Plasma is generated by applying a 13.5 MHz high frequency electric field between the
Sputter etching was performed for 10 minutes at KW.

Next, after setting the degree of vacuum to 5 Xl0-5Pa, open the slide shutter 10 and introduce Ar to reduce the degree of vacuum to 0.2~5 Pa.
Open the rotary shaft 11 with the pressure set to 0.5 Pa, switch the bias power supply 9 to set the fixed electrode to a low potential, and set the 5i
After applying a high frequency electric field between the J4 target 6 and the transparent substrate 1 and sputtering the SiO□ target 6 to form a film of 1100 nm on the transparent substrate, the rotating shaft 7 11 was opened and the Tb Pa Co target 7 was sputtered. Sputter 11
00n film is formed, then the rotary shutter 11 is opened and Sing is performed.
By forming a film with a thickness of 1100 nm, a magneto-optical disk having the structure shown in FIG. 2 was formed.

A peel test was performed on the magneto-optical disk thus formed and the magneto-optical disk formed without sputter etching the transparent substrate using an adhesive tape (Scotch tape #810 manufactured by 3M).

As a result, the yield rate of the conventional magneto-optical disk, which is formed without any treatment, is about 60%, whereas the yield rate of the magneto-optical disk in which the present invention was implemented was 100%, with no peeling occurring. Ta.

In addition, in a temperature/humidity cycle test at a temperature of 60°C and a relative humidity of 90% and -10°C, the magneto-optical disk according to the present invention showed no peeling even after 500 hours, whereas the untreated one showed no peeling. In all cases, peeling from the inner and outer peripheries of the discs was observed.

Example 2 (when using a PC board): A transparent substrate made of PC molded by injection molding and provided with guide grooves was placed in a sputtering apparatus as shown in Fig. 1, and the same process as in Example 1 was carried out. After performing high frequency sputter etching treatment, a base layer made of SiO□, Tb Fe Co
Magneto-optical disks were prepared by forming a protective layer consisting of 1 and 1 and a protective layer consisting of SiO□ to a thickness of 1100 nm, respectively, and the adhesion was compared with that using an untreated substrate.

As a result, adhesive tape (scotch tape #81 manufactured by 3M Company) was used.
As a result of the peel test according to 0), the yield rate of the disc using the present invention was 100%, while the yield rate of the disc using the untreated substrate was 10%, proving the improvement in adhesion. .

〔Effect of the invention〕

As described above, by implementing the present invention, the adhesion between the transparent substrate of the optical disc and the underlying layer, recording layer, and protective layer formed thereon is improved, and peeling during use is reduced.
Reliability can be improved.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a sputtering apparatus embodying the present invention, and FIG. 2 is a partial sectional view showing the layer structure of an optical disk. In the figure, 1 is a transparent substrate, 2 is a base layer, 3 is a recording layer,
4 is a protective layer.

Claims (1)

[Claims] An optical disc comprising a base layer, a recording layer, and a protective layer formed on a disc-shaped transparent substrate, characterized in that the base layer is formed after the transparent substrate is subjected to sputter etching treatment using an inert gas. A method for manufacturing optical discs.