JP3029328B2 - Method of forming optical reflection film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical reflection film for an optical information disk, an optical device, and the like, and a method for forming the same.

[0002]

2. Description of the Related Art In an optical information disk such as an optical video disk, information pits are formed on a surface of a plastic substrate such as an acrylic resin or a polycarbonate resin, and an optical reflection film of aluminum or an aluminum alloy is formed thereon. It is provided. Above all, in the case of optical video discs, it is common to use an acrylic resin, that is, PMMA (polymethyl methacrylate resin) as a material for a substrate from the viewpoint of optical characteristics and cost, and a reflectance as a material for an optical reflection film. It is common to use high-purity aluminum from the viewpoints of durability, cost, and the like.

[0003] A disk using such a PMMA substrate is liable to be warped or the like due to changes in temperature or humidity. Therefore, deformation of the disk is prevented by bonding two disks back to back with an adhesive or the like. I try to suppress it. However, there is a risk that the reflective film will peel off when the adhesive is applied at the time of bonding, and if the disk is repeatedly subjected to the stress caused by changes in temperature and humidity as described above, the reflective film will not peel off. There is a worry that will happen.

Therefore, conventionally, a method of forming a reflective film using a vacuum evaporation method has been generally adopted, with an emphasis on the adhesion of the film to the substrate.

[0005]

However, the conventional vacuum deposition method used for forming an aluminum reflective film on the surface of a PMMA substrate requires equipment cost because a large-sized batch-type apparatus needs to be used. However, there was a problem that control of operating conditions was not easy.

[0006] On the other hand, the sputtering method has the advantages that the apparatus can be made compact because the apparatus can be a continuous apparatus, the operating conditions can be easily controlled, and quality control can be easily performed. However, the film formed by the sputtering method has a fatal defect that the adhesion to the PMMA substrate is poor. Therefore, even if it is disadvantageous in quality control, it is necessary to adopt a vacuum evaporation method in which the adhesion of the film to the substrate is good. Did not.

Accordingly, an object of the present invention is to provide a novel method for forming an aluminum reflective film having good adhesion to a substrate by a sputtering method in which the apparatus is small and quality control is easy.

[0008]

SUMMARY OF THE INVENTION An object of the present invention as described above is to perform a plasma treatment on a surface of a plastics substrate in a mixed gas atmosphere containing a carbon-containing substance and an inert gas to a thickness of 200 μm. This is achieved by a method for forming an optical reflection film, which comprises sputtering an aluminum or aluminum alloy film having a thickness of 400 to 600 ° and then sputtering an aluminum or aluminum alloy film having a thickness of 400 to 600 ° in an inert gas atmosphere. can do.

The plastics substrate used in the present invention is not particularly limited, but when used as an optical reflection film of an optical disk, PMMA or polycarbonate resin (PC) is preferable, and especially when PMMA is used. An extremely excellent effect is exhibited.

The aluminum or aluminum alloy used as the material for the optical reflection film used in the present invention is preferably high-purity aluminum from the viewpoint of reflectance. However, in order to improve corrosion resistance, adhesion and the like. Alternatively, an aluminum alloy can be appropriately selected and used.

The inert gas contained in the atmosphere gas is a gas belonging to Group 0 of the periodic table, and argon is preferably used. However, a mixture of argon and neon, krypton, xenon or the like may be used. Examples of the carbon-containing substance contained in the atmospheric gas include hydrocarbons that are compounds of carbon and hydrogen, carbon oxides that are compounds of carbon and oxygen, and oxygen-containing compounds that are compounds of carbon, hydrogen, and oxygen. Organic compounds and the like, as well as atomic groups such as radicals generated from these compounds are used. However, these must be present in a gaseous state in the atmosphere, and examples thereof include methane, ethane, carbon dioxide, methanol, ethyl ether, and acetone.

These carbon-containing substances may be supplied alone or as a mixed gas from the outside together with an inert gas constituting an atmospheric gas in the sputtering film forming apparatus. In some cases, radicals or ions generated when a compound that is difficult to gasify are decomposed by high energy, for example, activated atoms such as methylene and methyl may be used. It may be decomposed and released by impact.

In the present invention, first, in the first step, a film is formed by sputtering on the surface of the plastic substrate while performing a plasma treatment in a mixed gas atmosphere containing a carbon-containing substance and an inert gas. . At that time, the plasma processing is performed by, for example, applying a high voltage in a processing apparatus having an atmospheric pressure of about 10 to 10 ^-1 Pa to excite the atmospheric gas and exposing the surface of the plastic substrate to the gas plasma generated thereby. It is done by doing. In this case, if the energy of the gas plasma is too large, the surface of the substrate may be roughened due to decomposition, and a smooth optical reflection film may not be formed. Because of the shortage, it is desirable to appropriately adjust the plasma excitation voltage and current according to the actual apparatus, the material and size of the substrate to be processed, the composition of the atmosphere gas, and the like.

In the first step, the aluminum thin film formed by sputtering at the same time as the plasma treatment is a composite thin film containing a carbon-containing substance, and the thickness of the thin film is adjusted to be 200 to 400 °. Is good. When the film thickness is less than 200 °, the improvement of the adhesion becomes uncertain and the durability is poor. When the film thickness exceeds 400 °, further improvement of the durability cannot be expected, and the reflectance is rather lowered.

In a subsequent second step, aluminum is formed by sputtering on the composite thin film obtained in the first step. The film forming conditions at this time are, for example, about 10 to 10 ^-1 Pa. It can be carried out according to a usual method in a vacuum vessel using only the above-mentioned inert gas at atmospheric pressure as the atmospheric gas. Since the atmosphere gas in the second step is different from that in the first step, it may be carried out in a processing vessel different from the first step in order to avoid contamination by the carbon-containing substance contained in the atmosphere gas in the first step. preferable.

By adjusting the thickness of the aluminum film obtained in the second step to be 400 to 600 °, the total thickness of the reflection film is 700 to 800 °.
It is better to be. When the thickness of the reflective film is smaller than this, the reliability is inferior in terms of durability and the occurrence of defects.

[0017]

The thin film formed by sputtering aluminum or an aluminum alloy on the surface of a plastics substrate according to the method of the present invention has good adhesion to the plastics substrate and has a high quality. Since it has a light reflectance, this thin film can be used as it is as an optical reflection film. However, it is also possible to form an optical reflection film having further improved properties, for example, by forming a protective film made of a corrosion-resistant material on this thin film.

[0018]

EXAMPLE A PMMA substrate having a diameter of 300 mm and a thickness of 1.2 mm was mounted in a DC sputtering apparatus, and the inside of the apparatus was temporarily set to 10 mm.
After evacuation to ^-3 Pa, argon or a mixed gas of argon and methane was supplied at a predetermined flow rate (standard state gas cc / m
in) while maintaining the pressure in the device to about 1Pa,
Plasma was applied by applying a high voltage to the surface of the PMMA substrate, and aluminum was sputtered at an applied power of 20 kW to form a carbon-containing aluminum composite film.

Next, the substrate with the carbon-containing aluminum composite film thus obtained was transferred to a DC sputtering apparatus similar to the above, and the inside of the apparatus was once evacuated to 10 ^-3 Pa, and then argon was supplied at a flow rate of 15 cc / min. While supplying the pressure inside the device
While maintaining the pressure at about Pa, aluminum was sputter-deposited on the carbon-containing aluminum composite film surface of the substrate at an applied power of 20 kW to form an optical reflection film.

At this time, the flow rate and the film thickness of the atmosphere gas at the time of the film formation in the first step and the film thickness in the second step are
The reflectance (%) of each of the aluminum reflective films (Examples) formed and set as shown in Table 1 and the aluminum reflective films (Comparative Examples) formed only by the first step or the second step, respectively. The results are shown together with the measurement results of the adhesion between the reflective film and the substrate and the deterioration rate.

Here, the adhesion between the reflective film and the substrate was examined by a peeling test using an adhesive tape, and was evaluated from A (excellent) to E (excellent).
The deterioration rate is displayed in each of the following five stages. The deterioration rate is determined by performing an accelerated deterioration test on the reflective film for 150 hours in an atmosphere of 70 ° C. and 80% humidity, and determining the density of the generated defects by an S / N tester of an optical disk. And the value in the reflective film (control example) obtained by the vapor deposition method was expressed as a dB value, assuming 0 dB.

[0022]

[Table 1]

From these results, it can be seen that an aluminum reflective film having high adhesion and good durability can be obtained by the method for forming an optical reflective film of the present invention.

[0024]

According to the present invention, an optical reflection film having excellent adhesion can be efficiently formed on a PMMA substrate by a sputtering method, which has been considered to be unsuitable for practical use as an optical reflection film because of the low adhesion in the conventional method. Can be formed on the surface. The optical reflection film obtained by such a novel method has a high reflectance, and is suitable for use in an optical information disk.

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-4-3255941 (JP, A) JP-A-63-193341 (JP, A) JP-A-61-280050 (JP, A) JP-A-1- 177503 (JP, A) JP-A-4-204502 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G11B 7/26

Claims (4)

(57) [Claims] An aluminum or aluminum alloy film having a thickness of 200 to 400 ° is sputtered on a surface of a plastics substrate while performing a plasma treatment in a mixed gas atmosphere comprising a carbon-containing substance and an inert gas on a surface of a plastics substrate, Next, in an inert gas atmosphere, the thickness is 400 to 600 °.
Forming an aluminum or aluminum alloy film by sputtering. 2. The method according to claim 1, wherein the plastics substrate is formed of an acrylic resin. 3. The method according to claim 1, wherein the carbon-containing substance is a hydrocarbon compound or a carbon oxide. 4. The method for forming an optical reflection film according to claim 1, wherein the inert gas is argon.