JPH09251673A - Sputtering device for optical disk and film formation - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate the need for a dehumidifying and drying stage for a plastic substrate manufactured by an injection molding method at the time of forming an optical disk by using the plastic substrate made of PC (polycarbonate), etc., having high hygroscopicity. SOLUTION: A target mounted on a cathode and the plastic substrate are arranged to face each other in a static state and a recording film is formed on the substrate. In such a case, this device is arranged with the plastic substrate facing on the central axial line of the target, a substrate holder holding the plastic substrate and having plural pieces of gas vent holes and a suction port of a vacuum pump in this order by aligning their central axes. The formation of the multilayered films composed mainly of the recording layer is executed by a sputtering method in this method after the substrate is manufactured by an injection molding method using plastic having the hygroscopicity as a raw material, the substrate is set on the substrate holder having plural pieces of the gas vent holes.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plastic substrate for an optical disk, and more particularly to a dehumidifying device and method for dehumidifying a plastic substrate having high hygroscopicity.

[0002]

2. Description of the Related Art Among optical discs, a recording film of a magneto-optical disc, in particular, uses an amorphous alloy of a rare earth element and an iron group, but this material is chemically active and easily oxidized. Further, even in a phase-change type optical disc using a chalcogen element for a recording film, there is a problem that gas such as moisture contained in or adsorbed on the substrate deteriorates the recording film. On the other hand, as substrate materials, plastics such as polycarbonate (hereinafter abbreviated as PC), acrylic, polyolefin resin, etc. are used in addition to metal, glass, etc., but when plastics are stored in a normal environment, moisture in the atmosphere is also used. Absorbs. When left in a general atmosphere (23 ° C., 50% RH), the moisture content of the PC substrate before drying is about 2000 to 3000 ppm by weight. When a recording layer is formed on a PC substrate that has absorbed moisture in this way, the moisture contained in or adsorbed on the substrate is released into the vacuum film forming chamber, and the recording layer is oxidized.
Low reflectance, occurrence of pinholes (pitting corrosion),
The magneto-optical disk has a problem that the magnetic characteristics are deteriorated and good recording / reproducing characteristics cannot be obtained. Therefore, when the recording layer is formed by the usual method, the substrate is left in vacuum for several hours, or a dehumidification treatment is performed in which the moisture contained in the substrate is released in advance by heating it to 80 ° C or higher. , The moisture in the substrate is 20
It can be reduced to about 0 ppm, and if the recording layer is formed in this state, an optical disk with good characteristics can be manufactured. The current general optical disc manufacturing method is to injection mold a PC substrate, cool it in an electrostatic blow, then coat the protective resin layer on the read side by spin coating, and dry it at 90 ° C.
After degassing for about 2 hours in a normal atmosphere, set it on the substrate holder in the vacuum film forming chamber of the sputtering device,
After evacuation for 3 hours, a multilayer film including a recording layer is formed. Fig. 4 shows a typical single-layer film forming sputtering apparatus.
Substrate 1 mounted on substrate holder 5 in vacuum film forming chamber 8
Is arranged facing the target 4 on the cathode 3,
The vacuum exhaust port is provided at an arbitrary position.

[0003]

In the above steps, the dehumidification treatment of the substrate requires a dehumidification equipment different from the sputtering apparatus, and it takes a long time for heating and evacuation, resulting in poor productivity. However, there was a problem that the equipment and devices also became larger. The present invention is to provide a sputtering apparatus and a film forming method that do not require a dehumidifying step of a plastic substrate manufactured by an injection molding method when forming a film on an optical disk using a plastic substrate such as a PC having high hygroscopicity. To do.

[0004]

In order to solve such a problem, the present inventors have changed from the storage state of the raw material plastic related to the moisture content of the optical disk substrate to the substrate injection molding step, the substrate drying step and the film forming step. The present invention has been completed by tracing changes in moisture content, examining the most efficient dehumidification method, and establishing reproducible conditions. The gist of this is that in a sputtering apparatus in which a target mounted on a cathode and a plastic substrate are arranged in a statically opposed state, and a recording film is formed on the substrate, the plastic substrate and the plastic substrate are opposed to each other on the central axis of the target. And a substrate holder having a plurality of degassing holes and a suction port of a vacuum pump are arranged in this order with their respective central axes aligned with each other. A second aspect of the present invention is a method of manufacturing an optical disc using a plastic substrate,
After a plastic substrate is prepared by injection molding using a hygroscopic plastic as a raw material, the substrate is set in a substrate holder having a plurality of gas vent holes of the sputtering apparatus, and a multilayer including a recording layer is mainly formed by the sputtering method. A method for manufacturing an optical disk is characterized by forming a film.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION The greatest feature of the present invention will be described with reference to the drawings. FIG. 1 is an explanatory diagram of a batch type sputtering apparatus representing one embodiment of the present invention. FIG. 2 is a detailed view of the substrate holder 5 that holds the plastic substrate.
Is a top view and (b) is a vertical sectional view. Further, FIG. 3 is an explanatory diagram of the in-line type sputtering apparatus. The greatest feature of the present invention is that, as shown in FIGS.
In a sputtering apparatus in which a target 2 mounted on a cathode 3 inside and a plastic substrate 1 are arranged in a statically opposed state, and a recording film is formed on the substrate, the plastic substrate 1 is opposed to the center axis of the target 2 , A substrate holder 5 for holding a plastic substrate and having a plurality of gas vent holes 7 (see FIG. 2), and a suction port 9 of a vacuum pump, which are arranged in this order with their respective central axes aligned. The recording film is produced by this sputtering apparatus generally using an in-line type sputtering apparatus which is a mass continuous production method shown in FIG. 3, and the injection-molded plastic substrate 1 is preheated or subjected to a long-time treatment. Load lock chamber 10 without dehumidifying by vacuum exhaust
Then, it is mounted on the substrate holder 5 having the gas vent hole 7, and is set in the vacuum film forming chamber 8 through the vacuum transfer chamber 11. The vacuum film forming chamber is always set to 1 by the vacuum pump 9 except during sputtering film forming.
It is kept below × 10 ^-4 Torr. The moisture released from the back surface of the substrate transported to the vacuum film forming chamber is stored in the substrate holder 5
The plurality of gas vent holes 7 provided on the substrate are discharged from the suction port 9 of the vacuum pump on the coaxial line with the substrate. In this manner, the multilayer film forming process mainly including the recording layer is sequentially performed in the state where the moisture of the substrate is continuously discharged.

The substrate holder 5 of the present invention is preferably provided with a large number of large-diameter gas vent holes 7 to reduce the resistance to gas flow until the substrate holder 5 has sufficient strength to perform its function as a substrate holder. It is also possible to provide a plurality of minute protrusions on the substrate contact surface side of the substrate holder to form a gap between the substrate and the substrate holder, and to enhance gas distribution efficiency along with gas vent holes. Further, the vacuum pump suction port 9 is arranged on the back surface of the substrate holder and at a position where each axis is aligned,
It is necessary to set the diameter to an appropriate value from the exhaust capacity of the vacuum pump and the exhaust gas velocity to improve the vacuum exhaust efficiency that also serves as dehumidification.

A multi-layer film formation processing apparatus using the sputtering method is composed of the batch type single-layer film formation sputtering apparatus shown in FIG.
An apparatus is known in which at least a plurality of films to be formed are connected and arranged linearly or circumferentially on the same plane, and films are sequentially formed on a substrate on a conveyor under the same vacuum environment. In addition, as shown in FIG. 3, the sputtering apparatus of FIG. 1 is used as a unit and connected by at least the number of film formations and arranged on the circumference of the same vertical surface, and on the circumference of the disk under the same vacuum environment. Alternatively, the substrate 1 set in the substrate holder 5 attached to the tip of the radial arm
There is disclosed an in-line type sputtering apparatus in which a film is rotated to sequentially form a film. In the conventional technique, as shown in FIG. 4, the position of the vacuum pump suction port is far from the substrate,
Although the positions of the cathode, the substrate, the substrate holder, and the vacuum pump suction port are set as in FIG. 1, the substrate holder does not have exhaust means such as a sufficiently large exhaust hole, so that the moisture released from the back surface of the substrate is There is a device that goes into the vacuum film forming chamber without being directly evacuated, which sometimes deteriorates the characteristics of the optical disk.

The applicable range of the present invention is particularly effective in the case of a magneto-optical disk in which the recording film is made of a metal which is easily oxidized, and appears as a large difference in characteristics, but in the case of a phase change type optical disk. In addition, the gas released from the substrate may become a problem and the characteristics may deteriorate. Again, in this case,
By using the sputtering apparatus and the film forming method of the present invention, it is possible to eliminate the influence of the gas emitted from the plastic substrate on the optical disc characteristics.

The function of the present invention is to remove moisture and the like by forming a plurality of gas vent holes in the substrate holder of the sputtering apparatus and arranging the vacuum pump suction port on the back surface of the substrate holder and on the same axis. Since the released gas can be prevented from flowing into the vacuum film formation chamber during the film formation by sputtering, a preliminary drying step and a device for previously dehumidifying the moisture content of the substrate are not necessary.

[0010]

EXAMPLES The embodiments of the present invention will be specifically described below with reference to examples and comparative examples, but the present invention is not limited to these. (Evaluation of Quality Characteristics of Magneto-Optical Disk) With respect to the magneto-optical disk according to the present invention, reflectance, coercive force, CNR (Carrier to Carrier to
Noise Ratio) was measured. The signal recording conditions are as follows. Disk rotation speed: 2400 rpm, measurement position: radius 24 mm, pulse interval: 3.87 MHz, pulse width: 60 nsec, recording bias magnetic field: 2500 e, recording laser output: 2.
Data recorded under this condition for 4 to 12 mW was reproduced with a laser output of 1.0 mW, and the CNR value was measured when the intensity of the second harmonic became a minimum.

Example 1 A PC board of 86 mmφ × 1.2 mmt injection-molded from polycarbonate resin, Panlite 9000TG (trade name of Teijin Chemicals Co., Ltd.) pellets as a raw material was used for 2 days.
Water content stored in a clean room at 23 ℃ and 50% RH
PC board 1 which has not been subjected to 2000 ppm heat drying treatment,
The substrate holder 5 provided with the gas vent holes 7 of the present invention in the load lock chamber 10 of the in-line type sputtering apparatus at intervals of 4 seconds.
The vacuum transfer chamber is kept at a vacuum of 1 × 10 ^-5 Torr for 1 second, and the recording film is sequentially deposited by the DC magnetron sputtering method by stopping at a predetermined position in the vacuum film deposition chamber. did. The recording film is a Si N protective layer (film thickness 18
nm), a Tb-Fe-Co alloy recording layer (15 nm), a Si N protective layer (38 nm) and an Al reflective layer (80 nm). Then, the formed disk was taken out from the sputtering apparatus through the load lock chamber 10, and immediately a protective coat (film thickness 10 μm) made of UV resin was applied on the recording film by a spin coater to manufacture a magneto-optical disk. The quality characteristics of the product were measured and are shown in Table 1.

[0012]

[Table 1]

(Embodiment 2) As in Embodiment 1, a PC board of 86 mmφ × 1.2 mmt, which has not been heat-dried in advance, is
It is attached to the substrate holder 5 provided with the gas vent hole 7 of the present invention in the load lock chamber 10 of the in-line type sputtering device,
Protective layer (120 nm) composed of a mixture of SiO ₂ and Zn S, G
A recording layer (30 nm) made of e-Sb-Te, a protective layer (20 nm) made of a mixture of SiO ₂ and ZnS, and an Al reflective layer (60 nm) were sequentially formed. The protective layer was formed by RF magnetron, and the recording layer and the reflective layer were formed by DC magnetron sputtering method. Next, the deposited disk is taken out from the sputter device through the load lock chamber, and immediately a protective coat made of UV resin (film thickness 10 μm) is applied on the recording film by a spin coater to produce a phase change type optical disc. The reflectance was measured and is also shown in Table 1.

(Comparative Example 1) 90 in a clean open in advance
A substrate having a water content of 200 ppm, which has been heat-dried at ℃ for 2 hours, is mounted on the substrate holder having a gas vent hole of the present invention and evacuated at 1 × 10 ^-5 Torr for 2 hours. ,
A magneto-optical disk was manufactured under the same conditions as in Example 1. The product quality characteristics are also shown in Table 1.

(Comparative Example 2) A magneto-optical disk was produced by forming a recording film on a PC substrate under the same conditions as in Example 1 except that a conventional substrate holder having no gas vent hole was used, and its quality characteristics were obtained. Is also shown in Table 1.

(Comparative Example 3) A vacuum pump suction port 9 as shown in FIG. 4 is arranged in the direction perpendicular to the axis of the target-PC substrate, and a sputtering apparatus provided with a substrate holder having no vent holes is used. A recording film was formed under the same conditions as in Example 1, a magneto-optical disk was produced, and its quality characteristics are shown in Table 1.
It was also described in.

(Comparative Example 4) P was used under the same conditions as in Example 2 except that the conventional substrate holder having no vent hole was used.
A phase change recording film was formed on the C substrate to manufacture a phase change optical disk. The reflectance of the product is also shown in Table 1.

From the above results, the magneto-optical disk (Comparative Example 1) formed after the PC substrate was sufficiently heated and dried and the disk formed using the substrate holder of the present invention (Example 1) were used. , The reflectance, the coercive force, and the CNR all show the same characteristics, indicating that there is no problem at all. However, in the case of the disk (Comparative Example 2) formed by the conventional substrate holder having no gas vent hole, sufficient characteristics could not be obtained due to the gas such as water released from the PC substrate. Also, with respect to the disk (Comparative Example 3) manufactured by using the conventional sputtering apparatus as shown in FIG. 4, the recording film was oxidized by the gas released from the substrate, and good characteristics were not obtained. Further, also in the case of the phase change type optical disk, the present invention exhibits superior characteristics as seen in Example 2 and Comparative Example 4.

[0019]

By using the sputtering apparatus of the present invention, even when a film which is liable to be deteriorated by moisture is formed on a hygroscopic plastic substrate, the substrate is completely dehumidified before the film forming operation. It is not necessary to carry out, and a film having stable characteristics can be produced. Since the film-formed substrate can be stored for a long time in a normal clean atmosphere or a clean container, a large clean oven is not particularly required, and its industrial utility value is extremely high.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional explanatory view of a batch type single layer deposition sputtering apparatus of the present invention.

FIG. 2 is a view showing an embodiment of a substrate holder of the present invention. (A) Top view, (b) Vertical sectional view

FIG. 3 is a vertical cross-sectional explanatory view of an in-line type multi-layer film forming sputtering apparatus used in the present invention.

FIG. 4 is a vertical cross-sectional explanatory view of a single-layer film forming sputtering apparatus according to a conventional technique.

[Explanation of symbols]

 1 substrate, 2 target 3 cathode, 4 deposition plate 5 substrate holder, 6 mask mounting hole 7 gas vent hole, 8 vacuum film forming chamber 9 vacuum pump suction port, 10 load lock chamber 11 vacuum transfer chamber

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shinyasu Fukushima 2-13-1, Isobe, Annaka City, Gunma Prefecture Shin-Etsu Kagaku Kogyo Co., Ltd., Institute for Precision Materials (72) Inventor Makoto Saito Annaka City, Gunma Prefecture 2-13-1 Isobe Shin-Etsu Chemical Co., Ltd. Precision Materials Research Laboratory (72) Inventor Toshimi Kobayashi 2-3-1 Isobe, Annaka-shi, Gunma Shin-Etsu Chemical Industry Co., Ltd.

Claims (2)

[Claims] 1. In a sputtering apparatus in which a target mounted on a cathode and a plastic substrate are placed in a statically opposed state, and a recording film is formed on the substrate, the plastic substrate and the plastic are opposed to each other on the central axis of the target. An optical disk sputtering apparatus, comprising: a substrate holder that holds a substrate and has a plurality of gas vent holes; and a suction port of a vacuum pump arranged in this order with their respective central axes aligned. 2. A method for manufacturing an optical disk using a plastic substrate, which is manufactured by injection molding using a hygroscopic plastic as a raw material,
A method for manufacturing an optical disk, wherein the substrate is set on the substrate holder of the sputtering apparatus according to claim 1, and a multilayer film mainly including a recording layer is formed by a sputtering method.