JPH06180858A - Optical disk and its production - Google Patents

Abstract

PURPOSE:To produce an optical disk excellent in information preservability and highly resistant not only to the corrosion from the outer face of a recording film but also to the corrosion from the transparent substrate or backing film and recording bit forming part. CONSTITUTION:A recording film 5 consisting of a laminate of crystal grains 11 with the grain boundary coated with the forcedly oxidized layer 12 of a recording film material is formed directly on one side of a transparent substrate 1 or through a backing layer 4. The recording film is formed by granulating the recording film material in a vacuum atmosphere contg. oxygen when the film is formed in vacuum, selectively oxidizing the surface of the grain and laminating the grains with surface oxidized on the substrate or backing film to a specified thickness.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk and a manufacturing method thereof, and more particularly to a structure of a recording film having excellent corrosion resistance and a film forming method.

[0002]

2. Description of the Related Art When a recording film carried on a transparent substrate is oxidized, the recording sensitivity and the reproducing sensitivity are lowered, the recording error rate and the reproducing error rate are increased, and when the degree of oxidation further progresses, the information Recording / playback becomes impossible.

In order to prevent such inconvenience, a forced oxide film is formed on the outer surface of the tellurium recording film (the surface not in contact with the transparent substrate) and the forced oxidation is carried out, as described in, for example, Japanese Patent Laid-Open No. 3-120634. An optical disk has been proposed in which a lower recording film is protected from corrosion by a film.

[0004]

Since the outer surface of the recording film is passivated in the optical disk described in the above-mentioned known example, the outer surface of the recording film is exposed to a corrosive atmosphere, for example, high humidity air before recording. Even if exposed, the oxidation does not proceed to the inside of the recording film, and the recording film can be stably stored.

However, since the tellurium recording film records information by forming holes or pits (pits) in the irradiation portion of the recording light beam, the passivation film of the known optical disc is also recorded. Therefore, the forced oxide film is removed, so that corrosion progresses from the pit formation portion. Further, since an underlayer film for improving recording sensitivity, for example, a nitrocellulose film is generally formed on the underlayer of a tellurium recording film, an optical disk having a perforated recording film as in the above-mentioned known example is recorded after recording. Moisture in the air permeates into the base film through the pits formed in the film, and the recording film progresses from the interface on the side of the base film. Furthermore, when a plastic substrate is used as the transparent substrate, moisture in the air permeates from the transparent substrate side, so that the optical disc described in the above-mentioned known example cannot prevent corrosion of the recording film.

The present invention has been made to solve the deficiencies of the above-mentioned prior art, and the first object thereof is to stably store a recording film regardless of before and after recording and the type of transparent substrate. It is to provide an optical disc excellent in long-term storage property, and a second object thereof is to provide a method suitable for manufacturing such an optical disc.

[0007]

In order to achieve the first object, the present invention provides an optical disc in which a recording film is formed on one surface of a transparent substrate directly or via another film, The crystal grain boundary was formed of a laminated body of crystal grains covered with an oxide of the recording film material. The recording film is preferably made of a crystalline metal material such as tellurium or an alloy containing tellurium as a main component. Further, if a forced oxidation layer is formed at the interface of this recording film on the transparent substrate side, even better corrosion resistance can be obtained.

On the other hand, in order to achieve the above-mentioned second object, the present invention provides a method for manufacturing an optical disk in which a recording film is vacuum-deposited on one surface of a transparent substrate directly or via another film, and the vacuum of the recording film is used. At the time of film formation, the recording film material is made into particles in an oxygen-containing vacuum atmosphere to selectively oxidize the surface of the particles, and the particles whose surfaces have been oxidized are formed into a predetermined film on the transparent substrate or another film. The method of laminating up to the thickness was adopted. Also,
In order to further increase the corrosion resistance of the recording film, the recording film may be subjected to a forced oxidation treatment during or after the vacuum deposition of the recording film to form a forced oxidation layer on the interface on the transparent substrate side. Examples of the method for forcibly oxidizing the recording film include irradiation with ultraviolet light or heating, or irradiation with ultraviolet light under heating.

[0009]

When the crystal grains are covered with the oxide of the recording film material, the interface between the crystal grains is passivated, so that the corrosion resistance inside the crystal grains is improved. Therefore, high corrosion resistance can be exhibited even if moisture enters from any direction such as the outer surface side or the substrate side of the recording film, the problem of corrosion from the underlying film side after pit formation, and the case of using a plastic substrate. Can solve the problem of corrosion from the transparent substrate side. Further, even when a pit is formed in a part of the recording film by the information recording, the crystal grains around the pit are covered with the forced oxidation layer which is the passivation film, so that the corrosion resistance does not deteriorate.

On the other hand, regarding the manufacturing method, generally, the recording film is formed by a vacuum film forming method such as vacuum deposition or sputtering. However, an appropriate amount of aerobic gas (for example, pure oxygen or pure oxygen) is formed in a bell jar (vacuum film forming chamber). When film formation is performed while supplying clean air), the particle surface of the recording film material generated from the evaporation source or the target is oxidized in the process of being deposited on the transparent substrate. Therefore, a recording film whose crystal grain boundaries are covered with an oxide layer can be formed on the transparent substrate.

[0011]

1 shows a first example of a sectional structure of an optical disk according to the present invention. In the optical disc of this example, the transparent substrate 1 is
Parallel flat glass plate 2, UV (ultraviolet curing) resin layer 3 formed on the glass plate 2, and UV resin layer 3
The base film 4 and the base film 4 formed on the base film 4.
A recording film 5 is deposited on top. Reference numeral 6 in the figure indicates a pre-format pattern such as a guide groove of a recording / reproducing light beam or a pre-pit row in which an address signal is recorded. The preformat pattern 6 can be transferred to the recording film forming surface of the base film 4 or can be transferred to the base film forming surface of the UV resin layer 3. In the latter case, the preformat pattern 6 is applied to the UV resin layer 3
After the transfer, the base film 4 is formed on the transfer surface.

FIG. 2 shows a second example of the sectional structure of the optical disk according to the present invention. The optical disc of this example has a transparent substrate 1.
However, the pre-format pattern 6 is transferred on one surface of the plastic substrate 1, the base film 4 is attached to the pre-format pattern forming surface of the plastic substrate 1, and the recording film 5 is further formed on the base film 4. It is covered. As the plastic substrate material, the transparent substrate 1 is, for example, a polymer such as polycarbonate, polymethylmethacrylate, polypropylene, polyester, polyvinyl chloride, polyamide, polystyrene, or polyolefin.
And thermoplastic resins such as various modified polymers, copolymers and blends thereof, or thermosetting resins such as epoxy resins can be used.

The recording film 5 in FIGS. 1 and 2 is a so-called write-once recording film for recording information by forming pits in the irradiation portion of the light beam. For example, tellurium, selenium, lead, tin. , Bismuth and other chalcogenides. The base film 4 in FIGS. 1 and 2 is provided to promote the formation of pits in the recording film 5, and is, for example, nitrocellulose, polytetrafluoroethylene, polyimide, guanine, gold or gold-tin. It can be formed of an alloy or the like.

FIG. 3 shows a third example of a sectional structure of an optical disk according to the present invention. The optical disc of this example has a transparent substrate 1.
Is composed of a parallel flat glass plate 2 and a UV resin layer 3 formed on the glass plate 2, and a first enhance film 7, a magneto-optical recording film 8 are formed on the UV resin layer 3. Second
The enhancement film 9 and the metal reflection film 10 are applied in this order. Instead of the transparent substrate 1 including the glass plate 2 and the UV resin layer 3, the plastic substrate shown in FIG. 2 can be used.

The first and second enhancement films 7 and 9
Can be formed of an inorganic dielectric material made of, for example, a nitride or an oxide such as silicon, aluminum, zirconium, titanium, or tantalum. Further, the magneto-optical recording film 8 is
It can be formed by a rare earth-transition metal alloy, a platinum-manganese-antimony alloy (Heusler alloy), a manganese-bismuth alloy, a laminate of a platinum film and a cobalt film, or the like. Further, the metal reflection film 10 is made of aluminum,
It can be formed of gold, silver, platinum, or an alloy thereof.

4 to 6 schematically show the structures of the recording film 5 and the magneto-optical recording film 8. Recording film 5 of FIG.
(8) is formed by a deposited body of crystal grains 11, and each crystal grain boundary is covered with a forced oxidation layer 12 of a recording film material that constitutes the crystal grains. The recording film 5 (8)
It is practically difficult to cover all of the crystal grain boundaries forming the structure with the forced oxidation layer 12 without any gap. Therefore, as shown in FIG. 5, all or part of the crystal grain boundaries are covered with the forced oxidation layer 12. It does not matter even if the recording film 5 (8) is formed only from the undeposited crystal grains or only from such a deposit of crystal grains. The recording film 5 (8) of FIG. 6 has a forced oxidation layer 12 of a recording film material in which each crystal grain boundary constitutes the crystal grain.
It is formed of a deposit of crystal grains 11 covered with, and the forced oxidation layer 12 is also formed at the interface on the transparent substrate 1 side or the base film 4 side with a substantially uniform thickness. Also in the embodiment shown in FIG. 6, the recording film 5 (including only some of the crystal grain boundaries whose crystal grain boundaries are not covered with the forced oxidation layer 12 or only the deposited body of such crystal grains). 8)
May be formed. The forced oxidation layer 12 contains at least one kind of oxide selected from the oxides illustrated in FIG. 9 depending on the recording film material.

In the recording film of FIGS. 4 and 5, the recording film material is made into particles in an oxygen-containing vacuum atmosphere to selectively oxidize the surfaces of the particles, and the particles whose surfaces are oxidized are deposited on the transparent substrate. Alternatively, it can be formed by a method of stacking another film to a predetermined thickness. Specifically, it can be formed by vacuuming the inside of the bell jar to a predetermined high degree of vacuum and then vacuum vapor deposition or sputtering while supplying an appropriate amount of oxygen-containing gas such as pure oxygen or clean air into the bell jar. That is, according to this method, the particles of the recording film material generated from the evaporation source or the target are exposed to oxygen in the process of being deposited on the transparent substrate, and only the surface is selectively oxidized. A film is formed. Further, the recording film of FIG. 6 is obtained by depositing the recording film on the transparent substrate by the above-mentioned method and then irradiating it with ultraviolet rays from the transparent substrate side, heating it, or irradiating it with ultraviolet rays under heating. Can be formed by.

The curing of the present invention will be clarified below with reference to more specific examples. <Example 1> By a so-called 2P method, on one surface of a glass plate,
UV resin layer with a thickness of about 70 μm and a thickness of about 0.2 μm
After applying the nitrocellulose base layer of No. 1, in order to eliminate uneven curing or uneven reaction of the UV resin layer
The transparent substrate shown in FIG. 1 was produced by baking for 2 hours in an atmosphere of ° C. Next, this transparent substrate was housed in a bell jar and vacuum-deposited at a metal composition ratio of tellurium: selenium: lead = 80: 15: 5 to form a tellurium-selenium-lead alloy recording film on the nitrocellulose underlayer. It was vacuum deposited. During the vapor deposition of the recording film, the pressure inside the bell jar was reduced to 1 × 10 to ⁶ (Torr) or less in order to remove the residual gas components, and then pure oxygen gas was introduced into the bell jar to adjust the pressure inside the bell jar to 8 × was elevated to the deposition to 10 ~ ⁶ (Torr). Finally, the transparent substrate on which the recording film is vacuum-formed is baked in an atmosphere of 80 ° C. for 1 hour to crystallize the recording film and diffuse oxygen into each crystal grain boundary, so that the crystal grain boundary is a tellurium oxide film. A recording film covered with (TeO ₂ ) was formed (see FIGS. 4 and 5).

Example 2 The internal pressure of the bell jar at the time of forming the recording film was adjusted to 5 × 10 ⁶ (Torr). Other conditions were the same as in Example 1.

<Embodiment 3> The pressure inside the bell jar at the time of forming the recording film was adjusted to 1 × 10 ⁶ (Torr). Other conditions were the same as in Example 1.

Comparative Example 1 The recording film was vacuum-deposited in a state in which oxygen gas was not introduced into the bell jar and the inside of the bell jar was evacuated to 1 × 10 to ⁶ (Torr) or less. Other conditions were the same as in Example 1.

FIG. 7 shows Examples 1 to 3 in which information is written.
3 shows the reduction rate of the reflectance in the information pit forming part after the optical disk of Comparative Example 1 was left for 168 hours in an environment where the temperature was 80 ° C. and the relative humidity was 50%. As is clear from this graph, the optical disks of Examples 1 to 3 in which the recording film was vacuum-deposited in an oxygen-containing atmosphere were more reflective than the optical disk of Comparative Example 1 in which the recording film was vacuum-deposited in an oxygen-free atmosphere. The rate of decrease of the rate was low, and it was found that it was effective in preventing corrosion from the underlayer side. Further, from the comparison of Examples 1 to 3, it was found that the higher the amount of introduced oxygen gas, the higher the anticorrosion effect. However, when higher than Berujiya the pressure 1 × 10 ~ ⁵ during vacuum deposition (Torr), since the recording film is deteriorated altered by the recording and reproducing characteristics, Berujiya the pressure during the vacuum deposition was 10 through ⁶ ( Torr) is preferably adjusted.

<Embodiment 4> The bell jar is filled with 1 × 10 to
After reducing the pressure to ⁶ (Torr) or less, a mixed gas of oxygen and nitrogen having an oxygen gas / nitrogen gas ratio adjusted to 20/80 was introduced into the bell jar to perform vapor deposition. The degree of vacuum during vapor deposition was set to 8 × 10 ⁶ (Torr). Other conditions were the same as in Example 1.

<Embodiment 5> The inside of the bell jar is 1 × 10 to
After reducing the pressure to ⁶ (Torr) or less, a mixed gas of oxygen and nitrogen having an oxygen gas / nitrogen gas ratio adjusted to 40/60 was introduced into the bell jar to perform vapor deposition. Other conditions were the same as in Example 4.

<Embodiment 6> The inside of the bell jar is 1 × 10 to
After reducing the pressure to ⁶ (Torr) or less, a mixed gas of oxygen and nitrogen having an oxygen gas / nitrogen gas ratio adjusted to 60/40 was introduced into the bell jar to perform vapor deposition. Other conditions were the same as in Example 4.

<Embodiment 7> The inside of the bell jar is 1 × 10 to
After reducing the pressure to ⁶ (Torr) or less, a mixed gas of oxygen and nitrogen having an oxygen gas / nitrogen gas ratio adjusted to 80/20 was introduced into the bell jar to perform vapor deposition. Other conditions were the same as in Example 4.

<Embodiment 8> 1 × 10 to the inside of the bell jar
After reducing the pressure to ⁶ (Torr) or less, 100% oxygen gas was introduced into the bell jar to perform vapor deposition. Other conditions were the same as in Example 4.

<Comparative Example 2> 1 × 10 to the inside of the bell jar
After reducing the pressure to ⁶ (Torr) or less, 100% nitrogen gas was introduced into the bell jar to perform vapor deposition. Other conditions were the same as in Example 4.

FIG. 8 shows Examples 4 to 8 in which information is written.
3 shows the reduction rate of the reflectance in the information pit forming section after the optical disk of Comparative Example 2 was left for 168 hours in an environment where the temperature was 80 ° C. and the relative humidity was 50%. As is apparent from this graph, the oxygen gas / nitrogen gas ratio is 60/40.
When it is lower than the above range, no significant effect is observed in improving the corrosion resistance, but it has been found that the corrosion resistance is improved when the oxygen gas / nitrogen gas ratio is increased more than that. The same result was obtained by mixing a rare gas such as argon or krypton with oxygen gas instead of nitrogen.

<Embodiment 9> The inside of the bell jar is 1 × 10 to
After reducing the pressure to ⁶ (Torr) or less, clean room air having an air temperature of 23 ° C. and a relative humidity of 50% was introduced into the bell jar to perform vapor deposition. Degree of vacuum during vapor deposition is 8 × 1
It was set to 0 to ⁶ (Torr). For other conditions,
Same as Example 1.

After the optical disk of Example 9 was left in an environment of an air temperature of 80 ° C. and a relative humidity of 50% for 168 hours, the decrease rate of reflectance in the information pit forming section was measured. Almost the same good results were obtained. It is presumed that this is because the clean room air contains water and the oxygen in the water contributed to the oxidation of the recording film crystal grains.

[0032]

As described above, according to the present invention,
Since the crystal grains constituting the recording film are covered with the oxide of the recording film material, the interface of the crystal grains is passivated and the corrosion resistance inside the crystal grains is improved. Therefore, high corrosion resistance can be exhibited even if moisture enters from any direction such as the outer surface side or the substrate side of the recording film, the problem of corrosion from the underlying film side after forming the recording pit, and the use of the plastic substrate. In this case, the problem of corrosion from the transparent substrate side can be solved. Further, even when pits are formed in a part of the recording film due to information recording, the crystal grains around the pits are covered with the forced oxidation layer which is the passivation film, so that the corrosion resistance does not deteriorate. is there.

[Brief description of drawings]

FIG. 1 is a sectional view showing a first example of an optical disk according to the present invention.

FIG. 2 is a sectional view showing a second example of the optical disc according to the present invention.

FIG. 3 is a sectional view showing a third example of an optical disk according to the present invention.

FIG. 4 is an explanatory diagram schematically showing the structure of a recording film according to the present invention.

FIG. 5 is an explanatory diagram schematically showing the structure of the recording film according to the present invention.

FIG. 6 is an explanatory diagram schematically showing the structure of a recording film according to the present invention.

FIG. 7 is a characteristic diagram showing a relationship between oxygen gas pressure and reflectance decrease amount.

FIG. 8 is a characteristic diagram showing the relationship between oxygen concentration and reflectance decrease amount.

FIG. 9 is a table showing an example of oxides contained in a forced oxidation layer.

[Explanation of symbols]

 1 Transparent Substrate 2 Glass Plate 3 UV Resin Layer 4 Underlayer 5 Recording Film 7, 9 Enhance Film 8 Magneto-Optical Recording Film 10 Metal Reflective Film 11 Crystal Grain 12 Forced Oxidation Layer

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Norio Ohta 1-88, Tora-Tora, Ibaraki City, Osaka Prefecture Hitachi Maxell Co., Ltd.

Claims (6)

[Claims] 1. An optical disc having a recording film formed on one surface of a transparent substrate directly or via another film, wherein the recording film is formed of crystal grains whose crystal grain boundaries are covered with an oxide of the recording film material. An optical disc formed by a laminated body. 2. The optical disc according to claim 1, wherein a forced oxidation layer is formed on an interface of the recording film on the transparent substrate side. 3. The optical disc according to claim 1, wherein the recording film is made of tellurium or an alloy containing tellurium as a main component. 4. A method of manufacturing an optical disc in which a recording film is vacuum-deposited on one surface of a transparent substrate directly or via another film, and the recording film material is formed in a vacuum atmosphere of oxygen during the vacuum deposition of the recording film. A method for manufacturing an optical disc, comprising: forming particles into particles and selectively oxidizing the surfaces of the particles, and laminating the particles whose surfaces are oxidized to a predetermined film thickness on the transparent substrate or another film. 5. A method of manufacturing an optical disc in which a recording film is vacuum-deposited on one surface of a transparent substrate directly or via another film, and forced oxidation is performed on the recording film during or after the vacuum deposition of the recording film. A method for manufacturing an optical disk, which comprises performing a treatment to form a forced oxidation layer on the interface on the transparent substrate side. 6. The method for manufacturing an optical disc according to claim 5, wherein the forced oxidation treatment of the recording film is ultraviolet irradiation, heating, or ultraviolet irradiation under heating.