JPH02297737A - Optical recording medium - Google Patents

Abstract

PURPOSE:To prevent corrosion, deformation and defect of a metal reflecting layer and to improve recording sensitivity, qualities of signals, secular stability and storage stability of the medium by forming the metal reflecting film by sputtering a metal essentially comprising Al in an environment into which an inert gas is introduced to a specified pressure. CONSTITUTION:The metal reflecting film is formed by sputtering a metal essentially comprising Al under the condition that an inert gas is introduced at >=10 mTorr into the environment. When the gas pressure is raised to a certain value, molecules of the gas to be fetched into the thin film being formed increase, while trace amts. of water and oxygen which remain with the inert gas in the vacuum chamber are also fetched into the thin film. The molecules of water and oxygen incorporated into the thin film uniformly disperse therein to make Al inert and to make the thin film of the metal reflecting layer chemically stable. Thereby, the metal reflecting layer has improved corrosion resistance and is free from deformation and defect, and thus, secular stability and storage stability of the medium can be enhanced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical recording medium, and particularly to improving the storage durability of an optical recording medium having a metal reflective layer on a transparent substrate.

(Prior Art and its Problems) In recent years, optical recording media have been widely used for large-capacity data files and the like as media readable by laser light.

The optical recording medium is a so-called R media that only plays back video discs, compact discs, CD-ROMs, etc.
There are OM type media, WO type media that can be written once, magneto-optical media that can be freely rewritten, and phase change media.

In a ROM type medium, information is formed as prepits on a substrate during injection molding, and a thin film of a metal dielectric layer is formed on this substrate to reflect light for reproduction.

The WO type body records and reproduces information by utilizing changes in light transmission/reflectance characteristics due to laser beam irradiation.

In addition, in a magneto-optical medium that can be freely rewritten, information is recorded by thermomagnetic reversal of the magnetic domains of a vertical ζn film, and information is reproduced by the Kerr effect. In phase change media, information is recorded and reproduced using changes in the light transmission/reflectance characteristics of the crystal layer and the amorphous layer.

In addition, the shape of the optical recording medium includes a single-sided recording type humpact disk type medium that has an optical recording layer, a protective layer, etc. on the substrate and is used as a single disk, a 3.5-inch magneto-optical disk, etc. There are some double-sided recording type media used by bonding two media together with an adhesive, some WO type magneto-optical media, phase change media, and the like.

A common requirement of the above optical recording media is that they must have a certain degree of reflectance because reproduction is performed using laser light. In order to satisfy this requirement,
In said ROM type media, a thin film of metallic reflective layer is used;
In the WO type body, not only those using a dye-based recording layer but also those using a metal recording layer have a metal reflective layer in order to obtain an appropriate reflectance and improve signal quality. has been established.

Magneto-optical media also use metal reflective layers to improve signal quality during readout.

It is important that the material of the metal reflective layer used in the optical recording medium has high light reflectance, and Au, Ag, Al
(aluminum) etc. are used.

Among them, Al is widely used from the viewpoint of cost, and is formed on a substrate together with a recording layer, a protective layer, etc. in the form of a thin film by a vacuum film forming method such as a spunter method or a vacuum evaporation method.

However, a problem with Al metal reflective layers is that they have low durability.

That is, in particular, it is relatively easy to corrode, and as time passes, the reflectance decreases, resulting in deterioration of the characteristics of the optical recording medium.

In order to improve this problem, for example,
As disclosed in JP-A No. 7743, JP-A-63-224049, and JP-A-63-224050, a film was formed by adding metals such as Ti, Se, and Ag to Al. Methods have been proposed to increase the corrosion resistance of thin metal reflective layers.

This method was somewhat effective against corrosion caused by oxidation and the like.

However, Tjl seems to be due to crystallization as disclosed in JP-A-62-137743.
It is insufficient to prevent the deformation defect called H41loc, which is accompanied by local deformation of the film. When the medium is stored for a long period of time under high temperature and high humidity, deformation defects of cover irregularities, which are different from those of the Hilloc, are observed, and there is no means to prevent such deformation defects.

Further, no method has yet been proposed for preventing corrosion and defects in the metal reflective layer by devising a method for forming the metal reflective layer.

Corrosion and deformation defects in the metal reflective layer described above cause an increase in noise, an increase in BER (pit error rate), and a decrease in phase margin during use and storage, which is a serious problem for the practical use of optical recording media. there were.

[Problems to be Solved by the Invention] The present invention has been made in view of the problems of the prior art described above. In particular, by preventing corrosion and deformation defects of a metal reflective layer mainly composed of Al, recording The purpose of the present invention is to provide an optical recording medium with excellent sensitivity and signal quality, and excellent stability over time and storage stability.

[Means to solve problems]

The object of the present invention is to provide an optical recording medium having a thin film of a metal reflective layer mainly made of Al (aluminum) on a transparent substrate, in which the metal reflective layer is formed until a gas pressure of 10 layers↑orr or more is reached. This is achieved by an optical recording medium characterized in that it is a thin film formed by sputtering a metal mainly composed of Al under conditions where an inert gas is introduced.

Since the optical recording medium of the present invention has an Is film which is a metal reflective layer mainly composed of Al, the thermal conductivity can be controlled by controlling the amount of added elements, so it is possible to obtain a medium with good recording sensitivity. can.

Further, when the optical recording medium is a magneto-optical recording medium, excellent signal quality can be achieved by forming the recording layer into an riI film and utilizing both the Kerr effect and the Faraday effect.

Furthermore, an inert gas was introduced into the vacuum film forming chamber at a gas pressure of 10 ta.
By forming the thin film of the metal reflective layer after the temperature reaches Torr or higher, excellent corrosion resistance can be obtained, especially when the
It prevents deformation defects such as loose irregularities that are characteristic of the use of real-melt adhesives when creating OCs and double-sided recording type optical recording media, and prevents deterioration in terms of noise, BER, phase margin, etc. over time and during storage. It is possible to obtain almost no optical recording media. Inert gases include Ar, Fle, Ne,
Kr etc. can be used.

The above-mentioned advantages against corrosion and deformation defects of the metal reflective layer in the optical recording medium of the present invention are brought about by the conditions for forming the y1 film of the metal reflective layer mainly composed of Al by sputtering or the like.

In other words, when the gas pressure increases to a certain extent, more gas molecules are incorporated into the thin film formed, and a trace amount of water and oxygen remaining in the vacuum deposition chamber along with the inert gas are also incorporated into the thin film. It is presumed that this is because water and oxygen uniformly distribute within the IF film and inactivate Al, thereby chemically stabilizing the thin film of the metal reflective layer.

In the optical recording medium of the present invention, the inert gas pressure when forming the thin film of the metal reflective layer mainly composed of Al is l Ql T
or more, and particularly preferably from 10 mTorr to 2011 Torr.

If the inert gas pressure is less than I Om Torr, the corrosion resistance of the metal reflective layer, particularly the effect of preventing modification defects, will be reduced. Furthermore, if the inert gas pressure becomes too large, a large amount of inert gas will be incorporated into the metal reflective layer mainly composed of Al, and the density of the thin film will be lost. X
1 (I” Torr or less).

In particular, the above-mentioned advantage of the optical recording medium of the present invention is manifested in the prevention of deformation defects of gentle irregularities that often occur in double-sided recording type optical recording media using hot melt adhesives.

The metal reflective layer of the optical recording medium of the present invention is usually formed by a vacuum film forming method, and generally a sputtering method or a vacuum evaporation method is employed.

For example, a sputtering method is preferably a magnetron sputtering method using RF or DC power, and a vacuum evaporation method is preferably a heating method using an EB gun.

The above-mentioned advantage of the optical recording medium of the present invention is that the metal reflective layer is 2N
It is particularly large when Al has a purity higher than that.

Even if the alloy contains various metals in Al, the above-mentioned advantages are still great, but if the alloy contains Al at 90 atomic % or more, preferably 99.9 to 95 atomic %, the reflectance will increase. This is preferable because corrosion resistance and deformation defect resistance can be improved without a significant decrease in .

In particular, when the optical recording medium of the present invention is a magneto-optical recording medium, the thermal conductivity of the metal reflective layer affects the recording sensitivity, so it is preferable to use Al and Ta as a single component rather than Al as a single component.

Nb, Cr, Yi, Zr, In, Mn, Ni.

An alloy with at least one metal selected from Mg, P, V, W, PC, Au, Ag, Cu, etc. is preferable.

The thickness of the thin metal reflective layer in the optical recording medium of the present invention is not particularly limited by the structure of the present invention, and may be any commonly used thickness.

For example, if the optical recording medium of the present invention is a magneto-optical recording medium, the WA thickness of the metal reflective layer is usually 200 to 200 mm.
It is good if it is within the range of 0 people.

The structure, material, film thickness, etc. of the thin film of the other layer laminated with the metal reflective layer of the optical recording medium of the present invention are not limited to the structure of the present invention.

When the optical recording medium of the present invention is a reflective type optical disc, the metal reflective layer is directly formed on the surface of the substrate having the group grooves.

Further, in the case of a WO type medium or a magneto-optical recording medium, a recording layer and a dielectric protective layer are formed on the top layer of a stacked film. In the case of a double-sided recording type magneto-optical recording medium, an organic resin protective layer such as an ultraviolet curable resin may be further provided on the metal reflective layer. Even with the organic resin protective layer, the above characteristics of the optical recording medium of the present invention,
Of course, the advantages are not lost.

Therefore, in the case of a double-sided recording type magneto-optical recording medium, the hot melt adhesive is coated directly on the metal reflective layer or on the top surface of the organic resin protective layer, and the two sheets of light (ff) are coated on the substrate. are bonded together with the metal reflective layer facing outside and the metal reflective layer facing inside.

In this case, hot melt adhesives used include synthetic rubber-based, EVA-based, acrylic-based, and polyamide-based resins.

Materials for the substrate used in the optical recording medium of the present invention include polycarbonate, polymethyl methacrylate, epoxy, glass, etc., but polycarbonate and polymethyl methacrylate exhibit the characteristics of the optical recording medium of the present invention most effectively. , a resin substrate such as epoxy.

Among the resin substrates, polycarbonate substrates have advantages such as low water absorption and high glass transition temperature, and are preferably used in the optical recording medium of the present invention.

In the present invention, when the optical recording medium is a magneto-optical recording medium, thin films of various oxides and metals can be used as the recording layer. For example, MnB1゜MuAlCe, M
Crystalline materials such as ncuBi, Cd IG, B1SmEr
Single crystal materials such as Ga IG, B1SmYbCoGe1C, as well as GdCo, GdFe, TbFe, DyFe
, C; dFeBi.

This is a thin film using an amorphous material such as CdTbFe, GdFeCo, or TbFeCo. Among these, a recording layer mainly composed of rare earth metals or transition metals is most preferable in terms of sensitivity, C/N, etc.

Further, in the present invention, when the optical recording medium is a phase change type recording medium, various Te-based and non-Te-based alloys or dyes are used as the recording layer.

In the present invention, when the optical recording medium is a magneto-optical recording medium, a dielectric protective thin film is provided adjacent to the above-mentioned recording layer, for example, by sandwiching the top and bottom of the recording layer, and a metal reflective layer is formed thereon. By doing so, a medium with the highest C/N can be obtained. The dielectric protective layer that can be used in the present invention is, for example, SiOx, SiNx, Al
Dielectric materials such as oxides, nitrides, and sulfides such as Nx and ZnS are preferable. Among them, silicon nitride is preferable from the viewpoint of optical properties and protective function, as disclosed in JP-A-59-121368. Most preferred.

In the present invention, when the optical recording medium is a magneto-optical recording medium, the thickness of the recording layer is usually 150 to 500 mm, and the thickness of the dielectric protective layer is usually 200 to 200 mm.
There are 0 people.

It is preferable that the first dielectric protective layer has a capacity of 300 to 1,500 people, and the second dielectric protective layer has a capacity of 100 to 600 people.

Each layer provided on the substrate in the magneto-optical recording medium is formed by a vacuum film forming method, and usually by a sputtering method.

〔Effect of the invention〕

When forming the metal reflective layer of the optical recording medium, by increasing the inert gas pressure to a relatively high level of 10 n Torr or more, the corrosion resistance of the metal reflective layer of the resulting optical recording medium is improved and deformation defects are reduced. This can improve stability over time and storage stability. In particular, deformation defects caused by gentle unevenness peculiar to double-sided recording type optical recording media using hot melt adhesives can be made less likely to occur.

[Example = 1] The initial vacuum degree in the first chamber was set to 3 X l O-' Torr by exhausting from the exhaust port directly connected to the cryopump of the continuous sputtering apparatus. Subsequently, 10100c of 3N high-purity Ar gas and 5 sec of N2 gas were introduced into the first chamber, and the conductance of the continuous sputtering device was fully opened to bring the gas pressure in the first chamber to lvb Torr. . and,
moving the polycarbonate substrate on which the first dielectric protection layer is formed next from within the first chamber to a second chamber by a Si metal nitrogen gas reaction spunter method;
The Ar gas pressure in the second chamber was set at 1 m Torr.
After that, 25% of Fe, Co, Cr, alloy, and Tb were deposited on the first dielectric protective layer using a binary simultaneous sub-lid method.
0 person's membrane pressure Tbt+ (Feq*C01sCrq)
A recording layer consisting of a thin film of yv was formed.

Furthermore, the polycarbonate substrate having the laminated film in which the recording layer is deposited on the first dielectric protective layer is moved into the third chamber, and the recording layer is deposited for 350 minutes under the same deposition conditions as the first dielectric protective layer. A second dielectric protective layer consisting of a thin film of SiNx was formed on the recording layer.

Thereafter, the polycarbonate substrate on which the second dielectric protective layer has been formed is moved to a fourth chamber, the conductance is narrowed, and the A in the fourth chamber is
After setting the r gas pressure to 20■↑orr, add A with a purity of 3N.
A RFit force of 1 kHz is applied to the target to perform spattering to form a metal reflective layer of an Al fl film with a thickness of 250 mm on the second dielectric protective layer, and then the second dielectric protective layer is formed on the polycarbonate substrate. A magneto-optical recording layer was prepared as a laminated film in which a first dielectric protective layer, a recording layer, a second dielectric protective layer, and a metal reflective layer were formed in this order.

On the magneto-optical recording layer, an ultraviolet curable resin #5D-17 manufactured by Dainippon Ink (I) was applied by spin coating and cured by irradiation with ultraviolet rays to form an organic resin protective layer with a thickness of 2 μm.

After applying Hontomelt adhesive #XW-13 manufactured by Toagosei Kagaku ■ on the organic resin protective layer using a roll coater, the polycarbonate 1 substrate was placed on the outside and the organic resin protective layer was placed on the inside. Towards this end, two sheets of the medium produced as described above were pressed together to obtain a sample of a double-sided recording type optical recording medium.

(Comparative Example-1) A sample of a double-sided recording type optical recording medium was obtained under the same conditions as in Example-1 except that the Ar gas pressure during the formation of the metal reflective layer was 1 mTorr.

[Example 2] Sample #I of a double-sided recording medium was obtained under the same conditions as Example 1, except that an Al-Ta alloy containing 5 at % of Ta was used as the metal reflective layer.

[Comparative Example-2] A sample of a double-sided recording type optical recording medium was obtained under the same conditions as in Example-2, except that the gas pressure of A was set to 1 mTorr when forming the metal reflective layer.

C Example-3] A sample of a double-sided recording medium was obtained under the same conditions as Example-1, except that an Al--Tl alloy containing 2 at % Ti was used as the metal reflective layer.

[Comparative Example-3] A sample of a double-sided recording type optical recording medium was obtained under the same conditions as in Example-3, except that the Ar gas pressure during the formation of the metal reflective layer was 1 mTorr.

[Comparative Example-4] A sample of a double-sided recording type optical recording medium was obtained under the same conditions as in Example-1, except that the gas pressure of A" was set to 5 mTorr when forming the metal reflective layer.

[Example 4] A sample of a double-sided recording type optical recording medium was obtained under the same conditions as in Example 1, except that the Ar gas pressure during the formation of the metal reflective layer was set to Low Torr.

The BER, phase margin, and recording/erasing noise of Samples A to H of the double-sided recording type optical recording media obtained as described above were measured by the following methods.

BER: 1800rpm, f=3.7Hllz
A single frequency signal was recorded and expressed as the number of missing bits relative to the total number of focuses during rack playback.

Phase Margin 2 The phase time margin for a constant error rate was measured using a phase margin measuring device. (This is commonly used as an industry term.) The results obtained are shown in Table 1.

Table 1 Next, samples of each double-sided recording type optical recording medium were heated at 80°C and 190°C.
%RH for 1000 hours. Each characteristic was measured after being left standing. The results are shown in Table 2.

In addition, in Comparative Example 1 and Comparative Example 4, corrosion occurred on the entire surface of the metal reflective layer even after being left for 500 hours, making measurement impossible.

Table 2 Patent Applicant: Fuji Photo Film Co., Ltd. 1, Incident Indication: Heisei/Year Patent Application No. 11P11! No. 2, Title of the invention Optical recording medium 3. Relationship with the person making the amendment Patent applicant Location 210 Nakanuma, Minamiashigara City, Kanagawa Prefecture Name (520) Fuji Photo Film Co., Ltd. Subject of amendment "Details of the invention" in the specification Contents of the amendment The description in the ``Detailed Description of the Invention'' section of the specification is amended as follows.

1) Page 3, line 19 “After improved J. "of" Insert.

2) Page 3, line 7 "Hanbakuto" r compact” and correct it.

3) Page 7, line 5 “I can do it.” "can." to correct.

4) Page 7, line 6 [Insert inert gas into the vacuum deposition chamber] [Inert gas in the vacuum deposition chamber] and correct it.

5) Page 7 ■ 4th line "As for" “As a person,” and correct it.

6) Page 9, lines 15-16 r99.9 to 95 atomic%” [95 atomic% or more J and correct it.

7) Page 10, line 2 rYt” rTi” and correct it.

8) No.] Page 0, line 15 "Reflective type" rROM type” and correct it.

9) Page 10, line 19 "Dielectric resistance" "Dielectric" and correct it.

10) Page 71413, line 2 "So thin film" "Layer thin film J and correct it.

11) Page 13, line 9 "Silicon nitride" "Silicon nitride J and correct it.

12) Page 14, line 2 "Gas Gas" "gas" and correct it.

13) Page 14, line 19 "Dielectric resistance" "Dielectric" and correct it.

14) Page 15, line 4 "Membrane pressure" "Film thickness" and correct it.

Claims (3)

[Claims] (1) In an optical recording medium having a thin film of a metal reflective layer mainly made of Al (aluminum) on a transparent substrate, the metal reflective layer is coated under conditions in which an inert gas is introduced until the gas pressure reaches 10 mTorr or more. An optical recording medium characterized in that it is a thin film formed by sputtering a metal mainly composed of Al. (2) The content of Al in the metal reflective layer is 90 atomic %
The optical recording medium according to claim 1, wherein the optical recording medium is as follows. (3) On a transparent substrate, a first dielectric protective layer, a recording layer, a second
2. The optical recording medium according to claim 1, comprising a magneto-optical recording layer having a laminated film in which a dielectric protective layer and the metal reflective layer are formed in this order.