JPH04182950A - Optical recording medium - Google Patents

Abstract

PURPOSE:To prevent the deterioration of a recording layer by using a tantalum oxide film contg. a small amt. of a specified metal oxide. CONSTITUTION:At least one of the groups III and IV metals of the periodic table such as Al, Si, Ti, Sn, Zr and Hf is added to or incorporated into a metallic Ta target by 0.1-10 atomic % and the resulting target is used or a chip of a group III or IV metal is arranged on a metallic Ta target at the time of sputtering so as to alloy a formed thin film. Superior aging stability is ensured and deterioration at high temp. and humidity can be prevented.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to an optical recording medium used for optical recording.

[Conventional technology and its issues]

A magneto-optical recording medium is a recording medium in which recording is performed by heating a recording layer formed on a transparent substrate by light irradiation, and reading is performed using magneto-optical effects such as the Kerr effect and Faraday effect. As the recording layer, TbFe, Tb
FeCo, DyFeCo, GdFeCo, GdTbFe
Rare earth/transition metal thin films such as Co are often used.

These recording layers generally have the disadvantage of being very susceptible to oxidation and having poor corrosion resistance. For this reason, it is known to protect the recording layer by providing an interference layer or a protective layer made of a transparent dielectric material such as metal oxide or metal nitride on both sides of the recording layer. In addition to protecting the recording layer as described above, the interference layer also has the role of lowering the reflectance due to the interference effect, lowering noise, and improving the C/N ratio.

As an interference layer (protective layer), S izN, , AfN, A
When a metal nitride such as fSiN is used, cranking occurs in the film due to the difference in thermal expansion coefficient between the plastic substrate (for example, polycarbonate or acrylic resin) and the metal nitride. For this reason, when the metal nitride is used in a plastic substrate, it is complicated to provide an undercoat layer between the substrate and the metal nitride. Also, instead of metal nitride, A, A
, 03, SiO□ or SiO prevents the occurrence of cracks, but it also reacts with the recording layer, resulting in a decrease in characteristics.

As a method to solve these problems, it has been proposed to use tantalum oxide as an interference layer etc.
171141). When this tantalum oxide is used as an interference layer, the occurrence of cranking and deterioration of the recording layer are greatly improved, and it is suitable as an interference layer, etc. However, when the device is used for a long time under high temperature and high humidity It was found that the recording layer deteriorated slightly.

[Means to solve the problem]

The inventors of the present invention have made extensive studies to overcome the problems of optical recording media using tantalum oxide interference layers, etc., as described above. As a result, the above-mentioned problems can be solved by using a tantalum oxide film containing a small amount of a specific metal oxide. The present invention has been completed based on the discovery that an optical recording medium can be obtained in which the above points are improved and the recording layer does not deteriorate.

[Structure of the invention]

The gist of the present invention is to provide an optical recording medium in which a layer containing tantalum oxide as a main component is provided as an interference layer or a protective layer on a substrate, wherein the interference layer or protective layer is made of tantalum metal and has 0.1 to 10 atoms of tantalum oxide as a main component. Obtained by reactive sputtering in the presence of oxygen gas and an inert gas using a target containing at least one metal component selected from the group of Group I or Group II metals of the periodic table. The present invention resides in an optical recording medium characterized by a thin film layer containing tantalum oxide as a main component.

Hereinafter, the present invention will be explained in detail.

The present invention is applicable to all optical recording media that use a tantalum oxide film as the interference layer or protective layer of the recording layer, such as magneto-optical recording media and phase change recording media.

In the present invention, a resin substrate such as a polycarbonate resin or acrylic resin, a glass substrate, or the like is used as the transparent substrate. The thickness of the substrate is approximately 1 to 2 mm.

The case of a magneto-optical recording medium will be explained below.

As the recording layer formed on the substrate surface, a known magneto-optical recording layer structure can be adopted. For example, TbFe
, quality magnetic alloys of rare earths and transition metals such as TbFeCo, TbCo, DyFeCo, MnBi, MnCuB
A polycrystalline perpendicular magnetization film, such as i, etc., can be used. As the magneto-optical recording layer, a single layer may be used, or a GdTb
Two or more recording layers such as Fe/Tb may be stacked and used.

The thickness of the recording layer is 100 to 1,000 mm, preferably 2
00 to 500 people.

Note that an interference layer is usually provided between the substrate and the recording layer. The interference layer uses the light interference effect of a transparent film with a high refractive index to lower the reflectance and reduce noise.
This is to improve the N ratio. As the interference layer forming material, a specific tantalum oxide film described in detail below is used. The thickness of this interference layer is 400 to 1,500, preferably 50 to 1,000, more preferably 700 to 1,000.
It is 9008.

Further, it is desirable to provide a protective layer made of a dielectric material made of the same material as the interference layer on the surface of the recording layer opposite to the interference layer.

In a medium having a structure in which a reflective layer is provided, a metal of high reflectivity (for example, Al, Cu, etc.) or The alloy is provided as a reflective layer.

The thickness of the reflective layer is 100~CoO0, preferably 20
Approximately 0 to 600 people.

Further outside the reflective layer, it is also possible to provide a hard coat layer consisting of an organic protective layer (for example, a curable resin layer that is cured by ultraviolet rays, light, heat, etc.) for the purpose of improving mechanical strength and preventing thermal deformation. It is.

In the present invention, a target containing a specific metal component in tantalum metal is used as the interference layer or protective layer,
A thin film mainly composed of tantalum oxide (TazOs) is used, which is formed by performing DC or RF reactive sputtering in a mixed gas atmosphere of oxygen gas and an inert gas, such as argon gas. The target used in the present invention is a metal tantalum target, and its purity is usually:
A11.99.9% or more. , Si, Ti, Sn,
At least one metal component selected from the group of Group Ⅰ and Group Ⅰ metals of the periodic table such as Zr and Hf is added or contained in an amount of 0.1 to 10 atomic %, preferably 1 to 5 atomic %. things are used. A method of alloying a thin film by placing small pieces of the above-mentioned Group (1) or Group (2) metal on a metal tank target during sputtering is also within the scope of the "target containing a metal component" in the present invention.

If the content of Group Ⅰ or Group Ⅰ metal components of the periodic table in the above target is less than the lower limit, a slight defect may occur in the film due to lack of oxygen during the process of forming a tantalum oxide film by reactive sputtering, and the film cannot be used under high temperature and high humidity. If the amount exceeds the upper limit, the tantalum oxide concentration in the film decreases and the original function of the tantalum oxide film deteriorates, which is not preferable.

As for the above reactive sputtering conditions, a metal tantalum target is usually used, and reactive sputtering is performed using oxygen gas and argon gas to form an oxidized tank TaOx (x#2
．． 5) fii! The conditions for forming a film are adopted, and in the case of DC reactive sputtering, the sputtering gas pressure is 10X10-3.
Tor r or less, preferably IXI O-3 to 5XI
O-'Tor r, film deposition rate is 0.1-100
Performed in the human/second range.

Next, the phase change recording medium will be explained.

The layer structure of a phase change recording medium usually includes a structure of substrate 1/interference layer 2/recording layer 3/protective layer 4/hard coat layer 5,
Substrate I/interference layer 2/recording layer 3/protective layer (second interference) 4/
An example is the configuration of reflective layer 6/hard coat layer 5.

As the substrate 1, the above-mentioned transparent substrate is suitably used.

The interference layer 2 and the protective layer 4 are thin films made of tantalum oxide, each having a thickness of 100 to 50 mm. OO0
Used within the scope of humans.

The tantalum oxide thin film formed according to the present invention described above is used.

The recording layer 3 is an alloy thin film containing, for example, three elements: Ge (germanium), sb (antimony), and Te (tellurium). In the present invention, the recording layer 3 may be made of only three elements, C, e, Sb and Te, and these include Sn, In, Pb, As, Se, Si, Bi, Au,
One or more elements selected from the group consisting of Ti5Cu, Ag, Pt, Pd, Co, Ni, etc. may be added. The composition of the recording layer 3 is particularly Ge.
A composition containing an excess of sb in a pseudo-binary alloy containing 5Tes and 3b4Te as constituent components is preferable, and the amount of excess sb is preferably 0≦sb≦20 atomic %. Further, the thickness of such a recording layer 3 is 100 to 1
,000 people is preferable.

The hard coat layer 5 is provided to improve mechanical strength and prevent thermal deformation, and as its material, a curable resin that is cured by ultraviolet rays, light, heat, etc. is suitably used, and in particular, an ultraviolet curable resin is used. is preferred.

With the layer structure described above, the hard coat layer 5 is provided on the protective layer 4 with the optical reflective layer 6 interposed therebetween.

By providing the reflective layer 6, a large contrast in reflectance can be obtained, and the reflective layer 6 also has the effect of promoting the diffusion of thermal energy absorbed by the recording layer 3. However, the reflective layer 6 is not necessarily necessary. It is not necessary to provide this. The reflective layer 6 is made of AI!, which has a high reflectance. ,,Au
, Ag, Ni, etc. are used. When providing the reflective layer 6, the thicknesses of the interference layer 2, recording layer 3, and protective layer 4 are determined taking into consideration the interference effect including the reflective layer.

Example 1, Comparative Example 1 A polycarbonate substrate was introduced into a magnetron sputtering device, and after first evacuating to 5×10 −′ Pa or less, 20 SCCM of Ar and 5 SCCM of 0□ were introduced to adjust the pressure to 0.8 Pa. In this state, a 4-inch φ Ta target containing 2 atomic % of Ti (a target made by adding 2 atomic % of Ti to a metal Ta product of 99.9% or more) was subjected to DC sputtering with a power of 500 W, and a sputtering rate of 4 people/second was applied. 800 tantalum oxide interference layers were formed at high speed.

After evacuating the chamber once, Ar gas was pumped to 30sccR.
The Tb target and Feq were introduced to a pressure of 10,3 Pa. Perform simultaneous sputtering of Co, target and T b23 (F eqoc OIl+)
? ? 300 recording layers were formed on the interference layer. Further T
A7 with a chip! Swap the target in Ar gas Ar 9? 30 consisting of an alloy of T a 3
A reflective layer was formed for 0 people.

Furthermore, after evacuating the chamber once, Ar gas was evacuated for 20S.
CCM, 53CCM of Oz gas introduced, Ti 2at%
Protective films for 400 people were formed using a Ta target (99.9% or more metallic Ta product with 2 at% Ti added).

(Disk A) Comparative Example 3 A disk was obtained in the same manner as in Example except that a N (99.9%) Ta target was used. (Disc B) After pasting these discs A and B together with their recording layers facing each other, they were placed under the conditions of a temperature of 80°C and a humidity of 85%.
,000Hr acceleration test was conducted.

While there was almost no change in the hide error rate for disk A, for disk B it increased by 1.6 times.

〔Effect of the invention〕

The optical recording medium of the present invention has excellent stability over time and can be used under high temperature and high humidity conditions.

Claims (1)

[Claims] (1) In an optical recording medium in which a layer mainly composed of tantalum oxide is provided as an interference layer or a protective layer on a substrate, the interference layer or protective layer is made of tantalum metal and 0.1
By reactive sputtering in the presence of oxygen gas and an inert gas using a target containing at least one metal component selected from the group of group III and group IV metals of the periodic table in an amount of ~10 at % An optical recording medium characterized by having a thin film layer containing the obtained tantalum oxide as a main component.