JPH03153388A - Optical recording medium - Google Patents

Abstract

PURPOSE:To obtain a phase changing recording material with high sensitivity and excellent anti-humidity properties by using an element which is defined to a specified range as an average composition of a recording layer in a film thickness direction. CONSTITUTION:The average composition atomic % of a recording layer in a film thickness direction is expressed by a formula. In the formula, 50<=alpha<=90, 5<=x<=30, 0<=y<=20, 0<=z<=20, alpha+x+y+z=100 deg.C, A is one or more elements selected from group IV b elements; and B is one or more elements selected from among groups IVa, Va and VIa elements. For example, A is Ge, Sn and PbB is Ti, Zr, V, Cr. The crystal temperature of a Sb and Cu series is increased by adding group Nb element to the series and the amorphous phase becomes more stable. The anti-humidity properties of the series are improved by adding groups IVa, Va and VIa elements.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a phase change optical recording medium, and particularly to an optical recording medium with excellent moisture resistance.

[Prior Art] There are many inventions of phase change recording media, and many of them contain Te as a main component.

The oldest one is Te Kokoku No. 41-28891
-Ge type, As-Te-Ge type, Te-0 type, etc. are disclosed. A relatively recent representative example is JP-A-63.
xGeTe (1-
x) SbzTe3.

Optical recording using phase change does not involve deformation of the recording film, so it has the advantage of being able to produce double-sided discs made by directly bonding two discs together, or single-disc discs in which a protective layer is provided directly on the recording film.

Taking a single-plate disk as an example, the typical layer structure of a disk is such that a dielectric layer, a recording layer, and a dielectric layer are sequentially laminated on a substrate as shown in FIG. This is to prevent the recording layer from being deformed during the recording/erasing process by sandwiching the recording layer between strong dielectric materials. Since this dielectric layer also serves as a moisture absorption prevention layer, the disk also has good moisture resistance.

By the way, among the reversible phase changes between amorphous and crystal, the change from an amorphous phase to a crystalline phase is highly sensitive, so
By utilizing only this, it is possible to create a high-sensitivity write-once type disc. In this case, there is no need for dielectric sandwiching,
In order to obtain a low-cost write-once disc, it is desirable to have a structure in which a recording layer is directly provided on a resin-molded substrate, as shown in FIG. 1, for example. In this case, since there is no moisture absorption prevention layer, the moisture resistance of the recording layer itself is important.

Now, many of the various phase change materials that have been proposed so far have Te as a main component. Te has a large absorption in the semiconductor laser wavelength range, and an amorphous phase is easily formed, so it is suitable for a phase change recording material. However, since the crystallization temperature of Te alone is too low, the amorphous phase is unstable at room temperature. Therefore, combinations with various elements were tried,
Materials with very excellent recording and reproducing properties have been obtained (Japanese Patent Laid-Open No. 63-225934).

However, since Te has poor moisture resistance, although a disk configuration as shown in FIG. 2 can be used, there is a problem in that reliability cannot be ensured with a low-cost configuration as shown in FIG. 1.

[Problems to be Solved by the Invention] The present invention aims to provide a phase change recording material with excellent moisture resistance.

[Means to solve the problem] In the present invention, the main component of the recording layer is sb.

Similar to Te, sb has large absorption in the semiconductor laser wavelength range and is likely to form an amorphous phase. and,
Moisture resistance is quite good compared to Te. If Sb is used alone, the crystallization temperature will be too low and the amorphous phase will become unstable, so it is necessary to stabilize the amorphous phase by adding elements. The present inventors produced recording films using combinations of various elements and sb, and investigated their recording characteristics. in this case,
The so-called as-depo film is in an amorphous phase, and this state was treated as an unrecorded state and evaluated using a crystallization recording method in which recording marks of a crystalline phase are formed by laser beam irradiation.

The result was that in most cases the noise level increased at the same time as recording, and the C/N ratio was poor considering the signal amplitude was large. However, we have found a phenomenon in which the noise level does not specifically increase only when Cu is selected as the additive element. Therefore, the second essential component of the recording layer is Cu. By adding a group IVb element to the sb and Cu system, the crystallization temperature of the system increases and the amorphous phase becomes more stable.

Furthermore, when Na%Va and Via group elements are added to the sb and Cu system, the moisture resistance of the system is further improved. Based on the above, the present invention is an optical recording medium characterized in that the average composition (atomic %) of the recording layer in the film thickness direction is expressed by the following general formula.

Two-pronged type] ・i Sb, Cux AY Bz [However, 5G≦a≦90. 5≦x≦30.
O≦y≦20.0≦2≦20, a + x + y
+ z m 100 , A represents one or more elements 1 selected from the lVb group elements, B represents at least one or more elements selected from the IVaSVas Via group elements].

The inventors have discovered that the above structure provides a phase change recording material with high sensitivity and excellent moisture resistance, leading to the present invention.

In the above general formula, if α is less than 50, sufficient recording sensitivity cannot be obtained, and if it exceeds 90, the amorphous phase becomes unstable.

If X is less than 5, the effect of suppressing the increase in noise level due to Cu as described above will be insufficient, and if it exceeds 3o, recording sensitivity will decrease.

When y and z each exceed 20, the recording sensitivity also decreases.

The recording layer can be formed by vacuum deposition, sputtering, or the like. In vacuum evaporation, it is desirable to perform co-evaporation from a plurality of evaporation sources from the viewpoint of composition control. Further, in sputtering, an alloy target having a desired composition may be used, or a composite target may be used in which chips of each element are combined in a mosaic shape at an area ratio according to each composition.

The thickness of the recording layer is 100~300G! , preferably 30
0 to 2000 people.

As the substrate material, polycarbonate, PMMA1 polyolefin, transparent resin such as epoxy, or glass can be used. Tracking guide grooves, guide bits, and preformats such as address signals may be formed on the substrate surface.

A protective layer can be suitably provided on the recording layer, and examples of the material include SiO, 5iOz, TiO2, 5i3Nn.
, inorganic compounds such as ZnS, polycarbonate, acrylic, polyamide, epoxy, polyolefin, and other resin materials can be used. Acrylic or epoxy ultraviolet curing resins are also suitable examples of materials. Each of the above materials may be used alone, or a plurality of them may be mixed or laminated.

The thickness of the protective layer is not particularly limited, and may be appropriately selected depending on the purpose, such as increasing the thickness if scratch resistance is important.

It goes without saying that an undercoat layer may be provided between the substrate and the recording layer, if necessary.

[Example] Hereinafter, the present invention will be specifically explained with reference to Examples.

Example 1 Sputtering was performed on a polycarbonate injection molded substrate with a tracking guide groove, the composition of which was approximately Sb.
, 5Cu 15G e 5 Ti B was formed to a thickness of about 700 mm.

This medium was installed in an optical disk tester, and the laser beam wavelength was 780 ns, N, A, 0.5, and linear velocity was 11.3 Iil.
Recording and reproduction were performed under the following conditions: sec, recording signal frequency of 3.7 MHz, recording light power of 5 s Vs, reproduction light power of 0.5 mW, and the C/N (bandwidth of 30 kHz) was measured.

Furthermore, after storing this medium in an environment of 60° C. and 90% RH for 30 days, the C/N was measured again under the above conditions.

Examples 2 to 7 Recording layer compositions S b BCursG e 5 Z r BS b
6sCu ssG e 5 V 15S
b6sCussGe5 Crys SbssCutsSns Ties S b 65Cu 15P b 5 T i 1sS
b An optical recording medium was produced under the same conditions as in Example 1, except that 2 g of 6sCu +5T i was used, and tested under the same conditions.

Example 8 In Example 1, a protective layer of ZnS was further added on the recording layer by approximately 2
An optical recording medium was produced under the same conditions as in Example 1 except that 000 A was provided, and tested under the same conditions.

Example 9 An optical recording medium was prepared under the same conditions as in Example 1, except that an epoxy ultraviolet curable resin protective layer of about 5 μm was further provided on the recording layer in Example 1, and tested under the same conditions.

Comparative example 1 In Example 1, the recording layer composition was Ge2°sb.

- An optical recording medium was produced under the same conditions as in Example 1, except that T e was 6, and tested under the same conditions.

Comparative Example 2 In Comparative Example 1, a protective layer of ZnS was further added on the recording layer by approximately 2
An optical recording medium was produced under the same conditions as in Comparative Example 1, except that the number of participants was 1,000, and the test was conducted under the same conditions.

Comparative Example 3 An optical recording medium was prepared under the same conditions as in Comparative Example 1, except that a protective layer of epoxy ultraviolet curable resin with a thickness of about 5 μm was further provided on the recording layer in Comparative Example 1, and tested under the same conditions.

The evaluation results are shown in Table-1.

Table 1 FIG. 1 is a schematic cross-sectional view showing an example of the structure of the optical recording medium of the present invention. FIG. 2 is a schematic cross-sectional view showing the structure of a conventional optical recording medium.

l...ultraviolet curing resin layer, 2...recording layer, 2...substrate, 4...dielectric layer.

Claims (3)

[Claims] (1) An optical recording medium characterized in that the average composition (atomic %) of the recording layer in the film thickness direction is represented by the following general formula. General formula Sb_αCu_XA_YB_Z However, 50≦α≦90 5≦x≦30 0≦y≦20 0≦z≦20 α+x+y+z=100 A is one or more elements selected from group IVb elements, B is group IVa, Va, VIa group Represents one or more elements selected from the elements. (2) The element represented by A in the general formula is Ge, Sn, P
The optical recording medium according to claim 1, wherein the optical recording medium is one or more elements of b. (3) The element represented by B in the general formula is Ti, Zr, V
, Cr. , Cr.