JPS61258787A - Information-recording medium - Google Patents

Abstract

PURPOSE:To provide a recording material in which bit error ratio is thermally stable and which has excellent sensitivity and S/N, by providing a recording layer having a specified composition and having a light absorptivity, or transmittance, which is varied by heating. CONSTITUTION:The recording material has the composition of general formula I. The recording layer is provided by vacuum deposition, sputtering, ion plating or the like. In the case of vacuum deposition, the composition is preferably controlled by using a quaternary vapor co-deposition method or applying a flash vapor deposition method to a vapor-deposited material having a specified composition. Although practically satisfactory characteristics can be obtained by using the recording layer solely, it is preferable to provide a reflective layer on or beneath the recording layer, since a higher S/N can be thereby obtained. A glass, a glass provided with photo-curable resin thereon, a plastic base of a polycarbonate, an acrylic resin, an epoxy resin, a styrene resin or the like, a metallic plate of an Al alloy or the like is used as a base.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a novel information recording material, more specifically, a recording layer provided on a predetermined substrate is irradiated with active light such as a laser beam, and the irradiated portion is The present invention relates to a medium for recording information using changes in reflectance.

(Prior Art) Until now, as recordable information recording media, for example,
2. Description of the Related Art Recording media are known in which a predetermined recording material is provided on a substrate, irradiated with laser light to form holes in accordance with information, and information is read out using the difference in reflectance depending on the presence or absence of the holes.

In this case, Te, which has a low melting point, and alloys or compounds containing Te, which have a low melting point, are used in this case (Japanese Patent Laid-Open No. 57-66966).

In addition, systems have been proposed in which the optical properties are changed by laser light irradiation and changes in reflectance caused by this change in optical properties are utilized.For example, a system in which fine particles of Te are dispersed in Tea (JP Publication No. 50-46317 @
), and those having a two-layer structure such as Sb2Te3/Te (Japanese Unexamined Patent Publication No. 186243/1983) are known.

However, in the above-mentioned pore-forming method, in addition to heating, the process of melting, dispersion, or evaporation is involved in forming the pores, so the viscosity at the time of melting and the surface tension at the time of dispersion are delicate. It is difficult to control the shape of the hole, and residues are generated inside the hole, resulting in increased noise and errors.

On the other hand, the method that utilizes changes in optical properties caused by heating by laser beam irradiation does not require the process of melting, dispersing, or evaporating the recording layer, making it easy to control the shape of the pits. , the problem of residue generation in the holes is also eliminated. However, conventional recording materials using this method have poor thermal stability, which has been a practical obstacle. The present inventors previously addressed these obstacles using the general formula (Sbx Te+-x) y Ge+-
y (However, 0.2≦X≦0.7.0.4≦y≦0.
It was shown that the recording material having the composition shown in 8) has excellent thermal stability.

(Patent Application No. 60-33779).

However, in the recording material represented by the above general formula, C/
Although it has excellent stability in N ratio and sensitivity, when used for digital signal recording, the stability of bit error rate is not necessarily satisfactory, especially under high temperature and high humidity. isn't it.

Problems to be Solved by the Invention In view of the above circumstances, the present invention provides an information recording medium that utilizes changes in optical characteristics caused by laser beam irradiation.
The bit error rate is thermally stable, and the sensitivity and S/
This provides a recording material with an excellent N ratio.

Means for Solving the Problems The present invention consists of a recording material whose light absorption coefficient, ie, transmittance, changes when heated, and information is recorded as a change in the light reflectance.

The recording material in the present invention has the general formula ((sb).

Te+-x) y t1+-J +-* Mz (
However, 0.2≦X≦0.7.0.4≦y≦0.8.0
．． It is a number in the range of 05≦2≦0.5, and M is AI%
51% TI% Vs Cr-, Mn1Fe 1CO1
Nis Cus ZnXY% Zrs Nb, MO%
Rus Rhs Pd.

Ag, Cds Ins Sn, Las CeX
Pr, Nds S11% Gds Tb5DY%
Hfs is a metal selected from Ta, W, A11% TI, PB, and old. ) It is characterized by having the composition shown by.

Conventionally, the compound Sb2Te+ was considered to be used in information recording materials because its transmittance changes greatly when heated, but due to the low temperature change, its thermal stability is extremely poor, making it impractical for practical use. was considered impossible to use.

[[Journal of Applied Physics (J
, A11I)1. Phys) J Volume 54 (Patient 3)
, pp. 1256-1260].

The present inventors took advantage of the characteristics of the two elements Sb-Te,
By adding Ge, we have found that the thermal stability can be greatly improved without changing the optical properties, but by further adding a metal as a fourth component to this composition, We have found that it is possible to further improve the stability of the bit error rate, which is important in practice.

The composition ratio of 5bXTe and Ge is such that X is 0.2 to 0.7
, preferably 0°3 to 0.6, y is 0.4 to 0.8,
Preferably it is in the range of 0.5 to 0.7. The value of X is 0.
If it is smaller than 2 or larger than 0.7, the change in absorption coefficient due to heating is small, and sufficient contrast cannot be obtained, resulting in a low S/N ratio.

On the other hand, if the value of y is larger than 0.8, the absorption coefficient changes due to heating at low temperatures, resulting in poor thermal stability and y
When the value of is smaller than 0.4, the change in the absorption coefficient is small and the S/N ratio becomes extremely low.

The fourth component metal M is AI% Si, Ti,
V% Cr5Mn5 Fe, Co, Ni, 011%
ZnsY, Zr-, Nb, Mo, Ru.

Rhs Pds Ag, Cd, Inz Sn,,L
as Ces Prs Nds Sm5Gd,, Tb
s DV% Hfs Tas W% ALI, TI,
PblBl% etc. can be used, especially Sns Bis In
,, TisCr,, Fe5CoSNisCLI%
Zn is effective. The value of Z is preferably in the range of 0.01 to 0.5, particularly preferably in the range of 0.1 to 0.3. When Z is smaller than 0.01, it hardly contributes to the stability of the bit error rate, and when it is larger than 0.5, the stability deteriorates on the contrary.

A vacuum evaporation method, a sputtering method, an ion blating method, etc. are used to form the recording layer.

To control the composition, in the case of a vacuum deposition method, it is preferable to perform a four-component co-evaporation method or a flash deposition method of a deposited material having a specific composition. In the case of sputtering, it is advantageous to use a target material of a specific composition or to place pieces of one element or compound on a target material of another element or compound. Regarding the distribution of the composition in the thickness direction, it is preferable for the four elements to be uniformly mixed in terms of characteristics such as the S/N ratio.

Practically sufficient characteristics can be obtained even when the recording layer is used alone, but
Furthermore, providing a reflective layer above or below the recording layer results in a higher S/N.
This is more preferable because the ratio can be obtained.

When the recording layer is used alone, the film thickness is 500 Å or more, preferably between 800 and 2000 Å. On the other hand, when a reflective layer is provided above or below the recording layer, the thickness of the recording layer varies depending on the material of the reflective layer, but is approximately 200 mm thick.
Preferably between 1 and 1000 people.

Materials that can be used for the reflective layer are not particularly limited, but include ■, Tis Cr, C0% Ni,
Se,, Zrs AgX In, Sn,, S
b-, Te, Pts 8us pb, Bi
metals such as, or alloys thereof are preferable.

Particularly preferred are AI% 5bSBi and BizTe=.

The reflective layer may be made of one of these elements or alloys, or may be a stack of two or more elements or alloys.

The thickness of the reflective layer is preferably 100 Å or more, and most preferably between 100 and 1000 Å from the viewpoint of sensitivity.

In the present invention, providing a layer made of a metal compound such as a metal oxide or nitride, or a layer made of an organic substance at least above or below the recording layer or at least above or below the reflective layer is effective for recording. It is more preferable in the sense of preventing deterioration of the layer or reflective layer over time. Examples of metal oxides include AI, G
% 5i1Ges Zrs 5esTi1 Tes
V, If,, Ces S11% LaX Sm,
, Y, Sbs Ta5 Pbs Bi, etc. are preferred.

Further, these metal oxides may be used alone, in a composite oxide, or in a stack of one or more metal oxides. 1 Examples of metal nitrides include CrN%TtN%'
1rNsAIN and the like are preferable because they are less prone to cranking. As the organic substance, various phthalocyanine pigments and fluorine-based polymers are preferable.

The film thickness of metal oxide, metal nitride, or organic substance is 10
0 manpower) or 10,000 people, more preferably 200 people
Preferably 1000 people.

As the substrate in the present invention, glass, a photocurable resin on glass, a plastic substrate such as polycarbonate, acrylic resin, epoxy resin, or styrene resin, or a metal plate such as A1 alloy are used.

When the recording medium of the present invention is actually used as an information recording medium, two identical disks each having a recording material provided on a substrate are placed with the surfaces provided with the recording material facing each other with a spacer interposed therebetween. A so-called air sandwich structure is used, in which two identical discs are bonded and integrated over their entire surface without a spacer, with the surfaces on which the recording material is provided facing each other. The structure may be a so-called full-surface adhesive structure, or a structure in which a recording material is provided on a film-like sheet and this sheet is wound into a roll, which is completely different from these structures.

Example The present invention will be explained in detail below by way of examples.

Reference example 1 Groove (700 mm deep, medium 0
．． On a 1.5 mm thick acrylic substrate with a pitch of 65 p m, pitch 1.6, cam), SbO, L was deposited by ternary co-evaporation from a Mo port into which Sb, Te, and Ge were introduced by resistance heating vacuum evaporation. ! lTeO,35G
A film having a composition ratio of e6.3 was formed to a thickness of 300 mm, and 200 mm of Sb was further applied thereon by the same resistance heating method.

The degree of vacuum at this time was 3 x 10-' Torr. This disk sample was rotated at a speed of 90 rpm, and a semiconductor laser (wavelength: 830 nm) was focused and irradiated through the transparent substrate to write a signal with a single frequency of 3 MHz.

At this time, the laser power used to record a signal at a location with a diameter of 140 mm on the disk was 41 mm on the recording surface.

To reproduce the signal, semiconductor laser light of the same wavelength is used,
It was played back at 1.2m.

The C/N ratio of the signal is 52d at a band width of 30K)
It was B.

The bit error rate of this recording medium was 3×10−′. After performing an acceleration test on this sample for 7 days under the conditions of 60℃ and 82%RH, when the signal was regenerated, the C/N was
Although the ratio remained unchanged, the error rate decreased by one order of magnitude to 3 x 10-4. Also, in the write test after the acceleration test, both the sensitivity and C/N ratio remained unchanged, but the error rate was 6X10-
It was S.

Conventional recording media have been evaluated based on the C/N ratio, but it has been found that the recording layer needs to have better stability in terms of bit error rate, which is a practical characteristic evaluation item for recording digital signals. .

Example 1 S
By four-component co-evaporation of bs Tes Ges and the metals shown in Table 1, (Sbo, +s Teo, *s Geo,:
+o) 9+IMIO (here M is the metal shown in Table-1)
A film with the composition was formed. The film thickness was 400 people. Furthermore, 200 sb membranes were placed on top of this. This recording layer was evaluated in the same manner as in Reference Example 1, and the results shown in Table 1 were obtained.

Table 1 shows the results of an accelerated test performed on this sample under conditions of 60° C. and 82% RH.

From Table 1, it can be seen that Sn and B1XIn are effective in stabilizing bit errors.

Example 2 Grooves (70 mm in depth) were formed in advance on a tempered glass disc with a thickness of 1.5 mm and a diameter of 305 mm using a photocurable resin.
By sputtering, Sbo, zs
A Sb2Te3 chip was placed on the Ge target so that the composition was Teo, 35Ge, 4, and the table
2, and the composition ratio of the added metals is as shown above (Sbo, zsTeo, 3sGeo, 4
), sputtering was performed to form a predetermined film with a thickness of 400 mm. Further, in the same sputtering apparatus, 200 nm was applied from the AI target onto the above film.
A human A1 membrane was formed. This recording medium was evaluated in the same manner as in Example 1, and the results shown in Table 2 were obtained. Furthermore, Table 2 shows the evaluation results after exposing these recording media to an accelerated test at 60° C. and 82% RHT day.

From Table 2, it can be seen that TI% Cr- and Ni are effective in stabilizing the error rate.

Table 2 Effects of the Invention According to the present invention, information can be recorded with high sensitivity and a high S/N ratio by irradiation with laser light, etc., and the bit error rate has excellent stability, which has great practical advantages. Media can be provided.

Patent applicant: Asahi Kasei Industries, Ltd. Procedural amendment July 3, 1985 Director General of the Patent Office Michibe Uga 1.Display of the incident 1985 Patent Application No. 100875 2. Name of the invention Information recording medium 3. Person who makes corrections Relationship to the case Patent applicant 1-2-6-4 Dojimahama, Kita-ku, Osaka-shi, Osaka Prefecture, subject to amendment Full statement (no changes to the contents)

Claims (1)

[Claims] An information recording medium in which a recording layer made of a material whose light absorption coefficient changes when heated is provided on a substrate, and information is recorded by a change in light reflectance caused by the change in the absorption coefficient. , the recording layer has the general formula {(Sb_xTe_1_-_x)_yGe_1_-_y
}_1_−_zM_z (where x is 0.2 to 0.7,
y is a number in the range of 0.4 to 0.8, z is a number in the range of 0.01 to 0.5, and M is Al, Si, Ti, V, N, Cr, Mn
, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, M
o, Ru, Rh, Pd, Ag, Cd, In, Sn, La
, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Hf,
The metal is selected from Ta, W, Au, Tl, Pd, and Bi. ) An information recording medium characterized by having a composition represented by: