JPH0714657B2 - Optical information recording member - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] The present invention relates to an optical information recording member for recording / reproducing optical information utilizing light, heat, etc. An object of the present invention is to provide an optical information recording member that has excellent repetitive characteristics of recording and erasing, has a small erasing rate variation with time, and can record and reproduce information signals at high speed and high density.

Optical disks using laser light include a write-once type in which recording and reproduction are performed only once and a rewritable type in which a recorded signal can be erased and repeatedly used. The present invention is the rewritable type of the latter. Belong to The present inventors have previously proposed a method in which a change in reflectance due to a phase transition between an amorphous state and a crystalline state of Te-TeO ₂ is used as a signal. In addition, various additives (Sn, Ge, Bi, In, Pd, Tl, Se, etc.) are also added to Te-TeO ₂ as a rewritable recording film utilizing phase transition. , It has been clarified that a recording film having high C / N and excellent moisture resistance can be obtained.

By the way, the above recording film containing an oxide has the following drawbacks. For rewritable optical disks, Te-
Erase is performed in the crystalline state of TeO ₂ , and recording is performed in the amorphous state. The phase transition between crystalline and amorphous is carried out by changing the conditions of cooling by laser light and rapid cooling. That is, after heating with laser light, it becomes crystalline by cooling and becomes amorphous by quenching. Therefore,
By repeating recording and erasing, the recording film repeats a phase transition between a crystalline state and an amorphous state. In this case, if an oxide is present in the recording film, the mobility of the chalcogenide is reduced due to the high viscosity of the film, and segregation of the film composition is likely to occur.
Furthermore, since the oxide has a low thermal conductivity, a difference in temperature distribution is generated between the incident side and the opposite side of the laser beam, which also causes segregation of the film composition. For the above reasons, the recording film containing an oxide has a drawback that the characteristics gradually change due to repeated recording and erasing. The present invention eliminates this drawback,
It is intended to improve various properties such as C / N, erasure rate, moisture resistance and heat resistance of a conventional recording film made of a chalcogen compound.

[Structure of the Invention] The optical information recording member of the present invention contains tellurium (Te), germanium (Ge) and tin (Sn) as main components, and the proportions of these elements are Te, Ge and Sn of 100 at% respectively. The coordinates (at
%) Is A (Te ₉₃ Ge ₅ Sn ₂ ), B (Te ₉₃ Ge ₂ Sn ₅ ), C (Te
₆₈ Ge ₂ Sn ₃₀ ), D (Te ₅₂ Ge ₁₈ Sn ₃₀ ), E (Te ₅₂ Ge ₄₆ Sn ₂ ).
The amount of indium (In) added as a subcomponent to the main component has a composition within the range surrounded by 5 points, and the amount of the Te-Ge-Sn system forming the main component is m. , And the value of the sub-component In is n (m + n = 100), the value of n is 1
It is characterized by having a recording film of -40 at%.

Attempts to use chalcogen compounds for recording films are old, and Te-Ge
In addition to the above, there are examples in which As, S, Si, Se, Sb, Bi and the like are added to improve the characteristics. Rewritable recording films made of these chalcogenides are generally used for recording,
It is characterized by poor stability against repeated erasing. The reason is that Te, Ge and other added components cause phase separation of the recording film by repeating several times, and the constituent components of the recording film are different at the initial stage and after the repeating. When the phase transition is utilized in an erasable recording film, a method is usually used in which the unrecorded and erased states are crystalline and the recorded state is amorphous. In this case, recording is performed with a laser beam, and the recording film is melted and quenched to be amorphous. However, since the current semiconductor laser has a limited power, a recording film having a low melting point has high recording sensitivity. . Therefore, in order to improve the recording sensitivity, the recording film made of the above chalcogenide has a composition having a melting point as low as possible, that is, a film composition containing a large amount of Te. The fact that the content of Te is larger than that of the other additive components means that phase separation is likely to occur in the repeating characteristics. Therefore, how to fix the excess Te added to lower the melting point to make the composition difficult to move is a repeating characteristic and
This will have a great influence on the change over time of the CNR and erase rate.

A feature of the present invention is that In is added to the above-described conventional composition Te-Ge-Sn to fix excess Te. As a method of fixing excess Te, the concentration of Ge and Sn is increased and stoichiometric GeT
Although it is possible to use e or SnTe, when Ge is added, the transition temperature from amorphous to crystalline becomes high and a large laser power is required for recording and erasing, which is not practical. Further, in the case of Sn, if the composition near SnTe is close to the stoichiometry, it is crystalline after vapor deposition and a stable amorphous state cannot be obtained. Therefore, it is beneficial to add In to fix Te as in the present invention.

Next, the operation of the present invention will be described. In the present invention, Te is a base material that exhibits an optical density change before and after recording in a state where other elements are bonded. Ge controls the transition rate between amorphous and crystalline depending on the concentration ratio with Te. That is, in the region where the Ge concentration is low (when only Te and Ge are used, Ge is 50 at
%), It exists stably as an amorphous substance, but when the concentration becomes high, the crystalline substance becomes stable, so that it becomes difficult to amorphize the crystalline substance. The ge concentration of the present invention is 50 at
% Or less, ge contributes to increase the amorphousness of the film. The action of Sn is similar to that of Ge, but the region where Sn and Te increase the amorphousness is narrow, and rather promotes crystallization within the scope of the present invention. That is, Ge and Sn have similar effects on Te, but depending on the concentration ratio with Te, the amorphousness or the crystallinity increases. When the Ge and Sn concentrations are high, the recording film is stable as a crystalline state, so that the transition from the amorphous state to the crystalline state is facilitated, but the reverse is difficult.
Therefore, such materials are write-once materials (W / O materials).
Suitable for However, even such a W / O material can be used as an erasable disc if the laser power is strong and the recording film can be sufficiently melted. Currently, the practically available semiconductor laser has a wavelength of 830 mm and a power of about 30 mΩ, and it is difficult to melt a composition (TeGe, TeSn) close to the stoichiometry of Te, Ge, and Sn. (Melting point is about 800 ° C) The area where Te-Ge-Sn can be recorded and erased is in a very large area of Te (80 at% or more), but the composition of this area has a low transition temperature and is not thermally stable. It is stable, and Te is excessive.
TeGe or TeSn have drawbacks such that the recording film is likely to undergo phase separation. In of the present invention, this excess Te
Has a stabilizing effect as InTe and In ₂ TeIn ₂ IIe ₃ . In and Te in the above alloys, when Te is 50 at% or more, the melting points are 696 ° C. 667 ° C. and 455 ° C., respectively, and the addition of In does not raise the melting point of Te (451 ° C.). Therefore, the recording film added with In can be sufficiently melted with the current semiconductor laser power. In addition, because the excessively thermally unstable Te is bonded as InTex, it forms a thermally stable recording film that is stable over a long period without causing phase separation due to repeated recording and erasing. To do. The amount of In added is the amount necessary to fix the remaining excess Te bonded to Ge and Sn, and the In concentration is also high in the region where the Te concentration is high.

[Explanation of FIG. 1] FIG. 1 shows the main component Te− of the recording film of the present invention.
The Ge-Sn concentration is shown in a triangular coordinate diagram. In the figure, the coordinates of points A, B, C, D and E that define the composition range of the present invention are A (Te ₉₃ Ge ₅ Sn ₂ ), B (Te ₉₃ Ge ₂ Sn ₅ ), C
(Te ₆₈ Ge ₂ Sn ₃₀ ), D (Te ₅₂ Ge ₁₈ Sn ₃₀ ), E (Te ₅₂ Ge ₄₆ S
n ₂ ), the recording film of the present invention is mainly composed of the Te-Ge-Sn system within the range surrounded by this ABCDE.
It is formed by adding 1 to 40 at% of In as a subcomponent. Therefore, the constitution of the recording film of the present invention can be expressed by the following general formula.

(Te ・ xGe ・ ySn ・ z) mIn ・ n However, when Te is more than x + y + z = 100, m + n = 100 line AB, the Ge concentration inevitably decreases,
Amorphization becomes difficult. Also, since the GeSn concentration is low, the transition temperature from amorphous to crystalline is low. When Ge is lower than line BC, the transition temperature is lower as when Te is higher than line AB. Also, the tendency for transformation from crystalline to amorphous is
Better than with more Te. However, from a practical point of view, sufficient phase transition from crystalline to amorphous cannot be obtained. When the Sn concentration is higher than that of the line CD, the addition of Sn promotes crystallization, so that amorphization becomes difficult. Also, the transition temperature from amorphous to crystalline is low, and thermal stability is poor.
When the amount of Te is less than that of the line DE, Te, Ge, and Sn form stable GeTe and SnTe in this region as crystals with a stoichiometry, and thus it is difficult to amorphize. Also, this area is excessive
Since there is almost no Te, the added In concentration is also small. That is, the effect of adding In is small. Therefore, this region is higher than the melting point of the film, making it difficult to amorphize. In a region where Sn is less than the line EA, it is difficult to crystallize because it is amorphous and stable. However, this tendency is on the EA line
It is dominated by the ratio of Te and Ge. The more Te, the easier the crystallization is. The Te concentration around 70at% makes the crystallization the most difficult, and when Te is around 50at%, the crystallization becomes easy again. Become.
The reason is that Te and Ge are more stable compounds as amorphous.
Because it forms GeTe ₂ , it is difficult to crystallize at a Te concentration of around 70%.

For the reasons described above, Te-, which constitutes the main component of the present invention,
The Ge-Sn system is limited to the range surrounded by five points A, B, C, D and E in FIG. That is, within this area
When In is added to Te-Ge-Sn as an auxiliary component in an amount of 1 to 40 at%, information can be recorded and erased practically by utilizing the reversibility between crystalline and amorphous.

[Explanation of FIG. 2] Similar to FIG. 1, FIG. 2 shows the concentration of the main component Te—Gu—Sn of the recording film of the present invention in a triangular coordinate diagram. The portion surrounded by the four points F, G, H, and I is the region defined in claim (2) and contains 10 to 30 at% as a subcomponent.
In is added. Further, the part surrounded by the five points H, J, K, L, and M is the region of claim (3)
15 at% In is added as a subcomponent. As shown in FIG. 4, each point of F to M is within the area of claim (1) surrounded by A, B, C, D and E, and the coordinates of each point are as follows. It is as follows.

F (Te ₉₂ Ge ₅ Sn ₃ ), G (Te ₉₂ Ge ₃ Sn ₅ ) H (Te ₆₈ Ge ₃ Sn ₂₉ ), I (Te ₇₄ Ge ₂₃ Sn ₃ ) J (Te ₇₀ Ge ₁₀ Sn ₂₀ ), K ( Te ₆₂ Ge ₂₉ Sn ₃ ) L (Te ₅₂ Ge ₄₅ Sn ₃ ), M (Te ₅₂ Ge ₁₉ Sn ₂₉ ) FGHI The amorphous to crystalline transition temperature in the region surrounded by four points is 90 to 160. Within ℃, it is lower than the transition temperature (150-220 ℃) of the area surrounded by 5 points of HJKLM. In addition is Te
It has the effect of increasing the crystal transition temperature by 10 to 30 ° C as compared with the case of only -Ge-Sn. Therefore, the addition of In has an effect of increasing the transition temperature showing thermal stability and an advantage of facilitating the amorphization without increasing the melting point of the recording film so much.

In the region surrounded by 5 points of HJKLM, the excess Te is small, so the effect of adding In is smaller than that in the case of FGHI. However, amorphization is easier than that of the Te-Ge-Sn system in which In is not added. HJ
The KLM region has a high transition temperature and is thermally stable.
Since the composition is close to the stoichiometry of e and SnTe, crystallization is easy and amorphization is difficult. However, if the semiconductor laser is made to have high output, amorphization becomes easy. The part surrounded by the point IJK is a region where GeTe _{2 in a} stable crysotropic state exists, and crystallization is difficult.
For the reasons described above, the optimum compositions of the main component Te-Ge-Sn system and the subcomponent In of the present invention are limited.

[Explanation of FIG. 3] FIG. 3 shows a cross section of an optical disk using the recording film of the present invention. 1, 5 are substrates made of transparent materials such as polycarbonate, acrylic resin, glass and polyester, 2 and 4 are protective layers made of various oxides, sulfides and carbides, and 3 is a recording film of the present invention. The protective layers 2 and 4 prevent the heat deterioration of the substrates 1 and 5 due to repeated recording and erasing of the recording film 3 and prevent moisture of the recording film 3. The recording film 3 is formed by vapor deposition, sputtering or the like. The film thickness of the recording film 3 is set to a value that matches the optical characteristics of the protective layers 2 and 4 (a large difference in reflectance between the recorded portion and the unrecorded portion can be obtained).

[Example 1] Te,
Ge, Sn, and In were evaporated from their respective sources. Substrate is ψ
8mm glass plate, vacuum degree 1 × 10 ^-5 Torr, rotation speed 150rp
It was vapor-deposited under m to have a film thickness of 1000Å. The deposition rate from each source was changed to adjust the ratio of the number of Te, Ge, Sn, and In atoms in the recording film. The composition in Table 1 is a value converted from this vapor deposition rate. In addition, when a typical composition was measured by an X-ray microanalyzer (XMA), almost the same quantitative result as the charged value was obtained. With respect to the test pieces A to M and 1 to 16 prepared by the above-mentioned manufacturing method, the transition temperature, the blackening characteristic and the whitening characteristic were evaluated. The results are shown in Table 1. FIG. 4 shows the positions of the test pieces A to M and 1 to 16 in the triangular coordinate diagram.

(Transition temperature) The transition temperature is a starting temperature at which a film in an amorphous state immediately after vapor deposition becomes crystalline due to heat. A device for measuring the transmittance of the film was used for the measurement, and the temperature at which the transmittance started to decrease when the temperature of the test piece was increased by a heater at a temperature rising rate of 1 ° C./sec was taken as the transition temperature. A high transition temperature means that the recording film is thermally stable.

(Blackening characteristics and whitening characteristics) The blackening characteristics indicate the transition rate of transition from amorphous to crystalline, and the whitening characteristics indicate the transition rate of transition from crystalline to amorphous. The measurement was performed by focusing laser light on a recording film on the test piece with a lens and moving the test piece up, down, left and right. Laser beam spot is 45 × 0.4μm, pulse width is 400ns, power density is 1
The wavelength of 0.6 mΩ / μm ² was 900 mm. As for the blackening characteristic, the speed of transformation (amorphous → crystalline) when the test piece is moved relatively slowly is observed, and the speed is sufficiently fast, and the contrast ratio between the unrecorded part and the recorded part is A sufficiently large one was marked with ◎. “X” indicates that the image is not blackened even if it is moved slowly, or that the contrast ratio is small. ○ and △ are located between ◎ and ×. In this qualitative expression, the practical blackening characteristic is ◯ or higher. As for the whitening property, the blackened test piece is quickly moved to make a rapidly cooled state and whitened (crystalline → amorphous). When the whitening state is ◎, the whitening occurs even when the moving speed is relatively slow, and the contrast ratio between the amorphous part and the crystalline part is large.
Indicates that no whitening occurs. ○ and △ are ◎
It is located between x and x.

According to the above-mentioned expression, when both the blackening property and the whitening property are excellent, the results are ◎ and ◎, but as a practical matter, at the same moving speed, neither can be ◎. It is preferable that the blackening characteristics are somewhat excellent, such as ⊚, ◯ or ⊚, Δ. As shown in Table 1, the compositions A to M and 1 to 16 within the region of the present invention surrounded by five points of ABCDE in FIG. It is possible to write and erase information.

Example 2 In this example, Te ₅₀ Ge ₁₀ Sn ₁₀ (point 4 in FIG. 4) is drawn from the region surrounded by FGHI in FIG. 2 and Te ₆₀ Ge ₂₅ Sn is drawn from the region surrounded by HJKLM. ₁₅ (point 12 in FIG. 4) was selected, and the same manufacturing method and evaluation method as in Example 1 were used.
When In was added to the Te-Ge-Sn system, the effect of In concentration on the characteristics was tested. The results are as shown in Table 2, FGHI
In the range of 10 to 35 at%, the In concentration shows good characteristics, and in the HJKLM region, the concentration of In is 1 to 15 at%.
% Indicates that it is usable. No.24 (Pd1at%
The following) are outside the scope of the present invention and do not whiten and do not become a rewritable recording film. No. 30 has a blackening characteristic of X to Δ, but blackening is possible, but practically it is difficult to use.

[Characteristic test No. 1 with optical disk] Polycarbonate resin plate having a thickness of 1.2 mm and a diameter of 200 mm is used for the substrate 1 of FIG.
A ZnS heat-resistant layer is vapor-deposited as a protective layer 2 to a thickness of 900Å, a recording film 3 having a thickness of 1000Å is vapor-deposited thereon by the method of Example 1, and a protective layer 4 of ZnS having a thickness of 1800Å is further deposited thereon. Then, the substrate 5 was disposed in close contact with the substrate 5 and two kinds of optical disks were prepared by using No. 21 and No. 26 in Table 2 for the recording film 3. The recording power and the erasing power are 8 mω and 15 mω and the recording beam is ψ1 for these two types of optical disks.
Recording and erasing tests were carried out in a whitened state and a blackened state, with the erasing laser beam length being about 15 μm (half-value width) and about 15 μm (half-value width). The recording frequency is ZMHZ and the disk peripheral speed is 5 m / s. The results are as follows.

(1) The C / N of the No. 21 disc was 53 bB and the erasing rate was −53 dB, and the C / N of the No. 26 disc was 49 dB and the erasing rate was −46 dB. (2) The decrease in C / N after recording and erasing 100,000 times is -3 dB for No. 21 disc and -2 dB for No. 26 disc.
The reductions in erasure rate were 1 dB and 0.5 dB, respectively.
(3) The No. 21 disc had a C / N decrease of -1 dB and an erasure rate decrease of 1 dB after being left at 80 ° C and 60% RH for 1 month.

[Characteristic Test No. 2 by Optical Disc] With respect to the No. 21 optical disc, GeO ₂ and SiC were used as the heat-resistant protective layer, and the characteristic was tested. The film thickness of the protective layer (2) is 800Å, and the film thickness of the protective layer (4) is 1900Å. Others are the same as those in the characteristic test No.1. As a result, (1) C / N was 52 dB for GeO ₂ and 50 dB for SiC. Also, the erase rate is
They were −47 dB and −48 dB, respectively. (2) Life test (deterioration of characteristics after left for 1 month) is C / N for GeO _2.
Was -3 dB, and that of SiC was -0.8 dB.

[Characteristic test No. 3 by optical disk] The recording film of Example 1 was used.
The optical disk No. 5 was prepared by using the same substrate and method as those used in the characteristic test 1. The heat-resistant protective layer 2 is 860 Å, the recording layer 3 is 300 Å, and the protective layer 4 is 1950 Å. The C / N of this optical disc was 54 dB, the erasing rate was -52 dB, and the C / N reduction after repeating recording and erasing 100,000 times was -2 dB.

[Advantages of the Invention] As described above, the optical information recording member of the present invention, by adding In to the Te-Ge-Sn system and repeating recording and erasing to improve the characteristics, was subjected to a number of experiments to test each component. By defining an effective compounding range, it is possible to sufficiently blacken (erase) and whiten (record) with the current semiconductor laser power, and it is safe against temperature and humidity, and the disadvantages of this type of conventional recording film are eliminated. Has an excellent effect of eliminating.

[Brief description of drawings]

1 is a triangular coordinate diagram showing the composition of the main component of the recording film of the optical information recording member of the present invention. FIG. 2 is the composition of the main component of the recording film of claims (2) and (3). Triangular coordinate diagram FIG. 3: Cross-sectional view of optical information recording member of the present invention FIG. 4: Test pieces A to M and 1 to 16 of Example 1 of the present invention
Diagram showing the position on the triangular coordinate diagram of

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shinji Ohno 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (56) References JP-A-61-31291 (JP, A)

Claims (3)

[Claims] 1. Tellurium (Te), germanium (Ge) and tin (Sn) are contained as main components, and the proportion of these elements is
In the triangular coordinate diagram in which Te, Ge, and Sn are 100 at% vertices, the coordinates (at%) are A (Te ₉₃ Ge ₅ Sn ₂ ), B (Te ₉₃
Ge ₂ Sn ₅ ), C (Te ₆₈ Ge ₂ Sn ₃₀ ), D (Te ₅₂ Ge ₁₈ Sn ₃₀ ),
E (Te ₅₂ Ge ₄₆ Sn ₂ ) has a composition within the range surrounded by the five points as a main component, and the amount of indium (In) added as a sub component to the composition is Te which forms the main component. −Ge−Sn
An optical information recording member having a recording film in which the value of n is 1 to 40 at%, where m is the amount of the system and n (m + n = 100) is the amount of the subcomponent In. 2. The coordinates of Te, Ge, and Sn which are the main components of the first term are F (Te ₉₂ Ge ₅ Sn ₃ ), G (Te ₉₂ Ge ₃ S) in the triangular coordinate diagram.
n ₅ ), H (Te ₆₈ Ge ₃ Sn ₂₃ ), and I (Te ₇₄ Ge ₂₃ Sn ₃ ), within the range surrounded by four points and added as the accessory component.
The amount of In added is such that the value of n is 10 to 35 at%, The optical information recording member according to claim (1). 3. The coordinates of Te, Ge, and Sn which are the main components of the first term are H (Te ₆₈ Ge ₃ Sn ₂₃ ), J (Te ₇₀ Ge ₁₀ Sn) in the triangular coordinate diagram.
₂₀ ), K (Te ₆₅ Ge ₂₃ Sn ₃ ), L (Te ₅₂ Ge ₄₅ Sn ₃ ), M (Te
₅₂ Ge ₁₉ Sn ₂₉ ) within the range surrounded by 5 points, and the value of n is 1 to
The optical information recording member according to claim (1), characterized in that the content is 15 at%.