JPH0675995B2 - 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 and reproducing optical information utilizing light, heat or the like. It is an object of the present invention to provide an optical information recording member capable of optically recording and reproducing at high speed and high density, and having high erasing speed and erasing sensitivity and rewriting information.

As a recording medium used for recording / reproducing high-density information by using a laser beam, a recording medium that uses a state change between tellurium amorphous and crystal is used. These are irradiated with relatively strong and short pulsed light to rapidly cool the irradiation part from a heated state to an amorphous state, and reduce its optical constant,
Recording and erasing are performed by (whitening) or by irradiating a relatively weak and long pulsed light into a crystalline state and increasing the optical constant (blackening). The optical constant is reduced during recording. The erasing direction is used in the erasing direction.

Tellurium is stable as crystals at room temperature and does not exist in the amorphous state. Therefore, an additive is necessary to stably exist in an amosphas state at room temperature, and selenium is known as a typical additive. Selenium exists as a very stable amorphous compound at room temperature, and is completely solid-dissolved with tellurium in any proportion, in any composition range of tellurium and selenium.
A Te-Se thin film that is stable as amorphous is formed.

By the way, this Te-Se thin film is capable of optical recording and erasing of information, but is very stable as amorphous, so when the irradiated part is irradiated with a relatively weak and long pulsed light, the irradiated part is gradually heated and slowly cooled. Since the crystallization speed is slow, it cannot be rewritten. As a rewritable recording thin film, Te-
There is a Se-Sd thin film (eg, Te ₈₀ Se ₁₀ Sb ₁₀ ), but the optical disk of this thin film has a slow erasing speed and insufficient erasing sensitivity, and in addition, there is a difference in optical constant between the black part and the white part. Since it is small, there is a defect that the writing contrast ratio is insufficient.

On the other hand, the present inventors previously composed of a mixture of Te and TeO _2.
We succeeded in improving the crystallization rate by adding palladium to the TeO _X thin film (Japanese Patent Application No. 59-192003).
However, this TeO _X -Pd recording thin film cannot be used as a rewritable recording thin film because it is difficult to whiten it once it is blackened. The present invention contemplates this point,
Te-Se thin film has stability as amorphous and TeO _X
-Pd thin film has both excellent characteristics of high-speed black crystallization and Te-Se thin film and TeO _X -Pd
It is an object of the present invention to provide a rewritable optical information recording member that cannot be expected from a thin film.

[Structure of the Invention] The optical information recording member of the present invention contains tellurium (Te), selenium (Se) and palladium (Pd) as main components, and the proportion of these elements is 100 at% for Te, Se and Pd, respectively. The coordinates (at
%) Was surrounded by four points: A (Te ₈₅ Se ₁₀ Pd ₅ ), B (Te ₄₅ Se ₄₅ Pd ₁₀ ), C (Te ₄₅ Se ₁₅ Pd ₄₀ ), D (Te ₈₅ Se ₅ Pd ₁₀ ). It is characterized by having a recording thin film having a composition within the range. That is, the ratio of the numbers of atoms of Te, Se, and Pd forming the recording thin film of the present invention is A, B in FIG.
It is within the range surrounded by C and D.

The recording thin film of the present invention is extremely stable as amorphous and has a very high blackening sensitivity so that signals can be optically rewritten. It is considered that the action of Se in this Te-Se-Pd recording thin film prevents the Te or Te-Pd compound from crystallizing in the amorphous state and stabilizes the amorphous state (signal recording bit). On the other hand, Pd is considered to act as a crystal nucleus that forms a Te-Pd compound during erasing and promotes crystal growth. Therefore, it is considered that by including Se, the recording thin film in a stable amorphous state has sufficient erasing speed and erasing sensitivity by including Pd. Furthermore, Te-Se-Pd thin film, compared to Te-Se thin film,
Since the light transmittance is low, the light absorption rate of the recording thin film is good and the sensitivity is high. Further, since crystallization is performed at high speed and sufficiently, the difference in optical constant between amorphous and crystal becomes large, and the contrast ratio at the time of signal writing becomes large, so that large C / N can be obtained.

Next, the ratio of the numbers of Te, Se, and Pd atoms forming the recording thin film of the present invention will be described. Of the constituent elements, Te becomes an morphous state by heating and rapid cooling by laser irradiation, and becomes a crystalline state by heat removal and cooling. That is, this Te-
In the Se-Pd thin film, signals are recorded and erased mainly by the change in reflectance due to the phase transformation of Te, but the change in reflectance is small in the region where the content of Te is small. It was confirmed that, in the region where the content of Te was less than Te45 at% (BC line in Fig. 1), the crystallization gradually became difficult when the phase transformation between amorphous and crystal was repeated. Te itself has strong crystallinity at room temperature, and Te85 at% (Fig. 1, AD line)
In the above Te-rich region, the amorphous part (recording bit) is likely to crystallize, and there is a problem in saving the recorded signal.

Se acts as a solid solution with Te in any ratio and enters into the crystal of Te to prevent the crystal of Te from increasing and to keep the recording thin film in an amorphous state, while Pd acts as Te. When Te-Pd crystallizes from amorphous
Alternatively, it is thought that it acts like a kind of crystal nucleus by making some kind of Se-Pd compound, and promotes the crystallization of Te (erasing the recording signal) at high speed and high sensitivity by laser irradiation. Has the effect of Therefore, Se and Pd act in opposite ways in the recording thin film, so the relative proportion of these contents is important.

In the region where the Pd content is less than the AB line in Fig. 1, the action of Pd is too small compared to the action of Se, and the whitening sensitivity (recording sensitivity) is sufficiently obtained, but the blackening sensitivity (erasing sensitivity) is insufficient. . Pd
Fig. 1 In the region where CD content is higher than the CD line, the action of Se is Pd
It is too small compared to the action of, and the formation of amorphous is insufficient.
In addition, since the amorphous portion is easily crystallized,
The reliability of saving recorded signals is poor. The recording thin film of the present invention provides sufficient recording, erasing sensitivity, storage stability of recorded signals, and high
The relative proportion of Te, Se, and Pd is Te = 45 to 85, which has N and exhibits stable characteristics in repeated recording and erasing of signals.
At%, Se = 5 to 45 at%, Pd = 5 to 40 at%, and these numbers are clear from the data of Examples 1 to 3 described later. As shown in the figure, the area is surrounded by A, B, C, and D. In addition, A,
The coordinates (at%) of B, C, and D points are as follows.

A (Te ₈₅ Se ₁₀ Pd ₅ ), B (Te ₄₅ Se ₄₅ Pd ₁₀ ), C (Te ₄₅ Se ₁₅ Pd ₄₀ ), D (Te ₈₅ Se ₅ Pd ₁₀ ) [Additive] The recording thin film of the present invention is an additive. By blending, the characteristics can be further improved. The embodiment of claim (2) is particularly effective when used at a high temperature when a small amount of Ge is added. One of the causes of deterioration of the recording thin film is that when Te in an amorphous state is left at high temperature, it may gradually crystallize (whitening parts gradually become black), but Ge is amorphous in the recording thin film. It is considered that the converted Te has the effect of increasing the transition start temperature at which crystallization starts. Even if the addition amount of Ge is about 2 at%, the effect is sufficiently recognized. If the amount added exceeds 15 at%, the transition start temperature becomes too high and the erasing sensitivity decreases, so 15 at% is the limit.

The embodiment of claim (3) is a case of adding at least one of the elements selected from Sn, Sb, Bi and In. Increasing the Pd content to improve the blackening sensitivity of the Te-Se-Pd recording thin film reduces the whitening sensitivity, but adding a small amount of Sn, Sb, Bi, In, etc. does not decrease the whitening sensitivity. The blackening sensitivity can be improved, and the addition amount is appropriately 5 to 30 at%. The addition of Sn, Sb, Bi, In, etc. is particularly effective in the region where the content of Pd is small in terms of improving the blackening sensitivity, and considering that Pd is an expensive element, in practice, It can be said that it is an advantageous additive substance.

The optical information recording member of the present invention, the method for producing the same, and the method for evaluating the characteristics thereof will be described with reference to FIGS. 2 and 3. FIG. 2 is a sectional view of the optical information recording member of the present invention.
Is a substrate made of transparent resin such as PMMA, polycarbonate, vinyl chloride, polyester, or glass, and 2 is a recording thin film. The recording thin film 2 is formed on the substrate 1 by vapor deposition, sputtering, etc., and its film composition is determined by Auger electron spectroscopy, inductively coupled high frequency plasma emission spectrometry, X-ray microanalysis, etc.

An electron beam evaporator capable of three-source evaporation was used to form the recording thin film, and Te, Se, and Pd were deposited on each acrylic resin substrate (10 × 20 × 1.2 m / m) rotating at 150 rpm from each source. ×
Deposition was performed under a vacuum of 10 ^-5 Torr or less. The thickness of the recording thin film was about 1200Å. The deposition rate from each source was varied to adjust the ratio of the numbers of Te, Se, and Pd atoms in the recording thin film.

A third method for evaluating the blackening characteristic (erasing characteristic) and the whitening characteristic (recording characteristic) of a test piece prepared by the above method
The figure will be described. Wavelength 830nm emitted from semiconductor laser 3
Is converted into pseudo parallel light 5 by the first lens 4 and
After being shaped into a round shape by the lens 6, it becomes parallel light again by the third lens 7, and is focused by the fourth lens 9 through the half mirror 8 on the spot 11 with a wavelength limit of about 0.8 μm on the test piece 10. Is recorded. For detection of the signal, the reflected light from the test piece 10 is received via the half mirror 8 and the fifth lens 12
Through the light sensitive diode 13. By thus modulating the semiconductor laser and irradiating the test piece with various pulsed laser beams having different irradiation powers and irradiation times, the blackening characteristic and the whitening characteristic can be known.

To evaluate the blackening characteristics, the irradiation power is relatively small, for example
We adopted a method of fixing the power density to about 1 mw / μm ² and changing the irradiation time to measure the irradiation time at the start of blackening. To evaluate the whitening characteristics, blacken the recording material in advance,
A method of fixing the irradiation time to, for example, about 50 nsec and measuring the irradiation light power required to start whitening was adopted. Considering the practical output of a semiconductor laser, if the irradiation time for blackening start is about 3 μsec or less and the irradiation power for whitening start is about 10 mw / μm ² or less in the above evaluation method, the recording thin film is practically used. It is thought that it can be used for a typical optical disk. The results of evaluating the prepared test pieces using the above evaluation method are as follows.

[Example 1] As an evaluation material composition, the atomic ratio of Se and Pd was 5
The composition was controlled so that it became 0:50, and at the same time, the Se ₅₀ Pd
Multiple test pieces were prepared by changing the ratio of ₅₀ and Te.

FIG. 4 (a) shows the change in the irradiation time required to start blackening when the Te content was changed while maintaining Se ₅₀ Pd ₅₀ and irradiation was performed with a power of 1 mw / μm ² . From this figure, it can be seen that the irradiation time required for the start of blackening becomes longer when the content of Te is small, but it is considered to be a sufficiently practical time within the range of this example. It was also observed that the amount of change in reflectance decreased as the Te content decreased.
This shows that a large C / N cannot be obtained, but this is not a problem in practical use. Further, in a region where the Te content is less than 45 at%, for example, in a thin film of Te ₄₀ Se ₃₀ Pd ₃₀ , after blackening once, the whitened part is not blackened sufficiently as much as the first blackened state even if it is blackened again. It was confirmed. This is thought to be due to some phase separation of the recording thin film in the laser-irradiated portion, and shows that the recording and erasing characteristics gradually change when signal recording and erasing are repeated. There's a problem.

Fig. 4 (b) shows the difference in irradiation power required to start whitening when the irradiation time is changed to 50 nsec and the irradiation time is changed to 50 nsec, and the blackened area is irradiated with 15 msec with 1 mw / μm ² power. Is shown. From now on, Te against Se ₅₀ Pd ₅₀
It can be seen that the irradiation power required to start the whitening increases as the ratio of B increases, but it is considered that the irradiation power is sufficiently practical within the range of the present embodiment. But,
It was confirmed that in the region where the Te content exceeds 85 at%, the whitened portion (amorphous portion) cannot stably exist for a long period of time at room temperature and gradually becomes black (crystallizes). This indicates that the recording bit of the signal disappears spontaneously, which is a practical problem.

From the above, a recording thin film having a composition represented by (Se ₅₀ Pd ₅₀ ) 100−x Te _X (at% display) has an x value of 45 ≦ x ≦ 85 at%
It can be seen that the recording thin film having excellent recording and erasing characteristics can be obtained by selecting.

[Example 2] The composition of the material to be evaluated was controlled so that the atomic ratio of Te and (Se + Pd) was 80:20.
A plurality of test pieces were prepared by changing the ratio of Pd and Pd.

Fig. 5 (a) shows that Te ₈₀ Se _20-X Pd _X , 0 ≤ x ≤ 20 (at% display), the value of x was changed to start blackening when irradiation was performed with a power of 1 mw / μm ^2. The change of irradiation time required is shown. It can be seen from the figure that the irradiation time required to start the blackening becomes shorter as the value of x increases (the amount of Pd added increases). If the value of x is about 6 at% or more, the practical blackening rate It is revealed that can be obtained.

Fig. 5 (b) shows the difference in the irradiation power required to start whitening when the irradiation time is changed to 50 nsec and the irradiation time is changed to 50 nsec and the blackened area is irradiated with 15 msec with a power of 1 mw / μm ^2. Is shown. From now on Te ₈₀ Se _20-X Pd _X
It can be seen that the irradiation power required for the start of whitening increases as the value of x increases. However, if the value of x is about 14 at% or less, it is considered that the irradiation power has no practical problem.
In addition, it was confirmed that in the recording thin film having a composition of x = 17 at%, that is, Te ₈₀ Se ₃ Pd ₁₇ , the whitened portion gradually blackened when left at room temperature for a long period of time. It turns out that it is not practical.

From the above, the recording thin film having the composition represented by Te ₈₀ Se _20-X Pd _X is selected by setting the value of x to 6 ≦ x ≦ 14 at%.
It was clarified that both recording and erasing show excellent characteristics.

[Example 3] The composition of the material to be evaluated was controlled so that the atomic ratio of Te and (Se + Pd) was 50:50.
A plurality of test pieces were prepared by changing the ratio of Pd and Pd.

Fig. 6 (a) shows that Te ₅₀ Se _50-X Pd _X , 0 ≤ x ≤ 50 (at% display), the value of x is changed, and it is necessary to start blackening when irradiating with a power of 1 mw / μm ^2. The change in irradiation time is shown. It can be seen from the figure that the irradiation time required to start blackening becomes shorter as the value of x increases (the amount of Pd added increases), and if the value of x is 10 at% or more, the practical blackening rate It is revealed that can be obtained.

FIG. 6 (b) shows the irradiation power required to start whitening when the irradiation time is changed to 50 nsec and the irradiation time is changed to 50 nsec for a sufficiently blackened area by irradiation with a power of 1 mw / μm ² for example. Shows the difference. From now on Te ₅₀ Se _50-X Pd
_It can be seen that the irradiation power required to start whitening increases as the value of x increases in X, but it is considered that there is no practical problem if the value of x is 35 at% or less. From the above,
The recording thin film having a composition represented by Te ₅₀ Se _50-X Pd _X is
It can be seen that by setting the value of x to 10 ≦ x ≦ 35 at%, a recording thin film excellent in recording and erasing can be obtained.

From Examples 1 to 3 above, a recording thin film having Te, Se, and Pd as constituent elements and having a ratio of the number of atoms of each element within the range surrounded by A, B, C, and D in FIG. It can be seen that the optical information recording member has good characteristics and erasing characteristics.

[Example 4] The composition of the material to be evaluated was controlled so that the atomic ratio of Te, Se and Pd was 70:15:15.
A plurality of test pieces with different amounts of Ge added to Te ₇₀ Se ₁₅ Pd ₁₅ were prepared. This test piece was prepared by using an electron beam evaporation machine capable of four-source evaporation to evaporate Te, Se, Pd, and Ge from each source. Other vapor deposition conditions are the same as those in the above-mentioned embodiment.

This test piece was left in a constant temperature bath at 60 ° C., and the heat resistance was determined by measuring the change in transmittance with respect to light having a wavelength of 830 nm. FIG. 7 (a) shows the result. It can be seen from the figure that the rate of decrease in transmittance is slowed by adding Ge to Te ₇₀ Se ₁₅ Pd ₁₅ . The decrease in transmittance is
This means that the recording thin film in the amorphous state gradually crystallizes when left at high temperature, and the addition of Ge shows an increase in the crystallization temperature. That is, by adding Ge, the recording bit of the signal (amorphous state)
The storage characteristics of can be improved. This effect is observed even when the amount of Ge added is 2 at% or less, but it can be seen that the larger the amount added, the higher the heat resistance.

FIG. 7 (b) shows the change in the time required for the initiation of blackening when the amount of Ge added was increased while maintaining Te ₇₀ Se ₁₅ Pd ₁₅ and irradiation was performed at 1 mw / μm ² . From the figure, it can be seen that the irradiation time for the start of blackening gradually increases as the amount of Ge added increases. This is because the crystallization temperature of the recording thin film in the amorphous state increased due to the addition of Ge. Although the addition of Ge causes a decrease in blackening sensitivity,
From the figure, it can be seen that there is no problem if the added amount is 15 at% or less.

FIG. 7 (c) shows the irradiation power required to start whitening when irradiation is performed for 15 μsec with a power of 1 mw / μm ² and sufficiently blackened, and the irradiation power is changed with the irradiation time set to 50 nsec. Shows changes. From now on Te ₇₀ Se ₁₅ Pd ₁₅
Although the irradiation power required for the initiation of whitening gradually increases by adding Ge to Al, there is practically no problem within the range of the added amount (25 at% or less) in this example.

From the above, the addition of Ge is effective in improving the heat resistance of the Te-Se-Pd recording thin film, and especially when the addition amount of Ge is 15 at% or less, the heat resistance while maintaining both the blackening property and the whitening property is good. It turns out that can be improved.

[Example 5] The composition of the material to be evaluated was controlled so that the atomic ratio of Te, Se, and Pd was 75:15:10.
_A plurality of test pieces were prepared by changing the ratio of ₇₅ Se ₁₅ Pd ₁₀ and one element selected from Sn, Sb, Bi and In. In this case, the method of preparing the test piece is to use an electron beam vapor deposition machine capable of four-source vapor deposition, and use Te, Se, Pd and Sn from each source.
One element selected from Sb, Bi and In was deposited. Other vapor deposition conditions are the same as those in the above-mentioned embodiment.

FIG. 8 (a) shows the results obtained by adding Sn to Te ₇₅ Se ₁₅ Pd ₁₀ and
Figure (a) shows the case when Sb was added, Figure 10 (a) was the case where Bi was added, and Figure 11 (a) was the case when In was added.
The changes in the irradiation time required to start blackening when irradiated with a power of 1 mw / μm ² are shown. From these figures,
Irrespective of the addition of Sn, Sb, Bi, or In, it was found that the irradiation time required to start the blackening was shortened.
It can be seen that the effect is large when it is added in an amount of not less than%.

FIG. 8 (b), FIG. 9 (b), FIG. 10 (b), and FIG. 11 (b) each show a power of, for example, 1 mw / μm ² and 15 μse.
c shows the change in the irradiation power required to start the whitening when the irradiation time is changed to 50 nsec and the irradiation power is changed to the sufficiently blackened area. From these figures,
It can be seen that the irradiation power required for the initiation of whitening increases even if any of Sn, Sb, Bi and In is added to Te ₇₅ Se ₁₅ Pd ₁₀ . However, no matter which element Sn, Sb, Bi or In is added, it is considered that the irradiation power is sufficiently practical if the addition amount is 30 at% or less.

From the above, by adding 5 to 30 at% of the element selected from Sn, Sb, Bi and In to the Te-Se-Pd recording thin film, the blackening characteristic is improved while keeping the whitening characteristic in a practical range. You can see what you can do.

Example 6 A 1.2 t × 200 mmφ acrylic resin plate was used as a substrate, and Te ₇₅ Se ₂₅ thin film and Te ₇₀ Se ₁₅ were used as recording thin films.
Two types of optical disks with a Pd ₁₅ thin film formed were prototyped and a comparative test of signal recording and erasing was performed. The method of forming each recording thin film is the same as that of the above-mentioned embodiment.

Using these two types of optical disc, the recording power, respectively erasing power 8 mW, at a 18 mW, the erase laser beam length was line summer whitening recording and blackening eliminated as about 1 × 15 [mu] m in the half width, Te ₇₀ Se A disk with a ₁₅ Pd ₁₅ thin film has a single frequency of 2 MHz, a disk peripheral speed of 7 m / s, and a C / N of 55 dB. Almost no deterioration of C / N is seen even after recording and erasing 100,000 times. Nakatsuta. On the other hand, the disk having the Te ₇₅ Se ₂₅ thin film does not turn black enough even when irradiated with the erase beam,
Therefore, even if the signal was recorded, only C / N of about 30 dB was obtained, and since the blackening speed was slow when the recorded signal was erased, it was not possible to erase it sufficiently by irradiating the erase beam for one turn.

[Advantages of the Invention] As described above, the optical information recording member of the present invention has a signal recording bit (amorphous) by adding Pd to a Te-Se thin film that is stable as an amorphous.
The erasing sensitivity is improved without impairing the stability of, and the ratio of the proper number of atoms of Te, Se, and Pd is shown by A, B, C, and D in Fig. 1 by many experiments. Stipulated in the range. Further, by adding Ge, heat resistance is improved, and by adding an element selected from Sn, Sb, In, and Bi, erasing characteristics are improved without significantly lowering recording characteristics. ing. Therefore, it has an excellent effect of providing a practically excellent optical disk by eliminating the drawbacks of the conventional optical information recording thin film mainly composed of Te-Se and capable of rewriting signals.

[Brief description of drawings]

1 is a triangular coordinate diagram showing the composition of a recording thin film of the present invention. FIG. 2 is a sectional view of an optical information recording member of the present invention. FIG. 3 is a schematic diagram of an optical system of a characteristic evaluation device for an optical information recording member of the present invention. Fig. 4: Graph showing (a) blackening characteristics and (b) whitening characteristics of the recording thin film (Se ₅₀ Pd ₅₀ ) _100-X Tex of the present invention. Fig. 5: Recording thin film of the present invention (Te ₈₀ Se _{20- X} Pdx) (a)
Graph showing blackening characteristics, (b) whitening characteristics FIG. 6: (a) of recording thin film (Te ₅₀ Se _50-X Pdx) of the present invention
Graph showing blackening characteristics, (b) whitening characteristics FIG. 7: (a) heat resistance characteristics, (b) blackening characteristics, (c) of the recording thin film (Te ₇₀ Se ₁₅ Pd ₁₅ ) _100-X Gex of the present invention Graph showing whitening characteristics Fig. 8: Graph showing (a) blackening characteristics and (b) whitening characteristics of recording thin film (Te ₇₅ Se ₁₅ Pd ₁₀ ) _100-X Snx of the present invention Fig. 9: Recording of the present invention Graph showing (a) blackening characteristics and (b) whitening characteristics of thin film (Te ₇₅ Se ₁₅ Pd ₁₀ ) _100-X Sbx. Fig. 10: Recording thin film (Te ₇₅ Se ₁₅ Pd ₁₀ ) _100-X Bix of the present invention Graphs showing (a) blackening characteristics and (b) whitening characteristics of FIG. 11: (a) blackening characteristics, (b) whitening characteristics of the recording thin film (Te ₇₅ Se ₁₅ Pd ₁₀ ) _100-X Inx of the present invention Showing the graph

Claims (3)

[Claims] 1. Tellurium (Te), selenium (Se), and palladium (Pd) are contained as main components, and the proportions of these elements are coordinated in a triangular coordinate diagram having Te, Se, and Pd as 100 at% vertices, respectively. (At%) is surrounded by four points: A (Te ₈₅ Se ₁₀ Pd ₅ ), B (Te ₄₅ Se ₄₅ Pd ₁₀ ), C (Te ₄₅ Se ₁₅ Pd ₄₀ ), and D (Te ₈₅ Se ₅ Pd ₁₀ ). An optical information recording member having a recording thin film having a composition within the range. 2. The invention as set forth in claim 1, wherein the additive substance contains germanium in an amount of 15 at% or less.
Optical information recording member. 3. An additive substance containing at least one or more elements selected from tin, antimony, bismuth and indium, and the total amount of addition is 5 to 30 at%. The optical information recording member in the range (1).