JPH01138634A - Information recording medium - Google Patents

Abstract

PURPOSE:To obtain an information recording medium having excellent wet heat resistance and high durability and reliability by incorporating gallium, antimony, germanium, tellurium, and selenium as essential components into the elements forming thin films on a substrate. CONSTITUTION:The substrate 5 is mounted to a substrate stage 7 provided oppositely to evaporation boats 1a, 1b, 1c for resistance heating. A GaSb alloy is set in the boat 1a, a TeGe alloy in 1b and an Se alloy in 1c. The thin films are formed on the substrate 5 through a slit plate 2 having the slits corresponding to the boats when a shutter 3 is opened and the boats 1a-1c are independently heated. The rates of evaporation are the rates set by film thickness sensors 4a-4c. The recording films having uniform quality are formed when the substrate 5 is rotated by a driving device 6. The recording medium having the excellent wet heat resistance and the high durability and reliability is obtd. by forming the thin films in such a manner.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an information recording medium, and is particularly applicable to an optical disk device that records information by irradiation with an energy beam such as a laser beam or an electron beam. The invention relates to information recording media.

[Prior Art] Various recording methods have been proposed for optical information recording media, but in particular, there are methods that address differences in optical properties due to phase changes of the medium, such as differences in reflectance between crystalline and amorphous states. In the case of the method used for recording, there are few advantages such as not requiring any change in the shape of the medium thin film itself and no problem of contamination due to evaporated matter. Furthermore, since it is possible to improve durability by forming a protective film, the requirements for the stability of the film itself are not so strict, and there is an advantage that a wide range of materials can be selected. Te low oxide thin film, “1eGei film (JP-A-60-1
57894> etc. are known.

Among these materials, TeQe in particular can be easily formed into a thin film using well-known thin film forming techniques such as vapor deposition and sputtering, and the reflectance of TeQe in the amorphous and crystalline states before and after phase change is This has the advantage that the difference (recording margin) can be relatively large.

In addition to improving the characteristics of the medium itself, another way to obtain a high-quality reproduction signal is to increase the reflectance of the crystallized portion or lower the reflectance of the amorphous portion.
Alternatively, various methods have been considered, such as making the reflectance of the crystallized portion lower than that of the amorphous portion. As an example, the light reflected from the front and back surfaces of the recording medium is 1/2 each.
Adjust the film thickness of the medium so that there is an optical path difference equal to the wavelength, and use the effect of film thickness interference to cancel the reflected light at the amorphous part and lower the reflectance. A method is known in which the difference in reflectance change (recording margin) is amplified by utilizing the fact that the interference conditions of a film are shifted due to a change in the complex refractive index.

[Problems to be solved by the invention] However, even with TeQe, when a thin film was actually formed on a disk-shaped substrate and the recording characteristics and durability under high temperature and high humidity were evaluated, the following results were found. It became clear that there were problems.

That is, (1) the C/N (ratio of carrier signal to noise), which indicates the quality of the reproduced signal, is not sufficient, and (2) the recording margin, which indicates the size of the reproduced signal, is also not sufficient. When conducting an accelerated test for humidity and heat resistance using 60'C190%Rl-1, the characteristics of the thin film itself deteriorated significantly, so there was a limit to the improvement in durability with a normal protective layer, and only partial durability was observed. There were problems such as it was not so easy to ensure performance and reliability.

Regarding the above-mentioned problems (1) and (2), the present inventors have previously proposed a solution to problems (3e) in Japanese Patent Application No.
proposed adding Qa3b to the film, and found that good recording characteristics could be obtained.In this case, it was also found that the durability of the thin film itself was improved to a certain extent compared to the TeGe film, but the moisture and heat resistance As for the characteristics, no sufficient improvement effect has yet been observed, and further improvements have been desired in terms of improved durability and reliability.

Therefore, the object of the present invention is to
It is an object of the present invention to provide an information recording medium that maintains the excellent properties of the recording medium while significantly improving its moisture and heat resistance in particular and has excellent durability and reliability.

(Means for Solving the Problems) An object of the present invention is to form a thin film on a substrate, and to improve the optical properties of the thin film using heat generated directly or indirectly by irradiating the film with an energy beam. In an information recording medium that records information by changing characteristics, the elements constituting the thin film include gallium, antimony, germanium,
This is achieved by an information recording medium characterized by containing tellurium and selenium as main components.

The recording thin film in the present invention includes gallium (Ga), antimony (Sb), germanium (Ge), and tellurium (Te).
and those containing selenium (Se) as a main constituent element.

Although its composition is not particularly limited, in order to effectively exhibit the effects of the present invention, it is preferable to have the following composition.

That is, the proportion of selenium in all the thin film components is 5 to 22% in atomic %, and the composition of each component except selenium is as follows.
General formula % Formula % X: Number of atoms of (Ga and Sb) in the thin film %y: (Ga and s
b> Number of atoms of Ga in %z: (Te and Ge) When expressed as the number of atoms of Te in %, the ranges of x, y, and z are respectively,
It is preferable that 2≦X≦50.2≦y≦70.30≦7≦70.

If the Se content is small outside of this range, it is difficult to achieve the effect of improving heat and humidity resistance, while if it is too large, the light absorption rate of the medium may decrease or the recording margin may decrease, which is preferable. do not have.

Furthermore, the range of X, Y, and Z is important for expressing the excellent characteristics of the QGe-Qa3b recording medium, and outside this range, it becomes difficult to express the excellent effects of containing Ga and Sb. In addition, it becomes difficult to form a thin film with a stable amorphous structure, and it becomes difficult to form a thin film with an appropriate transition temperature, which is undesirable.

In order to more preferably express the effects of the present invention,
The range of X is more preferably 3≦X≦30, and even more preferably the range of 5≦X≦25. Further, for y and 2, the ranges of 5≦y≦60 and 40≦2≦60 are more preferable.

The thickness of the recording film is not particularly limited, but when actively utilizing the film thickness interference effect as described above,
By setting it in the range of 80 to 120 nm, it is possible to improve the recording margin.

However, it is clear that the recording medium can be used with other film thicknesses as well, as the recording medium of the present invention is characterized by utilizing changes in the optical properties of the medium itself. .

Substrates used in the present invention include polymer resins such as polymethyl methacrylate resin, polycarbonate resin, epoxy resin, polyolefin resin, polyvinyl chloride resin, polyester resin, and styrene resin, glass plates, and in some cases AQ A metal plate such as the like can also be used.

In addition, in order to effectively express the original characteristics of the recording medium of the present invention, a protective layer can be provided between the substrate and the recording layer or on the recording layer.The protective layer can be formed by vapor deposition, sputtering, etc. ,
An inorganic film such as 3i02 or an ultraviolet curing film may be provided using a method such as a spin cord, or a resin such as epoxy or polycarbonate, film, glass, etc. may be laminated using an adhesive or the like. Alternatively, a method such as lamination may be used.

The effects of such a protective layer include extending the life of the recording medium by improving durability and resistance to moisture absorption, and eliminating the need to bond a disk together when a single disk is used. Furthermore, when exposing a recording medium to high temperatures using heating means such as energy beams or heaters, it is possible to prevent deformation due to delamination or swelling of the recording film from the substrate, and to prevent adverse effects such as loss of the recording medium due to melting, evaporation, diffusion, etc. Effects such as prevention can be expected.

Naturally, even if materials other than those exemplified as the substrate or protective film are used, the protective film is omitted, or a configuration other than the configuration mentioned in the present invention is adopted, the optical characteristics of the recording thin film itself will essentially remain. It goes without saying that the use of such changes does not depart from the spirit of the present invention.

〔Production method〕

Although there are various methods for manufacturing the recording medium of the present invention, the vacuum evaporation method and the Yasbatta method described below are effective as simple and easy methods.

Figures 1 and 2 show an example of a manufacturing apparatus using the vacuum evaporation method, and its basic structure is 1 (1a, 1b, 1C1
1d) is an evaporation boat for resistance heating, and 2 is a slit corresponding to the boat (2'a, 2'b, 2'c,
2'd) is provided with a slit plate, 3 is a shutter, and 4 is a shutter.
(4a, 4b, 4C) are film thickness sensors for monitoring the amount of evaporation. The vacuum chamber 8 in which these devices are installed also has a stage 7 on which the substrate 5 is attached, and is set to be rotatable by a drive device 6 such as a motor. The steam from each evaporation boat is set to reach the substrate through each slit, and can be controlled independently.

In order to produce the recording medium of the present invention using such an apparatus, for example, the simplest method is to use (3a3b alloy for 1a, TeG for 1b).
Se is set in e alloy, 1C, and each independently,
A preset amount may be evaporated based on the film thickness sensors 4a, 4b14C.

The substrate is rotated by the drive device 6 in a range of 60 to 600 rpm. According to the results of studies conducted by the present inventors, the membrane produced by such a method is sufficiently homogeneous and fully satisfies the purpose of the present invention. Of course, as another method, for example, Te may be set for 1a, Qe for 1b, GaSb for ic, and Se for 1d.

Next, regarding the sputtering method, a method for producing a recording film using the magnetron sputtering method illustrated in FIG. 3 will be described. The basic structure consists of a sputter target 10, a substrate holder 7 and a film thickness sensor 4 arranged opposite to the sputter target 10. When the shutter 3 is opened after sputter discharge starts, the substrate 5
The film formation on the substrate 5 is started, and the amount of film deposited on the substrate 5 is monitored by the film thickness sensor 4 as in the case of the vapor deposition method. A sufficiently homogeneous recording film can be produced by rotating the substrate holder at 10 to 300 rpm. In order to produce a recording thin film satisfying the composition of the present invention, for example, alloy pellets such as GaSb and Se may be placed on a TeGe target to have a predetermined composition and co-sputtered, or (GaSb, Se, etc.) may be co-sputtered.
, Sb, Te, Ge', and 3e), and its composition may be adjusted by taking into account the sputtering rate of each element so that the thin film after sputtering has a predetermined composition.

As the sputtering gas, an inert gas such as argon can be used, and the sputtering can be carried out under conditions of an RF output of 100 to 200 W and a degree of vacuum during sputtering of about 6 to 4×10'Pa.

Naturally, appropriate sputtering conditions are not constant depending on the apparatus, and it goes without saying that a recording medium may be produced under conditions other than these conditions.

The film thickness of the recording medium produced by these methods is not particularly limited, but if it is set in the range of 80 to 120 nm, a large recording margin can be obtained due to the film thickness interference effect, and the characteristics of the recording medium of the present invention can be best utilized. Can be done.

Other methods for producing the rough record film include thin film production techniques such as electron beam evaporation.

[Measurement method] The evaluation method used in the examples of the present invention will be explained.

■As described in the transition temperature manufacturing method, a pair of electrodes is formed on the record film fabricated on the glass substrate, and one end of the electrode is set to 30Ω.
Connect the resistors in series. 5■ on both ends of the remaining electrode and resistor
A constant voltage is applied, the voltage across the resistor is measured with a voltmeter, the applied voltage and current of the thin film are determined from this, and the resistance value is calculated. Next, use a heating furnace to uniformly heat the entire board, and measure the resistance while increasing the temperature using a temperature controller at a rate of approximately 0°C/min to find the point at which the resistance changes from high to low. , the temperature at that time was taken as the transition temperature.

■ Recording margin The reflectance of the amorphous substrate side of the recording thin film fabricated on the glass substrate and the reflectance of the crystalline substrate side were measured using a spectrophotometer ((
The difference in reflectance at 830 nm, which is the wavelength of the semiconductor laser used for recording, was determined and used as the recording margin.

(2) Composition A recording thin film prepared on a glass substrate was dissolved with aqua regia, nitric acid, etc. and separated from the substrate. The content of each element in this solution was determined by high-frequency inductively coupled plasma (ICP) emission spectrometry (Seiko Electronics Co., Ltd. SPS-"l 100 model), and the composition ratio (atomic %) was calculated.

■ Moisture and heat resistance evaluation Sample with only recording thin film formed on glass substrate Wavelength 60
The transmittance at 0 nm is measured using the spectrophotometer described above. Next, the sample was left in a moist heat oven (PH-1G type, manufactured by Tabai Co., Ltd.) set at a temperature of 60°C and a humidity of 90%, and the change in transmittance after being left (if the transmittance changed by 3% or more) If there was a change, the evaluation was made based on the presence or absence of a change (in the case of a change) and the length of time it was allowed to stand.

[Applications] The recording medium of the present invention thus obtained can be used particularly for optical disks, optical tapes, optical cards, optical floppy disks,
It has favorable characteristics as an information recording medium such as microfiche and laser 00M. Therefore, it can be used not only for these applications but also for all applications that utilize differences in optical properties for recording. In addition, in the above explanation, we mainly explained the record of the transition from amorphous to crystal, but the record is that the record is crystallized in advance, then heated to above the melting point by an energy beam, and returned to the amorphous state in the melting/quenching process. It can also be used in methods. Furthermore,
It can also be applied to the purpose of repeatedly recording and erasing by combining crystallization and melting/quenching processes.

[Example] The present invention will be further explained in detail based on examples.

Examples 1-5. Comparative Examples 1-2 By the vacuum evaporation method and sputtering method described in the manufacturing method,
On a glass substrate (1.2 mm thick), the film thickness is 95-11 mm.
A recording thin film was formed to have a thickness in the range of 0.05n.

That is, Examples 1 to 4 and Comparative Examples 1 to 2 were each performed by a vacuum evaporation method, using the vacuum evaporation apparatus illustrated in FIG. Te (3e alloy) and Se were charged into a boat MIC, and the amount of evaporation from each boat was adjusted using film thickness monitors 4a to 4C.
The tube was rotated to ensure that the evaporates from the three ports were evenly mixed. Comparative Example 1 is an example of a two-source co-evaporated film of TcGe and GaSb that does not contain only Se.
Comparative Example 2 shows an example using only He (3e alloy).

Table 1 shows the composition and evaluation results of the recording thin film.

In addition, Example 5 used the sputtering apparatus illustrated in FIG. 3, in which a TeGe alloy target was combined as the sputter target I, and Ga3b alloy with a diameter of 20 mm and each pellet of 3b and 3e were combined thereon. It is made by sputtering using materials. The sputtering conditions are 5.8xlO'Pa using argon gas as sputtering gas.
The substrate was rotated at about 4 rpm to make the composition uniform, and the amount of sputtering was adjusted using a film thickness monitor. The composition and evaluation results are shown in Table 1.

As is clear from Table 1, Comparative Example 2 with a transition temperature of 170°C
In Examples 1 to 5, the transition temperature can be easily controlled by adjusting the amount of 3e added, and the transition temperature (i.e., crystallization temperature) is lower than in Comparative Example 3. Since it can be set quite high, crystallization in a standing state can be suppressed and the stability and storage life of the medium can be significantly improved. Furthermore, the upper limit of the temperature rise of the recording layer due to the heat of the reproduction light can be set high, which improves the storage stability and stability of recordings.
It is possible to increase the reproduction light power without 0.
For example, when using the film thickness interference effect, it is easy to compensate for the decrease in reflectance of an amorphous recording film by increasing the reproduction light power, and to secure the amount of reflected light necessary for precise tracking and focusing control. becomes.

Furthermore, in the case of the present invention, a larger recording margin is obtained than in Comparative Example 2, and the performance is equivalent to that of the TeGe/Ga5bW body of Comparative Example 1, which is characterized by a large recording margin. This means that if recorded as a disk-shaped recording medium, a larger reproduction signal will be generated by 1q, making it easier to detect, and furthermore, even if the film thickness deviates from the optimal film thickness for the film thickness interference effect, the reproduction signal will be larger than that of Comparative Example 2. Since a signal can be obtained, constraints on film thickness control during manufacturing can be significantly relaxed.

Furthermore, in the case of the present invention, the transmittance does not change even after more than 1,000 hours have elapsed, which means that there is no change over time for more than 10 years at a room temperature of 25° C. It can be seen that it has excellent long-term stability as a medium.

〔Effect of the invention〕

Since the information recording medium according to the present invention is constructed as described above, it exhibits excellent effects as described below.

(1) A stable optical recording medium with very good heat and humidity resistance and capable of long-term recording retention can be obtained.

(2) The transition temperature from amorphous to crystalline can be easily controlled by controlling the composition and can be set appropriately high.
There are 19 optical recording media that can increase the reproducing optical power without impairing recording stability or archivability.

(3) Since a very large recording margin can be obtained as a reflectance difference, a stable optical recording medium in which the amplitude of the reproduced signal can be kept to a large extent can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing an example of an apparatus for manufacturing an information recording medium of the present invention, FIG. 2 is a view taken along arrow A-A' in FIG. 1, and FIG. 3 is a diagram showing an information recording medium of the present invention. FIG. 2 is a schematic explanatory diagram showing another example of the manufacturing apparatus.

Claims (2)

[Claims] (1) In an information recording medium that records information by forming a thin film on a substrate and changing the optical characteristics of the thin film by heat generated directly or indirectly by irradiating the thin film with an energy beam. , An information recording medium characterized in that the thin film is mainly composed of gallium, antimony, germanium, tellurium and selenium. (2) In the information recording medium according to claim (1), the proportion of selenium in the total thin film component is 5% by number of atoms.
~22%, and the composition of each component excluding selenium is of the general formula (GaYSb100-Y)X(TeZGe100-Z)
100-Xx: % number of atoms of (Ga and Sb) in the thin film y: % number of atoms of Ga in (Ga and Sb) z: % number of atoms of Te in (Te and Ge) When expressed as x , y, and z ranges are 2≦x≦, respectively.
50, 2≦y≦70, and 30≦z≦70.