JPS63147689A - Information recording medium - Google Patents

Abstract

PURPOSE:To enhance C/N, by providing a thin film comprising gallium, antimony, germanium and tellurium as main constituents on a base to produce an information recording medium. CONSTITUTION:A base 5 is rotated at a rate of 60-600rpm by a driver 6, a GaSb alloy is set in a resistance heating evaporation boat 1a, while a TeGe alloy is set in a resistance heating evaporation boat 1b, and the alloys are evaporated in preset amounts based on film thicknesses detected by film thicknessensors 4a, 4b. As a result, an information recording medium is obtained which is provided with a thin film comprising gallium, antimony, germanium and tellurium on the base 5. Since an extremely large recording margin can be provided, a stable information recording medium is obtained which is capable of recording with a large change in optical characteristics through using suitable recording power and can give a large amplitude of reproduction signals.

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.

[Conventional technology]

Conventionally, the following two methods have been proposed for optical information recording media.

■ The first method is to irradiate energy beams such as laser beams or electron beams, and use the heat to melt and evaporate the
This is a method of recording holes (pits) in a medium, and examples thereof include thin films of Te, Te-based compounds, chalcogen compounds, metal compounds, organic dyes, and the like.

■ The second method is to irradiate the recording medium with a beam.
For example, the optical properties of the medium itself (refractive index,
This method changes the reflectance (reflectance, etc.), and known methods include chalcogenated H119, Te low oxide thin film, and TeGe thin film.

In order to reproduce the information recorded in this way, a readout beam is irradiated onto the recorded location. In (2), a reproduced signal is extracted as a difference in reflected light due to a change in reflectance between a region where @-conversion by the recording light has occurred and a region where it has not.

In addition to improving the characteristics of the medium itself, various methods have been devised to obtain high quality reproduction signals. In particular, in the case of method (■), the reflectance of the crystallized part is made higher or the reflectance of the amorphous part is made lower, or conversely, the reflectance of the crystallized part is made lower than that of the amorphous part. Various methods are being considered, such as lowering the value. As an example,
Adjust the film thickness of the recording medium so that there is an optical path difference of 1/2 wavelength between the front and back surfaces of the recording medium.
The reflected light is canceled by the effect of film thickness interference to lower the fouling rate, and when the recording beam is irradiated, the interference condition of the film is shifted due to the change in the complex refractive index of the film at that part. A method of amplifying the difference in reflectance change is well known.

[Problem that the invention seeks to solve]

However, the above-mentioned conventional recording media have various problems as described below, and are not necessarily fully satisfactory.

That is, in the medium of the method described in item (2), pits are formed in the medium by heating the recording light, but it is not so easy to create a highly sensitive medium that requires less energy for recording; for example, Sensitivity may be insufficient when recording at high speeds, and the outline of the formed hole may be distorted, the surrounding area may rise, or debris may remain in the pit, resulting in poor signal quality. It rarely worsens the noise ratio.

Furthermore, since it is not possible to apply a coating film such as a protective film to the recording medium, it is difficult to stabilize the life of the film over a long period of time. Furthermore, problems such as contamination of the surrounding area and harm to the human body due to evaporated matter generated by the formation of the holes have become non-negligible.

On the other hand, with the recording medium using the method in item (■), there is less disturbance in the shape of the recording area as in the case of the perforated type in item (i) above, and since it is possible to attach a protective film, there is no need to worry about the stability of the film itself. The demands are not that strict either. Another advantage was that there was almost no contamination due to evaporated matter. However, with such materials, the optical characteristics of the recording part and the non-recording part ↑
It was not easy to find a good recording medium with a large difference in 1 and a large amplitude of the reproduced signal. Among these materials, TeQe can be easily formed into a thin film using well-known thin film fabrication techniques such as evaporation Yasbatta, and the difference in fouling rate (recording margin) between crystalline and amorphous materials is υ1. It had the advantage that a large amount of water could be obtained.

However, when a thin film was actually formed on a disk-shaped substrate and the recording characteristics of TeGe were evaluated, it was found that the following problems were encountered. That is, the inventors et al.
According to the results of experiments conducted on the Ge thin film, the C/N (ratio of carrier signal to noise), which is an important item indicating the quality of the reproduced signal, was not sufficient. In addition, the recording margin, which indicates the size of the reproduced signal, is by no means sufficient compared to the medium in item (■), and in this case, 1CQ
If the film thickness of e is set so that the above-mentioned film thickness interference effect can be expected, the reflectance at the recording wavelength will become too small, and the intensity of reflected light required for stable tracking and control of fuzzing will be obtained. It was difficult and rare. Furthermore, if this problem is avoided by increasing the reflectance by changing the film thickness, a problem has arisen in that the recording margin is further reduced.

It is an object of the present invention to solve these problems and provide an information recording medium with an excellent C/N ratio. A further object of the present invention is to provide a recording medium in which the intensity of reflected light can be adjusted to the extent necessary for stable tracking and control of fugitive casing while maintaining a sufficient recording margin.

(Means for Solving the Problems) An object of the present invention is to form a thin film on a substrate, and apply an optical beam to the thin film by direct or indirect heat generated by the principle of an energy beam onto the thin film. The present invention is achieved by an information recording medium that records information by changing physical properties, the information recording medium being characterized in that the elements constituting the thin film contain gallium, antimony, germanium, and delurium as main components. .

The recording thin film in the present invention refers to gallium (Ga), antimony (Sb), delurium (Te), germanium (G
e) as a main constituent element. Although its composition is not particularly limited, in order to effectively exhibit the effects of the present invention, a composition represented by the following general formula is preferred. That is, (Gay S bloo-y) x (Toz Gol
oo-z) 1oo-xy: Number of atoms of Ga in (Ga and sb>%)Z: Number of atoms of Te in (Te and Ge)%X: Number of atoms of (Ga and sb>% in the thin film) In this case, it is preferable that the range of X is 2≦x≦50.If there is a small amount of On the other hand, if the amount is too large, it becomes difficult to form a thin film with a stable amorphous structure, or it becomes difficult to form a thin film with an appropriate transition temperature as described in the present invention, which is undesirable. It is more preferable that y and 7 are in the following range.

2≦y≦70.30≦2≦70 Outside this range, it is not preferable because a thin film having a stable amorphous structure cannot be easily formed or a thin film having an appropriate transition temperature cannot be formed.

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

Although the thickness of the recording film is not particularly limited, when the film thickness interference effect is used as described above,
When using the recording medium of the present invention, it is preferable to set the wavelength in the range of 80 to 120 nm.

However, it is clear from the fact that the recording medium of the present invention is characterized in that it utilizes changes in the optical properties of the medium itself due to the light beam that it is possible to use the recording medium with a film thickness other than this. It is.

Further, 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, A metal plate such as AQ can also be used.

Furthermore, in order to effectively bring out the original characteristics of the recording medium of the present invention, it is necessary to protect the recording medium between the substrate and the recording layer or on the recording layer.
f15 can be provided. The FF1 layer may be formed of an inorganic film such as 3i02 or an ultraviolet curing film using a method such as vapor deposition, electron beam evaporation, sputtering, or spin code, or may be formed of epoxy, polycarbonate, etc. using an adhesive or the like. Alternatively, resin, film, glass, etc. may be pasted together, or a method such as lamination may be used. In this way, various effects can be expected depending on the protective layer, but the first is
Examples include extending the life of the recording medium by improving durability and moisture absorption resistance, and using a single disk by omitting disk bonding.

When exposing a recording medium to high temperatures using heating means such as energy beams or heaters, it is necessary to prevent the recording film from deforming due to peeling or swelling from the substrate, and to prevent the recording medium from disappearing due to melting, evaporation, diffusion, etc. It can be expected to have effects such as preventing negative effects.

Also, as a matter of course, since the present invention utilizes changes in the optical properties of the recording thin film itself, the substrate and protective film themselves are not directly involved in recording performance, and materials other than those exemplified may be used. There is no difference in what you do. Furthermore, in some cases, the protective film may be omitted without departing from the spirit of the present invention. In addition, as is clear from the spirit of the present invention, configurations other than those listed in the present invention,
(It goes without saying that even if the IIi4 configuration is adopted, it does not depart from the spirit of the present invention as long as changes in the optical characteristics of the recording thin film itself are essentially utilized.

(Manufacturing method) There are various methods for manufacturing the recording medium of the present invention, but the vacuum evaporation method and 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
ld> corresponds to the evaporation boat for resistance heating, and 2 corresponds to the port (2' a, 2' b, 2' c, 2
' d) slit plate provided with 3 is a shutter, 4
(4a, 4b) 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 of the ports is set to reach the substrate through each slit, and each can be controlled independently.

In order to produce the recording medium of the present invention using such an apparatus, for example, most simply, a Ga S b alloy is set in 1a and a TeGe alloy is set in 1b, and each is independently connected to the film thickness sensor 4.
It is sufficient to evaporate a preset amount using a and 4b as bases.

The substrate is rotated by a 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, if more precise control of the composition is desired, the four elements may be placed in independent boats and controlled independently. Roughly speaking, 1a has Te
It goes without saying that these methods may be combined, such as Ge for 1b and Qa3b for 1C.

Next, regarding the sputtering method, a recording film preparation method 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 the start of sputter discharge, 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 vapor deposition. 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 Ga5bf)Sb may be placed on a TeGe target to have a predetermined composition and co-sputtered, or (G
A four-element alloy target of a, Sb, Te, Ge) may be prepared, and its composition may be adjusted in consideration of the sputtering rate of each element so that the thin film after sputtering has a predetermined composition. As the sputtering residue, use an inert gas such as argon, RF output 100-200W, vacuum degree 5x1 during sputtering.
This can be carried out under conditions of approximately 0" to 3X10-3 Torr. Naturally, appropriate sputtering conditions are not constant depending on the apparatus, and it goes without saying that recording media may be produced under conditions other than these conditions. do not have.

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. I can do it.

Furthermore, other methods for producing the recording thin film include thin film producing techniques such as electron beam evaporation.

[Measurement method] A total of one song method used in the examples of the present invention will be explained.

■A pair of electrodes are formed on the recording thin film fabricated on the glass substrate as described in the transition temperature 'lA manufacturing method, and one end of the electrode is
Connect a resistor of Ω in series with . Apply a constant voltage of 5 to both ends of the remaining electrode and resistor, measure the voltage across the resistor with a voltmeter, calculate the applied voltage and current of the thin film from this, and calculate the resistance value. Next, the entire feeding plate is heated uniformly using a heating furnace, and the resistance is measured while heating the plate at a rate of approximately 10'C/min using a temperature controller, and the point at which the resistance changes from high to low is determined. The temperature at that time was determined as the transition temperature.

■ Recording Margin Measure the anti-height on the amorphous substrate side and the anti-Oij ratio on the crystalline substrate side of the recording thin film fabricated on the glass substrate using a spectrophotometer (Newly manufactured by Hitachi Seisakusho, Model 323). measure,
In particular, the wavelength of the semiconductor laser used for recording is 830n.
The difference in reflectance of m was determined and used as the recording margin.

■ Recording characteristics The disc-shaped recording medium is made of polycarbonate (hereinafter referred to as PC).
'34 optical disc substrate with pre-group on which a recording thin film was formed was used. Signal recording and reproduction was performed using an optical disc evaluation device (OMS-1000> manufactured by Nakamij Co., Ltd.) at a linear velocity of 4 m/min. The recording frequency was 1 MH2, and the reproduction power was 0.5 to 0.8 mw.The C/N was O.
The RF signal from MS-1000 was determined using a spectrum analyzer with a bandwidth of 30 KHz. A semiconductor laser with a wavelength of 830 nm was used for recording and reproduction here.

(2) Composition A recording thin film prepared on a glass substrate was dissolved with aqua regia, nitric acid, etc. and separated from the substrate. This solution was analyzed using high-frequency inductively coupled plasma (ICP) emission spectrometry (Seiko Electronics).
Inc. SPS-1100 model), the content of each element was determined, and the composition ratio (number of atoms %) was calculated.

[Applications] The recording medium of the present invention obtained in this way has characteristics particularly suitable for information recording media such as optical disks, optical tapes, optical cards, optical floppy disks, microfiche, laser 00M, etc. . 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, by combining crystallization and melting/quenching processes, it can be applied to the purpose of repeated recording and erasing.

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

Examples 1-5. Comparative Example 1 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 3 are based on the vacuum evaporation method, which uses the vacuum evaporation apparatus illustrated in FIG.
A Ga3b alloy was charged into the port 1b, and a TeGe alloy was charged into the port 1b, and two-source simultaneous vapor deposition was performed. Adjust the amount of evaporation from each port using the film thickness monitor 48.4b,
The substrate was rotated at about 30 Q r pm to ensure uniform mixing of evaporates from the two ports. For comparison, a film made only of TeGe alloy was also prepared and designated as Comparative Example 1.

Table 1 shows the composition and evaluation results of the record film.

Further, Examples 4 and 5 used the sputtering apparatus illustrated in FIG. 3, which used a HeGe alloy target as a sputtering target and a G
A combination of a3b alloy pellets and Sb pellets is arranged and cosbatted. The sputtering conditions are 5X using argon gas as sputtering gas.
The process was carried out at 10 -3 Torr and RF output of 100 W, the substrate was rotated at about 4 Orpm, the composition was mixed to be uniform, and the sputtering range was adjusted using a film thickness monitor. The composition and evaluation results are shown in Table 1.

As is clear from Table 1, compared to Comparative Example 1 with a transition temperature of 170'C, in Examples 1 to 5, the transition temperature can be easily controlled by adjusting the amounts of Ga and sb added, and the transition temperature changes from amorphous to crystalline. This allows the transition temperature to be set appropriately.

As a result, for example, when the crystallization temperature is raised and the film thickness interference effect is used, the reduction in reflectance of the amorphous recording film can be compensated for by increasing the reproduction light power, which is necessary for precise tracking and focusing control. The amount of light reflected from the recording layer can be ensured. This means that at the crystallization temperature of the comparative example, the temperature of the recording layer will rise and approach the crystallization temperature, making crystallization more likely to occur, which may impede the stability and storage stability of the recording. Regarding the reproduction light power, the medium of the present invention means that the margin for tracking and force shifting is increased without impairing the recording characteristics as described above.

Furthermore, higher sensitivity can be achieved by lowering the transition temperature.

In addition, in the case of the present invention, as is clear from Table 1, the recording margin is larger by 1q than in Comparative Example 1, and if recorded as a disk-shaped recording medium, the reproduced signal becomes larger and detection becomes easier. . Furthermore, even if the film thickness deviates from the appropriate film thickness for the film thickness interference effect and the reflectance of the amorphous state cannot be lowered sufficiently, the reproduced signal that is larger than that of the comparative example will be j'
Therefore, constraints on film thickness control during manufacturing can be significantly relaxed.

Examples 6 to 10 Using the same method as described in Examples 1 to 3, the substrate was changed from glass to an optical disk substrate with a pre-group made of PC with a diameter of 130 mm and a thickness of 1.2 mm, and two types of composition ratios were used. A different recording medium was prepared and designated as Example 6.7.

In addition, using the same sputtering method as in Example 4.5), the substrate was changed from glass to a PC board with a diameter of 130 mm and a length of 1.2 m.
In Examples 8 to 10, recording media with holes having three different composition ratios were prepared by using an optical disk substrate with a pregroup having a thickness of m. In the case of the disk shown in Example 9, a protective film of SiO2 was formed on the obtained recording film by sputtering. In this case, sputtering uses a SiO2 target, and the vacuum level is 4.5X10'Torr7)Ltf')
The test was carried out in an atmosphere with an RF power of 1 KW and a substrate rotation speed of 4 Orpm.

The recording/reproducing characteristics of each sample sample were measured using a Hobeta optical disk evaluation system (OMS-1000). The linear velocity was 4 m/sec, and the recording frequency was 1 MH2.

The evaluation results are shown in Table 2. As is clear from Table 2, Examples 6 to 10 that satisfy the present invention exhibit good recording characteristics.

That is, the disc obtained in Example 6 had a C/N of 4 when the read power was 0.5 mW and the write power was 2.5 mW.
8 dB was recorded, and the same (Example 7, the output power was 3 m)
A C/N of 46 dB was obtained at W. Also, the playback power is 0.
7 mW, and in Example 8, the write power was 44 mW with a write power of 5 mW.
dB C/N, in Example 9, the write power is 10 m.
A C/N of 42 dB was obtained for W, and in Example 10, a C/N of 49 dB was obtained for the ti-included power of 5.5 mW, and good recording/reproducing characteristics were obtained in all of these Examples. .

〔Effect of the invention〕

As described above, the present invention applies to Qa, 3b, and Te.

It is characterized by containing Ge as a main component, and has excellent effects as described below.

(1) Since the recording margin is extremely large, recording with large changes in optical characteristics can be performed with appropriate recording power.
A stable optical recording medium with a large playback signal amplitude can be obtained.

(2) High C/N, which indicates signal quality, and good recording.
An optical recording medium having playback characteristics is obtained.

(3) The recording film can be easily and easily produced using conventional vapor deposition sandbatter technology. In addition, the transition temperature from amorphous to crystalline can be easily controlled by controlling the composition.
1q of optical recording media having a transition temperature suitable for the purpose are prepared.

[Brief explanation of the drawing]

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

Claims (2)

[Claims] (1) An information recording medium in which a thin film is formed on a substrate, and the optical properties of the thin film are changed by heat generated directly or indirectly by irradiation of an energy beam onto the thin film and information is recorded. The elements constituting the thin film are
An information recording medium characterized by containing gallium, antimony, germanium, and tellurium as main components. (2) In the information recording medium according to claim (1), the general formula showing the composition of the thin film is (Ga_ySb_1_0_0_-_y)_x(Te_z
Ge_1_0_0_-_z)_1_0_0_-_xy:
% number of atoms of Ga in (Ga and Sb) z: % number of atoms of Te in (Te and Ge) x: % number of atoms of (Ga and Sb) in the thin film When expressed as: x, y, z The range of 2≦x
An information recording medium characterized in that ≦50, 2≦y≦70, and 30≦z≦70.