JPS5871193A - Optical information recording medium - Google Patents

Abstract

PURPOSE:To enhance sensitivity and prolong useful life, by a method wherein light reflectance at a part along a recording track is enhanced as compared to that at other part, in a optical information recording medium film consisting of a metal having a specified melting point, C and H. CONSTITUTION:A recording film 12 consisting of a metal having a melting point of 25-600 deg.C, such as Te, In, Sn or an alloy thereof, and a compound containing C and H, such as methane, is formed on a substrate 11 such as an acrylic resin plate in a thickness of about 200Angstrom -1mum. When the metal having the low melting point is Te, sputtering is conducted in a gaseous mixture of methane and argon by using Te as a target. The amounts of C and H contained in the film are controlled by the mixing ratio of the gases and the high-frequency power impressed. The light reflectance is increased when an energy beam 13 is irradiated at a given energy value, while a recess is produced and the reflectance is lowered when the beam 13 is irradiated at a further higher energy value. Accordingly, reproduction and recording can be performed easily.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical information recording medium on which recorded information can be read optically, and in particular, a recording film in which holes or four parts are formed by irradiation with an energy beam such as light or heat. The present invention relates to an optical information recording medium on which information is recorded.

As an optical information recording medium, conventionally, Kente-5===tC
There is one in which an energy beam is irradiated onto a recording film l formed on a substrate/soil to form a pit-no row corresponding to the information to be recorded. In such optical information recording media, it has been known to use tellurium (Te) as the recording film t. Te film can form desired holes (pits) with very low energy,
It is extremely promising as a highly sensitive material in this type of application. Sensitivity here refers to the energy (mJ/crn) required to form a recording section (pit in this case) per unit area.
Defined by

However, when Te is left in the atmosphere, it is oxidized by oxygen and moisture and quickly becomes transparent. When used as a recording film, the film thickness is extremely thin, about 700×, so the deterioration in sensitivity due to increased transparency caused by oxidation of the film is significant. That is, when the film is oxidized, the melting and evaporation temperatures increase, and absorption of energy such as light decreases due to transparency, so the energy required to form pits increases, resulting in deterioration of sensitivity.

For example, when left in an atmosphere with a temperature of 70° C. and a relative humidity of 85%, the sensitivity decreases by about 20% in about 5 hours, and by about 50% in about 15 hours.

For this reason, various measures have been taken to prevent oxidation of the Te film.

One of these methods, a method of coating a Te film with a stable inorganic substance, is effective in preventing oxidation of the Te film, but it has not been put to practical use because it reduces sensitivity and is expensive. On the other hand, plastic coatings have a low thermal conductivity and are advantageous in that they do not impair sensitivity to a small extent, but they allow oxygen and water to permeate through them relatively easily.
It is not very useful in preventing oxidation of the membrane.

In addition, high-density and large-capacity recording is now required for such optical information recording media, and therefore
．． It is necessary to form recording tracks at a pitch of 5 to 2 μm. In that case record.

In order to facilitate tracking during playback, a method was used in which a glass plate with grooves formed by photolithography was used as the master, and the tracking grooves were transferred to an acrylic plate.
There were problems with the accuracy and cost of the tracking groove.

The present invention has been made to solve the above problems, and an object of the present invention is to provide an optical information recording medium with high sensitivity and long life, and in which a tracking pattern can be easily formed with high accuracy.

The optical information recording medium according to the present invention records information as holes or four parts by irradiating a recording film on a substrate with an energy beam, and the recording film is made of a low melting point metal or an alloy thereof. It is characterized in that it is formed of a film containing C and H, and that a dragging pattern with a higher light reflectance than the surrounding area is formed in advance along the recording track on this recording film, thereby achieving high sensitivity and long length. In addition to having the advantages of long life and low noise, it also facilitates tracking and is designed to reduce costs. Here, as the low melting point metal, a metal having a melting point of 25 to 600° C. is used from the viewpoint of film forming technology and recording characteristics. Examples of such low melting metals include Cd, In, Sn, Zn, Pb,
Bi.

There are Te etc. These metals may be used alone, but
Alloys thereof can also be used.

That is, the present invention takes advantage of the fact that a high light reflectance can be obtained by irradiating the recording film with a relatively low-energy energy beam [7] Forming a tracking pattern,
Furthermore, when an energy beam of higher energy is irradiated, a concave portion is formed in the hole, and conversely, the light reflectance decreases, which is used to record information.

Hereinafter, embodiments and examples of the present invention will be explained in 5-5 with reference to the drawings. Explain in detail.

FIG. 1 is a sectional view showing one embodiment of the present invention. In the figure, reference numeral 11 denotes a substrate, and in this embodiment, an acrylic plate, which is one of synthetic resins, is used. However, other synthetic resin plates or glass plates may also be used, and can be appropriately selected depending on the information recording and reading method. Then, a recording film 12 made of a low melting point metal film containing C and H is formed on this substrate II. The thickness of this recording film 12 needs to be thick enough to obtain sufficient light reflectance and thin enough not to impair sensitivity, and is 200X to 1 μm.
The degree is appropriate.

For example, if a Te film is selected as the low melting point metal, the recording film 1
2 is a gas containing C and H using Te as a target;
For example, it can be obtained by sputtering in a mixed gas of methane (CH4) and argon (Ar). Here, the content of C and H in the Te film can be freely controlled by the mixing ratio of CH4 and Ar and the applied high frequency power.
A high frequency of about 0.3 W/cm (13,56 M
When power (Hz) is applied between the Te conductor and the substrate 1, a film containing C in an atomic ratio of 02 to Te can be formed. In this case, the compositional formula of the film is Te1
It can be expressed as -xCx (H), and the H content at which the film is most chemically stable is determined by X. Here, (2) the content can be arbitrarily selected as long as it is not contained in such a large amount that hydrogen gas (H2) is generated in the film. Furthermore, since the film thickness is proportional to the snow R sagging time, it can be freely controlled.

The optical constants of the recording film 12 are determined by the film composition, and in the above example, a film thickness of about 700× had a maximum reflectance of 50×, and the recording characteristics were the best. Furthermore, the recording film 12 produced under these conditions has an amorphous value, and the nip area around the holes or recesses in the recording state is smoother than that of a polycrystalline Te film.
The noise level during information reproduction can be kept low.

The inventor has proposed that the recording film 12 made of a low melting point metal such as the Te film containing C and H or an alloy film thereof is the first
As shown in the figure, when irradiated with an energy beam 13 such as a laser beam with energy above a certain value, the light reflectance increases, and when an even larger energy beam above a certain value is irradiated, depressions and even holes are formed. The main finding is that the light reflectance decreases to below the initial value. FIG. 2 shows a recording film 12 made of a Te film containing C and H according to the above embodiment with a spot diameter of 1 μm on the surface of the recording film 12.
, shows changes in the light reflectance of the recording film 12 with respect to beam energy when irradiated with a laser beam having a wavelength of 830 nm while scanning at a speed of 4 m/s.

That is, a laser beam of 1.5-35 mW is
By scanning the recording film 12 with /a, the light reflectance increases from 50 inches (initial value) to 80 inches, and as a result, tracking marks are formed along the recording track as shown in FIG. It is possible to form a second turn. Furthermore, by scanning a laser beam of 35 mW or more that is modulated (on, off) according to the information to be recorded along the tracking pattern 21 at the same speed,
It becomes possible to form holes or recesses 22 according to information. When recording this information, please use the tracking number 4.
While detecting reflected light or transmitted light from turn 21,
By aligning the recording laser beam, that is, tracking, the recording track pitch can be adjusted to 1.5 to 2.
It is possible to easily achieve high-density recording on the order of μm. Needless to say, the tracking No. 21 can also be used for tracking during playback.

Figure 4 shows the state of deterioration of sensitivity over time in an atmosphere with a temperature of 70°C and a relative humidity of 85°C, that is, the life characteristics.
FIG. 3 is a diagram showing a comparison between a case A of a conventional recording film made of a single Te and a case B of a recording film according to the present invention. In this figure, the deterioration in sensitivity 6 is expressed as a change with respect to the initial value of the reciprocal of the energy of the energy beam necessary for recording, and both A and B show the case where the recording film is formed on an acrylic substrate.

As can be seen from this figure, in the case of a recording film made of only Te, the sensitivity deteriorates over time as shown by A. This is because local transparent areas (spots) occur over time, and after about 170 hours, the sensitivity deteriorates over the entire recording film. On the other hand, in the case of the recording film made of a T8 thin film containing C and H according to the embodiment of the present invention, B
As shown in , even after 1,000 hours, no stains like those seen on recording films made of pure Te were observed, and the sensitivity remained almost constant, indicating that a long service life was achieved. .

Figure 5 (,) is an optical micrograph showing the surface condition of a conventional recording film made of pure Te on an acrylic substrate after 20 hours at a temperature of 70°C and a relative humidity of 85 m.
b) shows the surface condition of a recording film made of a Te film containing C and H according to an example of the present invention that was left for 1,000 hours under the same conditions.

The magnification is 50 times in both (a) and (b).

Also, the sensitivity of the recording film according to the present invention, that is, the energy required to form a hole or four parts per single 10=potential area (
It was confirmed that the sensitivity (mJ/crn) was equivalent to or slightly higher than the sensitivity of the conventional Te film body recording film. That is, the optical information recording medium according to the present invention not only exhibits little deterioration in sensitivity over time, but also has the advantage of high sensitivity.

Note that if the content of C in the recording film is less than 005 in atomic ratio to Te, the above-mentioned effect will not be observed;
A decrease in sensitivity was observed when the temperature exceeded s. This point also applies when a low melting point metal other than Te or an alloy thereof is used for the recording film. Therefore, it is desirable that the content d1 of C in the recording film is in the range of 0.05 to 0.08 in terms of atomic ratio to the total amount of metal elements.

In the above embodiment, the recording film was formed by reactive sputtering in a mixed gas of CH4 and Ar, but a re film containing C and H was formed on the substrate by using CH4 and Te vapor in the form of plasma. It is also possible to form a recording film consisting of: A similar recording film can also be formed by vapor phase growth or plasma vapor phase growth using T(](CH3)2 (trimethyltellurium) or Te(C2Hs)2 (diethyltellurium). Te as a method.

Some or all of the C and H atoms may be ionized and deposited on the substrate in the form of a beam.

The low-melting metal is Zn (melting point -319°C).

Cd (320℃) etc. also have CH4 and Ar in exactly the same way as Te.
A recording film having properties equivalent to those described above can be obtained by sputtering in a mixed gas of

Still Bi2Te3 (585℃), In5b (535℃
) is also known to have a low melting point, and similarly to the above, it is possible to form a record of the above properties by the tsuttering method. Sputtering of Bi (271°C) is impossible, but the above properties can be achieved by reactive vapor deposition. A recording film having the following properties can be formed.

In addition, the CH4 gas mentioned above may be C2H4 (ethylene) gas or C2H4 gas.
It is also possible to replace it with 2H2 (acetylene) gas.

In this way, the optical information recording medium according to the present invention has a long life and high sensitivity, and requires a transfer process using a master disc with grooves, unlike the conventional one in which grooves are used as a tracking pattern. This has the advantage that a tracking pattern can be easily formed to a good degree without any problems.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view for explaining one embodiment of the present invention, and FIG. 2 is a diagram showing the relationship between the energy of the laser beam irradiated to the recording film and the light reflectance of the recording film in the same embodiment. FIG. 3 is a plan view showing the tracking pattern and information recording state in the same embodiment; FIG.
Figures (a) and (b) are micrographs showing the surface state of the recording film in a conventional recording medium and a recording medium according to the present invention. DESCRIPTION OF SYMBOLS 11... Substrate, 12... Recording film, 13... Energy beam, 27... Tracking pattern, 13
-22...hole or four parts. 14- Figure 3 Figure 4 Early opening of the pancreas (h) Figure 5 (a) (b)

Claims (3)

[Claims] (1) In an optical information recording medium consisting of a substrate and a recording film that is deposited on the substrate and records information by forming holes or recesses by irradiation with an energy beam, the recording film has a It is characterized by containing a metal or its alloy having a melting point of ~600°C, C and H, and having a tracking notarne formed along the recording track with a higher light reflectance than the surrounding area. Optical information recording medium. (2) The optical information recording according to claim 1, wherein the content of C in the recording film is in an atomic ratio of 0.05 to 0.8 with respect to the total amount of metal elements. Medium. (3) The optical information recording medium according to claim 1 or 2, wherein the thickness of the recording film is 200X to 1 μm.