JPS6025278B2 - optical information recording medium - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical information recording medium in which recorded information can be optically exchanged, and in particular, holes or recesses are formed in a recording film 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 by.

2. Description of the Related Art Conventionally, there is an optical information recording medium in which a recording film formed on a substrate is irradiated with an energy beam to form a bit string corresponding to information to be recorded.

In such optical information recording media, it has been known to use tellurium Te as a recording film. T
The e-membrane can form desired holes (bits) with very low energy, making it extremely promising as a highly sensitive material in this crab application. Here, incubation refers to the energy (mJ/
) defined in ). 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 Å, so the sensitivity deteriorates significantly due to increased transparency caused by oxidation of the film. That is, when the film is oxidized, the melting and evaporation temperatures rise, and absorption of energy such as light decreases due to transparency, which increases the energy required to form bits, resulting in deterioration of sensitivity. For example, if you light up an atmosphere with a temperature of 7 pm and a relative humidity of 85%, the sensitivity will drop by about 20% in about 5 hours, and about 50% in about 15 hours.
It will decrease by 0%.

For this reason, various measures have been taken to prevent oxidation of the Te film. One of these methods, a method of coating the 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 therefore advantageous in that they do not impair sensitivity to a small extent, but they allow oxygen and water to permeate through them relatively easily, so they are not very useful in preventing oxidation of the Te film. Also,
Such optical information recording media are required to have high-density and large-capacity recording, and therefore
It is necessary to form recording tracks at a pitch of 2 degrees.

In this case, in order to facilitate tracking during recording and playback, a method was used in which a piece of glass with grooves formed using the photographer's engraving method was used as a pig board, and the tracking book was transferred onto an acrylic board. There were problems with groove accuracy and cost. 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 in the form of holes or recesses by irradiating a recording film deposited on a substrate with an energy beam, and the recording film is formed of a metal with a low friction point. The recording film is formed by a film containing carbon or an alloy thereof, and a tracking pattern having a higher light reflectance than the surrounding area is formed along the recording track in advance. In addition to having the advantages of high sensitivity, 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 qo is used due to film forming technology and recording characteristics. Examples of such low-melting metals include Cd, ln, Sn, Zn, Pb, Bi, and Te. These metals may be used alone, but alloys thereof may also be used. That is, the present invention utilizes the fact that a high light reflectance can be obtained when the recording film is irradiated with a relatively low-energy energy beam, and forms a tracking pattern, and further irradiates the recording film with a higher-energy energy beam. Information is recorded by utilizing the fact that holes or recesses are formed and the light reflectance is reduced.

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a sectional view showing an 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 hydrogen is formed on this substrate 11. The thickness of this recording film 12 must be thick enough to obtain sufficient light reflectance and thin enough not to impair sensitivity.
Approximately 1Am is appropriate. For example, Te as a low melting point metal.
When a film is selected, the recording film 12 is obtained by sputtering Te as a target in a gas containing C and hydrogen, for example, a mixed gas of methane (CH4) and argon (~).

Here, the content of C in the Te film can be freely controlled by the mixing ratio of CH4 and ~ and the applied high-frequency power.
13.58MHZ) power Te target and substrate 1 1
When the voltage is applied between 1 and 2, it is possible to form a film containing C in an atomic ratio of 0.2 to Te. In this case, the compositional formula of the film can be written as Te, - length x (H), and the content on the day when the film is chemically most stable is determined by x. Here, the H content can be arbitrarily selected as long as it is not contained in such a large amount that hydrogen gas (2) is generated in the film. Furthermore, since the film thickness is proportional to the sputtering 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, the reflectance reached a maximum of 50% at a film thickness of about 700 Å, and the recording characteristics were the best. Furthermore, the recording film 12 produced under these conditions has an amorphous value, and the edges around the holes or recesses in the recorded state are smoother than that of a polycrystalline Te film, and the noise level during information reproduction can be kept low. The present inventor has proposed that the recording film 12 made of a low-melting point metal such as the Te film containing C and hydrogen or an alloy film thereof can be used as an energy source such as a laser beam or the like having an energy of a certain value or more, as shown in FIG. It has been found that when the beam 13 is irradiated, the light reflectance increases, and when a larger energy beam of a certain value or more is irradiated, depressions and even holes are formed, and the light reflectance decreases to below the initial value.

FIG. 2 shows a recording film 12 made of a Te film containing C and oxide according to the above embodiment while scanning a laser beam with a spot diameter of 1 mountain and a wavelength of 83 m/s on the surface of the recording film 12 at a speed of 4 m/s. It shows the change in light reflectance of the recording film 12 with respect to beam energy when irradiated. That is, 1.5
By scanning the recording film 12 with a ~38 hW laser beam at 4 m/s, the light reflectance increases from 50% (initial value) to 80%, and as a result, the recording track is formed as shown in FIG. A tracking pattern 21 can be formed along the line.

Further, by scanning a laser beam of 38 hW or more modulated (on/off) according to the information to be recorded along the tracking pattern 21 at the same speed, a hole or a recess 22 according to the information is formed. becomes possible. When recording this information, the recording laser beam is aligned while detecting reflected light or transmitted light from the tracking pattern 21, that is, tracking is performed, so that the recording track pitch is 1.5 to 1.5.
High-density recording of 2 mm can be easily achieved. It goes without saying that the tracking pattern 21 can also be used for tracking during playback. Figure 4 shows the state of deterioration of sensitivity over time, that is, the life characteristics of conventional Te
FIG. 3 is a diagram showing a comparison between a case A of a recording film made of a single substance and a case B of a recording film according to the present invention.

The deterioration in sensitivity in this figure is expressed as a change from 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 you can see from this figure,
In the case of a recording film made of Te alone, as shown by A, the sensitivity deteriorates over time.

This is because local transparent areas (spots) occur over time, and after about 170 hours the sensitivity deteriorates over the entire recording film. In contrast, C
In the case of a recording film consisting of a Te thin film containing
As shown in B, even after 1.00 hours had elapsed, no stains like those seen on recording films made of pure Te were observed, and the sensitivity was always maintained at a nearly constant level, achieving a long service life. I understand. Figure 5a shows the conventional Te on an acrylic substrate after 2q hours at a temperature of 70qo and a relative humidity of 85%.
Figure b is an optical micrograph showing the surface condition of a recording film made of a single substance. Indicates surface condition.

The magnification is 5 pm for both a and b. Furthermore, the sensitivity of the recording film according to the present invention, that is, the energy (mJ/) required to form holes or recesses per unit area, is equivalent to or slightly higher than the sensitivity of the secondary recording film made of a single Te film. It was confirmed that

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 feature of high sensitivity. Note that when the content of C in the recording film was less than 0.05 in atomic ratio to Te, the above-mentioned effect was not observed, and when it exceeded 0.8, a decrease in sensitivity was observed.

This point also applies when a low melting point metal other than Te or an alloy thereof is used for the recording film. Therefore, the content of C in the recording film is 0.05 to 0 in terms of atomic ratio to the total amount of metal elements.
．． A range of 8 is desirable. In the above embodiment, the recording film was formed by reactive sputtering I in a mixed gas of CH4 and Ar.
Although it was formed by conducting J-type process, the Te vapor containing C and Te was formed on the substrate by making CH4 and Te vapor into plasma.
It is also possible to form a recording film consisting of a film. Also,
Te(CH3)2 (dimethyltellurium) and Te(C2day5
) 2 (jetyl tellurium) or plasma vapor phase epitaxy can also form a similar recording film. Still another method is to ionize some or all of the Te, C, and Ni atoms and deposit them on the substrate in the form of a beam. Low-melting metals such as Zn (cocoon & point = 31 pi○) and Cd (320°C) are also sputtered in a mixed gas of CH4 and Ar in exactly the same way as Te.
A recording film having properties equivalent to those described above can be obtained. Also, Bi2Te3 (spotted?○), lnSd (535q
Alloys such as (o) and the like are also known to have low melting points, and similarly to the above, a record of the above characteristics can be formed by the sputtering method. Bi (271° C.) cannot be sputtered, but a recording film having the above characteristics can be formed by reactive vapor deposition. Furthermore, the CH4 gas can be replaced with C2day4 (ethylene) gas or C2day22 (acetylene) gas. As described above, the optical information recording medium according to the present invention has a long life and high sensitivity, and can be tracked without the need for a transfer process using a master disc with grooves, unlike conventional ones that use grooves as a tracking pattern. It has the advantage that a pattern for use can be easily formed with good quality.

[Brief explanation of the drawing]

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. 4 is a diagram comparing the life characteristics of the recording medium of the present invention and a conventional recording medium, and 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. 11... Substrate, 12... Recording film, 13
... Energy beam, 21 ... Tracking pattern, 22 ... Hole or recess. Figure 1 Figure 2 Figure 3 Blind screen Figure 5

Claims (1)

[Scope of Claims] 1. An optical information recording medium comprising a substrate and a recording film which is deposited on the substrate and records information by forming holes or recesses by irradiation with an energy beam. The recording film shall contain a metal or its alloy with a melting point of 25 to 600°C, C and H, and shall have a tracking pattern formed along the recording track with a higher light reflectance than the surrounding area. An optical information recording medium characterized by: 2. The optical information recording medium 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. 3. The optical information recording medium according to claim 1 or 2, wherein the recording film has a thickness of 200 Å to 1 μm.