JPS60124038A - Optical recording medium and its production - Google Patents

Abstract

PURPOSE:To assure a practically usable and rewritable medium by depositing a thin film of heat-resistant plastic consisting of any among a polyimide resin, polyamide resin, etc. contg. >= a kind of low melting metal such as tellurium, bismuth, etc. CONSTITUTION:A recording medium which performs optical recording by mak- ing use of the phase transition to crystalline and amorphous states consists of a recording material which causes a structural change by absorbing laser light and a dispersant which supports and holds said material. The former is a low melting metal and the latter is metallic oxide or hydrocarbon. The sputtered film of the heat-resistant plastic contg. the low melting metal is formed on a base plate by sputtering >=1 kind of the low melting metal such as tellurium, bismuth and antimony and one kind of the heat-resistant plastic selected from the group of a polyimide resin, polyamide resin, polyamide imide resin and polyphenylene sulfide resin. A practically usable and rewritable medium is obtd. by using the heat-resistant plastic.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical recording medium and a method for manufacturing the same, and more specifically, the present invention relates to an optical recording medium and a method for manufacturing the same. The present invention relates to an optical recording medium with excellent heat resistance that can withstand repeated rapid heating and cooling caused by laser irradiation, particularly when rewriting information many times, and a method for producing the same.

Laser recording as described above is being considered for use as a large-capacity file memory for optical discs and the like. Conventionally, such recording has utilized perforation, deformation, or structural changes in thin films caused by laser heating, but as the demand for not only write-once information recording but also rewritable information recording has increased, it has become possible in principle to rewrite information. There is increasing interest in recording media that take advantage of possible structural changes. Here, recording using structural changes most commonly refers to crystallization or amorphization of a thin film by laser heating.

For example, a film of polyfluorocarbon containing a low melting point metal such as Te (Japanese Patent Application No. 57-198978;
No. 7-198979), Te in the film is amorphous in the as-prepared state, but crystallizes when heated by laser. Along with this, the optical reflectance of the film changes, and this is used to perform recording.

In such a recording medium, information can be rewritten by further applying laser heating to cause the low melting point metal to become amorphous. That is, information is recorded and erased by repeating crystallization and amorphization of the low melting point metal. Here, in order to be able to record and erase information many times, the heat resistance of the recording medium becomes a problem. In other words, when rapid heating and cooling are repeated by laser heating, high quality records,
In order to erase the data, the medium must have strong heat resistance so that it will not be deformed during laser heating.

Therefore, it is no exaggeration to say that the first condition that a rewritable recording medium must currently meet is sufficient stability against heat cycles such as rapid heating and cooling. However, depending on the manufacturing conditions, the polyfluorocarbon film containing Te may have insufficient thermal stability, which poses a problem in providing a practically usable rewritable optical recording medium. It had become.

The present invention has been made in view of the above points, and an object of the present invention is to provide a rewritable medium that can be put to practical use by improving the heat resistance of the recording medium, and a method for manufacturing the same.

To summarize the present invention, the optical recording medium according to the present invention is a heat-resistant material made of polyimide resin, polyamide resin, polyamide-imide resin, or polyphenylene sulfide resin containing one or more low-melting point metals such as tellurium, bismuth, and antimony. It is characterized by a thin plastic film deposited on a substrate.

Further, the method for producing an optical recording medium according to the present invention includes tellurium, tellurium,
A low melting point metal is contained by sputtering one or more low melting point metals such as bismuth and antimony; and a kind of heat resistant plastic selected from the group consisting of polyimide resin, polyamide resin, polyamideimide resin and polyphenylene sulfide resin. This method is characterized by forming a sputtered film of heat-resistant plastic on a substrate.

The optical recording medium according to the present invention has the advantage that it can be used as a practically usable rewritable medium by using a heat-resistant plastic as a substance containing a low melting point metal in the recording medium. Furthermore, since the method for producing an optical recording medium according to the present invention uses a simple, easy, and easily controllable method called sputtering,
It has the advantage that it can be expected to reduce costs when mass producing optical recording media.

The present invention will be explained in more detail.

In general, a recording medium that performs optical recording using crystallization or amorphization is considered to consist of a recording material that absorbs laser light and undergoes a structural change, and a dispersion medium that supports and retains the recording material. The former is usually a low melting point metal, and the latter is a transparent and weather resistant material such as a metal oxide or hydrocarbon.

The recording material used in the present invention includes tellurium, bismuth, which has been conventionally used in this type of recording medium,
Antimony can be used alone or in combination of two or more.

Further, as the dispersion medium used in the present invention, one selected from the group consisting of polyimide resin, polyamide resin, polyamideimide resin, and polyphenylene sulfide resin, which are plastic inks with good heat resistance, is used. In other words, in order to provide rewritability to a medium, it is necessary for the recording medium to have sufficient thermal stability to withstand repeated rapid heating and cooling over multiple stages by laser beam irradiation. In order to improve the heat resistance of the medium, one of the above-mentioned polyimide resins, polyamide resins, polyamideimide resins, or polyphenylene sulfide resins is used as the dispersion medium.

Next, a method for manufacturing an optical recording medium according to the present invention will be explained.

The method for producing an optical recording medium according to the present invention includes at least one low melting point metal of tellurium, bismuth, and antimony; By sputtering a heat-resistant plastic, a sputtered film of a heat-resistant plastic containing a low-melting point metal is formed on a substrate.

In the present invention, the sputtering target is basically not limited as long as it forms a film of polyimide resin, polyamideimide resin, polyamide resin, or polyphenylene sulfide resin containing a low melting point metal. For example, a composite of the same resin powder and metal powder as the low melting point metal-containing resin film to be formed can be used. For example, when forming a thin film of polyimide resin and Te, the target may be a composite of polyimide resin powder and Te powder.

It seems strange that when a spuck film is produced using a plastic having a relatively complicated structure as described above as a base material, the resulting film has excellent heat resistance just like the base material. The cause of this is not completely understood, but
This is probably due to the following reasons. That is, in sputtering, the target material is evaporated in an atomic or monomeric state. However, this is because these evaporated substances are considered to repolymerize when passing through the discharge plasma, forming a thin film having a structure similar to the target material on the substrate.

The sputtering gas pressure is preferably I
Preferably, xiO-” Torr.
If it is less than 0-'' Torr, the discharge will become unstable and it will be difficult to form a film, and if it exceeds 5 xxo-'' Torr, the film quality will deteriorate.

Further, the RF power is preferably 30 to 200W. If it exceeds a little less than 200, there is a risk that the target will be contaminated, and if it is less than 30, the film deposition rate becomes too low to be practical.

The present invention will be explained in detail below.

Example 1 Using Te as a low melting point metal and polyimide resin as its dispersion medium, a film of polyimide resin containing Te was produced by sputtering and used as an optical recording medium. A composite of Te and polyimide resin powder was used as a sputtering target. Polyimide resin is known as a plastic with excellent heat resistance, exhibits non-spreading and non-melting properties, and is a substance that can be used satisfactorily up to temperatures of 400° C. or higher. Ars was used as the sputtering gas, the gas pressure was 2xto-2 Torr, and the RF power was about 100, sputtering was carried out for 7 minutes to form a film with a thickness of about 1 on the acrylic resin substrate.
A Te-containing polyimide thin film of 0OnIIl was produced. Using this as an optical recording medium, the laser recording characteristics were measured using a semiconductor laser.

Although Te in this medium is amorphous as produced, it is crystallized by laser heating, resulting in a change in reflectance and optical recording. Here, we investigated the conditions for crystallization by changing the pulse width and laser power, and the conditions for making the crystallized part amorphous by further applying laser irradiation.

We also investigated the laser irradiation conditions that would cause deformation or holes in the medium.

The results are shown in Figure 1. For comparison, the results for a conventional ↑e-containing polyfluorocarbon film are shown in FIG. 2.

In order to use the medium as a rewritable recording medium, it is desirable to crystallize or amorphize the medium without causing deformation. In Figures 1 and 2, the shaded areas indicate conditions for crystallization and amorphization without deformation of the medium; in the figures, A is the amorphous area, and B is the crystallized area. part,
C indicates a portion with no change, and D indicates a portion where the medium is deformed or perforated. Note that whether crystallization or amorphization occurred was determined based on a change in the signal level of the reflected light. Further, the presence or absence of deformation and holes was determined by microscopic observation of the irradiated area after laser pulse irradiation.

It is clear that the larger the diagonal areas A and B as described above are, the better the rewritability characteristics are. It has been found that this example occupies a sufficiently large area and has a sufficient rewritable margin for practical use.

Next, a certain portion of the medium of this example was repeatedly irradiated with laser pulses to perform recording and erasing many times. Here, amorphization was repeated using a laser power of 8 m and a pulse width of 50 nsec. As a result, it was confirmed that even after multiple laser irradiations, this recording medium was able to record with high signal contrast and completely erase the recording without causing any deformation.

Example 2 Next, as a low melting point metal in the medium, Bi was used instead of Te.
was selected, and a Wi film was fabricated on an acrylic resin substrate by sputtering using polyimide resin as a dispersion medium. A composite of AT and polyimide resin powder was used as the sputtering target, and the other conditions were as in Example 1.
It was the same.

This was used as an optical recording medium to measure laser recording characteristics.

The results were almost the same as those shown in FIG. 1, and it was found that there were laser conditions that allowed the film to be crystallized and amorphized without causing any change in the medium.

Further, sb was selected as the low melting point metal, and a sputtered film of polyimide resin containing sb was examined, and it was confirmed that it exhibited good optical recording characteristics.

Example 3 A sputtered film was formed on an acrylic resin substrate by using Te as the low melting point metal in the medium and selecting polyamideimide instead of polyimide resin as the dispersion medium. Although polyamide-imide resin is not like polyimide resin, it has excellent heat resistance and flexibility. Te is used as a sputtering target.
A composite of powder and polyamide-imide resin was used. The sputtering conditions are: gas pressure 4X10"
A thin film with a thickness of about 100 nm was produced by spuntering at Torr and RF power of 7 for 10 minutes. When the laser recording characteristics were measured using this as an optical recording medium, the characteristics shown in FIG. 1 were slightly shifted toward lower power and shorter pulse width. That is, while the darkness value at which amorphous Te crystallizes in the as-prepared state shifted to the left in FIG. 1, the darkness value at which the recording medium deforms also shifted slightly to the left. Therefore, in terms of preventing deformation, Example 1
Although it is inferior to , it is an improvement in terms of the darkness value of laser recording.

We also investigated the optical recording properties of sputtered films containing low-melting point metals using polyimide resin or polyphenyl sulfide resin as a dispersion medium.

It was also confirmed that crystallized and amorphous regions existed in the medium depending on the laser irradiation conditions, although there were differences in degree, and it was found that writing and erasing of information using a laser beam was possible.

It seems strange that when a sputtered film is produced using a plastic having a relatively complex structure as described above as a base material, the film obtained has excellent heat resistance just like the base material. Although the cause of this is not clear (13) (12), it can be estimated as follows.

It is generally said that in sputtering, the target material is evaporated in an atomic or monomeric state.

However, these evaporated substances may repolymerize when passing through the discharge plasma, and a thin film having a structure similar to the target material may be formed on the substrate. Therefore, it is presumed that the plastic thin film according to the present invention has a structure similar to, if not the same as, that of the target material, and as a result, it has excellent heat resistance.

As explained above, since the optical recording medium according to the present invention contains plastic with excellent heat resistance, it can be used as a practically usable rewritable medium.

Furthermore, since the method for producing an optical recording medium according to the present invention uses sputtering, which is a simple and easy method with good controllability, the process is simple and can be expected to reduce costs when mass producing optical recording media. There is.

Therefore, the optical recording medium and its manufacturing method according to the present invention can be effectively applied as a technique (14) for providing a large-capacity file memory.

[Brief explanation of the drawing]

Fig. 1 shows the results of optical recording using the Te-containing sputtered film according to the present invention as an optical recording medium by changing the laser power and pulse width, and Fig. 2 shows the laser power of a conventional optical recording medium. , is a diagram showing the results of optical recording with varying pulse widths. Applicant's agent Masaki Amemiya (15) Figure 1 101001000 HA6NOSUYU (n5ec)

Claims (1)

[Claims] (1) A thin film of heat-resistant plastic made of polyimide resin, polyamide resin, polyamide-imide resin, or polyphenylene sulfide resin containing one or more low-melting point metals such as tellurium, bismuth, and antimony is deposited on the substrate. optical recording medium. (21) one or more low melting point metals such as tellurium, bismuth, and antimony; a type of heat-resistant plastic selected from the group consisting of polyimide resin, polyamide resin, polyamideimide resin, and polyphenylene sulfide resin;
1. A method for producing an optical recording medium, which comprises forming a sputtered film of a heat-resistant plastic containing a low melting point metal on a substrate by sputtering.