JPH02146120A - Optical recording medium - Google Patents

Abstract

PURPOSE:To enable rapid heating and cooling of local areas in a phase-shift type optical recording film, and to improve the erasing rate and record retaining property by sandwiching the recording film with heat-insulating films which are formed in a manner that the elements of the compounds constituting the recording film are gradedly change in the oxides into the heat-insulating films. CONSTITUTION:The heat-insulating film 5 comprising antimony oxide and indium oxide is formed on a substrate 1 with tracks 2 by sputtering on indium-antimony alloy as a target with supplying carrier gas containing large amount of oxygen. Then the amount of oxygen is reduced while the amount of indium antimony in the film 5 is raised to form the phase-shift type optical recording film 3 comprising indium antimony. Then the amount of oxygen gas is raised again to form the heat insulating film 5. The recording film thus formed between the heat-insulating films can be locally, rapidly heated or cooled by laser irradiation, which improves the erasing rate and record retaining property.

Description

[Detailed Description of the Invention] [Summary] Regarding improvements to improve the recording erasability and record preservation properties of rewritable optical recording media, a phase change optical recording device that has excellent both record erasability and record preservation properties is provided. A disk for the purpose of providing a medium, in which a groove forming a track along which information is written is formed on a substrate, and a phase change optical recording film is formed on at least the track. In the optical recording medium, at least one surface of the phase change optical recording film contains a compound forming the phase change optical recording film and an oxide of an element forming a constituent element of the phase change optical recording film. A heat shielding film is formed in which the content of the compound constituting the phase change optical recording film continuously decreases in response to the distance from the phase change optical recording film. It consists of an optical recording medium.

[Industrial application field]

TECHNICAL FIELD The present invention relates to improvements that improve the record erasability and record preservation properties of rewritable optical recording media.

[Conventional technology]

2. Description of the Related Art As a type of rewritable optical recording medium, an optical recording medium that utilizes a change in reflectance due to a phase change is conventionally known.

As shown in FIG. 2, the phase change optical recording medium uses a film 21 of ultraviolet curing resin or the like on a disk-shaped substrate 1 of glass or the like to form a head guiding track 2 of about 1.6 nm. an optical recording layer 3 made of indium antimony (In4sSbss) or the like is formed thereon, and a protective film 4 made of polyimide or the like is further formed thereon, or As shown in FIG. 3, the surface layer of a disc-shaped substrate 1 made of polycarbonate or the like is molded,
A head guiding track 2 is formed in a spiral or concentric shape with a pitch of about 1.6n, and an optical recording layer 3 is formed on it.
as indinium antimony (I nass bss
) or the like is formed, and a protective film 4 made of polyimide or the like is further formed thereon.

When writing on/off information, a pulsed optical signal such as a laser beam is irradiated in accordance with the on/off information to be written, and a layer of indium antimony or the like in an equilibrium state is transitioned to a metastable state. The reflectance of a layer such as indium antimony is low in an equilibrium state and high in a metastable state, so when reading on/off information, it is necessary to consider the strength of reflected light due to the difference in reflectance between the planar state and the metastable state. Detect and read on/off information.

In optical discs, the address area is not created accurately, so the linear velocity is constant.
(constant 1inear velocity
) type is commonly used. This linear velocity varies depending on the material of the information recording material, but in order to transition from an equilibrium state (low reflectance) to a metastable state a (high reflectance), an optical signal output of 10 mW is required.
, when the circumferential speed is about 6 m/s, and vice versa, the optical signal output is 3.
5 mW and a circumferential speed of about 2 m/s are generally used.

[Problem to be solved by the invention]

In optical recording media, both recording erasability and recording storage stability are extremely important characteristics. It goes without saying that it is important to have the ability to preserve records even at the highest temperature that can actually be expected, for example 60°C, but if the record erasability is not good, noise will be mixed into the information that will be written next. Therefore, recording and erasing properties are also extremely important characteristics. However, in phase-change optical recording media, erasability and archivability are antithetical, and it is necessary to realize a phase-change optical recording medium that is excellent in both erasability and archivability. This is not an easy task, and it has been desired for some time to realize an optical recording medium that is excellent in both phase-change recording erasability and recording storage performance.

An object of the present invention is to realize this request, and to provide a phase-change optical recording medium that is excellent in both recording erasability and recording storage performance.

[Means to solve the problem]

The above object is achieved by forming a groove forming a track (2) along which information is written on a substrate (1), and forming a phase change optical recording film (3) on at least the track (2). In an optical recording medium consisting of a disc on which a phase-change optical recording film (3) is formed, at least one surface of the phase-change optical recording film (3) contains a compound forming the phase-change optical recording film (3) and the phase-change optical recording film (3). The phase change optical recording film (3) is composed of a composition with an oxide of an element constituting the change optical recording film (3), and the phase change optical recording film This is achieved by an optical recording medium on which a heat shielding film (5) is formed in which the content of the compound constituting the film (3) is continuously reduced.

[Effect]

The inventor of the present invention proposed that erasing performance could be improved by rapidly heating and rapidly cooling only each localized bit area of the optical recording film when erasing records. I got an idea. In order to make this idea concrete,
We thought that it would be sufficient to cover one or both sides of the phase-change optical recording film with a film with poor thermal conductivity, and we applied it as a material with poor thermal conductivity on a substrate having grooves forming tracks. Various substances, such as silicon dioxide (SiOi)
, zinc sulfide (ZnS), etc. are selected and formed into a film, and on top of that,
Efforts were made repeatedly to form a phase-change optical recording film made of indium antimony (Inn5s bss) or the like.

However, at the interface between such materials with poor thermal conductivity, such as silicon dioxide (SiO2) and zinc sulfide (ZnS), and a phase change type optical recording film made of indium antimony (Inn5s bss), etc. Problems such as continuous surfaces and, in some cases, peeling occurring on these discontinuous surfaces occurred, and the above idea could not be realized.

Therefore, the inventors of the present invention believe that the generation of this discontinuous surface can be caused by materials with poor thermal conductivity, such as silicon dioxide (Stow).
), zinc sulfide (ZnS), etc. and indinium antimony (
In order to overcome the problem of insufficient chemical bonding force with I n4ss bsi) etc., a film of a substance with strong chemical bonding force with these two layers should be interposed between these two layers. In order to embody this idea, for example, when using the above-mentioned indinium antimony (I nass bss) as a phase change type optical recording film, for example, an alloy of indinium antimony In3sSbths is used as a target. When a phase-change optical recording film was formed using a sputtering method, and a large amount of oxygen was mixed into the carrier gas as the film was separated from the phase-change optical recording film, the above-mentioned problems were solved. No continuous surface was generated, and a heat shielding film with favorable characteristics could be formed.

In other words, a sputtering process is first carried out on a substrate having tracks, using a sputtering process targeting an alloy of, for example, indium antimony 1n15sbths, while supplying a carrier gas containing a large amount of oxygen. For example, a film of a composition of antimony oxide Sb*Oz and indium oxide Ingot is formed, and this is used as a heat shielding film, and the amount of oxygen gas supplied is gradually reduced to form a film formed as a heat shielding film. By increasing the amount of indinium antimony contained in the film, a phase change type optical recording film made of indinium antimony (r nasS bss) is finally formed using only indinium antimony.

Next, while gradually increasing the amount of oxygen gas supplied and reducing the amount of indium antimony formed, for example, antimony oxide sb, o, and indium oxide Inx
A film of the composition with Os is formed to form a heat shielding film.

In this way, the indium antimony phase-change optical recording film sandwiched between the formed heat shielding films has improved heat retention, so when it is irradiated with a laser for erasing, only local areas will rapidly rise in temperature. In addition, the erasure rate was improved by rapidly lowering the temperature, and the phase-change optical recording film did not change in temperature even if the outside temperature changed below a certain level, improving the storage stability of recording.

〔Example〕

Hereinafter, with reference to the drawings, the manufacturing process of a phase change type optical recording medium according to an embodiment of the present invention will be described. A groove forming track 2 with a pitch of 6n is formed.

Using a target made of an alloy of In5sSbis, while supplying oxygen gas at a pressure of IPa,
RF sputtering is carried out with a power of 00 mW. Through this process, a heat shielding film 5 of 100 nm thick is formed, which is made of a composition of SbgOs containing a large amount of 5bxOi and a somewhat small amount of In1Os, and In, O, etc. Oxygen is gradually converted to argon, and finally the entire amount is argon to form a phase change type optical recording film 3 made of indinium antimony and having a thickness of 100 nm.

Next, the amount of oxygen is increased again to produce 5btOs and IntOs containing somewhat more 5btOs and somewhat less IntOs.
, O, and has a thickness of 100n-〇 heat shielding film 5
form. It goes without saying that the change in composition between the above-mentioned lower heat shielding film and this upper heat shielding film is the best rule.

Finally, a protective film 4 made of polyimide or the like is formed.

When writing and erasing was carried out on the phase change optical recording medium manufactured by the above process at a linear velocity of 1.6 m/s, the writing laser intensity was 6 mW and the erasing laser intensity was 3 mW, and the medium functioned satisfactorily. The amount is 35
I checked the dB.

In addition, we conducted an accelerated deterioration test to confirm the storage stability of records by holding the record at the highest temperature that could actually be expected, for example, 85°C, which is much higher than 60°C. As shown in Figure 4, No changes were observed for at least 1,000 hours. In addition, in a similar accelerated deterioration test, the optical recording medium according to the conventional technology showed a decrease of approximately 40%! ! ! It was done.

Note that it is sufficient to provide the heat shielding film on one surface with good thermal conductivity, but it goes without saying that the effect will be even greater if it is provided on two surfaces.

〔Effect of the invention〕

As explained above, the phase change type optical recording film of the optical recording medium according to the present invention has at least its working surface composed of the compound constituting the phase change type optical recording film described above. Since it is sandwiched between the oxides of the elements that make up the elements with a graded heat shielding film, only the local area that is irradiated with the laser during erasing is rapidly heated and cooled. A sufficiently large erasure rate can be obtained, and at the same time, sufficiently large record retention characteristics can also be obtained. The reason for this is not necessarily clear, but due to the existence of the heat shield film, when erasing records, only the localized bit td region of the optical recording film rapidly rises in temperature and rapidly cools down. It seems that the performance will improve. Further, the reason why such characteristics are realized is considered to be that the compositional change between the heat shielding film and the phase change type optical recording film is graded, and there is no discontinuity between the eyebrows.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a phase change optical recording medium according to an embodiment of the present invention. FIG. 2 is a sectional view of an example of a phase change optical recording medium according to the prior art. FIG. 3 is a sectional view of another example of a phase change optical recording medium according to the prior art. FIG. 4 is a graph showing the results of an accelerated deterioration test of a phase change optical recording medium according to an example of the present invention. Substrate, track with groove, film of ultraviolet curable resin, phase change optical recording film, storage! ! membrane, a heat shielding membrane according to the subject matter of the present invention.

Claims (1)

[Scope of Claims] [1] A groove forming a track (2) along which information is written is formed on a substrate (1), and a phase change optical recording film is formed on at least the track (2). (3
), on at least one surface of the phase change optical recording film (3), a compound constituting the phase change optical recording film (3) and the phase change optical recording film (3) are formed. The phase change type optical recording film (3) is made of a composition with an oxide of an element constituting the optical recording film (3), and the phase change type optical recording film (3) An optical recording medium characterized in that a heat shielding film (5) is formed in which the content of a compound forming the structure continuously decreases.