JP2900862B2 - Phase change optical disk - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical information recording / reproducing medium used for a rewritable optical information recording / reproducing apparatus and the like. The present invention relates to an optical information recording / reproducing medium in which a structural change between crystalline materials and optical properties change, that is, a phase change optical disk.

[0002]

2. Description of the Related Art An optical disk recording system using a laser beam is capable of large-capacity recording and non-contact high-speed access.
Optical disks are classified into a read-only type, which is known as a compact disk or a laser disk, a write-once type, which can be recorded by the user himself, and a rewritable type, which can repeatedly record and erase on the user side. Write-once and rewritable optical disks are about to be used as an external memory of a computer or as a document / image file.

[0003] As rewritable optical disks, there are a phase change optical disk utilizing a phase change of a recording film and a magneto-optical disk utilizing a change in the magnetization direction of a perpendicular magnetization film. Of these, the phase-change optical disk does not require an external magnetic field and can be easily overwritten, so that it is expected that the rewritable optical disk will become the mainstream in the future.

A rewritable, so-called phase-change type optical disk using a recording film which causes a phase change between crystal and amorphous by irradiation with a laser beam has been conventionally known. A phase-change optical disk irradiates a high-power laser beam spot according to the information to be recorded on the recording film, and locally raises the recording film temperature to cause a phase change between crystal and amorphous. Recording is performed, and reproduction is performed by reading a change in the optical constant accompanying the change as reflected light intensity difference with a low power laser beam.

For example, in a phase change optical disk using a recording film having a relatively slow crystallization time, the disk is rotated,
The recording film formed on the disk is irradiated with laser light to raise the temperature of the recording film to a temperature equal to or higher than the melting point, and after the laser light passes, is rapidly cooled, thereby recording the portion in an amorphous state. At the time of erasing, the recording film is crystallized by maintaining the recording film temperature in a crystallization-possible temperature range from the crystallization temperature to the melting point and lower than the crystallization temperature for a period sufficient for crystallization to proceed. As a method for this, there is known a method of irradiating a long oval laser beam in a laser beam traveling direction. In the case of performing pseudo overwriting by two beams for recording new information while erasing already recorded data, the erasing elliptical laser light is arranged to be irradiated prior to the recording circular laser light. .

On the other hand, a disc using an information recording film capable of high-speed crystallization uses a single laser beam focused in a circular shape. Conventionally known methods perform crystallization or amorphization by changing the power of laser light between two levels. That is, by irradiating the recording film with laser light having a power capable of raising the temperature of the recording film to a temperature equal to or higher than the melting point, most of the recording film becomes amorphous upon cooling, while the recording film temperature is crystallized. Above temperature,
A portion irradiated with a laser beam having a power to reach a temperature equal to or lower than the melting point is in a crystalline state.

[0007] The recording film of the phase change type optical disk is made of a chalcogenide-based material such as GeSbTe-based or InSbTe-based.
System, AgInSbTe system, InSe system, InTe system, A
sTeGe system, TeOx-GeSn system, TeSeSn
A system, a SbSeBi system, a BiSeGe system, or the like is used, and all are formed by a film forming method such as a resistance heating vacuum evaporation method, an electron beam vacuum evaporation method, and a sputtering method. The state of the recording film immediately after film formation is a kind of amorphous state, and in order to perform recording on this recording film and form an amorphous recording portion, an initialization process for making the entire recording film crystalline. Is performed. Recording is achieved by forming amorphous portions in this crystallized state.

Conventionally, as a technique for performing high-density recording on a phase-change optical disk, a mark edge recording method for recording information at the edge of a recording mark has been proposed. As a disk configuration suitable for mark edge recording, a disk configuration using a transmission-type reflective film, particularly a Si reflective film, has already been proposed (for example, JP-A-2-218834, JP-A-6-230671, JP-A-6-230671). 253326).

In the configuration of the Si reflection film, an ultraviolet curing resin (UV resin) is applied on the Si reflection film for protection. Alternatively, a UV resin is applied on the dielectric interference layer on the Si reflection film for protection. However, UV resin has a weak adhesive force to Si or a dielectric material, and therefore, a configuration in which UV resin is directly applied has insufficient characteristics in terms of weather resistance and repeated overwrite resistance. was there. The protective resin plays a role of minimizing mechanical deformation or thermal deformation of each thin film at the time of overwriting of the phase change optical disk, and is very important for ensuring the reliability of the phase change optical disk.

Conventionally, this type of phase change type optical disk generally has a configuration shown in FIGS. FIG. 3 is a schematic cross-sectional view showing a configuration of a conventional phase change optical disk, and FIG. 4 is a schematic cross-sectional view showing a configuration of a conventional phase change optical disk provided with an interference film. 3 and 4, reference numerals 31 and 41 denote substrates, 32 and 42 are base protective films, 33 and 43 are phase change recording films, 34 and 44 are upper protective films, and 35 and 45 are transmissive reflective films. , 37 and 47 are protective resins, and 48 is an interference film.

In order to test the effect of the conventional phase change type optical disk, a base protective film 32, a phase change recording film 33, and an upper protective film 3 are formed on a substrate 31 so as to have the same configuration as that of FIG.
4. The transparent reflective film 35 and the protective resin 37 were sequentially formed.
As the substrate 31, a polycarbonate substrate having a diameter of 130 mm (plate thickness 1.2 mm, track pitch 1.2 μm) was used. On this substrate 31, ZnS-
Under protective film 32 (260 nm thick) made of SiO ₂ , Ge ₂ Sb ₂
Phase change recording film 33 made of Te ₅ (15 nm thick), ZnS-Si
An upper protective film 34 (20 nm thick) made of O ₂ and a Si permeable reflective film 35 (20 nm thick) were formed. And ultraviolet curing resin (manufactured by Dainippon Ink, SD301, 10 μm thickness)
Was formed as a protective resin 37 by spin coating.

Subsequently, at 90 ° C., 9 to confirm the effect.
0% R. H. (Relative humidity) accelerated test in a high temperature and high humidity environment. In the test up to 1000 hours, the peeling of the protective resin 37 which is an ultraviolet curable resin was partially observed.

Next, in order to test the effect of the conventional phase-change type optical disk provided with an interference film, an underlayer protective film 42 and a phase-change recording film 43 are formed on a substrate 41 so as to have the same configuration as that shown in FIG. , Upper protective film 44, transmissive reflective film 45, interference film 4
8. A protective resin 47 was sequentially formed. As the substrate 41, a polycarbonate substrate having a diameter of 130 mm (plate thickness 1.2 mm,
Track pitch 1.2 μm). On this substrate 41, sequentially by sputtering, base protective film 42 (260 nm thick) made of ZnS-SiO _2, a phase change recording film 43 (15 nm thick) made of Ge ₂ Sb ₂ Te _5, a ZnS-SiO ₂ Upper protective film 44 (20 nm thick), and a Si permeable reflective film 45 (20 n
interference film 48 (120 nm thick) made of ZnS-SiO ₂
Was formed. Then, a UV-curable resin (manufactured by Dainippon Ink, SD301, 10 μm thick) was formed as a protective resin 47 by spin coating.

Subsequently, at 90 ° C. 9
0% R. H. (Relative humidity) accelerated test in a high temperature and high humidity environment. In the test up to 1000 hours, a phenomenon very similar to the effect test of the conventional phase-change optical disk having the same configuration as that of FIG. 3, that is, the peeling of the protective resin 47, which is an ultraviolet curable resin, was partially observed.

[0015]

As described above, it is very important from the viewpoint of the reliability of a phase change optical disc to enhance the adhesion between the protective resin and the functional thin film relating to the phase change recording characteristics. It is an issue.

An object of the present invention is to provide a phase-change type optical disk having a layer for enhancing the adhesion of a protective resin and having improved weather resistance and repetition resistance while having desired overwrite recording characteristics. .

[0017]

According to the phase change type optical disk of the present invention, information is recorded by the phase change of the information recording film which causes a reversible phase change between a crystal and an amorphous by irradiation of laser light. In a phase change optical disc on which recording / reproduction is performed, at least a transparent reflective film made of Si;
Protective resin, between the transparent reflective film and the protective resin
There is an adhesion strengthening layer consisting of a metal alloy ultra-thin film
And said that you are.

[0018]

The adhesion strengthening layer may be a metal alloy ultra-thin film containing Al as a main component. Furthermore, on the substrate,
An underlayer protective film, a phase change recording film, an upper protective film, a transmissive reflective film, an adhesion reinforcing layer, and a protective resin may be sequentially formed.

In the present invention, the structure between the protective resin and the functional thin film is improved by devising the structure of the phase change type optical disk, that is, by forming a metal alloy ultra-thin film as an adhesion reinforcing layer between the protective resin and the functional thin film. Is to enhance the adhesive force of the rubber. The inventors have found that the adhesive force between a metal and a protective resin typified by an ultraviolet curable resin is very strong, and have arrived at the invention. Conventionally, as a transparent reflection film, for example, Si
When the protective resin is used, the protective resin is formed on the Si reflective film, but the adhesive force between Si and the protective resin is not so strong, and by the formation of the adhesion reinforcing layer according to the present invention,
A great effect can be expected.

Further, on the substrate, a base protective film, a phase change recording film, an upper protective film, a transmissive reflective film, an interference film, an adhesion reinforcing layer,
The protective resin may be sequentially formed.

In a configuration in which an interference film is provided on a transmissive reflection film in order to improve performance by utilizing optical interference, even when a dielectric thin film is used as the interference film, S
As in the case of i, since the adhesion is required to be enhanced, an adhesion reinforcing layer is provided between the interference film and the protective resin. Since the adhesion reinforcing layer is an extremely thin metal alloy and is optically transparent or translucent, there is an advantage that even if the adhesion reinforcing layer is formed, there is almost no influence on the original optical characteristics of the disc, which is advantageous. Further, there is no thermal adverse effect such as a decrease in recording sensitivity due to the extremely thin film. The thickness of the metal alloy ultra-thin film is particularly preferably 10 nm or less.

[0023]

Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic cross-sectional view showing a configuration of a phase change optical disk according to a first embodiment of the present invention, and FIG. 2 is a schematic diagram showing a configuration of a phase change optical disk provided with an interference film according to a second embodiment. FIG. In FIGS. 1 and 2, reference numerals 1 and 21 denote substrates.
Reference numerals 2 and 22 denote a base protective film, and reference numerals 3 and 23 denote phase change recording films.
24 is an upper protective film, 5 and 25 are transmissive reflective films, 6, 26
Is an adhesion reinforcing layer, 7 and 27 are protective resins, and 28 is an interference film.

As shown in FIG. 1, a phase-change optical disk according to a first embodiment of the present invention has a
The phase change recording film 3, the upper protective film 4, the transmissive reflective film 5, the adhesion reinforcing layer 6, and the protective resin 7 are sequentially formed. The substrate 1 is made of disk-shaped glass or plastic. The lower protective film 2 and the upper protective film 4 are made of SiO ₂ , S
A material such as i ₃ N ₄ , AlN, TiO ₂ , ZnS or a mixture thereof is used. The phase change recording film 3 may be a chalcogenide-based material such as GeSbTe-based or InSb-based.
Te-based, AgInSbTe-based, InSe-based, InTe
System, AsTeGe system, TeOx-GeSn system, TeSe
Sn-based, SbSeBi-based, BiSeGe-based, and the like are used. As the transmissive reflection film 5, Si, G having a high refractive index is used.
e can be used. An extremely thin metal alloy is used for the adhesion strengthening layer 6. For example, Al, Au, Ag, Cr, C
u, Ni, Co, Ta, Ti, Pt, Pd and the like can be used. The adhesion strengthening layer 6 is desirably an Al or Al alloy ultra-thin film.
Al-Ti, Al-Si, Al-Ta, Al-Cu, A
1-Ni, Al-Co, Al-Cr and the like can be used.
As the protective resin 7, an ultraviolet curable resin that is generally cured by ultraviolet light is used.

In order to test the effect of the phase change type optical disk according to the first embodiment of the present invention, a base protective film 2 and a phase change recording film 3 are formed on a substrate 1 so as to have the same configuration as that of FIG. ,
An upper protective film 4, a transmissive reflective film 5, an adhesion reinforcing layer 6, and a protective resin 7 were sequentially formed. As the substrate 1, a polycarbonate substrate having a diameter of 130 mm (plate thickness 1.2 mm, track pitch 1.2 μm) was used. On this substrate 1, successively, by sputtering, a base protective film 2 made of ZnS-SiO ₂ (260n
m), phase change recording film 3 (15 nm) made of Ge ₂ Sb ₂ Te ₅
Upper protective film 4 (20 nm thick) made of ZnS-SiO ₂
Thickness), Si transparent reflection film 5 (20 nm thickness), Al-Ti
(Ti, 1.0 wt%)
Thickness). Then, an ultraviolet curable resin (SD301, 10 μm thick, manufactured by Dainippon Ink) was formed as a protective resin 7 by spin coating.

Next, in order to confirm the effects of the present invention,
90 ° C 90% R. H. (Relative humidity) accelerated test in a high temperature and high humidity environment. In the test up to 1000 hours, visual observation and evaluation at the bit error rate level were performed, but no abnormality was found.

Next, as shown in FIG. 2, a phase change type optical disc provided with an interference film according to a second embodiment of the present invention has a base protection film 22, a phase change recording film 23, an upper protection film on a substrate 21. Film 24, transmissive reflection film 25, interference film 28, adhesion reinforcing layer 2
6. The protective resin 27 is sequentially formed. Substrate 2
1 is a disc-shaped glass or plastic. SiO ₂ is used for the base protective film 22 and the upper protective film 24.
A material such as Si ₃ N ₄ , AlN, TiO ₂ , ZnS or a mixture thereof is used. As the phase change recording film 23, a chalcogenide-based material such as GeSbTe-based
SbTe system, AgInSbTe system, InSe system, InT
e system, AsTeGe system, TeOx-GeSn system, TeS
eSn system, SbSeBi system, BiSeGe system, etc. are used. As the transmissive reflective film 25, a high refractive index S
i, Ge, etc. can be used. For the adhesion strengthening layer 26, a metal alloy ultra-thin film is used. For example, Al, Au, Ag, C
r, Cu, Ni, Co, Ta, Ti, Pt, Pd and the like can be used. The adhesion strengthening layer 26 is desirably an Al or Al alloy ultra-thin film.
For example, Al-Ti, Al-Si, Al-Ta, Al-Cu, Al-Ni, Al-Co, Al-Cr and the like can be used. As the protective resin 27, an ultraviolet curable resin that is generally cured by ultraviolet light is used. The interference film 28 is preferably made of a transparent dielectric material and has a different optical constant from the transmissive reflection film 25. For example, SiO, Si, G
e, MgF ₂ , Al ₂ O ₃ , In ₂ O ₃ , ZrO _{2 and the} like can be used. By providing the interference film 28, performance can be improved such as enhancement of the reproduction signal level.

In order to test the effect of the phase change type optical disk provided with the interference film according to the second embodiment of the present invention, the undercoat protection film 2 is formed on the substrate 21 so as to have the same configuration as that of FIG.
2. A phase change recording film 23, an upper protective film 24, a transmissive reflective film 25, an interference film 28, and a protective resin 27 were sequentially formed. As the substrate 21, a polycarbonate substrate having a diameter of 130 mm (plate thickness 1.2 mm, track pitch 1.2 μm) was used.
On this substrate 21, ZnS—SiO ₂ was sequentially formed by sputtering.
Base protective film 22 (260 nm thick) made of Ge ₂ Sb ₂ Te ₅
Phase change recording film 23 (15 nm thick) made of ZnS, upper protective film 24 (20 nm thick) made of ZnS-SiO ₂ , Si transparent reflective film 25 (20 nm thick), interference film 28 made of ZnS-SiO ₂
(120 nm thick), Al-Ti (Ti, 1.0 wt%)
An adhesion strengthening layer 26 (2 nm thick) was formed. Then, an ultraviolet-curing resin (manufactured by Dainippon Ink, SD301, 1
(Thickness: 0 μm) as a protective resin 27 by spin coating.

Next, in order to confirm the effects of the present invention,
90 ° C 90% R. H. (Relative humidity) accelerated test in a high temperature and high humidity environment. In the test up to 1000 hours, visual observation and evaluation at the bit error rate level were performed, but no abnormality was found.

Although the embodiment of the present invention has been described with reference to the above-described configuration, the present invention is not limited to the above-described configuration, and is used for the purpose of broadly enhancing the adhesive force of a phase change optical disk. It is needless to say that the present invention is applied to an adhesion reinforcing layer.

[0031]

As described above, according to the present invention, in order to ensure the reliability of the phase change type optical disk, the adhesion reinforcing layer for enhancing the adhesion between the protective resin and the functional thin film is provided. Since the reinforcing layer is an optically transparent or translucent metal alloy ultra-thin film, it has almost no effect on optical characteristics and no thermal adverse effect, so it has desired overwrite recording characteristics, weather resistance, and repetition resistance. There is an excellent effect that can be improved.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view illustrating a configuration of a phase-change optical disc according to a first embodiment of the present invention.

FIG. 2 is a schematic cross-sectional view showing a configuration of a phase-change optical disc provided with an interference film according to a second embodiment of the present invention.

FIG. 3 is a schematic cross-sectional view showing a configuration of a conventional phase change optical disc.

FIG. 4 is a schematic cross-sectional view showing a configuration of a conventional phase-change optical disc provided with an interference film.

[Explanation of symbols]

 1, 21, 31, 41 Substrate 2, 22, 32, 42 Underlayer protective film 3, 23, 33, 43 Phase change recording film 4, 24, 34, 44 Upper protective film 5, 25, 35, 45 Transmissive reflective film 6, 26 adhesion strengthening layer 7, 27, 37, 47 protective resin 28, 48 interference film

Claims (4)

(57) [Claims] 1. A phase change type optical disk in which information is recorded / reproduced / erased by the phase change of an information recording film which causes a reversible phase change between a crystal and an amorphous by irradiation with laser light. At least a transparent reflective film made of Si, a protective resin, and an adhesion reinforcing layer between the transparent reflective film and the protective resin and made of a metal alloy ultrathin film are provided. Phase change optical disk. 2. The phase-change type optical disk according to claim 1, wherein said adhesion strengthening layer is a very thin alloy containing Al as a main component. 3. A phase-change optical disk in which information is recorded, reproduced, and erased by the phase change of an information recording film which causes a reversible phase change between a crystal and an amorphous by irradiation with laser light. On the substrate, a base protective film, a phase change recording film,
Upper protective film, permeable reflective film made of Si, ultra-thin metal alloy
A phase-change type optical disk characterized in that an adhesion reinforcing layer made of a film and a protective resin are sequentially formed. 4. A phase-change optical disc in which information is recorded, reproduced, and erased by the phase change of an information recording film which causes a reversible phase change between a crystal and an amorphous by irradiation with laser light. On the substrate, a base protective film, a phase change recording film,
Upper protective film, transparent reflective film made of Si, interference film, metal
A phase-change type optical disk characterized in that an adhesion strengthening layer composed of an extremely thin alloy film and a protective resin are sequentially formed.