JPH07169095A - Information recording medium - Google Patents

Abstract

PURPOSE:To improve adhesiveness of a thin film for forming a recording layer and to enhance durability of an information recording medium by providing an oxide layer on a boundary between the recording layer and a reflecting layer. CONSTITUTION:The figure shows an information recording medium for independently recording and reproducing on both surface of a disk. The medium recording layers 9a, 9b for recording recording information by condensing and casting a laser light on boards 1a, 1b and reflecting layers 6a, 6b having a high reflectively for the light on the recording layers. Thus, the light is condensed to the recording layer thereby to vary reflectivity of the recording layer by generating low-melting-point alloy. Main ingredients of the layers 9a, 9b are antimony, selenium. The layers 6a, 6b contain aluminum. The recording layer is exposed to an oxygen atmosphere to form oxide layers 5a, 5b made of antimony oxide on the boundary between the recording layer and a reflecting layer. Thus, adhesiveness between the recording layer and the reflecting layer are improved and durability of the medium is enhanced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an information recording medium suitable for application to various image files such as video discs and digital audio discs and a large-capacity memory. The present invention relates to a (DRAW) type information recording medium.

[0002]

2. Description of the Related Art As a conventional information recording medium, a low melting point metal thin film layer formed on a substrate is irradiated with laser light modulated by a recording information signal, and the metal thin film layer is locally heated according to the information. By heating or heating the amorphous recording layer without melting or vaporizing a recording pit to form a recording pit, that is, recording by changing the shape, or recording mode by changing the shape. There is known a recording medium in which a crystallized recording portion is partially formed and recording and reading are performed by the difference in optical characteristics between the crystallized recording portion and the amorphous portion (for example, Japanese Patent Laid-Open Publication No. Sho. 5
No. 2-138,145).

However, in the former recording medium, a large power is required for writing, and it is difficult to control the shape of the recording pit generated by melting, so that the noise level becomes high and the resolution is low, so that high density recording is performed. There was a problem that it was not suitable. Also, the latter one,
In order to crystallize, it is necessary to record under conditions of slow heating and slow cooling, but when performing high-speed and high-density recording, the recording conditions are rapid heating and rapid cooling. There is a risk that crystallization will not occur. On the contrary, if a material that is easily crystallized under conditions of rapid heating and rapid cooling is used,
There is a problem that the amorphous part is gradually crystallized during a long-term storage and the S / N ratio is lowered.

Therefore, a first metal layer having a high transmittance for the laser light is formed on the substrate, and the first metal layer having a high absorptivity for the laser light is formed on the first metal layer. A recording medium having a second metal layer containing a low melting point metal as a main component, which easily forms an alloy with the above metal layer, has been proposed (for example, Japanese Patent Application Laid-Open No. 60-28,045 filed by the present applicant). (See the official gazette). In this case, the first metal layer can be composed of, for example, antimony selenium Sb ₂ Se ₃ , and the second metal layer can be composed of, for example, bismuth tellurium Bi ₂ Te ₃ . Further, a heat insulating layer and a reflecting layer are further formed on the first and second metal layers, and the heat insulating layer has a low thermal conductivity and a high laser beam transmittance, for example, antimony selenium S.
In addition to being composed of b ₂ Se ₃ , the reflective layer may be composed of a material having a large difference in refractive index and absorptivity from the heat insulating layer such as aluminum Al so that the reflectance with respect to the laser beam at the interface with the heat insulating layer becomes large. it can.

In such a recording medium, the thickness of the first metal layer is selected so that the reflectance thereof is low with respect to the laser light incident from the substrate side by utilizing the interference effect due to the multiple repeated reflection. As a result, when the laser light is focused and irradiated, the first metal layer, the second metal layer, and a part of the reflective layer become an alloy in which four elements are mixed, and when the conditions of the multiple repeated reflection are changed, the substrate is changed. Since the substantial reflectance of the recording layer viewed from the side changes, information can be recorded and read. Moreover, since the recorded contents are not erased by the magnetic field of the surrounding environment unlike the conventional magnetic recording, it is attracting attention as a medium capable of storing the recorded information for a long time.

[0006]

However, on the substrate,
Nchimon Selenium Sb₂Se₃A first metal layer consisting of
Sumasteru Bi₂Te₃A second metal layer consisting of
Chimon Selenium Sb₂Se ₃Insulation layer made of aluminum
A reflective layer made of aluminum and an ultraviolet curable resin
Two protective layers formed in the same way
Bond the board with the protective layer as the bonding surface via an adhesive,
The recording medium is configured so that recording / reading can be performed from the surface.
In case of antimony selenium Sb₂Se₃Insulation layer consisting of
At the interface with the reflection layer made of aluminum Al
There was a problem with the fit.

That is, the two substrates are joined by attaching a double-sided adhesive tape as an adhesive to the protective layer of each substrate, peeling off the mount of the double-sided adhesive tape, and then laminating the respective double-sided adhesive tapes. However, there is a problem that when the backing of the double-sided adhesive tape is peeled off, the backing does not separate from the double-sided adhesive tape and peeling occurs at the interface between the heat insulating layer and the reflective layer. It is presumed that such a problem of adhesiveness is caused by deterioration over time without using the double-sided adhesive tape. The present invention has been made in view of such problems of the conventional art, and an object of the present invention is to improve the adhesion of a thin film forming a recording layer.

[0008]

In order to achieve the above object, the information recording medium of the present invention condenses and irradiates the laser light onto a substrate through which the laser light modulated according to the recording information signal is transmitted. By forming a recording layer for recording the recording information on the recording layer, forming a reflective layer having a high reflectance with respect to the laser light on the recording layer, and converging and irradiating the recording light with the laser light. In an information recording medium for generating a melting point alloy to change the reflectance of the recording layer viewed from the substrate side, an oxide layer made of an oxide is formed at an interface between the recording layer and the reflecting layer. I am trying.

The recording layer is made of antimony selenium (Sb ₂ S
e ₃ ) as a main component, and the reflective layer is made of aluminum (A
It is preferable to use l) as a main component. The thickness of the oxide layer is preferably 10 nm or more.

[0010]

[Operation] The main component of the recording layer is antimony selenium (Sb ₂ S
e ₃ ), the reflective layer is mainly aluminum (Al), and the recording layer is exposed to an oxygen atmosphere to expose antimony oxide (Sb ₂ O) at the interface between the recording layer and the reflective layer.
_{When the} oxide layer composed of ₃ ) is formed, the adhesion between the recording layer and the reflective layer is improved. However, if the thickness of this oxide layer is less than 10 nm, no improvement in adhesion is observed, so the thickness is preferably 10 nm or more.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 (A) is an overall sectional view showing an optical disc according to an embodiment of the present invention, and FIG. 1 (B) is an enlarged sectional view showing part B of FIG. 1 (A). In this embodiment, element bodies a and b capable of independently recording information on both main surfaces of the disc and reading the recording from the same side on which the information is recorded are provided, The recording capacity of one information recording medium is doubled. However, the present invention is not limited to this embodiment, and the element body may be formed only on one surface.

The substrates 1a and 1b of the two elements a and b are made of polycarbonate resin or acrylic resin having a high transmittance for laser light for recording and reading, and guide the laser light when molding these substrates. Grooves 10a, 10b
Is formed. Recording layers 9a and 9b are formed on the surface on which the guide groove is formed.

The recording layers 9a and 9b of this embodiment are the substrate 1
first metal layers 2a and 2b directly formed on a and 1b,
The second metal layers 3a, 3 formed on the first metal layer
b and the heat insulation layers 4a, 4a formed on the second metal layer.
any of the layers 2a, 2b, 3a, 3
b, 4a, 4b can also be formed by sputtering, vacuum evaporation, electron beam evaporation, or the like.

The first metal layers 2a and 2b are sufficiently transparent to the laser light used and the second metal layer 3 is used.
It is composed of a material that easily alloys with a and 3b,
For example, antimony selenium Sb ₂ Se ₃ can be exemplified. On the other hand, the second metal layers 3a and 3b are low melting point metals that sufficiently absorb the laser light used, and are alloyed with the first metal layers 2a and 2b to form the first metal layers. Materials that can change the optical properties (eg, reflectance) of, eg, tellurium T
e, a low melting point metal such as bismuth Bi, antimony Sb, or indium In, or a low melting point compound containing these elements. When using a semiconductor laser having a wavelength band of 680 to 800 nm, for example, bismuth Bi, bismuth tellurium Bi ₂ Te ₃ or the like can be used as the second metal layers 3a and 3b.

The second metal layers 3a and 3b are formed of 10
It is preferably formed with a film thickness of nm to 50 nm. On the other hand, the film thicknesses of the first metal layers 2a and 2b are the same as those of the interface between the first metal layer and the substrates 1a and 1b and between the first metal layer and the second metal layers 3a and 3b. As a result of the interference of repeated multiple reflections that occur between the interfaces, the reflectivity is small when the laser light is irradiated from the substrate side, and the laser light is efficiently absorbed in the second metal layer. It However, it is advantageous that the reflectance is small in order to increase the absorption efficiency of the recording laser light, but in order to stabilize the operation of the laser light autofocus or the autotracking mechanism in the recording / reproducing apparatus, the detection light has a certain level. Since the reflectance is required, it can be said that the reflectance in the unrecorded state is preferably about 10 to 20%.

The heat insulating layers 4a and 4b formed on the above-mentioned second metal layers 3a and 3b are made of a material having a low thermal conductivity, for example, antimony selenium Sb similar to the first metal layers 2a and 2b. It can be composed of ₂ Se ₃ . The recording layers 9a and 9b in the present embodiment are the first metal layers 2a and 2b, the second metal layers 3a and 3b, and a part of the heat insulating layers 4a and 4b (portions adjacent to the second metal layer. ), The laser light is emitted from the substrate side and focused on the recording layer, so that the laser light is emitted from the second metal layer 3
a and 3b are efficiently absorbed and converted into heat, which melts the first metal layer, the second metal layer, and a part of this heat insulating layer, and thereby the antimony, selenium, bismuth, and tellurium
Produces alloys of elemental metals. The alloy generated by the irradiation of the laser light (that is, the recording portion) has different optical characteristics such as the reflectance as compared with the metal layer that is not irradiated with the laser light (that is, the unrecorded portion). Recording and reading can be performed by utilizing the difference of.

The thickness of the heat insulating layers 4a and 4b is the same as that of the second layer after a part of the light that has been irradiated from the substrate side and transmitted through the second metal layers 3a and 3b is reflected by the reflecting layers 6a and 6b which will be described later. Selected to function to return to the metal layer of
Depending on the thickness of the heat insulating layers 4a and 4b, the reflectance of the laser light from the substrate side will differ due to the interference effect of multiple reflection. Therefore, the reflectance of the entire recording layer is 10 to 20% or more, which is necessary to obtain the servo signals for the above-described autofocus and autotracking, and the difference in reflectance between the recorded portion and the unrecorded portion is large. Further, it is necessary to select the film thickness of the heat insulating layer such that the absorptance of the second metal layers 3a and 3b is high. For example, when the first metal layer (antimony selenium) has a thickness of 30 nm, the second metal layer (bismuth tellurium) has a thickness of 15 nm, and the heat insulating layer is made of antimony selenium and the reflecting layer is made of aluminum, The thickness of the heat insulating layers 4a and 4b is preferably selected to be about 120 to 150 nm in consideration of the above-mentioned conditions.

On the other hand, the reflective layers 6a and 6b according to this embodiment.
Is made of a material whose refractive index and absorption coefficient are largely different from those of the heat insulating layer so that the reflectance of the laser beam at the interfaces with the heat insulating layers 4a and 4b is high.
Examples are silver and gold. The thicknesses of the reflective layers 6a and 6b are selected within a range in which the amount of laser light passing through the reflective layers and leaking to the outside is sufficiently small and can be ignored. The reflective layers 6a and 6b can also be formed by sputtering, vacuum evaporation, electron beam evaporation, or the like.

"7a, 7b" is a protective layer for protecting the optical disc, especially the reflective layers 6a, 6b in the manufacturing process, and is made of, for example, resin or the like. However, when the resin is cured by heating, thermal distortion or the like is generated in the recording layers 9a and 9b and the substrates 1a and 1b, which is not preferable. Therefore, in this embodiment, a photocurable resin such as an ultraviolet curable resin is used. In the present invention, it is not always necessary to provide the protective layer, and the reflective layers of both the element bodies can be directly bonded to each other.

Both element bodies a and b thus formed
Are bonded by the adhesive layers 8a and 8b. In this embodiment, the double-sided adhesive tapes are attached to the protective layers 7a and 7b of the respective element bodies, and the double-sided adhesive tapes are adhered to each other to form the two element bodies a. , B are joined. However,
The method is not limited to this method, and the two elements may be joined using various adhesives.

Particularly, in this embodiment, the above-mentioned heat insulating layer 4a,
Oxide layers 5a and 5b are formed between the insulating layer 4b and the reflection layers 6a and 6b to improve the adhesion between the heat insulation layer and the reflection layer. When the heat insulating layers 4a and 4b are made of antimony selenium and the reflective layers 6a and 6b are made of aluminum, the oxide of antimony Sb (for example, S
It is preferable to form the layers 5a and 5b made of b ₂ O ₃ ). Such an antimony oxide is formed by forming the heat insulating layers 4a and 4b made of antimony selenium by sputtering, and then exposing the heat insulating layers 4a and 4b once in an oxygen atmosphere.
Alternatively, it can be performed by introducing oxygen into a vacuum. As the oxide, an oxide of selenium (for example, Se
O ₂ ), etc. were also considered, but from the experimental results described later, antimony oxides (eg Sb ₂ O ₃ ) were found to be used for adhesion.
Was confirmed to be effective.

Further, the heat insulating layers 4a and 4b and the reflecting layers 6a and 6
When the oxide layers 5a and 5b are formed between the oxide layers 5b and 5b, the adhesion is not improved if the thickness is less than 10 nm, as will be apparent from the experimental results described later.
It is desirable to set it to nm or more.

Examples will be described below in which the present invention is further embodied, but the specific numerical values in the following examples do not limit the present invention in any way. EXAMPLE About 30 nm antimony selenium layer (first metal layer), about 15 nm angstrom bismuth tellurium layer (second metal layer), and 140-148 nm antimony selenium layer by sputtering on a substrate molded from polycarbonate. After each (heat insulating layer) was laminated, it was exposed to an oxygen atmosphere having an oxygen O ₂ partial pressure of 7 × 10 ⁻³ Pa to form an oxide layer of 10 nm or more on the heat insulating layer. Further, about 10 is deposited on the oxide layer by sputtering.
An aluminum layer (reflection layer) having a thickness of 0 nm was formed, and then a protective layer was formed using an ultraviolet curable resin to obtain an element body of one of the optical discs shown in FIG. Comparative Example One element was manufactured under the same conditions as the above-mentioned example except for the oxide layer. That is, it is an element body in which a heat insulating layer is formed under the same conditions as in the embodiment, and a reflective layer is continuously formed without being exposed to an oxygen atmosphere.

First, the chemical bonding state at the interface between the heat insulating layer and the reflective layer of each of the examples and the comparative examples was analyzed by ESCA (photoelectron spectroscopy) to clarify the substance occurring at the interface. For ESCA analysis, ULVAC-PUI ESCA5400M is used as an analyzer.
C is used, the degree of vacuum is on the order of 10 ^-8 Pa, and X-ray is Mg
Kα (15kV, 400W), photoelectron escape angle is 45
The measurement was carried out at an analysis diameter of 1.1 mmφ. The antimony 3d spectra of Examples and Comparative Examples are shown in FIG.
The selenium 3d spectra of Examples and Comparative Examples are shown in FIG.

From these results, as shown in FIG. 3, the binding energies associated with the selenium element are 55e in both Examples and Comparative Examples.
Since a peak appears in the vicinity of V, it is understood from the diagram of FIG. 4B that selenium exists as a simple metal.
However, as shown in FIG. 2, regarding the antimony element, the comparative example has a peak near 528 eV, whereas the example shows a peak near 530 eV. This is because, as is clear from FIG. 4A, in the comparative example, antimony existing at the interface is a simple metal, whereas in the interface of the example, antimony is antimony oxide Sb.
It suggests that it exists as ₂ O ₃ . Further, according to the results of the following peeling experiment, since the example is extremely excellent in terms of adhesion, it is preferable that the oxide layer formed between the heat insulating layer and the reflective layer is an oxide of antimony. I can say.

Next, the element body thus prepared is
When 20,000 sheets were prepared and a double-sided adhesive tape was attached to each protective layer and the backing of the double-sided adhesive tape was peeled off, it was not between the backing and the double-sided adhesive tape but between the heat insulating layer and the reflective layer. When the ratio of the sample peeled off was verified, the results shown in Table 1 were obtained. As is clear from this result, it is understood that the adhesion performance is improved about 5 times when the oxide layer is formed between the heat insulating layer and the reflective layer.

[0027]

[Table 1] Number of sheets peeled off at the interface between the heat insulating layer and the reflective layer Defect rate Example 12 sheets 0.12% Comparative example 60 sheets 0.60%

Further, in order to verify the amount of oxides present at the interface between the heat insulating layer and the reflective layer using the samples in which peeling did not occur in the above-mentioned examples and the samples in which peeling occurred in the comparative examples, argon Ar was used. ESCA is performed by gradually etching in the depth direction with ion etching using ⁺ gas.
(Photoelectron spectroscopy analysis) It analyzed. The results are shown in FIG. 5, where (A) shows the analysis result of the example and (B) shows the analysis result of the comparative example. In the example, an oxide layer having a thickness of about 25 nm is formed, whereas in the comparative example, an oxide slightly oxidized by the sputtering atmosphere or the like is about 10 n.
Although it has a thickness of about m, this sample has a problem of adhesion so that peeling occurs between the heat insulating layer and the reflective layer, and thus the oxide layer needs to have a thickness of at least 10 nm or more. To be understood.

It should be noted that the embodiments described above are described for facilitating the understanding of the present invention and not for limiting the present invention. Therefore, each element disclosed in the above-described embodiments is intended to include all design changes and equivalents within the technical scope of the present invention.

[0030]

As described above, according to the present invention, since the oxide layer is formed at the interface between the recording layer and the reflective layer, the adhesion performance at the interface is remarkably improved and the durability as an information recording medium is improved. Will increase.

[Brief description of drawings]

FIG. 1A is an overall sectional view showing an optical disc according to an embodiment of the present invention, and FIG. 1B is an enlarged sectional view showing a B portion of FIG.

FIG. 2 is a spectrum diagram showing ESCA analysis results (antimony) on the peeled surfaces of the example and the comparative example.

FIG. 3 is a spectrum diagram showing an ESCA analysis result (selenium) on a peeled surface of an example and a comparative example.

4A is a diagram showing binding energies of antimony and its compounds, and FIG. 4B is a diagram showing binding energies of selenium and its compounds.

5A is a graph showing the relationship between the oxide layer thickness and the oxide amount according to the example, and FIG. 5B is a graph showing the relationship between the oxide layer thickness and the oxide amount according to the comparative example. .

[Explanation of symbols]

 a, b ... Element body 1a, 1b ... Substrate 2a, 2b ... First metal layer 3a, 3b ... Second metal layer 4a, 4b ... Thermal insulation layer 5a, 5b ... Oxide layer 6a, 6b ... Reflection layer 7a, 7b ... Protective layer 8a, 8b ... Adhesive layer 9a, 9b ... Recording layer

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location B41M 5/26

Claims (3)

[Claims] 1. A recording layer for recording the recording information is formed by converging and irradiating the laser light on a substrate through which the laser light modulated according to the recording information signal is transmitted, and the laser is formed on the recording layer. Form a reflective layer with high reflectance for light,
In the information recording medium, which generates a low melting point alloy by performing focused irradiation of the laser beam on the recording layer to change the reflectance of the recording layer viewed from the substrate side, the recording layer and the reflection An information recording medium, wherein an oxide layer made of an oxide is formed at the interface with the layer. 2. The recording layer comprises antimony selenium (Sb ₂ S).
e ₃ ) as a main component, and the reflective layer is made of aluminum (A
The information recording medium according to claim 1, characterized in that l) is a main component. 3. The information recording medium according to claim 1, wherein the oxide layer has a film thickness of 10 nm or more.