JPH0896413A - Phase change type information recording medium and its production - Google Patents

Abstract

PURPOSE: To form a reflecting layer having satisfactory oxidation resistance and to produce an information recording medium having stable characteristics. CONSTITUTION: A 1st dielectric protective layer 2, a phase change recording layer 3, a 2nd dielectric protective layer 4, a metallic reflecting layer 5 and a UV-curing resin layer 6 are formed on a substrate 1 to obtain the objective phase change optical disk. The reflecting layer 5 is formed as follows; a 1st metallic layer 7 of Al and a 2nd metallic layer 8 of at least one selected from among Ni, Ti, Co, Cr and Si are successively deposited by sputtering and a diffused alloy layer 9 is formed between the 1st and 2nd metallic layers 7, 8 by diffusing the element of the layer 8 in a part of the layer 7 close to the surface while depositing the layer 8 on the layer 7.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a phase change type information recording medium having a phase change type recording layer.

[0002]

2. Description of the Related Art As a recordable / erasable information recording medium, as shown in FIG. 3, a first dielectric protective layer 12, a phase change recording layer 13, and a second dielectric protective layer are provided on a substrate 11. Layer 1
There is a phase change type information recording medium in which 4, a metal reflection layer 15 and an ultraviolet curable resin layer 16 are sequentially laminated. Board 11
As a material for the above, transparent plastics such as acrylic and polycarbonate are used in terms of manufacturability and cost. Zn as the material of the first and second dielectric protective layers
S, SiO ₂ , Al ₂ O ₃ and mixtures thereof are used. GeSbT is used as the material of the phase change recording layer 13.
Chalcogenides such as e are used. Metal reflective layer 1
As the material of 5, a material having high reflectance and large thermal conductivity is desired, and Al, Au, or the like is used. Each of the above layers except the ultraviolet curable resin layer 16 can be formed by a deposition method such as a vacuum vapor deposition method or a sputtering method. The UV curable resin layer 15 is formed by spin coating a resin by a spinner,
Curing is performed by irradiation with ultraviolet rays.

When recording and erasing information by producing such a recording medium, first, the entire surface of the medium is irradiated with a light beam and heated at a temperature below its melting point to initialize the recording layer to a high crystallinity state. Turn into. Next, in order to record information, the medium is irradiated with a short intense pulsed light to heat, melt, and rapidly cool the recording layer,
An amorphous phase with reduced crystallinity is formed. Since the atomic arrangement is different between the crystalline state and the amorphous state, the optical characteristics such as transmittance and reflectance are different, and information is recorded by utilizing this difference in optical characteristics. To erase the recorded information, the recorded portion is irradiated with long and weak pulsed light to heat it at a temperature below the melting point of the recording layer, and then gradually cooled to cause a phase transition from amorphous to crystalline and erase information. Is done.

Further, by superimposing a strong and short pulse on a weak continuous laser power, the recording portion in the amorphous state is recrystallized to erase the recording mark, and at the same time, a new recording mark is formed, so-called overwriting. It can be performed. Generally, since a recording medium is manufactured as a product having a double-sided structure in which single plates are bonded together, information is reproduced by detecting a change in reflectance.

[0005]

By the way, the metal reflective layer has a thermal function as a heat sink in addition to an optical function as a reflective layer, and the recording layer heated above the melting point is rapidly cooled for recording. Amorphous recording marks are formed on the layer. Therefore, it is desired that the reflective layer has a high reflectance and a high thermal conductivity, and in consideration of the manufacturing cost, Al has a desirable characteristic as the reflective layer. Al is a commercially available compact disc (CD) for music or a CD-ROM (Read On) in which image / character information is filed.
It is used as an optical disk reflection layer such as ly Memory). The reproduction power of the optical disk is 1 of the recording power.
Since it is about / 10, in the case of the read-only optical disc as described above, the reflection film is not particularly damaged by the laser light irradiation.

However, in a phase-change optical disk in which recording / erasing is repeatedly performed, the recording layer reaches its melting point (several hundreds of degrees Celsius) or more during recording by irradiation with a laser beam having a recording power, which is higher than that of a read-only type. The reflective layer is subject to considerable thermal stress. An ultraviolet curable resin layer is provided on the reflective layer as a mechanical protection layer for the medium, but since it is a high molecular organic material, it is relatively easy for air and moisture to permeate as compared with inorganic materials, and the Al reflective layer is Even if the initial characteristics are good, there is a problem that deterioration such as oxidation occurs during repeated recording.

Generally, Ni, Ti, Co, Cr, Si
It is known that alloys of Al with elements selected from the above have excellent corrosion resistance, but these alloys cannot be directly used for the reflective layer of the phase change disk. This is because Al alone has good optical and thermal characteristics as initial characteristics, but the above-mentioned Al alloy contains elements other than Al at a concentration exceeding the impurity level.
This is because the thermal characteristics change and the desired characteristics as a reflective film for a phase change optical disk cannot be obtained.

Therefore, it is possible to improve the corrosion resistance of the Al reflection layer by providing the above-mentioned Al alloy layer on the outer surface of the Al layer. Since these alloys are high melting point substances, a sputtering method is generally used for film formation. The sputtering method is based on the principle that an inert gas such as Ar is ionized, a voltage is applied to collide with a target, and the atoms forming the target are repelled to form a film on a substrate at an opposing position. The number of target particles ejected per sputter gas particle (sputter yield) differs depending on the atom. Therefore, when the target is composed of a plurality of elements and the sputter yield is different, the composition of the formed film is different from the target composition. A similar tendency is observed for the above-mentioned Al alloy, and the film composition changes as the film formation is repeated, which makes it difficult to supply a disk having stable characteristics.

The present invention has been made in view of the above points, and an object of the present invention is to provide a phase change type information recording medium having a reflective layer having good oxidation resistance and having stable characteristics, and a method for manufacturing the same. To do.

[0010]

In order to solve the above-mentioned problems, according to the present invention, firstly, a phase change recording for recording information by causing a state change in a substrate and a portion irradiated with a light beam. A layer, a first dielectric protective layer provided between the substrate and the phase change recording layer, a second dielectric protective layer provided on the phase change recording layer, and a second dielectric protective layer provided on the phase change recording layer. A phase change type information recording medium having a metal reflection layer provided on a dielectric protection layer and a resin protection layer further provided on the metal reflection layer, wherein the reflection layer is made of Al. A first metal layer, a second metal layer made of at least one selected from Ni, Ti, Co, Cr and Si, and a first metal layer formed at a boundary portion between the first and second metal layers. And a diffusion alloy layer formed by diffusing the constituent elements of the second metal layer and A first metal layer formed on the dielectric protective layer side, the second metal layer is to provide a phase-change information recording medium, characterized in that formed on the resin protective layer side.

Second, on the substrate, the first dielectric protective layer,
A method for manufacturing a phase-change information recording medium, comprising forming a phase-change recording layer on which information is recorded by a change of a state caused by irradiation of a light beam, a second dielectric protective layer, a metal reflection layer, and an ultraviolet curable resin layer. The reflective layer is formed by sputtering,
First, a first metal layer made of Al and Ni, Ti, C
A second metal layer made of at least one selected from o, Cr, and Si is deposited, and a second metal layer is deposited on the first metal layer.
Forming a diffusion alloy layer between the first and second metal layers by diffusing the elements of the second metal layer into the surface vicinity layer of the first metal layer while depositing the first metal layer. And a method for manufacturing a phase change type information recording medium characterized by the above.

[0012]

In the phase change type information recording medium according to the present invention, the reflective layer has the first metal layer made of Al and Ni, Ti, C.
a second metal layer made of at least one selected from o, Cr, and Si, and a first metal layer and a second metal layer formed at a boundary portion between these first and second metal layers. It has a three-layer structure with a diffusion alloy layer formed by diffusing constituent elements. The diffusion alloy layer has good oxidation resistance, and the element forming the second metal layer has a higher oxidation resistance than Al. Therefore, the reflection layer is oxidized by the air or moisture passing through the resin protective layer. Is prevented. The reflective layer is formed by depositing a first metal layer made of Al on the second dielectric protection layer 13 by sputtering and then selecting from Ni, Ti, Co, Cr and Si. The sputtering of the target composed of the above-mentioned elements is started. The film-forming particles ejected from the target by sputtering collide with the substrate surface with a considerably large amount of energy. Therefore, after the first metal layer made of Al is formed, it is continuously selected from Ni, Ti, Co, Cr and Si. When sputtering a target composed of
The high-speed particles ejected from the target collide with the surface of the first metal layer and diffuse inside, forming a diffusion alloy layer of Al and the target material near the outer surface of the first alloy layer during film formation. It However, since the sputtered particles are attenuated in the first metal layer, their diffusion is limited to the vicinity of the surface of the first metal layer, and a sufficient film thickness for preventing oxidation cannot be obtained. Therefore, the sputtering is continued to further form the second metal layer made of the target material on the diffusion alloy layer. Since these target substances alone have relatively excellent corrosion resistance, the first metal layer made of Al is doubly protected by the diffusion alloy layer and the second metal layer. Therefore, the reflective film of the present invention has a three-layer structure as described above and has good oxidation resistance. Further, since the alloy layer for improving the oxidation resistance is a diffusion alloy layer formed by diffusion, there is little possibility that the characteristics of the information recording medium will change.

[0013]

Embodiments of the present invention will be described in detail below. FIG. 1 is a sectional view showing a phase change optical disk (phase change type information recording medium) according to an embodiment of the present invention. In this optical disc, a first dielectric protective layer 2, a phase change recording layer 3, a second protective layer 4, a reflective layer 5, and an ultraviolet curable resin layer (resin protective layer) 6 are formed in this order on a substrate 1. It has a layered structure.

The substrate 1 is made of a material that is transparent and does not change with time.
For example, acrylic resin such as polymethylmethacrylate (PMMA), polycarbonate resin, epoxy resin,
It is made of styrene resin or glass.

The dielectric protection layers 2 and 4 are arranged so as to sandwich the recording layer 2, and the recording layer 2 is irradiated with a recording beam.
However, it also has a role of preventing scattering and formation of holes, and a role of controlling heat diffusion of heating and cooling of the recording layer 2 at the time of recording. This dielectric protection layer 2, 4
Is SiO ₂ , SiO, AlN, Al ₂ O ₃ , Zr
It is composed of O ₂ , TiO ₂ , Ta ₂ O ₃ , ZnS, or a mixed material thereof. The thickness is preferably several nm to several μm.

The phase-change recording layer 2 is made of a material whose state changes when irradiated with a light beam, and information is recorded by utilizing this state change. Examples of such phase change materials include GeTe-based, TeSe-based, GeS
bSe system, TeOx system, InSe system, GeSbTe system,
A chalcogenide-based material such as InSb-based, GaSb-based, InSbTe-based can be used. This recording layer 2 is
It can be formed by sputtering or the like. The thickness of the recording layer 1 is preferably in the range of several nm to several μm.

The UV-curable resin protective layer 6 is provided to prevent scratches and dust when handling the optical disk. For example, UV-curable resin is applied to the surface of the reflective layer 5 by spin coating. It is formed by irradiating ultraviolet rays and curing.

The reflective layer 5, which is a feature of the present invention, has the first dielectric protective layer 4 and the ultraviolet curable protective layer 6 extending from the first dielectric protective layer 4 toward the ultraviolet curable protective layer 6.
3 has a three-layer structure in which the metal layer 7, the diffusion alloy layer 8, and the second metal layer 9 are sequentially formed. The first metal layer 7 is made of Al having desired optical and thermal characteristics as a phase change optical disk reflection layer, and the second metal layer is made of Ni, Ti, C.
It consists of at least one element selected from o, Cr and Si. The diffusion alloy layer 9 is formed at the boundary between the first and second metal layers and is formed by diffusing the constituent elements of the first metal layer and the second metal layer. The thickness of the reflective layer 5 is preferably several tens nm to several μm in total. The thickness of the diffusion alloy layer 9 is controlled by the diffusion of atoms during the sputtering after the formation of the first metal layer 7 as described later, and is about several nm.

Next, a method of manufacturing the phase change optical disc having the above-described structure will be described. The first dielectric thin film 2, the phase change recording layer 3, and the second dielectric protection layer 4 are sequentially formed on the substrate 1 by sputtering or the like commonly used in this field, and then the reflective layer 5 is formed. To be done. In the present invention, the reflective layer 5 is formed by using sputtering. In forming the reflective layer 5, first, the first metal layer 7 made of Al is deposited on the second dielectric protection layer 13, and then N is deposited.
Sputtering of a target made of an element selected from i, Ti, Co, Cr and Si is started. Generally, the film-forming particles ejected from the target by sputtering have a kinetic energy of ˜1 eV, and when converted into thermal kinetic energy (3/2) kT [k: Boltzmann constant, T: absolute temperature] of the particles. Then ~ 8000
Corresponding to the temperature of [k], it collides with the substrate surface with considerably large energy. Therefore, after forming the first metal layer 7 made of Al, Ni, Ti, Co, Cr, Si
When the target composed of the element selected from among the above is sputtered, the high-speed particles ejected from the target collide with the surface of the first metal layer 7 and diffuse into the inside thereof, and the first metal is deposited during the film formation. A diffusion alloy layer 9 of Al and a target material is formed near the outer surface of the layer 1. However, since the sputtered particles are attenuated in the first metal layer, their diffusion is limited to the vicinity of the surface of the first metal layer 7, and a sufficient film thickness for preventing oxidation cannot be obtained. Therefore, the sputtering is continued to further provide the second metal layer 8 made of the target material on the diffusion alloy layer 9. Since these target substances alone have relatively excellent corrosion resistance, the first metal layer 7 made of Al is doubly protected by the diffusion alloy layer 9 and the second metal layer 8. .
Therefore, the reflective film of the present invention has a three-layer structure as described above and has good oxidation resistance. Further, by forming the reflective layer as described above, it becomes possible to stably form the above-mentioned alloy layer 9 on the outer surface of the first metal layer 7 made of Al.

After the reflective layer 5 is formed in this manner, an ultraviolet curable resin is applied by a spinner and irradiated with ultraviolet rays to be cured to form an ultraviolet curable resin protective layer 6.

The recording / erasing of information on such a phase change optical disc is performed as follows. First, the entire surface of the disk is irradiated with a light beam and heated at a temperature equal to or lower than the melting point to initialize the phase change recording layer 2 to a state of high crystallinity. Next, in order to record information, a short intense pulsed light is applied to the disc to heat and melt and rapidly cool a desired portion of the recording layer 2 to form an amorphous phase with reduced crystallinity. . Since the atomic arrangement is different between the crystalline state and the amorphous state, the optical characteristics such as transmittance and reflectance are different, and information is recorded by utilizing this difference in optical characteristics. The recording is erased by irradiating the recorded portion with long and weak pulsed light and heating it at a temperature equal to or lower than the melting point of the recording layer 2. That is, the portion heated in this way is gradually cooled thereafter to cause a phase transition from amorphous to crystal, and information is erased.

Further, as shown in FIG. 2, by superimposing strong and short pulses on weak continuous laser power,
It is possible to perform so-called overwriting, in which the recording mark in the amorphous state is recrystallized to erase the recording mark and at the same time a new recording mark is formed.

Next, specific examples will be described. (Example 1) Here, the transparent substrate has a diameter of 130 mm,
A polycarbonate substrate having a thickness of 1.2 mm and a groove track pitch of 1.6 μm was used. A mixture of ZnS and SiO ₂ was used as the first and second dielectric protection layers, and the thickness of each layer was 180 nm and 20 nm, respectively. As the phase change recording layer, a Ge ₂ Sb ₂ Te ₅ 3 layer having a thickness of 30 nm is used.
The original compound was used. Each of these layers was formed by sputtering. Next, a reflective layer was formed. First, 100 nm thick Al was deposited as a first metal layer, and subsequently 100 nm thick Ni was deposited as a second metal layer. Al formed at the interface between the first and second metal layers
In order to examine the depth profile of the alloy layer, an Al layer and a Ni layer were sequentially deposited to a thickness of 100 nm on a Si substrate, and Auger electron spectroscopy analysis was performed. It was estimated that the alloy layer profile was several nm. It was For comparison, only Al is used as the reflection layer (thickness: 100 nm) as a conventional example.
The sample of was also produced. After forming the reflective layer, the UV curable resin layer was spin-coated with a spinner, and the resin layer was cured with an UV exposure device.

The sample provided with the reflection layer of the present invention and the conventional sample were subjected to an accelerated test under conditions of high temperature and high humidity of 70 ° C.-90% RH for 2000 hours, and the reflection of the unrecorded area before and after the test was performed. The signal and byte error rate were compared. The laser wavelength of the evaluation drive device is 830
nm, the objective lens NA is 0.55, the spindle motor rotation speed is 1800 rpm, and the disk radius is 45 mm.
The area was evaluated. When the reproduction signal level fluctuation before and after the acceleration test was observed on the basis of the zero reflection level of the reproduction laser light, almost no signal level fluctuation was observed in the sample provided with the reflective layer of the present invention, but the conventional sample The signal level was reduced by about 10%. The sample provided with the reflective layer of the present invention and the conventional sample are the same except for the reflective layer, and the reflectance fluctuation observed in the conventional sample after acceleration is caused by deterioration of the reflective layer.

Furthermore, 1-7 RLL (Run Length
When the length of the mark was recorded with random data coded by a thimated modulated code, the error rate was measured, and the same area was measured again after acceleration. As a result, almost no change was observed in the sample provided with the reflective layer of the present invention. No
The initial value (2 × 10 ^-5 ) was maintained. On the other hand, the error rate of the conventional sample after acceleration was approximately doubled.

[0026]

As described above, according to the present invention, there is provided a phase change type information recording medium having a reflection layer having good oxidation resistance, stable characteristics and high reliability, and a method for manufacturing the same. It

[Brief description of drawings]

FIG. 1 is a sectional view showing a phase change optical disk according to an embodiment of the present invention.

FIG. 2 is a principle diagram for explaining overwrite recording.

FIG. 3 is a sectional view showing the structure of a conventional phase change optical disc.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Substrate, 2 ... 1st dielectric protective layer, 3 ... Phase change recording layer, 4 ... 2nd protective layer, 5 ... Reflective layer, 6 ... Resin protective layer,
7 ... 1st metal layer, 8 ... 2nd metal layer, 9 ... Diffusion alloy layer.

Claims (2)

[Claims] 1. A substrate, and a phase change recording layer for recording information by causing a state change in a portion irradiated with a light beam,
A first dielectric protective layer provided between the substrate and the phase change recording layer, and a second dielectric protective layer provided on the phase change recording layer.
And a metal protective layer provided on the second dielectric protective layer, and a resin protective layer provided on the metal reflective layer. The reflective layer includes a first metal layer made of Al, Ni, T
At least one selected from i, Co, Cr, and Si
A second metal layer made of a seed, and a diffusion alloy layer formed at the boundary between the first and second metal layers and formed by diffusing the constituent elements of the first metal layer and the second metal layer. And the second metal layer is formed on the side of the resin protection layer, and the first metal layer is formed on the side of the dielectric protection layer. 2. A first dielectric protective layer, a phase change recording layer on which information is recorded by a change in state caused by irradiation of a light beam, a second dielectric protective layer, a metal reflective layer, and an ultraviolet curing layer on a substrate. A method of manufacturing a phase change type information recording medium, comprising forming a resin layer, wherein the reflection layer is formed by sputtering a first metal layer made of Al and Ni, Ti, Co, Cr, Si in order.
Of the second metal layer of at least one selected from among the first metal layer and the second metal layer is deposited on the first metal layer, and A method of manufacturing a phase-change information recording medium, characterized in that the element of the second metal layer is diffused to form a diffusion alloy layer between the first and second metal layers.