JP2001006213A - Optical recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress deformation of a substrate and to prevent corrosion of a transparent dielectric layer and a recording layer, oxidation and deformation of the recording layer and deterioration of BER and the like. SOLUTION: The optical recording medium M2 has such layers mentioned below and successively film-formed by a magnetron sputtering method on the main surface of a transparent substrate which has a disk-like shape having a 3.5 inch diameter and consists of polycarbonate, that is, a deformation suppressing layer 12 having about 200 Åfilm-thickness and >=1.5×106 Kg/cm2 Young's modulus, a first transparent dielectric layer 13 having an about 1,000 Åfilm-thickness and containing >=70 mole % ZnS, a recording layer 14 having an about 200 Å film-thickness and made of Ge2, Sb2 and Te5, a second transparent dielectric layer 15 having an about 200 Å film-thickness and made of the same material as the first dielectric layer and a reflecting layer 16 having an about 1,000 Å film-thickness and made of an Al-Cr alloy.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording layer having a phase change between an amorphous state and a crystalline state according to the output of a light beam such as a laser beam to be irradiated. The present invention relates to a rewritable optical recording medium which records and reproduces digital information by utilizing the difference in reflectance of the optical recording medium.

[0002]

2. Description of the Related Art FIG. 3 is a partial sectional view of a conventional rewritable optical recording medium M1 utilizing a phase transition (hereinafter referred to as a medium M1). In FIG. 1, reference numeral 1 denotes a disk-shaped substrate made of a resin such as polycarbonate, glass, or the like;
First transparent dielectric layer made of S-SiO ₂ or the like, 3 GeT
e, a recording layer capable of phase-change into two states of amorphous or crystalline, 4 a second transparent dielectric layer made of ZnS-SiO ₂ or the like, 5 a reflective layer made of a high reflectivity material such as Al It is.

In such a rewritable medium M1, the recording layer 3 has a different light reflectance between a crystalline state and an amorphous state, and generally has a higher reflectance in the crystalline state. There are many. The operating principle of the medium M1 is as follows. First, all the recording bits of the recording layer 3 are crystallized. That is, initialization is performed in a state where the reflectance is high. For writing information, a laser beam pulse-modulated to two kinds of laser powers is irradiated while rotating the medium M1, and the recording layer is irradiated with a high-output (about 10 to 20 mW) laser beam. The material becomes higher than the melting points of the three materials, and is melted and rapidly cooled to become amorphous. on the other hand,
A recording bit irradiated with a laser beam of medium output (about 5 to 10 mW) is heated to a crystallization-possible temperature range equal to or lower than the melting point and then cooled to a crystalline state.

[0004] The above-mentioned writing operation can be performed directly after the old information remains, and each recording bit changes to a state corresponding to the new information. That is, overwriting by overwriting (Over Write, hereinafter abbreviated as OW) is possible. Reproduction is performed by irradiating a low-output (about 1 to 2 mW) laser beam for reading to determine whether the phase is a crystalline phase having a high reflectivity or an amorphous phase having a low reflectivity. read.

The material of the recording layer 3 is Te, S
A chalcogenide of a material containing one element of e and S is suitable, and the chalcogenide has a feature that it easily becomes amorphous. Specifically, GeTe-based materials, GeSbT
e-based materials, InSeTlCo-based materials, InSbTe-based materials, and the like.

Conventionally, such a phase change type medium M
In 1, an optical recording medium in which a phase-change optical recording layer is formed on a transparent substrate, in which the direction of cracks generated in the dielectric film exists in the radial direction, is defined as dielectrics A, in which cracks are generated. When dielectrics B exist in the circumferential direction, a dielectric film belonging to dielectrics A such as aluminum nitride and silicon carbide and a silicon nitride, zinc sulfide, etc. are provided between the transparent substrate and the optical recording layer. Or a composite dielectric film in which at least two dielectric films belonging to dielectrics A are laminated or at least two components of dielectric materials belonging to dielectrics B are mixed. As a result, a C / N ratio, BER, and the like are not deteriorated for a long time, cracks can be prevented, and long-term reliability is improved (conventional example 1: Japanese Patent Application Laid-Open No. Sho 62-42350). reference).

As a second conventional example, in an optical recording medium in which a first dielectric layer, a phase-change recording layer, a second dielectric layer, and a reflective layer are sequentially formed on a substrate, the first dielectric layer is 250
It has a thickness of at least nm and is mainly composed of oxides, nitrides, carbides or oxynitrides of Si, Ta, and Al, ZnS, ZnSe, a mixture of these compounds, or a complex compound of these compounds. Thus, a resin substrate is known in which even if rewriting of recording is repeated many times, the resin substrate is hardly damaged and the protective layer is hardly defective (see Conventional Example 2: JP-A-6-20301).

[0008]

However, in the above prior art example 1, it is difficult to suppress the erosion of moisture from the transparent substrate made of resin or the like to the dielectric film, and the deformation of the transparent substrate due to a change in environmental temperature and humidity. Effect was insufficient. In Conventional Example 2, the first dielectric layer is 250
Since the thickness is as thick as nm (2500 °) or more, there is a problem that the cost is increased.

Accordingly, the present invention has been completed in view of the above circumstances, and an object of the present invention is to suppress deformation of a substrate caused by changes in the temperature and humidity of the environment and to prevent erosion of moisture from the substrate. Accordingly, it is possible to prevent the recording layer from being oxidized and deformed, and to prevent the reflection layer from being peeled off. Further, it is not necessary to increase the thickness of the deformation suppressing layer, so that it can be manufactured at low cost.

[0010]

The optical recording medium of the present invention comprises:
A deformation suppressing layer having a Young's modulus of 1.5 × 10 ⁶ kg / cm ² or more is formed on the substrate, and the phase of the deformation suppressing layer changes to amorphous or crystalline according to the output of irradiation light. A recording layer, a transparent dielectric layer formed on at least one interface of the recording layer and containing at least 70 mol% of zinc sulfide, and a reflective layer are provided.

According to the present invention, a deformation suppressing layer having a Young's modulus equal to or higher than a predetermined value is formed in contact with the main surface of the substrate to suppress the deformation of the substrate caused by changes in environmental temperature and humidity. In addition, it has the effect of preventing oxidation and deformation of the recording layer, peeling of the reflection layer, and the like by preventing erosion of moisture from the substrate.

In the present invention, preferably, the deformation suppressing layer comprises a deformation suppressing component comprising at least one of aluminum oxide and zirconium oxide;
A high-adhesion component composed of at least one of magnesium oxide, yttrium oxide, and germanium nitride is a main component.

According to such a configuration, the deformation of the substrate and the erosion of moisture can be suppressed, and the adhesion between the substrate and the transparent dielectric layer is also improved. That is, the high adhesion component has toughness and a large bonding force with an organic substance, so that the adhesion between the substrate and the transparent dielectric layer is enhanced.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The medium of the present invention will be described below. The basic layer structure of the medium of the present invention is shown in FIGS. In the figure, reference numeral 11 denotes a disc-shaped transparent substrate made of polycarbonate, polyolefin, epoxy resin, acrylic resin, glass, tempered glass having a resin layer formed on the surface, translucent ceramics, or an opaque material such as Al ₂ O ₃ ; 12 is a deformation suppressing layer having a Young's modulus of 1.5 × 10 ⁶ kg / cm ² or more; 13 is a first transparent dielectric layer containing ZnS—SnO ₂ containing 70 mol% or more of ZnS—SiO ₂ ; Is a phase change type recording layer, 15 is a second transparent dielectric layer of the same material as the first transparent dielectric layer 13, 16 is Al, AlTi alloy, AlCr alloy, AlCu alloy, Au, Ag, AuCu having high reflectivity. The reflection layer is made of an alloy, Pt, AuPt alloy, or the like.

In the present invention, the recording layer 14 is made of GeTe,
Materials made of chalcogenides, such as GeSbTe, InSeTlCo, and InSbTe, are preferred.
GeSbTe is preferable because it can be rewritten a large number of times, can be crystallized in a short time when crystallized, and has high stability in an amorphous state.

[0016] In _{addition, Ge a Sb b Te c (} a + b + c =
100 at%), 5 at (atomic)% ≦ a ≦ 7
0 at% is good, and when a <5 at%, the crystallization speed is low,
When 70 at% <a, the amorphous state becomes unstable. 0at
% ≦ b ≦ 50 at% is good, and if 50 at% <b, the amorphous state becomes unstable. 40 at% ≦ c ≦ 70 at% is good, and if c <40 at%, the crystallization temperature becomes too high, and
Even when 0 at% <c, the crystallization temperature is too high. In particular, Ge ₂ Sb ₂ Te ₅ or GeSb ₂ Te ₄ is preferable. In this case, the crystallization speed is high and the erasing characteristics at a high linear velocity are good.

The thickness of the recording layer 14 is preferably 5 to 30 nm, and if it is less than 5 nm, the reflectance difference between the crystalline state and the amorphous state becomes small. Rate) and the like. More preferably, it is 10 to 20 nm.

The deformation suppressing layer 12 of the present invention has a Young's modulus of 1.0.
5 × 10 ⁶ kg / cm ² or more and 1.5 × 10 ⁶ k
If it is less than g / cm ² , the effect of suppressing local deformation of the substrate 11 will be small, and deformation of the recording layer 14 and peeling of the reflective layer 16 will easily occur. The measurement of the Young's modulus can be performed by a method of measuring an external force required for making a predetermined indentation on the deformation suppressing layer 12 by using a hardness meter.

The deformation suppressing layer 12 includes a deformation suppressing component composed of at least one of aluminum oxide (Al ₂ O ₃ ) and zirconium oxide (ZrO ₂ ) and silicon nitride (S).
i ₃ N _4), magnesium oxide (MgO), yttrium oxide (Y ₂ O _3), it is preferable that a main component and the high adhesion of components consisting of one or more of germanium nitride (GeN), the substrate 11 The deformation and erosion of the first transparent dielectric layer 13 and the recording layer 14 due to moisture from the substrate 11 can be suppressed, and the adhesion between the substrate 11 and the first transparent dielectric layer 13 is also improved. The deformation-suppressing component is preferably contained in an amount of 40 to 90 mol%. If the amount is less than 40 mol%, the deformation-suppressing effect is reduced. Is generated.

Further, the thickness of the deformation suppressing layer 12 is 50 to 50.
0 ° is good, and if it is less than 50 °, the deformation suppressing effect becomes too small, and if it exceeds 500 °, heat is easily stored in the entire medium, and heat radiation deteriorates.

The first transparent dielectric layer 13 and the second transparent dielectric layer 15 function as a protective layer and an intermediate layer of the recording layer 14, and are made of zinc sulfide (ZnS).
It contains 0 mol% or more. If it is less than 70 mol%, the refractive index becomes small, the effect of enhancing the reflected light from the recording layer 14 due to the light interference effect becomes small, and C / N
The ratio etc. deteriorates. The content of zinc sulfide can be analyzed by X-ray photoelectron spectroscopy (so-called ESCA), Auger electron spectroscopy, or the like.

The components that can be added to zinc sulfide include zirconium oxide (ZrO ₂ ), aluminum oxide (Al ₂ O ₃ ), silicon oxide (SiO ₂ , SiO),
Titanium oxide (TiO ₂ ), silicon nitride (Si ₃ N ₄ ), silicon carbide (SiC), titanium nitride (TiN), titanium carbide (TiC), aluminum nitride (AlN), tantalum nitride (TaN), zirconium carbide (ZrC) ), Yttrium oxide (Y ₂ O ₃ ), magnesium oxide (MgO),
Nickel oxide (NiO), boron oxide (B ₂ O ₃ ), chromium oxide (Cr ₂ O ₃ ), calcium oxide (CaO),
Antimony sulfide (Sb ₂ S ₃ ), tin selenide (SnSe)
₂ ), antimony selenide (Sb ₂ Se ₃ ), cesium fluoride (CeF ₃ ), titanium boride (TiB ₂ ), boron carbide (B ₄ C), B and the like are preferable. The addition of the substance improves the durability against repeated recording and reproduction.

The thickness of the first transparent dielectric layer 13 and the second transparent dielectric layer 15 is preferably 1 to 200 nm. If the thickness is less than 1 nm, the function as a protective layer is lost and it is difficult to form a uniform film. . If it exceeds 200 nm, the ability to follow the volume change of the recording layer 14 due to thermal expansion is deteriorated, and as a result, the characteristic deterioration such as BER for repeated recording / reproduction becomes large.

In the above embodiment, the configuration in the case where light is incident from the substrate 11 side has been described. However, as shown in FIG. 2, the present invention can be applied to a medium M3 in which light is incident from the recording layer 25 side. In the figure, 21 is a substrate, 22 is a deformation suppressing layer, 23 is a reflective layer, 24 is a second transparent dielectric layer,
Reference numeral 25 denotes a phase-change type recording layer, and reference numeral 26 denotes a first transparent dielectric layer. The order of film formation is different from that in FIG. 1, but the materials and thicknesses thereof are the same as those in FIG.

Thus, the optical recording medium of the present invention suppresses the deformation of the substrate caused by changes in the temperature and humidity of the environment,
In addition, the transparent dielectric layer and the recording layer are prevented from being eroded by moisture from the substrate, thereby preventing the recording layer from being oxidized and deformed, the reflection layer from being peeled off, and the adhesion to the substrate is further enhanced. Having.

In the present invention, the recording capacity may be doubled by laminating each of the above layers on both sides of the substrate 11 or by bonding two substrates 11 each having the above layers on one side of the substrate 11. Further, the present invention is not limited to the light intensity modulation method of pulse-modulating a laser beam,
A heating method using an energy beam such as an electron beam or an electromagnetic wave is also applicable. The media M2 and M3 of the present invention are phase-change rewritable optical disks, and are CD-RW (Compac
t Disc ReWritable), DVD-RW (Digital Versat)
ile Disc ReWritable).
Further, the media M2 and M3 of the present invention can be applied not only to disk-shaped media but also to card-shaped optical recording media.
1 is not necessarily required to be transparent as long as it has a structure like the medium M3.

It should be noted that the present invention is not limited to the above embodiment, and various changes may be made without departing from the scope of the present invention.

[0028]

Embodiments of the present invention will be described below.

(Embodiment) Medium M2 (optical disk) in FIG.
Was constructed as follows. The following layers were sequentially formed on the main surface of a 3.5-inch diameter disk-shaped transparent substrate 11 made of polycarbonate by magnetron sputtering.

Deformation suppressing layer 12 made of various materials (Table 1) having a thickness of about 200 Å, about 1000 膜厚 (ZnS)
_A first transparent dielectric layer 13 made of ₈₀ (SiO ₂ ) ₂₀ , a recording layer 14 made of Ge ₂ Sb ₂ Te ₅ ,
A second transparent dielectric layer 15 made of the same material as the first transparent dielectric layer 13;
The reflection layer 16 is made of an r alloy.

When the material of the deformation suppressing layer 12 is changed as shown in Table 1, the Young's modulus (kg
/ Cm ² ), BER when recording was performed once, 85 ° C.,
Table 1 shows the measurement results of the BER after leaving for 2000 hours in an environment of 95% RH (relative humidity). In addition, the measurement of BER was performed as follows. The linear velocity of the track of the optical disk is set to 6.18 m / s, and a laser beam pulse-modulated to 13 mW (corresponding to amorphous) and 5 mW (corresponding to crystalline) at an optical wavelength of 830 nm is recorded at 4.91 MHz. It is obtained from the reproduced signal intensity when reproducing with a 1 mW laser beam.

[0032]

[Table 1]

As shown in Table 1, the Young's modulus was 1.5 × 1
NO. ⁶ kg / cm ² or more. 1-5 and 1.5 × 10 ⁶
kg / cm ² less than the NO. Comparing with 6,7, N
O. In Nos. 1 to 5, the deterioration width of the BER was as small as 24.9 × 10 ⁶ or less. In Examples 6 and 7, the BER degradation range was very large, 388.3 × 10 ⁶ or more.

The NO. 1 containing 40 to 90 mol% of the deformation suppressing component was used. 8 to 19, and N outside the above range
O. 20 to 23, NO. In 8-19, B
While the deterioration width of ER was 8.2 × 10 ⁶ or less,
NO. In 20 to 23, it was as large as 11.6 × 10 ⁶ or more.

As described above, the present invention has a long life due to its excellent deformation suppressing power, adhesive strength and weather resistance, and as a result, deterioration of BER is reduced.

[0036]

According to the present invention, the Young's modulus is 1.5 × on the substrate.
A deformation suppressing layer of 10 ⁶ kg / cm ² or more is formed, and on the deformation suppressing layer, at least one interface between the recording layer and the recording layer that changes into an amorphous or crystalline phase according to the output of irradiation light. By providing the formed transparent dielectric layer containing at least 70 mol% of zinc sulfide and the reflective layer, deformation of the substrate caused by changes in the temperature and humidity of the environment is suppressed, and the transparent dielectric layer is formed by moisture from the substrate. By preventing erosion of the recording layer and the recording layer, oxidation and deformation of the recording layer, separation of the reflection layer, and the like are prevented, and furthermore, there is an effect that the adhesion between the substrate and the transparent dielectric layer is enhanced.

[Brief description of the drawings]

FIG. 1 is a partial sectional view of an optical recording medium M2 of the present invention.

FIG. 2 is a partial sectional view of an optical recording medium M3 of the present invention.

FIG. 3 is a partial cross-sectional view of a conventional optical recording medium M1.

[Explanation of symbols]

 1: substrate 2: first transparent dielectric layer 3: recording layer 4: second transparent dielectric layer 5: reflective layer 11: substrate 12: deformation suppressing layer 13: first transparent dielectric layer 14: recording layer 15: first Double transparent dielectric layer 16: Reflective layer

Claims (2)

[Claims] 1. The method according to claim 1, wherein the Young's modulus is 1.5 × 10 ⁶ kg /
forming a deformation suppression layer of at least ² cm2, and on the deformation suppression layer,
A recording layer that changes into an amorphous or crystalline phase in accordance with the output of the irradiation light, a transparent dielectric layer formed on at least one interface of the recording layer and containing at least 70 mol% of zinc sulfide, and a reflective layer. An optical recording medium characterized by being provided. 2. The deformation suppressing layer comprises a deformation suppressing component comprising at least one of aluminum oxide and zirconium oxide and a high adhesion component comprising at least one of silicon nitride, magnesium oxide, yttrium oxide and germanium nitride. 2. The optical recording medium according to claim 1, wherein