JP2002050076A - Optical recording medium - Google Patents

Abstract

(57) [Summary] PROBLEM TO BE SOLVED: To be equivalent to a DVD-ROM as a large capacity medium
An optical information recording medium having an amount of recording density is provided. SOLUTION: The recording layer is composed of two layers and is adapted for laser beam irradiation.
Therefore, recording / reproducing by causing mutual diffusion between these two layers
Optical recording medium, wherein the two recording layers are made of different metals.
And expanded between the different metals up to 1000K.
Dispersion coefficient is 5 × 10 ^-Fivem^Two/ S or more.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical recording medium on which recording and reproduction can be performed by causing an optical change in a recording layer by irradiation with an energy beam.

[0002]

2. Description of the Related Art There are write-once optical recording media such as CD-R and DVD-R as recordable optical recording media by laser beam irradiation. These optical recording media are CD-ROM
Or, it is compatible with DVD-ROM and used as a small-scale distribution medium or storage medium, but has not reached the recording density of the same capacity as DVD-ROM which is a large-capacity medium. . Therefore, in order to spread the write-once optical recording medium widely, high-density recording can be performed, and it is particularly important to secure a recording power margin in high-density recording.

In order to secure a recording power margin at a high recording density, inorganic recording materials such as a phase change recording material and an alloyable two-layer film are advantageous, but these recording materials have insufficient reflectance. , Lack of modulation, or DPD (Differentiation) such as DVD-ROM
al Phase Detection) has a problem that the tracking signal intensity of a drive using the drive is insufficient.

[0004] For example, in an optical recording medium disclosed in Japanese Patent Application Laid-Open No. 6-171236, the recording layer is an Al-Ge double layer film,
Reflectance increases after heat treatment (low-to-high change)
There is a problem in performing ROM compatibility. That is, in order to realize ROM compatibility, the reflectance after recording film deposition (sputtering) is 40% or more, the reaction after heat treatment decreases (high-to-low change), and the above 60% It is necessary to obtain the above modulation. In addition, in the Al-Ge two-layer film, a desired mutual diffusion is not performed because the diffusion coefficient between the two elements is small, and the sensitivity is low.

Japanese Patent Publication No. 1-19451, 1-19
No. 453, No. 1-19454, No. 1-194
No. 55 and Japanese Patent Publication No. 1-194459, the optical recording medium is composed of In-Mo, Sn
-Pb, Sn-Au, Sn-Mo, Sn-Ge alloys, etc., but these recording layers have low reflectance and low to
It is not suitable for ROM compatibility for high change.

Further, Japanese Patent Publication No. 1-19450, Japanese Patent Publication No.
No. -19452 describes an optical recording medium whose recording layer is made of Sn—Cu or Sn—Zn, and is low to hi.
Although the recording is based on the change in gh, it is difficult to become a ROM-compatible recording medium because the reflectance is low or the modulation is low.

In the optical recording medium described in Japanese Patent No. 2538647, a recording layer, an optical interference layer, and an optical reflection layer are provided in order to increase the reflectance in an unrecorded state so as to cause a low-to-high change. However, the presence of the interference layer increases the number of steps for producing an optical recording medium, which leads to an increase in cost.

On the other hand, as a conventional recordable optical recording medium, a low melting point recording film such as Te or Bi provided on a substrate is irradiated with a laser beam to form a hole. There is known an optical recording medium for recording information by changing the reflectance of a recording film. In the method of recording information by forming these holes, a protective layer such as an ultraviolet-curable resin layer cannot be provided directly on the surface of the recording film, so there is a problem in storage stability, and a special substrate such as an air sandwich must be prepared. It had to be expensive and costly.

Further, Sb ₂ S _{3 is} used as a write-once type recording layer material.
It has been proposed to use (Japanese Unexamined Patent Publication No. 3-24153)
7, JP-A-3-240589, JP-A-3-2488
No. 84, JP-A-4-105226, JP-A-8-267
925). In the optical recording media in these proposals, S
Utilizing the low thermal conductivity of b ₂ S _3, the temperature is increased by heat storage in the recording laser beam irradiation section, thereby deforming the substrate to form recording pits. However, in these proposals, sufficient reflectivity has not been realized in a short wavelength range, and it has not been fully understood what conditions are suitable. Had become.

[0010]

As described above, each of the conventional optical recording media has its own problems. Further, a general problem is that if the reflectivity is increased, the recording layer can be reduced. The temperature is hard to rise, and the reflectivity is 40
% Of optical recording media having sufficient modulation and sensitivity have not been obtained.
An inorganic write-once optical recording medium having a recording density equal to that of OM has not been commercialized.

An object of the present invention is to provide an optical recording medium which has a sufficient reflectivity to be ROM compatible at the time of film formation, has high sensitivity and has a high modulation value under the circumstances, and is inexpensive. .

[0012]

As a result of intensive studies, the present inventors have found that the above problems can be realized by forming a recording layer satisfying the following conditions (1), (2) and (3). I found it. The present invention has been made based on this. (1) Two layers of different metals diffusing by heat are laminated. (2) The diffusion coefficient between these two different metals up to 1000 K is 5 × 10 ⁻⁵ m ² / s or more. (3) Preferably, the above (1) and (2) are added, and the film having the higher reflectance among the two layers is disposed on the energy beam irradiation side.

Therefore, according to the present invention, in an optical recording medium for recording / reproducing information by changing an optical constant of a recording layer by irradiating an energy beam, the recording layer is composed of two layers of different metals; 10 between these different metals
An optical recording medium characterized by having a diffusion coefficient up to 00K of 5 × 10 ⁻⁵ m ² / s or more is provided.

In the above-mentioned optical recording medium of the present invention, it is preferable that, of the two recording layers, a layer having a higher reflectance is arranged on the energy beam irradiation side. By employing such a layer configuration, a recording layer of an optical recording medium having a higher reflectance can be obtained.

Further, in the optical recording medium of the present invention, the two-layered recording layer is constituted by (a) a laminate of a layer containing Zn as a main element and a layer containing Sn as a main element; Pb
(C) A stack composed of a layer containing Pb as a main element and a layer containing Ni as a main element, and (d) Sn. (E) composed of a stack of a layer having Sb as a main element and a layer having Sb as a main element.
(F) A stack composed of a layer containing Ni as a main element and a layer containing Cr as a main element, and (f) a stack composed of a layer containing Ge as a main element and a layer containing Sn as a main element. It is preferable to form a stack of a layer containing Ni as a main element and a layer containing Mn as a main element, or (h) to form a stack of a layer containing Ni as a main element and a layer containing Mo as a main element. . By forming a two-layer recording layer with a combination of these two elements,
High reflectivity and modulation can be obtained.
RO with high sensitivity that allows writing with h to low behavior
A recording layer of an optical recording medium compatible with M can be obtained.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail. 1 and 2 show two typical examples of the optical recording medium of the present invention. In the example of FIG. 1, two recording layers are formed on a substrate, an ultraviolet curable resin layer is laminated on the recording layer, and a cover substrate is adhered on the ultraviolet curable resin layer by an adhesive layer. It has a structure. In the example of FIG. 2, a heat storage layer is provided between the recording layer and the ultraviolet curable resin layer in FIG.

As a material for the substrate (including the cover substrate), glass, ceramics, or resin is usually used, and a resin substrate is preferable in terms of moldability. Representative examples are polycarbonate, acrylic, epoxy, polystyrene, polypropylene, silicon, fluororesin, ABS,
Urethane and the like can be mentioned, but polycarbonate resin is preferable in view of workability, optical characteristics and the like. Further, the shape of the substrate may be a disk shape, a card shape, or a sheet shape.

The recording layer 1 and the recording layer 2 are preferably
n and Sn, Pb and In, Pb and Ni, Sn and Sb, Ge
And Sn, Ni and Cr, Ni and Mn, or a combination of Ni and Mo. The reason that two metals are used in such a combination is that the diffusion coefficient between these different metals up to 1000K is 5 × 10
^-5 m ² / s or more. Thereby, the recording layer composed of two layers has a high modulation,
Writing can be performed in a high to low behavior.

The heat storage layer is made of Ge, Te, Pb, Se, Sb,
Materials such as Bi and Sn are suitable. Since these materials have low specific heat and thermal conductivity, they do not spread heat in the plane direction of the heat storage layer or the recording layer, and contribute to improvement in sensitivity of the recording layer.

Both the recording layer and the heat storage layer of the present invention can be formed by various vapor phase epitaxy methods such as a sputtering method and an electron beam method. These film thicknesses cannot be unconditionally determined because the type of metal used is different. However, the recording layer 1 and the recording layer 2 each have a thickness of 100 to 400 °, preferably 2 °.
100 to 300 °, and the heat storage layer is 100 to 600 °, preferably 200 to 400 °.

The recording layer 1, the recording layer 2, and / or the heat storage layer may contain a low surface tension element in an amount of 20 atm% or less, preferably 5 to 10 atm%, if necessary. The low surface tension materials include those shown in Table 1. By adding these elements, the jitter value serving as an index for disc specification can be reduced. This is presumably due to the effect of reducing the surface tension of the material to clean the edges of the pits formed during recording.

[0022]

[Table 1]

The recording layer 1, the recording layer 2, and / or the heat storage layer may contain a rare earth element in an amount of 30 atm% or less, preferably 8 to 15 atm%, if necessary. In particular, it is effective to include a rare earth element in the heat storage layer. Rare earth elements have the effect of lowering thermal conductivity and specific heat. As shown in Table 2, many typical rare earths have very small thermal conductivity and specific heat, and even if these elements are contained in the recording layer 1, the recording layer 2, and the heat storage layer of the present invention. Characteristics such as reflectance are hardly degraded, and sensitivity can be improved.

[0024]

[Table 2]

UV curable resin layer (0.1-2 μm thickness)
Is formed by applying an ultraviolet-curable resin liquid onto the recording layer 2 by, for example, a spin coating method and irradiating ultraviolet rays. The cover substrate is stuck on the UV-curable resin layer using an adhesive to obtain the optical recording medium shown in FIG.

In the unrecorded state of the recording according to the present invention, the reflectance of the recording layer must exhibit a sufficiently high reflectance to be compatible with the ROM, and it is desired that the reflectance is 40% or more, which is the minimum value. On the other hand, if the reflectance is 75% or more, the recording, that is, the reflectance cannot be reduced even if the material such as the present invention has a thermal conductivity or a specific heat.

[0027]

Next, the present invention will be described in detail with reference to examples.

Example 1 A groove having a pitch of 0.74 μm, a depth of 400 °, and a thickness of 0.1 mm was used.
Zn (300 °) as the resin layer 1 of the present invention and Sn (300 °) as the recording layer 2 are sequentially laminated on a 6 mm, 120 mm diameter polycarbonate resin substrate by a sputtering method, and an ultraviolet curable resin liquid is spin-coated thereon. Thus, an ultraviolet curable resin layer (thickness: 1 μm) was formed by ultraviolet irradiation. Subsequently, the ultraviolet curable resin layer and the cover substrate (thickness: 0.6 mm) were adhered to each other with an adhesive layer, thereby producing an optical recording medium. The evaluation conditions were a recording linear velocity of 3.5 m / s, a linear density of 0.4 μm / bit, a wavelength of 635 nm, and an NA of 0.6.
It is. Table 3 shows the results of the diffusion coefficient, reflectance, modulation, and sensitivity of this optical recording medium. The diffusion coefficient was investigated in "Metal Handbook". In Table 3, 感 度: extremely good, ：: good, Δ: slightly poor, ×: bad.

Examples 2 to 8 Optical recording media were prepared in the same manner as in Example 1 except that the metals of the recording layers 1 and 2 were changed, and evaluated in the same manner as in Example 1. The results are summarized in Table 1.

[0030]

[Table 3]

Comparative Examples 1 to 8 The recording layer 1 was Ge (300 °), and the recording layer 2 was Al (300 °).
Å) A comparative optical recording medium was prepared in the same manner as in Example 1 except that
Create a body, which has its diffusion coefficient, reflectance, and modulation
Table 4 shows the results of the measurement and the sensitivity. Also the diffusion coefficient
Is 5 × 10^-Fivem ^Two/ S or less as a comparative example
Show.

[0032]

[Table 4]

[0033]

According to the first aspect of the present invention, in an optical recording medium for recording and reproducing information by irradiating a medium with a laser or the like to change the optical constant of the recording layer, the recording layer is different. It consists of two layers of metal and the diffusion coefficient between these different metals up to 1000 K is 5 × 10 ⁻⁵ m ²
By being at least / s, a high-sensitivity, ROM-compatible optical recording medium recording layer that has high modulation and can be written in a high-to-low behavior was obtained.

According to the second aspect of the present invention, by arranging the higher recording layer of the two recording layers on the laser side, an optical recording medium recording layer having a higher reflection ratio can be obtained.

According to the third to tenth aspects of the present invention, the recording layer of the optical recording medium is composed of two layers, that is, a layer composed of Zn and a layer composed of Sn. It was composed of two layers of a layer composed of Pb and a layer composed of Ni, composed of two layers of a layer composed of Sn and a layer composed of Sb, and composed of two layers composed of a layer composed of Ge and Sn composed of Sn. , Composed of two layers, a layer composed of Ni and a layer composed of Cr, composed of two layers composed of a layer composed of Ni and a layer composed of Mn, or composed of two layers composed of a layer composed of Ni and a layer composed of Mo As a result, a high-sensitivity, ROM-compatible optical recording medium recording layer having high reflectivity and modulation and capable of writing in a high-to-low behavior was obtained.

[Brief description of the drawings]

FIG. 1 is a view showing a typical example of an optical recording medium according to the present invention.

FIG. 2 is a diagram showing another typical example of the optical recording medium of the present invention.

Continuing from the front page (72) Inventor Takashi Shibaguchi 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Company (72) Inventor Yoshiyuki Kageyama 1-3-6 Nakamagome, Ota-ku, Tokyo Ricoh Company F term (for reference) 2H111 EA03 EA33 FA02 FB05 FB06 FB07 FB09 FB16 FB19 FB23 5D029 HA05 HA07 JA01 JB05 JB17 JC02 JC20

Claims (10)

[Claims] 1. An optical recording medium for recording / reproducing information by changing an optical constant of a recording layer by irradiation with an energy beam, wherein the recording layer comprises two layers of different metals,
An optical recording medium characterized in that the diffusion coefficient between these different metals up to 1000 K is 5 × 10 ⁻⁵ m ² / s or more. 2. The optical recording medium according to claim 1, wherein a layer having a higher reflectance among the two recording layers is provided on the energy beam irradiation side. 3. The optical recording medium according to claim 1, wherein the two recording layers are composed of a layer containing Zn as a main element and S
An optical recording medium comprising a stack of a layer having n as a main element. 4. The optical recording medium according to claim 1, wherein the two-layered recording layer comprises a layer containing Pb as a main element,
An optical recording medium comprising a stack of a layer having n as a main element. 5. The optical recording medium according to claim 1, wherein the two-layered recording layer comprises a layer containing Pb as a main element, and N
An optical recording medium comprising a laminate of a layer containing i as a main element. 6. The optical recording medium according to claim 1, wherein the two-layered recording layer comprises a layer having Sn as a main element,
An optical recording medium comprising a stack of a layer containing b as a main element. 7. The optical recording medium according to claim 1, wherein the two-layered recording layer includes a layer mainly composed of Ge,
An optical recording medium comprising a stack of a layer having n as a main element. 8. The optical recording medium according to claim 1, wherein the two-layered recording layer comprises a layer containing Ni as a main element, and C
An optical recording medium comprising a stack of a layer containing r as a main element. 9. The optical recording medium according to claim 1, wherein the two-layered recording layer comprises a layer containing Ni as a main element,
An optical recording medium comprising a stack of a layer having n as a main element. 10. The optical recording medium according to claim 1, wherein the two-layer recording layer includes a layer containing Ni as a main element;
An optical recording medium comprising a laminate of a layer containing Mo as a main element.