JP2003006928A - Optical recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical recording medium having high reliability in storage, good mechanical characteristics and high productivity and capable of high-speed recording. SOLUTION: (1) In the optical recording medium having a substrate, a light absorbing layer and a light reflecting layer, the average grain diameter Lc of the light reflecting layer, the minimum length Lm of a mark recorded and the thickness Lt of the light reflecting layer satisfy the relation of the formula Lt/4<=Lc<=Lm. (2) The light reflecting layer comprises Ag of >=99 wt.% purity containing 0.00005-0.005 wt.% metal having a lower standard electrode potential than Ag.

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 capable of recording / reproducing or rewriting information by causing an optical change in a light absorbing layer by irradiating a laser beam. In particular, CD-R media, CD-RW media, DV
D-R medium, DVD-RW medium, DVD + R medium, DV
The present invention relates to a CD-ROM or DVD-ROM compatible optical recording medium such as a D + RW medium.

[0002]

2. Description of the Related Art Magneto-optical media, CD-R media, CD-RW media, DVD-R media, DVD-RW media, DVD + R media, DVD + RW media as optical recording media capable of recording / reproducing or erasing by irradiation of laser light. , DVD-RO
M media and the like have been commercialized. In these optical recording media, higher density and higher linear velocity are expected to enable more information to be recorded faster,
As a solution, A with high reflectance and high thermal conductivity
The adoption of u, Ag, Cu, and Al-based light reflecting layers is under study. In particular, an Ag-based light reflecting layer having the highest reflectance and thermal conductivity among metals is expected.

When Ag is used as a light reflecting layer of an optical recording medium, the following merits A to F are expected. A. Improved medium reflectance in a wide wavelength range. B. Increased signal amplitude due to the optical properties of Ag. C. In the case of the light-reflecting layer of the phase-change type medium, the number of overwrites is improved due to the layer structure that is cooled more rapidly. D. In the case of the light reflection layer of the phase change type medium, the recording linear velocity is expanded by the layer structure that is more rapidly cooled. E. High productivity due to high sputtering efficiency. F. Reduction of thermal stress by shortening sputter film formation time (improvement of medium mechanical properties). On the other hand, when Ag is used as a light reflection layer of an optical recording medium, there are the following problems G to L. G. Easily corroded under high temperature and high humidity. H. Easily corroded by sulfur and chlorine. J. The film adhesion to the base is small. K. It is a noble metal and is more expensive than Al or the like. L. Abnormal mechanical properties due to Ag film stress when using a 0.6 mm thick substrate.

As a method of suppressing Ag corrosion, AgCu disclosed in JP-A-57-186244 and JP-A-7-3 can be used.
363, AgMg, JP 9-156224, AgOM (M: Sb, Pd, Pt), JP 2000
It is known to use an alloy of Ag as seen in AgPdCu of -285517. Also, patent 2
No. 749080, in order to control the thermal conductivity, Ag, Ti, V, Fe, Co, Ni, Zn, Zr,
Nb, Mo, Rh, Pd, Sn, Sb, Te, Ta,
It is disclosed that W, Ir, Pt, Pb, Bi, and C are contained. However, when these material systems are actually used for the light reflecting layer, the CD-R medium, the CD-RW medium, the D
When a VD-RW medium, a DVD + R medium, and a DVD + RW medium were manufactured and the recording signal was evaluated, sufficient reflectance and signal amplitude could not be obtained. This is because if Ag is added with 1 wt% or more of another metal, high reflectance and high thermal conductivity, which are characteristics of Ag, cannot be obtained. In addition, when the medium was evaluated for archival high temperature storage reliability at 80 ° C. and 85% RH, a rapid increase in errors was observed after storage for 300 hours, and the above disclosed material did not provide sufficient storage reliability. In the case of a substrate of a bonded type medium such as a DVD + RW medium, when a light reflection layer is formed on a substrate as thin as 0.6 mm, substrate deformation is induced by thermal stress and internal stress of the light reflection layer, and recording / reproduction is performed. Caused a problem.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an optical recording medium having high storage reliability, good mechanical properties, high productivity, and high-speed recording.

[0006]

[Means for Solving the Problems] The above problems are solved in the following 1) to
It is solved by the invention of 5) (hereinafter, referred to as the inventions 1 to 5). 1) In an optical recording medium having a substrate, a light absorbing layer, and a light reflecting layer, the average crystal grain size Lc of the light reflecting layer, the minimum mark length Lm to be recorded, and the film thickness Lt of the light reflecting layer are as follows: An optical recording medium characterized by the following relationship. Lt / 4 ≦ Lc ≦ Lm 2) The optical recording medium according to 1), wherein Lc, Lm, and Lt have the following relationship. Lt / 3 ≦ Lc ≦ Lm 3) The light-reflecting layer contains 0.00005 to 0.005 wt% of a metal having a standard electrode potential lower than Ag and a purity of 99 wt.
The optical recording medium according to 1) or 2), wherein the optical recording medium is composed of at least Ag. 4) Metals whose standard electrode potential is smaller than Ag are Al and B.
i, Ca, Cu, Cd, Fe, Mn, Mg, Ni, P
The optical recording medium according to 3), which is at least one selected from d, Pb, Sb, and Zn. 5) The optical recording medium according to 3) or 4), wherein a metal having a standard electrode potential lower than that of Ag is contained in the crystal grain boundaries of Ag and / or Ag alloy of the light reflecting layer.

The present invention will be described in detail below. As a result of diligent studies on the problems of the Ag reflective layer, in order to obtain a light reflectance of 90% or more, which is a characteristic of Ag, as a light reflective layer of an optical recording medium, the Ag content of the light reflective layer is 99 wt% or more. It has been found that the amount should preferably be 99.9 wt% or more. Further, the crystal grain boundaries of the light reflection layer of Ag and / or Ag alloy have thermophysical properties significantly different from the crystals of Ag or Ag alloy. Variation in the mark shape and the mark length (jitter) occurs depending on whether or not crystal grain boundaries exist in the light reflection layer in the portion where the recording mark is formed by light irradiation. FIG. 5 shows the relationship between the average crystal grain size Lc and Jitter (jitter) when recording is performed on the DVD + RW medium using the light reflection layer having various average crystal grain sizes Lc by the optimum recording strategy. The average crystal grain size Lc was set to a predetermined value by adjusting the substrate temperature, the film forming speed, and the film forming pressure. The minimum mark length Lm of the DVD + RW medium is 0.4 μm. From FIG. 5, it can be seen that when the average crystal grain size Lc of the light reflecting layer exceeds the minimum mark length 0.4 μm, the jitter of the recorded signal increases. This was the same result in any of the light reflection layers of Ag, AgPdCu, and AlTi. As characteristics, Ag, AgPd
The results were good in the order of Cu and AlTi. From the above knowledge, it is understood that it is necessary to satisfy Lc ≦ Lm.

The crystal grain size of the light reflecting layer affects the mechanical characteristics of the optical recording medium, especially the warp of the substrate. The mechanism is that when the light reflection layer is vacuum-formed and then exposed to the atmosphere, water vapor (water molecules) enters crystal grain boundaries to generate compounds such as oxides and undergoes volume expansion. Since water molecules enter, the rate of volume expansion differs between the surface of the light reflecting layer and the inside, and internal stress occurs. At this time, if the crystal grain size of the light reflection layer is large, the relaxation of the internal stress becomes small, so that the strain as the optical recording medium becomes large. For example, if the thickness of the light reflection layer and the size of the crystal grain size are approximately the same, the internal stress generated by water molecules is not relaxed, and tensile stress is generated in the substrate. On the other hand, when the crystal grain size is sufficiently smaller than the thickness of the light reflection layer, the internal stress generated by water molecules is relieved, so that tensile stress does not occur in the substrate. However, if the crystal grain size of the light reflecting layer is too small, the light reflectance and the thermal conductivity required for the light reflecting layer become small, which is not preferable. In order to prevent tensile stress from being generated in the substrate while maintaining the light reflectance and / or thermal conductivity required for the light reflecting layer, the average crystal grain size Lc of the light reflecting layer is equal to the film thickness Lt of the light reflecting layer. It should be ¼ or more (Lt / 4 ≦ Lc), preferably ⅓ or more (Lt / 3 ≦ Lc).

FIG. 6 shows the relationship between the ratio (Lc / Lt) of the average crystal grain size Lc to the film thickness Lt of the reflective layer and the modulation degree of the recording signal. The degree of modulation after recording is DVD-ROM, CD-R
Since the reproduction capability of the OM or the like is affected, a modulation degree of 55% or more, preferably a modulation degree of 60% or more is necessary to enable reproduction. As can be seen from FIG. 6, in order to realize the modulation degree of 55% or more or 60% or more, Lc is
/ Lt needs to be 1/4 or more, that is, Lt / 4 ≦ Lc, and 1/3 or more, that is, Lt / 3 ≦ Lc.

Further, in the phase change type optical recording medium, the optical reflection
Thermophysical properties and optical properties of the coating layer are important factors. For example
Protective layer ZnS / SiO on polycarbonate substrate
_Two(Film thickness 80 nm), recording layer AgInSbTe (film thickness 1
6 nm), protective layer ZnS / SiO _Two(Film thickness 20 nm),
Light in which reflective layers Ag-Cu (film thickness 140 nm) are sequentially stacked
Recording on the recording medium with laser light having a wavelength of 650 nm
As shown in Table 1, when the recorded signal characteristics are measured by performing live
Results are obtained. As can be seen from Table 1, the purity of Ag
Therefore, the size (modulation degree) of the recording signal greatly differs. one
, DVD-ROM, CD-ROM, etc.
To achieve this, the degree of modulation is 55% or more, preferably 60%
The above is necessary. Therefore, the purity of Ag is 99
wt% or more, preferably 99.9 wt% or more is required
And more preferably 99.99 wt% or more.

[0011]

[Table 1]

However, in consideration of the above requirements, the reflective layer has
When Ag having a high purity of 9 wt% or more was used, the high temperature and high humidity storage reliability became insufficient, and the medium reflectance decreased. Then, as a result of studying the mechanism of the decrease in reflectance, it was revealed that Ag is ionized and corroded when the sulfur source and the chlorine source come into contact with Ag in the presence of water (H ₂ O). This corrosion is due to the sulfur source reaching the Ag surface,
The chlorine source proceeds through the Ag grain boundaries using water as a medium. From the knowledge about such a mechanism, in the present invention, in order to prevent ionization of Ag, a metal having a standard electrode potential smaller than that of Ag is added to the extent that the intended light reflectance and thermal conductivity of Ag are not impaired. It was to be. Specifically, it was effective to add 0.00005 to 0.005 wt% of a metal having a standard electrode potential smaller than Ag with respect to Ag. As the additive metal, Al, Bi, Ca, Cu, Cd, Fe, Mn, Mg, which has excellent compatibility with Ag,
Ni, Pd, Pb, Sb and Zn are effective.

According to the Ag corrosion mechanism, if a metal having a standard electrode potential lower than that of Ag is present at the grain boundaries of the crystals of Ag and / or Ag alloy, the ionization of Ag can be effectively suppressed. In order to generate a metal having a standard electrode potential smaller than that of Ag at the grain boundary of Ag and / or Ag alloy, the Ag crystal in the film formation is sufficiently controlled by controlling the substrate temperature, the film formation speed, the film formation pressure, and the like. It is necessary to move the additive metal to the grain boundaries of Ag and / or Ag alloy while growing the metal. As the film forming conditions, when the substrate temperature is high, the film forming rate is high, and the film forming pressure is low, the added metal can be effectively generated at the Ag crystal grain boundaries. The light-reflecting layer is formed by various vapor deposition methods such as vacuum deposition method, sputtering method, plasma CVD method, photo CVD method, ion plating method,
It can be formed by an electron beam evaporation method or the like. The thickness of the alloy or metal layer is 50 to 200 nm, preferably 70.
It is preferable that the thickness is up to 160 nm. It is also possible to make the alloy or metal layer into multiple layers. In the case of multilayering, the thickness of each layer must be at least 10 nm or more, and the total thickness of the multilayered film is preferably 50 to 160 nm. When used as a semitransparent reflective layer of a multilayer recording layer, 10 to 50 nm is suitable.

1 to 4 show an embodiment of the present invention.
In the basic configuration of FIG. 1, a lower protective layer 2, a light absorbing layer 3, a first upper protective layer 4, an Ag light reflecting layer 6 and an overcoat layer 7 are preferably provided on a transparent substrate 1 having guide grooves. Is the
1 A second upper protective layer 5 is provided on the upper protective layer 4. Further, if necessary, a printed layer 8 may be provided on the overcoat layer, and a hard coat layer 9 may be provided on the mirror surface (back surface) of the substrate. FIG. 2 shows an example in which the above-mentioned single plate disc is laminated with the adhesive layer 10 interposed therebetween. The other party 11 to be bonded to the single plate disk may be the same single plate disk or only the transparent substrate. In addition, after a single plate disk having no printing layer is attached, a printing layer 8'may be formed on the opposite surface side (outermost surface side). Furthermore, the overcoat layer also serves as the adhesive layer,
It is also possible to have one layer. CD-R medium and DVD
In the case of the + R medium, it is better not to use the lower protective layer 2, the first upper protective layer 4, and the second upper protective layer 5 as shown in FIG.
It is desirable because sensitivity can be improved and cost can be reduced. Figure 4
3 has a structure in which the medium of FIG. 3 is laminated in the same manner as in FIG. In these optical recording media, irradiation with a semiconductor laser beam causes an optical change and / or a shape change in the light absorption layer to perform optical recording.

The material of the substrate is usually glass, ceramics, or resin, and a resin substrate is suitable in terms of moldability and cost. Examples of the resin include polycarbonate, acrylic resin, epoxy resin, polystyrene, acrylonitrile-styrene copolymer resin, polyethylene, polypropylene, silicone resin, fluorine resin, ABS resin, urethane resin, etc. Polycarbonate and acrylic resin, which are excellent in properties and cost, are preferable. However, the optical recording medium of the present invention is a DVD
In the case of application to a rewritable optical recording medium that is compatible with ROM, it is desirable to give the following specific conditions. That is, the width of the guide groove formed in the substrate to be used is 0.10 to 0.40 μm, preferably 0.15 to 0.35.
μm, and the depth of the guide groove is 15 to 45 nm, preferably 20 to 40 nm. The thickness of the substrate is preferably 0.55 to 0.65 mm, and the thickness of the disc after bonding is preferably 1.1 to 1.3 mm. By having such a substrate groove, a DVD-
Playback compatibility in the ROM drive is improved.

The optical information recording medium of the present invention is a CD-R.
When applied to W medium, the width of the guide groove is 0.25 to
0.65 μm, preferably 0.30 to 0.60 μm, and the depth of the guide groove is 20 to 50 nm, preferably 25 to 45 nm. The light absorption layer contains Sb and Te that can undergo a phase change between a crystalline phase and an amorphous phase and can be in a stable or metastable state, and the composition thereof is Sb _X T
e _100-X (X is atomic%), the phase change type recording material with 40 ≦ X ≦ 80 has a recording (amorphization) sensitivity / speed, an erasing (crystallization) sensitivity / speed, and an erasing ratio. It is preferable because it is good. This SbTe material has Ga, G
By adding elements such as e, Ag, In, Bi, C, N, O, Si, and S, recording / erasing sensitivity and signal characteristics,
The reliability can be controlled. The addition ratio of these elements is 0.1 to 20 at%, preferably 0.1 to 15 at%.
At% If less than 0.1%, the effect is small and 20a
If it is more than t%, initialization (crystallization) cannot be performed well.

As the phase change type light absorbing layer made of an alloy,
In addition to simply recording and erasing, signal reproduction stability and signal life (reliability) when recorded in a high density and high linear velocity region are also required. A composition formula (Ag and //
Or Ge) α (In and / or Ga and / or Bi) β
Those containing an alloy represented by SbγTeδ and having α, β, γ, and δ (atomic%) in the following ranges are excellent. 0.001 ≦ α / (α + β + γ + δ) ≦ 0.07 0.01 ≦ β / (α + β + γ + δ) ≦ 0.15 0.60 ≦ γ / (α + β + γ + δ) ≦ 0.90 0.15 ≦ δ / (α + β + γ + δ) ≦ 0 .30, more preferably a cubic lattice crystal structure in which the crystal structure in the unrecorded state after initialization is an isotropic crystal structure, preferably N
A material having an aCl-type crystal structure can undergo a phase change with less variation from an amorphous phase, which is also considered to have high isotropy, and performs recording (amorphization) and erasing (crystallization) at high speed and uniformly. Suitable because it can.

The thickness of the phase change type light absorbing layer made of an alloy is 1
The thickness is 0 to 50 nm, preferably 12 to 30 nm. Further, considering the initial characteristics such as jitter, overwrite characteristics, and mass production efficiency, the thickness is preferably 14 to 25 nm. 10
When the thickness is less than 50 nm, the light absorption ability remarkably lowers and does not play its role, and when the thickness is more than 50 nm, uniform phase change at high speed hardly occurs. Such a light absorption layer can be formed by various vapor phase growth methods such as vacuum deposition method, sputtering method, plasma CVD method, photo CVD method, ion plating method and electron beam evaporation method. Among them, the sputtering method is preferable because it is excellent in mass productivity and film quality. Further, as the dye-based light absorbing layer, a cyanine-based dye,
Pyrylium / thiopyrylium dyes, azurenium dyes, squarylium dyes, metal complex salt dyes such as Ni and Cr, naphthoquinone / anthraquinone dyes, indophenol dyes, indoaniline dyes, triphenylmethane dyes, triallyl Materials having absorption at a recording wavelength such as methane dyes, aminium-based / diimmonium-based dyes, nitroso compounds, azo-based dyes and phthalocyanine-based dyes, and mixtures thereof can also be used. Further, if necessary, a binder, a light stabilizer and the like can be contained.

The thickness of the dye-based light absorbing layer is 10 to 500 n.
m, preferably 50 to 300 nm. If the film thickness is too thin, the recording signal amplitude and recording sensitivity will decrease, and if the film thickness is too thick, the reflectance will decrease. Can be decided.
The dye-based light-absorbing layer is usually provided by dissolving the dye-based light-absorbing material in an organic solvent and spin-coating it. At that time, the rotation speed of spin-coating is controlled to control a predetermined film thickness. Other optical recording layers include FeT
A magneto-optical recording material such as bCo is used. Each of these various optical recording layers is preferably used as a single layer, but may be formed in multiple layers. At that time, with the dielectric layer interposed,
It is also possible to make the optical recording layer multi-layered. In the case of forming multiple layers, it is possible to form multiple layers of different light absorbing layers such as a phase change type light absorbing layer and a dye type light absorbing layer, and a phase change type light absorbing layer and a magneto-optical recording layer. By making these light absorption layers multi-layered, recording / reproduction can be performed in a heterogeneous optical recording device.

Materials for the lower protective layer and the first and second upper protective layers are SiO, SiO ₂ , ZnO, SnO ₂ and A.
metal oxides such as l ₂ O ₃ , TiO ₂ , In ₂ O ₃ , MgO, and ZrO ₂ ; Si ₃ N ₄ , AlN, TiN, BN,
ZrN and other nitrides; ZnS, In ₂ S ₃ , TaS ₄ and other sulfides; SiC, TaC, B ₄ C, WC, TiC,
Carbides such as ZrC; diamond-like carbon, or a mixture thereof. In the second upper protective layer,
Of C, Si, SiC, SiN, SiO, SiO ₂ ,
A material containing at least one substance is desirable. These materials may be used alone as the protective layer, or may be mixed with each other. Moreover, you may contain an additive as needed. However, the melting points of the lower protective layer and the first and second upper protective layers need to be higher than that of the recording layer. The lower protective layer and the first and second upper protective layers may be formed by various vapor deposition methods such as vacuum deposition method, sputtering method, plasma CVD method, photo CVD method, ion plating method, and electron beam evaporation method. Can be formed. Among them, the sputtering method is excellent in mass productivity and film quality.

The film thickness of the lower protective layer greatly affects the reflectance, the degree of modulation and the recording sensitivity. In order to obtain good signal characteristics, the thickness is preferably 60 to 120 nm. The thickness of the first upper protective layer is 5 to 45 nm, preferably 7 to 40 n.
m. When the thickness is less than 5 nm, the function as the heat resistant protective layer is not fulfilled and the recording sensitivity is lowered. On the other hand, when the thickness is more than 45 nm, interfacial peeling is likely to occur and the repetitive recording performance is also deteriorated. The thickness of the second upper protective layer is 1 to 20 nm, preferably 2 to 10 nm, and more preferably 3 to 7 nm. The second upper protective layer needs to function as a chemically inactive layer and / or a heat dissipation adjusting layer between the Ag-based light reflecting layer and the second upper protective layer, and if it is too thin, the Ag-based light reflecting layer and the first It facilitates mass transfer to and from the upper protective layer and does not function as a chemically inert layer.
On the other hand, if the thickness is too large, the number of overwrites and the reflectance will decrease. As described above, the second upper protective layer has a predetermined thickness so as to balance the chemical inertness, the number of overwrites, and the reflectance.

An overcoat layer is formed on the reflection / heat dissipation layer to prevent its oxidation. As the overcoat layer, a UV curable resin produced by spin coating is suitable. The appropriate thickness is 3 to 15 μm. Three
If the thickness is less than μm, an increase in error may be observed when the printing layer is provided on the overcoat layer.
If it is thicker than 5 μm, the internal stress becomes large and the mechanical properties of the disk are greatly affected. An ultraviolet curable resin produced by spin coating is generally used as the material for the hard coat layer. Its thickness is 2-6μ
m is suitable. If it is thinner than 2 μm, sufficient scratch resistance cannot be obtained, and if it is thicker than 6 μm, internal stress becomes large and the mechanical properties of the disk are greatly affected. The hardness of the hard coat layer needs to be equal to or higher than the pencil hardness H so that it is not scratched by rubbing with a cloth. If necessary, it is also effective to prevent the electrification by mixing a conductive material and prevent the adhesion of dust and the like.

The printing layer is used for the purpose of ensuring scratch resistance, label printing of brand names and the like, formation of an ink receiving layer for an ink jet printer and the like, and it is preferable to form an ultraviolet curable resin by a screen printing method.
A suitable thickness is 3 to 50 μm. If the thickness is less than 3 μm, unevenness may occur during layer formation, and 50 μm
If the thickness is made thicker, the internal stress becomes larger and the mechanical properties of the disk are greatly affected. As the adhesive layer, an adhesive such as an ultraviolet curable resin, a hot melt adhesive, or a silicone resin can be used. The material for such an adhesive layer is applied on the overcoat layer or the printing layer by a method such as spin coating, roll coating, or screen printing according to the material, and is subjected to treatments such as ultraviolet irradiation, heating, and pressure. Go and stick with the disc on the other side. The disk on the opposite surface may be the same single plate disk or only the transparent substrate, and the material for the adhesive layer may or may not be applied to the bonding surface of the disk on the opposite surface. Also,
A pressure-sensitive adhesive sheet can also be used as the adhesive layer. The thickness of the adhesive layer is not particularly limited, but is 5 to 100 in consideration of the coating properties of the material, the curability, and the mechanical properties of the disk.
μm, preferably 7 to 50 μm. The range of the adhesive surface is not particularly limited, but when applied to a rewritable disc that is compatible with DVD and / or CD, the position of the inner peripheral edge is set to Φ15 in order to secure the adhesive strength to the extent that high-speed recording is possible. -40 mm, preferably 15-30 mm.
Further, the glass transition temperature of the adhesive layer is preferably 100 ° C. or lower in order to secure the drop durability of the optical recording medium.

[0024]

EXAMPLES The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples.

Example 1 A 0.6 mm thick polycarbonate substrate having a guide groove with a groove width of 0.25 μm and a groove depth of 27 nm was injection-molded, and a lower protective layer, a light absorbing layer, and a first upper portion were formed on the substrate. Protective layer,
The second upper protective layer and the Ag light reflection layer having a purity of 99.99 wt% were sequentially stacked by the sputtering method. ZnS.SiO ₂ (SiO ₂₎ is used for the lower protective layer and the first upper protective layer.
With ₂ 20 mol%), respectively the film thickness 80 nm, 1
1 nm. Ag _0.5 Ge _1.5 is used for the light absorption layer.
In ₈ Sb ₇₀ Te ₂₀ was used and the thickness was set to 16 nm.
A SiC film having a thickness of 4 nm was used for the second upper protective layer.
For the Ag light reflection layer, Ag having a purity of 99.99 wt% with 0.003 wt% of Cu added was used and had a thickness of 140 nm. As a result, polycarbonate substrate / ZnS.Si
O ₂ (80 nm) / Ag _{0. 5} Ge _1.5 In ₈ Sb
₇₀ Te ₂₀ (16 nm) /ZnS.SiO ₂ (11n
m) / SiC (4 nm) /99.99 wt% Ag-0.
A layer structure of 003 wt% Cu (140 nm) was formed. Then, an overcoat layer was formed on the Ag light reflection layer by spin coating of an ultraviolet curable resin to prepare a single-disc disk of a phase change type optical recording medium. Next, another polycarbonate substrate was attached with an ultraviolet curable adhesive to obtain an optical recording medium having the structure shown in FIG. Next, a linear velocity of 3.0 m / s, an electric power of 850 mW and a feed of 1 were set by an initialization device having a large diameter LD (beam diameter 200 × 1 μm).
At 00 μm, the entire surface was crystallized from the inner circumference to the outer circumference at a constant linear velocity, but no abnormality in mechanical properties such as warpage due to Ag stress was observed in the optical recording medium. Next, a recording linear velocity of 16.75 m / s was applied to the obtained phase change optical recording medium.
Optical recording was performed in a DVD-ROM reproducible format with a wavelength of 650 nm, an NA (aperture ratio) of 0.65, and a recording power of 14.5 mW. The minimum mark length is 0.4 μm.
As a result, after overwriting 1000 times, Data
The to Clock Jitter (data to clock jitter) was good at 8.5%. In addition, the reflectance is 20% and the modulation degree is 63%, and the signal characteristics are good.
The original high light reflectance and high thermal conductivity could be used efficiently. Further, even after a storage test in which this phase change type optical recording medium was left in an environment of temperature 80 ° C. and humidity 85% RH for 500 hours, the reflectance was 20% and the degree of modulation was 63%, which was not observed. A of the phase change type optical recording medium before and after this storage test
As a result of examining the cross-sectional TEM and electron beam diffraction spectrum of the g light reflection layer, Cu was observed at the Ag grain boundaries before storage, whereas Cu was observed at the Ag grain boundaries after storage.
O and CuS were observed, and it was found that Ag corrosion was suppressed. From these, by adding 0.003 wt% Cu to 99.99 wt% pure silver, A
It was confirmed that the corrosion of g was prevented and the high light reflectance and high thermal conductivity inherent in Ag could be efficiently used.

Example 2 A 0.6 mm thick polycarbonate substrate having a guide groove with a groove width of 0.25 μm and a groove depth of 27 nm was injection molded, and a lower protective layer, a light absorbing layer, and a first upper portion were formed on the substrate. Protective layer,
The second upper protective layer and the Ag light reflecting layer having a purity of 99.99 wt% were sequentially stacked by the sputtering method. The lower protective layer and the first upper protective layer are made of ZnS.SiO ₂ (SiO ₂
20 mol%) and the film thickness is 80 nm and 11 respectively.
nm. Ge ₂ Ga ₅ Sb ₇₃ Te is used for the light absorption layer.
₂₀ was used and the thickness was set to 16 nm. A SiC film having a thickness of 4 nm was used for the second upper protective layer. For the Ag light reflection layer, Ag having a purity of 99.99 wt% with 0.0005 wt% of Fe and Al added, and having a thickness of 140 nm
And The Ag light reflection layer is formed at a substrate temperature of 70 ° C.
The film formation speed was 120 nm / s, and the particle size was controlled to 60 nm. As a result, polycarbonate substrate / ZnS.Si
O ₂ (80 nm) / Ge ₂ Ga ₅ Sb ₇₃ Te ₂₀ (1
6 nm) /ZnS.SiO ₂ (11 nm) / SiC (4
nm) /99.99 wt% Ag-0.005 wt% Fe
A layer structure of -0.0005 wt% Al (140 nm) was formed. Then, an overcoat layer was formed on the Ag light reflection layer by spin coating of an ultraviolet curable resin to prepare a single-disc disk of a phase change type optical recording medium. Then
Another polycarbonate substrate was attached with an ultraviolet curable adhesive to obtain an optical recording medium having the structure shown in FIG. Next, with an initialization device having a large diameter LD (beam diameter 200 × 1 μm), a linear velocity of 3.0 m / s and an electric power of 850 m
Although the entire surface was crystallized at a constant linear velocity from the inner circumference to the outer circumference at a feed rate of W and 100 μm, no abnormalities in mechanical properties such as warpage due to Ag stress were found in the optical recording medium. Then, a recording linear velocity of 16.
Optical recording was performed in a DVD-ROM reproducible format at 75 m / s, wavelength 650 nm, NA 0.65, and recording power 14.5 mW. The minimum mark length is 0.4 μm. As a result, Da after recording 1000 times of overwriting
The ta to Clock Jitter (data to clock jitter) was as good as 8.0%. In addition, the reflectance was 21% and the modulation degree was 60%, and the signal characteristics were also good, and the original high light reflectance and high thermal conductivity of Ag could be efficiently utilized. Further, this phase change type optical recording medium is heated at a temperature of 80
Even after a storage test in which the sample was left for 500 hours in a RH environment of 85 ° C. and a humidity of 85%, the reflectance was 21% and the degree of modulation was 60%. As a result of examining the cross-sectional TEM and electron beam diffraction spectrum of the Ag light reflecting layer of the phase change optical recording medium before and after this storage test, it was found that Fe and Al existed in the Ag grain boundaries before storage. On the other hand, after storage, FeSx (X = 1.0 to 1.
5), AlOx (X = 1.0 to 1.5) was observed, and A
It was found that the corrosion of g was suppressed. From these, 0.0005 wt% F is added to 99.99 wt% pure silver.
e and Al are added to prevent Ag corrosion,
It was also confirmed that Ag's original high light reflectance and high thermal conductivity can be efficiently used.

Example 3 A polycarbonate substrate having a thickness of 0.6 mm and having a guide groove having a groove width of 0.25 μm and a groove depth of 100 nm was injection-molded,
A light absorption layer was formed on this substrate by spin coating with an alcohol solution of an azo dye. The film thickness of the groove is 120
nm. Then, as a light reflecting layer, M
Purity with 0.0001 wt% of g and Zn added 9
9.99 wt% Ag was formed to a thickness of 100 nm. The Ag light reflection layer was formed at a substrate temperature of 50 ° C. and a film formation rate of 12
The particle size was controlled to 0 nm / s and the particle size was controlled to 30 nm. As a result, polycarbonate substrate / azo dye / 99.99 wt
% Ag-0.0001 wt% Mg-0.0001 wt%
A layer structure of Zn (100 nm) was formed. Then
An overcoat layer was formed by spin-coating an ultraviolet curable resin on the Ag light reflection layer to prepare a single plate disk for an optical recording medium. Next, another polycarbonate substrate was bonded with an ultraviolet curable adhesive to obtain an optical recording medium having the structure shown in FIG. 4, but no abnormality in mechanical properties such as warpage due to Ag stress was observed. Next, a recording linear velocity of 16.75 m / s and a wavelength of 650 were applied to the obtained phase change optical recording medium.
nm, NA 0.65, recording power 15 mW, DVD-
Optically recorded in ROM reproducible format. The minimum mark length is 0.4 μm. As a result, Data after recording
The to Clock Jitter (data to clock jitter) was as good as 7.5%. In addition, the signal characteristics, such as a reflectance of 65% and a modulation degree of 65%, are good.
The original high light reflectance could be efficiently used. When this optical recording medium was reproduced with a DVD-ROM drive, it could be reproduced without any problem. Furthermore, even after a storage test in which this optical recording medium was left in an environment of temperature 80 ° C. and humidity 85% RH for 500 hours, the reflectance was 65% and the degree of modulation was 65%.
No change was observed. As a result of examining the cross-sectional TEM and electron beam diffraction spectrum of the Ag light reflection layer of the optical recording medium before and after this storage test, the presence of Mg and Zn was observed at the Ag grain boundaries before storage, whereas Later, ZnS and MgO were observed at the Ag grain boundaries, and AgS
It has been found that it suppresses the corrosion of. From these, 0.0001 wt% of M is added to 99.99 wt% of pure silver.
g and Zn are added to prevent Ag corrosion,
Moreover, it was confirmed that Ag's original high light reflectance can be efficiently used.

Examples 4 to 11 Bi (Example 4), Ca (Example 5), Cd (Example 6), Mn (Example 7) were used in place of Cu added to the Ag light reflecting layer in Example 1. ), Ni (Example 8), Pd
(Example 9), Pb (Example 10), Sb (Example 1)
When an optical recording medium having the structure of FIG. 2 was produced and evaluated in the same manner as in Example 1 except that 1) was used, the same results as in Example 1 were obtained.

[0029]

According to the first aspect of the present invention, it is possible to obtain an optical recording medium in which the stress of the light reflecting layer is small and the recording signal characteristics, particularly the jitter, are good. According to the second aspect of the present invention, the stress of the light reflecting layer is small, the recording signal characteristics, especially the jitter are good, and R
A good optical recording medium compatible with the OM drive can be obtained. According to the third aspect of the present invention, it is possible to provide an optical recording medium that effectively utilizes the high light reflectance and high thermal conductivity that are characteristics of Ag and suppresses Ag corrosion. According to the present invention 4, it is possible to easily provide an optical recording medium that effectively utilizes the high light reflectance and high thermal conductivity that are characteristics of Ag and suppresses the corrosion of Ag.
According to the present invention 5, it is possible to provide an optical recording medium that effectively utilizes the high light reflectance and high thermal conductivity that are characteristics of Ag, and effectively suppresses the corrosion of Ag.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of a layer structure of an optical recording medium of the present invention.

FIG. 2 is a diagram showing an example of a layer structure when the optical recording medium shown in FIG. 1 is changed to a bonded type.

FIG. 3 shows an optical recording medium of the present invention, which is a CD-R or a DVD-R.
The figure which shows an example of the layered structure when using it.

FIG. 4 is a diagram showing an example of a layer structure when the optical recording medium shown in FIG. 3 is changed to a bonded type.

FIG. 5 is a diagram showing a relationship between a particle diameter of a light reflecting layer material and recording signal characteristics.

FIG. 6 is a ratio of the average crystal grain size Lc of the reflective layer to the film thickness Lt (L
FIG. 6 is a diagram showing a relationship between c / Lt) and the modulation factor of a recording signal.

[Explanation of symbols]

1 substrate 2 Lower protective layer 3 Light absorption layer 4 First upper protective layer 5 Second upper protective layer 6 Ag-based light reflection layer 7 Overcoat layer 8 printing layers 8'printing layer 9 Hard coat layer 10 Adhesive layer 11 Laminated substrate or disk

Claims (5)

[Claims] 1. In an optical recording medium having a substrate, a light absorbing layer and a light reflecting layer, an average crystal grain size Lc of the light reflecting layer, a minimum mark length Lm to be recorded, and a film thickness Lt of the light reflecting layer. ,
An optical recording medium characterized by the following formula. Lt / 4 ≦ Lc ≦ Lm 2. The optical recording medium according to claim 1, wherein the Lc, Lm, and Lt have the following relationship. Lt / 3 ≦ Lc ≦ Lm 3. The optical recording according to claim 1, wherein the light reflecting layer is made of Ag having a purity of 99 wt% or more containing 0.00005 to 0.005 wt% of a metal having a standard electrode potential lower than that of Ag. Medium. 4. A metal having a standard electrode potential smaller than that of Ag,
Al, Bi, Ca, Cu, Cd, Fe, Mn, Mg, N
The optical recording medium according to claim 3, which is at least one selected from i, Pd, Pb, Sb, and Zn. 5. A metal having a standard electrode potential smaller than that of Ag,
The optical recording medium according to claim 3 or 4, wherein the optical recording medium is contained in a crystal grain boundary of Ag and / or an Ag alloy of the light reflecting layer.