JP2523421B2 - Optical recording medium - Google Patents

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 having a recording layer on a substrate, and more particularly to a write / write device for a compact disc.
The present invention relates to a once type optical recording disc.

[0002]

2. Description of the Related Art As an optical recording medium having a recording layer and a reflective layer on a substrate, for example, a compact disc (hereinafter referred to as C
An optical recording disk has been proposed which can be additionally recorded or recorded according to the standard (abbreviated as D) (Nikkei Electronics, January 23, 1989, No. 46).
5, P107, Kinki Chemical Association Functional Dye Subcommittee,
March 3, 1989, Osaka Science and Technology Center, SPIE vol
1078 Optical Data Storage Topical Meeting, 80 1989
etc).

This is a transparent resin substrate, a dye layer,
The Au reflective layer and the protective film are formed in this order. That is, the reflective layer is provided in close contact with the dye layer.

Conventionally, an air layer is provided on the dye layer in order to form recording marks or pits on the dye layer. However, in this proposal, since the reflection layer is provided in close contact with the dye layer, It is possible to configure a CD standard disc having a total thickness of 1.2 mm.

In the case of a contact type medium in which such a reflective layer and a recording layer containing a dye are provided in close contact with each other, particularly 60% or more, particularly C of the recording light and the reproducing light of the recording layer.
The D standard requires a reflectance of 70% or more. Therefore, as disclosed in Japanese Patent Laid-Open No. 2-79235, an Au thin film having a high reflectance and a high corrosion resistance is used for the reflective layer.

However, since Au is soft, when the recording layer is irradiated with recording light to form the recording mark portion, the Au thin film on the recording mark portion may be deformed due to thermal expansion of the recording layer. Therefore, the eye pattern, which is the reproduced output waveform, is disturbed and jitter is increased.

Since Au is expensive, it has been proposed to use a relatively inexpensive metal thin film such as Ag or Cu as the reflective layer. For example, Japanese Patent Laid-Open Nos. 2-79235 and 2-87341 disclose specific examples of using a Ag thin film, a Cu thin film, or the like as a reflective layer.

However, in the case of a Cu thin film or an Ag thin film, a reflectance of about 70% is obtained at the beginning of film formation, but its corrosion resistance is insufficient.

On the other hand, a metal thin film other than Au, Ag, and Cu, such as an Al thin film, cannot provide sufficient reflectance.

Therefore, an optical recording disk in which a metal thin film other than Au is applied to the reflective layer has a large error rate and is difficult to put into practical use.

[0011]

SUMMARY OF THE INVENTION An object of the present invention is to have a reflective layer having a high reflectance and a good corrosion resistance, without disturbing the eye pattern and increasing the jitter, and having a small error rate and good recording. Another object of the present invention is to provide an optical recording medium that can be reproduced.

[0012]

The above objects are achieved by the present invention described in (1) to (6) below.

(1) An optical recording comprising a recording layer on a substrate, and a reflective layer of an alloy thin film containing Cu and 5 at% or more and less than 40 at% Ag on the recording layer. Medium.

(2) The recording layer contains a dye and is formed by laminating the reflective layer in close contact with the recording layer, and recording light is irradiated onto the recording layer to form a recording mark portion. The optical recording medium according to (1) above, which reproduces with reproduction light.

(3) When reproducing light is radiated from the substrate side,
The reflectance of the unrecorded portion is 60% or more, the reflectance of the recorded portion is 60% or less of the reflectance of the unrecorded portion, and the extinction coefficient k of the recording layer at the wavelengths of the recording light and the reproducing light is 0. 0.01 to 0.25, the refractive index n of the recording layer at the wavelengths of the recording light and the reproducing light is 1.8 to 4.0, and the wavelengths of the recording light and the reproducing light are 600 to 900 nm. The optical recording medium according to 2).

(4) At the interface between the substrate and the recording layer of the recording mark portion, there is a layer containing a decomposition product of the recording layer material and substantially not containing the substrate material. The optical recording medium according to 2) or (3).

(5) The optical recording medium as described in (4) above, wherein a void is formed in the recording mark portion.

(6) The optical recording medium as described in any of (2) to (5) above, which has a protective film on the reflective layer, and has a pencil hardness of H to 8H at 25 ° C.

[0019]

The alloy thin film used for the reflective layer of the optical recording medium of the present invention has a high reflectance and a high corrosion resistance. Therefore, an optical recording medium having a small error rate and capable of excellent recording and reproduction is realized.

Further, in the case of an optical recording medium having a recording layer on a substrate and a reflective layer laminated on the recording layer in close contact, the recording layer is irradiated with recording light because the reflective layer is hard. Even if the portion is formed, the reflective layer on the recording mark portion is not deformed.
Therefore, the disturbance of the eye pattern and the increase of jitter do not occur.

[0021] In Japanese Patent Laid-Open No. 186244/1982, Ag-C containing Ag in an amount of more than 40 at% on the substrate.
An optical read information disc having a reflective layer of a u alloy thin film is described. Since this optical read information disc is a read-only disc having no recording layer, no problem occurs in the reflective layer.

However, in the case of Ag-Cu alloy thin film, Ag
Of 40 at% or more, sufficient hardness as a reflection layer of the optical recording medium cannot be obtained. Therefore, particularly in the case of an optical recording medium in which a reflective layer is laminated in close contact with the recording layer,
When the recording mark portion is formed by irradiating the recording light, the reflective layer on the recording mark portion may be deformed due to thermal expansion of the recording layer. As a result, the eye pattern is disturbed and jitter is increased.

On the other hand, in the present invention, the content of Ag in the Cu-Ag alloy thin film is regulated to less than 40 at%, so that the reflection layer having sufficient hardness can be obtained as described above.

[0024]

Specific Structure The specific structure of the present invention will be described in detail below.

The optical recording medium of the present invention has a recording layer on the substrate and a reflective layer on the recording layer. In this case, the recording layer is not particularly limited as long as it can record information later, but here, the optical recording medium shown in FIG. 1 will be described as a preferred example.

This optical recording medium 1 is a contact type in which a recording layer 3 containing a dye is provided on a substrate 2, and a reflective layer 4 and a protective film 5 are formed in close contact with the recording layer 3. .

The substrate 2 includes recording light and reproducing light (600-
It is formed of a resin or glass that is substantially transparent (preferably a transmittance of 80% or more) to a semiconductor laser beam of about 900 nm, particularly 700 to 800 nm, especially 780 nm. This enables recording and reproduction from the back side of the substrate.

The substrate 2 is in the shape of a disk of a normal size, and when used as a CD, the thickness is about 1.2 mm and the diameter is about 80 to 120 mm.

In this case, it is preferable to use resin as the substrate material, and various thermoplastic resins such as polycarbonate resin, acrylic resin, amorphous polyolefin, TPX and the like are preferable.

If necessary, an oxygen barrier film may be formed on at least one of the outer surface and the inner surface of the substrate 2 and, if necessary, on the inner and outer peripheral surfaces.

A groove for tracking is preferably formed on the surface of the substrate 2 on which the recording layer 3 is formed.

The groove is preferably a spiral continuous groove having a depth of 250 A or more, especially 6
00A or more and 2200A or less, particularly 1800A or less, a width of 0.2 to 1.1 μm, particularly 0.3 to 0.6 μm, and a land (a portion between adjacent grooves) width of 0.5 to
It is preferably 1.4 μm, and particularly preferably 1.0 to 1.3 μm.

With such a structure of the groove, a good tracking signal can be obtained without lowering the reflection level of the groove portion. It should be noted that the groove may be provided with unevenness for address signals.

In the present invention, when the substrate has a groove, it is preferable that the recording light is applied to the recording layer in the groove. That is, the optical recording medium of the present invention is preferably used as an optical recording medium for groove recording. By using groove recording, the effective thickness of the recording layer can be increased.

Further, a resin layer (not shown) may be formed on the substrate 2 by, for example, the 2P method, and a groove for tracking or an unevenness for address signal may be provided in the resin layer.

The resin material forming the resin layer is not particularly limited and may be appropriately selected from known resins used in the so-called 2P method, but a radiation-curable compound is usually used.

The recording layer 3 is formed by compatibilizing one kind or two or more kinds of dyes.

In this case, the light absorbing dye may be mixed with a quencher, and an ionic combination of a dye cation and a quencher anion may be used as the light absorbing dye.

The extinction coefficient (imaginary part of complex refractive index) k of the recording layer 3 at the wavelengths of the recording light and the reproducing light is 0.01 to 0.
It is preferably 25, more preferably 0.03 to 0.25. When k is less than the above range, the absorptivity of the recording layer is lowered, and it is difficult to perform recording with normal recording power. When k exceeds 0.25, the reflectance is 60%.
, Which makes it difficult to perform reproduction according to the CD standard. In this case, a value of k 0.02 to 0.10, particularly 0.03 to 0.05, gives extremely preferable results.

The refractive index (real part of complex refractive index) n is
It is preferably 1.8 to 4.0, more preferably 2.2 to 3.3. When n <1.8, the reflectance decreases and C
Reproduction according to the D standard tends to be difficult. Also, n>
To obtain 4.0, it is difficult to obtain the raw material dye.

When measuring n and k, a recording layer is formed on a predetermined transparent substrate to a thickness of about 400 to 1000 A under actual conditions to prepare a measurement sample.
Then, the reflectance through the substrate or from the recording layer side is measured. The reflectance is measured by specular reflection (about 5 °) using the recording / reproducing light wavelength. In addition, the transmittance of the sample is measured. From these measured values, for example, n and k may be calculated according to Kyoritsu Zensho "Optical" Kozo Ishiguro P168-178.

The light absorbing dye to be used is not particularly limited as long as it has an absorption maximum of 600 to 900 nm, preferably 600 to 800 nm, and more preferably 650 to 750 nm. One or more of phthalocyanine type, anthraquinone type, azo type, triphenylmethane type, pyrylium or thiapyrylium salt type, squarylium type, croconium type, metal complex dye type and the like are preferable.

Cyanine dyes include indolenine ring,
A cyanine dye having a benzoindolenine ring is particularly preferable.

The method for forming the recording layer 3 is not particularly limited,
For example, layering by coating using various solvents,
A known method such as vapor deposition may be used.

The thickness of the recording layer 3 is 500 to 2 at the land portion.
It is preferably 000A. Outside this range, the reflectance decreases and it becomes difficult to reproduce the CD standard.

A reflective layer 4 is provided on the recording layer 3 so as to be in direct contact therewith.

The reflective layer 4 is composed of an alloy thin film containing Cu and Ag. By using the above alloy thin film, a high reflectance is obtained, and compared with Cu thin film and Ag thin film,
The corrosion resistance of the film is remarkably improved, and the hardness of the film is remarkably increased as compared with the Au thin film.

The content of Ag in the reflective layer 4 is 40 at%.
Less than When the content is 40 at% or more, the hardness of the film is insufficient. Therefore, when the recording layer 3 is irradiated with recording light to form the recording mark portion 6, thermal expansion of the recording layer 3 causes the recording mark portion 6 to remain on the recording mark portion 6. The reflective layer 4 is deformed. Therefore, the eye pattern is disturbed and the jitter is increased.

However, if the content of Ag is too small, the corrosion resistance is insufficient. For example, when it is stored or used for a long period of time under high temperature and high humidity, the reflectance of the film decreases and the error increases. Further, Cu in the reflective layer 4 easily diffuses into the recording layer 3 containing a dye, which has a bad influence.

For the above reason, the upper limit of the Ag content in the reflective layer 4 is preferably 38 at%, more preferably 36 at%.
at%, particularly preferably 35 at%.

The lower limit is 5 at%, more preferably 6 at%.
at%, more preferably 8 at%, particularly preferably 1
It is 0 at%.

The reflective layer 4 preferably has a thickness of 500 A or more, and may be formed by vapor deposition, sputtering or the like.
Although the upper limit of the thickness is not particularly limited, it is preferably about 1200 A or less in consideration of cost, production work time and the like.

Accordingly, the reflectance of the reflective layer 4 alone is
The reflectance of 90% or more, the reflectance of the unrecorded portion of the medium through the substrate is 60% or more, and particularly 70% or more.

A protective film 5 is formed on the reflective layer 4.

The protective film 5 may be formed of various resin materials such as an ultraviolet curable resin, etc., usually in a thickness of about 0.1 to 100 μm. The protective film 5 may be layered or sheet-shaped.

The protective film 5 is preferably a radiation-cured coating film containing a radiation-curable compound and a photopolymerization sensitizer. The hardness of the protective film 5 is 25
The pencil hardness (JIS K-5400) at C is from H to
It is preferably configured to be 8H, especially 2H to 7H.

With this structure, the eye pattern is further improved and the jitter is remarkably reduced. Further, the protective film and the reflective layer do not peel off even when stored under conditions of high temperature and high humidity or changes in temperature and humidity. More specifically, if the hardness of the protective film is softer than H, the eye pattern will be disturbed and jitter will increase, and if it is harder than 8H, the coating film will become brittle and the film forming ability will decrease, and also the adhesive force with the reflective layer will decrease. To do.

The radiation-curable compound used for forming such a protective film preferably contains an oligoester acrylate.

The oligoester acrylate is an oligoester compound having a plurality of acrylate groups or methacrylate groups. And preferable oligoester acrylate has a molecular weight of 1,000 to 10,000, preferably 2,000 to 7,000 and a polymerization degree of 2 to 10,
Preferably, 3-5 are mentioned. Further, among these, 2 to 6 acrylate groups or methacrylate groups are used.
Polyfunctional oligoester acrylates having one, preferably 3 to 6, are preferred.

In addition to the above compounds, or in place of this, a radiation curable compound obtained by subjecting a thermoplastic resin to radiation-sensitive modification may be used.

The thickness of the protective film of such a radiation-curable compound is 0.1 to 30 μm, more preferably 1 to 10 μm.
Is.

When the film thickness is less than 0.1 μm, it is difficult to form a uniform film, the moisture-proof effect in an atmosphere with high humidity is not sufficient, and the durability of the recording layer is lowered. Moreover, the effect of preventing jitter is reduced. If it exceeds 30 μm,
Due to the shrinkage that accompanies the curing of the resin film, the warp of the recording medium and the cracks in the protective film are likely to occur.

Such a coating film is usually formed by spinner coating, gravure coating, spray coating, dipping, etc.
Layers may be formed by combining various known methods. The layer forming conditions of the coating film at this time may be appropriately determined in consideration of the viscosity of the mixture of the coating film composition, the target coating film thickness, and the like.

The radiation for irradiating the coating film in the present invention includes ultraviolet rays and electron beams, but ultraviolet rays are preferable.

When ultraviolet rays are used, a photopolymerization sensitizer is usually added to the above radiation-curable compounds.

Examples of the photopolymerization sensitizer include benzoin compounds such as benzoin methyl ether, benzoin ethyl ether, α-methylbenzoin, α-chlordeoxybenzoin, benzophenone, acetophenone, morpholinodimethylmethyl-4-methylthiophenyl ketone,
Examples thereof include ketones such as bisdialkylaminobenzophenone, quinones such as acetoraquinone and phenanthraquinone, and sulfides such as benzyl disulfide and tetramethylthiuram monosulfide.

To cure a coating film containing such a photopolymerization sensitizer and a radiation-curable compound by ultraviolet rays, various known methods may be used. For example, a UV bulb such as a xenon discharge tube or a mercury discharge tube may be used. An electron beam can also be used depending on the case.

In order to perform recording or additional recording on the optical recording medium 1 having such a structure, for example, recording light having a wavelength of 780 nm is irradiated through the substrate 2 in a pulsed manner.

As a result, the recording layer 3 absorbs light to generate heat, and the substrate 2 is also heated at the same time. As a result, in the vicinity of the interface between the substrate 2 and the recording layer 3, the recording layer material such as a dye is melted or decomposed, pressure is applied to the interface between the recording layer 3 and the substrate 2, and the bottom wall or side wall of the groove is deformed. There is something to do.

In this case, the decomposed product layer 61 containing the melted product or the decomposed product of the recording layer 3 usually remains in a shape that covers the bottom and the boundary of the groove 23. The material of the decomposed material layer 61 is a material that does not substantially include the substrate material, and is composed of a decomposed material of the recording layer material or a mixture of the decomposed material of the recording layer material and the recording layer material. The decomposed material layer 61 is usually about 30 to 95% of the thickness of the recording layer 3.

In general, a void 63 is formed on the decomposed material layer 61 at the interface with the reflective layer, and the decomposed material layer 61 and the void 63 are formed in the recording mark portion 6. The void 63 is
It is usually about 5 to 70% of the thickness of the recording layer 3.

Although the substrate 2 may not be deformed in such a recording process, the recording mark portion 6 of the substrate 2 usually has the groove edge blunted by the pressure during heating.

In addition, the recording layer 3 or a decomposed product of the recording layer 3 or the like may remain on the void 63 with a small film thickness in close contact with the reflective layer 4.

As described above, a layer containing substantially no substrate material is formed at the interface between the substrate 2 and the recording layer 3 of the recording mark portion 6.

The recording light power is usually 5 to 9 mW.
The substrate rotation linear velocity may be about 1.2 to 1.4 m / s.

After the recording mark portion 6 is formed in this way, when the reproducing light of, for example, 780 nm is irradiated through the substrate 2, the recording mark portion 6 causes a phase difference of light,
The reflectance is reduced to 60% or less, particularly 50% or less, and further 40% or less of the unrecorded portion. On the other hand, in the unrecorded area, 6
Since it has a high reflectance of 0% or more, particularly 70% or more, reproduction according to the CD standard is possible.

The power of the reproducing light is about 0.1-10 mW.

The above-mentioned optical recording medium is an example of the optical recording medium of the present invention. In addition to this, the information is magnetically recorded by the modulated heat beam or the modulated magnetic field, and the recorded information is It may be a so-called magneto-optical recording medium that is magnetic-optically converted and reproduced. In this case, the recording layer is
The material is not particularly limited as long as magneto-optical recording can be performed, but an alloy containing a rare earth metal element, particularly an alloy of a rare earth metal and a transition metal, by sputtering, vapor deposition method, ion plating method, etc. It is preferably formed as an amorphous film.

The reflective layer used in the present invention can also be applied to a read-only optical reproducing medium such as an optical video disc or a compact disc which carries information in advance.

However, the optical recording medium is preferably formed by laminating the reflective layer in close contact with the recording layer containing the dye as described above.

[0081]

EXAMPLES The present invention will be described in more detail below by showing specific examples of the present invention.

Example 1 A recording layer containing a dye was formed on a 120 mmφ, 1.2 mm thick polyolefin resin substrate having continuous grooves. Cu-Ag is sputtered on this recording layer.
An optical recording disk sample No. 1 was obtained by forming an alloy thin film with a thickness of 1000 A to form a reflection layer, and further applying an ultraviolet curing resin containing an oligoester acrylate and then ultraviolet curing to form a protective film with a thickness of 5 μm. It was

The dye contained in the recording layer of Sample No. 1 is shown in Chemical Formula 1 below.

[0084]

Embedded image

The recording layer is formed on the substrate by 500 to 3000.
Spin coating was performed while rotating at rpm. As a coating solution, a 5.0 wt% cyclohexanone solution was used. The thickness of the recording layer is 2800A at the groove,
The land area was 1800A. The recording layer had a refractive index (n) of 2.3 and an extinction coefficient (k) of 0.03.

The values n and k are obtained by forming a solution containing the above dye on a measurement substrate to form a dry film thickness of 1000 A as a test recording layer, and measuring n and k of the test recording layer. It was In addition, this measurement was performed according to the description of "Optics" (Kozo Ishiguro, Kyoritsu Zensho), pages 168-178. In the measurement of the recording layer containing the dye represented by the above chemical formula 1, cyclohexanone was used as the solvent and a polyolefin substrate was used as the measurement substrate.

The composition of the Cu-Ag alloy thin film of the reflective layer is C
u ₆₅ Ag ₃₅ (at%), and the film forming conditions were as follows.

Sputtering pressure: 1.0 Pa Input power: 11.0 W / cm ²

The composition of the Cu-Ag alloy thin film was determined by inductively coupled high frequency plasma spectroscopy.

As the protective film, a coating composition containing the following radiation-curable compound and photopolymerization sensitizer was applied by spinner coating.

(Coating composition) Polyfunctional oligoester acrylate [30% by weight of oligoester acrylate (trifunctional or higher), 70% by weight of trimethylpropane acrylate, trade name Aronix M-8030; manufactured by Toagosei Co., Ltd.] 100 parts by weight Photopolymerization sensitizer (trade name: IRGACURE907; manufactured by Nippon Ciba Geigy) 5 parts by weight

After applying such a coating composition, 120 W /
An ultraviolet ray of cm was irradiated for 15 seconds to crosslink and cure to obtain a cured film. The pencil hardness of this film was 2H.

Sample No. 3 was replaced with the thin film shown in Table 1 below only the reflective layer. Sample No. 2 to No. 7 was produced.

EFM signals were recorded on the obtained samples No. 1 and No. 2 with a laser having a wavelength of 780 nm and 7 mW, and then reproduced on a commercially available compact disc player.

As a result, the S / N ratio was high, and good reproduction could be performed. A reflectance of 70% or more was obtained in the unrecorded area, and the reflectance of the recorded area was 4 times that of the unrecorded area.
It was 0% or less.

Next, the following evaluation was performed on each sample.

1) Reflectance E with a laser of wavelength 780 nm, 7 mW for the sample
After recording the FM signal, reproduction was performed with a commercially available compact disc player to measure the reflectance at the Itop level of the recording portion.

Then, the sample was placed at a temperature of 80 ° C. and a humidity of 80.
After being left in an environment of% RH for 200 hours, the reflectance at the Itop level of the recording portion was similarly measured.

Then, using the initial reflectance of each sample as a reference (1.00), the normalized reflectance of each of Samples No. 1 to No. 6 was calculated.

Evaluation Criteria O: Standardized reflectance is over 0.93 X: Normalized reflectance is less than 0.93

2) C1 error Playback with a commercially available compact disc player
C1 initially and after 200 hours (80 ° C, 80% RH)
The error was measured.

In this case, the C1 error CD standard is 22.
It is within 0 (count / second).

Evaluation Criteria ○ ... Within C1 error 220 (counts / second) × ... Over C1 error 220 (counts / second)

3) Disturbance of eye pattern Observing the initial eye pattern using an oscilloscope,
The degree of disorder was evaluated on a three-point scale of ○, Δ, and ×.

Evaluation Criteria ◯: Eye pattern is not disturbed △: Eye pattern rising portion is slightly disturbed × ... Eye pattern rising portion is disturbed

A photograph of the oscilloscope waveform of the initial eye pattern of sample No. 1 is shown in FIG. 2, and a photograph of the oscilloscope waveform of the initial eye pattern of sample No. 4 is shown in FIG.

4) Jitter Playback with a commercially available compact disc player,
Jitter was measured at the initial stage and after 200 hours (80 ° C., 80% RH). As the evaluation device, a CD jitter meter MJM-631 manufactured by MEGURO was used.

Evaluation Criteria ○: Less than 30 ns ×: 30 ns or more

The results are shown in Table 1.

[0110]

[Table 1]

From the results shown in Table 1, the effect of the present invention is clear.

When the pencil hardness of the protective film of each sample was lowered, the eye pattern was slightly disturbed and the jitter was increased.

Further, various samples having different Ag contents in the reflective layer were prepared and evaluated in the same manner as the above, and the same result was obtained.

Example 2 In the same manner as in Example 1, except that a polycarbonate resin substrate was used instead of the polyolefin resin substrate, and diacetone alcohol was used instead of cyclohexanone as the solvent of the coating solution when forming the recording layer. A sample was prepared. Sample No. 1 to No. Sample No. 6 corresponding to No. 6 21-No. 26. Sample No. Two
1 to No. The same operation as in Example 1 was performed on Sample No. 26, and the same evaluation was performed. 1 to N
o. Equivalent results were obtained corresponding to 6.

[0115]

In the optical recording medium of the present invention, since the reflective layer has good corrosion resistance and moisture resistance, the high reflectance can be maintained even when it is used under high temperature and high humidity or is stored for a long time. Therefore, an optical recording medium having a small error rate and capable of excellent recording and reproduction is realized.

Further, according to the close contact type optical recording medium of the present invention, since the reflectance is high and the reflectance is greatly reduced at the recording mark portion, good optical recording capable of reproducing according to the CD standard is performed. Is possible.

Moreover, unlike the conventional optical recording medium in which the reflective layer of the Au thin film is formed, a good eye pattern can be obtained, the jitter is small, and the cost is advantageous.

[Brief description of drawings]

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

FIG. 2 is a drawing-substitute photograph showing an oscilloscope waveform, showing an eye pattern of the optical recording medium of the present invention.

FIG. 3 is a drawing-substitute photograph showing an oscilloscope waveform, showing an eye pattern of a conventional optical recording medium.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Optical recording medium 2 ... Substrate 21 ... Land part 23 ... Group 3 ... Recording layer 4 ... Reflective layer 5 ... Protective film 6 ... Recording mark part 61 ... Decomposition layer 63 ... Void

Claims (6)

(57) [Claims] 1. An optical recording medium having a recording layer on a substrate, and having a reflective layer of an alloy thin film containing Cu and 5 at% or more and less than 40 at% Ag on the recording layer. . 2. The recording layer contains a dye and is constituted by laminating the reflective layer in close contact with the recording layer, and irradiating the recording layer with recording light to form a recording mark portion,
The optical recording medium according to claim 1, wherein reproduction is performed with reproduction light. 3. When the reproducing light is irradiated from the substrate side, the reflectance of the unrecorded portion is 60% or more, and the reflectance of the recorded portion is 60% or less of the reflectance of the unrecorded portion. The extinction coefficient k of the recording layer at the wavelength of the reproducing light is 0.
The refractive index n of the recording layer at the wavelengths of the recording light and the reproducing light is 1.8 to 4.0, and the wavelengths of the recording light and the reproducing light are 600 to 900 nm. The optical recording medium according to 1. 4. A layer containing a decomposition product of a recording layer material and substantially not containing a substrate material is present at an interface portion between the substrate and the recording layer of the recording mark portion.
Or the optical recording medium according to item 3. 5. The optical recording medium according to claim 4, wherein a void is formed in the recording mark portion. 6. A protective film is provided on the reflective layer, and the pencil hardness of the protective film at 25 ° C. is H to 8H.
6. The optical recording medium according to any one of 1 to 5.