JPH1125515A - Optical recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the chemical stability with respect to a silver optical reflection layer and to improve the reliability and the durability of the optical reflection layer. SOLUTION: The optical recording medium is constituted of successively laminating an organic coloring material recording layer 2, an optical reflection layer 3 and a protective layer 4 on a substrate 1. The layer 3 is formed by the silver-ruthenium alloy, in which the silver contains ruthenium for 0.5 to 20 atom %, or the silver-ruthenium group alloy in which the silver contains ruthenium for 0.5 to 10 atom %, and contains at least more than one element for 0.1 to 10 atom %, among rhodium, palladium, iridium, platinum and gold.

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, and more particularly, to an optical recording medium having a silver-ruthenium alloy containing silver as a main component or a silver-ruthenium-based alloy light reflecting layer.

[0002]

2. Description of the Related Art Conventionally, gold or aluminum alloy has been widely used for a light reflection layer of an optical disk as an optical recording medium. Gold has high reflectivity and is chemically stable, and is therefore mainly used for write-once optical disks (such as CD-R) having an organic dye in a recording layer. However, gold is expensive, and cheaper materials are desired to reduce manufacturing costs.

On the other hand, aluminum alloys are inexpensive, have relatively high reflectivity, and are relatively chemically stable, so that read-only optical disks (CD-ROM, DVD-ROM) are used.
Etc.) and rewritable optical disks (CD-RW, DVD-R
AM, MO, etc.). However, the light reflection layer of the CD-R, which is a write-once optical disc, requires a high reflectivity sufficient to compensate for the attenuation of the light beam in the organic dye recording layer. Therefore, an aluminum alloy whose reflectivity is not as high as gold is required. Not yet used.

As a material for the light reflecting layer other than gold and aluminum alloy, silver having a reflectance equal to or higher than that of gold can be considered (see JP-A-57-212638). And silver is much cheaper than gold,
It satisfies both high reflectivity and economy, and can be applied to the light reflection layer of CD-R which is a write-once optical disc.

[0005]

However, silver is not chemically very stable, and when it is used as a light reflection layer of an optical recording medium, there is a possibility that a problem may occur in the reliability of the optical recording medium. In particular, when the optical recording medium is stored for a long period of time, a problem such as an increase in an error occurrence rate is likely to occur.

As a method for improving the chemical stability of silver, a method has been proposed in which another metal element is added to silver to form a silver alloy (for example, JP-A-61-134945).
And Japanese Patent Application Laid-Open No. 3-122845). The present inventor also produced an optical disk using these alloys and performed an environmental resistance test on it, but could not obtain sufficient performance.

[0007] The present invention has been made in view of such conventional problems.
By using a silver-ruthenium alloy or a silver-ruthenium-based alloy light reflection layer that is higher in reflectivity than aluminum alloy and less expensive than gold, the chemical stability is higher than that of silver. It is an object of the present invention to provide an optical recording medium having improved reliability and durability. Japanese Patent Application Laid-Open No. Hei 5-21704 discloses silver as one of a number of candidate materials for the light reflecting layer. In order to enhance the chemical stability of the light reflecting layer using these candidate materials. Of 1
Ruthenium is exemplified as one of the zero or more additional elements. However, there is no description about silver and ruthenium alloy, there is no detailed description such as composition ratio, and there is no description in Examples. That is, silver of a specific composition ratio
It cannot be said that a ruthenium alloy reflective film is described or suggested.

[0008]

According to the present invention, in an optical recording medium having a substrate and a light reflecting layer laminated on the substrate, the light reflecting layer is made of ruthenium and silver. It is composed of a silver-ruthenium alloy containing 0.5 to 20 atomic%. Similarly, in the invention according to claim 2, in an optical recording medium having a substrate and a light reflection layer laminated on the substrate, the light reflection layer is made of silver having a ruthenium content of 0.5 to 0.5%.
It is composed of a silver-ruthenium-based alloy containing 10 atomic% and containing 0.1 to 10 atomic% of at least one element selected from rhodium, palladium, iridium, platinum and gold.

With such a structure, the chemical stability of the light reflecting layer can be improved. If the silver-ruthenium alloy or the silver-ruthenium-based alloy has a ruthenium content of less than 0.5 atomic%, remarkable chemical stability cannot be added to silver. Conversely, if the amount of atoms other than silver is more than 20 atomic%, the chemical stability increases, but the reflectance of the silver alloy decreases, and expensive ruthenium, rhodium, palladium, iridium,
It is not economically preferable because the content of platinum, gold and the like increases.

The optical recording medium of the present invention can be applied to any of a read-only type, a rewritable type, and a write-once type optical recording medium. This is most effective when an organic dye recording layer is provided between the two and used as a write-once type optical recording medium that requires high reflectivity and economic efficiency. In this case, on the light reflection layer,
A configuration in which layers such as a protective layer, an adhesive layer, and a second substrate are sequentially stacked may be employed.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view showing the structure of a write-once optical disc which is an embodiment of the optical recording medium of the present invention. On a substrate 1, an organic dye recording layer 2, a light reflection layer 3,
And the protective layer 4 are sequentially laminated.

The substrate 1 is preferably made of a material transparent to the recording light beam and the reproducing light beam, for example, resin or glass, and is particularly preferably resin because it is easy to handle and inexpensive. . Specifically, for example, a polycarbonate resin, an acrylic resin, an epoxy resin, an ABS resin, or the like can be used as the resin. The shape and dimensions of the substrate are not particularly limited, but are usually disk-shaped, the thickness is usually about 0.5 to 3 mm, and the diameter is 4 mm.
It is about 0 to 360 mm. On the surface of the substrate, a predetermined pattern such as a groove or the like for pre-pits for recording information or for tracking or addressing is provided as necessary.

The dye of the dye thin film forming the organic dye recording layer 2 is not particularly limited as long as it absorbs light, for example, laser energy and changes optical properties.
Specifically, organic dyes such as cyanine dyes, squarylium dyes, croconium dyes, azurenium dyes, triarylamine dyes, anthraquinone dyes, metal-containing azo dyes, dithiol metal complex salt dyes, and indoaniline metal Complex dyes, phthalocyanine dyes,
Naphthalocyanine dyes, intermolecular CT complex dyes and the like are preferably used. These dyes can be used alone or in combination. Further, an antioxidant, a binder, and the like can be added to the dye thin film.

As a method for forming the organic dye recording layer 2, a method in which an organic dye is dissolved in an organic solvent and spin-coated on a transparent substrate 1 is preferably used, but has a sublimation property like a phthalocyanine dye. For the dye, a vapor deposition method can also be used. The thickness of the dye thin film of the organic dye recording layer 2 is determined based on the wavelength used, the optical properties of the light reflection layer 3 and the dye in consideration of recording sensitivity to light energy used for recording such as a laser, a performance coefficient, and the like. It is appropriately selected according to the material of the thin film and the like, and is usually in the range of 120 to 150 nm.

The light reflection layer 3 is formed by adding ruthenium to silver in an amount of 0.5 to 0.5%.
A silver-ruthenium alloy containing 20 atomic%, or 0.5 to 10 atomic% of ruthenium in silver, and further containing at least one element selected from rhodium, palladium, iridium, platinum and gold in 0% A silver-ruthenium-based alloy containing 0.1 to 10 atomic% is used. The composition ratio of ruthenium in the silver-ruthenium alloy is preferably 10 atomic% or less, and more preferably 5 atomic% or less, in order to obtain a high reflectance. Similarly, for the composition ratio of elements other than silver in the silver-ruthenium-based alloy,
It is preferably at most 10 atomic%, particularly preferably at most 5 atomic%. The thickness of the light reflection layer 3 is usually 10 to 200 nm.
Is set to If it is thinner, high reflectivity cannot be obtained,
If the thickness is larger than this, no remarkable effect is exhibited.

The method of forming the light reflecting layer 3 is not particularly limited, but it is preferable to use a vapor phase growth method such as a sputtering method or a vacuum evaporation method, which can easily form a uniform film and is easy to mass-produce. After forming the light reflecting layer 3, the protective layer 4 is provided as a single layer or a plurality of layers in order to improve friction resistance and corrosion resistance.

The protective layer 4 is preferably composed of an organic substance mixed with various organic or inorganic fillers. In particular, the radiation-curable compound or its composition is irradiated with radiation such as electron beams or ultraviolet rays. It is preferably composed of a cured material. The thickness of the protective layer is usually about 0.1 to 100 μm in total, and can be formed by a usual method such as spin coating, gravure coating, spray coating, roll coating and the like.

In the write-once optical disc having the above-described configuration, an information signal is recorded by irradiating a recording light beam from the substrate 1 side to change the optical properties of the organic dye recording layer 2. On the other hand, during reproduction, it is weaker than the recording light beam,
The substrate 1 is irradiated with a reproducing light beam to the extent that the optical properties of the organic dye recording layer 2 do not change, and the recorded information signal is read based on the reflected light. Although this reflected light is attenuated by the organic dye recording layer 2, the light reflection layer 3 using a silver-ruthenium alloy or a silver-ruthenium-based alloy has a reflectance higher than that of an aluminum alloy, which is a practical problem. It is possible to obtain reflected light with no intensity.

Furthermore, the light reflecting layer 3 using a silver-ruthenium alloy or a silver-ruthenium-based alloy has improved reliability and durability, which have hitherto been disadvantages of the silver reflecting layer. It shows the same reliability and durability as the optical disk used.
Thus, for example, even when the optical disk is stored under high temperature and high humidity for a long period of time, the error occurrence rate does not significantly increase.

The present invention is applicable to various types of optical recording media such as a read-only type and a rewritable type, in addition to the write-once type optical recording medium described above. In the case of a read-only optical recording medium, one having a protective layer, an adhesive layer, a second substrate, and the like in addition to the above-described substrate and light reflecting layer is considered. It is conceivable that the substrate has a layer such as a dielectric layer, a phase-change recording layer, a protective layer, an adhesive layer, and a second substrate in addition to the substrate and the light reflecting layer described above. In the case of a rewritable optical recording medium utilizing magnetism (such as a magneto-optical disk), an interference layer, a reproducing layer, a non-magnetic intermediate layer, a magnetic recording layer, One having a layer such as a writing layer and a protective layer is conceivable.

[Embodiments] In order to specifically show the effects of the present invention, embodiments will be described below. (Example 1) Using a polycarbonate substrate having a spiral guide groove having a diameter of 120 mm and a plate thickness of 1.2 mm, a cyanine-based organic dye was reflected on an organic dye recording layer, and a silver-ruthenium alloy (ruthenium 3 atom%) was reflected light. A write-once optical disc (CD-R) used for the layer was produced.

First, a cyanine dye is dissolved in an organic solvent,
After filtering through a filter to remove impurities, the solution was applied on a substrate using a spin coater (manufactured by Able). Subsequently, heat treatment is performed in an oven to completely remove the solvent,
An organic dye recording layer was obtained. Next, a 100 nm-thick silver-ruthenium alloy (ruthenium 3 atomic%) light reflection layer was formed with a DC magnetron sputtering apparatus. Pure silver was used as the target, and a ruthenium chip was placed on the target to obtain a silver-ruthenium alloy film. As for the composition ratio, a silver-ruthenium alloy single layer film was directly formed on a glass substrate, and the composition was analyzed by an inductively coupled plasma emission spectrometer (ICP).

After forming the light reflecting film, an ultraviolet-curable resin was applied by a spin coating method and cured by irradiation with ultraviolet light to form a protective layer. The cured film thickness of the protective layer was 5 μm. Example 2 A write-once optical disc was manufactured in the same manner as in Example 1 except that the light reflecting layer was formed of a silver-ruthenium alloy (ruthenium 10 atomic%).

Example 3 A write-once optical disc was produced in the same manner as in Example 1, except that the light reflecting layer was formed of a silver-ruthenium-rhodium alloy (ruthenium 2 atomic%, rhodium 1 atomic%). Example 4 A write-once optical disc was manufactured in the same manner as in Example 1, except that the light reflecting layer was formed of a silver-ruthenium-palladium alloy (ruthenium 4 atomic%, palladium 2 atomic%).

Example 5 A light-reflecting layer was formed of a silver-ruthenium-iridium alloy (ruthenium 3 atomic%, iridium 1
Atomic%), a write-once optical disc was produced in the same manner as in Example 1. (Example 6) A write-once optical disc was manufactured in the same manner as in Example 1 except that the light reflecting layer was formed of a silver-ruthenium-platinum alloy (ruthenium 5 atom%, platinum 3 atom%).

Example 7 A write-once optical disc was produced in the same manner as in Example 1, except that the light reflecting layer was formed of a silver-ruthenium-gold alloy (ruthenium 7 atomic%, gold 1 atomic%). (Example 8) As a substrate, a polycarbonate substrate on which pits (concavities and convexities) corresponding to data for 74 minutes were formed in advance, an organic dye recording layer was not provided, and a light reflection layer was used.
A read-only optical disk (CD-ROM) was manufactured in the same manner as in Example 1 except that the optical disk was formed of a silver-ruthenium alloy (ruthenium 20 atomic%).

Example 9 A read-only optical disk was produced in the same manner as in Example 8, except that the light reflecting layer was formed of a silver-ruthenium-palladium alloy (ruthenium 10 atomic%, palladium 5 atomic%). Comparative Example 1 A write-once optical disc was manufactured in the same manner as in Example 1 except that the light reflecting layer was formed of silver.

Comparative Example 2 A read-only optical disk was manufactured in the same manner as in Example 8, except that the light reflecting layer was formed of silver. Comparative Example 3 An additional optical disc was manufactured in the same manner as in Example 1 except that the light reflecting layer was formed of a silver-ruthenium alloy (ruthenium 30 atomic%).

Comparative Example 4 A write-once optical disc was produced in the same manner as in Example 1, except that the light reflecting layer was formed of a silver-ruthenium-palladium alloy (ruthenium 20 at%, palladium 15 at%). Comparative Example 5 An additional optical disk was manufactured in the same manner as in Example 1, except that the light reflecting layer was formed of a silver-ruthenium alloy (ruthenium 0.3 atomic%).

Reference Example 1 A write-once optical disc was manufactured in the same manner as in Example 1 except that the light reflecting layer was formed of gold. In the optical disk obtained as described above, data was recorded on the write-once optical disk as follows. Data was transmitted and converted from the host computer by CD writing software, and the EFM signal was recorded for 74 minutes by a CD recorder (CDW-900E manufactured by SONY). The wavelength of the semiconductor laser used for the recording pickup of the CD recorder is 780 nm, and the aperture NA of the optical lens is 0.50.

Next, the reflectivity of the unrecorded portion and the maximum value of the block error rate of all the optical disks were measured by a signal evaluator for CD. The wavelength of the semiconductor laser used for the reading pickup of the signal evaluator for CD is 78.
0 nm, and the aperture NA of the optical lens is 0.45. First, the initial reflectance and the maximum value of the block error rate were measured, and then each optical disk was subjected to high temperature and high humidity (80 ° C,
(85% RH) for 1000 hours, and further, in a normal environment for a day and a night. Then, the reflectance of the unrecorded portion and the maximum value of the block error rate were measured again.
Table 1 shows the results.

[0032]

[Table 1]

In the optical disks of the present invention of Examples 1 to 9, the maximum value of the block error rate hardly changed before and after the high-temperature and high-humidity test. This is a result equivalent to that of the optical disk having the light reflection layer formed of gold in Reference Example 1. On the other hand, in Comparative Examples 1 and 2 having the silver light reflecting layer, the maximum value of the block error rate after the high-temperature and high-humidity test is about 10 times that before the test.

In Comparative Examples 3 and 4, the reflectance is small, and is lower than the standard value (65%) of the reflectance of the write-once optical disc (CD-R). In Comparative Example 5, the ruthenium content was low, and the chemical stability of the silver alloy was not sufficient, so that an increase in the block error rate was not suppressed. From the above results, the optical recording medium of the present invention is:
It has been found that the material has both high reflectivity and durability.

[0035]

According to the first and second aspects of the present invention, since the light reflecting layer is formed of a silver-ruthenium alloy or a silver-ruthenium-based alloy, the chemical properties of the light reflecting layer can be improved. There is an effect that the stability can be improved, and an optical recording medium having high reflectivity and excellent reliability and durability can be provided at low cost.

According to the third aspect of the present invention, there is provided a silver-ruthenium alloy having a high reflectance sufficient to compensate for the attenuation of the light beam by the organic dye recording layer, and excellent reliability and durability. Alternatively, there is an effect that a light-reflective layer of a silver-ruthenium-based alloy can provide a high-performance write-once optical recording medium at low cost.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a layer configuration of a write-once optical disc according to an embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 2 Organic dye recording layer 3 Light reflection layer 4 Protective layer

Claims (3)

[Claims] 1. An optical recording medium having a substrate and a light reflection layer laminated on the substrate, wherein the light reflection layer is made of a silver-ruthenium alloy containing 0.5 to 20 atomic% of ruthenium in silver. An optical recording medium, comprising: 2. An optical recording medium having a substrate and a light reflecting layer laminated on the substrate, wherein the light reflecting layer contains 0.5 to 10 atomic% of ruthenium in silver, and contains rhodium, An optical recording medium comprising a silver-ruthenium-based alloy containing 0.1 to 10 atomic% of at least one element selected from palladium, iridium, platinum and gold. 3. The optical recording medium according to claim 1, wherein an organic dye recording layer is provided between the substrate and the light reflection layer.