JPH11131218A - Metallic thin coating film and optical recording medium using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an optical recording medium having metallic thin coating film showing gold before. SOLUTION: On a transparent substrate 10, a light absorbing layer 20 contg. at least one kind of organic pigments, a metallic thin coating film 30 in which carbon is incorporated into the surface layer of alloy thin coating film essentially consisting of silver (50 to 95 pts.wt.) and copper (50 to 5 pts.wt.) so as to regulate the total content of silver and copper to >=80 pts.wt. as a light reflecting layer and a protecting layer 40 are successively formed to produce an optical recording medium 50.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a metal thin film, and more particularly, to a metal thin film which is colored golden by adding carbon to a surface layer, and which can be written on a so-called compact disk using the metal thin film. Related to optical disks.

[0002]

2. Description of the Related Art Optical recording media represented by compact discs have been widely used as media for audio software, computer software, and electronic publishing because of their large recording capacity and high productivity as software packages. ing. To create an optical recording medium exclusively for reading as represented by a conventional compact disc,
A mold for transferring a record on the transparent substrate is required. However, since the cost for manufacturing the mold is high, the cost per disk is considerably high when manufacturing several hundred disks.

In order to solve this problem, an optical recording medium having a recordable area that can be directly recorded on a disk, that is, a compact disk, is not used for producing a recording disk using a mold. Recordable (below,
It is called CD-R. And the like, and an optical recording medium capable of recording by laser light has been developed.

[0004] A description will be given below using a CD-R as an example. C
The DR is capable of recording information and has the same reflectance as a read-only compact disc, so that information can be recorded and reproduced by a read-only compact disc player or a read-only compact disc drive. It has the feature that reading is also possible. Usually, an optical recording medium capable of recording such as a CD-R has a light absorbing layer made of an organic dye, a light reflecting layer made of a metal thin film, and a protective layer made of an ultraviolet curable resin on a transparent substrate. It is produced by forming sequentially.

[0005]

In a CD-R which has already been put to practical use and is commercially available, it is necessary to obtain a reflectance of 65% or more with respect to a laser beam having a wavelength of 780 nm for reading, and a light reflection layer. In order to prevent the migration and the decrease in the reflectivity due to the chemical reaction, as the light reflection layer, a stable gold and an alloy mainly composed of gold are used. However, since gold is expensive, the production cost is high. This is an obstacle to reducing. On the other hand, in the case where aluminum having the same reflectance as gold and an alloy containing the same as the main component are used as the light reflection layer in order to reduce the manufacturing cost, a decrease in the reflectance due to migration or a chemical reaction or an error may be caused. High-reliability CDs that can withstand long-term storage because disk characteristics such as increase tend to change over time.
-R was difficult to produce. When silver is used,
Because of the so-called metallic or silver color, there is a disadvantage that the design of gold is lost.

On the other hand, it has been proposed to use a corrosion-resistant alloy such as stainless steel for improving the corrosion resistance. However, many of them require a large amount of additional components necessary for exhibiting the corrosion resistance. As a result, the reflectivity of the alloy decreases. Further, since the anticorrosion mechanism forms a passivation film on the surface of the alloy, a decrease in reflectance was inevitable when used as a reflection film. In this case, of course, the design of gold is impaired. An object of the present invention is to use a metal thin film layer, which is cheaper than gold, as a light reflection layer while maintaining the same design and reliability as an optical recording medium using gold having stability as a light reflection layer. An object of the present invention is to provide an optical recording medium capable of recording information.

[0007]

Means for Solving the Problems The inventors of the present invention have made intensive studies to solve the above-mentioned problems, and found that by adding carbon to a specific alloy-based thin film, it was possible to obtain a golden design. The inventors have found that an excellent metal thin film can be obtained, and that an optical recording medium excellent in design and reliability can be obtained using the metal thin film, and arrived at the present invention.

That is, the gist of the present invention is that (1) a metal thin film characterized in that carbon is contained in the surface layer of an alloy thin film containing silver and copper as main components, and (2) the alloy thin film contains silver. It contains 50 to 95 parts by weight, and contains 50 to 5 parts by weight of copper, and the total content of silver and copper is 80 to 99.
(1) The metal thin film according to (1), wherein the carbon content is 1 × 10 ¹⁶ to 1 × 10 ^18.
Characterized in that it is a atom / cm ² (1) or a metal thin film according to (2), and (4) a transparent substrate, a light absorbing layer containing at least one organic dye, as a light reflecting layer ( (1) An optical recording medium characterized by sequentially forming the metal thin film and the protective layer according to (3), and (5) the metal thin film having a thickness of 50 to 200 nm. An optical recording medium according to (4).

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An optical recording medium according to the present invention will be described with reference to FIG. As the material of the transparent substrate used in the present invention,
Plastics such as polycarbonate, polymethyl methacrylate, and amorphous polyolefin, or materials having high light transmittance to visible light such as glass can be suitably used. These transparent substrates usually have a thickness of 1-2.
A guide groove having a diameter of about mm and formed concentrically or spirally is used.

The light absorbing layer is made of a material such as a phthalocyanine dye, a naphthalocyanine dye, a cyanine dye, a squarylium dye, a croconium dye, an azurenium dye, a triarylamine dye, which are organic dyes.
Preferred are anthraquinone dyes, metal-containing azo dyes, dithiol metal complex dyes, indoaniline metal complex dyes, and intermolecular CT dyes. These dyes may be used alone or in combination of two or more. Can be. Usually, a deterioration inhibitor, a binder and the like are added to these coloring materials for use. Specific examples of the phthalocyanine dyes include, for example, JP-A-3-62878 and JP-A-4-226.
390 and JP-A-3-215466.

Specifically, Pd-phthalocyanine having one 1-isopropyl-isoamyloxy group at one of the α-positions of each of the four benzene rings in the phthalocyanine molecule, and four respective benzenes in the phthalocyanine molecule Ni-phthalocyanine having one bis (isopropyl) -methoxy group at one α-position of the ring, one bis (isobutyl) -methoxy at one α-position of each of the four benzene rings in the phthalocyanine molecule Cu- having a group
Phthalocyanine, one 4-t-butyl- at one of the α-positions of each of the four benzene rings in the phthalocyanine molecule.
Pd-phthalocyanine having a cyclohexyloxy group, Ni-phthalocyanine having one t-dodecylmercaptoxy group at one of the α-positions of the four respective benzene rings in the phthalocyanine molecule, four respective benzenes in the phthalocyanine molecule Examples include Pt-phthalocyanine having one 1,3-dimethyl-butoxy group at one of the α-positions of the ring.

As a method for forming the light absorbing layer containing an organic dye, a method in which the organic dye is dissolved in an organic solvent and spin-coated on a transparent substrate directly or via another layer can be suitably used. The thickness of the light-absorbing layer is appropriately selected according to the wavelength to be used, the optical constant of the reflective layer, and the material of the light-absorbing layer in consideration of the coefficient of performance of the recording sensitivity with respect to the power of the recording light such as laser light used for recording. It is readily understood by those skilled in the art that the
μm. The film thickness of the light absorbing layer, in spin coating, by appropriately changing the concentration of a solution of an organic dye dissolved in an organic solvent or the number of rotations during spin coating, and when using an evaporation method, the evaporation time or It can be easily adjusted by appropriately changing the power at the time of vapor deposition. The light absorbing layer may be provided on one side or both sides of the transparent substrate.

As the light reflecting layer, a metal thin film that is colored golden by adding carbon to the surface layer of an alloy thin film mainly composed of silver and copper is used. The alloy thin film contains 50 silver.
A metal thin film containing about 95 parts by weight, 50 to 5 parts by weight of copper, and a total of 80 to 99.99 parts by weight of silver and copper is preferable. If the content of silver is too small, the reflectance is reduced, and the reflection color does not become golden, the redness becomes strong, and the film becomes poor in design. On the other hand, if the amount of silver is too large, the reflectance is high, but a normal metallic color, that is, a so-called silver-colored reflection color, which is also poor in design in the sense that it does not exhibit a golden color. The copper content is complementary to that of silver; if it is too high, the reflection color will be red, and if it is too low, it will be metallic.

The total content of silver and copper in the alloy thin film is 80
~ 99.99 parts by weight are preferred. If the amount is too small, the reflectivity will be reduced and the color will be golden, but it is not suitable for an optical recording medium. Metals to be added other than silver and copper include noble metals such as gold, platinum and palladium. Examples of other metals include nickel, zinc, tin, cobalt, aluminum, tungsten, titanium, manganese, vanadium, molybdenum, antimony, and the like, and oxygen other than metals. For fine adjustment of color, zinc, nickel, tin, titanium, and oxygen are preferably used. The metal components other than silver and copper may be 0.01 parts by weight or less, but if the purity is further increased, the cost will be increased industrially.

The composition can be easily confirmed by X-ray fluorescence analysis. The composition in the depth direction of the film can also be determined by Auger electron spectroscopy using a sputtering method. The alloy thin film is formed on the light absorption layer directly or through another layer by a sputtering method or a vacuum evaporation method, and is preferably a polycrystalline film or an amorphous film having a thickness of 50 to 200 nm. In the formation of an alloy by a sputtering method, sputtering can be performed using an alloy as a target, or can be separately sputtered from a plurality of targets by a co-sputtering method. In general, the composition of the target and the composition of the formed film do not always match due to factors such as segregation, selective sputtering, and errors in measuring equipment, but the difference between the composition of the target and the composition of the film has a great effect on the present invention. It does not give.

If necessary, the surface of the alloy thin film may be subjected to a chemical treatment with a tridiantiol-based compound or a benzimidazole-based compound. As the protective layer formed on the alloy thin film, it is preferable to use a hard material such as an acrylic ultraviolet curing resin. Usually, a thickness of 2 is formed on the alloy thin film layer by spin coating directly or through another layer.
After coating with a thickness of ２０20 μm, it is cured by ultraviolet irradiation.

In order to produce a golden color, it is necessary to include carbon in the surface layer of the alloy thin film. In particular,
In the case where the alloy thin film is covered with a resin or the like, at the interface between the resin and the alloy thin film, a state in which carbon permeates into the alloy thin film side to form a surface layer may be realized. The depth at which carbon permeates the alloy thin film depends on the processing method, but is usually 50 to 200 nm.

In the method of permeating carbon into a surface layer according to the present invention, heat treatment in an atmosphere containing carbon is the simplest. For example, the atmosphere containing carbon means that the alloy thin film is exposed to a gas containing carbon such as methane, benzene, or alcohol. As an example of specific conditions, heating may be performed at 100 ° C. for one hour in the atmosphere. What is important here is that the surface layer is heated at a temperature of 150 ° C. or less to convert the surface layer to a golden color. Since a polymer substrate is usually used for an optical recording medium, heat treatment at a high temperature cannot be performed. By using the alloy composition of the present invention, it is possible to develop a golden color at a low temperature, and once the color is developed, the subsequent color change hardly occurs.

Further, as another example of the method of infiltrating carbon, carbon may be supplied at the time of producing an alloy thin film.
When an alloy thin film is formed by a sputtering method, a gas such as methane, ethane, benzene, carbon dioxide, or carbon monoxide may be mixed with a sputtering gas such as argon during sputtering. In this case, since the alloy thin film is thin, it does not matter if carbon is contained in the entire thin film, but even in that case,
Its content should be in the range of 1 × 10 ¹⁶ to 1 × 10 ¹⁸ atoms / cm ² .

Further, as another example, there is a method in which a carbon source on a solid is placed adjacent to the surface of the alloy thin film, and carbon is supplied from the carbon source. In other words, 1
A gold color can be formed by attaching carbon atoms of from × 10 ¹⁶ to 1 × 10 ¹⁸ atoms / cm ² by a sputtering method or a vacuum evaporation method and appropriately performing a heat treatment.

Alternatively, if there is a certain rise in temperature during film formation even without heating, carbon atoms adhering to the surface of the alloy thin film diffuse into the vicinity of the surface of the alloy thin film to form a surface layer. It can be substantially impregnated with carbon.
Further, a resin may be used as a carbon source adjacent to the surface of the alloy thin film. The resin is not particularly limited, but polyester-based, acrylic-based, and urethane-based resins are preferably used. The resin may be dissolved in a solvent and applied to the surface of the alloy thin film, or an alloy thin film may be formed on a film or sheet made of the resin by a sputtering method or a vacuum evaporation method. After realizing a state in which the alloy thin film and the resin layer are adjacent to each other, for example, a heat treatment (100 ° C.)
For 1 hour. A metal thin film is formed as described above. The thickness of the obtained metal thin film is usually 50 to
200 nm.

The atomic composition of the metal thin film formed by the above method is determined by Auger electron spectroscopy (AES), inductively coupled plasma (ICP), Rutherford backscattering (RBS).
Can be measured. Among these methods, Auger electron spectroscopy that is highly sensitive to light elements is particularly preferably used. The layer configuration and the film thickness can be measured by Auger electron spectroscopy observation in the depth direction, cross-sectional observation using a transmission electron microscope, or the like. When it is necessary to monitor the carbon content, the relationship between the infiltration conditions and the infiltration rate is clarified in advance, and then the infiltration is performed, or the film thickness after the infiltration of the carbon is monitored using a quartz oscillator or the like. The oxidation state of the surface layer is determined by Auger electron spectroscopy or X-ray photoelectron spectroscopy (XP
S) can be evaluated.

After being processed into an optical recording medium, the cross section is exposed, and information on the oxidation state is provided by cross section observation with a transmission electron microscope. In addition, as for the state of color development, a heating temperature and a heating time may be appropriately selected. The golden color of the metal thin film is first determined visually. If necessary, evaluation was made by measuring chromaticity by a method according to JIS-8729. As a standard, a * = − 1 to 9 and b * = 30 to 50 were set as the golden ranges. The reflectance of the metal thin film itself is 750 to
It is preferably at least 80% in the wavelength range of 800 nm.

[0024]

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples, but the present invention is not limited to the following examples. Example 1 An alloy thin film having a thickness of 120 nm was formed on a polycarbonate substrate by a DC magnetron sputtering method using a target of 90 parts by weight of silver and 10 parts by weight of copper. The color of the thin film was metallic. When this sample was heated at 100 ° C. for 1 hour in an atmosphere containing 1% by volume of benzene, the sample developed a golden color. When the carbon content of the surface layer was measured, it was 4 × 10 ¹⁶ atoms / c.
m ² .

Example 2 An alloy thin film having a thickness of 100 nm was formed on a polycarbonate substrate by a DC magnetron sputtering method using a target of 90 parts by weight of silver and 10 parts by weight of copper. The color of the thin film was metallic. 2 × 10 carbon atoms were applied to the surface of this sample from a high-purity isotropic graphite target by DC magnetron sputtering.
^When penetrated by ¹⁶ atoms / cm ² , it developed a golden color.

Example 3 An alloy thin film having a thickness of 80 nm was formed on a polycarbonate substrate by a DC magnetron sputtering method using a target of 60 parts by weight of silver and 40 parts by weight of copper. The color of the thin film was metallic. 2 × 10 ¹⁶ carbon atoms were applied to the surface of this sample from a high-purity isotropic graphite target by DC magnetron sputtering.
When penetrated by atoms / cm ² , it developed a golden color.

Example 4 Using a target of 60 parts by weight of silver, 25 parts by weight of copper, and 15 parts by weight of zinc, a film having a thickness of 180 nm was formed on a polycarbonate substrate.
Alloy thin films were prepared by DC magnetron sputtering.
The color of the thin film was metallic. When 1 × 10 ¹⁶ atoms / cm ² of carbon atoms were permeated into the sample surface layer from a high-purity isotropic graphite target by a DC magnetron sputtering method,
It developed a golden color.

Example 5 Polysilicon was prepared using a target of 90 parts by weight of silver and 10 parts by weight of copper.
DC thin film of 100nm alloy thin film on carbonate substrate
It was manufactured by magnetron sputtering. At this time, argon
Was mixed with 40% by volume of methane gas and sputtered.
The color of the obtained thin film was golden. Thin film composition analysis
According to Auger electron spectroscopy, 12 atom% of carbon
It was found that the film contained 6 × 10¹⁷original
Child / cm ^TwoWas estimated to contain
Was.

Example 6 An alloy thin film having a thickness of 120 nm was formed on a polycarbonate substrate by a DC magnetron sputtering method using a target of 60 parts by weight of silver and 40 parts by weight of copper. At this time, sputtering was performed by mixing 20% by volume of methane gas with argon.
The color of the obtained thin film was golden. When the composition analysis of the thin film was performed by Auger electron spectroscopy, it was found that the thin film contained 6 atomic% of carbon. Therefore, it was found that the thin film contained 3 × 10 ¹⁷ carbon atoms / cm ^2. Was estimated.

COMPARATIVE EXAMPLE 1 A polycarbonate was prepared using a target of 98 parts by weight of silver and 2 parts by weight of copper.
-An alloy thin film with a thickness of 120 nm is
It was produced by the guntron sputtering method. At this time, argon
Sputtering was performed by mixing 60% by volume of methane gas. Profit
The color of the obtained thin film was metallic, that is, silver. Thin film
Was analyzed by Auger electron spectroscopy.
It was found that it contained atomic% of carbon,
9 × 10 ¹⁷Atom / cm^TwoContains carbon atoms of
Was estimated.

Comparative Example 2 An alloy thin film having a thickness of 120 nm was formed on a polycarbonate substrate by a DC magnetron sputtering method using a target of 45 parts by weight of silver and 55 parts by weight of copper. At this time, sputtering was performed by mixing 4% by volume of methane gas with argon. The color of the obtained thin film was red close to the color of metallic copper. The composition analysis of the thin film was performed by Auger electron spectroscopy.
Since it was found that the thin film contained 2 atomic% of carbon, it was estimated that the thin film contained 6 × 10 ¹⁶ atoms / cm ² of carbon atoms.

Comparative Example 3 An alloy thin film having a thickness of 120 nm was formed on a polycarbonate substrate by a DC magnetron sputtering method using a target of 90 parts by weight of silver and 10 parts by weight of copper. Carbon atoms were infiltrated into the sample surface layer by DC magnetron sputtering at 5 × 10 ¹⁵ atoms / cm ^2, and the color of the obtained thin film was metallic.
It was so-called silver.

Comparative Example 4 An alloy thin film having a thickness of 120 nm was formed on a polycarbonate substrate by a DC magnetron sputtering method using a target of 90 parts by weight of silver and 10 parts by weight of copper. 5 × 10 ¹⁸ atoms / cm ² of carbon atoms were permeated into the surface of this sample from a high-purity isotropic graphite target by DC magnetron sputtering, but the color of the obtained thin film was dark brown. Table 1 shows the results of Examples 1 to 6 and Comparative Examples 1 to 4 described above.

[0034]

[Table 1] Table 1 shows that a metal film having a golden color and a high reflectance can be obtained according to the present invention. next,
Examples of the optical recording medium will be described, but the present invention is not limited to the following examples.

Example 7 As a transparent substrate, for a compact disk capable of recording, a periodically meandering tracking groove was provided.
A polycarbonate substrate having a thickness of 20 mm and a thickness of 1.2 mm was used. Polycarbonate resin substrate with guide groove (diameter 1
3.5 mm of a phthalocyanine-based dye, that is, a Pd-phthalocyanine having one 1-isopropyl-isoamyloxy group at the α-position of each of the four benzene rings constituting the phthalocyanine. 2000% by weight of dimethylcyclohexane solution
pm, spin-coated at 70 ° C for 2 hours, 100n
A light absorbing layer having a thickness of m was formed.

Further, 90 parts by weight of silver and 10 parts by weight of copper
Film thickness of 100 on polycarbonate substrate
nm alloy thin film produced by DC magnetron sputtering
Was. At this time, methane gas of 40% by volume is mixed with argon
And sputtered. The color of the obtained thin film is golden.
Was. The composition analysis of the thin film was performed by Auger electron spectroscopy.
It turns out that it contains 12 atomic% of carbon.
6 × 10 in the thin film ¹⁷Atom / cm^TwoContains carbon atoms
It was estimated that it had been. UV on this reflective layer
Use line-curing resin SD-17 (Dai Nippon Ink Chemical Industry)
After pin-coating, irradiate with UV light to protect 6μm thick
A layer was formed to produce an optical recording medium.

When viewed from above, the protective resin exhibited a golden color, and an excellent design was obtained. This optical recording medium is 780
linear velocity of 2.8 m using a Philips writer (CDD-521) equipped with an
/ S, and an EFM signal was recorded at a laser power of 9.5 mW. The obtained optical recording medium was subjected to a temperature of 85 ° C. and a humidity of 8
A high-temperature and high-humidity test was performed for 500 hours under the condition of 5%.
5 sun (500 mW / cm ² ) light irradiation test at 60 ° C.
For 100 hours, and changes in reflectance and C1 error before and after the test were measured. As a result, both after the high-temperature and high-humidity test and after the light irradiation test, only a slight decrease in the reflectance and a slight increase in the C1 error were observed.

Example 8 An alloy thin film having a thickness of 100 nm was formed on a polycarbonate substrate by a DC magnetron sputtering method using a target of 90 parts by weight of silver and 10 parts by weight of copper. The color of the alloy thin film was metallic. When 5 × 10 ¹⁵ atoms / cm ² of carbon were infiltrated into the sample surface layer by DC magnetron sputtering, a golden color was formed. Furthermore, after spin-coating an ultraviolet-curing resin SD-17 (manufactured by Dainippon Ink and Chemicals) on the metal thin film (light reflecting layer), a protective layer having a thickness of 6 μm is formed by irradiating ultraviolet rays to form an optical recording medium. Was prepared. An optical recording medium was produced in the same manner as in Example 5, except that the substrate was heated at 80 ° C. when irradiating ultraviolet rays. Also in this case, the reflection color of the metal thin film layer was colored golden, and the optical recording medium was excellent in design. The same evaluation as in Example 5 was performed, but only a slight decrease in reflectance and a slight increase in C1 error were observed after the high-temperature and high-humidity test and after the light irradiation test. Table 2 summarizes the results of the above examples.

[0039]

[Table 2] From Table 2, it is clear that by using the metal thin film of the present invention, it is possible to obtain an optical recording medium having excellent design properties and sufficiently high reliability.

[0040]

Industrial Applicability The present invention enables an optical recording medium having excellent design and reliability to be manufactured at low cost, and is industrially extremely useful.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a cross section of an embodiment of an optical recording medium.

[Explanation of symbols]

 Reference Signs List 10 transparent substrate 20 light absorbing layer containing organic dye 30 light reflecting layer of metal thin film 40 protective layer 50 optical recording medium

Claims (5)

[Claims] A metal thin film characterized in that carbon is contained in the surface layer of an alloy thin film containing silver and copper as main components. 2. The alloy thin film contains 50 to 95 parts by weight of silver, 50 to 5 parts by weight of copper, and has a total content of silver and copper of 80 to 99.99 parts by weight. The metal thin film according to claim 1, wherein 3. The metal thin film according to claim 1, wherein said carbon content is 1 × 10 ¹⁶ to 1 × 10 ¹⁸ atoms / cm ² . 4. A light absorbing layer containing at least one organic dye, a metal thin film according to claim 1 as a light reflecting layer and a protective layer are sequentially formed on a transparent substrate. Optical recording medium. 5. The optical recording medium according to claim 4, wherein said metal thin film has a thickness of 50 to 200 nm.