JP2985067B2 - 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, and more particularly to an optical recording medium having a light reflecting layer of silver or an alloy containing silver as a main component.

[0002]

2. Description of the Related Art Conventionally, gold or an 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 needed 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 Japanese Patent Application Laid-Open No. 57-212638).
Moreover, since silver is much cheaper than gold, it satisfies both high reflectivity and economy, and can be applied to the light reflection layer of a CD-R which is a recordable optical disk.

[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, there has been proposed a method in which another metal element is added to silver to form a silver alloy (for example, JP-A-61-134945,
See JP-A-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. Further, when silver is alloyed, there is a problem that the reflectance is lowered, which is not preferable in terms of the performance of the optical recording medium.

[0007] Also, JP-A-6-231488, JP-A-7-10
In Japanese Patent No. 5572, corrosion resistance is improved by treating the surface of a light reflection layer formed of silver with a triazine thiol-based compound, a triazine amine-based compound, a mercaptobenzimidazole-based compound, and an optical disc having high reliability is obtained. It is disclosed. The present inventor also produced an optical recording medium in which a silver light reflecting layer was treated with these compounds and performed an environmental resistance test, but the reliability and durability were improved as compared with those without treatment. But it was still not enough.

The present invention has been made in view of such conventional problems,
In an optical recording medium that has a higher reflectance than gold and is inexpensive and has silver or a silver-based alloy in the light reflection layer, the chemical stability of silver or silver alloy is improved, and the reliability and durability are improved. An object of the present invention is to provide an optical recording medium excellent in the above.

[0009]

For this reason, in the invention according to claim 1, an optical recording medium is laminated on a substrate and the surface of the optical recording medium which is laminated on the substrate and which is opposite to the substrate side is formed by a general formula (I) )

[0010]

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And a light reflecting layer made of silver or an alloy containing silver as a main component, which is treated with a dipyridyl compound represented by the formula (1). That is, a dipyridyl compound is attached to the surface of a light reflecting layer made of silver or an alloy containing silver as a main component. Here, R1 to R8 are
A hydrogen atom, a halogen atom, a hydroxyl group, an alkoxyl group, an amino group, a nitro group, a mercapto group, a cyano group,
Sulfonic acid group, acyl group, aldehyde group, carboxyl group, hydrocarbon group, alkylthio group, aryl group, aryloxy group, arylthio group, acyloxy group, ester group, thioester group, thiocarboxylic acid group, -NHR,
—NRR ′ (R and R ′ are alkyl groups).

Similarly, in the invention according to claim 2, an optical recording medium is laminated on a substrate and the surface on the side opposite to the substrate side is formed by a general formula (II)

[0013]

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And a light reflection layer made of silver or an alloy containing silver as a main component, which is treated with a phenanthroline compound represented by the formula (1). Here, R1 'to R8' are
A hydrogen atom, a halogen atom, a hydroxyl group, an alkoxyl group, an amino group, a nitro group, a mercapto group, a cyano group,
Sulfonic acid group, acyl group, aldehyde group, carboxyl group, hydrocarbon group, alkylthio group, aryl group, aryloxy group, arylthio group, acyloxy group, ester group, thioester group, thiocarboxylic acid group, -NHR,
—NRR ′ (R and R ′ are alkyl groups). Although the length of the alkyl group of -NHR and -NRR 'is not particularly limited, it usually has 1 to 20 carbon atoms.
Is preferably used.

Any of the compounds represented by the general formulas (I) and (II) can be used in the form of a hydrate.
With such a configuration, the chemical stability of silver or an alloy containing silver as a main component, which forms the light reflection layer, is improved. 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. Is most effective when used as a write-once optical recording medium which is required to have high reflectivity and economic efficiency. In this case, a structure in which layers such as a protective layer, an adhesive layer, and a second substrate are sequentially stacked on the light reflecting layer may be adopted.

[0016]

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 a 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
It is about 40 to 360 mm. On the surface of the substrate, a predetermined pattern such as a pre-pit on which information is recorded or a groove or the like for tracking or addressing is provided as required.

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 sublimability 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 reflective layer 4 and the dye thin film in consideration of recording sensitivity to light energy used for recording such as a laser, a performance coefficient, and the like. Is appropriately selected depending on the material of the material, and is usually in the range of 120 to 150 nm.

The light reflecting layer 3 is formed of silver or an alloy containing silver as a main component. The element which forms a silver alloy when mixed with silver is not particularly limited, but for example, Al, Au,
Cu, Cr, Ni, Pt, Sn, In, Pd, Ti, Fe
, Ta, W, Zn and the like. Although the composition ratio of silver in the alloy is not particularly limited, it is preferably at least 50 atomic%, particularly preferably at least 80 atomic%, in order to obtain a high reflectance in the light reflecting layer. The thickness of the light reflecting layer 3 is usually 10
Set to ~ 200nm. If it is thinner than this, a high reflectance cannot be obtained, and if it is thicker, 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. In the present invention, after forming the light reflecting layer 3 made of silver or an alloy containing silver as a main component, the light reflecting layer 3 is formed.
Is treated with the above-described dipyridyl-based compound represented by the general formula (I) or the phenanthroline-based compound represented by the general formula (II). In general, R
1 to R8 (or R1 'to R8') each represent a hydrogen atom, a halogen atom, a hydroxyl group, an alkoxyl group, an amino group, a nitro group, a mercapto group, a cyano group, a sulfonic acid group, an acyl group, an aldehyde group, a carboxyl group, Hydrocarbon group, alkylthio group, aryl group, aryloxy group, arylthio group, acyloxy group, ester group, thioester group, thiocarboxylic acid group, -NHR, -NR
R '(R and R' are alkyl groups) may be used, but R1 and R8 (or R1 'and R8') are preferably hydrogen atoms because of their tendency to adsorb to silver. Also,
R2 to R7 (or R2 'to R7')
May form a condensed ring. R2 to R7 (or R2 'to R7') in terms of ease of synthesis and cost
Is preferably a hydrogen atom, a methyl group, or a phenyl group.

Specifically, compounds having the following structures are mentioned.

[0023]

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Further, these compounds may be hydrates.
The surface treatment of the light reflection layer 3 with the compound is performed by dissolving the compound in an appropriate solvent to form a treatment liquid, applying the treatment liquid on the light reflection film, and then drying. The application method is not particularly limited, but spin coating or dip coating is preferably used.

The solvent for the treatment liquid is not particularly limited, but an alcohol-based or ether-based solvent is preferred from the viewpoint of solubility of the compound and ease of handling, and examples thereof include ethanol and diethyl ether. The concentration of the compound in the solvent is usually preferably from 0.0001 to 5.0% by weight, more preferably from 0.001 to 0.1% by weight. If the concentration is lower than this, the treatment effect of the compound on the light reflecting layer 3 is not sufficient, and if the concentration is higher than this, no remarkable improvement in the effect is observed.

The drying (volatilization) of the solvent can be performed by a spin drying method at room temperature. If necessary, drying can be promoted by heating and dehumidifying the atmosphere. By performing such a treatment, the dipyridyl-based compound represented by the general formula (I) or the phenanthroline-based compound represented by the general formula (II) adhered to the surface of the light reflecting layer 3 made of silver or a silver alloy. As a result, the chemical stability of the light reflection layer 3 is significantly improved.

After the light reflecting layer 3 is subjected to the surface treatment by the above-described method, the protective layer 4 is provided to improve the friction resistance and the corrosion resistance.
A single layer or a plurality of layers are provided. The protective layer 4 is preferably composed of an organic substance in which various organic or inorganic fillers are mixed, and in particular, a substance obtained by curing a radiation-curable compound or a composition thereof by radiation such as an electron beam or ultraviolet rays. Preferably. The thickness of the protective layer is usually about 0.1 to 100 μm in total, and can be formed by ordinary methods such as spin coating, gravure coating, spray coating, and roll coating.

In the write-once optical disk 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. This reflected light is attenuated by the organic dye recording layer 2, but the light reflecting layer 3 using silver or a silver alloy has a reflectance similar to that of gold, and obtains reflected light having an intensity that does not cause any practical problem. be able to.

Further, since the light reflecting layer 3 has been subjected to the above-mentioned surface treatment, the reliability and durability, which have conventionally been regarded as the disadvantages of the light reflecting layer using silver or an alloy containing silver as a main component, are low. It shows improved reliability and durability equivalent to those of optical disks using gold for the light reflection layer. 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. In the case of a rewritable optical recording medium, Is a dielectric layer in addition to the substrate and the light reflecting layer described above,
One having a layer such as a phase change recording layer, a protective layer, an adhesive layer, and a second substrate can be considered. 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.

[Examples] In order to specifically show the effects of the present invention, examples will be described below. (Example 1) As a sample, a diameter of 120 mm and a thickness of 1.2 mm
Using a polycarbonate substrate having a spiral guide groove, a write-once optical disc having a cyanine-based organic dye in an organic dye recording layer and silver in a light reflection layer was manufactured.

First, a cyanine dye is dissolved in an organic solvent,
After filtering through a filter to remove impurities, the mixture was applied on a substrate by a spin coater (manufactured by Able) to form an organic dye recording layer. Subsequently, heat treatment was performed in an oven to completely remove the solvent, and then a 100 nm-thick silver light reflecting layer was formed by a DC magnetron sputtering apparatus.

Next, the following structural formula

[0034]

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The monohydrate of 1,10-phenanthroline represented by the following formula was dissolved in ethanol to prepare a solution having a concentration of 0.01% by weight, and the solution was applied on a silver light reflection film by spin coating. Thereafter, spin drying was performed for 10 seconds. And
An ultraviolet-curable resin was applied on the surface-reflected silver light-reflective film by spin coating, and cured by irradiation with ultraviolet light to form a protective layer. The thickness of the protective layer after curing was 5 μm.

Example 2 A sample was prepared in the same manner as in Example 1 except that the light reflecting layer was formed of a silver-titanium alloy (10 atomic% of titanium). (Example 3) The compound used for the surface treatment of the light reflecting layer was represented by the following structural formula

[0037]

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A sample was prepared in the same manner as in Example 1, except that 4,7-dimethyl-1,10-phenanthroline was used. Example 4 The compound used for the surface treatment of the light reflecting layer was represented by the following structural formula

[0039]

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A sample was prepared in the same manner as in Example 1, except that 2,2'-dipyridyl represented by the following formula was used. Example 5 As a substrate, a polycarbonate substrate on which pits (concavities and convexities) corresponding to 74 minutes of data were formed in advance and an organic dye recording layer was not provided was used.
In the same manner as in the first embodiment, a read-only optical disk (CD-RO
M) was prepared.

Comparative Example 1 A sample was produced in the same manner as in Example 2 except that the surface treatment of the light reflecting layer was not performed. (Comparative Example 2) The compound used for the surface treatment of the light reflecting layer was represented by the following structural formula

[0042]

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A water solution was used as a solvent to prepare a 0.02% by weight solution of the triazineamine compound represented by the formula:
A sample was prepared in the same manner as in Example 1 except that the light reflecting layer surface was treated by spin coating. (Comparative Example 3) A sample was produced in the same manner as in Example 5, except that the surface treatment of the light reflecting layer was not performed.

Reference Example 1 A sample was prepared in the same manner as in Comparative Example 1 except that the light reflecting layer was formed of gold. Data was recorded on each sample other than Example 5 and Comparative Example 3 obtained as described above. The data is transmitted and converted from the host computer by CD writing software, and the CD recorder (CDW-900E manufactured by SONY) is used.
The EFM signal was recorded for 74 minutes. 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 maximum value of the block error rate for all samples was measured by a CD signal evaluator.
The wavelength of the semiconductor laser used for the reading pickup of the CD signal evaluation device is 780 nm, and the aperture NA of the optical lens is 0.45. First, the maximum value of the initial block error rate was measured, and then each sample was allowed to stand for 1000 hours under conditions of high temperature and high humidity (80 ° C, 85% RH). , The maximum value of the block error rate was measured. Table 1 shows the results.

[0046]

[Table 1]

In the samples of the present invention of Examples 1 to 5, 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 sample of Reference Example 1 having a reflective layer formed of gold. On the other hand, in Comparative Examples 1 and 3 in which the surface treatment was not performed on the silver light reflection layer, the maximum value of the block error rate after the high-temperature and high-humidity test was about 10 times that before the test.

In Comparative Example 2 in which the surface of the silver light reflecting layer was treated with a compound different from that of the present invention, the block error after the high-temperature and high-humidity test was smaller than Comparative Examples 1 and 3. The maximum value of the rate has increased about four times. From the above results, it has been clarified that the optical recording medium of the present invention has both high reflectivity and durability.

[0049]

According to the first and second aspects of the present invention, the chemical stability of the light reflecting layer made of silver or an alloy containing silver as a main component is improved, and a high reflectance and an excellent light reflecting layer are obtained. There is an effect that an optical recording medium having reliability and durability can be provided at low cost.

According to the third aspect of the present invention, silver or silver having high reflectivity sufficient to compensate for the attenuation of the light beam by the organic dye recording layer and excellent reliability and durability is mainly used. A light reflecting layer of an alloy as a component is obtained, and there is an effect that a high-performance write-once optical recording medium can be provided 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

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G11B 7/24 538

Claims (3)

(57) [Claims] A substrate laminated on the substrate and having a surface opposite to the substrate side;
General formula [R1 to R8 each represent a hydrogen atom, a halogen atom, a hydroxyl group, an alkoxyl group, an amino group, a nitro group, a mercapto group, a cyano group, a sulfonic acid group, an acyl group, an aldehyde group, a carboxyl group, a hydrocarbon group, an alkylthio group, Aryl group, aryloxy group, arylthio group, acyloxy group, ester group, thioester group, thiocarboxylic acid group, -NHR, -NRR '(R and R' are alkyl groups)
And a light reflecting layer made of silver or an alloy containing silver as a main component, which is treated with a dipyridyl-based compound represented by the following formula: 2. A substrate, and a surface laminated on the substrate and opposite to the substrate,
General formula [R1 ′ to R8 ′ each represent a hydrogen atom, a halogen atom, a hydroxyl group, an alkoxyl group, an amino group, a nitro group, a mercapto group, a cyano group, a sulfonic acid group, an acyl group, an aldehyde group, a carboxyl group, a hydrocarbon group, an alkylthio group; Group, aryl group, aryloxy group, arylthio group,
Silver or silver treated with a phenanthroline-based compound represented by any one of an acyloxy group, an ester group, a thioester group, a thiocarboxylic acid group, -NHR and -NRR '(R and R' are alkyl groups). An optical recording medium comprising: a light reflecting layer made of an alloy having the following formula: 3. An organic dye recording layer is provided between the substrate and the light reflection layer.
An optical recording medium according to claim 1.