JPH07251567A - Optical recording medium - Google Patents

Abstract

PURPOSE:To reduce the cost of an optical recording medium such as a write- once compact disk by forming a light absorbing layer of a mixture of a specific metal-containing azo compd. and an org. dye other than the metal-containing azo compd. and forming a light reflection layer of a silver or silver alloy membrane. CONSTITUTION:In an optical recording medium constituted by successively laminating a light absorbing layer, a light reflection layer and a protective layer on a transparent substrate, the light absorbing layer is formed of a mixture of a metal-containing azo compd. represented by the general formula (wherein R<1> and R<2> are a hydrogen atom, an alkyl group which may be substituted, an aryl group, an alkenyl group or a cycloalkyl group, rings A, B may have a substituent and M is a metal atom) and an org. dye other than the metal-containing azo compd. and the light reflection layer is formed of a silver or silver alloy membrane. As the org. dye, a cyanine dye or a phthalocyanine dye is used.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to an optical recording medium. Specifically, it relates to an optical recording medium suitable for a write-once compact disc using an organic dye.

[0002]

2. Description of the Related Art An optical disc has a larger recording capacity than a conventional recording medium and can be randomly accessed.
It is widely used as a reproduction-only medium for audio software, computer software, game software, electronic publishing, and the like. On the other hand, write-once and rewritable recordable optical discs having an organic recording layer and an inorganic recording layer based on various recording principles have been developed and some of them have been put to practical use.

One of them is a recordable compact disc (CD-WO), which is capable of additional recording and has a reflectance equivalent to that of a read-only compact disc. It has the feature of being reproducible with. This recordable compact disc is usually produced by sequentially providing a light absorbing layer made of an organic dye such as a cyanine dye, a light reflecting layer made of a metal and a protective layer made of an ultraviolet curable resin on a transparent substrate having a guide groove, The record is 1
Deformation of the light absorption layer and its adjacent layer due to the heat mode using the laser beam narrowed down to about μm
It is performed due to alteration.

[0004]

In a recordable compact disc which has been put to practical use and is on the market, a light reflecting layer has a high reflectance of 65% or more and a high corrosion resistance with respect to the wavelength of the reading laser beam. In many cases, gold and alloys containing gold as a main component are used, but since gold is expensive, it is a big problem in terms of cost.

On the other hand, when a metal such as silver, copper or aluminum, which is inexpensive and has a high reflectance comparable to that of gold, and an alloy containing them as a main component are used as the light reflecting layer, the organic dye in the adjacent light absorbing layer is used. Promotes corrosion of the light-reflecting layer, which tends to cause changes in disc characteristics over time such as increased errors and decreased recording sensitivity, making it difficult to produce recordable compact discs with sufficient reliability for the operating environment. Met.

The present invention solves the above-mentioned conventional problems, and uses an inexpensive metal light reflecting layer without impairing the life and reliability of an optical recording medium using expensive gold as a light reflecting layer. By making it possible, it is an object to provide a low-cost optical recording medium suitable for a recordable compact disc.

[0007]

As described above, when silver, copper, aluminum or an alloy containing them as a main component is used as the light reflecting layer instead of gold having high corrosion resistance, the light absorbing layer is There is a problem that the corrosion of the light reflecting layer is promoted from the interface between the light reflecting layer and the light reflecting layer, so that the characteristics of the disk tend to change with time such as an increase in errors and a decrease in recording sensitivity.

In order to overcome the above-mentioned problems, the inventors of the present invention have conducted extensive studies on effective combinations of reflective layer materials and organic dyes. As a result, the light reflective layer contains silver or silver as a main component. In the case of using a thin film of an alloy, it has been found that by adding a metal-containing azo dye to the organic dye forming the light absorption layer, it is possible to significantly suppress the temporal change of the disk characteristics.

On the other hand, on the other hand, when the metal-containing azo compound is added to the organic dye forming the light absorbing layer, the recording and reproducing characteristics inherent to the organic dye forming the light absorbing layer may be impaired. As a result of a study on an effective metal-containing azo compound, the metal-containing azo compound represented by the general formula [I] shows little change in recording / reproducing characteristics even when added to the organic dye constituting the light absorption layer, and silver or It was found that not only the corrosion of the light reflecting layer made of a thin film of a silver alloy is suppressed, but also the crystallization and the light deterioration of the light absorbing layer are suppressed and the high temperature and high humidity resistance is also improved, and the present invention was completed. .

That is, the gist of the present invention is an optical recording medium in which a light absorbing layer, a light reflecting layer and a protective layer are sequentially laminated on a transparent substrate, and the light absorbing layer is represented by the general formula [I]. An optical recording medium comprising a mixture of a metal azo compound and an organic dye other than the metal-containing azo compound, and the light reflecting layer comprising a thin film of silver or a silver alloy.

[0011]

[Chemical 2]

(In the formula, R ¹ and R ² are each independently a hydrogen atom, an optionally substituted alkyl group,
It represents an aryl group, an alkenyl group or a cycloalkyl group, and ring A and ring B may have a substituent. M represents a metal element. ) The optical recording medium of the present invention will be described in detail below. Examples of the transparent substrate used in the present invention include plastics such as polycarbonate, polymethylmethacrylate, and amorphous polyolefin, or glass. As these transparent substrates, those having a guide groove formed in a spiral shape having a thickness of 1.2 mm are usually used.

The optical recording medium of the present invention is characterized in that the light absorbing layer comprises a metal-containing azo compound represented by the following general formula [I] and an organic dye other than the metal-containing azo compound.

[0014]

[Chemical 3]

In the general formula [I], R ¹ and R
² each independently represent a hydrogen atom, an optionally substituted alkyl group, an aryl group, an alkenyl group or a cycloalkyl group, and among these, particularly 1 to 1 carbon atoms.
An alkyl group of 5 is preferred. Ring A may have a substituent, and examples of the substituent include an alkyl group, an alkoxy group, a thioalkoxy group, an arylthio group, an aryloxy group, an aralkyl group, an aryl group, a halogen atom, a cyano group and a nitro group. , An ester group, a carbamoyl group, an acyl group, an acylamino group, a sulfamoyl group, a sulfinic acid group, an amino group, a hydroxyl group, a phenylazo group, a pyridinoazo group, a vinyl group and the like, and these substituents further have a substituent. May be. Preferred among these substituents are a hydroxyl group, a halogen atom, a cyano group, a nitro group and a substituent,
Alkyl group having 1 to 25 carbon atoms, alkoxy group having 1 to 25 carbon atoms, thioalkoxy group having 1 to 25 carbon atoms, and 6 carbon atoms
To C30 arylthio group, C1 to C25 alkylsulfamoyl group, C6 to C30 phenylsulfamoyl group, C1 to C25 alkylsulfinic acid group, and C6 to C30 phenylsulfinic acid Group, carbon number 6 to 3
0 pyridinoazo group, C2-C26 ester group, C2-26 alkylcarbamoyl group, C6-C3
0 phenylcarbamoyl group, an acyl group having 2 to 26 carbon atoms, acylamino group having 1 to 25 carbon atoms, -NR ³ R ⁴
(R ³ and R ⁴ each independently represent a hydrogen atom, an optionally substituted alkyl group having 1 to 25 carbon atoms or a phenyl group, and R ³ and R ⁴ are bonded to each other. It may form a 5-membered ring or a 6-membered ring.), -C
R ⁵ = C (CN) R ⁶ (R ⁵ is a hydrogen atom or a carbon number of 1 to
6 represents an alkyl group, and R ⁶ represents a cyano group or an alkoxycarbonyl group having 2 to 7 carbon atoms. ) And the like, and more preferably an alkyl group having 1 to 10 carbon atoms, which may have a substituent such as a halogen atom, and 1 to 1 carbon atoms.
Examples thereof include an alkoxy group having 0 and a thioalkoxy group having 1 to 10 carbon atoms.

Ring B may have a substituent other than the --NR ¹ R ² group and the --SO ₃ group, and as such a substituent, an alkyl group, preferably an alkyl group having 1 to 10 carbon atoms; Examples thereof include an alkoxy group, preferably an alkoxy group having 1 to 10 carbon atoms; a halogen atom and the like, and the substituents such as these alkyl group and alkoxy group may further have a substituent such as a halogen atom.

M is not particularly limited as long as it is a metal capable of forming a chelate compound with an azo compound which is a ligand, but nickel, cobalt, iron, ruthenium, rhodium, palladium, copper, osmium, iridium, A transition element such as platinum is preferable, and nickel and cobalt are particularly preferable. Here, in the general formula [I], particularly preferable R ¹ , R ² , a substituent of ring A, and a substituent of ring B (-NR ¹
Table 1 shows combinations of R ² groups and groups other than —SO ₃ groups) and M.

[0018]

[Table 1]

The metal-containing azo compound may be used alone or in combination of several kinds. Other organic dyes other than the metal-containing azo compound used in the light absorbing layer include cyanine dyes, squarylium dyes, croconium dyes, azulenium dyes, triarylamine dyes, anthraquinone dyes, and dithiol metal complex salt dyes. , Indoaniline metal complex dyes, phthalocyanine dyes, naphthalocyanine dyes, intermolecular CT dyes, etc. are used.
In particular, cyanine dyes and phthalocyanine dyes, and especially indolenine cyanine dyes are preferably used.

Other organic dyes other than the metal-containing azo compounds are
You may use each individually or in mixture of several types.
It is effective that the mixing ratio of the metal-containing azo compound in the light absorption layer is 5% by weight or more, more preferably 10 to 90% by weight. The metal-containing azo compound of the present invention is different from usual deterioration inhibitors, and since the metal-containing azo compound itself has good characteristics as an optical recording material, even if the compounding ratio of the metal-containing azo compound is increased. There is little change in the recording and reproducing characteristics, and it has the advantage that the characteristics peculiar to organic dyes are not impaired.

In the light absorption layer, in addition to the above-mentioned organic dye and metal-containing azo compound, a deterioration inhibitor for the organic dye,
A binder or the like may be added. As a method of forming the light absorbing layer, a method of dissolving an object to be coated in an organic solvent and spin coating the transparent substrate is preferably used. A thin film of silver or a silver alloy is used for the light reflection layer, and a method such as a sputtering method or a vacuum deposition method is used for forming the film. Particularly, the sputtering method is preferably used, and the light reflection layer has an incident angle with respect to the substrate surface. In the X-ray diffraction spectrum measured by the θ-2θ method with θ as θ, the X-ray diffraction intensity by the (111) plane is I ₁₁₁ and the X-ray diffraction intensity by the (200) plane is I.
_When it is set to ₂₀₀ , it is preferable to use a polycrystalline silver thin film such that I ₂₀₀ / I ₁₁₁ ≦ 0.2. The thickness of the light reflecting layer is preferably 50 to 200 nm. When a silver alloy thin film is used for the light reflection layer, its alloy composition is not particularly limited as long as it has a high reflectance for the reproduction laser light,
In order to improve corrosion resistance, additional elements such as rhodium, palladium, platinum, titanium, molybdenum, zirconium, tantalum, tungsten and vanadium may be contained in a range of 5 atomic% or less.

In order to improve the corrosion resistance of the surface of the light reflection layer on the protective layer side, it is selected from triazine thiol compounds, triazine amine compounds, mercaptobenzimidazole compounds, thiodipropionate compounds and dithiocarbamate. Surface treatment with at least one compound may be applied. As the material of the protective layer formed on the light reflection layer, it is preferable to use an ultraviolet curable resin, particularly an acrylic ultraviolet curable resin, which is applied to a thickness of 2 to 20 μm by a spin coating method or a screen printing method, It is formed by being cured by ultraviolet irradiation. Further, the ultraviolet curable resin, as an anticorrosive agent for the surface of the protective layer side of the light reflection layer, from triazine thiol compounds, triazine amine compounds, mercaptobenzimidazole compounds, thiodipropionate compounds, dithiocarbamate salts You may use by making it contain at least 1 sort (s) of compound selected. A second protective layer or a printing layer such as a label may be provided on the protective layer, if necessary.

[0023]

EXAMPLES The present invention will be described in more detail with reference to examples below, but the present invention is not limited to the following examples as long as the gist thereof is not exceeded. Example 1 As a transparent substrate, a recording groove having a meandering tracking groove for a compact recordable disk, having a diameter of 120 mm,
A polycarbonate substrate having a thickness of 1.2 mm was used.

The light absorbing layer was prepared by mixing a cyanine dye represented by the following structural formula (1) and a metal-containing azo compound represented by the following structural formula (2) at a weight ratio of 1: 1 and then mixing the mixture with 2.
It was dissolved in methyl cellosolve at a concentration of 4% by weight, filtered, and then formed into a film on the substrate by spin coating. After applying the dye, drying was performed in an oven at 80 ° C. for 10 minutes in order to completely evaporate the solvent in the dye layer.

[0025]

[Chemical 4]

Then, as a light reflecting layer on the light absorbing layer,
Silver having an average thickness of 100 nm was formed by the DC magnetron sputtering method. Further, an ultraviolet curing agent SD-318 (manufactured by Dainippon Ink and Chemicals, Inc.) was applied on the light reflecting layer by a spin coating method to a thickness of 3 μm, and was irradiated with ultraviolet rays by an ultraviolet irradiation device to be cured, A protective layer was formed.

The obtained recordable compact disc was recorded with an optical disc evaluation device DDU-1000 (manufactured by Pulstec Industrial Co., Ltd.) for EFM signals and evaluated for initial characteristics, and was subjected to 500 at a temperature of 80 ° C. and a humidity of 90%. After the high-temperature high-humidity test for an hour, when it was played back with a commercially available CD player and the change in the block error rate was measured, only a slight increase in error was seen. The results are shown in Table-2. Example 2 A cyanine-based dye represented by the following structural formula (3), a dithiol nickel complex salt-based dye represented by the following structural formula (4) and a metal-containing azo compound represented by the following structural formula (5) were mixed at a weight ratio of 6: 1. A recordable compact disc was prepared in the same manner as in Example 1 except that the mixture was dissolved in methyl cellosolve at a concentration of 2.4% by weight to prepare a coating solution.

[0028]

[Chemical 5]

When the obtained disk was tested in the same manner as in Example 1, only a slight increase in error was observed. The results are shown in Table-2. Example 3 A cyanine dye represented by the structural formula (3), a cyanine dye represented by the following structural formula (6), and a metal-containing azo compound represented by the following structural formula (7) were mixed in a weight ratio of 3: 5: 2.
Then, a recordable compact disc was prepared in the same manner as in Example 1 except that the coating liquid was prepared by dissolving the mixture in methyl cellosolve at a concentration of 2.4% by weight.

[0030]

[Chemical 6]

When the obtained disk was tested in the same manner as in Example 1, a slight increase in error was observed. The results are shown in Table-2. Example 4 A cyanine dye represented by the following structural formula (8) and a metal-containing azo compound represented by the following structural formula (9) were mixed at a weight ratio of 9: 1, and then the mixture was added at a concentration of 2.4% by weight. A recordable compact disc was prepared in the same manner as in Example 1 except that the coating liquid was prepared by dissolving the coating liquid in tetrafluoropropanol.

[0032]

[Chemical 7]

When the obtained disk was tested in the same manner as in Example 1, only a slight increase in error was observed. The results are shown in Table-2. Example 5 A phthalocyanine-based dye represented by the following structural formula (10) and a metal-containing azo compound represented by the structural formula (5) were mixed at a weight ratio of 6: 4, and the mixture was added at a concentration of 2.4% by weight. A recordable compact disc was prepared in the same manner as in Example 1 except that the coating liquid was prepared by dissolving the coating liquid in tetrafluoropropanol.

[0034]

[Chemical 8]

When the obtained disk was tested in the same manner as in Example 1, only a slight increase in error was observed. The results are shown in Table-2. Example 6 A phthalocyanine dye represented by the following structural formula (11) and a metal-containing azo compound represented by the above structural formula (9) were mixed at a weight ratio of 8: 2, and the mixture was added at a concentration of 2.4% by weight. A recordable compact disc was prepared in the same manner as in Example 1 except that the coating liquid was prepared by dissolving the coating liquid in tetrafluoropropanol.

[0036]

[Chemical 9]

When the obtained disk was tested in the same manner as in Example 1, only a slight increase in error was observed. The results are shown in Table-2. Comparative Example 1 A recordable compact disc was prepared in the same manner as in Example 1 except that the cyanine dye represented by the structural formula (1) was dissolved in methyl cellosolve at a concentration of 2.4% by weight to prepare a coating solution. Was prepared. When the obtained disk was tested in the same manner as in Example 1, a large increase in errors was found. The results are shown in Table-2.

Comparative Example 2 The cyanine dye represented by the structural formula (3) and the dithiol nickel complex salt dye represented by the structural formula (4) were mixed at a weight ratio of 6: 1, and then the mixture was mixed with 2.4. A recordable compact disc was prepared in the same manner as in Example 1 except that the coating solution was prepared by dissolving the solution in methyl cellosolve at a concentration of wt%. When the obtained disk was tested in the same manner as in Example 1, a large increase in errors was found. The results are shown in Table-2.

Comparative Example 3 The cyanine dye represented by the structural formula (3) and the cyanine dye represented by the structural formula (6) were mixed in a weight ratio of 3: 5, and the mixture was added in an amount of 2.4% by weight. A recordable compact disc was produced in the same manner as in Example 1 except that the coating solution was prepared by dissolving the solution in methyl cellosolve at the concentration of. When the obtained disk was tested in the same manner as in Example 1, a large increase in errors was found.
The results are shown in Table-2.

Comparative Example 4 The procedure of Example 1 was repeated except that the cyanine dye represented by the structural formula (8) was dissolved in tetrafluoropropanol at a concentration of 2.4% by weight to prepare a coating solution. A recordable compact disc was prepared. When the obtained disc was tested in the same manner as in Example 1,
A large increase in errors was seen. The results are shown in Table-2.

Comparative Example 5 The procedure of Example 1 was repeated except that the phthalocyanine dye represented by the structural formula (10) was dissolved in tetrafluoropropanol at a concentration of 2.4% by weight to prepare a coating solution. A recordable compact disc was prepared. When the obtained disk was tested in the same manner as in Example 1, a large increase in errors was found. The results are shown in Table-2.
It was shown to.

Comparative Example 6 The procedure of Example 1 was repeated except that the phthalocyanine dye represented by the structural formula (11) was dissolved in tetrafluoropropanol at a concentration of 2.4% by weight to prepare a coating solution. A recordable compact disc was prepared. When the obtained disk was tested in the same manner as in Example 1, a large increase in errors was found. The results are shown in Table-2.
It was shown to.

Reference Example In each of Examples 1 to 6 and Comparative Examples 1 to 5, recordable compact discs were produced in the same manner except that the light reflecting layer was made of gold. Each of the obtained disks was tested in the same manner as in Example 1. The results are shown in Table 2 in correspondence with each Example and Comparative Example.

[0044]

[Table 2]

The following is clear from Table-2. In Comparative Examples 1 to 6, after the high temperature and high humidity test, a large increase in block error due to corrosion of the light reflecting layer is observed. On the other hand, in Examples 1 to 6 to which the present invention was applied, the increase in block error was small even after the high temperature and high humidity test, and the disk reliability was the same as that of the reference example using gold as the light reflecting layer. Has been obtained.

[0046]

According to the present invention, a highly reliable optical recording medium having excellent durability can be manufactured at low cost and is industrially very useful.

Claims (3)

[Claims] 1. An optical recording medium comprising a transparent substrate, a light-absorbing layer, a light-reflecting layer, and a protective layer, which are sequentially laminated, wherein the light-absorbing layer contains a metal-containing azo compound represented by the following general formula [I]. An optical recording medium comprising a mixture with an organic dye other than a metal azo compound, and the light reflecting layer comprising a thin film of silver or a silver alloy. [Chemical 1] (In the formula, R ¹ and R ² are each independently a hydrogen atom, an optionally substituted alkyl group, an aryl group,
It represents an alkenyl group or a cycloalkyl group, and ring A and ring B may have a substituent. M represents a metal element. ) 2. The optical recording medium according to claim 1, wherein the organic dye other than the metal-containing azo compound is a cyanine dye. 3. The optical recording medium according to claim 1, wherein the organic dye other than the metal-containing azo compound is a phthalocyanine dye.