JP3371487B2 - Optical recording medium - Google Patents

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to an optical recording medium.
More specifically, the present invention relates to a writable optical disc that is compatible with a so-called compact disc (CD).

[0002]

2. Description of the Related Art Compact discs are widely used as audio software, computer game software, and electronic publishing media because of their large recording capacity and high productivity as software packages. However, in order to produce a compact disc, a die for transferring a record is required on the transparent substrate, and because of the cost of the die, when producing about 100 discs or less, one disc is used. The cost will be considerably higher.

In order to solve this problem, a compact disc having a recordable area that can be directly recorded on the disc, that is, a recordable compact disc, has been developed, instead of producing a recording disc through a mold. ing. A recordable compact disc is recordable and has the same reflectivity as a read-only compact disc, so that it can be played back by a read-only compact disc player or drive after recording.

This recordable compact disc is usually manufactured by sequentially providing a light absorbing layer made of an organic dye, a light reflecting layer made of a metal, and a protective layer made of an ultraviolet curable resin on a transparent substrate.

[0005]

In a recordable compact disc which has been put to practical use and is on the market, in order to obtain a high reflectance of 65% or more and a high corrosion resistance with respect to the wavelength of a read laser beam, a light reflection is required. Although gold and an alloy containing gold as the main component are used for the layer, the cost is a major problem because gold is expensive.

On the other hand, silver, which is inexpensive and has a high reflectance comparable to that of gold,
When a metal such as copper or aluminum and an alloy containing them as a main component are used as the light reflecting layer, a change over time in disk characteristics such as a decrease in reflectance and an increase in error due to corrosion of the light reflecting layer is likely to occur. It was difficult to produce a recordable compact disc with sufficient reliability for the usage environment.

The present invention solves the above-mentioned problems of the prior art, and retains the same life and reliability as a recordable optical disc using gold having a high corrosion resistance as a light reflecting layer, while reflecting less expensive metal. The purpose of the present invention is to provide a low-cost optical disk suitable as a recordable compact disk by making it possible to use as a layer. In order to overcome the above-mentioned problems, the present inventors diligently studied the corrosion form of silver and a light-reflecting layer containing silver as a main component, and as a result, the progress of corrosion from the surface of the light-reflecting layer in contact with the protective layer was observed. We have come to the knowledge that the degree determines the life of the entire disc.

Based on this finding, as a result of further investigation on the above-mentioned corrosion prevention, the protective layer was selected from the group consisting of triazine amine compounds, mercaptobenzimidazole compounds, thiodipropionate compounds and dithiocarbamate salts. By using an ultraviolet curable resin containing at least one compound selected,
It has been found that a progress of corrosion of the light reflecting layer is extremely suppressed, and a recordable optical disk having the same disk reliability as that when gold is used as the light reflecting layer is obtained, and the present invention has been achieved.

That is, the gist of the present invention is an optical recording medium in which a light absorbing layer, a silver or light reflecting layer containing silver as a main component, and a protective layer are sequentially laminated on a transparent substrate, and the protective layer is a triazine amine compound. An optical recording medium comprising an ultraviolet curable resin containing at least one compound selected from the group consisting of a mercaptobenzimidazole compound, a thiodipropionate compound and a dithiocarbamate.

The optical recording medium of the present invention will be described in detail below. The optical recording medium of the present invention comprises a transparent substrate, a light absorbing layer, a silver or light reflecting layer containing silver as a main component, and a protective layer, which are sequentially laminated. As the material of the transparent substrate,
Examples thereof include plastics such as polycarbonate, polymethylmethacrylate, and amorphous polyolefin, or glass. As these transparent substrates, those having a thickness of about 1 to 2 mm and spiral guide grooves are used.

Materials for the light absorbing layer include cyanine dyes, squarylium dyes, croconium dyes, azurenium dyes, triarylamine dyes, anthraquinone dyes, metal-containing azo dyes, and dithiol metal complex salt dyes, which are organic dyes. Indoaniline metal complex dyes, phthalocyanine dyes, naphthalocyanine dyes, intermolecular CT dyes, and the like are preferable, and they are used alone or in a mixture, or in the form of addition of a deterioration inhibitor, a binder, and the like.

As a method for forming a light absorbing layer containing an organic dye, a method in which an organic dye is dissolved in an organic solvent and spin-coated directly or through another layer on a transparent substrate is preferably used. A vapor deposition method can also be used for a dye having a sublimation property such as a system dye. Further, as the material of the light absorption layer, GeSb which is an inorganic thin film is used.
Chalcogenide alloys such as Te and TeSe and TbFe
Rare earth-transition metal alloys such as Co can also be used.

The thickness of the light absorption layer is determined according to the wavelength used, the optical constant of the reflection layer, the material of the light absorption layer, etc., in consideration of the recording sensitivity to the power of the recording light such as laser light, the performance coefficient, and the like. It is appropriately selected and is usually in the range of 100Å to 5 μm. The light absorption layer may be provided on both sides of the transparent substrate or may be provided on one side. The light-reflecting layer silver or a metal thin film containing silver as a main component is formed on the light-absorbing layer directly or through another layer by a sputtering method or a vacuum deposition method.
The film thickness is preferably 0 to 200 nm.

On the light-reflecting layer thus formed, at least one compound selected from the group consisting of triazine amine compounds, mercaptobenzimidazole compounds, thiodipropionate compounds and dithiocarbamate salts. An ultraviolet curing agent containing is coated and cured by irradiation with ultraviolet rays to form a protective layer.

As the triazine amine compound, the compound represented by the following general formula [I] is preferably used.
-R ¹ in the general formula [I] is a hydrocarbon group, -OR ^11, -S
It represents R ¹² or ^{-NR 13 R 14, R 11,} R 12, R 13 and R
Each ¹⁴ represents a hydrogen atom or a hydrocarbon group. R ¹ , R
Preferable examples of the hydrocarbon group represented by ¹¹ , R ¹² , R ¹³ and R ¹⁴ include an alkyl group, an alkenyl group and an aryl group.

[0016]

[Chemical 1]

A mercaptobenzimidazole compound and
As the compound, a compound represented by the following general formula [II] is preferable.
Used. -R in the general formula [II]²Is a hydrocarbon group,
OR ^{twenty one}Or-NR^{twenty two}R^{twenty three}Represents R^{twenty one}, R^{twenty two}And R^{twenty three}Is
Each represents a hydrogen atom or a hydrocarbon group. R², R^{twenty one},
R^{twenty two}And R^{twenty three}The hydrocarbon group represented by is alkyl
A group, an alkenyl group and an aryl group are preferred.

[0018]

[Chemical 2]

As the thiodipropionate compound, the compound represented by the following general formula [III] is preferably used. In general formula [III], -R ³¹ and -R ³² each represent a hydrocarbon group, preferably a higher alkyl group and a higher alkenyl group having 9 or more carbon atoms, or an aryl group.

[0020]

[Chemical 3]

As the dithiocarbamate, a compound represented by the following general formula [IV] is preferably used. In general formula [IV], -R ⁴¹ and -R ⁴² each represent a hydrocarbon group, preferably an alkyl group, an alkenyl group or an aryl group. M represents lithium, sodium, potassium or a substituted ammonium ion.

[0022]

[Chemical 4]

As the ultraviolet curing agent, it is preferable to use an acrylic ultraviolet curing agent, which is selected from the group consisting of triazine amine compounds, mercaptobenzimidazole compounds, thiodipropionate compounds and dithiocarbamate salts. At least one compound,
Usually, 0.001 to 0.1% by weight, preferably 0.01
It is melted at a ratio of about 0.05% by weight and coated on the light reflecting layer by a method such as spin coating or screen printing. The thickness of the protective layer can be set arbitrarily, but is 2 to 20 μm
It is preferable to set it to the degree.

[0024]

The optical recording medium of the present invention comprises a light absorbing layer, a silver or light reflecting layer containing silver as a main component, and a protective layer, which are sequentially laminated on a transparent substrate, and the triazine amine compound is added to the protective layer.
By using an ultraviolet curable resin containing at least one compound selected from the group consisting of mercaptobenzimidazole compounds, thiodipropionate compounds and dithiocarbamate, the corrosion resistance of the light reflecting layer is significantly improved. .

As a result, it is possible to obtain an optical recording medium having a high reliability and a long life, which has the same reliability as that of the case where gold is used as the light reflecting layer and has a small change in characteristics over time.

[0026]

EXAMPLES The present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples unless it exceeds the gist. 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 dissolving the metal-containing azo dye represented by the following structural formula in methyl cellosolve at 2.2% by weight (weight to solvent), filtering and then spin-coating on the above substrate. A film was formed. After applying the dye layer coating, drying was performed in an oven at 80 ° C. for 10 minutes to completely evaporate the solvent in the dye layer. The film thickness of the dye layer was selected to have a high reflectance and was set to 120 nm.

[0028]

[Chemical 5]

Then, as a light reflecting layer on the light absorbing layer,
100 nm thick silver was formed by DC magnetron sputtering in argon gas. Here, a triazine amine compound represented by the following structural formula was dissolved in an ultraviolet curing agent SD-318 (manufactured by Dainippon Ink and Chemicals, Inc.) in a proportion of 0.02% by weight, then spin-coated, and an ultraviolet irradiation device was used. Was irradiated with ultraviolet rays and cured to form a protective layer.

[0030]

[Chemical 6]

With respect to the obtained recordable compact disc, an EFM signal was recorded by an optical disc evaluation device DDU-1000 (manufactured by Pulstec Co., Ltd.) and subjected to a high temperature and high humidity test for 500 hours at a temperature of 85 ° C. and a humidity of 85%. Later, when it was reproduced with a commercially available CD player and the change in C1 error was measured, only a slight increase in C1 error was seen. The results are shown in Table-1.

Example 2 Recording is possible in the same manner as in Example 1 except that the UV curing agent SD-318 used for forming the protective layer contains a mercaptobenzimidazole compound represented by the following structural formula. A compact disc was manufactured.

[0033]

[Chemical 7]

When the obtained disk was tested in the same manner as in Example 1, a slight increase in C1 error was observed. The results are shown in Table-1. Example 3 Compact recordable in the same manner as in Example 1 except that the thiodipropionate compound represented by the following structural formula was contained in the UV curing agent SD-318 used for forming the protective layer. A disk was prepared.

[0035]

[Chemical 8]

When the obtained disk was tested in the same manner as in Example 1, a slight increase in C1 error was observed. The results are shown in Table-1. Example 4 A recordable compact disc was prepared in the same manner as in Example 1 except that the UV curing agent SD-318 used for forming the protective layer contained the dithiocarbamate represented by the following structural formula. went.

[0037]

[Chemical 9]

When the obtained disk was tested in the same manner as in Example 1, a slight increase in C1 error was observed. The results are shown in Table-1. Example 5 An ultraviolet curing agent SD-318 used for forming a protective layer was allowed to contain 0.02% by weight of an equimolar mixture of a triazine thiamine compound and a thiodipropionate compound represented by the following structural formulas. A recordable compact disc was prepared in the same manner as in Example 1 except that the compact disc was used.

[0039]

[Chemical 10]

When the obtained disk was tested in the same manner as in Example 1, a slight increase in C1 error was observed. The results are shown in Table-1. Example 6 A recordable compact disc was produced in the same manner as in Example 5 except that a silver-aluminum alloy having a thickness of 100 nm (silver: 85 atom%, aluminum: 15 atom%) was used as the light reflecting layer. .

When the obtained disk was tested in the same manner as in Example 1, a slight increase in C1 error was observed. The results are shown in Table-1. Comparative Example 1 A recordable compact disc was produced in the same manner as in Example 1 except that the UV curing agent SD-318 used for forming the protective layer was used as it was.

When the obtained disk was tested in the same manner as in Example 1, a huge increase in C1 error was observed. The results are shown in Table-1. Comparative Example 2 A recordable compact disc was produced in the same manner as in Example 6 except that the UV curing agent SD-318 used for forming the protective layer was used as it was.

When the obtained disk was tested in the same manner as in Example 1, a huge increase in C1 error was observed. The results are shown in Table-1. Reference Example 1 A recordable compact disc was manufactured in the same manner as in Comparative Example 1 except that gold having a thickness of 100 nm was used as the light reflecting layer.

When the obtained disk was tested in the same manner as in Example 1, a slight increase in C1 error was observed. The results are shown in Table-1. Reference Example 2 A recordable compact disc was manufactured in the same manner as in Example 1 except that gold having a thickness of 100 nm was used as the light reflecting layer.

When the obtained disk was tested in the same manner as in Example 1, a slight increase in C1 error was observed. The results are shown in Table-1.

[0046]

[Table 1] The following is clear from Table-1.

In Comparative Examples 1 and 2, a large increase in C1 error due to corrosion of the light reflecting layer was observed after the high temperature and high humidity test. On the other hand, in Examples 1 to 6 to which the present invention was applied, there was little increase in the C1 error even after the high temperature and high humidity test, and the cases of Reference Example 1 and Reference Example 2 using gold as the light reflecting layer were compared. Equivalent disk reliability is obtained.

[0048]

Industrial Applicability According to the present invention, a highly reliable optical recording medium excellent in high temperature and high humidity resistance can be produced at low cost, and is industrially very useful.

Continuation of front page (56) Reference JP-A-4-318339 (JP, A) JP-A-3-104037 (JP, A) JP-A-2-215588 (JP, A) JP-A 64-43825 (JP , A) JP 62-28291 (JP, A) JP 59-213039 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) G11B 7/24

Claims (4)

(57) [Claims] 1. An optical recording medium comprising a transparent substrate, a light absorbing layer, a silver or a light reflecting layer containing silver as a main component, and a protective layer, which are sequentially laminated, wherein the protective layer is a triazine amine compound or a mercaptobenzimidazole compound. An optical recording medium comprising an ultraviolet curable resin containing at least one compound selected from the group consisting of a compound, a thiodipropionate compound and a dithiocarbamate. 2. A triazine amine compound, mercapto
Benzimidazole compounds, thiodipropionic acid S
From the group consisting of ter compounds and dithiocarbamates
The compounding amount of the selected compound is 0.
The optical recording medium according to claim 1, which is 001 to 0.1% by weight.
body. 3. The light absorbing layer is made of a light absorbing organic dye.
The optical recording medium according to claim 1, which is formed. 4. The thickness of the light reflecting layer is 50 to 200 nm.
And 65% or more of the reading laser light wavelength
4. The light according to claim 1, which has a reflectance of
recoding media.