JPH0449091A - Optical data recording medium and preparation thereof - Google Patents

Abstract

PURPOSE:To suppress the optical deterioration of a dye in which an oxygen molecule is participated by specifying the oxygen content of a recording layer formed using an org. dye. CONSTITUTION:In a solvent coating type optical recording medium having a recording layer formed using an org. dye, the oxygen content of the recording layer is set to 10 ppm or less. That is, a dye coating solution with oxygen content of 10 ppm or less prepared by dissolving the org. dye in a solvent is used to form the recording layer. The recording layer 3 composed of the org. dye is provided on a substrate 2 having the unevenness of a preformat pattern and the oxygen content of the recording layer composed of the org. dye is adjusted to 10 ppm or less and a protective substrate 5 is further laminated to the recording layer through an adhesive layer 4.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical information recording medium with excellent photostability and a method for manufacturing the same.

[Prior Art] Conventionally, many proposals have been made to use a dye recording layer having a high reflective function for recording and reproducing light as a recording layer of an optical information recording medium. For example, JP-A-58-1149
89, JP 58-112790, JP 57-212639, JP 59-24692, JP 59-85791, JP 60-8
There are publications such as No. 3236. However, these dye recording layers have poor light resistance, and there is a problem in that the reflectance of the dye in the recorded and/or non-recorded areas changes due to, for example, a reproduction laser beam during reproduction of recorded information.

As a means to solve such problems, a method of adding a singlet oxygen quencher represented by a nickel dithio metal complex into the recording layer or protective layer is known, for example, as disclosed in JP-A-58-'175693. , Japanese Patent Publication No. 59-215
It has been reported in JP-A No. 11192, JP-A-59-1831117, JP-A-59-55794, etc.

In addition, in order to prevent the change in the reflectance of the dye as described above, a method of adding an infrared absorber having the structure shown below to the recording layer is disclosed in JP-A-60-163245 and JP-A-60-163245. This is reported in Publication No. 60-236131.

R: Alkyl group It is reported in Japanese Patent Publication No. 151346/1983. Attempts have been made to improve the photodeterioration of dye recording media caused by oxygen molecules by the methods described above.

On the other hand, these dye recording layers are formed by applying a solution of a solid dye dissolved in a solvent onto a substrate on which pregroups are formed using a wet coating method.

[Problems to be Solved by the Invention] The solvent used for wet coating of the dye is usually acetone, ethanol, dichloroethane, diacetone alcohol, etc., and the organic dye is usually dissolved in 2 to 4 wt % in these solvents. Further, the molecular weight of the dye used as the recording layer is usually about 600 to 1,200. Therefore, the dye dissolves in the amount of 1.7 Xl0-' moles per gram of solvent. On the other hand, the amount of oxygen molecules dissolved in these solvents is I per gram of solvent.
X 10-@ to 3 X 10-' moles. ("Chemical Handbook Basic Edition IIJ pages 15g to 165, published by Maruzen Co., Ltd. in 1986)" In this way, the molar concentration of the dye and the molar concentration of oxygen in the solution in which the dye is dissolved in a solvent are approximately the same.

Further, since these organic dyes are usually poorly soluble or have low solubility in organic solvents, sufficient stirring of the solution is performed in order to dissolve the organic dyes in the solvent. the result,
Not only the dye but also oxygen molecules are sufficiently dissolved in the solvent.

Therefore, in the conventional wet coating method for dyes, oxygen molecules dissolved in a dye solution are mixed into or adsorbed into the dye recording layer during the wet coating process of the dye recording layer, and these oxygen molecules cause the dye to The problem has been that the photodeterioration of the dye is accelerated, and the effect of the heavy ring oxygen quencher or dye stabilizer is halved. In the conventional coating method, the amount of oxygen adsorbed in the dye recording layer was 20 to 1100 pp as analyzed by gas chromatography.

The present invention was made in order to improve the drawbacks of such conventional techniques, and by reducing the amount of oxygen contained in the recording layer formed using an organic dye, oxygen molecules become involved. It is an object of the present invention to provide an optical information recording medium that suppresses photodeterioration of dyes and has excellent photostability, and a method for producing the same.

[Means for Solving the Problems] That is, the present invention provides a solvent-coated optical recording medium having a recording layer formed using an organic dye, in which the oxygen content contained in the recording layer is 1Oppm or less. An optical information recording medium characterized by:

The present invention also provides a method for manufacturing a solvent-coated optical recording medium having a recording layer formed using an organic dye, in which recording is performed using a dye coating solution in which an organic dye is dissolved in a solvent and has an oxygen content of 10 ppm or less. This is a method for manufacturing an optical information recording medium characterized by forming a layer.

The present invention will be explained in detail below.

FIG. 1 is a schematic cross-sectional view showing a typical example of an optical information recording medium (hereinafter referred to as an optical recording medium) of the present invention. In the figure, the optical recording medium of the present invention is provided with a recording layer 3 made of an organic dye on a substrate 2 having unevenness of a preformat pattern, and the oxygen content contained in the recording layer made of the organic dye is 1Oppm or less. It has been adjusted to be
Furthermore, a protective substrate 5 is laminated thereon via an adhesive layer 4. To protect the substrate surface, the substrate 2
A hard coat layer 1 is provided on the outer surface of.

In the present invention, the substrate 2 is preferably one that has few inconveniences in optical recording/reproduction, and when the recording/reproduction light is incident from the substrate side, it has a high transmittance for the light used. For example, acrylic resin, polyester resin, polycarbonate resin, vinyl resin, polysulfone resin, polyimide resin, polyacetal resin, polyolefin resin, polyamide resin, cellulose derivative, etc. can be used.

In addition, when the recording layer 3 is near the wavelength of the light to be used, for example, when the wavelength of the energy beam of the reproduction light is 6501 to 900 nm, the reflectance of the bits etc. formed in the colored recording area and the unrecorded area It is preferable that there is a large difference between the two wavelengths, and in order to record, it is necessary that there is absorption in the above wavelength range. Further, it is preferable that the reflectance of the recorded portion and the unrecorded portion is not easily changed depending on the energy beam of the reproduction light. In order to form an organic recording layer, it is preferable for mass production that the organic thin film can be continuously coated using a dye solution or dispersion system. For example, anthraquinone derivatives (especially those having an inkhurene skeleton), dioxazine compounds and their derivatives, triphuedithiazine compounds,
Phenanthrene derivatives, cyanine compounds, merocyanine compounds, biryllium compounds, xanthine compounds, triphenylmethane compounds, croconium dyes, azo dyes, crocones, azines, indigoids, polymethine dyes, azulenes, squalium derivatives, sulfide Mention may be made of pigments such as dyes and dithiolate complexes of metals.

Furthermore, known quencher-1 metal complexes, infrared absorbers, and the like can be added to these dyes.

An organic thin film made of such an organic dye can be formed by applying a dye solution in which the dye is dissolved or dispersed in a solvent and from which dissolved oxygen has been removed using a known coating method. For example, methods such as dip coating, spray coating, spinner coating, bar code coating, blade coating, roll coating, and curtain coating can be used. The thickness of the organic thin film is approximately 500 to 2000, preferably around 1000. In particular, it is desirable that the thickness be thin from the point of view of recording sensitivity, and thicker from the point of view of reproduction S/N ratio.
The optimal film differs depending on the type of dye.

As the adhesive used for the adhesive layer 4, any commercially available adhesive can be used as long as it does not adversely affect the recording layer, but hot-melt adhesives are particularly suitable for use due to their excellent workability. It will be done.

Any hot melt adhesive may be used as long as it has a melting point of about 80 to 110°C, has adhesive strength, and does not attack the recording layer (for example, polyolefin adhesives such as ethylene vinyl acetate adhesives are useful). be.

In addition, as the protective substrate 5, polymethyl methacrylate, polycarbonate, polysulfone, vinyl chloride, etc. can be used, but especially thin protective substrates are resistant to bending and have good adhesion to printing inks, etc. Polycarbonate, which is also inexpensive, is preferred.

Furthermore, a hard coat layer may be provided on the surface of the substrate or the entire surface of the recording medium, if necessary.

Next, the method for manufacturing the optical recording medium of the present invention can be carried out by forming a recording layer using a dye coating solution containing an organic dye dissolved in a solvent and having an oxygen content of 10 ppm or less.

As a method for removing dissolved oxygen in a dye coating solution in which the above-mentioned dye is dissolved in a solvent, (1) A gas having a higher affinity for the dye dissolving solvent than oxygen is dissolved in the dye solvent and replaced with oxygen gas.

Usually, dye dissolving solvents include acetone, ethanol,
Organic solvents such as isopropyl alcohol and dichloroethane are used, but the solubility of 0□ in these solvents is 2
I x 10-'~3x10-@moR% (30
~96 ppm). Also, C,1(4(ethylene)
, the solubility of C2H6 (ethane) gas etc. is 10-'m
oj)%, and it is possible to use ethanino or ethylene gas as a replacement gas for oxygen gas.

In addition, inert gas, N2. Alternatively, dissolving a dye in a solvent and stirring it in an atmosphere such as a rare gas is also effective in reducing dissolved oxygen in the solvent.

Furthermore, dissolved oxygen in the dye-dissolving solvent can be removed by a method such as (1) blowing an oxygen-adsorbing gas into the dye-dissolving solvent (2) bringing the dye-dissolving solvent into contact with an oxygen adsorbent.

In the case of the method (2), an apparatus as shown in FIG. 2 is used, and the oxygen adsorbing gas is poured into the dye solution 7 from a cylinder 6 containing the oxygen adsorbing gas 8.

As oxygen-adsorbing gases, CO, CO+COz mixed gas, Hz+CO2 mixed gas, etc. are known, and especially co+
co□ mixed gas is preferred.

As the oxygen adsorbent used in method (2), fine particles of transition metals such as iron are known, and those having low reactivity with organic dyes are particularly preferred. As a method of implementation, dissolved oxygen can be removed by boat fishing (as is known) by sealing an oxygen adsorbent in a column made of glass or the like and passing a solution through the column.

In this way, to prepare an optical recording medium using a dye-dissolving solvent from which dissolved oxygen has been removed by the method (1) or/and (2), it can be carried out in the following manner. That is, the recording layer can be formed by applying a coating solution made of a dye-dissolving solvent deoxidized by the above method to the substrate on which the pregroups are formed, and then removing the solvent.

In the present invention, the oxygen content contained in the formed recording layer is preferably 20 ppm or less, preferably 10 ppm or less; if it exceeds 20 ppm, the photodegradation rate of the dye recording layer increases as the oxygen content increases. It becomes faster and I don't like it.

Further, in the present invention, it is preferable that the oxygen content dissolved in the coating solution made of the deoxidized dye dissolving solvent is 10 ppm or less, preferably 5 ppm or less,
If it exceeds 10 ppm, photodeterioration of the dye will be accelerated during storage of the dye solution, and an optical recording medium with a low C/N value will be produced from the photodegraded dye solution, which is not preferable.

[Function] The optical recording medium of the present invention manufactured by the above method using a coating solution consisting of a dye-dissolving solvent prepared to have an oxygen content of 10 ppm or less can reduce the amount of oxygen adsorbed in the recording layer. The content is reduced to below loppm, and as a result, it becomes possible to reduce the deterioration of the dye medium caused by oxygen due to irradiation with sunlight or information reproducing laser light.

Furthermore, even when a quencher is mixed with a dye as is conventionally known, the effect of the quencher becomes even higher by removing dissolved oxygen in the dye coating solution as in the present invention.

[Example] The present invention will be explained in more detail below using Examples.

Example 1 Substrate: thickness 0.4 mm, size 85 mm x 54
A polymethyl methacrylate optical card substrate having track grooves with a width of 3 μm and a pitch of 12 μm on one side was produced by cast molding.

Next, a dye represented by the following structural formula (I) (manufactured by Nippon Kayaku Co., Ltd., 1R82
0), (C, H mountain N (γ flea N (CJa) a404e (I) diacetone with dissolved oxygen adjusted to 2 ppm or less using a mixed gas of nitrogen gas and ethylene gas 1:3 as a replacement gas. The dye solution was dissolved in an alcohol solution to a concentration of 2.5 wt %. Stirring for dissolution was performed under a nitrogen gas atmosphere. The dye solution was applied to a substrate using a gravure coater, and a recording layer with a thickness of 1000 mm was formed. I got it.

The solvent was dried under a nitrogen atmosphere to reduce adsorption of oxygen gas to the dye as much as possible.

The oxygen content contained in the recording layer was 10 ppm. Note that the oxygen content was measured by gel permeation gas chromatography (manufactured by Shimadzu Corporation).

Next, a polycarbonate protective substrate with a thickness of 0.3 mm was bonded using a hot melt adhesive (trade name: Hirodyne 7580, manufactured by Hirodyne Industries) with a thickness of 50 μm. The bonding was performed using a hot laminator under a nitrogen stream. Next, a hard coat layer made of (modified acrylic resin) was provided on the surface of the substrate to a thickness of 4 μm to prepare an optical card.

Comparative Example 1 Using the same materials as in Example 1, a dye equivalent to that in Example 1 was dissolved at 2.5 wt% in a diacetone alcohol solution from which dissolved oxygen had not been removed, and all were dissolved in an air atmosphere. I created an optical card medium.

Next, when the optical card media of Example 1 and Comparative Example 1 were continuously irradiated with a laser beam with a spot diameter of 5 μm and a laser beam power of 0.15 mW, as shown in FIG. The decrease in reflectance was slower than in Comparative Example 1, and by reducing the amount of oxygen molecules in the dye dissolving solvent to 2 ppm or less, the light resistance of the organic dye medium could be improved.

Example 2 A dye stabilizer represented by the following structural formula (II) was further mixed into the dye solution of Example 1 so that the weight ratio of the dye to the stabilizer was 4:1, An optical recording medium was obtained in the same manner as in Example 1.

CRO"° (■) Dye stabilizer: IRG-010 (manufactured by Nippon Kayaku) Comparative Example 2 Using the same material as in Example 2, removal of solvent oxygen in the dye solvent and coating process performed in Example 1 An optical recording medium having the same structure as in Example 2 was obtained by a conventionally known method without performing inert gas treatment in the coating solvent drying step and protective substrate lamination step.

0.2 mW to the optical recording media obtained in Example 2 and Comparative Example 2
When a laser beam with a spot diameter of 3 μm was continuously irradiated with a laser power of
The results shown are obtained.

Table 1 As is clear from the results in Table 1, dissolved oxygen in the solvent was
It was found that when the amount was less than ppm, the light resistance of the organic dye recording layer was improved.

[Effects of the Invention] As explained above, according to the optical recording medium and the manufacturing method thereof of the present invention, since the amount of oxygen contained in the recording layer formed using an organic dye is reduced, the amount of oxygen contained in the recording layer formed using an organic dye is reduced. It is possible to suppress photodeterioration of organic dyes involving molecules, and to obtain an excellent effect of obtaining an organic dye medium with excellent photostability.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view showing a typical example of the optical recording medium of the present invention, FIG. 2 is an explanatory view showing an example of a method for removing dissolved oxygen in a dye solvent, and FIG. 3 is an example 1 and a comparative example. 1 is a graph showing a comparison of decreases in reflectance of optical recording media of No. 1;

Claims (2)

[Claims] (1) An optical information recording medium having a recording layer formed using an organic dye, characterized in that the oxygen content contained in the recording layer is 10 ppm or less. (2) In a method for manufacturing a solvent-coated optical recording medium having a recording layer formed using an organic dye, the recording layer is formed using a dye coating solution containing an organic dye dissolved in a solvent and having an oxygen content of 10 ppm or less. A method for manufacturing an optical information recording medium, characterized in that: