JP3168469B2 - 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 organic dye-based optical recording medium using a laser-absorbing dye, and more particularly, to an organic dye-based optical recording medium excellent in solubility of a laser-absorbing dye and storage stability of a coating film. About.

[0002]

2. Description of the Related Art An example of an optical recording medium is an optical disk. In particular, it is small and highly reliable,
With the advent of inexpensive semiconductor lasers, read-only optical disks such as compact disks (CDs) and the like, and additional optical disks using Te-based inorganic materials as recording media have been put to practical use.

On the other hand, studies have been made on an organic dye-based optical disk using a laser absorbing dye as a new write-once medium. The greatest feature of this organic dye-based optical disk is that it can be formed by a coating method such as a spin coating method, and high productivity under normal pressure is expected to reduce the cost in the future. Generally, an optical disc performs high-density information recording by irradiating a thin recording layer provided on a circular substrate with a laser beam focused to about 1 μm. In the recording layer, recording is performed by thermal deformation such as decomposition, evaporation, and dissolution of the recording layer generated at that location due to absorption of the irradiated laser energy,
Reproduction of recorded information is performed by reading the difference in reflectance between a portion where deformation has occurred and a portion where no deformation has occurred using a laser beam.

[0004] Guide grooves are formed in advance on the recording surface of the optical disc in order to perform accurate recording and reproduction. Usually, the guide groove is formed by a fetopolymer method or an injection molding method. However, in the former case, there is a disadvantage that productivity is poor and expensive due to molding from a photopolymer. In the latter case, the injection molding method provides excellent productivity and inexpensive disks can be produced.However, resins that can be used in the injection molding method are required to have fluidity at the time of heating, so there are restrictions on materials, and in general the resin is resistant. Poor solvent properties.

When forming a thin film of a laser-absorbing dye on such a transparent plastic substrate by solution coating, it is necessary that the guide groove on the substrate is not affected by the coating solvent. ,
Alcohol solvents are known. However, almost no laser-absorbing dye was dissolved in an alcohol-based solvent at a high concentration, and the laser-absorbing dye was supported at a high concentration on an injection-molded plastic substrate, and a stable coating film could not be formed.

[0006]

Therefore, the present inventors can apply evenly without invading the injection-molded plastic transparent substrate, dissolve and carry the laser-absorbing dye at a high concentration, and preserve the applied film. As a result of intensive studies on methods for improving the stability, the use of a mixture of three or more laser-absorbing dyes having the same chromogen and slightly different substituents improves the solubility and prevents crystallization of the coating film. (Improvement of amorphousness) was found, and the present invention was reached.

[0007]

SUMMARY OF THE INVENTION The present invention relates to an optical recording medium obtained by applying an organic solvent solution of a laser-absorbing dye on a transparent substrate and then drying the same. The gist of the present invention is an optical recording medium characterized in that at least three or more types are used.

Hereinafter, the present invention will be described in detail. Examples of the transparent substrate used in the present invention include substrates made of glass, plastic, and the like, and a plastic substrate is preferable from various points. Acrylic resin as plastic substrate,
Substrates such as methacrylic resin, vinyl acetate resin, vinyl chloride resin, nitrocellulose, polyethylene resin, polypropylene resin, polycarbonate resin, polyimide resin, and polysulfone resin.

Particularly preferred substrates include injection-molded polycarbonate resin substrates and methacrylic resin substrates which are excellent in mass productivity and have practical levels of birefringence, softening point and heat resistance. Examples of the laser absorbing dye include dye precursors such as a cyanine dye, a metal chelate compound, an azo dye, a triarylmethane dye, a phthalocyanine dye, a squarylium dye, an anthraquinone dye, and a naphthoquinone dye. As these laser-absorbing dyes, those having the same dye skeleton and having different types, positions or numbers of substituents are preferably used. In particular, as a substituent, a linear or branched alkyl group such as a methyl group, an ethyl group, a propyl group, a butyl group, a hexyl group, an octyl group, or a methoxyethyl group, an ethoxyethyl group, a propoxyethyl group, a butoxyethyl group And the like.

[0010] From the practicality of these laser absorbing dyes, the difference between the maximum absorption wavelengths is preferably within 50 nm, more preferably within 30 nm. Particularly preferred dyes as the laser absorbing dye include laser absorbing dyes represented by the following general formula [I] or general formula [II].

[0011]

Embedded image Wherein A ¹ represents a residue which forms a heterocyclic ring together with the carbon atom to which it is bonded and a nitrogen atom, and B ¹ is a group which is bonded to the two carbon atoms to which it is bonded. And X represents a group having active hydrogen.) And a chelate compound of a metal and an azo compound represented by the formula:

[0012]

Embedded image (Wherein, rings A ² and B ² each independently represent a benzene ring or a naphthalene ring which may have a substituent, and R ¹ and R ² each independently represent a substituent. Represents an alkyl group having 1 to 8 carbon atoms, X ⁻ represents an anion, m is 2 or 3, and n is an integer of 0 to 4).

In the metal chelate compound represented by the above general formula [I], the residue forming the heterocyclic ring represented by A ¹ is, for example, the following general formula:

[0014]

Embedded image (Wherein, R ³ and R ⁴ each independently represent a hydrogen atom, a halogen atom, an alkyl group, an acylamino group, a dicyanovinyl group, an alkoxy group, a nitro group or an alkoxyalkyl group). . The residue forming an aromatic ring or a heterocyclic ring represented by B ^1, for example, the following formula

[0015]

Embedded image (Wherein, R ⁵ is a hydrogen atom, a halogen atom, an alkyl group,
Represents an acylamino group or an alkoxy group, R ⁶ and R ⁷
Each independently represents a hydrogen atom or an alkyl group having 1 to 20 carbon atoms, each of which independently has a substituent selected from an alkoxy group, an alkoxyalkoxy group, an alkoxyalkoxyalkoxy group, and a hydroxy group. Is also good. ). Examples of the group having an active hydrogen represented by X include a hydroxyl group, a carboxylic acid group, and a sulfonic acid group. Examples of the metal forming a complex compound with an azo compound include Group VIII, Ib, and IIb.
Group, group IIIa, group IVa, group Va, group VIa, group VIIa, preferably Ni, Cu, Co metal atoms.

In the cyanine dye represented by the general formula [II], examples of the substituent of the benzene ring or naphthalene ring represented by rings A ² and B ² include a halogen atom such as a fluorine atom, a chlorine atom and a bromine atom. Alkyl groups such as methyl group, ethyl group, propyl group and butyl group; halogenated alkyl groups such as trifluoromethyl group; alkoxy groups such as methoxy group, ethoxy group and propoxy group; alkoxyalkoxy groups such as methoxyethoxy group; An alkoxyalkyl group such as an ethoxyethyl group is exemplified.

Examples of the optionally substituted alkyl group having 1 to 8 carbon atoms represented by R ¹ and R ² include a methyl group, an ethyl group, a linear or branched propyl group, a butyl group, Examples include a pentyl group, a hexyl group, a heptyl group, and an octyl group, and these may be substituted with a halogen atom, an alkoxy group, or the like. X ^- include anions represented by the

[0018]

Embedded image The laser absorbing dye represented by the above general formula [I] or general formula [II] is preferably an alcohol-based solvent. Of these laser absorbing dyes, three or more kinds of substituted derivatives of the same chromogen having a maximum difference in the maximum absorption wavelength of 50 nm or less are used in combination and spin-coated as they are or dissolved in an alcohol solvent together with a binder. By doing so, an optical recording medium is manufactured.

Any binder can be used as long as it is soluble in an alcohol solvent. The ratio of the laser absorbing dye to the alcohol solvent is 0.5
-3.0% by weight is particularly preferred. The ratio of the laser dye to the binder is desirably 10% by weight or more.
Preferred alcohol solvents include ketone alcohol solvents such as diacetone alcohol and 3-hydroxy-3-methyl-2-butanone; cellsolve solvents such as methylcellsolve and ethylcellsolve; tetrafluoropropanol and octafluoropentanol Perfluoroalkyl alcohol solvents; hydroxyester solvents such as methyl lactate and methyl isobutyrate.

The solution in which the dye is dissolved is preferably filtered through a filter having a size of 0.3 μm or less. The rotation speed of the spin coating is preferably from 500 to 2000 rpm. After the spin coating, if necessary, a treatment such as heating or exposure to a solvent vapor may be performed. The thickness of the coating film is
300-1500 ° is preferred.

Further, a transition metal chelate compound (acetylacetonate chelate, bisphenyldithiol, salicylaldehyde oxime, bisdithio-α-diketone, etc.) is contained as a singlet oxygen quencher for improving the stability and light resistance of the recording medium. May be. The recording film of the optical recording medium of the present invention may be provided on both sides of the substrate, or may be provided only on one side.

The recording on the recording medium obtained as described above is performed on the recording layer provided on both sides or one side of the substrate by 1 μm.
It is performed by applying a laser beam, preferably a semiconductor laser, which is focused to a certain degree. The part irradiated with the laser beam is decomposed by absorption of laser energy,
Thermal deformation of the recording layer such as evaporation and melting occurs. Reproduction of recorded information is performed by reading the difference in reflectance between a portion where thermal deformation has occurred and a portion where thermal deformation has not occurred using a laser beam.

As the light source, various lasers can be used, but a semiconductor laser is particularly preferable in terms of cost and size. As a semiconductor laser, the center wavelength 83
A laser having a wavelength of 0 nm and a center wavelength of 780 nm is desirable.

[0024]

The present invention will be described below in more detail with reference to examples, but the examples do not limit the present invention. Example 1 90 mg of compound 1 and 40 mg of compound 2 shown in Table 3
And 70 mg of compound 3 in 10 g of 3-hydroxy-3-methyl-2-butanone (HMB) to give 0.22
The solution was obtained by filtration through a μm filter. At this time, there was no filtration residue on the filter.

5 ml of this solution was added to a 1.2 mm thick plate of 1.
After dripping onto an injection-molded polycarbonate resin substrate (5 inches in diameter) having a groove (groove) of 6 μm pitch, and applying the solution at a rotation speed of 1000 rpm by a spinner method, 60 ° C.
For 10 minutes. The maximum absorption wavelength of the coating film is 720n
m. Storage stability test of coating film (70 ° C, 85
%: 200 hours). As a result, no crystallization or the like of the coating film was observed, which was favorable.

A reflective layer was formed by depositing gold on the coating film, and a hard coat treatment was further performed on the reflective layer with an ultraviolet curable resin to prepare a sample. The prepared sample had a center wavelength of 78.
The EFM signal was recorded with a semiconductor laser beam of 0 nm, and the optimum recording sensitivity and the modulation degree (I ₁₁ / I _top ) were obtained. .

Further, a light fastness test (xenon fade meter-acceleration test: 60 hours) and a storage stability test (7
(0 ° C., 85% RH: 500 hours). As a result, the sensitivity and the reproduction signal were not deteriorated as compared with the initial stage, and the optical recording medium was extremely excellent. Example 2 50 mg of compound 4 and 70 mg of compound 5 shown in Table 4
And 80 mg of compound 6 and 10 g of HMB,
The solution was obtained by filtration with a 0.22 μm filter. At this time, there was no filtration residue on the filter.

5 ml of this solution was added to a 1.2 mm thick plate of 1.
The solution was dropped on a 6 μm pitch grooved injection molded polycarbonate resin substrate (5 inches in diameter), applied at a rotation speed of 800 rpm by a spinner method, and then dried at 60 ° C. for 10 minutes. The maximum absorption wavelength of the coating film was 730 nm, and the storage stability was good. A reflective layer was formed by depositing gold on the coating film, and a hard coat treatment was further performed on the reflective layer with an ultraviolet curable resin to prepare a sample.

When the recording characteristics of the sample obtained in the same manner as in Example 1 were evaluated, a good initial recording characteristic with a recording sensitivity of 8.5 W and a modulation factor of 70% was obtained. In the same manner, light resistance and storage stability tests were carried out. As a result, no deterioration in sensitivity and reproduction signal was observed compared to the initial stage, and the optical recording medium was extremely excellent. Example 3 30 mg of compound 24 and 30 mg of compound 25 shown in Table 5
mg, compound 26 30 mg, compound 27 20 mg,
A sample was prepared in the same manner as in Example 2 except that 30 mg of compound 28, 30 mg of compound 29, and 30 mg of compound 30 were dissolved in 10 g of HMB. The maximum absorption wavelength of the coating film was 730 nm, and the storage stability was good.

When the recording characteristics of the sample obtained in the same manner as in Example 1 were evaluated, a good initial recording characteristic with a recording sensitivity of 8.5 W and a modulation factor of 70% was obtained. In the same manner, light resistance and storage stability tests were carried out. As a result, no deterioration in sensitivity and reproduction signal was observed compared to the initial stage, and the optical recording medium was extremely excellent. Comparative Example 1 After mixing Compound 1 with 200 mg and HMB 10 g,
A solution was obtained by filtration through a 0.22 μm filter.
At this time, there was a filtration residue on the filter.

A coating film was formed in the same manner as in Example 1.
The maximum absorption wavelength of the coating film was 721 nm. A storage stability test of the coating film was performed in the same manner as in Example 1. As a result, crystallization was observed in part of the coating film, and the storage stability was poor. Comparative Example 2 After mixing Compound 5 with 200 mg and HMB 10 g,
A solution was obtained by filtration through a 0.22 μm filter.
At this time, there was a filtration residue on the filter.

A coating film was formed in the same manner as in Example 1.
The maximum absorption wavelength of the coating film was 731 nm. A storage stability test of the coating film was performed in the same manner as in Example 1. As a result, crystallization was observed in a part of the coating film, and the storage stability was poor. Comparative Example 3 200 mg of Compound 25 and 10 g of diacetone alcohol
, And then filtered through a 0.22 μm filter to obtain a solution. At this time, there was a filtration residue on the filter.

A coating film was formed in the same manner as in Example 1.
The maximum absorption wavelength of the coating film was 731 nm. A storage stability test of the coating film was performed in the same manner as in Example 1. As a result, crystallization was observed in part of the coating film, and the storage stability was poor. Comparative Example 4 70 mg of compound 1, 70 mg of compound 3 and 60 mg of compound 31 having different chromogens were mixed with 10 g of HMB, and the mixture was filtered through a 0.22 μm filter to obtain a solution. There was a filtration residue on top.

A coating film was formed in the same manner as in Example 1.
The maximum absorption wavelength of the coating film was 721 nm. A storage stability test of the coating film was performed in the same manner as in Example 1. As a result, crystallization was observed in part of the coating film, and the storage stability was poor. Table 1 summarizes the results of Examples 1 to 3 and Comparative Examples 1 to 4.

[0035]

[Table 1]

Examples 4 to 11 According to Examples 1 and 2, three or more compounds having the same chromogen were selected from the compounds shown in Tables 4 to 6, and dissolved in an alcohol-based solvent for coating. A film was formed. Table 2 shows the results of the maximum absorption wavelength and the storage stability test of each of the obtained coating films.

As in Examples 1 and 2, each was dissolved in an alcohol-based solvent at a high concentration and had no filtration residue, and could be uniformly applied without attacking the injection-molded polycarbonate resin substrate (whitening, groove dripping, etc.). In addition, the obtained coating film had excellent storage stability, high reflectance, high density and good sensitivity.

[0038]

[Table 2]

[0039]

[Table 3]

[0040]

[Table 4]

[0041]

[Table 5]

[0042]

[Table 6]

[0043]

According to the present invention, it is possible to apply uniformly without invading (whitening, groove dripping, etc.) the transparent substrate of the injection-molded plastic, without crystallization at the time of application, and to obtain a coating film (recording layer). ) Is excellent in storage stability, high in reflectivity, and can provide a high-sensitivity optical recording medium, which is industrially extremely useful.

Continuation of the front page (72) Inventor Takako Tsukahara 1000 Kamoshita-cho, Midori-ku, Yokohama-shi, Kanagawa Prefecture Inside Mitsubishi Chemical Research Institute (56) References JP-A-1-210388 (JP, A) JP-A-1-198391 (JP, A) JP-A-64-42282 (JP, A) JP-A-62-233887 (JP, A) JP-A-2-204089 (JP, A) JP-A-4-112083 (JP, A) JP-A-60-205841 (JP, A) JP-A-4-226788 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B41M 5/26 G11B 7/24

Claims (4)

(57) [Claims] A recording layer, a reflection layer and a hard disk on a transparent substrate;
In the optical recording medium obtained by applying a solution obtained by dissolving a laser absorbing dye in an organic solvent on a transparent substrate and then drying the optical recording medium, the recording layer is replaced with the same chromogen as the laser absorbing dye. An optical recording medium comprising at least three kinds of derivatives. 2. The optical recording medium according to claim 1, wherein the difference between the maximum absorption wavelengths of the laser absorbing dyes is within 50 nm. 3. The laser-absorbing dyes have the same dye skeleton and have different types of substituents, different substituent positions, and different numbers of substituents. 3. The optical recording medium according to 2. 4. The method according to claim 3, wherein the laser absorbing dye is selected from a chelate compound of an azo compound represented by the following general formula [I] and a metal or a cyanine compound represented by the general formula [II]. Optical recording medium. Embedded image Wherein A ¹ represents a residue which forms a heterocyclic ring together with the carbon atom to which it is bonded and a nitrogen atom, and B ¹ is a group which is bonded to the two carbon atoms to which it is bonded. Represents an aromatic ring or a heterocyclic ring, and X represents a group having active hydrogen.) (Wherein, rings A ² and B ² each independently represent a benzene ring or a naphthalene ring which may have a substituent, and R ¹ and R ² each independently have a substituent Represents an optionally substituted alkyl group having 1 to 8 carbon atoms, X ⁻ represents an anion, m is 2 or 3, and n is an integer of 0 to 4.)