JPH0373386A - Manufacture of optical recording medium - Google Patents

Abstract

PURPOSE:To enable write sensitivity of reflectance and C/N ratio of reading to be raised by a method wherein a recording layer which contains a specific light absorbing coloring matter and does not contain a resin constituent is applied onto a base material. CONSTITUTION:A recording layer which contains a light absorbing coloring matter given by a formula [I] and does not contain a resin constituent is applied onto a base material. In the formula [I] phi+ and psi represent respectively indolenine ring residue, benzoindolenine ring residue or dibenzoindolenine ring residue. However, it is never generated that both phi<+> and psi become 4,5- benzoindolenine ring residue. L represents a combination group for forming cyanine coloring matter and X<-> represents an anion. (m) is an integer of 0 or 1. Further, though this light recording medium is written and is read from a rear surface side of a base material, this recording layer coated film, in the case where recording light and reading light of a long wavelength of semiconductor laser or the like are used, is high in read sensitivity and high in reflectance. Therefore, a S/N ratio of read is high and further, raw shelf life is excellent.

Description

DETAILED DESCRIPTION OF THE INVENTION ■ BACKGROUND OF THE INVENTION Field The present invention relates to a method for manufacturing an optical recording medium, particularly a heat mode optical recording medium.

Prior Art Optical recording media have the characteristic that the recording medium does not deteriorate due to wear and tear because there is no contact between the medium and the writing or reading head, and for this reason, research and development of various optical recording media are being conducted.

Among such optical recording media, heat mode optical recording media are being actively developed because they do not require image processing in a darkroom.

This heat mode optical recording medium is an optical recording medium that uses recording light as heat. For example, a part of the medium is melted or removed using recording light such as a laser, and it is called a bit. Some write by forming small holes, recording information using these bits, and reading out by detecting these bits with read light.

As an example of such bit-forming media,
It is known that a recording layer is formed by coating or vapor depositing a light-absorbing dye on a substrate, and a bit is formed by heating and melting the dye.

The recording light and read light for writing on such a heat mode optical recording medium are 750 to 8
It is preferable to use long wavelength recording light such as a semiconductor laser or a light emitting diode with an oscillation wavelength of 30 nm.

By the way, cyanine dyes and dithiol complexes are examples of dyes that absorb long-wavelength light. However, among cyanine dyes, the typically used thiazole ring, benzothiazole ring, naphthothiazole ring,
Those having benzoselenazole rings, benzoxazole rings, etc. at both ends of the vinylene chain have low solubility in coating solvents, poor coating properties, low reflectance, and low readout S/N ratio. It also has low thermal stability.

On the other hand, pt or Ni dithiol complexes have low extinction coefficients and reflectances, low write sensitivity and read reflectance, and low read S/N ratios.

Therefore, when these ordinary cyanine dyes and dithiol complexes are used, a medium that can be used in practical use for semiconductor lasers cannot be realized.

■ Purpose of the Invention The main purpose of the present invention is to provide high reading sensitivity when using long wavelength recording light and reading light such as semiconductor lasers.
Provided is a method for manufacturing an optical recording medium having a recording layer coating film that has excellent properties such as high reflectance, high readout S/N ratio, and good shelf life, and excellent productivity. There is a particular thing.

Such objects are achieved by the invention described below.

(1) A method for producing an optical recording medium, which comprises coating a substrate with a recording layer containing a light-absorbing dye represented by the following formula [I] and containing no resin component.

Formula [I] φ0-L=ψ(X-1゜(In the above formula [Engine], φ3 and ψ represent an indolenine ring residue, a benzindolenine ring residue, or a dibenzoindolenine ring residue, respectively) However, both φ” and ψ are 4,5−
It never becomes a benzindolenine ring residue.

L represents a linking group for forming a cyanine dye.

X- represents an anion.

m is an integer of O or 1; ) Furthermore, the earlier application of this application, JP-A-58-194595
The publication proposes the use of the same indolenine cyanine dye as in the present invention in the recording layer.

However, this publication does not disclose the coating of an indolenine-based cyanine dye alone, and the recording layer is formed from a vapor-deposited film or a coating film using a resin component as a binder. In this case, there are disadvantages in that the vapor-deposited film is inferior in mass productivity, and when a binder is used, sensitivity etc. are reduced.

■Specific structure of the invention Hereinafter, the specific configuration of the present invention will be explained in detail.

In the recording layer of the optical recording medium manufactured according to the present invention,
A light-absorbing dye represented by the above formula [I] is included.

In the above formula [1, Φ and A are residues of the indolenine ring or benzindolenine ring, Φ has a ten charge on the N atom of the indolenine nucleus, and A has a neutral N atom. .

Each of them may be the same or different, and various substituents can be bonded to them.

Among these, Φ and A are preferably the same, and particularly preferably those represented by the following formulas [111 to [Vl].

However, φ and ψ are never both 4,5-indolenine ring residues of formula [IV].

In this case, in Denko attached to the 2nd position of the indolenine ring, hmm It means that.

Formula [Ir] Mountain Expression [rllll 1 Formula [rV] 3 Formula [Vl (R’).

In the above formulas [] to [Vl, R2 represents a substituted or unsubstituted alkyl group.

The alkyl group preferably has 1 to 5 carbon atoms, and preferable substituents include a sulfonic acid group and an alkylcarboxyoxy group. In addition, examples of the substituent include an alkylamido group, an alkyloxy group, a carboxylic acid group, and a hydroxyl group.

Note that R1 may be a substituted or unsubstituted aryl group.

In such a case, when m (described later) is O, R of Φ
8 has one charge.

Further, R2 and R1 each represent an alkyl group or an aryl group such as a phenyl group, preferably an alkyl group. In this case, the alkyl group is preferably unsubstituted and preferably has 1 or 2, especially 1, carbon atom.

Further, R4 represents a substituent, which may be an alkyl group, an aryl group, a heterocyclic residue, a halogen atom, an alkoxy group, an alkylthio group, an alkylhydroxycarbonyl group, a carboxylic acid group, or the like.

Further, p is usually an integer of 0 to 4, and when p is 2 or more, the plurality of R4s may be different from each other.

On the other hand, L represents a linking group for forming a cyanine dye such as carbocyanine, dicarbocyanine, tricarbocyanine, or tetracarbocyanine, but especially the following formula [
VT] to [Kari].

Formula [Vl] CH= CH-CH= C-cH=
CH-CH formula [X] CH= CH-CH= CH-C = CH-CH= CH-CH ■ Formula [XII] CH=C-CH Here, Y represents a hydrogen atom or a monovalent group. In this case, the monovalent group includes a lower alkyl group such as a methyl group, a lower alkoxy group such as a methoxy group, a dimethylamino group, a diphenylamino group, a methylphenylamino group, a morpholino group, an imidazolidine group, and an ethoxycarbonyl bibera group. Preferred examples include a di-substituted amino group such as a gin group, an alkylcarbonyloxy group such as an acetoxy group, an alkylthio group such as a methylthio group, a halogen atom such as Br%C°C, a cyano group, and a nitro group.

Furthermore, X- is an anion, and preferred examples thereof include I-Br-CQO4 BF4-1CHzO3O*-.

Note that m is O or 1, but when m 7 or S 2 O, R1 of Φ usually has a single charge and becomes an inner salt.

Next, one specific example of the light-absorbing dye of the present invention will be given.
The present invention is not limited to this.

Such dyes are described in Laser Research Paper (4) Comprehensive list of organic compounds for dye lasers, Dai Organic Chemistry (Breakfast Shoten) Nitrogen-Containing Heterocyclic Compound IP438, and can be synthesized by known methods. Particularly in the case of heptamethine, so-called Z
It can be easily synthesized by INCK (DTCKMANN) reaction.

In the present invention, the recording layer is coated with a coating film of such a dye. Therefore, it is excellent in mass production.

For coating the recording layer, for example, methyl ethyl ketone,
Using solvents such as ketones such as methyl isobutyl ketone and cyclohexanone, esters such as butyl acetate, ethyl acetate, carpitol acetate, butylcarpitol acetate, ethers such as methyl cellosolve and ethyl cellosolve, and alkyl halides such as dichloroethane. and apply it according to the usual method.

In addition, when coating the recording layer, a plasticizer, a surfactant, an antistatic agent, a lubricant, a flame retardant, a stabilizer, a dispersant, etc. may be included.

However, it does not contain a resin component as a binder component. Containing a resin component improves sensitivity, reflectance, and S/N.
It is disadvantageous in terms of comparison.

There is no particular restriction on the material of the substrate on which such a recording layer is applied, and it may be any of various resins, glass, ceramics, metals, etc., but it is preferably transparent to recording light and reproduction light. .

In addition, the shape varies depending on the purpose of use, such as tape, disk,
It may be a drum, a belt, etc.

Note that the base body may have a base layer, a heat storage layer, etc., as necessary.

Further, on the recording layer, a reflective layer that functions as a back surface for writing and reading when a transparent substrate is used, various uppermost protective layers, a half mirror layer, etc. can be provided as necessary.

However, since the dye used in the present invention itself has extremely high reflectance through the substrate, there is usually no need to use such an underlayer or upper reflective layer.

The medium in the present invention may have the above-described recording layer on one surface of such a substrate, or may have recording layers on both surfaces thereof. Alternatively, two substrates each having a recording layer coated on one surface are used, and the recording layers are placed opposite to each other with a predetermined distance between them.
You can also seal it to prevent dust and scratches.

(2) Specific Effects of the Invention The medium manufactured according to the present invention is irradiated with pulsed recording light from the back side of the substrate while running or rotating.

At this time, the dye in the recording layer is heated and melted, forming bits.

In this case, when a semiconductor laser diode for recording with a wavelength of 750 to 850 nm is used, extremely good writing can be performed.

The bits thus formed are read out by detecting the reflected or transmitted light of the readout light of the above-mentioned wavelength, especially the reflected light through the substrate, while the medium is running or rotating.

Further, a He-Ne laser or the like can also be used as the recording and reading light.

■Specific Effects of the Invention The medium produced by the present invention is 7501780, 8
Extremely sensitive writing can be performed using semiconductor laser light emitting diodes with wavelengths such as 30 nm.

In addition, it is possible to form bits with extremely good shapes, and the coating properties are good, and the reflectance through the substrate is extremely high compared to other cyanine dyes and Ni%pt dithiol complexes. Therefore, the readout S/N ratio and C
/N ratio is also extremely high.

Furthermore, it has high safety against heat, etc., good shelf life, and little deterioration in writing characteristics.

Furthermore, since the recording layer is formed as a coating film, productivity is excellent. However, since a resin component as a binder is not required in the coating film of the recording layer, sensitivity, reflectance, S/N ratio, etc. are high.

(2) Specific Examples of the Invention Hereinafter, specific examples of the present invention will be shown and the present invention will be explained in more detail.

Example 1 After dissolving 11 parts by weight of the above dye No. D in 200 parts by weight of cyclohexanone-dichloroethane (1:1), 0.0 parts by weight of the above dye No. D was dissolved on an acrylic resin disk substrate with a diameter of 15 cm.
A medium of the present invention was obtained by coating the medium to a thickness of 04.11J1.

Further, the medium of the present invention was obtained in the same manner as above using colored threads No. D2 and D5 instead of colored thread No. D1.

B Separately, for comparison, comparative media were obtained in the same manner as above using the following dyes A to D.

CβO4- Further, for comparison, a recording layer coating film of dye No., DI and nitrocellulose in a ratio of 1=1 (weight ratio) was formed according to the description in JP-A-58-194595.

For the media created in this way, it costs 1800 r.
Al at the wavelengths shown in Table 1 below while rotating at pm.
A 2GaAs-GaAs semiconductor laser recording beam was condensed to 1-φ and irradiated in a pulse train through the substrate at a predetermined frequency (concentrator output 10 mV).

Each medium was irradiated with writing light from the substrate side while changing the pulse width, and the pulse width at which an extinction ratio of 2.5 was obtained was measured, and the reciprocal of the pulse width was taken as the writing sensitivity. The results are shown in Table 1.

In this case, the extinction ratio is the degree of attenuation in the bit portion of the reflectance of readout light, which will be described later.

The results are shown in Table 1.

Note that in Table 1, the reflectance through the substrate is listed.

From the results shown in Table 1, it can be seen that the medium of the present invention has extremely high reflectance writing sensitivity and reading C/N ratio.

In addition, for each medium, after writing, it was heated at 60°C in the dark.
C/N stored for 500 hours under conditions of 90% relative humidity
When the ratio was measured, the medium of the present invention showed significantly higher storage stability than the comparative medium.

Claims (2)

[Claims] (1) A method for producing an optical recording medium, which comprises coating a substrate with a recording layer containing a light-absorbing dye represented by the following formula [I] and containing no resin component. Formula [I] φ^+-L=ψ(X^-)_m {In the above formula [I], φ^+ and ψ are indolenine ring residue, benzoindolenine ring residue, or dibenzoindolenine, respectively Represents a ring residue. However, both φ^+ and ψ are 4 and 5
- It does not become a benzindolenine ring residue. L represents a linking group for forming a cyanine dye. X^- represents an anion. m is an integer of 0 or 1. } (2) The method for manufacturing an optical recording medium according to claim 1, wherein writing and reading are performed on the optical recording medium from the back side of the substrate.