JPH0613237B2 - Method of manufacturing optical recording medium - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Technical Field The present invention relates to a method for manufacturing an optical recording medium, particularly a heat mode optical recording medium.

The prior art optical recording medium has a feature that the recording medium does not wear and deteriorate because the writing and reading heads are not in contact with the medium, and therefore various optical recording media have been researched and developed.

Among such optical recording media, the heat mode optical recording media has been actively developed because it does not require image processing in a dark room.

This heat mode optical recording medium is an optical recording medium that uses recording light as heat, and as one example thereof, a part of the medium is melted and removed by recording light such as a laser and is called a pit. There is a method in which a small hole is formed for writing, information is recorded by the pit, and the pit is detected by a reading light to perform reading.

And, as an example of such a pit formation type medium,
It is known that a light absorbing dye is applied or vapor-deposited on a substrate to form a recording layer, and the dye is heated and melted to form pits.

The recording light and the reading light for writing on such a heat mode optical recording medium are 750 to 8 in order to make the writing and reading device small.
It is preferable to use long-wavelength recording light such as a semiconductor laser or a light emitting diode having an oscillation wavelength of 30 nm.

By the way, cyanine dyes and dithiol complexes are one of the dyes that absorb long-wavelength light.

However, among cyanine dyes, thiazole ring, benzothiazole ring, naphthothiazole ring, which are typically used,
Those having a benzoselenazole ring, a benzoxazole ring, or the like at both ends of a vinylene chain have low solubility in a coating solvent, poor coatability, low reflectance, and small read S / N ratio. Also, the thermal stability is low.

On the other hand, in the case of Pt or Ni dithiol complex, the extinction coefficient and reflectance are low, the writing sensitivity and the reflectance for reading are low, and the S / N ratio for reading is small.

For this reason, when these ordinary cyanine dyes and dithiol complexes are used, a medium for semiconductor lasers that cannot be practically used cannot be realized.

II Object of the invention The main object of the present invention is to provide a high reading sensitivity when using recording light having a long wavelength such as a semiconductor laser or reading light.
Manufacture of an optical recording medium having a recording layer coating film having excellent characteristics such as high S / N ratio or C / N for reading because of high reflectance and good raw storage stability and excellent productivity. To provide a method.

Such an object is achieved by the present invention described below.

(1) A method for producing an optical recording medium, which comprises coating a recording layer containing a light absorbing dye represented by the following formula [I] and not containing a resin component on a substrate.

Formula [I] φ ⁺ −L = ψ (X ⁻ ) _m {In the above formula [I], φ ⁺ and ψ are an indolenine ring residue, a benzoindolenine ring residue or a dibenzoindolenine ring residue, respectively. Represents However, neither φ ⁺ nor ψ becomes a 4,5-benzoindolenin ring residue.

L represents a linking group for forming a cyanine dye.
X ⁻ represents an anion.

m is an integer of 0 or 1. } Note that Japanese Patent Application Laid-Open No. 58-194595, which is a prior application of this application,
In the publication of the issue, it is proposed that the same indolenine cyanine dye as in the present invention is used in the recording layer.

However, the publication does not disclose that an indolenine-based cyanine dye is separately applied to form a coating layer, and the recording layer is formed of a vapor deposition film or a coating film using a resin component as a binder. In this case, the vapor deposition film is inferior in mass productivity, and the sensitivity and the like are deteriorated when a binder is used.

III Specific Structure of the Invention Hereinafter, the specific structure of the present invention will be described in detail.

In the recording layer of the optical recording medium produced by the present invention,
The light absorbing dye represented by the above formula [I] is included.

In the above formula [I], Φ and Ψ which are residues of the indolenine ring or the benzoindolenine ring are those in which Φ has a + charge on the N atom of the indolenine nucleus and Ψ has a neutral N atom. is there.

And each may be the same or different and various substituents can be bonded.

Of these, Φ and Ψ are preferably the same, and particularly preferably those represented by the following formulas [II] to [V].

However, neither φ nor ψ becomes a 4,5-indolenine ring residue of the formula [IV].

In this case, the charge symbol (•) attached to the 2-position of the indolenine ring is At Ψ It means that

Formula [II] Formula [III] Formula [IV] Formula [V] In the above formulas [II] to [V], R ₁ 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, as the substituent, an alkylamido group, an alkyloxy group, a carboxylic acid group, a hydroxyl group or the like can be used.

In addition, R ₁ may be a substituted or unsubstituted aryl group.

In such a case, when m described later is 0, R of Φ
₁ has a-charge.

R ₂ and R ₃ 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 unsubstituted and preferably has 1 or 2 carbon atoms, especially 1 carbon atom.

Further, although R ₄ represents a substituent, it can 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.

And, p is usually an integer of 0 to 4, and when p is 2 or more, a plurality of R _{4 s} 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, and is particularly one of the following formulas [VI] to [XII]. preferable.

Formula [VI] Formula [VII] Formula [VIII] Formula [IX] Expression [X] Formula [XI] Formula [XII] Here, Y represents a hydrogen atom or a monovalent group. In this case, the monovalent group is a lower alkyl group such as a methyl group,
Lower alkoxy group such as methoxy group, dimethylamino group,
Di-substituted amino groups such as diphenylamino group, methylphenylamino group, morpholino group, imidazolidine group, ethoxycarbonylpiperazine group, alkylcarbonyloxy groups such as acetoxy group, alkylthio groups such as methylthio group, halogen atoms such as Br and Cl It is preferably a cyano group, a nitro group or the like.

Further, X ⁻ is an anion, and preferable examples thereof include I ⁻ , Br ⁻ , ClO ₄ ⁻ , BF ₄ ⁻ , Etc. can be mentioned.

In addition, m is 0 or 1, but when m is 0, R _{1 of} Φ usually has a − charge to form an inner salt.

Next, one example of the specific examples 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 8 (4) Dye Laser Organic Compounds List, Dai Organic Chemistry (Asakura Shoten), nitrogen-containing heterocyclic compound IP438 and the like, and can be synthesized by a known method. Especially in the case of heptamethine system, so-called ZINC utilizing cleavage of pyridine derivative is used.
It can be easily synthesized by the K (DICKMANN) reaction.

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

To apply the recording layer, for example, methyl ethyl ketone,
Uses ketone-based solvents such as methyl isobutyl ketone and cyclohexanone, ester-based solvents such as butyl acetate, ethyl acetate, carbitol acetate and butyl carbitol acetate, ether-based solvents such as methyl cellosolve and ethyl cellosolve, and alkyl halides such as dichloroethane. And apply it according to the usual method.

When the recording layer is applied, a plasticizer, a surfactant, an antistatic agent, a lubricant, a flame retardant, a stabilizer, a dispersant, etc. may be added.

However, it does not contain a resin component as a binder component. When resin component is included, sensitivity, reflectance, S / N
It is disadvantageous in terms of ratio.

The material of the substrate on which such a recording layer is coated is not particularly limited and may be any of various resins, glass, ceramics, metals and the like, but those transparent to recording light and reproducing light are preferable.

The shape of the tape, disk,
It may be a drum, a belt or the like.

The substrate may have a base layer, a heat storage layer, etc., if necessary.

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

However, since the dye of the present invention itself has a very high reflectance through the substrate, it is usually unnecessary to use such a base or upper reflective layer.

The medium in the present invention may have the above-mentioned recording layer on one surface of such a substrate, or may have the recording layer on both surfaces thereof. In addition, by using two recording layers coated on one surface of the substrate, the recording layers are made to face each other and are opposed to each other at a predetermined interval, and they are hermetically sealed to prevent dust and scratches. You can also do so.

IV Specific Actions of the Invention The medium manufactured according to the present invention irradiates recording light on pulses from the back surface side of the substrate while running or rotating.
At this time, the dye in the recording layer is heated and melted to form pits.

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

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

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

V. Specific Effects of the Invention The media produced according to the present invention are 750, 780, 8
Writing can be performed with extremely high sensitivity by using a semiconductor laser or a light emitting diode having a wavelength of 30 nm or the like.

In addition, pits having an extremely good shape can be formed, the coating properties are good, and the reflectance through the substrate is extremely high as compared with other cyanine dyes, Ni, and Pt dithiol complexes. , Read S / N ratio and C /
The N ratio is also extremely high.

Further, it is highly safe against heat and the like, has a good raw storability, and has little deterioration in writing characteristics.

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

VI Specific Examples of the Invention Hereinafter, specific examples of the present invention will be shown to explain the present invention in more detail.

Example 1. After dissolving 1 part by weight of the above dye No. D1 in 200 parts by weight of cyclohexanone-dichloroethane (1: 1),
0.04 on an acrylic resin disk substrate with a diameter of 15 cm
A medium of the present invention was obtained by applying a layer having a thickness of μm.

Also, instead of color system No. D1, use color system No. D2, D5,
The medium of the present invention was obtained in the same manner as above.

Separately from this, for comparison, the following dyes A to D were used in the same manner as above to obtain a medium for comparison.

A B C D For comparison, a 1: 1 (weight ratio) recording layer coating of dye No. D1 and nitrocellulose was provided according to the description in JP-A-58-194595.

This is 1800rp for the media created in this way.
While rotating at m, the AlG of the wavelength shown in Table 1 below
The aAs-GaAs semiconductor laser recording light was condensed to 1 μmφ (condenser output 10 mV) and irradiated in a pulse train at a predetermined frequency through the substrate.

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

In this case, the extinction ratio is the degree of attenuation of the reflectance of read light, which will be described later, at the pit portion.

The results are shown in Table 1.

In addition, in Table 1, C / N and reflectance through the substrate are also shown.

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

For each medium, after writing, in the dark at 60 ° C,
C / N stored for 500 hours under 90% relative humidity
When the ratio was measured, the medium of the present invention showed remarkably high storability as compared with the medium for comparison.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Akihiko Kuroiwa 1-13-1 Nihonbashi, Chuo-ku, Tokyo TDC Corporation (72) Inventor Shiro Nakagawa 1-13-1 Nihonbashi, Chuo-ku, Tokyo TDC (56) References JP 58-194595 (JP, A) JP 58-218055 (JP, A) JP 55-89359 (JP, A) JP 57-74845 (JP, A) Japanese Patent Publication Sho 49-13570 (JP, B1) US Patent 3916069 (US, A)

Claims (2)

[Claims] 1. A method for producing an optical recording medium, which comprises applying a recording layer containing a light absorbing dye represented by the following formula [I] and containing no resin component on a substrate. Formula [I] φ ⁺ −L = ψ (X ⁻ ) _m {In the above formula [I], φ ⁺ and ψ are an indolenine ring residue, a benzoindolenine ring residue or a dibenzoindolenine ring residue, respectively. Represents However, neither φ ⁺ nor ψ becomes a 4,5-benzoindolenin 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 optical recording medium according to claim 1, wherein writing and reading are performed from the back side of the substrate.
Item 2. A method for manufacturing an optical recording medium according to item.