JP2523448B2 - Optical recording medium and optical recording method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical recording medium, particularly a heat mode optical recording medium and an optical recording method.

[0002]

2. Description of the Related Art An optical recording medium has a characteristic that the recording medium does not wear and deteriorate because the writing and reading heads are not in contact with the medium. Therefore, various optical recording media have been researched and developed. .

Among such optical recording media, development of a heat mode optical recording medium has been active in that development processing in a dark room is unnecessary.

This heat mode optical recording medium is an optical recording medium that uses recording light as heat. As an example, a recording light such as a laser melts and removes a part of the medium to form pits. Write a small hole called
There is a pit formation type in which information is recorded by the pits, and the pits are detected by the reading light to perform reading.

Most of the pit-forming media, especially those having a semiconductor laser as a light source, which can miniaturize the device, have a recording layer mainly made of Te. .

However, in recent years, Te-based materials are harmful, need to be more sensitive, and manufacturing cost must be reduced. Therefore, instead of Te-based materials, dyes have been mainly used. Proposals and reports on media using organic material-based recording layers are increasing.

For example, for a He-Ne laser,
Squarylium dye [JP-A-56-46221 VB Jipson a
nd CRJones, J.Vac.Sci.Technol., 18 (1) 105 (1981))
And metal phthalocyanine dyes (JP-A-57-82094, 57
-82095) and some use.

There is also an example (JP-A-56-86795) in which a metal phthalocyanine dye is used for a semiconductor laser.

Each of these is a recording layer thin film formed by vapor deposition of a dye, and is not much different from the Te system in terms of manufacturing a medium.

However, the reflectance of the dye vapor deposition film with respect to the laser is generally small, and a read signal can be obtained by a change (decrease) in the amount of reflected light due to pits, and a large S / N ratio can be obtained in the ordinary system currently used. I can't.

When a transparent substrate carrying a recording layer is integrated so that the recording layers face each other, that is, a medium having a so-called air sandwich structure, and writing and reading are performed through the substrate, the writing sensitivity is not lowered. Further, it is advantageous in that the recording layer can be protected and the recording density is increased, but such a recording / reproducing system is not possible with the dye vapor deposition film.

This is because the ordinary transparent resin substrate has a certain degree of refractive index (1.5 for polymethylmethacrylate) and a large surface reflectance (see 4).
%), Since the reflectance of the recording layer through the substrate is, for example, about 60% or less for polymethylmethacrylate,
This is because it cannot be detected in the recording layer showing only a low reflectance.

In order to improve the read S / N ratio of the recording layer composed of the dye vapor deposition film, a vapor deposition reflective film such as Al is usually interposed between the substrate and the recording layer.

In this case, the vapor-deposited reflection film is for increasing the reflectance to improve the S / N ratio, and the reflection film is exposed by the formation of pits to increase the reflectance, or in some cases, Although the reflective film is removed to reduce the reflectance, it goes without saying that recording / reproduction cannot be performed through the substrate.

Similarly, in JP-A-55-161690, IR-1
A recording layer comprising 32 dyes (manufactured by Kodak Co.) and polyvinyl acetate, and 1,1′-diethyl-containing dye in JP-A-57-74845.
Recording layer composed of 2,2'-tricarbocyanine iodide and nitrocellulose, and further KYLaw, et al., Ap
pl. Phys. Lett. 39 (9) 718 (1981), a recording layer composed of a dye and a resin, such as a recording layer composed of 3,3'-diethyl-12-acetylthiatetracarbocyanine and polyvinyl acetate. There is disclosed a medium in which is coated by a coating method.

However, in these cases as well, a reflective film is required between the substrate and the recording layer, and recording and reproduction cannot be performed from the back surface side of the substrate, which has the same drawbacks as in the case of the dye vapor deposition film.

As described above, in order to realize a medium having a recording layer of an organic material, which is capable of recording / reproducing through a substrate and is compatible with a medium having a recording layer of a Te-based material. However, the organic material itself needs to exhibit a large reflectance.

However, heretofore, very few examples have shown a high reflectance with a single layer of an organic material without laminating a reflection layer.

Slightly, it was reported that the vapor-deposited film of vanadyl phthalocyanine exhibits high reflectance [P.Kivits, et al., Appl.
Phys. Part A 26 (2) 101 (1981), JP-A-55-97033], the writing sensitivity is low, probably because the sublimation temperature is high.

Further, thiazole-based and quinoline-based cyanine dyes and merocyanine dyes have been reported [Yamamoto et al., 27th
Proceedings of the Japan Society of Applied Physics 1p-P-9 (1980)], and a proposal based on this has been made in JP-A-58-112790.
These dyes have a low solubility in a solvent, are easily crystallized, and are extremely unstable with respect to a reading light and are immediately decolorized, and thus cannot be put to practical use, especially when formed as a coating film.

In view of such circumstances, the inventors of the present invention previously found that an indolenine-based resin having high solubility in a solvent, low crystallization, thermal stability, and high reflectance of a coating film. It has been proposed to use a cyanine dye as a single layer film (Japanese Patent Application Nos. 57-134397 and 57-134170).

Further, in other cyanine dyes such as indolenine type, thiazole type, quinoline type and selenazole type, a long chain alkyl group is introduced into the molecule to improve solubility and prevent crystallization. It is proposed to get rid of it (Japanese Patent Application No. 57-182589, No. 57-177776, etc.).

Further, in order to improve photostability, and particularly to prevent decolorization (reproduction deterioration) due to reading light, it has been proposed to add a transition metal compound quencher to a cyanine dye (Japanese Patent Application No. 57- 166832, 57-168048, etc.).

Further, it has been proposed to form an ionic bond between a dye and a quencher, thereby further reducing regeneration deterioration and improving stability (Japanese Patent Application No. 59-148).
48, 59-18878, 59-19715).

By the way, in the optical recording film made of the dye or the dye composition, pits are formed at the same time as the light irradiation,
The irradiation light after that is not absorbed in the central part where the energy is most concentrated.

Therefore, the energy utilization efficiency is low, and the sensitivity is not improved beyond a certain value.

Therefore, the present inventors previously formed a high melting point film, such as a colloidal particle dispersion liquid coating film of a silicon-based condensate, as a surface layer to form a pit for irradiation light for a certain period of time. It provides that the pits are formed at a stretch by waiting for the temperature to rise to a sufficient temperature without forming the pits to improve the sensitivity (Japanese Patent Application No. 59-62386, etc.).

However, in such a case, the pits are formed all at once, so that the sensitivity is improved, but at the same time, the surface layer is crushed and scattered, which scatters on other tracks and reduces the S / N ratio. It has been found that there may be inconveniences such as increasing the error rate.

[0029]

DISCLOSURE OF THE INVENTION An object of the present invention is to improve the surface layer of an optical recording medium having a recording layer composed of a dye or a dye composition so that the sensitivity is high and the S
It is to make the / N ratio high and the error rate small.

[0030]

The above object is achieved by the present invention described in (1) and (2) below. (1) In an optical recording medium having a recording layer containing a combination of a dye cation and a quencher anion as a light absorbing dye on a substrate, and having a surface layer on the recording layer, the surface layer is more than the recording layer. An optical recording medium comprising a first surface layer of an inorganic film having a high melting point and a polymer film laminated on the first surface layer. (2) Optical recording is performed by irradiating an optical recording medium having a recording layer containing a combination of a dye cation and a quencher anion as a light absorbing dye on a substrate and having a surface layer on the recording layer with laser light. In carrying out the above, as the surface layer, a first surface layer of an inorganic film having a melting point higher than that of the recording layer and a polymer film laminated on the first surface layer are provided, and sufficient energy is applied to the first surface layer. An optical recording method for improving sensitivity by preventing recording on a recording layer until absorption, and for preventing scattering of crushed pieces during recording by the polymer film.

[0031]

Specific Structure The specific structure of the present invention will be described in detail below.

The recording layer of the optical recording medium of the present invention contains an ionic bond of a dye and a quencher as a light absorbing dye.

As the dye-quencher ion bond, those described in Japanese Patent Application No. 59-14848 may be used.

However, more preferably used are the conjugates of the cyanine dye cation and the quencher anion described in Japanese Patent Application Nos. 59-18878 and 59-19715.

Such a conjugate has the following formula [I]:
Are preferred.

Formula [I] Φ-L = Ψ (Q ⁻ ) _{m In the} above formula [I], Ψ and Φ are indoles to which an aromatic ring such as a benzene ring, a naphthalene ring or a phenanthrene ring may be condensed. And ring, thiazole ring, oxazole ring, selenazole ring, imidazole ring, pyridine ring and the like.

These Φ and Ψ may be the same or different, but they are usually the same, and various substituents may be bonded to these rings. Note that Φ is
The nitrogen atom in the ring has a positive charge, and in Ψ, the nitrogen atom in the ring is neutral.

Examples of the skeletal rings of Φ and Ψ include the followings, but those represented by the formulas [ΦI] to [ΦXV] are preferable. In the following, the structure is shown in the form of Φ.

[0039]

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[0040]

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[0041]

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[0042]

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[0043]

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[0044]

[Chemical 6]

[0045]

[Chemical 7]

[0046]

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[0047]

[Chemical 9]

[0048]

[Chemical 10]

[0049]

[Chemical 11]

[0050]

[Chemical 12]

[0051]

[Chemical 13]

[0052]

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[0053]

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[0054]

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In such various rings, the group R ₁ (R ₁ , R ₁ ′) bonded to the nitrogen atom (two nitrogen atoms in the imidazole ring) in the ring is a substituted or unsubstituted alkyl group or aryl. It is a base.

There is no particular limitation on the number of carbon atoms of the groups R ₁ and R ₁ 'bonded to the nitrogen atom in such a ring. When this group further has a substituent, the substituent is a sulfonic acid group, an alkylcarbonyloxy group, an alkylamido group, an alkylsulfonamido group,
Alkoxycarbonyl group, alkylamino group, alkylcarbamoyl group, alkylsulfamoyl group, hydroxyl group,
It may be a carboxy group, a halogen atom or the like.

Further, when the rings of Φ and Ψ are fused or non-fused indole rings (formula [ΦI] to [ΦIV]), two substituents R ₂ and R ₃ are bonded to the _3-position. Preferably. In this case, the two substituents R ₂ and R ₃ bonded to the 3-position are preferably an alkyl group or an aryl group. And, of these, an unsubstituted alkyl group having 1 or 2 carbon atoms, particularly 1, is preferable.

On the other hand, another substituent R ₄ may be further bonded to a predetermined position in the ring represented by Φ and Ψ. Examples of such a substituent include an alkyl group, an aryl group, a heterocyclic residue, a halogen atom, an alkoxy group, an aryloxy group, an alkylthio group, an arylthio group, an alkylcarbonyl group, an arylcarbonyl group, an alkyloxycarbonyl group and an aryloxycarbonyl. Group, alkylcarbonyloxy group, arylcarbonyloxy group, alkylamido group, arylamido group, alkylcarbamoyl group, arylcarbamoyl group, alkylamino group, arylamino group, carboxylic acid group, alkylsulfonyl group, arylsulfonyl group, alkylsulfone It may be various substituents such as an amide group, an aryl sulfonamide group, an alkylsulfamoyl group, an arylsulfamoyl group, a cyano group and a nitro group.

The number of these substituents (p, q,
r, s, t) is usually 0 or about 1 to 4.
When p, q, r, s, and t are 2 or more, a plurality of R ₄ may be different from each other.

Among these, the expressions [ΦI] to
Those having a condensed or non-condensed indole ring of [ΦIV] are preferable. These are solubility in solvent, coating property,
The stability is excellent, the reflectance is extremely high, and the read S / N ratio is extremely high.

On the other hand, L represents a linking group for forming a mono-, di-, tri- or tetracarbocyanine dye, and examples thereof include the following, particularly those of the formulas [LI] to [LVII:
It is preferably any one of I].

[0062]

[Chemical 17]

[0063]

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[0064]

[Chemical 19]

[0065]

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[0066]

[Chemical 21]

[0067]

[Chemical formula 22]

[0068]

[Chemical formula 23]

[0069]

[Chemical formula 24]

[0070]

[Chemical 25]

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, an ethoxycarbonylpiperazine group. And a disubstituted amino group, an alkylcarbonyloxy group such as an acetoxy group, an alkylthio group such as a methylthio group, a cyano group, a nitro group, and a halogen atom such as Br and Cl.

In these formulas [LI] to [LVIII], a tricarbocyanine linking group, especially formula [LII],
[LIII] is preferred.

Specific examples of the cyanine dye cation D ⁺ forming the conjugate in the present invention will be given below, but the present invention is not limited thereto.

[0074]

[Table 1]

[0075]

[Table 2]

[0076]

[Table 3]

[0077]

[Table 4]

[0078]

[Table 5]

[0079]

[Table 6]

[0080]

[Table 7]

In the formula [I], Q ⁻ represents a quencher anion, and m is 1.

Q ⁻ may be any anion form of the quencher Q described in 1) to 8) below.

1) Bisdithio-represented by the following chemical formula 26
α-diketone

[0084]

[Chemical formula 26]

Here, R ^{1 to} R ⁴ represent a substituted or unsubstituted alkyl group or aryl group, and M is Ni,
It represents a transition metal atom such as Co, Cu, Pd, or Pt.

In this case, M has a negative charge and may form a salt with a cation (Cat) such as a quaternary ammonium ion.

Specific examples of the combination of R ^{1 and the} like in Chemical formula 26 are shown below. In the following description, ph is a phenyl group, φ is a 1,4-phenylene group, and φ ′ is a 1,2-phenylene group. The group, benz, means that groups that are adjacent to each other on the ring are bonded to each other to form a condensed benzene ring.

[0088]

[Table 8]

2) Bisphenyldithiol system represented by the following chemical formula 27

[0090]

[Chemical 27]

Here, R ^{5 to} R ⁸ represent hydrogen or an alkyl group such as a methyl group and an ethyl group, a halogen atom such as Cl, or an amino group such as a dimethylamino group and a diethylamino group, and M represents Ni, Co, Cu, Pd,
Represents a transition metal atom such as Pt.

In addition, M in the above structure has a -charge and is 4
A salt may be formed with a cation (Cat) such as a primary ammonium ion, and further, another ligand may be bonded to the upper and lower sides of M.

Examples of such a device are as follows. Here, the chemical formula 27 is used and shown by a combination of R ^{5 and the} like.

[0094]

[Table 9]

[0095]

[Table 10]

In addition to these, there are those described in Japanese Patent Application Laid-Open No. 50-45027 and Japanese Patent Application No. 58-163080.

3) Those represented by the following chemical formula 28

[0098]

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Here, M represents a transition metal atom, and Q
¹ is Q ¹¹ and Q ¹² shown in the following Chemical Formula 29, and Cat
Represents a cation.

[0100]

[Chemical 29]

Specific examples will be shown below with combinations of M and the like in Chemical formula 28.

[0102]

Besides, there is one described in Japanese Patent Application No. 58-125654.

4) What is shown in the following chemical formula 30

[0105]

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Here, M represents a transition gold atom, A represents S, C (R ¹¹ ) (R ¹² ), or a compound of formula 31,

[0107]

[Chemical 31]

R ¹¹ and R ¹² are CN and COR, respectively.
¹³ , COOR ¹⁴ , CON (R ¹⁵ ) (R ¹⁶ ) or SO ₂
Represents R ^17, R ¹³ ~R ¹⁷ each represent a hydrogen atom or a substituted or unsubstituted alkyl group or aryl group, Q ² (Chemical formula 31) is required to form a 5-membered or 6-membered ring Represents an atomic group, Cat represents a cation, and n is 1 or 2.

Specific examples will be shown below with combinations of M and the like in Chemical formula 30.

[0110]

[Table 11]

In addition to this, there is one described in Japanese Patent Application No. 58-127074.

5) Compound represented by the following chemical formula 32

[0113]

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Here, M represents a transition metal atom, and Ca
t represents a cation, and n is 1 or 2.

Specific examples will be shown below with combinations of M and the like in Chemical formula 32.

[0116]

In addition, there is one described in Japanese Patent Application No. 58-127075.

6) Thiocatechol chelate system represented by the following chemical formula 33

[0119]

[Chemical 33]

Where M is Ni, Co, Cu, Pd,
Represents a transition metal atom such as Pt.

In addition, M has a-charge and is a cation (Cat).
And a benzene ring may have a substituent.

Specific examples will be shown below with combinations of M and the like in Chemical formula 33.

[0123]

7) Compound represented by the following chemical formula 34

[0125]

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Here, R ¹⁸ represents a monovalent group, and k
Is 0 to 6, M represents a transition metal atom, and Ca
t represents a cation.

Specific examples will be shown below in combination of M and the like in Chemical formula 34.

[0128] ^{M R 18 k Cat Q7-1 Ni H} 0 N + (nC 4 H 9) 4 Q7-2 Ni CH 3 1 N + (nC 4 H 9) 4

In addition, there is one described in Japanese Patent Application No. 58-143531.

8) Thiobisphenolate chelate system represented by the following chemical formula 35

[0131]

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Here, M is the same as defined above, and R ⁶⁵ and R ⁶⁶ represent an alkyl group. Further, M has a-charge and may form a salt with a cation (Cat).

Specific examples will be shown below with combinations of M and the like in Chemical formula 35.

[0134]

Specific examples of the conjugate of the dye cation and the quencher anion used in the present invention will be given below. In addition,
D ⁺ is the dye cation described above, Q ⁻ is the quencher anion corresponding to the quencher described above, and is indicated by a combination thereof.

[0136]

[Table 12]

[0137]

[Table 13]

[0138]

[Table 14]

The dye-quencher conjugate having such a light absorbing property is appropriately selected and used according to the light source to be used.

Such a dye-quencher conjugate is
The recording layer can be formed alone.

Alternatively, the recording layer is formed together with the resin.

The resin used is a self-oxidizing resin,
Alternatively, a thermoplastic resin is suitable.

The self-oxidizing resin contained in the recording layer is
Among them, nitrocellulose is particularly preferable, although it causes oxidative decomposition when the temperature is raised.

The thermoplastic resin is softened by the temperature rise of the dye that has absorbed the recording light, and various known thermoplastic resins can be used.

Among these, the thermoplastic resins which can be used particularly preferably include the following.

I) Polyolefin Polyethylene, polypropylene, poly-4-methylpentene-1 and the like.

Ii) Polyolefin Copolymer For example, ethylene-vinyl acetate copolymer, ethylene-acrylic acid ester copolymer, ethylene-acrylic acid copolymer, ethylene-propylene copolymer, ethylene-butene-1 copolymer. Coalesce, ethylene-maleic anhydride copolymer,
Ethylene propylene terpolymer (EPT) etc. In this case, the polymerization ratio of the comonomer can be arbitrary.

Iii) Vinyl chloride copolymer For example, vinyl acetate-vinyl chloride copolymer, vinyl chloride-vinylidene chloride copolymer, vinyl chloride-maleic anhydride copolymer, acrylic ester or methacrylic ester and chloride Copolymer with vinyl, acrylonitrile-vinyl chloride copolymer, vinyl chloride ether copolymer,
Ethylene or propylene-vinyl chloride copolymer, ethylene-vinyl acetate copolymer graft-polymerized with vinyl chloride, etc. In this case, the copolymerization ratio can be arbitrary.

Iv) Vinylidene chloride copolymers Vinylidene chloride-vinyl chloride copolymers, vinylidene chloride-vinyl chloride-acrylonitrile copolymers, vinylidene chloride-butadiene-vinyl halide copolymers and the like. In this case, the copolymerization ratio can be arbitrary.

V) Polystyrene vi) Styrene copolymer For example, styrene-acrylonitrile copolymer (AS resin), styrene-acrylonitrile-butadiene copolymer (ABS resin), styrene-maleic anhydride copolymer (SMA resin). , Styrene-acrylic acid ester-acrylamide copolymer, styrene-butadiene copolymer (SBR), styrene-vinylidene chloride copolymer, styrene-methyl methacrylate copolymer and the like. In this case, the copolymerization ratio can be arbitrary.

Vii) Styrene-type polymer For example, α-methylstyrene, p-methylstyrene,
2,5-dichlorostyrene, α, β-vinylnaphthalene, α-vinylpyridine, acenaphthene, vinylanthracene and the like, or copolymers thereof, such as α-
Copolymer of methylstyrene and methacrylic acid ester.

Viii) Coumaron-indene resin Coumaron-indene-styrene copolymer.

Ix) Terpene resin or picolite For example, a terpene resin which is a polymer of limonene obtained from α-pinene, or picolite obtained from β-pinene.

X) Acrylic resin In particular, an acrylic resin containing an atomic group represented by the following chemical formula 36 is preferable.

[0155]

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In the above formula, R ₁₀ represents a hydrogen atom or an alkyl group, and R ₂₀ represents a substituted or unsubstituted alkyl group. In this case, in the above formula, R ₁₀ is
A hydrogen atom or a lower alkyl group having 1 to 4 carbon atoms, particularly a hydrogen atom or a methyl group is preferable. R ₂₀ may be a substituted or unsubstituted alkyl group, but the alkyl group preferably has 1 to 8 carbon atoms, and when R ₂₀ is a substituted alkyl group, it is an alkyl group. The substituent for substituting the group is preferably a hydroxyl group, a halogen atom or an amino group (particularly a dialkylamino group).

The atomic group represented by the above formula may form a copolymer with other repeating atomic groups to form various acrylic resins. The acrylic resin is constituted by forming a homopolymer or a copolymer having 1 or 2 or more of the above as a repeating unit.

Xi) Polyacrylonitrile xii) Acrylonitrile copolymer For example, acrylonitrile-vinyl acetate copolymer, acrylonitrile-vinyl chloride copolymer, acrylonitrile-styrene copolymer, acrylonitrile-vinylidene chloride copolymer, acrylonitrile-vinyl pyridine. Copolymer, acrylonitrile-methyl methacrylate copolymer,
Acrylonitrile-butadiene copolymer, acrylonitrile-butyl acrylate copolymer and the like. In this case, the copolymerization ratio can be arbitrary.

Xiii) Diacetone acrylamide polymer A diacetone acrylamide polymer obtained by reacting acrylonitrile with acetone.

Xiv) Polyvinyl acetate xv) Vinyl acetate copolymer For example, copolymers with acrylic acid ester, vinyl ether, ethylene, vinyl chloride and the like. The copolymerization ratio may be arbitrary.

Xvi) Polyvinyl ether For example, polyvinyl methyl ether, polyvinyl ethyl ether, polyvinyl butyl ether and the like.

Xvii) Polyamide In this case, as the polyamide, in addition to ordinary homonylon such as nylon 6, nylon 6-6, nylon 6-10, nylon 6-12, nylon 9, nylon 11, nylon 12, nylon 13, etc. , Nylon 6 / 6-6 / 6-1
0, nylon 6 / 6-6 / 12, nylon 6 / 6-6 /
It may be a polymer such as 11, or modified nylon in some cases.

Xviii) Polyester For example, with an aliphatic dibasic acid such as oxalic acid, succinic acid, maleic acid, adipic acid, and sebastenic acid, or various dibasic acids such as aromatic dibasic acid such as isophthalic acid and terephthalic acid. Condensates and co-condensates with glycols such as ethylene glycol, tetramethylene glycol and hexamethylene glycol are preferable.

Of these, a condensate of an aliphatic dibasic acid and a glycol, and a cocondensate of a glycol and an aliphatic dibasic acid are particularly preferable.

Further, for example, a modified glyptal resin obtained by esterifying a glyptal resin, which is a condensate of phthalic anhydride and glycerin, with a fatty acid, a natural resin or the like is also suitably used.

Xix) Polyvinyl acetal resin Polyvinyl formal and polyvinyl acetal resin obtained by acetalizing polyvinyl alcohol are preferably used.

In this case, the degree of acetalization of the polyvinyl acetal resin can be arbitrary.

Xx) Polyurethane resin A thermoplastic polyurethane resin having a urethane bond. In particular,
Polyurethane resins obtained by condensation of glycols and diisocyanates, particularly polyurethane resins obtained by condensation of alkylene glycols and alkylene diisocyanates, are suitable.

Xxi) Polyether Styrene formalin resin, ring-opening polymer of cyclic acetal, polyethylene oxide and glycol, polypropylene oxide and glycol, propylene oxide-ethylene oxide copolymer, polyphenylene oxide and the like.

Xxii) Cellulose derivatives For example, various esters of cellulose such as nitrocellulose, acetyl cellulose, ethyl cellulose, acetyl butyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, methyl cellulose, ethyl hydroxyethyl cellulose, ethers and mixtures thereof.

Xxiii) Polycarbonate For example, polydioxydiphenylmethane carbonate,
Various polycarbonates such as dioxydiphenyl propane carbonate.

Xxiv) Ionomer Methacrylic acid, acrylic acid, and other Na, Li, Zn,
Mg salt etc.

Xxv) Ketone resin For example, a condensation product of a cyclic ketone such as cyclohexanone or acetophenone and formaldehyde.

Xxvi) Xylene resin For example, a condensate of m-xylene or mesitylene and formalin, or a modified product thereof.

Xxvii) Petroleum resin C ₅ type, C ₉ type, C ₅ -C ₉ copolymer type, dicyclopentadiene type, or copolymers or modified products thereof.

Xxviii) A blend of two or more of the above i) to xxvii), or a blend with another thermoplastic resin.

The self-oxidizing or thermoplastic resin may have various molecular weights.

The self-oxidizing compound or thermoplastic resin and the dye-quencher conjugate are
Usually, the layer is formed in a wide range of the weight ratio of 1 to 0.1 to 100.

In order to form such a recording layer, generally, it may be coated by a conventional method. And the thickness of the recording layer is
Usually, it is about 0.03 to 2 μm.

The recording layer has a thickness of 0.04 to 0.12 μm.
, Particularly preferably 0.05 to 0.08 μm.

At 0.04 μm or less, especially 0.03 μm or less, both the absorption amount and the reflection amount are small, and the writing sensitivity and the reproducing sensitivity cannot be large.

When the thickness is 0.12 μm or more, the pregroup is buried and it becomes difficult to obtain a tracking signal. Further, it is not easy to form pits, and the writing sensitivity is reduced.

In addition, in such a recording layer, other dyes, other polymers or oligomers, various plasticizers, surfactants, antistatic agents, lubricants, flame retardants, stabilizers,
A dispersant, an antioxidant, a crosslinking agent and the like may be contained.

In order to form such a recording layer, it is sufficient to coat the substrate with a predetermined solvent and dry it.

The solvent used for coating is, for example, a ketone system such as methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone, an ester system such as butyl acetate, ethyl acetate, carbitol acetate, butyl carbitol acetate, methyl cellosolve, ethyl cellosolve, etc. The ether type, aromatic type such as toluene or xylene, alkyl halide type such as dichloroethane, alcohol type and the like may be used.

The substrate on which such a recording layer is provided is made of resin. Various materials can be used as the resin material.

However, in such a resin, it is particularly easy to be exposed to the above-mentioned various coating solvents, particularly ketone-based, ester-based, alkyl halide, etc., and the effect of the underlayer of the present invention is particularly great. , Acrylic resin or polycarbonate resin.

Since these are substantially transparent to writing and reading light, writing and reading can be performed from the back surface side of the substrate, and sensitivity and S
It is advantageous in terms of the / N ratio and the like, and is also advantageous in terms of mounting such as measures against dust. Further, since the moldability is good, it is easy to form the groove for tracking.

The acrylic resin is preferably a copolymer or homopolymer mainly composed of a methacrylic acid ester having a chain or cyclic alkyl group having 1 to 8 carbon atoms such as polymethylmethacrylate.

The polycarbonate resin is preferably bisphenol A type.

When the acrylic resin or the polycarbonate resin is formed by injection molding, the effect of the underlayer of the present invention becomes greater.

The number average degree of polymerization of these acrylic resins or polycarbonate resins is preferably about 800 to 6000.

The surface layer provided on the recording layer comprises a first surface layer and a polymer film laminated on the first surface layer.

The first surface layer may be an inorganic film having a melting point higher than that of the recording layer and a hardness higher than that.

Accordingly, various oxide-based, nitride-based, and carbide-based inorganic materials such as silicon oxide, titanium oxide, aluminum oxide, magnesium oxide, zircon oxide, silicon nitride, and silicon carbide can be used as a vapor deposition film. It may be.

Alternatively, it may be a hydrolyzed coating film mainly formed of silicon oxide, titanium oxide, zirconate acid, aluminum oxide or the like formed from a chelate compound known as a so-called crosslinking agent.

However, of these, the most useful is a coating film of a colloidal particle dispersion of a silicon-based condensate.

The colloidal particles of the silicon-based condensate are preferably hydrolyzed condensates of silicon halide, especially silicon tetrachloride, or alkyl silicic acid, especially tetra-lower alkyl (methyl, ethyl) silicic acid.

The colloidal particle size is 30-100.
A, especially about 50 to 80 A.

As the dispersion medium, alcohol, particularly one aliphatic alcohol, alkyl acetate, a mixed solvent of these and aromatic hydrocarbon, or the like is used.

For hydrolysis, a mineral acid is added if necessary.

Then, if necessary, a stabilizer such as ethylene glycol or a surfactant is added.

One example of such a colloidal particle dispersion is silicon tetrachloride (S) described in JP-B-31-6533.
iCl ₄ ) and a monohydric aliphatic alcohol are dissolved in an alkyl acetate ester.

Further, a solution containing tetraalkylsilicic acid, a monohydric aliphatic alcohol, an alkyl acetate and a mineral acid described in JP-B-36-4740 may be added with 1 to 20 wt% of ethylene glycol. .

Further, an alcohol solution of a tetra-lower alkylsilicic acid described in JP-B-45-35435 may be used.

In such a case, the monohydric aliphatic alcohol used is methyl alcohol, ethyl alcohol, denatured alcohol, isopropyl alcohol, butyl alcohol, or a mixture thereof,

As the alkyl acetate, methyl acetate, ethyl acetate, amyl acetate, butyl acetate or a mixture thereof is used.

As the mineral acid, an aqueous solution of hydrochloric acid, sulfuric acid, etc.,
What is normally used industrially may be used.

The dispersion may be applied by spinner coating or the like according to a conventional method.

In this case, the diluting solvent may be, for example, a mixed solvent of a hydrocarbon type and an alcohol type.

Then, the drying is carried out at 40 to 80 ° C. for 20
It suffices to do it for about 2 minutes to 2 hours.

The coating film thus formed is a silicon oxide inorganic coating film containing a hydroxyl group.

The thickness of the first surface layer is 0.005 to 0.005.
It is 0.05 μm. Particularly preferably, 0.008-
It is preferably 0.012 μm.

If the thickness of the first surface layer is less than 0.003 μm, the effect of improving the read / write sensitivity of the optical recording medium cannot be obtained.

When the first surface layer exceeds 0.03 μm, the sensitivity of writing and reading as an optical recording medium is rather lowered.

In the optical recording film made of the dye composition, pits are formed at the same time as the light irradiation, and the irradiation light thereafter is not absorbed in the central portion where the energy is most concentrated.
Therefore, the use efficiency of energy is low, which causes the sensitivity not to improve more than a certain value.

In the present invention, by providing a hard film having a high melting point as the first surface layer, pits are not formed with respect to irradiation light for a certain time or less, and after waiting for the temperature to rise to a sufficient temperature, The pits are formed at once.

The polymer film laminated on the first surface layer as described above is for preventing scattering of crushed pieces of the first surface layer when forming pits.

Various polymers can be used as the polymer to be used. Particularly, for the first surface layer, the dye is not dissolved by invading the first surface layer, the adhesion is good, the uniformity is good, and the coating is good. From the viewpoints of easy handling, low viscosity, and the like, it is preferable to use a coating film of a polymer compound that is soluble in water or a water-alcohol mixed solvent and has a hydroxyl group.

In this case, the term "soluble in water or water-alcohol mixed solvent" means that it is soluble in water or a water-alcohol mixed solvent as described later by about 1% or more.

Such polymer compounds may be polysaccharides such as gum arabic, alginic acid and tragacanth gum, but the following cellulose derivatives and vinyl alcohol unit-containing resins are particularly preferable.

1) Cellulose derivative Nitrocellulose, acetylcellulose, ethylcellulose, acetylbutylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, methylcellulose, ethylhydroxyethylcellulose and the like.

In this case, it is preferable that one or more hydroxyl groups are contained on average per repeating unit.

2) Vinyl alcohol unit-containing resin Complete or partial hydrolyzate of polyvinyl alcohol, polyvinyl acetate, ethylene-vinyl acetate copolymer and the like.

In this case, the vinyl alcohol unit is 70
It is preferable that the content is at least mol%, preferably at least 80 mol%.

The number average molecular weight of such a polymer compound is not particularly limited.

Such a polymer compound is usually dissolved in a water-alcohol mixed solvent to form a coating layer.

In this case, the alcohol is preferably a single or complex system such as methanol, ethanol, propanol, butanol and the like. The mixing ratio of water and alcohol is about 1: 0.5 to 3.

Although water alone can be used as the coating solvent, a water-alcohol mixed solvent is superior in terms of coating properties on a resin substrate.

When coating such a layer, a crosslinking agent may be added to the coating solution to crosslink the polymer compound in the coating film.

At this time, solvent resistance, water resistance and heat resistance are improved, and stability of the recording layer is improved.

In this case, a surfactant, an antifoaming agent, an antistatic agent, etc. are added to the coating liquid in order to prevent the generation of pinholes, completely defoam, and lower the viscosity. Good.

The crosslinking agent used is an organic compound of titanium, zirconium or aluminum or a chelating agent.
It is preferably a todide, or an aldecht, an oxycarboxylic acid, or a methylol-containing oligomer.

Such a polymer film has a thickness of 0.002-0.8.
It is preferable that the thickness is μm, more preferably 0.005 to 0.5 μm.

This is because if it is less than 0.002 μm, there is no actual work of preventing scattering, and if it exceeds 0.8 μm, the sensitivity is decreased.

Further, the recording layer having the surface layer of the present invention is
It may be formed directly on the substrate, or may be provided via an underlayer.

The underlayer may be any of various known ones, but it is preferable that the underlayer is produced in exactly the same manner as the above-mentioned first surface layer or polymer film.

The thickness of the underlayer is 0.005 to 0.05 μm
Is. It is particularly preferably 0.008 to 0.03 μm.

If the thickness of the underlayer is less than 0.005 μm, the effect of imparting solvent resistance and heat resistance to the substrate is insufficient. If it exceeds 0.05 μm, the sensitivity decreases.

By providing the underlayer as described above, the sensitivity as an optical recording medium is further increased and the S / N ratio is further improved.

A recording layer is usually provided directly on the underlayer, but if necessary, another intermediate layer may be provided between the underlayer and the recording layer. it can.

Similarly, various uppermost protective layers, half mirror layers, reflecting layers and the like can be further provided on the surface layer. However, it is desirable that the reflective layer is not laminated.

The medium of the present invention may have the above-mentioned recording layer on one surface of such a substrate via an underlayer, or may have a recording layer on both surfaces thereof via an underlayer. It may be.

Further, two recording layers were coated on one surface of the substrate with an underlayer interposed between them. The recording layers were made to face each other and faced each other with a predetermined gap therebetween, and they were sealed to remove dust or dust. You can also prevent scratches.

The optical recording method of the present invention uses the optical recording medium of the present invention having the above-mentioned structure to irradiate a laser beam to perform optical recording.

In order to miniaturize the device, the light sources for writing and reading are preferably 750 and 7.
80,830nm semiconductor laser or 633nm H
It is preferable to use an e-Ne laser or the like.

[0247]

According to the present invention, the recording light is applied to the optical recording medium in a pulsed form while running or rotating.

At this time, the self-oxidizing resin is decomposed or the thermoplastic resin or the dye is melted by the heat generation of the dye-quencher combination which is the light absorbing dye in the recording layer, and pits are formed. It

In this case, it is preferable that writing is performed from the back side of the gas.

In particular, when a tri- or tetracarbocyanine dye-quencher conjugate is used, 750,7
When a recording semiconductor laser diode having a wavelength of 80 or 830 nm is used, extremely good writing can be performed.

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

In this case, it is preferable to irradiate the reading light from the back side of the substrate and detect the reflected light.

When a thermoplastic resin is used for the recording layer, the pits once formed in the recording layer can be erased by light or heat and rewriting can be performed.

The recording or reading light is H
An e-Ne laser or the like can also be used.

[0255]

According to the present invention, since the recording layer comprising the dye-quencher conjugate or the composition of this conjugate has the surface layer comprising the first surface layer and the polymer film, writing as an optical recording medium is possible. The sensitivity of is improved.

Since the polymer film prevents scattering of the first surface layer during pit formation, the S / N ratio is improved and the error rate is reduced.

[0257]

EXAMPLES The present invention will be described in more detail below by showing specific examples of the present invention.

Example Substrate A PMMA (MFI = 2) injection-molded substrate having a diameter of 30 cm was mixed with tetraethyl hydrochloric acid 4.2 parts ethyl alcohol 43 parts ethyl acetate 42 parts concentrated hydrochloric acid 5.4 parts ethylene glycol 5.4 parts. , 50 to 80% colloidal dispersion, and diluted with n-propanol to obtain a coating solution.

After spin-coating this, 60 ° C., 3
It was processed for 0 minutes. The film thickness is 0.01 μm.

Then, using a 1% solution of the conjugate SD1 of the dye cation D ⁺ 1 and the quencher anion Q ^- 2-8 [dichloroethane, diclohexanone (6: 5)],
A recording layer composed of the conjugate SD1 was formed with a spinner.

Further, a first surface layer was formed on the recording layer by spinner coating a solution prepared by diluting the colloidal dispersion with n-hexane. The film thickness was about 0.006 μm.

Furthermore, a polyvinyl alcohol PVA (205, manufactured by Kuraray Co., Ltd., hydrolysis rate 88%) dissolved in methanol-water (1: 1) at a concentration of 1% was applied and layered thereon. To make a polymer film. Thickness of about 0.01 μm
Met. The above is Sample 1.

A recording layer using SD16 was formed on the dye-quencher conjugate under the same conditions as in Sample 1. Surface layer,
The underlayer is the same as in sample 1. The above is referred to as Sample 2.

Then, in Sample 1, those without a polymer film are referred to as Sample 3, and those without a polymer film and a surface layer are referred to as Sample 4.

With respect to the above samples, the reflectance from the back surface side of the substrate at 830 nm was measured.

Further, the reciprocal of the minimum pulse width (ns) at which a reflection level ratio (extinction ratio) of 2 was obtained by writing from the back side of the substrate using an 830 nm semiconductor laser with a condensing part output of 10 mW was measured as the sensitivity.

Furthermore, with a spectrum analyzer manufactured by Hewlett-Packard Co., C at a bandwidth of 30 kHz was used.
The / N ratio was measured.

Further, the presence or absence of crushed pieces of the surface layer was observed with an electron microscope. The error rate was measured. The results are shown in Table 15.

[0269]

[Table 15]

From the results shown in Table 15, the effect of the present invention is clear.

The following Table 16 shows the polymer film and the first film.
The results of the sensitivity depending on the presence or absence of the surface layer and the presence or absence of crushed pieces are shown.

[0272]

[Table 16]

From Table 16, the effect of the present invention is clear.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kazuo Takahashi 1-13-1 Nihonbashi, Chuo-ku, Tokyo TDC Corporation (72) Inventor Akihiko Kuroiwa 1-13-1 Nihonbashi, Chuo-ku, Tokyo TDK Within the corporation

Claims (2)

(57) [Claims] 1. An optical recording medium having a recording layer containing, on a substrate, a combination of a dye cation and a quencher anion as a light absorbing dye, and having a surface layer on the recording layer, the surface layer is a recording layer. An optical recording medium comprising: a first surface layer of an inorganic film having a higher melting point than the layer; and a polymer film laminated on the first surface layer. 2. An optical recording medium having a recording layer containing a combination of a dye cation and a quencher anion as a light absorbing dye on a substrate, and having a surface layer on the recording layer is irradiated with laser light. When performing optical recording, as the surface layer, a first surface layer of an inorganic film having a melting point higher than that of the recording layer and a polymer film laminated on the first surface layer are provided, and the first surface layer is more sufficient. An optical recording method in which recording is not performed on a recording layer until energy can be absorbed to improve sensitivity, and the polymer film prevents scattering of shreds during recording.