JP3020256B2 - Optical recording medium - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical recording medium, in particular, a write-once optical recording disk compatible with a compact disk.

<Prior Art> An optical recording disk that can be additionally recorded or recorded in accordance with the compact disk (hereinafter abbreviated as CD) standard has been proposed (Nikkei Electronics, January 1989).
March 23, No. 465, P107, Kinki Chemical Association Functional Dye Subcommittee, March 3, 1989, Osaka Science and Technology Center, SPIE
vol 1078 Optical Data Storage Topical Meeting, 80 1
989 etc.).

This is formed by providing a dye layer, an Au reflection layer and a protective film in this order on a transparent resin substrate. That is,
The reflective layer is provided in close contact with the dye layer.

In the past, an air layer was provided on the dye layer to form pits in the dye layer.However, in this proposal, since the reflection layer is in close contact with the dye layer, the total thickness of the CD standard disc is 1.2mm configuration is possible.

<Problems to be Solved by the Invention> In the case of a contact-type medium in which such a reflective layer and a recording layer containing a dye are provided in close contact with each other, in particular, the erasing of the recording layer at the wavelength of the recording light and reproduction light. The extinction coefficient k and the refractive index n are
They have predetermined values of 0.03 to 0.25 and 1.8 to 4.0, respectively, and must have a reflectance of 60% or more, particularly 70% or more, in an unrecorded portion.

By the way, when a dye layer is used as a recording layer, it is known that the light absorbing dye has low light fastness, and in particular, the dye undergoes photon mode deterioration during repeated reproduction, thereby causing reproduction deterioration.

The present inventors have proposed to use a dye cation, an anion of a transition metal complex as a singlet oxygen quencher and an ionic conjugate in order to prevent this regeneration deterioration and improve light resistance. (Japanese Unexamined Patent Publication Nos. 60-1559087 and 60-16
No. 2691, No. 60-203488, No. 60-163243).

In such a conjugate, the dye cation and the quencher anion are present in a one-to-one relationship.

On the other hand, when a cationic dye and a quencher are mixed to form a recording layer, four kinds of ions, that is, a dye cation, a quencher ion, and each counter ion, are mixed according to the mixing ratio of the dye and the quencher. Exists.

Therefore, when the conjugate is used, since the respective counter ions of the dye and the quencher are not present, the reproduction deterioration is further reduced and the light resistance is improved as compared with the mixed system.

Further, many of the conjugates have a high and distinct melting point, but in a mixed system, the melting point decreases, the softening point becomes broad, and the thermal stability decreases.

For this reason, regeneration deterioration in the heat mode is reduced, and storage stability is improved.

 Further, the water resistance and the like are improved.

However, ordinary quencher anions have particularly large k. For this reason, if a binder is used for a contact-type medium, particularly k of the recording layer increases, and the reflectance decreases, so that good reproduction cannot be performed.

Therefore, to control k to a predetermined value, k
Must be further mixed with other light-absorbing dyes having a low light resistance, and light resistance, thermal stability, and the like are reduced.

As described above, the fact is that the characteristics of the bonded body exhibiting excellent light resistance and the like are not fully utilized in the contact type medium.

An object of the present invention is to provide a contact-type optical recording medium capable of performing good recording and reproduction and having sufficient light resistance, heat resistance, and water resistance.

<Means for Solving the Problems> Such an object is achieved by the present invention of the following (1) to (7).

(1) A recording layer containing a dye is provided on a substrate, and a reflective layer is laminated on the recording layer in close contact with the recording layer. The recording layer is irradiated with recording light to form a pit portion, and reproduction is performed. An optical recording medium for reproducing by light, wherein the recording layer contains an ionic combination of a cyanine dye cation and an anion of a copper complex of bisphenylenedithiol.

(2) When the reproducing light is irradiated from the substrate side, the reflectance of the unrecorded portion is 60% or more, and the reflectance of the recorded portion is 60% or less of the reflectance of the unrecorded portion. Optical recording medium.

(3) The extinction coefficient k of the recording layer at the wavelength of the recording light and the reproduction light is 0.03 to 0.25, and the refractive index n of the recording layer at the wavelength of the recording light and the reproduction light is 1.8 to 4.0. The optical recording medium according to (1).

(4) The optical recording medium according to any one of (1) to (3), wherein the wavelengths of the recording light and the reproduction light are 600 to 900 nm.

(5) At the interface between the substrate and the recording layer in the pit portion, there is a layer containing a decomposition product of the material of the recording layer and substantially not containing the material of the substrate. The optical recording medium according to any one of 4).

(6) The optical recording medium according to (5), wherein a void is formed in the pit portion.

(7) The above (1) containing two or more kinds of the ionic conjugates.
The optical recording medium according to any one of (1) to (6).

<Function> The anion of the quencher used in the present invention is
It has a low k of 0 to 0.01 at the reproduction light wavelength.

Therefore, k of the conjugate can also be a predetermined value,
Good recording and reproduction can be performed, and excellent characteristics such as light resistance, heat resistance, and water resistance inherent to the combined body can be exhibited.

<Specific Configuration> Hereinafter, a specific configuration of the present invention will be described in detail.

FIG. 1 shows an example of the optical recording medium 1 of the present invention.

The optical recording medium 1 is of a contact type in which a recording layer 3 containing a dye is provided on a substrate 2 and a reflective layer 4 and a protective film 5 are formed in close contact with the recording layer 3.

The substrate 2 is formed of a resin or glass which is substantially transparent (preferably at least 80% transmittance) to recording light and reproduction light (semiconductor laser light of about 600 to 900 nm, particularly about 700 to 800 nm, particularly 780 nm). Is done. This enables recording and reproduction from the back side of the substrate.

The substrate 2 is a disk having a normal size, and when used as a CD, has a thickness of about 1.2 mm and a diameter of 80 to 120 mm.
mm.

In this case, it is preferable to use a resin as the substrate material, and various thermoplastic resins such as polycarbonate resin, acrylic resin, amorphous polyolefin, and TPX are suitable.

If necessary, an oxygen barrier coating may be formed on at least one of the outer surface and the inner surface of the substrate 2 and, if necessary, on the inner and outer peripheral surfaces.

It is preferable that a groove for tracking is formed on the surface of the substrate 2 on which the recording layer 3 is formed.

The groove is preferably a spiral continuous groove, having a depth of 250 to 1800 mm and a width of 0.3 to 1.1 μm.
m, preferably 0.4 to 0.6 μm, and the land (portion between adjacent grooves) preferably 0.5 to 1.3 μm, particularly 1.0 to 1.2 μm.

With such a configuration of the groove, a good tracking signal can be obtained without lowering the reflection level of the groove portion.

The grooves may be provided with irregularities for address signals.

In the present invention, when the substrate has a groove, it is preferable that the recording light be applied to the recording layer in the groove. That is, the optical recording medium of the present invention is preferably used as an optical recording medium for groove recording. By using groove recording, the effective thickness of the recording layer can be increased.

Further, a resin layer (not shown) may be provided on the substrate 2 by, for example, the 2P method, and the resin layer may have grooves for tracking and unevenness for address signals.

The material of the resin constituting the resin layer is not particularly limited, and may be appropriately selected from known resins used in the so-called 2P method. Usually, a radiation-curable compound is used.

 The recording layer 3 contains a binder described below.

The extinction coefficient (imaginary part of the complex refractive index) k of the recording layer 3 at the wavelength of the recording light and the reproduction light is preferably 0.03 to 0.25.

If k is less than 0.03, the absorptivity of the recording layer decreases, and it is difficult to perform recording with normal recording power.

On the other hand, if k exceeds 0.25, the reflectivity falls below 60%, making it difficult to perform reproduction according to the CD standard.

In this case, when k is 0.04 to 0.20, particularly 0.05 to 0.15, and even more preferably 0.05 to 0.12, a very preferable result is obtained.

Further, the refractive index (the real part of the complex refractive index) n is preferably 1.8 to 4.0, more preferably 2.2 to 3.3.

When n <1.8, the reflectivity tends to decrease, and it is difficult to reproduce data according to the CD standard. Also, in order to make n> 4.0,
It is difficult to obtain raw material dyes.

The conjugate used is an ionic conjugate of a dye cation and a singlet oxygen quencher anion.

The anion of the singlet oxygen quencher used is an anion of a copper complex of bisphenylenedithiol, and one or more of those represented by the following formula [I] are particularly preferable.

Formula [I] In the above [I], R _{1 to} R ₄ are each substituted by a hydrogen atom, preferably an alkyl group having 1 to 8 carbon atoms, a halogen atom or an amino group or an alkyl group having 1 to 5 carbon atoms. It is preferably an amino group.

These quencher anions usually have a cation such as a quaternary ammonium ion as a counter ion. Such a quencher can be easily synthesized according to a conventional method.

Hereinafter, specific examples of the anion-type quencher having the quencher anion represented by the formula [I] will be described.

In the following, when any of R _{1 to} R ₄ is H, it is not displayed.

The single layer film of such a quencher exhibits a k of about 0 to 0.01 at the wavelength of the recording / reproducing light.

 Usually, n is about 1.5 or more.

The light-absorbing cationic dye used in the conjugate of the present invention has an absorption maximum of 600 to 900 nm, preferably 600 to 800 nm.
There is no particular limitation as long as it is a cationic dye having a nm, more preferably 650 to 750 nm, but one or more of a cyanine-based dye, a pyrylium or thiapyrylium salt-based dye, and an azurenium-based dye are preferred.

Among these, a cyanine dye, particularly a cyanine dye having an indolenine ring or a benzoindolenine ring is preferable.

As these dye cations, JP-A-60-159087,
Any of those disclosed in JP-A-60-162691, JP-A-60-203488, and JP-A-60-163243 can be used.

Hereinafter, specific examples of particularly preferable dyes having dye cations will be described.

These dye cations combine with various acid anions to form a cationic dye.

Such a cationic dye and an anionic quencher are easily synthesized as a conjugate of a dye cation and a quencher anion by the method described in the above publication.

 Hereinafter, specific examples of the conjugate of the present invention will be described.

In addition, for example, the anion of the quencher Q1 is Q ^- 1,
The cation of dye D1 is represented as D ⁺ 1 and the like.

These conjugates can be alone in the above ranges of n and k.

Then, the recording layer may be formed from such a combination.

On the other hand, k for the recording light and the reproduction light of the dye cation
Varies from 0 to about 2 depending on its skeleton and substituents.

For this reason, for example, when a cation-type dye having a k of 0.03 to 0.25 is selected to form a conjugate, there are limitations on its skeleton and substituents.

As a result, the coating solvent may be limited, or the coating may not be possible depending on the material of the substrate.

In addition, when a new molecular design is performed, great effort is required for design and synthesis.

On the other hand, according to the experiments of the present inventors, k of the mixed dye layer containing two or more kinds of dyes is a value substantially corresponding to the mixing ratio according to k of the dye layer composed of each dye used alone. It turned out to be.

Therefore, in the present invention, the recording layer 3 may be formed by dissolving a conjugate formed from two or more dye cations.

At this time, k is almost proportional to the mixing ratio in the mixed system of most of the dyes. That is, when the mixture fraction and k of the i kinds of conjugates are Ci and ki, respectively,
k is almost ΣCiki. Therefore, a recording layer having a predetermined k can be obtained by mixing the conjugates having different k's while controlling the mixing ratio. Therefore, a dye to be used can be selected from a very wide range of dye groups.

This can be applied to the improvement of the wavelength dependency. The wavelength of a semiconductor laser is usually in the range of ± 10 nm, and commercially available CD
For players, a reflectance of 70 from 770 to 790 nm
% Must be secured.

In general, the k value of the dye often has a large wavelength dependence, and even if it is an appropriate value at 780 nm, it is 770 or 790 nm.
In many cases, it will deviate greatly. In such a case, by mixing the conjugate using the second dye, it can be set so that appropriate n and k values are always obtained in the range of 780 ± 10 nm.

As a result, there is no limitation on the film forming method such as restrictions on the coating solvent and the like, and it is also possible to use an inexpensive dye that is easy to synthesize, to use a dye having good characteristics, and to use a hardly soluble dye. be able to.

When two or more binders are used for the recording layer 3, the binder to be used may be selected from those in the range of n = 1.6 to 6.5 and k = 0 to 2.

In this case, it is particularly preferable to use two or more kinds of conjugates having indolenine rings having different condensed states or having two or more kinds of indolenine cyanine dye cations having different methine chain lengths.

When measuring n and k, a recording sample is prepared by forming a recording layer on a predetermined transparent substrate to a thickness of, for example, about 400 to 800 mm under actual conditions. Next, the reflectance through the substrate or from the recording layer side is measured.

The reflectance is measured by specular reflection (about 5 °) using the recording / reproducing light wavelength. Also, the transmittance of the sample is measured.

From these measured values, for example, n and k may be calculated according to Kyoritsu Zensho “Optics” Kozo Ishiguro, pages 168 to 178.

The recording layer of the present invention may be formed from one or more of these conjugates of the present invention, but may also contain other light-absorbing dyes, quencher, or conjugate. You may.

However, the conjugate of the present invention has a total of 80 to 100 of the recording layer.
It preferably occupies by weight.

As a light-absorbing dye that can be used in combination, the absorption maximum is 600
~ 900nm, preferably 600 ~ 800nm, more preferably 650 ~
If it is 750 nm, there is no particular limitation, but cyanine-based,
One or more of phthalocyanine-based, naphthalocyanine-based, anthraquinone-based, azo-based, triphenylmethane-based, pyrylium or thiapyrylium salt-based, squarylium-based, croconium-based, and metal complex dye-based pigments are preferred.

The cyanine dye is preferably a cyanine dye having an indolenine ring, particularly a benzoindolenine ring.

Examples of quenchers that can be used in combination include bisacetylthionates, bisdithio-α-diketones, and bisdithiol compounds such as the bisphenylenedithiol compound of the above formula [I].
Metal complexes such as thiocatechol, salicylaldehyde oxime, and thiobisphenolate are preferred.

Further, amine quencher such as amine compound having nitrogen radical cation or hindered amine is also suitable.

When another conjugate is used in combination, a cyanine dye having an indolenine ring is preferable as a dye constituting the conjugate, and a metal complex dye such as a bisphenylenedithiol metal complex is preferable as a quencher.

Details of preferred dyes, quencher and conjugates are described in JP-A-59-24692, JP-A-59-55794, and JP-A-59-55795.
Nos. 59-81194, 59-83695, 60-18387,
No. 60-19586, No. 60-19587, No. 60-35054, No. 60
-36190, 60-36191, 60-44554, 60-445
No. 55, No. 60-44389, No. 60-44390, No. 60-47069
No. 60-20991, No. 60-71294, No. 60-54892,
No. 60-71295, No. 60-71296, No. 60-73891, No. 60
No. 73892, No. 60-73893, No. 60-83892, No. 60-854
No. 49, No. 60-92893, No. 60-159087, No. 60-162611
No. 60-203488, No. 60-201988, No. 60-234886
No. 60-234892, No. 60-16894, No. 61-11292,
No. 61-11294, No. 61-16891, No. 61-8384, No. 61-
No. 14988, No. 61-163243, No. 61-210539, Japanese Patent Application No. 60
-54013, JP-A-62-30088, JP-A-62-32132 and 62
No.-31792, published in CMC, "Functional Dye Chemistry", pp. 74-76.

It is preferable that the thickness of such a recording layer 3 be 500 to 2000 °. Outside of this range, the reflectivity decreases and it becomes difficult to perform reproduction according to the CD standard.

The method of forming the recording layer 3 is not particularly limited. However, in the present invention, it is preferable to form the recording layer 3 by coating from the viewpoint that the degree of freedom and easiness in selecting a dye, designing a medium, and manufacturing is further increased.

Various solvents such as ketones, esters, ethers, aromatics, alkyl halides, and alcohols can be used for coating the recording layer 3, and the degree of freedom in selecting a solvent is large. Spin coating or the like may be used for application.

Note that the recording layer 3 may be formed by a vapor deposition film in some cases.

On such a recording layer 3, a reflective layer 4 is provided in close contact with the recording layer.

Au, AlMg alloy, AlNi alloy, Ag, Pt
And high reflectivity metals such as Cu may be used.Among these, Au, AlMg alloy and
It is preferable to use any of the AlNi alloys. In addition, Al
The Mg content in the Mg alloy is preferably about 3 to 7% by weight. The Ni content in the AlNi alloy is preferably about 3 to 4 wt%.

The thickness of the reflective layer 4 is preferably 500 mm or more,
The layers may be formed by vapor deposition, sputtering, or the like. The upper limit of the thickness is not particularly limited, but is preferably about 1000 mm or less in consideration of cost, production operation time, and the like.

As a result, the reflectivity of the unrecorded portion of the medium through the substrate can be 60% or more, particularly 70% or more.

 On the reflective layer 4, a protective film 5 is provided.

The protective film 5 may be formed of various resin materials such as an ultraviolet-curing resin, for example, to a thickness of usually about 0.1 to 100 μm. The protective film 5 may be in the form of a layer or a sheet.

The protective film 5 is preferably a radiation-cured coating film containing a radiation-curable compound and a photopolymerization sensitizer.

Then, it is preferable that the hardness of the protective film 5 is H to 8H, particularly 2H to 7H in pencil hardness (JIS K-5400) at 25 ° C.

With this configuration, the jitter is significantly reduced.

In addition, the protective film and the reflective layer do not peel off during storage under high-temperature, high-humidity or temperature-humidity change conditions.

More specifically, when the hardness of the protective film is softer than H, the jitter increases, and when it is harder than 8H, the coating film becomes brittle and the film-forming ability decreases, and also the adhesive strength with the reflective layer decreases.

The radiation-curable compound used for forming such a protective film preferably contains an oligoester acrylate.

The oligoester acrylate is an oligoester compound having a plurality of acrylate groups or methacrylate groups. Preferred oligosteracrylates include those having a molecular weight of 1,000 to 10,000, preferably 2,000 to 7,000, and a degree of polymerization of 2 to 10, preferably 3 to 5. Of these, polyfunctional oligoester acrylates having 2 to 6, preferably 3 to 6, acrylate or methacrylate groups are preferred.

Multifunctional oligoester acrylates include Aronix M-7100, M-5400, M-5500, M-5700, and M-62.
Commercially available products such as 50, M-6500, M-8030, M-8060, and M-8100 (manufactured by Toagosei Chemical Co., Ltd.) can be used, and these are represented by the following formulas (A) and (B). It is what is done.

(A) (B) AMN _n- MA A: an acrylate group or a methacrylate group, M: a dihydric alcohol (eg, ethylene glycol, diethylene glycol, 1,6-hexane glycol, bisphenol A, etc.) residue, N: Dibasic acid (e.g., terephthalic acid, isophthalic acid, adipic acid, succinic acid, etc.) residue, n: 1 to 10,
Preferably 2-5 Of these, those represented by (A) are preferred.

Such an oligoester acrylate may be used alone.

Further, another radiation-curable compound may be used in combination. In such a case, the oligoester acrylate is preferably present in the radiation-curable compound in an amount of 20% by weight or more.

Other radiation-curable compounds can be used in combination with the above-mentioned oligoester acrylates, such as acrylic acid and methacrylic acid having an unsaturated double bond that is sensitive to ionization energy and exhibits radical polymerizability. Groups that are crosslinked or polymerized by irradiation such as acrylic double bonds such as acids or their ester compounds, allyl double bonds such as diallyl phthalate, unsaturated double bonds such as maleic acid and maleic acid derivatives, etc. And monomers, oligomers and polymers containing or introduced in the molecule. These are preferably polyfunctional, particularly preferably trifunctional or higher.

As the radiation-curable monomer, a compound having a molecular weight of less than 2,000 is used, and as the oligomer, one having a molecular weight of 2,000 to 10,000 is used.

These also include styrene, ethyl acrylate, ethylene glycol diacrylate, ethylene glycol dimethacrylate, diethylene glycol diacrylate, diethylene glycol methacrylate, 1,6-hexane glycol diacrylate, 1,6-hexane glycol dimethacrylate, etc. Examples thereof include pentaerythritol tetraacrylate (methacrylate), pentaerythritol acrylate (methacrylate), trimethylolpropane triacrylate (methacrylate), trimethylolpropane diacrylate (methacrylate), an acrylic modified product of urethane elastomer (Nipporan 4040), or these. Products with functional groups such as COOH, phenol ethylene oxide adducts Acrylate (methacrylate), pentaerythritol fused ring acrylic group (methacryl group) represented by the following general formula or ε- caprolactone - compound with a acryl group, In the formula, a compound of m = 1, a = 2, b = 4 (hereinafter referred to as special pentaerythritol condensate A), a compound of m = 1, a = 3, b = 3 (hereinafter, special pentaerythritol condensate B) A compound of m = 1, a = 6, b = 0 (hereinafter referred to as special pentaerythritol condensate C), a compound of m = 1, a = 6, b = 0 (hereinafter, special pentaerythritol condensate D) And special acrylates represented by the following general formula.

_{1) (CH 2 = CHCOOCH 2} ) 3 -CCH 2 OH ( special acrylate _{A) 2) (CH 2 =} CHCOOCH 2) 3 -CCH 2 OH ( special acrylate _{B) 3) [CH 2 =} CHCO (OC 3 H 6 _{) n -OCH 2] 3 -CCH 2} CH 3 ( special acrylate C) _{8) CH 2 = CHCOO- (CH} 2 CH 2 O) 4 -OCCH = CH 2 ( special acrylate H) As the radiation-curable oligomer, an acrylic modified urethane elastomer, or these materials may be used.
Examples include those into which a functional group such as COOH has been introduced.

Further, a radiation-curable compound obtained by subjecting a thermoplastic resin to radiation-sensitive modification in addition to or instead of the above-mentioned compounds may be used.

Specific examples of such a radiation-curable resin include acrylic acid having an unsaturated double bond showing radical polymerizability,
Radical irradiation-crosslinking or polymerizing groups such as acrylic double bonds such as methacrylic acid or their ester compounds, allyl double bonds such as diallyl phthalate, and unsaturated bonds such as maleic acid and maleic acid derivatives. Is contained or introduced in the molecule of the thermoplastic resin.

Examples of thermoplastic resins that can be modified into radiation-curable resins include vinyl chloride copolymers, saturated polyester resins,
Examples thereof include a polyvinyl alcohol resin, an epoxy resin, a phenoxy resin, and a cellulose derivative.

Other resins that can be used for radiation-sensitive modification include polyfunctional polyester resins, polyetherester resins, polyvinylpyrrolidone resins and derivatives (PVP
An olefin copolymer), a polyamide resin, a polyimide resin, a phenol resin, a spiroacetal resin, an acrylic resin containing at least one hydroxyl group-containing acrylic ester and methacrylic ester as a polymerization component are also effective.

The thickness of the protective film of such a radiation-curable compound is 0.1
-30 μm, more preferably 1-10 μm.

When the thickness is less than 0.1 μm, it is difficult to form a uniform film, the moisture-proof effect in a high humidity atmosphere is not sufficient, and the durability of the recording layer is reduced.

 In addition, the effect of preventing jitter is reduced.

On the other hand, if the thickness exceeds 30 μm, warpage of the recording medium and cracks in the protective film are likely to occur due to shrinkage of the resin film upon curing.

Such a coating film may be usually formed by combining various known methods such as spinner coating, gravure coating, spray coating, and dipping. The conditions for forming the coating film at this time may be appropriately determined in consideration of the viscosity of the mixture of the coating film composition, the desired thickness of the coating film, and the like.

In the present invention, examples of the radiation applied to the coating film include an ultraviolet ray and an electron beam, and an ultraviolet ray is preferable.

When ultraviolet rays are used, a photopolymerization sensitizer is usually added to the radiation-curable compound as described above.

As the photopolymerization sensitizer used in the present invention, a compound represented by the following general formula (I) is preferable. By using this with a polyfunctional oligoester acrylate,
The hardness described above is easily obtained, and the physical properties of the film are improved.

And peeling from the adhesive layer is reduced, and durability and moisture resistance are improved.

General formula (I) In the general formula (I), R represents a substituted or unsubstituted alkyl group having 1 to 4 carbon atoms, for example, a methyl group, an ethyl group, a propyl group, a butyl group and the like, and among them, a methyl group, an ethyl group and the like are preferable. .

L is a substituted or unsubstituted alkylene group having 1 to 3 carbon atoms, for example -CH ₂ -, Etc., among others Is preferred.

Y is a heterocyclic group such as morpholino, 2-morpholinyl, piperidino, 4-piperidinyl, 2-pyridyl, 2-quinolyl, 1-pyrrolidinyl, 1-
It represents a pyrrolyl group, a 2-thienyl group, a 2-furyl group or the like, and among them, a morpholino group is preferable.

RS- may be bonded to the benzene ring at any substitutable position of the benzene ring in the general formula (I), Is preferably the p-position.

In the present invention, among the compounds represented by the general formula (I), the most preferred are the following.

Compound A This compound A is commercially available as IRGACURE907 (manufactured by Nippon Ciba Geigy).

The compound represented by the general formula (I) functions as a photopolymerization initiator or a photopolymerization sensitizer during radiation curing.

The content of such a compound in the organic protective coat layer is 0.1 to 20% by weight, preferably 1 to 10% by weight.

If the amount is less than 0.1 wt%, the action as a photopolymerization initiator or a photopolymerization sensitizer is not sufficient. If the content exceeds 20 wt%, the remaining photopolymerization initiator or photopolymerization sensitizer permeates the recording layer, This is because it adversely affects the recording layer.

As the photopolymerization sensitizer, the following known compounds can be used in combination with the compound represented by the above general formula (I), if necessary.

For example, benzoin compounds such as benzoin methyl ether, benzoin ethyl ether, α-methylbenzoin, α-chlordeoxybenzoin, ketones such as benzophenone, acetophenone and bisdialkylaminobenzophenone, quinones such as acetolaquinone and phenanthraquinone, and benzyl disulfide And sulfides such as tetramethylthiuram monosulfide.

In order to cure the coating film containing the photopolymerization sensitizer and the radiation-curable compound with ultraviolet rays, various known methods may be used.

For example, an ultraviolet light bulb such as a xenon discharge tube and a hydrogen discharge tube may be used.

 In some cases, an electron beam can be used.

On such a protective film 5, a layered or sheet-shaped resinous protective layer may be further provided.

Another anti-jitter film may be provided on the reflection layer 4 and / or between the recording layer 3 and the reflection layer 4.

As such a jitter prevention film, there is a plasma polymerized film or an inorganic thin film. When provided on the reflective layer 4, the film itself may function as a protective film or a protective film may be further formed thereon.

The anti-jitter film 5 has a thickness of 0.05 μm or more, particularly 0.1 to 10 μm.
Preferably, the thickness is m.

If the film thickness is too thin, the effect of preventing jitter is reduced. If the film thickness is too thick, it deviates from the CD standard or the cost increases, and the effect corresponding to the film thickness cannot be obtained.

The plasma-polymerized film to be used may be any of known plasma-polymerized films, including C, and in addition to H,
It may contain halogens such as O, C and F, and various elements such as Si and N.

Of these, C and H and, if necessary, one of Si and O
Those containing at least one species are preferred.

At this time, known sources and conditions for plasma polymerization may be used.

Since these plasma polymerized films are substantially transparent, they may be provided on either the upper layer or the lower layer of the reflective layer.

On the other hand, various inorganic compounds may be used as the inorganic film. The inorganic film contains one or more of oxides, nitrides, carbides, silicides, and the like.
And an adhesive layer may be provided in close contact therewith.

The adhesive layer is composed of a hydrolytic condensate of an organic silicate compound, an organic titanate compound, an organic aluminate compound or an organic zirconate compound, or Si, Ti, Al or Zr.
It is preferable to contain a hydrolysis-condensation product of a halide.

As the organic titanate compound to be used, various known compounds can be used, and an alkyl titanate, a substituted alkyl titanate, an alkenyl titanate or a substituted alkenyl titanate is particularly preferable.

As the organic zirconate compound, various known compounds can be used, and particularly, an alkyl zirconate, a substituted alkyl zirconate, an alkenyl zirconate or a substituted alkenyl zirconate is preferred.

As the organic aluminate compound, an aluminum alkoxide and an aluminum chelate compound are preferable.

Among them, those having the following structural formula can be particularly preferably used.

M (OR ₁ ) (OR ₂ ) (OR ₃ ) (OR ₄ ) Al (OR ₁ ) (OR ₂ ) (OR ₃ ) Here, M represents Ti or Zr.

R ₁ , R ₂ , R ₃ and R ₄ are each a hydrogen atom,
Or a substituted or unsubstituted alkyl or alkenyl group. However, at least 2 out of R _{1 to} R ₄
It is preferable that the number is not a hydrogen atom but an alkyl group or an alkenyl group.

The substituted or unsubstituted alkyl or alkenyl group preferably has 2 to 18 carbon atoms.

In addition, as a group which substitutes an alkyl group or an alkenyl group, a substituted amino group such as a carboxyl group, an alkylcarboxy group, a di (hydroxyalkyl) amino group, a hydroxyl group, an alkyloxycarbonyl group, and the like are preferable.

Hereinafter, specific examples of preferable organic titanate compounds will be described.

T1 tetraethyl titanate T2 tetrapropyl titanate T3 tetraisopropyl titanate T4 tetra (n-butyl) titanate T5 tetra (isobutyl) titanate T6 tetra (sec-butyl) titanate T7 tetra (tert-butyl) titanate T8 tetra (2-ethylhexyl) titanate T9 Tetrastearyl titanate T10 hydroxytitanium stearate T11 isopropoxytitanium stearate T12 hydroxytitanium oleate T13 isopropoxytitanium oleate T14 di-i-propoxy bis (acetylacetone)
Titanate T15 di-n-butoxy bis (triethanolamine) titanate T16 dihydroxy bis (lactic acid) titanate T17 tetraoctylene glycol titanate T18 di-i-propoxy bis (ethyl acetoacetate)
Titanate Specific examples of preferred organic zirconate compounds are also given.

Tetra-n-propyl zirconate, tetra-i-propyl zirconate, tetra-n-butyl zirconate, tetra-i-butyl zirconate, zirconium tetraacetylacetonate, zirconium-2-ethylhexoate, zirconium naphthenic acid , Diacetate zirconic acid and the like.

Specific examples of preferred organic aluminate compounds will be given.

Aluminum-i-propylate, mono-sec-butoxyaluminum diisopropylate, aluminum-se
c-butyrate, ethyl acetoacetate aluminum diisopropylate, aluminum (ethyl acetoacetate) and the like.

As the organic silicate compound, an alkyl silicic acid, particularly a tetra-lower alkyl (methyl, ethyl) silicic acid is preferred.

The organic titanate compound, organic zirconate compound, organic aluminate compound, and organic silicate compound may form an oligomer or a colloidal condensed oxide in the coating solution.

As the halide, silicon halide, particularly silicon tetrachloride, is preferable.

In order to form an adhesive layer using such an organic silicate compound, an organic titanate compound, an organic aluminate compound, an organic zirconate compound or a halide, these are formed by using a solvent such as water, alcohol, hexane, or benzene, or a solvent such as these. It may be diluted with a mixed solvent, applied to the dye layer, and left to hydrolyze to obtain a condensate.

The method for applying the adhesive layer is not particularly limited, and spin coating or the like may be used.

The thickness of the adhesive layer is preferably from 10 to 300 °, particularly preferably from 20 to 100 °. If the thickness is less than this range, it will be optically non-uniform and the bonding strength will be insufficient. In addition, when the ratio exceeds this range, the optical characteristics change, and it becomes impossible to increase both the reflectance and the degree of modulation.

To perform recording or additional recording on the optical recording medium 1 having such a configuration, recording light of, for example, 780 nm is irradiated through the substrate 2 in a pulsed manner.

Thereby, the recording layer 3 absorbs light and generates heat, and at the same time, the substrate 2 is also heated. As a result, in the vicinity of the interface between the substrate 2 and the recording layer 3, melting or decomposition of the recording layer material such as a dye occurs, pressure is applied to the interface between the recording layer 3 and the substrate 2, and the bottom and side walls of the groove are deformed. May be caused.

In this case, the decomposed material layer 61 containing the melted or decomposed material of the recording layer 3 usually remains in a shape that covers the bottom and the boundary of the groove 23.

The material of the decomposition layer 61 is substantially a material that does not include the material of the substrate, and is composed of a decomposition product of the recording layer material or a mixture of the decomposition material of the recording layer material and the recording layer material.

The decomposition layer 61 is usually about 30 to 90% of the thickness of the recording layer 3.

Then, usually, a void 63 is formed on the decomposed substance layer 61 at the interface with the reflective layer, and the decomposed substance layer 61 and the void 63 are formed in the pit portion 6.

The gap 63 is usually about 10 to 70% of the thickness of the recording layer 3.

Further, in such a recording process, the substrate 2 may not be deformed, but the pit portion 6 of the substrate 2 is usually dented by the pressure at the time of heating. The dent amount of the substrate 2 is larger as the size of the pit portion 6 is larger.
The depth is about 300 mm.

Further, the recording layer 3 or a decomposition product thereof may be left on the gap 63 with a very small thickness in close contact with the reflection layer 4.

As described above, a layer substantially not containing the substrate material is formed at the interface between the substrate 2 and the recording layer 3 in the pit portion 6.

The present inventors have confirmed that no substrate material is contained between the substrate 2 and the recording layer 3 in the pit portion 6 as follows.

First, several sample pieces were prepared from one optical recording medium 1 manufactured and recorded under a certain condition, and the protective film 5 and the reflective layer 4 were peeled from each sample.

Next, the surface of the substrate 2 was washed with an alcohol-based solvent.

In this case, two types of cleaning conditions were used: weak cleaning in which the liquid was slightly shaken in an alcohol-based solvent, and strong cleaning in which ultrasonic cleaning was performed.

Then, the scanning tunneling microscope (ST
M) The thickness in the groove of the substrate 2 was determined from the output image.

As a result, in the case of the sample subjected to the ultrasonic cleaning having the strong cleaning power, the pit portion 6 of the substrate 2 was flat or dented.

On the other hand, the pit portion 6 of the substrate 2 of the sample which was cleaned with a weak cleaning power was raised.

From these results, the portion of the sample that was washed with a weak detergency appears to be raised, and the material of the recording layer, such as dye, was decomposed due to heat, that is, the degraded material of the recording layer material with reduced solubility was contained. Layer.

In fact, the residue after washing was measured by liquid chromatography, absorption spectrum, FTIR, MAS, etc.As a result, in the case of weak washing power, the presence of decomposed substances at the bottom of the pit and the absence of substrate material were confirmed. Has been confirmed.

As described above, the mechanism of the present invention is based on the proposal disclosed in Nikkei Electronics, January 23, 1989, No. 465, P107, that is, “When the recording laser beam is irradiated, the dye layer is melted or decomposed. The substrate is also softened, and the dye material and the substrate material are mixed at the interface to form a pit portion. "

As a result, the pit shape is improved, and the S / N ratio is improved.

The power of the recording light is about 5 to 9 mW, and the substrate linear velocity is about 1.2 to 1.4 m / s.

After the pit portion 6 is formed in this way, for example, 78
When the reproduction light of 0 nm is irradiated through the substrate 2, a phase difference of the light is generated by the pit portion 6, and the reflectance is 60% of the unsaturated portion.
%, Especially 50% or less, and even 40% or less.

On the other hand, since the unrecorded portion has a high reflectance of 60% or more, particularly 70% or more, it can be reproduced according to the CD standard.

 The power of the reproduction light is about 0.1 to 10 mW.

<Example> Example 1 A recording layer containing a dye was formed on a polycarbonate resin substrate having a continuous groove and a thickness of 120 mmφ and a thickness of 1.2 mm. On this recording layer, Au is deposited to a thickness of 1000 mm by vapor deposition to form a reflective layer. Further, an ultraviolet-curable resin containing oligoester acrylate is applied, and then ultraviolet-cured to form a protective film having a thickness of 5 μm. Disk samples were obtained.

 The dyes contained in the recording layer of each sample are shown below.

The recording layer was formed by spin coating while rotating the substrate at 500 rpm. As a coating solution, 1.5w
A t% methanol solution was used. Dye layer thickness after drying is 1
It was 300Å.

The dyes contained in the recording layer of each sample and the content ratio thereof, and the refractive index (n) and the extinction coefficient (k) of the recording layer are shown in Table 1 below.

n and k were determined by forming a solution containing the above dye on a measurement substrate to a dry film thickness of 600 ° to form a test recording layer, and measuring n and k of the test recording layer. This measurement is based on “Optics” (Kozo Ishiguro, Kyoritsu Zensho)
Performed according to the description on pages 168 to 178. In the measurement of the recording layer containing the dyes D1 and D2, methanol was used as a solvent, and a polycarbonate substrate was used as a measurement substrate.

The protective film was formed by spin-coating a coating composition containing the following radiation-curable compound and a photopolymerization sensitizer.

(Coating composition) Polyfunctional oligoester acrylate [oligoester acrylate (trifunctional or more) 30% by weight, trimethylpropane acrylate 70% by weight, trade name ARONIX M-80
30; manufactured by Toa Gosei Co., Ltd.] 100 parts by weight Photopolymerization sensitizer (the compound A: trade name IRGACURE907; manufactured by Nippon Ciba Geigy Co., Ltd.) 5 parts by weight
Irradiation for 5 seconds was carried out to crosslink and cure to obtain a cured film.

 The pencil hardness of this film was 2H.

For each of the obtained samples, a compact disk signal was recorded by a laser having a wavelength of 780 nm and 7 mW, and then reproduced by a commercially available compact disk player.

As a result, in Sample No. 1, the S / N ratio was high, and good reproduction could be performed.

Next, two sample pieces were obtained from the above sample No. 1.

After the protective film and the reflective layer were peeled off, the surface of the substrate was washed with methanol under different conditions for 2 minutes.

In this case, sample No. 1-1 has been subjected to weak washing with slight rocking in methanol, and sample No. 1-2 has been subjected to strong washing while applying ultrasonic waves.

After the cleaning, a 100-μm thick Au film was formed on the substrate surface by sputtering, and the surface state of both samples was imaged using a scanning tunneling microscope (STM) sold by Toyo Technica.

The STM image of Sample No. 1-1 is shown in Fig. 2, Sample No. 1
The STM image of -2 is as shown in FIG.

From FIGS. 2 and 3, it can be seen from FIG. 2 that sample No. 1-1 which underwent weak cleaning had a thick pit portion in the groove and sample No. 1-2 which underwent strong cleaning underwent the film within the groove. It can be confirmed that the thickness is almost constant.

Also, in order to check the film thickness in the groove more accurately,
A graph showing a surface state in a cross section along the groove was prepared. FIG. 4 shows a graph of sample No. 1-1, and FIG. 5 shows a graph of sample No. 1-2.

The vertical axis of the graph is the height in the substrate thickness direction from the reference plane, and the horizontal axis is the distance in the groove direction. In the drawing, arrow a indicates a pit portion, and arrow b indicates a position outside the pit portion.

As is apparent from FIG. 4, the pit portion of the sample No. 1-1 which has been weakly washed has a swelling as shown by the symbol a.

On the other hand, as apparent from FIG. 5, in the sample No. 1-2 which has been subjected to strong cleaning, the pit portion is slightly dented as shown by the symbol a.

From these facts, it can be considered that the portion of Sample No. 1-1 which looks prominent is a substance in which the dye is decomposed by receiving heat, that is, a decomposed substance layer containing a decomposed substance of the dye whose solubility is reduced.

Then, after the recording layer of the pit portion and the layer formed at the interface between the substrate and the substrate are peeled off by ultrasonic waves, an analysis is performed. As a result, it is found that a decomposition product is present and the substrate material is substantially contained. It was confirmed that it was not.

Further, a recording layer as shown in Table 2 below was formed using the dyes D1 and D2.

For each sample obtained, a wavelength of 780 n
m, recording a compact disc signal with a 7 mW laser, and then playing back with a commercially available compact disc player.As a result, in sample No. 1, good playback could be performed as described above. In the other samples No. 1-3, the dye layer had insufficient absorption and recording was impossible. In Nos. 1-4, the reflection was small and reproduction was impossible.

Next, the effect of the conjugate of the present invention was confirmed using Sample No. 1.

C1 k (780) = 0.03 C2 k (780) = 1.25 D + 2 · Q1 also quencher was used as a mixture Q1 below for comparison.

Q1 k (780) = 0 Q ⁻ 1 · N ⁺ (n−C ₄ H ₉ ) ₄ The composition of each sample is shown in Table 3 below.

Recording and reproduction were performed for each sample in the same manner as described above.

As a result, in the sample Nos. 2 and 3 of the present invention, the sample
A pit similar to No. 1 was formed.

In the unrecorded portion, a reflectance of 70% or more was obtained. The reflectance of the recorded portion of the 11T pulse of the CD signal was 40% or less of the unrecorded portion, so that good recording and reproduction could be performed. .

Further, each sample was irradiated with a 1.5 kw Xe lamp from a distance of 15 cm through the substrate, and the dye fastness after 20 hours was measured to evaluate the light fastness.

Dye Zan'yu rate (100-R) / (100 -R o) ( provided that, R _o and R, respectively, initial and reflectivity at 780nm after irradiation) was determined by.

In addition, 70 ° C, 10% relative humidity and 60 ° C, 90% relative humidity
%, Stored for 250 hours and 500 hours, respectively, and regenerated after storage to evaluate heat resistance and moisture resistance.

 The evaluation is as follows.

 ：: No error increase Δ: Some error increase ×: Error increase The results are shown in Table 3.

From the results shown in Table 3, it can be seen that the recording layer using the conjugate of the present invention has predetermined values of n, k and reflectance, and shows good recording / reproducing characteristics.

In addition, it can be seen that the light resistance, heat resistance, and moisture resistance show remarkably excellent characteristics as compared with the mixed system.

The measurement of Sample No. 2 of the present invention with a CD jitter meter MJM-631 manufactured by MEGURO revealed that the jitter was less than 100 ns and the jitter was small.

Example 2 Sample No. 1 was prepared in the same manner as in Example 1 except that the binder was changed to the following and the recording layer composition shown in Table 4 below was used.
Nos. 1 to 13 and Comparative Sample No. 21 were produced.

C3 (D ⁺ 3 · Q ^- 1) C6 (D ⁺ 8 · Q ^- 1) C21 (D ⁺ 3 · Q ^- 5) C11 (D ⁺ 26 · Q ^- 1) In comparison sample No. 21, Combination C'6
C'6 in which the quencher anion of C6 was changed as follows was used.

As a result, in Samples Nos. 11 to 13, pits exactly the same as those described above were formed, and good recording and reproduction without jitter could be performed.

On the other hand, in Sample No. 21, the reflectance was less than 60%, and reproduction could not be performed.

<Effects of the Invention> According to the present invention, since the reflectivity is high and the reflectivity at the pit portion is greatly reduced, good optical recording that can be reproduced according to the CD standard can be performed.

Then, an optical recording medium having a good pit shape, a high S / N ratio, and good recording / reproduction can be realized.

 At this time, the light resistance is extremely high and the reproduction deterioration is small.

 In addition, heat resistance, moisture resistance or water resistance are high.

[Brief description of the drawings]

FIG. 1 is a partial sectional view showing an optical recording medium of the present invention. 2 and 3 are photographs of the output image of the scanning tunneling microscope on the surface of the substrate after the recording layer of the optical recording medium of the present invention has been washed and removed, respectively. FIG. 4 and FIG. 5 are graphs each showing a surface state in a cross section along a groove of the substrate surface of the optical recording medium of the present invention. DESCRIPTION OF SYMBOLS 1 ... optical recording medium 2 ... substrate 21 ... land portion 23 ... groove 3 ... recording layer 4 ... reflection layer 5 ... protective film 6 ... pit portion 61 ... decomposition layer 63 ... … Void

────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masahiro Shinkai 1-13-1, Nihonbashi, Chuo-ku, Tokyo Inside TDK Corporation (56) References JP-A-60-163243 (JP, A) JP-A-60 JP-159087 (JP, A) JP-A-2-147286 (JP, A) JP-A-3-66042 (JP, A) JP-A-59-55794 (JP, A) JP-A-61-210539 (JP, A) JP-A-61-292237 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B41M 5/26

Claims (7)

(57) [Claims] A recording layer containing a dye is provided on a substrate, and a reflective layer is laminated on the recording layer in close contact with the recording layer. A pit portion is formed by irradiating recording light to the recording layer. An optical recording medium for performing reproduction by reproducing light, wherein the recording layer contains an ionic combination of a cyanine dye cation and an anion of a copper complex of bisphenylenedithiol. 2. The method according to claim 1, wherein when the reproducing light is irradiated from the substrate side, the reflectance of the unrecorded portion is 60% or more, and the reflectance of the recorded portion is 60% or less of the reflectance of the unrecorded portion. The optical recording medium according to the above. 3. The extinction coefficient k of the recording layer at the wavelength of the recording light and the reproducing light is 0.03 to 0.25, and the refractive index n of the recording layer at the wavelength of the recording light and the reproducing light is 1.8 to 4.0. Item 3. The optical recording medium according to Item 2. 4. The optical recording medium according to claim 1, wherein the wavelengths of the recording light and the reproducing light are from 600 to 900 nm. 5. A layer containing a decomposed substance of a recording layer material and substantially not containing a substrate material at an interface between the substrate and the recording layer in the pit portion. 5. The optical recording medium according to any one of 4. 6. The optical recording medium according to claim 5, wherein a void is formed in said pit portion. 7. The optical recording medium according to claim 1, wherein said optical recording medium contains two or more kinds of said ionic conjugates.