JPH0441060B2 - - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to optical recording media, particularly heat mode optical recording media. Prior Art Optical recording media have the characteristic that the recording medium does not deteriorate due to wear since the medium and the writing or reading head are not in contact with each other, and for this reason, research and development of various optical recording media are being carried out. Among such optical recording media, heat mode optical recording media are being actively developed because they do not require image processing in a darkroom. This heat mode optical recording medium is an optical recording medium that uses recording light as heat. One example is a heat mode optical recording medium that uses recording light such as a laser to melt or remove a part of the medium, which is called a pit. Some devices perform writing by forming small holes, record information using the pits, and read out information by detecting the pits with a readout light. Examples of such pit-forming media include media in which a recording layer made of a light-absorbing dye is formed on a substrate and pits are formed by melting the dye, and media in which pits are formed by melting the dye, and self-oxidizing media such as nitrocellulose. A recording layer containing a thermoplastic resin and a light-absorbing dye is formed, and a recording layer that forms pits by decomposing nitrocellulose, etc. There are also known methods that form pits by melting. Among the dyes, cyanine dyes exhibit extremely high reflectance and provide an extremely high readout S/N ratio. However, in media that use such cyanine dyes, during storage, the dyes may migrate and become mixed into the substrate, re-agglomerate, recrystallize, or bleed out, resulting in a decrease in writing sensitivity. In addition, there are disadvantages in that the read S/N ratio decreases. In particular, readout S/S due to high temperature storage after recording
The decrease in N ratio is extremely large. Purpose of the Invention The present invention was made in view of the above-mentioned circumstances, and its main purpose is to provide an optical recording medium using a cyanine dye that has improved storage stability, especially storage stability at high temperatures after recording. Our goal is to provide the following. These objects are achieved by the invention described below. That is, the first invention is an optical recording medium characterized in that a recording layer made of a resin having an acid anion group in its side chain and a cyanine cation bonded to the acid anion group is formed on a substrate. be. A second invention is characterized in that a recording layer comprising a resin having an acid anion group in its side chain and a cyanine cation bonded to the acid anion group, and a quencher is formed on a substrate. It is an optical recording medium. Specific Configuration of the Invention The specific configuration of the present invention will be described in detail below. The recording layer in the present invention is made of a resin in which cyanine cations are bonded to side chains. In this case, the resin to which the cyanine dye is bonded in the form of a cation is one in which one or more cations of the cyanine dye described below are bonded to the acid anion group of the resin side chain. In this case, the acid anion group on the resin side chain is
Various types are possible, especially carboxylic acid anion group (-COO ^- ), sulfonic acid anion group (-
SO ₃ ^- ), phosphate anion group, etc. are preferred, and among these, -COO ^- and -SO ₃ ^- are most preferred. Such a resin having an acid anion group is preferably obtained by, for example, treating a -COOH-containing resin or a -SO ₃ H-containing resin as described below with an alkali. (1) COOH-containing resin A homopolymer of acrylic acid or methacrylic acid or a copolymer with other monomers, or a copolymer of maleic anhydride, pyromellitic anhydride, trimellitic anhydride with vinyl acetate, etc. Combination etc. (2) SO ₃ H-containing resin polystyrene sulfonic acid, etc. The number of acid anion groups in the resin is approximately 0.05 to 2 per replacement unit. Further, there are no particular limitations on the molecular weight, etc. On the other hand, the dye is a cation of cyanine dye. Among the cyanine cations, those represented by the following formula are preferred. Formula [] Φ ⁺ -L=Ψ In the above formula [], Ψ and φ are indole rings, thiazole rings, oxazole rings, selenazole rings to which aromatic rings such as benzene rings, naphthalene rings, and phenanthrene rings may be fused. Represents a ring, imidazole ring, pyridine ring, etc. These Φ and Ψ may be the same or different, but are usually the same, and various substituents may be bonded to these rings. In addition,
In Φ, the nitrogen atom in the ring has a positive charge, and in Ψ, the nitrogen atom in the ring is neutral. The skeleton rings of these Φ and Ψ are preferably those represented by the following formulas [Φ] to [Φ]. In addition, in the following, the structure is shown in the form of Φ. In these various rings, the group R ₁ (R ₁ , R ₁ ') bonded to the nitrogen atom in the ring (two nitrogen atoms in the imidazole ring) is a substituted or unsubstituted alkyl group or aryl group. . A group R ₁ bonded to the nitrogen atom in such a ring,
There is no particular restriction on the number of carbon atoms in R ₁ ′. In addition, when this group further has a substituent, examples of the substituent include a sulfone group, a hydroxyl group,
It may be any of a carboxy group, an alkylcarbonyloxy group, an alkylamide group, an alkylsulfonamide group, an alkoxyoxy group, an alkylamino group, an alkylcarbamoyl group, an alkylsulfamoyl group, a halogen atom, and the like. Furthermore, when the rings Φ and Ψ are fused or non-fused indole rings (formulas [Φ] to [Φ]), two substituents R ₂ and R ₃ are preferably bonded to the 3-position. . 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. Among these, unsubstituted alkyl groups having 1 or 2 carbon atoms, particularly 1, are preferred. On the other hand, another substituent R ₄ may be bonded to a predetermined position in the ring represented by Φ and Ψ. Such substituents include alkyl groups,
It may be a variety of substituents such as an aryl group, a heterocyclic residue, a halogen atom, an alkoxy group, an alkylthio group, an alkyloxycarbonyl group, an alkylcarbonyloxy group, and the like. The number of these substituents (p, q, r, s, t) is usually 0 or 1 to 1.
It is said to be around 4. In addition, p, q, r, s, t are 2
In the above cases, the plurality of R ₄ may be different from each other. Furthermore, among these, the formula [Φ] ~ [Φ
It is preferable to have a fused or non-fused indole ring. This is because these materials have excellent coating properties and stability, exhibit extremely high reflectance, and have an extremely high readout S/N ratio. On the other hand, L represents a linking group for forming a mono-, di-, tri- or tetracarbocyanine dye, and is particularly preferably one of formulas [L] to [L]. Formula [L] Formula [L] Formula [L] Formula [L] Formula [L] Formula [L] Formula [L] Formula [L] Here, Y represents a hydrogen atom or a monovalent group. In this case, monovalent groups include lower alkyl groups such as methyl groups, lower alkoxy groups such as methoxy groups, dimethylamino groups, diphenylamino groups, methylphenylamino groups, morpholino groups, imidazolidine groups, and ethoxycarbonylpiperazine groups. Preferable examples include a di-substituted amino group such as, 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 addition, in these formulas [L] to [L],
Tricarbocyanine linking group, especially formula [L], [L
] is preferred. In addition, cyanine cation refers to cyanine dye,
According to the conventional method, I ^- , Br ^- , ClO ₄ ^- , BF ₄ ^- ,

【formula】

What is necessary is to cationize the salt that has been produced by [Formula] etc. Next, specific examples of cyanine cations used in the present invention will be given, but the present invention is not limited to these.

【table】

【table】

【table】

[Table] Such cyanisic cations can be easily synthesized according to known methods. That is, first, the corresponding Φ′−CH ₃ (Φ′ is the above Φ
represents the ring corresponding to . ), for example R ₁ I in excess
( _R1a alkyl group or aryl group) is heated to introduce _R1 into the nitrogen atom in Φ' to ^obtain Φ- _CH3I- . Next, this may be subjected to dehydration condensation using an unsaturated dialdehyde and an alkali catalyst. and,
When this is reacted with a resin having an acid anion group, it is bonded in the form of a cyanine cation. Such a cyanine cation is bonded to the acid anion group via the N ⁺ atom of Φ. To carry out such a bonding reaction, each of the above resins is treated in an alkali such as KOH-ethanol to obtain a resin having acid anion groups.
Then, this and the cyanine dye are mixed in a suitable solvent such as THF, cyclohexanone, dichloroethane,
This may be done by heating under reflux in MEK or the like and extracting with water or the like. In addition, cyanine cations are contained in the resin from 10 to
It is preferably contained in an amount of about 96 wt%, particularly about 50 to 96 wt%. The recording layer of the medium of the present invention is made of a resin to which such cyanine cations are bonded,
The recording layer may also contain other resins. At this time, coating properties are improved, and recording sensitivity, readout S/N ratio, etc. are improved. Examples of such resins include, for example, Japanese Patent Application No. 1983-
Those described in No. 15229 etc. are suitable. The resin is contained in an amount of about 50% or less by weight based on the resin to which cyanine cations are bonded. Preferably, such a recording layer further contains a quencher. This reduces reproduction deterioration and improves light resistance. Various types of quenchers can be used, but in particular, when cyanine cations are excited and singlet oxygen is generated, it undergoes electron transfer or energy transfer from the singlet oxygen and becomes excited, returning to the ground state by itself. In addition, it is preferably a singlet oxygen quencher that converts singlet oxygen into a triplet state. Various substances can be used as singlet oxygen quenchers, but transition metal chelate compounds are particularly preferred because they reduce regeneration deterioration and have good compatibility with cyanine cation-binding resins. is preferred. In this case, the central metal is preferably Ni, Co, Cu, Mn, etc., and the following compounds are particularly preferred. (1) Acetylacetonate chelate system Q1 Ni () acetylacetonate Q2 Cu () acetylacetonate Q3 Mn () acetylacetonate Q4 Co () acetylacetonate (2) Bisdithio-α-diketone system Here, R ⁽¹⁾ to ^{R (4)} represent a substituted or unsubstituted alkyl group or aryl group, and M is 2
Represents a valent transition metal atom. In this case, M has a single charge and may form a salt with a quaternary ammonium ion or the like. Q5 Ni()dithiobenzyl Q6 Ni()dithiobiacetyl (3) Bisphenyl dithiol type Here, R ⁽⁵⁾ and R ⁽⁶⁾ represent an alkyl group such as a methyl group, or a halogen atom such as Cl, and M represents a divalent transition metal atom such as Ni. Furthermore, a and b are each 0 or an integer of 4 or less. Further, M in the above structure may have a negative charge and form a salt with an anion, and further, other ligands may be bonded above and below M. As such, the following are commercially available. Q10 PA-1001 (product name manufactured by Mitsui Toatsu Fine Co., Ltd.) Q11 PA-1002 [Ni-bis(toluene dithiol) tetra(t-butyl) ammonium as above] Q12 PA-1003 (same as above) Q13 PA-1005 [Ni as above] -bis(dichlorobenzenedithiol)tetra(t-butyl)ammonium] Q14 PA-1006 [Ni-bis(trichlorobenzenedithiol)tetra(t-butyl)ammonium] Q15 Co-bis(benzene-1,2-dithiol) Tetrabutylammonium Q16 Co-bis(0-xylene-4,5-dithiol)tetra(t-butyl)ammonium Q17 Ni-bis(benzene-1,2-dithiol)tetrabutylammonium Q18 Ni-bis(0-xylene- 4,5-dithiol)tetrabutylammonium Q19 Ni-bis(5-chlorobenzene-1,2
-dithiol)tetrabutylammonium Q20 Ni-bis(3.4.5.6-tetramethylbenzene-1,2dithiol)tetrabutylammonium Q21 Ni-bis(3.4.5.6-tetrachlorobenzene-1,2dithiol)tetrabutylammonium(4) Dithiocarbamate chelate system Here, R ⁽⁷⁾ and R ⁽⁸⁾ represent an alkyl group. Moreover, M represents a divalent transition metal atom. Q22 Ni-bis(dibutyl dithiocarbamic acid) [Antigen NBC (manufactured by Sumitomo Chemical)] (5) Bisphenylthiol type Q23 Ni-bis(octyl phenyl) sulfide (6) Thiocatechol chelate type Here, M represents a divalent transition metal atom.
Further, M has a negative charge and may form a salt with an anion, and the benzene ring may have a substituent. Q24 Ni-bis(thiocatechol)tetrabutylammonium salt (7) Salicylaldehyde oxime type Here, R ⁽⁹⁾ and R ⁽¹⁰⁾ represent an alkyl group, and M represents a divalent transition metal atom. Q25 Ni()0-(N-isopropylformimidoyl)phenol Q26 Ni()0-(N-dodecylformimidoyl)phenol Q27 Co()0-(N-dodecylformimidoyl)phenol Q28 Co()0 -(N-dodecylformimidoyl)phenol Q29 Ni()2,2'-[ethylenebis(nitrilomethylidine)]-diphenol Q30 Co()2,2'-[ethylenebis(nitrilomethylidine)]-diphenol Q31 Ni()2,2′-[1.8-naphthylenebis]
Nitrilomethylidine)]-diphenol Q32 Ni()-(N-phenylformimidoyl)phenol Q33 Co()-(N-phenylformimidoyl)phenol Q34 Cu()-(N-phenylformimidoyl) ) Phenol Q35 Ni () Salicylaldehyde Phenylhydrazone Q36 Ni () Salicylaldehyde oxime (8) Thiobisphenolate chelate system Here, M is the same as above, R ⁽¹¹⁾ and
R ⁽¹²⁾ represents an alkyl group. Moreover, M has a negative charge and may form a salt with an anion. Q37 Ni()n-butylamino[2,2'-thiobis(4-tert-octyl)-phenolate][Cyasorb-UV-1084 (American Cyanamide Co., Ltd.)] Q38 Co()n-butylamino[ 2,2'-thiobis(4-tert-octyl)-phenolate] Q39 Ni()-2,2'-thiobis(4-tert-octyl)-phenolate (9) Phosphonous acid chelate system Here, M is the same as above, R ⁽¹³⁾ and
R ⁽¹⁴⁾ represents a substituent of an alkyl group or a hydroxyl group. In addition, other quenchers include the following. (10) Benzoate Q51 Existing chemical substance 3-3040 [Tinuvin-120
(manufactured by Ciba Geigy)] (11) Hindered amine Q52 Existing chemical substance 5-3732 [SANOLLS-770
(manufactured by Sankyo Pharmaceutical Co., Ltd.)] Such a quencher is synthesized according to a known method. The quencher is generally 0.05 to 12 mol per mol of cyanine cation in the resin.
In particular, it is contained in a range of about 0.1 to 1.2 moles. In addition, the maximum absorption wavelength of the quencher (λmax) _Q
is preferably greater than or equal to the maximum absorption wavelength (λmax) _D of the cyanine cation used. In this case, is (λmax) _Q − (λmax) _D 0?
It is preferably 350 nm or less. As a result, reproduction deterioration becomes extremely small. In order to form such a recording layer, it is generally necessary to apply it by coating according to a conventional method. The thickness of the recording layer is usually 0.03 to 10 μm.
It is considered to be a degree. In addition, such a recording layer may contain other polymers or oligomers, various plasticizers, surfactants, antistatic agents, lubricants, flame retardants, stabilizers, dispersants, crosslinking agents, etc. Good too. To deposit such a recording layer, on the substrate,
What is necessary is just to apply|coat using a predetermined solvent and to dry. Examples of solvents used for coating include ketones such as methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone, esters such as butyl acetate, ethyl acetate, carbitol acetate, and butyl carbitol acetate, and ethers such as methyl cellosolve and ethyl cellosolve. , aromatic systems such as toluene and xylene, halogenated alkyl systems such as dichloroethane, and alcohol systems. The material of the substrate on which such a recording layer is provided is not particularly limited, and may be any of various resins, glass, ceramics, metals, etc. Further, the shape thereof may be a tape, a disk, a drum, a belt, etc. depending on the intended use. Note that the base body usually has a tracking groove. Further, if necessary, it may have a base layer such as a reflective layer, a heat storage layer, a light absorption layer, etc. Further, as the material for the substrate, a substrate without grooves or grooves such as acrylic resin, epoxy resin, polycarbonate resin, highly heat-resistant polycarbonate resin, polysulfon resin, polyether sulfon, methylpentene polymer, etc. is suitable. These substrates can also be coated with a primer to improve solvent resistance, wettability, surface tension, thermal conductivity, etc. As the primer, for example, titanium-based, silane-based, or aluminum-based coupling agents, various photosensitive resins, etc. can be used. Further, on the recording layer, a reflective layer that functions as a back surface when a transparent substrate is used, various uppermost protective layers, a half mirror layer, etc. can be provided as necessary. The medium of the present invention may have the recording layer described above on one surface of such a substrate, or may have recording layers on both surfaces thereof. Also,
Two substrates with recording layers coated on one side are used, and the recording layers are placed facing each other with a predetermined gap between them, and they are sealed to prevent dust and scratches. You can also do it like this. Specific effects of the invention When the medium of the invention is running or rotating,
Recording light is irradiated in a pulsed manner. At this time, the resin itself melts due to heat generated by cyanine cations in the recording layer, forming pits. The pits thus formed are read out by detecting the reflected or transmitted light of the readout light, especially the reflected light, while the medium is running or rotating. In this case, recording and reading may be performed from the base side or from the recording layer side. It is also possible to erase the pits once formed in the recording layer with light or heat and rewrite. Note that the recording or reading light can be a semiconductor laser, He-Ne laser, Ar laser, He
-Cd laser etc. can be used. Specific Effects of the Invention According to the present invention, even if the medium is stored for a long time,
There is very little deterioration in writing sensitivity or S/N ratio. In particular, the deterioration of the S/N ratio when read after recording and storage at a high temperature is extremely small. Furthermore, since cyanine dye is used, the readout S/N ratio is also extremely high. In addition, according to the second invention, reproduction deterioration is significantly reduced and light resistance is extremely high. The present inventors conducted various experiments to confirm the effects of the present invention. An example is shown below. Experimental Example 1 The following resins A, B, and C were treated in KOH-EtOH to introduce acid anion groups. This and cyanine dye D9 iodide and D44 iodide were refluxed in THF-methanol for 2 hours, then poured into water and subjected to Soxhlet extraction with water to remove KI. As a result of elemental analysis, no halogen was detected in any of the products thus obtained, and it was confirmed that cyanine cations were bonded to acid anion groups. The amount of dye in the molecule was approximately 70 wt%. Each of these cyanine cation-binding resins was dissolved in dichloroethane, and a recording layer was formed on a polymethyl methacrylate substrate to a thickness of 0.07 μm. Separately, for comparison, a recording layer was formed in which the above cyanine dye and resin were blended at a weight ratio of 7:3. Note that the resins R1, R2, and R3 are as follows. R1 Polymethacrylic acid R2 Styrene/methacrylic acid (50/50 mol) copolymer R3 Poly-paratoluenesulfonic acid For each sample prepared in this way,
While rotating at 1800 rpm, a semiconductor laser (830 nm) was focused on a diameter of 1 μm from the back side of the substrate (output of the focusing section was 10 mW), and writing was performed with a pulse width of 100 nsec. After this, a 1mW semiconductor laser readout light is applied.
A 1 μsec width, 3 KHz pulse was irradiated from the back side of the substrate, and the reflected light was detected to measure the C/N ratio. Each sample was then incubated at 50°C and 90% relative humidity.
After storage for 1000 hours, the deterioration of the C/N ratio was measured. Table 1 shows the deterioration rate (%) of the C/N ratio after storage.

[Table] From the results shown in Table 1, the effects of the present invention are clear. Experimental Example 2 Sample No. 15 was obtained by adding Quencher Q14 in a weight ratio of 50% to the cyanine cation binding resin in Sample No. 1 of Experimental Example 1. Table 2 shows the reproduction deterioration rate (%) of the C/N ratio after samples No. 1 and No. 15 were continuously irradiated with readout light for 4 minutes.

[Table] From the results shown in Table 2, the effect of the second invention is clear.

Claims (1)

[Scope of Claims] 1. An optical recording medium comprising a recording layer formed of a resin having an acid anion group in its side chain and a cyanine cation bonded to the acid anion group on a substrate. 2. An optical recording medium comprising a recording layer formed on a substrate and comprising a resin having an acid anion group in its side chain and a cyanine cation bonded to the acid anion group, and a quencher.