JP4422050B2 - Trimethine compound and optical recording medium using the same - Google Patents

Description

  The present invention relates to an optical recording medium using a trimethine compound and capable of recording and reproducing at a higher density than before.

  A CD-R using an organic dye as a recording material is widely known as a medium capable of recording and reproducing data such as images, videos, and sounds. At present, with the increase in the amount of data to be handled, it is desired that an optical recording medium capable of recording and reproducing a large volume compared with a CD-R is desired. In particular, a DVD-R using an organic dye as a recording material is similar to a CD-R. Developed and commercialized as the next generation medium.

  The general structure of a DVD-R is as shown in FIG. 1, on a transparent resin substrate 1 having lands 7 and grooves 6, a recording layer 2, a reflective layer 3 and a protective layer (or adhesive layer) 4. , And in some cases, a substrate 5 is further provided thereon.

  In DVD-R, in order to perform high-density recording, the transmission wavelength of laser light is near 630 nm to 680 nm and shorter than in the case of CD-R. Examples of dyes for organic dye-based optical recording media for short wavelength applications include cyanine, azo, porphyrin dyes, indigo, dioxazine compounds, coumarin compounds, perylene compounds, naphtholactam compounds, triphenylmethane compounds, and subphthalocyanine compounds. Dibenzopyran compounds, dipyrromethene compounds and the like have been proposed.

Among these, trimethine compounds have been studied because they are excellent in optical properties and can cope with higher density.
The trimethine compound is composed of a cation having a trimethine structure and an anion which is a counter ion thereof. Examples of the anion which is a counter ion include halogen anions such as iodine, bromine and chlorine; perchlorate anion, chlorate anion, and thiocyanate. Inorganic anions such as acid anion, phosphorus hexafluoride anion, antimony hexafluoride anion, boron tetrafluoride anion; organic sulfonate anions such as benzenesulfonate anion, toluenesulfonate anion, trifluoromethanesulfonate anion, etc. These are disclosed in Japanese Patent Laid-Open Nos. 2001-209969, 2001-322354, 2000-108510, 2000-168233, 10-235999, 10 -337959 It has been described in an equal.

On the other hand, as seen in the increase in recording speed in CD-R, an optical recording medium that supports high-speed recording at 4 times, 8 times, or higher speed is also desired in DVD-R as compared with the standard recording speed. ing. However, the optical recording medium using the above-described trimethine compound still has room for improvement in recording sensitivity during high-speed recording.
JP 2001-209969 A JP 2001-322354 A JP 2000-108510 A JP 2000-168233 A JP-A-10-235999 JP 10-337959 A

  The object of the present inventor is to enable recording and reproduction with a short wavelength laser having a wavelength of 520 to 690 nm, excellent recording sensitivity not only at standard recording speed but also at high speed recording, and high density with good recording characteristics. It is to provide an optical recording medium.

As a result of diligent studies to solve the above problems, the present inventors have achieved excellent recording sensitivity not only at standard recording speed but also at high speed recording by using a trimethine compound having a specific structure. The inventors have found that a high-density optical recording medium having excellent recording characteristics can be obtained, and have completed the present invention.
That is, the present invention
[1] A trimethine compound represented by the following general formula (I):

(In the formula, R _{1 to} R ₂ each independently represents an alkyl group, an alkoxyalkyl group, a dialkylaminoalkyl group, an alkoxycarbonylalkyl group, a benzyl group, or a sulfonic acid alkyl group, provided that at least _one of R ₁ and R ₂ is present. Always represents an alkyl sulfonate group.)
[2] An optical recording medium having at least a recording layer containing an organic dye and a reflective layer on a substrate, wherein at least one trimethine compound described in [1] is used as the organic dye Medium,
It is about.

  By using the novel trimethine compound of the present invention as a recording layer, recording and reproduction can be performed with a short wavelength laser having a wavelength of 520 to 690 nm, and good recording characteristics not only at standard recording speed but also at high speed recording. It is possible to provide a high-density optical recording medium having

Hereinafter, the present invention will be described in detail.
The trimethine compound of the present invention is a trimethine compound represented by the following general formula (I).
Hereinafter, the trimethine compound represented by the following general formula (I) will be described more specifically as the trimethine compound in the present invention.

(In the formula, R _{1 to} R ₂ each independently represents an alkyl group, an alkoxyalkyl group, a dialkylaminoalkyl group, an alkoxycarbonylalkyl group, a benzyl group, or a sulfonic acid alkyl group, provided that at least _one of R ₁ and R ₂ is present. Always represents an alkyl sulfonate group.)

In the trimethine compound represented by the general formula (I), R _{1 to} R ₂ each independently represents an alkyl group, an alkoxyalkyl group, a dialkylaminoalkyl group, an alkoxycarbonylalkyl group, a benzyl group, or an alkyl sulfonate group. However, at least _one of R ₁ and R ₂ always represents an alkyl sulfonate group.

Specific examples of R ₁ and R _{2 in} the trimethine compound of the general formula (I) include, for example, methyl group, ethyl group, n-propyl group, iso-propyl group, n-butyl group, iso-butyl group, sec- Butyl group, t-butyl group, n-pentyl group, 2-methylbutyl group, 1-methylbutyl group, neo-pentyl group, 1,2-dimethylpropyl group, cyclo-pentyl group, n-hexyl group, 4-methylpentyl Group, 3-methylpentyl group, 2-methylpentyl group, 1-methylpentyl group, 3,3-dimethylbutyl group, 2,3-dimethylbutyl group, 1,3-dimethylbutyl group, 2,2-dimethylbutyl Group, 1,2-dimethylbutyl group, 1,1-dimethylbutyl group, 3-ethylbutyl group, 2-ethylbutyl group, 1-ethylbutyl group, 1,2,2-trimethylbutyl group 1,1,2-trimethylbutyl group, 1-ethyl-2-methylpropyl group, cyclo-hexyl group, n-heptyl group, 2-methylhexyl group, 3-methylhexyl group, 4-methylhexyl group, 5 -Methylhexyl group, 2,4-dimethylpentyl group, n-octyl group, 2-ethylhexyl group, 2,5-dimethylhexyl group, 2,5,5-triethylpentyl group, 2,4-dimethylhexyl group, 2 , 2,4-trimethylpentyl group, n-nonyl group, 3,5,5-trimethylhexyl group, n-decyl group, 4-ethyloctyl group, 4-ethyl-4,5-dimethylhexyl group, n-undecyl Group, n-dodecyl group, 1,3,5,7-tetramethyloctyl group, 4-butyloctyl group, 6,6-diethyloctyl group, n-tridecyl group, 6-methyl-4 Butyloctyl group, 6,6-diethyloctyl group, n-tetradecyl group, n-pentadecyl group, 3,5-dimethylheptyl group, 2,6-dimethylheptyl group, 2,4-dimethylheptyl group, 2,2, C1-C20 straight chain, branched or cyclic such as 5,5-tetramethylhexyl group, 1-cyclo-pentyl-2,2-dimethylpropyl group, 1-cyclo-hexyl-2,2-dimethylpropyl group An alkyl group of
Chloromethyl group, dichloromethyl group, fluoromethyl group, trifluoromethyl group, 2,2,2-trifluoroethyl group, pentafluoroethyl group, heptafluoroisopropyl group, heptafluoro-n-propyl group, 2,2, 3,3,3-pentafluoropropyl group, nonafluoro-n-butyl group, nonafluoro-tert-butyl group, 2,2,3,3,4,4,4-heptafluorobutyl group, 2,2,3, 4,4,4-hexafluorobutyl group, perfluoroisopentyl group, 2,2,3,3,4,4,5,5-octafluoropentyl group, heptafluoro-sec-pentyl group, perfluorohexyl Groups, perfluoroisohexyl groups, perfluoroheptyl groups, perfluorooctyl groups, perfluorocyclohexyl groups, 4-trifluoromethylcyclohexyl groups and the like halogenoalkyl groups;
Alkoxyalkyl groups such as methoxyethyl group, ethoxyethyl group, iso-propyloxyethyl group, 3-methoxypropyl group, 2-methoxybutyl group;
2-dimethylaminoethyl group, 3-dimethylaminopropyl group, 4-dimethylaminobutyl group, 2-diethylaminoethyl group, 3-diethylaminopropyl group, 4-diethylaminobutyl group, 2-di-n-propylaminoethyl group, 3-di-n-propylaminopropyl group, 4-di-n-propylaminobutyl group, 2-di-n-butylaminoethyl group, 3-di-n-butylaminopropyl group, 4-di-n- A dialkylaminoalkyl group having 4 to 12 carbon atoms such as a butylaminobutyl group;
An alkoxycarbonylalkyl group having 3 to 7 carbon atoms such as a methoxycarbonylmethyl group, an ethoxycarbonylmethyl group, an n-propoxycarbonylmethyl group, an isopropoxycarbonylethyl group, a phenoxycarbonyl group;
Sulfonic acid alkyl groups such as propyl sulfonate group, butyl sulfonate group, pentyl sulfonate group, hexyl sulfonate group, heptyl sulfonate group, octyl sulfonate group, etc .;
Is mentioned.

  Although the preferable specific example of the trimethine compound of general formula (I) of this invention is shown below, the range of the compound is not limited to these.

  The method for producing the trimethine compound of the present invention is not particularly limited. For example, the indolenium compound represented by the general formula (II) and the compound represented by the following general formula (III) can be dehydrated in the presence of a fatty acid salt. A trimethine compound of the following general formula (I) is obtained by condensation using an organic acid.

(R ₁ and R _{2 in} formulas (II) and (III) have the same meaning as in formula (I).)

<Trimethine compound represented by the following general formula (I)>

(In the formula, R _{1 to} R ₂ each independently represents an alkyl group, an alkoxyalkyl group, a dialkylaminoalkyl group, an alkoxycarbonylalkyl group, a benzyl group, or a sulfonic acid alkyl group, provided that at least _one of R ₁ and R ₂ is present. Always represents an alkyl sulfonate group.)

In the above condensation reaction, examples of the fatty acid salt include sodium acetate, potassium acetate, potassium acetate, sodium propionate, and potassium propionate.
Such a fatty acid salt is usually used in an amount of about 0.1 to 5 mol, preferably about 0.5 to 2 mol, per mol of the compound represented by formula (II).
Examples of the dehydrating organic acid include acetic anhydride, propionic anhydride, butyric anhydride, and γ-butyllactone.
Such dehydrating organic acid is usually used in an amount of about 10 to 100 mol, preferably about 20 to 50 mol, per 1 mol of the compound represented by the general formula (III).

The proportion of the compound represented by the general formula (II) and the compound represented by the general formula (III) is usually about 1 to 1.5 mol, preferably 1 to 1.1 mol of the latter with respect to 1 mol of the former. Use about mol.
The above reaction usually proceeds suitably at about 10 to 150 ° C., preferably at room temperature to 100 ° C., and is generally completed in about several minutes to 3 hours.

  After the reaction, for example, water, methanol, ethanol, n-propanol, iso-propanol, n-butanol or other poor solvent is injected, or water, methanol, ethanol, n-propanol, iso-propanol, n-butanol, etc. The target product can be easily isolated from the reaction mixture by discharging to a poor solvent.

  A specific configuration of the optical recording medium in the present invention will be described below.

  The optical recording medium refers to both a reproduction-only optical reproduction medium in which information is recorded in advance and an optical recording medium in which information can be recorded and reproduced. However, here, as an example, an optical recording medium that can record and reproduce the latter information, particularly an optical recording medium having a recording layer and a reflective layer on a substrate will be described. The optical recording medium of the present invention has a bonding structure as shown in FIG. That is, the recording layer 2, the reflective layer 3, and the protective layer (or adhesive layer) 4 are formed on the transparent resin substrate 1 having the lands 7 and the grooves 6, and in some cases, the substrate 5 is further formed thereon. Provided. However, another layer may be provided below or on the recording layer 2, and another layer may be provided on the reflective layer 3. Here, in order to be compatible with an existing DVD, a disk-shaped substrate having a thickness of 0.6 mm, an outer diameter of 120 mmΦ, and an inner diameter of 15 mmφ is bonded.

  Next, the required characteristics of each layer constituting the recording medium of the present invention and its constituent materials will be described.

1) Substrate The material of the substrate may be basically transparent at the wavelengths of recording light and reproducing light. For example, an acrylic resin such as polycarbonate resin, vinyl chloride resin or polymethyl methacrylate, a polymer material such as polystyrene resin or epoxy resin, or an inorganic material such as glass is used. These substrate materials are formed into a disk shape by an injection molding method or the like. The substrate surface may have pregrooves and prepits representing recording positions, and prepits for partial reproduction-only information. These pregrooves and prepits are usually transferred and applied from a stamper master during substrate production by an injection molding method or the like. Moreover, you may produce by the laser cutting method (prelight) and 2P (Photo Polymer) method.

  The groove pitch of the substrate is 0.7 μm to 1.0 μm, and the groove depth is 100 nm to 200 nm, preferably 140 nm to 185 nm. The groove width is 0.25 μm to 0.40 μm, preferably 0.30 μm to 0.35 μm. When the groove depth is less than 100 nm, it tends to be difficult to obtain a push-pull signal amplitude for tracking. When the groove depth exceeds 200 nm, the transfer process at the time of injection molding is not practical for production. Further, when the groove width is less than 0.25 μm, the crosstalk tends to deteriorate, and when it exceeds 0.4 μm, the transfer process at the time of injection molding is not practical in production. These groove shapes are obtained from a diffracted light analysis by He-Cd laser irradiation or a profile such as AFM.

2) Recording Layer In the present invention, a recording layer is provided on a substrate, and the recording layer of the present invention contains a trimethine compound represented by the general formula (I) having a λmax in the vicinity of 450 nm to 630 nm. Among them, an appropriate optical constant for the recording and reproducing laser wavelength selected from 520 nm to 690 nm (the optical constant is expressed by a complex refractive index (n + ki). N and k in the formula are a real part n and an imaginary part. It is necessary to have a coefficient corresponding to k, where n is a refractive index and k is an extinction coefficient.

  In general, organic dyes are characterized in that the refractive index n and the extinction coefficient k greatly change with respect to the wavelength λ. When n is less than 1.8, the reflectivity and signal modulation necessary for accurate signal reading cannot be obtained, and even if k exceeds 0.40, the reflectivity decreases and a good reproduction signal is obtained. Not only is the signal easily changed by the reproduction light, but it is not suitable for practical use. In consideration of this feature, an organic dye having a preferable optical constant at a target laser wavelength is selected and a recording layer is formed, so that a medium having high reflectance and high sensitivity can be obtained. .

  The trimethine compound represented by the general formula (I) used in the present invention has a higher extinction coefficient than a normal organic dye, and an absorption wavelength range can be arbitrarily selected by selecting a substituent. Required for the recording layer (n is 1.8 or more and k is 0.04 to 0.40, preferably n is 2.0 or more and k is 0.04 to 0.4. 20) is satisfied.

  In addition, the trimethine compound represented by the general formula (I) has a nitro group and an alkyl sulfonate group substituted at specific positions at the same time, so that decomposition due to heat generated during recording laser irradiation is moderately accelerated, and high-speed recording is performed. Even at times, the sensitivity is excellent, and deterioration of pit jitter due to thermal interference can be suppressed sufficiently low. Thereby, it is possible to obtain an optical recording medium having excellent recording characteristics and excellent recording characteristics not only at the standard recording speed but also at high speed recording.

  In the recording layer of the present invention, one kind of trimethine compound represented by the general formula (I) is preferably used as the recording layer. However, in order to improve the recording characteristics, two or more kinds may be mixed, You may mix and use pigments other than a trimethine compound.

  The mixing ratio of the trimethine compound in the case of using a mixture of two or more trimethine compounds represented by the general formula (I) is not particularly limited. For the above reasons, the optical constant n is 1.8 or more, preferably 2 It is preferable that the mixing be performed so that the k is 0.04 or more and k is 0.04 to 0.40, preferably 0.04 to 0.20.

  Examples of the dye other than the trimethine compound of the present invention that may be used as a mixture include dyes having an absorption maximum at a wavelength of 450 nm to 630 nm and a large refractive index at 520 nm to 690 nm. Specifically, azo dyes, squarylium dyes, naphthoquinone dyes, anthraquinone dyes, porphyrin dyes, azaporphyrin dyes, tetrapyraporphyrazine dyes, indophenol dyes, pyrylium dyes, thiopyrylium dyes, Azurenium dyes, triphenylmethane dyes, xanthene dyes, indanthrene dyes, indigo dyes, thioindigo dyes, merocyanine dyes, thiazine dyes, acridine dyes, oxazine dyes, etc. It may be mixed. The mixing ratio of these pigments is about 0.1 to 30%.

  Further, when the k for the recording and reproducing laser wavelength selected from 520 nm to 690 nm of the trimethine compound represented by the general formula (I) is small, the wavelength is 600 nm to 900 nm for improving recording characteristics and the like. May be mixed with a light-absorbing compound having an absorption maximum. Specifically, azo dyes, squarylium dyes, naphthoquinone dyes, anthraquinone dyes, porphyrin dyes, azaporphyrin dyes, tetrapyraporphyrazine dyes, indophenol dyes, pyrylium dyes, thiopyrylium dyes, azurenium Dyes, triphenylmethane dyes, xanthene dyes, indanthrene dyes, indigo dyes, thioindigo dyes, merocyanine dyes, thiazine dyes, acridine dyes, oxazine dyes, phthalocyanine dyes, naphthalocyanine dyes Or a mixture of a plurality of pigments. The mixing ratio of these pigments is about 0.1 to 30%.

  When forming the recording layer, if necessary, a quencher, a dye decomposition accelerator, an ultraviolet absorber, an adhesive, an endothermic decomposition compound, or the like is mixed, or a compound having such an effect is represented by the general formula ( It can also be introduced as a substituent of the trimethine compound represented by I).

  Specific examples of quenchers include acetylacetonate compounds, bisdithio-α-diketone compounds, bisdithiol compounds such as bisphenyldithiol compounds, thiocatechol compounds, salicylaldehyde oxime compounds, thiobisphenolate compounds Metal complexes such as compounds are preferred. Amine compounds are also suitable.

  Examples of the thermal decomposition accelerator include metal compounds such as metal anti-knock agents, metallocene compounds, and acetylacetonate metal complexes.

  Furthermore, a binder, a leveling agent, an antifoaming agent, etc. can also be used together as needed. Preferred binders include polyvinyl alcohol, polyvinyl pyrrolidone, nitrocellulose, cellulose acetate, ketone resin, acrylic resin, polystyrene resin, urethane resin, polyvinyl butyral, polycarbonate, polyolefin and the like.

  When the recording layer is formed on the substrate, a layer made of an inorganic substance or a polymer may be provided on the substrate in order to improve the solvent resistance, reflectance, recording sensitivity, etc. of the substrate.

  Examples of the method for providing the recording layer include spin coating, spraying, casting, dipping, and other coating methods, sputtering, chemical vapor deposition, and vacuum vapor deposition. The spin coating method is simple and preferable.

  When a coating method such as spin coating is used, a coating solution in which the trimethine compound represented by the general formula (I) is dissolved or dispersed in a solvent so as to be 1 to 40% by weight, preferably 3 to 30% by weight. In this case, it is preferable to select a solvent that does not damage the substrate. Specific examples include alcohols (including alkoxy alcohols such as keto alcohols and ethylene glycol monoalkyl ethers), ketones, esters, ethers, aromatics, and alkyl halides.

  Of these, the alcohol type is particularly preferable. Among alcohols, alkoxy alcohols and keto alcohols are preferable. In the alkoxy alcohol system, the alkoxy moiety preferably has 1 to 4 carbon atoms, the alcohol moiety preferably has 1 to 5 carbon atoms, more preferably 2 to 5 carbon atoms, and the total number of carbon atoms is 3 It is preferably ˜7. Specifically, ethylene glycol monoalkyl ether (methyl cellosolve), ethylene glycol monoethyl ether (also called ethyl cellosolve, ethoxyethanol), butyl cellosolve, ethylene glycol monoalkyl ether (cellosolve) such as 2-isopropoxy-1-ethanol And 1-methoxy-2-propanol, 1-methoxy-2-butanol, 3-methoxy-1-butanol, 4-methoxy-1-butanol, 1-ethoxy-2-propanol and the like. Examples of keto alcohols include diacetone alcohol. Furthermore, fluorinated alcohols such as 2,2,3,3-tetrafluoropropanol can also be used.

  Moreover, you may make a coating liquid contain a binder, a dispersing agent, a stabilizer, etc. suitably.

  If necessary, the dye of the recording layer can be dispersed in a polymer thin film or the like.

  In addition, when a solvent that does not damage the substrate cannot be selected, a sputtering method, a chemical vapor deposition method, a vacuum vapor deposition method, or the like is effective.

  The film thickness of the dye layer is not particularly limited, but the film thickness on the guide grooves (grooves) of the substrate is preferably in the range of 30 nm to 150 nm, and the film thickness between the guide grooves (lands) of the substrate is 10 nm to A range of 80 nm is preferred. If the thickness of the groove exceeds 150 nm, the shortest pit is crushed, which is not preferable. On the other hand, when the thickness is smaller than 30 nm, good recording sensitivity and recording modulation degree cannot be obtained. It is particularly preferable that the film thickness on the land is as thin as possible. The film thickness of these recording layers can be controlled by using a mixture of a plurality of the above organic solvents.

3) Reflective layer A reflective layer having a thickness of preferably 50 nm to 300 nm is formed on the recording layer. As a material for the reflective layer, a material having a sufficiently high reflectance at the wavelength of the reproduction light, for example, Au, Al, Ag, Cu, Ti, Cr, Ni, Pt, Ta, and Pd metal may be used alone or as an alloy. Is possible. Among these, Au, Al, and Ag have high reflectivity and are suitable as the material for the reflective layer. Other than this, the following may be included. For example, Mg, Se, Hf, V, Nb, Ru, W, Mn, Re, Fe, Co, Rh, Ir, Zn, Cd, Ga, In, Si, Ge, Te, Pb, Po, Sn, Bi, etc. And metals and metalloids. In addition, a material containing Au as a main component is preferable because a reflective layer having a high reflectance can be easily obtained. Here, the main component means that the content is 50% or more. It is also possible to form a multilayer film by alternately stacking a low refractive index thin film and a high refractive index thin film using a material other than metal, and use it as a reflective layer.

  Examples of the method for forming the reflective layer include sputtering, ion plating, chemical vapor deposition, and vacuum vapor deposition. In addition, a known inorganic or organic intermediate layer or adhesive layer may be provided on the substrate or below the reflective layer in order to improve reflectivity, recording characteristics, and adhesion.

  The reflectance is not particularly limited as long as the signal can be reproduced, but is preferably 30% or more and less than 65%, and more preferably 45% or more and less than 60%.

4) Protective layer The material of the protective layer on the reflective layer is not particularly limited as long as it protects the reflective layer from external force. Examples of the organic substance include a thermoplastic resin, a thermosetting resin, an electron beam curable resin, and an ultraviolet curable resin. Examples of inorganic substances include SiO ₂ , Si ₃ N ₄ , MgF ₂ , SnO _{2 and the} like. A thermoplastic resin, a thermosetting resin, etc. can be formed by dissolving in an appropriate solvent, applying a coating solution, and drying. The ultraviolet curable resin can be formed by preparing a coating solution as it is or by dissolving in an appropriate solvent, and then applying the coating solution and curing it by irradiating with ultraviolet rays. As the ultraviolet curable resin, for example, acrylate resins such as urethane acrylate, epoxy acrylate, and polyester acrylate can be used. These materials may be used alone or in combination, and may be used not only as a single layer but also as a multilayer film.

  As a method for forming the protective layer, a coating method such as a spin coating method and a casting method, a sputtering method, a chemical vapor deposition method, and the like are used as in the recording layer. Among these, a spin coating method is preferable.

  The thickness of the protective layer is generally in the range of 0.1 μm to 100 μm, but in the present invention, it is 3 μm to 30 μm, more preferably 5 μm to 20 μm.

  A label or the like can be further printed on the protective layer. Alternatively, a protective sheet or substrate may be bonded to the reflective layer surface, or two optical recording media may be bonded to each other with the reflective layer surfaces facing each other. Further, an ultraviolet curable resin, an inorganic thin film, or the like may be formed on the mirror surface side of the substrate in order to protect the surface and prevent adhesion of dust and the like.

  The laser having a wavelength of 520 nm to 690 nm as used in the present invention is not particularly limited. Examples thereof include a semiconductor laser and a harmonic conversion YAG laser having a wavelength of 532 nm. In the present invention, high-density recording and reproduction are possible at one wavelength or a plurality of wavelengths selected from these.

  Examples of the present invention will be shown below, but the present invention is not limited thereto.

Preparation of Trimethine Compound (Specific Example Compound 4) In a nitrogen atmosphere, 7.2 g of a compound represented by the following structural formula (A) at 25 ° C. in 45.0 g of acetic anhydride, a compound represented by the following structural formula (B) 9. 6 g was reacted at 50 to 55 ° C. for 1.5 hours. After adding 45 ml of methanol and stirring at 30 ° C. for 30 minutes, the mixture was stirred at 60 to 65 ° C. for 1 hour, and the pressure was gradually reduced to distill off the solvent. 90 ml of methanol was added to 25 ° C., and the reaction was carried out at the same temperature for 1 hour. After adding 90 ml of water and stirring for 30 minutes, the crystals were collected by filtration, washed with water, dried and then recrystallized in methanol to obtain 6.1 g of a compound represented by the following structural formula (C).

The compound thus obtained showed an absorption maximum at 577.0 nm in a methanol solution, and the gram extinction coefficient was 1.30 × 10 ⁵ ml / g · cm.

  MS (m / e): 585

  The trimethine compound 7 listed in Table 2 was added to tetrafluoropropanol on an injection-molded polycarbonate substrate having a spiral groove (pitch = 0.74 um, depth = 165 nm, width = 0.33 um) having a thickness of 0.6 mm and a diameter of 120 mmΦ. (20 g / l), and the film was formed by spin coating so that the film thickness on the grooves was approximately 80 nm and the film thickness between the grooves was 20 nm. After drying at 80 ° C. for 2 hours, an AgPdCu reflective film is formed with a film thickness of 80 nm using a sputtering apparatus (CDI-900) manufactured by Balzers, and on this reflective layer, UV curable resin: SD17 (Dainippon Ink) After being coated and UV cured, a 0.6 mm thick polycarbonate substrate was laminated thereon as described above, and an optical recording medium was produced by bonding with UV light using a KZ8681 radical polymerization adhesive manufactured by JSR.

  Disc tester DDU1000 manufactured by Pulstec Industrial Co., Ltd .: wavelength = 661 nm, NA = 0.60, linear velocity = 3.5 m / s (DVD-R standard recording velocity), linear velocity = 42 m / second. Each DVDR-compatible EFM + signal was recorded at s (12 times the DVD-R standard recording speed). Recording conditions were recorded by adjusting the pulse conditions described in the DVD-R standard (ver. 2.0) at high speeds of 1 × speed and 12 × speed, respectively, so as to be optimal for each pit. Jitter measurement was performed on these recording parts at a standard DVD speed. In the DVDR medium shown in this example, high sensitivity and a good jitter value could be confirmed at both 1 × speed and 12 × speed.

[Examples 3 to 14]
An optical recording medium was produced in the same manner as in Example 2 except that the trimethine compounds described in Table 2 were used as appropriate.

  When these optical recording media were evaluated in the same manner as in Example 2, high sensitivity and good jitter values could be confirmed at both 1 × speed and 12 × speed.

[Comparative Example 1]
An optical recording medium was prepared in the same manner as in Example 2 using the following trimethine compound (a), and the same evaluation was performed. Although 1 × speed recording was possible, the sensitivity was poor and a recording power of 14.0 mW was required. Further, in 12 × speed recording, sensitivity was insufficient and good recording could not be performed.

Table 2 shows the 1 × speed and 12 × speed sensitivities and jitter results measured in Examples 2 to 14 and Comparative Example 1. In the DVD-R medium shown in this example, good sensitivity and jitter were confirmed at both 1 × speed and 12 × speed.
<Table-2>

  By using the trimethine compound of the present invention as a recording layer, it is possible to provide a write-once type optical recording medium that can be recorded and reproduced with a laser of 520 to 690 nm and is suitable for high-speed recording.

It is a cross-sectional structure diagram showing a conventional optical recording medium and a layer structure of the present invention.

Explanation of symbols

1 Substrate 2 Recording layer 3 Reflective layer 4 Adhesive layer 5 Substrate

Claims (2)

A trimethine compound represented by the following general formula (I).
(In the formula, R _{1 to} R ₂ each independently represents an alkyl group, an alkoxyalkyl group, a dialkylaminoalkyl group, an alkoxycarbonylalkyl group, a benzyl group, or a sulfonic acid alkyl group, provided that at least _one of R ₁ and R ₂ is present. Always represents an alkyl sulfonate group.)   An optical recording medium having at least a recording layer containing an organic dye and a reflective layer on a substrate, wherein at least one trimethine compound according to claim 1 is used as the organic dye.