Patent Application
20090018318
The present invention relates to the use of Basic Yellow dyes as dye component for optical data recording media. In a preferred aspect the present invention relates to Basic Yellow dyes together with a metalazo complex dye as dye components for optical data recording media. In a more preferred aspect, the invention relates to a write once read many (WORM) type optical data recording medium capable of recording and reproducing information with radiation of blue laser of preferably 405 nm, which employs a Basic Yellow dye together with a metalazo complex dye and a further recording dye in the optical layer.
Optical data recording media (optical discs) capable of recording information only once with a laser beam are conventionally known. Such optical discs are also referred to as write-once CDs (CD-Rs) and in a typical structure thereof, a recording layer (optical layer) comprising an organic compound such as an organic dye, a light reflective layer comprising a metal such as gold, and a protective layer made of a resin, are laminated successively, in this order, on a transparent disc-shaped substrate. Information is recorded to a CD-R by irradiating a near-infrared laser beam (usually a laser beam with a wavelength near 780 nm) thereon, in which the irradiated area of the recording layer absorbs the beam. The temperature of the irradiated area increases, causing the optical characteristics of the area to undergo physical or chemical changes (e.g. the formation of pits) and the information is thus recorded.
With regards to reading (reproduction) of information, this is also conducted by irradiating a laser beam with a wavelength identical to that of the recording laser beam. Information reproduction from the CD-R is conducted by detecting the difference of the reflectivity in the recording area between the areas where the optical characteristics have been changed (recorded area) and not changed (unrecorded area).
In recent years, there has been a demand for optical information recording media possessing higher recording density. To meet this demand for greater recording capacity, an optical disc referred to as a write-once digital versatile disc (DVD-R) has been proposed (for example, see Nikkei New Media special volume “DVD”, published in 1995). The DVD-R is configured by appending two discs, each usually formed by laminating a recording layer containing an organic dye, a light reflective layer and a protective layer, in this order, on a transparent disc-shaped substrate in which guide grooves (pre-grooves) for laser beam tracking are formed. The pre-grooves occupy a narrow area of the DVD-R, specifically one-half or less of the DVD-R (0.74-0.8 μm) and the recording layers of the disc are formed towards the inner portion of the disc. The DVD-R can also be configured so that a disc-shaped protective substrate is included with the recording layer formed towards the inner portion of the disc. Information is recorded to and reproduced from the DVD-R by irradiating a visible laser beam thereon (usually a laser beam with a wavelength of about 630 nm to 680 nm), and thus, recording at a density higher than that of a CD-R is possible.
However, considering factors such as the recent spread of networks (e.g. Internet) and the emergence of high definition television (HDTV) broadcasting, cheap and convenient recording media, capable of recording image information at even larger capacity, are required. While DVD-Rs sufficiently serve as high-capacity recording media at present, demand for larger capacity and higher density has increased.
Blu-ray® discs (Blu-ray® disc is a standard developed by Hitachi Ltd., LG Electronics Inc., Matsushita Electric Industrial Co. Ltd., Pioneer Corporation, Royal Philips Electronics, Samsung Electronics Co. Ltd., Sharp Corporation, Sony Corporation, Thomson Multimedia) or HD-DVD discs (a standard developed by Toshiba and NEC) are going to be the next milestone in optical recording technology. Its new specification increases the data storage up to 27 Gigabytes per recording layer for a 12 cm diameter disc. By adopting a blue diode laser with a wavelength of 405 nm (GaN or SHG laser diodes), the pit size and track interval can be further reduced, again increasing the storage capacity by an order of magnitude.
Here also organic dyes have attracted considerable attentions and some solutions have been already proposed in the field of short wavelength diode-laser optical storage. Examples of such media include JP-A Nos. 4-74690, 7-304256, 7-304257, 8-127174, 11-53758, 11-334204, 11-334205, 11-334206, 11-334207, 2000-43423, 2000-108513, 2000-113504, 2000-149320, 2000-158818, and 2000-228028. In the methods described above, information is recorded and reproduced by irradiating a blue laser beam (wavelength: 430 nm, 488 nm) or blue-green laser beam (wavelength: 515 nm) onto an optical disc having a recording layer containing porphyrine compounds, azo dyes, metalazo dyes, quinophthalone dyes, trimethinecyanine dyes, dicyanovinylphenyl skeleton dyes, coumarin compounds and naphthalocyanine compounds.
Unfortunately, the optical discs described in the above patent publications can not obtain the sensitivity required for practical use when recording information by irradiation of a short wavelength laser beam at a wavelength of 380 to 500 nm. Particularly, in the optical discs described in the above patent publications, the recording characteristics actually deteriorated when irradiating a laser beam with a wavelength of 380 to 500 nm. More specifically, read-out stability requirements (i.e. 1 000 000 cycles at 0.4 mW) are generally not reached with systems as described above.
It is an object of the present invention to provide an optical data recording medium that is capable of recording at high density with high recording characteristics and with improved read-out stabilities. Another objective of the invention is to provide an optical information recording method that can provide stable recording and reproducing characteristics, as well as an optical information recording medium on which information has been recorded by the recording method.
It has been found, that specific metalazo complex dyes are useful as dye components in optical layers for improving recording properties of cyanine dyes. These products show very interesting recording characteristics and good overall performances when applied in recording media.
Surprisingly it has now been found, that anionic metalazo complex dyes together with cationic Basic Yellow dyes significantly improve the recording characteristics in particular readout stability, and overall performances when applied as dye components in optical data recording media.
The invention therefore relates to Basic Yellow dyes as dye component for use in an optical layer and to the use of said optical layers for optical data recording media. Particularly, the invention relates to a heat mode type optical data recording medium, which employs a Basic Yellow dye together with a metalazo complex dye in the optical layer. More particularly, the invention relates to a write once read many (WORM) type optical data recording medium capable of recording and reproducing information with radiation of blue laser of preferably 405 nm, which employs a Basic Yellow dye together with a metalazo complex dye and a further recording dye in the optical layer.
The present invention is directed to an optical layer for an optical data recording medium comprising at least one Basic Yellow dye together with at least one metalazo complex dye as dye components.
Halogen represents F, Cl, Br or J, preferably F, Cl or Br, more preferably F or Cl, even more preferably Cl, in the following, if not otherwise stated.
In particular, the present invention is directed to an optical layer for an optical data recording medium comprising at least one Basic Yellow cationic dye together with at least one anionic metalazo complex dye as counter ion, represented by the general formula (I) or (II)
wherein
Preferably the Basic Yellow cationic dye component is selected from
Preferably the present invention is directed to an optical layer for an optical data recording medium comprising at least one Basic Yellow cationic dye together with at least one anionic metalazo complex dye as counterion, represented by the general formula (II) wherein
wherein
Most preferred anionic metalazo complex dyes as counterions of the dye compound of formula (II) are selected from the group consisting of the compounds of formula (A) to (F).
An optical layer according to the invention comprises a compound of formula (I) or (II) or a mixture of compounds of formula (I) and (II).
In a preferred aspect the optical layer according to the invention comprises a compound of formula (I) or (II) together with a further recording dye. The optical layer according to the invention thereby comprise compounds of formula (I) or (II) preferably in an amount of at least 20% by weight of the mixture.
The further recording dye preferably is a dye compound of formula (III)
wherein
Further, the invention relates to a method for producing an optical layer, comprising the following steps
Preferred substrates are polycarbonate (PC) or polymethylmethacrylate (PMMA).
Organic solvents are selected from C1-8 alcohol, halogen substituted C1-8 alcohols, C1-8 ketone, C1-8 ether, halogen substituted C1-4 alkane, or amides.
Preferred C1-8 alcohols or halogen substituted C1-8 alcohols are for example methanol, ethanol, isopropanol, diacetone alcohol (DAA), 2,2,3,3-tetrafluoropropanol, trichloroethanol, 2-chloroethanol, octafluoropentanol or hexafluorobutanol.
Preferred C1-8 ketones are for example acetone, methylisobutylketone, methylethylketone, or 3-hydroxy-3-methyl-2-butanone.
Preferred halogen substituted C1-4 alkanes are for example chloroform, dichloromethane or 1-chlorobutane.
Preferred amides are for example dimethylformamide or dimethylacetamide.
The optical layer (dye layer) obtained preferably has a thickness from 70 to 250 nm.
In a preferred aspect, the present invention provides for an optical layer suitable for high-density recording material, e.g. of the WORM disc format, in a laser wavelength range of from 350-450 nm, preferably around 405 nm.
The dye compounds of formula (I) and (II) possess the required optical characteristics (such as high absorption and high recording sensitivity), an excellent solubility in organic solvents, an excellent light stability and a decomposition temperature of 250-400° C.
A method for producing an optical recording medium comprising an optical layer according to the invention comprises the following additional steps
A high-density optical data recording medium according to the invention therefore preferably is a recordable optical disc comprising: a first substrate, which is a transparent substrate with grooves, a recording layer (optical layer), which is formed on the first substrate surface using the dye of formula (I) or (II), most preferably a dye of formula (I) or (II) and a recording dye of the formula (III), a reflective layer formed on the recording layer, a second substrate, which is a transparent substrate with grooves connected to the reflective layer with an attachment layer.
Most preferably, the optical data recording medium according to the invention is a recordable optical disc of the WORM type. It may be used, for example, as a playable HD-DVD (high density digital versatile disc) or Blu-ray® disc, as storage medium for a computer or as an identification and security card or for the production of diffractive optical elements, for example holograms.
The invention accordingly relates also to a method for the optical recording, storage and playback of information, wherein a recording medium according to the invention is used. The recording and the playback advantageously take place in a wavelength range of from 350 to 500 nm.
The structure of the optical data recording medium according to the invention is governed primarily by the readout method; known function principles include the measurement of the change in the transmission or, preferably, in the reflection, but it is also known to measure, for example, the fluorescence instead of the transmission or reflection.
When the optical data recording medium is structured for a change in reflection, the following structures can be used: transparent support/recording layer (optionally multilayered)/reflective layer and, if expedient, protective layer (not necessarily transparent); or support (not necessarily transparent)/reflective layer/recording layer and, if expedient, transparent protective layer. In the first case, the light is incident from the support side, whereas in the latter case the radiation is incident from the recording layer side or, where applicable, from the protective layer side. In both cases the light detector is located on the same side as the light source. The first-mentioned structure of the recording material to be used according to the invention is generally preferred.
When the optical data recording medium is structured for a change in light transmission, the following different structure comes into consideration: transparent support/recording layer (optionally multilayered) and, if expedient, transparent protective layer. The light for recording and for readout can be incident either from the support side or from the recording layer side or, where applicable, from the protective layer side, the light detector in this case always being located on the opposite side.
Suitable lasers are those having a wavelength of 350-500 nm, for example commercially available lasers having a wavelength of 405 to 414 nm, especially semi-conductor lasers. The recording is done, for example, point for point, by modulating the laser in accordance with the mark lengths and focusing its radiation onto the recording layer. It is known from the specialist literature that other methods are currently being developed which may also be suitable for use.
The process according to the invention allows the storage of information with great reliability and stability, distinguished by very good mechanical and thermal stability and by high light stability and by sharp boundary zones of the pits. Special advantages include the high contrast, the low jitter and the surprisingly high signal/noise ratio, so that excellent readout is achieved.
The readout of information is carried out according to methods known in the art by registering the change in absorption or reflection using laser radiation.
The invention accordingly relates also to a method for the optical data recording, storage and playback of information, wherein an optical data recording medium according to the invention is used. The recording and the playback advantageously take place in a wavelength range of from 350 to 500 nm.
The compounds of formula (I) and (II) provide for particularly preferable properties when used in optical layers for optical data recording media according to the invention. They possess the required optical characteristics, demonstrated when used in the form of a solid film:
Recording performance of a compound is related to specific parameters measured on disc like:
The absorption edge is surprisingly steep even in the solid phase.
The compounds of formula (I) also show a narrow decomposition temperature of 250-350° C., fitting with the thermal requirements. Additionally, these compounds show a high solubility in organic solvents, which is ideal for the spin-coating process to manufacture optical layers.
For UV-vis spectra, λ max and ε values of the compound are determined by using an UV-vis spectrophotometer, the compound was dissolved in CH2Cl2, DMSO or in tfp. The values are obtained by balancing the measurements performed on compound solutions at three different concentrations.
DP and HR are determined using a TA Instruments DSC Q100 apparatus, the compound being incorporated into a sealed aluminum pan. Analysis conditions are as following: Temperature range from 25 to 400° C., heating rate 10° C./min, nitrogen flow of 50 ml/min. Values are determined by single measurement.
A definition and the measuring techniques of PRSNR are described in a book available from DVD Format Logo Licensing Co., Ltd. for example, Annex H of Version 0.9, PART 1 Physical Specifications, DVD Specifications for High Density Read-Only Disk.
A definition and the measuring techniques of SbER are described in a book available from DVD Format Logo Licensing Co., Ltd. for example, Annex H of Version 0.9, PART 1 Physical Specifications, DVD Specifications for High Density Read-Only Disk.
PRSNR and SbER are measured in a state in which information has been recorded in the adjacent tracks.
A definition and the measuring techniques for the light reflectivity (R) is described in a book available from DVD Format Logo Licensing Co., Ltd. for example, Annex D of Version 0.9, PART 1 Physical Specifications, DVD Specifications for High Density Read-Only Disk.
The azo ligands are prepared by azo coupling reaction of the respective diazo component and the respective coupling agent. The diazo component is prepared by diazotization reaction of the respective amine compound. These amine compounds and the coupling agents are known substances.
It is possible to use more than one amine component and/or more than one coupling agent resulting in the respective mixture of azo ligands.
The coupling reaction may be carried out in water, non-aqueous solvents and in mixtures thereof. Non-aqueous solvents are alcohols such as methanol, ethanol, propanol, butanol, pentanol, etc., dipolar aprotic solvents such as DMF, DMSO, NMP and water-immiscible solvents such as toluene or chlorobenzene. Preferably the azo coupling reaction is carried out in water.
The coupling is preferably carried out in a stoichiometric ratio of coupling component and diazo component. The coupling is generally done at temperatures between −30° C. to 100° C., preference being given to temperatures of −10° C. to 30° C., and particular preference to temperatures of −5° C. to 20° C.
The coupling may be carried out in an acidic as well as an alkaline medium. Preference is given to pH<10, particular preference to pH between 3 to 9.0.
Preferably the azo ligand is isolated following standard methods, in case of a precipitate preferably by filtration, and preferably dried.
A mixture of 15.0 g of 2-amino-4-nitrophenol, 120 ml of water and 34.3 g of concentrated hydrochloric acid (30% w/w) was gradually admixed with 24.5 ml of sodium nitrite (33% w/v) at 0° C. After 1 hour of reaction at 0° C., the dark diazotization solution was added drop wise to an alkaline solution of 22.6 g of 1,3-diethyl-2-thiobarbituric acid while maintaining pH at 7.5-9 with sodium hydroxide (30% w/w). The batch was stirred 3 hours, then filtered with suction. The precipitate was washed with water and dried. 34.3 g of the azo ligand of formula (1) was obtained.
A mixture of 15.0 g of 2-amino-4-nitrophenol, 120 ml of water and 34.3 g of concentrated hydrochloric acid (30% w/w) was gradually admixed with 24.5 ml of sodium nitrite (33% w/v) at 0° C. After 1 hour of reaction at 0° C., the dark diazotization solution was added drop wise to an alkaline solution of 15.1 g of 1,3-dimethyl-barbituric acid while maintaining pH at 7.5-9 with sodium hydroxide (30% w/w). The batch was stirred 3 hours, then filtered with suction. The precipitate was washed with water and dried. 30.1 g of the azo ligand of formula (2) was obtained.
A mixture of 15.0 g of 2-amino-4-nitrophenol, 120 ml of water and 34.3 g of concentrated hydrochloric acid (30% w/w) was gradually admixed with 24.5 ml of sodium nitrite (33% w/v) at 0° C. After 1 hour of reaction at 0° C., the dark diazotization solution was added drop wise to an alkaline solution of 20.6 g of 1-Butyl-4-methyl-2,6-dioxo-1,2,5,6-tetrahydro-pyridine-3-carbonitrile while maintaining pH at 7.5-9 with sodium hydroxide (30% w/w). The batch was stirred 3 hours, then filtered with suction. The precipitate was washed with water and dried. 35.2 g of the azo ligand of formula (3) was obtained.
With 2-amino-5-nitrophenol the compound of formula (4) was prepared in analogy to the procedure in example 2, 26 g of the azo ligand of formula (4) was obtained.
Preferably, the anionic parts of formula (1) are prepared by complexing reaction of a solution of one equivalent of a metal salt with a boiling solution of one equivalent of the ligands above described. The anionic parts of formula (II) are prepared by complexing reaction of a solution of one equivalent of a metal salt with a boiling solution of two equivalents of the ligands above described.
In one preferred embodiment of the invention the metal of the metal salt is a trivalent metal. In another preferred embodiment of the invention the metal of the metal salt is a divalent metal, and the complexing reaction is carried out in the presence of preferably 2.5 to 4, more preferably 2.9 to 3.2, especially 3 equivalents of trialkylamine, preferably triethylamine, for each equivalent of ligand. This ensures that the divalent metal atom is converted during the complexing reaction into a trivalent oxidation state, and that the metal atom is incorporated into its four-fold coordination in the complex, resulting in an anionic charge on the final complex. Preferably, when the metal salt is a divalent metal salt, the precursor is preferably cobalt sulfate heptahydrate. It is possible to use more than one azo ligand, preferably a mixture of 2 or 3 azo ligands. Preferably in this case the combined amounts of the ligands should be in the required stoichiometric amounts with regard to the metal salt. It is also possible to use more than one metal salt, preferably a mixture of 2 or 3 metal salts, preferably in the required stoichiometric amounts with regard to the azo ligands; and a combination of these measures is also possible. The ligands can be added to the metal salt or vice versa.
7.6 g of ligand of formula (3) prepared according to example 3 are suspended in 80 ml of acetonitrile. After 15 minutes stirring at reflux, 6.7 g of triethylamine are added to the mixture. 4.16 g of cobalt sulfate heptahydrate are then added for over 15 minutes, whereupon a dark orange solution of the cobalt complex dye results. The mixture is heated at reflux for 6 hours and then cooled down to room temperature. The resulting precipitate is filtered off and the press cake washed with deionized water and dried. 16.8 g of the cobalt complex dye of the formula (A) with protonated triethylamine as counterion is obtained.
The cobalt complex dye of formula (B) was prepared according to the procedure of example 5, using the respective ligand.
2.6 g of chromium acetate (0.013 moles) are dissolved in 20 mL of distilled water. 11 g of azo ligand are suspended in 50 mL of water and the pH of the reaction mixture is adjusted to 7.0 by adding sodium hydroxide. The reaction mixture is heated up to reflux The solution of Cr3(OAc)7(OH)2 is then slowly added over a period of 1 h. The reaction mixture slowly turns into a dark red solution. When the reaction is complete, the reaction mixture is cooled down to 50° C. and dropped slowly into an aqueous solution of triethylammonium chloride. 9 g of the chromium complex dye of the formula (C) with protonated triethylamine as counterion is obtained after filtration, aqueous washing and drying of the precipitate.
7.4 g of ligand of formula (1) prepared according to example 1 are suspended in 80 ml of acetonitrile. After 15 minutes stirring at reflux, 6.7 g of triethylamine are added to the mixture. 4.16 g of cobalt sulfate heptahydrate are then added for over 15 minutes, whereupon a dark yellow solution of the cobalt complex dye results. The mixture is heated at reflux for 6 hours and then cooled down to room temperature. The resulting precipitate is filtered off and the press cake washed with deionized water and dried. 13.8 g of the cobalt complex dye of the formula (E) with protonated triethylamine as counterion is obtained.
6.6 g of ligand of formula (2) prepared according to example 2 are suspended in 80 ml of acetonitrile. After 15 minutes stirring at reflux, 6.7 g of triethylamine are added to the mixture. 4.16 g of cobalt sulfate heptahydrate are then added for over 15 minutes, whereupon a dark yellow solution of the cobalt complex dye results. The mixture is heated at reflux for 6 hours and then cooled down to room temperature. The resulting precipitate is filtered off and the press cake washed with deionized water and dried. 14.2 g of the cobalt complex dye of the formula (D) with protonated triethylamine as counterion is obtained.
6.6 g of ligand of formula (4) prepared according to example 4 are suspended in 80 ml of acetonitrile. After 15 minutes stirring at reflux, 6.7 g of triethylamine are added to the mixture. 4.16 g of cobalt sulfate heptahydrate are then added for over 15 minutes, whereupon a dark yellow solution of the cobalt complex dye results. The mixture is heated at reflux for 6 hours and then cooled down to room temperature. The resulting precipitate is filtered off and the press cake washed with deionized water and dried. 14.2 g of the cobalt complex dye of the formula (F) with protonated triethylamine as counterion is obtained.
The following complex dyes, listed in Table 1 and 2, have been prepared by reacting the commercially available Basic Yellow dyes with the anionic metalazo complex dyes, prepared according to examples 5 to 10, as represented below according to the following procedure.
5.4 g of the Azo metal complex A (complex dye of the formula (A)) with protonated triethylamine as counterion, prepared according to example 5, and 2.1 g of Basic Yellow 13 are suspended in 120 ml of ethanol. The mixture is heated to reflux and kept at this temperature for 4 hours. The obtained red suspension is cooled to room temperature and the resulting precipitate is filtered with suction and washed with a further 50 ml of ethanol and 500 ml of water. The compound 13(A) is obtained with 86.4% yield.
(A)Azo metal Complex A
(B)Azo metal Complex B
(C)Azo metal Complex C
(D)Azo metal Complex D
(E)Azo metal Complex E
(F)Azo metal Complex F
Cation of Basic Yellow 1
Cation of Basic Yellow 2
Cation of Basic Yellow 11
Cation of Basic Yellow 13
Cation of Basic Yellow 28
Table 4 gives the properties of some of the prepared complex dyes of tables 1 and 2. As a reference, the decomposition point of the Azo metal Complex A with protonated triethylamine as counterion is at 327° C., (single peak), i.e. indicating that a new compound is formed when the decomposition temperature (single peak) for the complex dyes of table 1 and 2 is different from the reference. Table 3 gives some DP as a reference for the complexes with protonated triethylammonium as counterion.
Table 4: optical and thermal analysis (DP [° C.] are all single peak)
Table 4: optical and thermal analysis (DP[°C] are all single peak)
The optical and thermal properties of the compounds of formula (I) and (II) were studied. The compounds of formula (I) and (II) show high absorption at the desired wavelengths. In addition, the shapes of the absorption spectra, that still remain critical to the disc reflectivity and formation of clean mark edges, are composed of one major band, comprised in a range of from 350 to 500 nm.
More precisely, n values of the refractive index were evaluated between 1.0 and 2.7. Light stabilities were found comparable to commercial dyes which are already stabilized with quenchers for the use in optical data recording.
Sharp threshold of thermal decomposition within the required temperature range characterizes the compounds of formula (I) and (II) which are desirable for the application in optical layers for optical data recording.
1.4% by weight of the mixture according to Example 1 are dissolved in 2,2,3,3-tetrafluoro-1-propanol and the solution is filtered through a Teflon filter of pore size 0.2 μm and applied by spin-coating at 1000 rpm to the surface of a 0.6 mm thick, grooved polycarbonate disc of 120 mm diameter. The excess solution is spun off by increasing the rotational speed. On evaporation of the solvent, the dye remains behind in the form of a uniform, amorphous solid layer, the optical layer. After drying the optical layer in a circulating-air oven at 70° C. (10 min) in a vacuum coating apparatus, a 100 μm thick silver layer is then applied to the recording layer by atomisation. Then a 6 μm thick protective layer of a UV curable photopolymer (650-020, DSM) is applied thereto by means of spincoating. Finally, a second substrate is provided to combine with the resin protection layer using an attachment layer. This completes the manufacturing of a high-density recordable optical disc, the optical data recording medium.
Evaluation tests are performed using an optical disk evaluation device available from Pulse Tech Co., Ltd.
The testing conditions are the following ones:
Results of the evaluation tests for some of the complex dyes of table 1 and 2 are summarized in table 5:
A test for evaluating a degree of degradation due to repetition reproduction is conducted for each of the write-once optical disks made for the described dye recording layers. Readings are carried out at a reading laser power of 0.4 mW and the degrees of degradation of PRSNR and SbER are then measured. Maximum cycles number was found at 1 622 000 for the composition 28(A).
| Number | Date | Country | Kind |
|---|---|---|---|
| 05007639.7 | Apr 2005 | EP | regional |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/EP2006/061328 | 4/5/2006 | WO | 00 | 10/5/2007 |
