Patent Application
20050142489
The invention relates to squarylium dyes, to a process for preparing them, to the components on which the squarylium dyes are based and their preparation, and to optical data carriers comprising the squarylium dyes in their information layer.
Write-once optical data carriers using specific light-absorbent substances or mixtures thereof are particularly suitable for use in DVD-R disks which operate with red (635-660 nm) laser diodes and for the application of the abovementioned dyes to a polymer substrate, in particular polycarbonate, by spin coating.
The write-once compact disk (CD-R, 780 nm) has recently experienced enormous volume growth and represents the technically established system.
The next generation of optical data stores—DVDs—is currently being introduced onto the market. The use of shorter-wavelength laser radiation (635-660 nm) and higher numerical aperture NA enables the storage density to be increased. The writable format in this case is DVD-R.
The achievable storage density depends on the focusing of the laser spot on the information plane. Spot size scales with the laser wavelength λ/NA. NA is the numerical aperture of the objective lens used. In order to obtain the highest possible storage density, the use of the smallest possible wavelength λ is the aim. At present, 390 nm is possible on the basis of semiconductor laser diodes.
Apart from the abovementioned optical properties, the writable information layer comprising light-absorbent organic substances has to have a substantially amorphous morphology to keep the noise signal during writing or reading as small as possible. For this reason, it is particularly preferred that crystallization of the light-absorbent substances be prevented in the application of the substances by spin coating from a solution, by vapour deposition and/or sublimation during subsequent coating with metallic or dielectric layers under reduced pressure.
The amorphous layer comprising light-absorbent substances preferably has a high heat distortion resistance, since otherwise further layers of organic or inorganic material which are applied by sputtering or vapour deposition can form blurred boundaries due to diffusion and thus adversely affect the reflectivity. Furthermore, a light-absorbent substance which has insufficient heat distortion resistance can, at the boundary to a polymeric support, diffuse into the latter and once again adversely affect the reflectivity.
A light-absorbent substance whose vapour pressure is too high can sublime during the abovementioned deposition of further layers by sputtering or vapour deposition in a high vacuum and thus reduce the desired layer thickness. This in turn has an adverse effect on the reflectivity.
It is therefore an object of the invention to provide suitable compounds which satisfy the high requirements (e.g. light stability, favourable signal/noise ratio, damage-free application to the substrate material, and the like) for use in the information layer in a write-once optical data carrier for writable optical data store formats in a laser wavelength range from 600 to 680 nm.
It has surprisingly been found that light-absorbent compounds selected from the group of specific symmetrical squarylium compounds can satisfy the abovementioned requirement profile particularly well.
The invention accordingly provides squarylium compounds of the general formula I,
where
Preference is given to squarylium compounds of the formula I which correspond to the formula Ia,
where
Formula Ia is one of the possible mesomeric formulae.
For the purposes of the present application, “alkyl” is preferably C1-C6-alkyl, “aryl” is preferably C6-C10-aryl, “aralkyl” is preferably C7-C16-aralkyl and “alkoxy” is preferably C1-C6-alkoxy.
Possible substituents on the alkyl, aryl or aralkyl radicals are halogen, in particular F, hydroxy, nitro, cyano, carboxyl, alkoxy, trialkylsilyl and trialkylsiloxy. The alkyl radicals can be linear, cyclic or branched. They can be partially halogenated or perhalogenated. Examples of substituted alkyl radicals are trifluoromethyl, chloroethyl, cyanoethyl, methoxyethyl. Examples of cyclic alkyl radicals are cyclohexylmethyl and cyclopropylmethyl. Examples of branched alkyl radicals are isopropyl, tert-butyl, 2-butyl, neopentyl. Examples of possible aryl radicals are phenyl, 4-methoxyphenyl, 4-cyanophenyl, 3,5-bis(trifluoromethyl)phenyl, 4-trifluoromethylphenyl and 4-ethylphenyl. Examples of aralkyl radicals are benzyl, phenethyl, phenylpropyl, 4-methoxybenzyl, 4-cyanobenzyl, 3,5-bis(trifluoromethyl)benzyl, 4-trifluoromethylbenzyl and 4-ethylbenzyl. Examples of carboxyl radicals are ethoxycarbonyl, butoxycarbonyl and trifluoromethoxycarbonyl.
Examples of alkylcarbonyl are acetyl, trifluoroacetyl, propanoyl, butanoyl, pentanoyl and hexanoyl.
Preferred substituted or unsubstituted alkyl radicals are methyl, ethyl, n-propyl, n-pentyl, isobutyl, isopropyl, perfluorinated methyl and ethyl.
Preferred substituted or unsubstituted aralkyl radicals are, for example, 4-trifluoromethylbenzyl, 2-trifluoromethylbenzyl, 3,5-bistrifluoromethylbenzyl and 4-fluoro-2-trifluoromethylbenzyl.
A preferred alkoxycarboxyl radical is ethoxycarbonyl.
Particular preference is given to squarylium compounds of the formula Ia in which
Even greater preference is given to squarylium compounds of the formula Ia in which
The invention further provides a process for preparing the squarylium compounds of the invention, which is characterized in that 3,4-dihydroxy-3-cyclobutene-1,2-dione (squaric acid) is reacted with at least one compound of the formula III
R—R5 (III),
in particular with a pyrrole compound of the formula (IIIa), preferably in a suitable solvent,
where
The process of the invention is preferably carried out in alcohol, in particular in ethanol. Preferred reaction temperatures are greater than 70° C., in particular 75-85° C. The process of the invention is likewise preferably carried out in aqueous acetic acid. The mixing ratio of acetic acid/water is, for example, from 3:1 to 1:3, preferably from 2:1 to 1:2, particularly preferably 1:1. Preferred reaction temperatures range from room temperature to the boiling point of the medium. Preference is likewise given to using a catalytic amount of a mineral acid, in particular HCl. The product generally precipitates as a pure solid from the reaction solution and is preferably washed with ether after being separated off.
The pyrrole compounds of the formula (IIIa) which are preferably used for preparing the squarylium compounds of the invention are likewise provided by the present invention.
The invention therefore also provides pyrroles of the formula (IIIa)
where
Particular preference is given to pyrrole compounds of the formula IIIa in which
The invention likewise provides a process for preparing the novel pyrrole compounds of the formula IIIa, which is characterized in that a pyrrole compound of the formula (II)
where
A particularly suitable base is KOH. The reaction is preferably carried out in a suitable solvent, for example in dimethyl sulphoxide (DMSO), dimethylformarnmide (DMF) or a mixture thereof. The reaction is preferably carried out at a temperature of 20-100° C., particular preferably 50-90° C., in particular 65-80° C. If R5 in formula II is ethoxycarbonyl, the ester group is saponified to give the corresponding alkali metal salt of the pyrrolecarboxylic acid. This can be precipitated from aqueous solution by acidification and filtered off.
The product can in this way be obtained in satisfactory purity without complicated crystallization steps or similar purification steps.
The invention further provides for the use of the squarylium dyes of the invention as light-absorbent compounds in the information layer of write-once optical data carriers.
In this use, the optical data carrier is preferably written on and read by means of red laser light, in particular laser light having a wavelength in the range 600-680 nm.
The invention further provides for the use of squarylium compounds as light-absorbent compounds in the information layer of write-once optical data carriers which can be written on and read by means of red laser light, in particular laser light having a wavelength in the range 600-680 nm.
The invention further provides an optical data carrier comprising a preferably transparent substrate to whose surface a light-writable information layer, if desired one or more reflection layers and a further substrate or a protective layer have been applied, which can be written on and read by means of red light, preferably having a wavelength in the range 600-680 nm, preferably laser light, where the information layer comprises a light-absorbent compound and, if desired, a binder, characterised in that at least one squarylium dye according to the invention is used as light-absorbent compound.
The light-absorbent compound should preferably be able to be changed thermally. The thermal change preferably occurs at a temperature of <600° C., particularly preferably at a temperature of <400° C., very particularly preferably at a temperature of <300° C., in particular <200° C. Such a change can be, for example, a decomposition or chemical change of the chromophoric centre of the light-absorbent compound.
It is likewise preferred that the light-absorbent compound can be changed thermally only at above 100° C.
Preferred embodiments of the light-absorbent compounds in the optical data stores of the invention correspond to the preferred embodiments of the squarylium dye of the invention.
In a preferred embodiment, the light-absorbent compounds used are compounds of the formula (Ia) in which
In a particularly preferred embodiment, the light-absorbent compounds used are compounds of the formula (Ia) in which
In the case of the write-once optical data carrier of the invention which is written on and read by means of the light of a red laser, preference is given to light-absorbent compounds whose absorption maximum λmax is in the range from 500 to 650 mm, where the wavelength λ1/2 at which the absorbance in the long wavelength flank of the absorption maximum at the wavelength λmax2 is half of the absorbance value at λmax and the wavelength λ1/10 at which the absorbance in the long wavelength flank of the absorption maximum at the wavelength λmax is one tenth of the absorbance value at λmax are preferably not more than 60 nm apart. Such a light-absorbent compound preferably has no longer-wavelength maximum λmax3 up to a wavelength of 750 nm, particularly preferably 800 nm, very particularly preferably 850 nm.
Preference is given to light-absorbent compounds having an absorption maximum λmax of from 510 to 620 nm.
Particular preference is given to light-absorbent compounds having an absorption maximum λmax of from 530 to 610 nm.
Very particular preference is given to light-absorbent compounds having an absorption maximum λmax of from 550 to 600 nm.
In these light-absorbent compounds, λ1/2 and λ1/10 as defined above, are preferably not more than 50 nm apart, particularly preferably not more than 40 nm apart, very particularly preferably not more than 30 nm apart.
The light-absorbent compounds preferably have a molar extinction coefficient ε of >60000 l/mol cm, more preferably >80000 l/mol cm, particularly preferably >100000 l/mol cm, very particularly preferably >120000 l/mol cm.
Particularly suitable squarylium compounds are those in which the dipole moment change Δμ=|μg−μag|, i.e. the positive difference between the dipole moments in the ground state and in the first excited state, is very small, preferably <5 D, particularly preferably <2 D. A method of determining such a dipole moment change A1 is described, for example, in F. Würthner et al., Angew. Chem. 1997, 109, 2933, and in the literature cited therein. A low solvent-induced wavelength shift (dioxane/DMF) is likewise a suitable selection criterion. Preference is given to squarylium compounds whose solvent-induced wavelength shift Δλ=|λDMF−λdioxane|, i.e. the positive difference between the absorption wavelengths in the solvents dimethylformamide and dioxane, is <20 nm, particularly preferably <10 run, very particularly preferably <5 nm.
The absorption spectra are preferably measured in solution.
The light-absorbent compounds used according to the invention preferably make it possible to achieve a reflectivity of >10% in the optical data carrier in the unwritten state and a sufficiently high absorption for thermal degradation of the information layer on point-wise illumination with focused light if the wavelength of the light is in the range from 600 to 680 nm. The contrast between written and unwritten points on the data carrier is achieved by the reflectivity change of the amplitude and also the phase of the incident light due to the changed optical properties of the information layer after the thermal degradation.
The squarylium dyes of the invention are preferably applied to the optical data carrier by spin coating. They can be mixed with one another or with other dyes having similar spectral properties. The information layer can comprise not only the squarylium dyes of the invention but also additives such as binders, wetting agents, stabilizers, diluents and sensitizers and also further constituents.
Apart from the information layer, further layers such as metal layers, dielectric layers and protective layers may also be present in the optical data store of the invention. Metals and dielectric layers serve, inter alia, to adjust the reflectivity and the heat absorption/retention. Metals can be, depending on the laser wavelength, gold, silver, aluminium, etc. Examples of dielectric layers are silicon dioxide and silicon nitride. Protective layers are, for example, photocurable surface coatings, (pressure-sensitive) adhesive layers and protective films.
Pressure-sensitive adhesive layers consist mainly of acrylic adhesives. Nitto Denko DA-8320 or DA-8310, disclosed in the patent JP-A 11-273147, can, for example, be used for this purpose.
The optical data carrier of the invention has, for example, the following layer structure (cf.
In
Alternatively, the structure of the optical data carrier can
The arrows shown in
The invention further provides optical data carriers according to the invention which have been written on by means of red light, in particular red laser light, particularly preferably having a wavelength of 600-680 nm.
The invention likewise provides a write-once optical data carrier whose information layer comprises at least one phthalocyanine dye as light-absorbent compound, and also provides a process for producing it.
It is accordingly an object of the invention to provide suitable compounds which satisfy the high requirements (e.g. light stability, favourable signal/noise ratio, damage-free application to the substrate material, and the like) for use in the information layer in a write-once optical data carrier, in particular for high-density writable optical data store formats, in a laser wavelength range from 360 to 460 nm.
It has surprisingly been found that specific phthalocyanines as light-absorbent compounds can satisfy the abovementioned requirement profile particularly well.
Phthalocyanines display an intense absorption in the wavelength range 360-460 nm which is important for lasers, namely the B or Soret bands.
The present invention accordingly provides an optical data carrier comprising a preferably transparent substrate which may, if desired, have previously been coated with one or more reflective layers and to whose surface a light-writable information layer, if desired one or more reflection layers and if desired a protective layer or a further substrate or a covering layer have been applied, which can be written or read by means of blue light, preferably laser light, particularly preferably light having a wavelength of 360-460 nm, in particular 380-420 nm, very particularly preferably 390-410 nm, or by means of infrared light, preferably laser light, particularly preferably light having a wavelength of 760-830 nm, where the information layer comprises a light-absorbent compound and, if desired, a binder, characterized in that at least one phthalocyanine of the formula (I)
where
Preference is given to phthalocyanines of the formulae (Ia), (Ib), (Ic), (Id), (Ie), (If), (Ig) and (Ih)
The formulae (Ic) and (If) to (Ih) are to be interpreted as indicating that the two halogen atoms are either both located above the plane of the phthalocyanine ring or one is located above and one is located below the plane of the phthalocyanine ring.
The phthalocyanines used according to the invention are known from, for example, J. N. Esposito, L. E. Sutton, M. E. Kenney, Inorg. Chem. 6, 1967, 1116 and W. J. Kroenke, M. E. Kenney, Inorg. Chem. 3, 1964, 696, or can be prepared as described there.
They can in principle be prepared by known methods, e.g.:
The phthalocyanines of the formula (II), preferably those in which Me=Sn, are prepared, for example, by reduction of phthalocyanines of the formula (I), preferably with Me=Sn, in which X1 and X2 are halogen, for example chlorine. A suitable reducing agent is, for example, sodium tetrahydroborate (NaBH4).
The light-absorbent compounds can be changed thermally. The thermal change preferably occurs at a temperature of <600° C. Such a change can be, for example, a decomposition or chemical change of the chromophoric centre of the light-absorbent compound.
The light-absorbent substances described guarantee a sufficiently high reflectivity of the optical data carrier in the unwritten state and a sufficiently high absorption for thermal degradation of the information layer on point-wise illumination with focused blue light, in particular laser light, preferably having a wavelength in the range from 360 to 460 nm. The contrast between written and unwritten points on the data carrier is achieved by the reflectivity change of the amplitude and also the phase of the incident light due to the changed optical properties of the information layer after the thermal degradation.
This means that the optical data carrier can preferably be written on and read by means of laser light having a wavelength of 360-460 nm.
The optical data carrier can likewise be written on and read by means of infrared light, in particular laser light having a wavelength of 760-830 nm, with the groove spacing and groove geometry then preferably being matched to the wavelength and numerical aperture.
The invention further provides for the use of the phthalocyanines of the formula (I) as light-absorbent compounds in the information layer of optical storage media.
The invention likewise provides for the use of the phthalocyanines of the formula (I) for producing optical storage media. The phthalocyanines are preferably used as light-absorbent compounds in the information layer.
The phthalocyanines which are particularly preferably employed in these uses have a content of more than 90% by weight, in particular more than 95% by weight, particularly preferably more than 98% by weight, based on the phthalocyanine of the formula (I).
The invention further provides a particulate solid preparation of a phthalocyanine of the formula (I), characterized in that the particles have a mean particle size of from 0.5 μm to 10 mm.
In a preferred embodiment of the particulate solid preparations, preference is given to those which have a mean particle size of from 0.5 to 20 μm, in particular from 1 to 10 μm, hereinafter referred to as fine powder. Such fine powders can be produced, for example, by milling.
Preference is likewise given to particulate solid preparations having a mean particle size of from 50 to 300 μm, hereinafter referred to as the finely crystalline form.
Further preferred particulate solid preparations are ones which have a mean particle size of from 50 μm to 10 mm, preferably from 100 μm to 800 μm, and form a particulate shaped body as agglomerates or conglomerates of primary particles. Such shaped bodies can, for example, have the shape of droplets, raspberries, flakes or rods, hereinafter referred to as granular materials.
The particle size of the finely crystalline form can, for example, be set via the parameters in the synthesis. For example, rapid heating, for example over a period of from 30 to 60 minutes, of the mixture of the components (phthalonitrile or aminoimino-isoindole and the appropriate metal halide in the appropriate solvent) to the reaction temperature, for example from 160 to 220° C., preferentially forms a finely divided form. A similar result is obtained when the metal halide is added to the reaction mixture (phthalonitrile or amino-imino-isoindole in the appropriate solvent) only at the reaction temperature, for example at from 160 to 190° C. Slow heating, for example over a period of from 65 to 250 minutes, of the mixture of the components to the reaction temperature, for example from 160 to 220° C., preferentially forms a coarse form.
The particulate solid preparations of the invention preferably comprise
The solid preparations of the invention are preferably low in dust, free-flowing and have a good storage stability.
The granular materials can be produced in various ways, e.g. by spray drying, fluidized-bed spray granulation, fluidized-bed buildup granulation or powder fluidized-bed agglomeration.
Preference is given to granulation by spray drying, with both rotary disc analyzers and single-fluid or two-fluid nozzles, inter alia, being possible as spraying device. Preference is given to the single-fluid nozzle, in particular the swirl chamber nozzle, which is preferably operated at a feed pressure of 20-80 bar.
The inlet and outlet temperatures during spray drying depend on the desired residual moisture content, on safety measures and on economic considerations. The inlet temperature is preferably 120-200° C., in particular 140-180° C., and the outlet temperature is preferably 40-80° C.
The granular materials are generally produced by firstly mixing the dye filter cake, if appropriate together with auxiliaries and additives, intensively in a stirred vessel. The crystals of the suspension are preferably comminuted in a mill, e.g. a bead mill, so that a finely divided atomizable suspension is obtained.
In a preferred embodiment, the dye suspension is an aqueous suspension. Granulation is carried out by spray drying.
The invention further provides solid shaped bodies such as pellets, extrudates, etc., comprising a phthalocyanine of the formula (I), preferably in an amount of more than 90% by weight, in particular more than 95% by weight, preferably more than 98% by weight, based on the shaped body. Further additives to the solid shaped bodies can be binders. The sum of phthalocyanine of the formula (I) and binder is preferably more than 95% by weight, particularly preferably more than 99% by weight.
Such shaped bodies can be produced, for example, by pressing the phthalocyanine of the formula (I), if desired in the presence of binders, at a pressure of from 5 to 50 bar, preferably from 10 to 20 bar.
The invention likewise provides dispersions, preferably aqueous dispersions, containing a metal complex of the formula (I), preferably in an amount of from 10 to 90% by weight, based on the dispersion. Possible dispersants are, for example: polymeric dispersants based on acrylates, urethanes or long-chain polyoxyethylene compounds. Examples of suitable products are: Solsperse 32000 or Solsperse 38000 from Avecia.
The invention further provides a process for coating substrates with the phthalocyanines of the formula (1). This is preferably carried out by spin coating, sputtering or vacuum vapour deposition. The phthalocyanines of the formulae (Ia) to (Ih) can be applied particularly well by vacuum vapour deposition or sputtering, in particular vacuum vapour deposition.
Starting materials for such coatings applied by sputtering or vacuum vapour deposition are all the abovementioned forms of the phthalocyanines of the formula (I), i.e. fine powders, finely crystalline forms or granular materials, particulate solid preparations, solid shaped bodies and dispersions. The latter are employed particularly for applying the phthalocyanines in finely divided form to a surface from which they can then be applied to the substrate by sputtering or vacuum vapour deposition.
Phthalocyanine purities of greater than 50%, particularly preferably greater than 85% and very particularly preferably greater than 90%, in particular greater than 95% or greater than 98%, are preferred for these procedures.
The phthalocyanines can be mixed with one another or with other dyes having similar spectral properties. The information layer can comprise not only the phthalocyanines but also additives such as binders, wetting agents, stabilizers, diluents and sensitizers and also further constituents.
The invention further provides an apparatus for the vapour deposition of light-absorbent compounds onto a substrate for producing optical storage media, which is characterized in that the dye can be vaporized by heating at a low background pressure and be deposited on the substrate. The background pressure is below 10−1 Pa, preferably below 10−3 Pa, particularly preferably below 10−4 Pa. The dye is preferably heated by means of resistive heating or by microwave absorption.
In particular, the invention provides an optical data carrier as described above in which the light-absorbent compound of the formula (I), if appropriate together with the abovementioned additives, forms an information layer which is optically amorphous. For the purposes of the present invention, amorphous means that no crystallites can be observed under an optical microscope and no Bragg reflections but only an amorphous halo can be observed in the X-ray diffraction pattern.
Apart from the information layer, further layers such as metal layers, dielectric layers and protective layers can be present in the optical data store. Metals and dielectric layers serve, inter alia, to adjust the reflectivity and the heat absorption/retention. Metals can be, depending on the laser wavelength, gold, silver, aluminium, alloys, etc. Examples of dielectric layers are silicon dioxide and silicon nitride. Protective layers are, for example, photocurable surface coatings, adhesive layers and protective films.
The adhesive layers can be pressure-sensitive.
Presssure-sensitive adhesive layers consist mainly of acrylic adhesives. Nitto Denko DA-8320 or DA-8310, disclosed in the patent JP-A 11-273147, can, for example, be used for this purpose.
The optical data carrier has, for example, the following layer structure (cf.
The structure of the optical data carrier preferably:
Alternatively, the optical data carrier has, for example, the following layer structure (cf.
Alternatively, the optical data carrier has, for example, the following layer structure (cf.
Alternatively, the structure of the optical data carrier can
The invention further provides optical data carriers according to the invention which have been written on by means of blue light, in particular laser light, particularly preferably laser light having a wavelength of 360-460 mm.
The following examples illustrate the invention.
The filtrate was evaporated and chromatographed on silica using dichloromethane as eluant. The first violet fraction gave, after taking off the solvent, a further 0.72 g of product. Total yield: 0.92 g (45% of theory).
Further suitable squarylium dyes are shown in the table. These are obtained by analogous preparation of the components and the squarylium dyes.
1)in acetone unless indicated otherwise
2)on the long wavelength flank
3)Δλ = |λDMF − λdioxane|
The dye dibromogermanium phthalocyanine (GeBr2Pc) was vapour-deposited in a high vacuum (pressure p 2-10−5 mbar) from a resistively heated molybdenum boat onto a pregrooved polycarbonate substrate at a rate of about 5 A/s. The layer thickness was about 55 nm. The pregrooved polycarbonate substrate had been produced as a disk by means of injection moulding. The diameter of the disk was 120 mm and its thickness was 0.6 mm. The groove structure produced in the injection moulding process had a track spacing of about 1 μm and the groove depth and groove width at half height were about 150 nm and about 260 nm, respectively. The disk with the dye layer as information carrier was coated with 100 nm of Ag by vapour deposition. A UV-curable acrylic coating was subsequently applied by spin coating and cured by means of a UV lamp. The disk was tested by means of a dynamic writing test apparatus constructed on an optical test bench comprising a GaN diode laser (λ=405 nm) for generating linearly polarized laser light, a polarization-sensitive beam splitter, a A/4 plate and a movably suspended collecting lens having a numerical aperture NA=0.65 (actuator lens). The light reflected from the disk was taken out from the beam path by means of the abovementioned polarization-sensitive beam splitter and focused by means of an astigmatic lens onto a four-quadrant detector. At a linear velocity V=5.00 m/s and a writing power Pw=13 mW, a signal/noise ratio C/N=41 dB was measured. The writing power was applied as a pulse sequence, with the disk being irradiated alternatively for 1 μs with the abovementioned writing power Pw and for 4 μs with the reading power Pr=0.44 mW. The disk was irradiated with this pulse sequence until it had rotated once. The markings produced in this way were then read using the reading power Pr=0.44 mW and the abovementioned signal/noise ratio CIN was measured.
9.95 g of the dichlorotin phthalocyanine of the formula
in 125 ml of pyridine were admixed at room temperature with 4.9 g of sodium tetrahydroborate. The mixture was stirred under reflux (115° C.) for 75 minutes and slowly cooled to 90° C. At this temperature, 100 ml of water were slowly added dropwise. The mixture was then refluxed for another 30 minutes, cooled to room temperature and filtered with suction. The filter cake was stirred with 200 ml of methanol, filtered with suction and washed with methanol until the washings were clear. After washing with 50 ml of water, it was dried at 30° C. under reduced pressure. This gave 4.03 g (63% of theory) of a blue powder of the formula
1.6 g of this product in 32 ml of chloronaphthalene which had been dried over molecular sieves were admixed at room temperature with a solution of 0.2 ml of bromine in 10 ml of chloronaphthalene while stirring. The mixture was then stirred at 70-75° C. for one hour, with the temperature rising briefly to 90° C. After cooling to room temperature, the mixture was filtered with suction, washed with toluene until the washings were clear, subsequently washed with methanol until the washings were virtually colourless and dried at 30° C. under reduced pressure. This gave 1.46 g (74% of theory) of a blue powder of the formula
| Number | Date | Country | Kind |
|---|---|---|---|
| 102 12 199.0 | Mar 2002 | DE | national |
| 102 45 581.3 | Sep 2002 | DE | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP03/02789 | 3/18/2003 | WO |
