Recordable optical data storage media using special light-absorbing substances or mixtures thereof are particularly suitable for use in high-density recordable optical data storage media which operate with blue laser diodes, and in particular GaN or SHG laser diodes (360-460 nm), and/or for use in DVD-R or CD-R discs, which operate with red (635-660 nm) or infrared (780-830 nm) laser diodes, and the application of the above-mentioned dyes to a polymer substrate, in particular polycarbonate, by spin-coating or vapour deposition.

There has recently been an enormous growth in the sales of recordable compact discs (CD-R, 780 nm), which represent the technically established system.

The next generation of optical data storage media-DVDs-is currently being introduced onto the market. By using shorter-wave laser radiation (635 to 660nm) and a higher numerical aperture NA, the storage density can be increased. The recordable format is in this case the DVD-R.

Today, optical data storage formats which use blue laser diodes (based on GaN, JP 08191171 or Second Harmonic Generation SHG JP 09050629) (360 nm to 460 nm) with a high laser power, are being developed. Recordable optical data storage media will therefore also be used in this generation. The achievable storage density depends on the focussing of the laser spot in the information plane. The spot size is proportional to the laser wavelength X/NA. NA is the numerical aperture of the objective lens used. The aim is to use the smallest possible wavelength X for

obtaining the highest possible storage density. Based on semiconductor laser diodes, 390 nm are presently possible.

The patent literature describes dye-based recordable optical data storage media which are equally suitable both for CD-R and DVD-R systems (JP-A 11 043 481 and JP-A 10 181 206). In order to obtain high reflectivity, a high modulation level of the readout signal and sufficient sensitivity during recording, use is made of the fact that the IR wavelength 780 nm of the CD-R is located at the base of the long-wavelength slope of the absorption peak of the dye and the red wavelength 635 mn or 650 nm of the DVD-R is located at the base of the short-wavelength slope of the absorption peak of the dye. In JP-A 02 557 335, JP-A 10 058 828, JP-A 06 336 086, JP-A 02 865 955, WO-A 09 917 284 and US-A 5 266 699 this concept is extended to cover the working wavelength range of 450 nm on the short-wavelength slope and the red and IR range on the long-wavelength slope of the absorption peak.

In addition to the above-mentioned optical properties, the recordable information layer consisting of light-absorbing organic substances must have a morphology which is as amorphous as possible, in order to keep the noise signal during recording or reading as small as possible. For this purpose it is particularly preferable, when applying the substances by spin-coating from a solution or by vapour deposition and/or sublimation, to prevent crystallization of the light-absorbing substances during the subsequent top-coating with metallic or dielectric layers in vacuo.

The amorphous layer of light-absorbing substances should preferably have high thermal stability, since otherwise additional layers of organic or inorganic material applied by sputtering or vapour deposition onto the light-absorbing information layer form blurred boundaries due to diffusion and thus have an adverse effect on the reflectivity. In addition, if a light-absorbing substance has inadequate thermal stability at the boundary to a polymeric substrate, it can diffuse into the latter and again have an adverse effect on the reflectivity.

If the light-absorbing substance has too high a vapour pressure, it can sublime during the above-mentioned sputtering or vapour deposition of additional layers in a high vacuum and thus reduce the desired layer thickness. This in turn has a negative effect on reflectivity.

The object of the invention is therefore to provide suitable compounds which meet the high demands (such as light stability, a favourable signal-to-noise ratio, damage- free application to the substrate material, etc.) for use in the information layer of a recordable optical data storage medium, in particular for high-density recordable optical data storage formats in a laser wavelength range of 340 to 680 nm.

Surprisingly, it has been found that light-absorbing compounds from the diaza hemi- cyanine group of dyes are particularly suitable for satisfying the above-mentioned requirement profile.

The invention therefore relates to an optical data storage medium containing a preferably transparent substrate which has optionally already been coated with one or more reflecting layers and onto the surface of which a photorecordable information layer, optionally one or more reflecting layers and optionally a protective layer or an additional substrate or a top layer are applied, which data storage medium can be recorded on and read using blue or red light, preferably laser light, wherein the information layer contains a light-absorbing compound and optionally a binder, characterized in that at least one diaza hemicyanine dye is used as the light-absorbing compound.

Blue laser light is particularly preferred.

The light-absorbing compound should preferably be thermally modifiable. Pref- erably the thermal modification is carried out at a temperature of <600°C, particularly preferably at a temperature of <400°C, very particularly preferably at a temperature of <300°C, and in particular at a temperature of <200°C. Such a

modification can for example be the decomposition or chemical modification of the chromophoric centre of the light-absorbing compound.

A diaza hemicyanine of the formula (I) is preferred in which K represents a radical of the formulae (II) to (IV) xi represents O or S,

X2 represents O, S, CH or N-R2, X3 represents N, CH or C-CN, Ri, R2 and R12 independently of one another represent Cl-to C16-alkyl, C3-to C6- alkenyl, 5-to C7-cycloalkyl or C7-to C16-aralkyl, A together with X2 and the C-atom bound therebetween represents a five- membered aromatic or quasi-aromatic heterocyclic ring which can contain 1 to 4 hetero atoms and/or can be benzo-or naphtho-fused and/or substituted by non-ionic radicals, R3, R4, R5 and R6 independently of one another represent hydrogen, Cl-to C16-alkyl, C4-to C7-cycloalkyl, C7-to C16-aralkyl or a heterocyclic radical or NR3R4 or NRR6 independently of one another represent a five-or six-membered saturated ring which is attached via N and can additionally contain an N or O atom and/or be substituted by non-ionic radicals, R7 represents hydrogen, Cl-to C16-alkyl, Cl-to C16-alkoxy or halogen or R7 and W form a two-or three-membered bridge which can contain an O or N atom and/or be substituted by non-ionic radicals, R8 represents hydrogen, Cl-to C16-alkyl, Cl-to C16-alkoxy, halogen, cyano, C1- to C4-alkoxycarbonyl, O-CO-R10, NH-CO-R10, O-SO2-R10 or NH-SO2-R10, R9 represents hydrogen, Cl-to C4-alkyl or C6-to C10-aryl,

Rl° represents hydrogen, Cl-to C16-alkyl, C4-to C7-cycloalkyl, C7-to C16-aralkyl, Cl-to C16-alkoxy, mono-or bis-CI-to Ci6-alkylamino, C6-to Clo-aryl, C6-to C1O-aryloxy, C6-to CtO-arylamino or a heterocyclic radical, Rll represents hydrogen, Cl-to C4-alkyl or C6-to Cl-aryl and An-represents an anion.

Suitable non-ionic radicals are for example Cl-to C4-alkyl, Cl-to C4-alkoxy, halogen, cyano, nitro, Cl-to C4-alkoxycarbonyl, Cl-to C4-alkylthio, Cl-to C4- alkanoylamino, benzoylamino, mono-or di-Cl-to C4-alkylamino.

Alkyl, alkoxy, aryl and heterocyclic radicals can optionally contain additional radicals such as alkyl, halogen, nitro, cyano, CO-NH2, alkoxy, trialkylsilyl, trialkyl- siloxy or phenyl, the alkyl and alkoxy radicals can be straight-chain or branched, the alkyl radicals can be partially halogenated or perhalogenated, the alkyl and alkoxy radicals can be ethoxylated or propoxylated or silylated, adjacent alkyl and/or alkoxy radicals on aryl or heterocyclic radicals can together form a three-or four-membered bridge and the heterocyclic radicals can be benzo-fused and/or quaternized.

The ring A of the formula particularly preferably represents thiazol-2-yl, benzothiazol-2-yl, benzoxazol-2-yl, benzimidazol-2-yl, imidazol-2-yl, pyrazol-3-yl, 1, 3,4-triazol-2-yl, 1, 3,4-thiadiazol-2- yl, 1, 2,4-thiadiazol-5-yl, 2-or 4-pyridyl or 2-or 4-quinolyl, wherein the afore- mentioned rings can each be substituted by Cl-to C6-alkyl, Cl-to C6-alkoxy, fluorine, chlorine, bromine, iodine, cyano, nitro, Cl-to C6-alkoxycarbonyl, Cl-to C6-

alkylthio, Cl-to C6-acylamino, C6-to Clo-aryl, C6-to C10-aryloxy, C6-to Ciao- arylcarbonylamino, mono-or du--to C6-alkylamino, N-Cl-to C6-alkyl-N-C6-to Clo-arylamino, pyrrolidino, morpholino or piperazino.

In a particularly preferred form the diaza hemicyanines used are those of the formula (I), in which the ring A of the formula represents thiazol-2-yl, benzothiazol-2-yl, wherein X2 represents S and the afore- mentioned radicals can each be substituted by methyl, ethyl, methoxy, ethoxy, chlorine, cyano, methoxycarbonyl or ethoxycarbonyl, or represents 1,3,4-triazolyl or 1,3,4-thiadiazolyl, wherein X2 represents N-R or S, respectively, and the afore- mentioned radicals can each be substituted by methyl, ethyl, phenyl, methoxy, ethoxy, methylthio, ethylthio, amino, anilino, dimethylamino, diethylamino, di- propylamino, dibutylamino, N-methyl-N-cyanethylamino, N-methyl-N-hydroxy- ethylamino, N-methyl-N-phenylamino, di- (cyanethyl) amino, di- (hydroxyethyl) amino, cyanethylamino, hydroxyethylamino, pyrrolidino, piperidino, morpholino or a radical of the formula K represents a radical of the formulae (II), (III) or (IV),

X'represents 0 or S, X3 represents N, CH or C-CN, Rl, R and R12 independently of one another represent methyl, ethyl, propyl, butyl, pentyl, hexyl, benzyl, phenethyl, phenylpropyl, allyl, cyclohexyl, chloroethyl, cyanomethyl, cyanoethyl, cyanopropyl, hydroxyethyl, 2-hydroxypropyl, methoxyethyl or ethoxyethyl, R3, R4, R5 and R6 independently of one another represent methyl, ethyl, propyl, butyl, pentyl, hexyl, benzyl, phenethyl, phenylpropyl, cyclohexyl, chloroethyl, cyanomethyl, cyanoethyl, cyanopropyl, hydroxyethyl, 2-hydroxypropyl, methoxyethyl, ethoxyethyl, methoxycarbonylethyl, ethoxycarbonylethyl, acetoxyethyl, propionyloxyethyl or a radical of the formula and R3 and R5 can additionally represent hydrogen or NR3R4 and NR5R6 independently of one another represent pyrrolidino, piperidino, N- methylpiperazino, N-ethylpiperazino, N-hydroxyethylpiperazino or mor- pholino, R7 represents hydrogen, methyl, methoxy or chlorine or R7 ; Rs represent a- (CH2) 2-,- (CH2) 3-,-C (CH3)-CH2-C (CH3) 2- or -O-(CH2)2-bridge, R8 represents hydrogen, methyl, methoxy or chlorine,

R9 represents hydrogen, Rl l represents hydrogen, methyl or phenyl and An-represents an anion.

Suitable anions An-are all monovalent anions or one equivalent of a polyvalent anion. Preferably the anions are colourless. Suitable anions are, for example, chloride, bromide, iodide, tetrafluoroborate, perchlorate, hexafluorosilicate, hexa- fluorophosphate, methosulphate, ethosulphat, Cl-to Clo-alkanesulphonate, Cl-to Clo-perfluoroalkane sulphonate, Cl-to Clo-alkanoate optionally substituted by chlorine, hydroxyl or Cl-to C4 alkoxy, benzene sulphonate, naphthalene sulphonate or biphenyl sulphonate optionally substituted by nitro, cyano, hydroxyl, Cl-to C25- alkyl, perfluoro-C1-to C4-alkyl, Cl-to C4-alkoxycarbonyl or chlorine, benzene disulphonate, naphthalene disulphonate or biphenyl disulphonate optionally substituted by nitro, cyano, hydroxyl, Cl-to C4-alkyl, Cl-to C4-alkoxy, Cl-to C4- alkoxycarbonyl or chlorine, benzoate optionally substituted by nitro, cyano, Cl-to C4-alkyl, Cl-to C4-alkoxy, Cl-to C4-alkoxycarbonyl, benzoyl, chlorobenzoyl or toluoyl, the anion of naphthalenedicarboxylic acid, diphenyl ether disulphonate, tetraphenyl borate, cyanotriphenyl borate, tetra-Cl-to C20-alkoxyborate, tetra- phenoxyborate, 7,8-or 7,9-dicarba-nido-undecaborate (l-) or (2-), which are optionally substituted on the B-and/or C-atoms by one or two Cl-to C12-alkyl or phenyl groups, dodecahydro-dicarbadodecaborate (2-) or B-Cl-to C12-alkyl-C- phenyl-dodecahydro-dicarbadodecaborate(l-).

Bromide, iodide, tetrafluoroborate, perchlorate, methane sulphonate, benzene sulpho- nate, toluene sulphonate, dodecylbenzene sulphonate and tetradecane sulphonate are preferred. In a very particularly preferred form the diaza hemicyanines used are those of the formulae (VI) to (IX) in which Rl and R2 independently of one another represent methyl, ethyl, propyl, butyl, pentyl, hexyl, benzyl, cyclohexyl, chloroethyl, cyanomethyl, cyanoethyl, hydroxy- ethyl, 2-hydroxypropyl, methoxyethyl, ethoxyethyl or a radical of the formula

Rs and R6 independently of one another represent methyl, ethyl, propyl, butyl, pentyl, hexyl, benzyl, cyclohexyl, chloroethyl, cyanoethyl, hydroxyethyl, 2-hydroxy- propyl, methoxyethyl, ethoxyethyl, methoxycarbonylethyl, ethoxycarbonyl- ethyl or acetoxyethyl or NR5R6 represents pyrrolidino, piperidino or morpholino, R7 represents hydrogen or R7 ; R5 represent a- (CH2) 2-,-C (CH3)-CH2-C (CH3) 2- or -O-(CH2)2- bridge, R8 represents hydrogen, Rl3, Rl4 and Ris independently of one another represent hydrogen, methyl, methoxy, chloro, nitro or cyano, R16 and Rl7 independently of one another represent methyl, ethyl, propyl, butyl, pentyl, hexyl, benzyl, cyclohexyl, chloroethyl, cyanoethyl, hydroxyethyl, 2- hydroxypropyl, methoxyethyl, ethoxyethyl, methoxycarbonylethyl, ethoxy- carbonylethyl, acetoxyethyl or phenyl and Ri6 additionally represents hydrogen or

NR 16 R17 represents pyrrolidino, piperidino or morpholino, and An-represents tetrafluoroborate, perchlorate, hexafluorosilicate, hexafluoro- phosphate, iodide, rhodanide, cyanate, hydroxy acetate, methoxy acetate, lactate, citrate, methane sulphonate, ethane sulphonate, benzene sulphonate, toluene sulphonate, butylbenzene sulphonate, chlorobenzene sulphonate, do- decylbenzene sulphonate or naphthalene sulphonate, wherein all alkyl radicals can be branched.

In a very particularly preferred form the diaza hemicyanines used are those of the formulae (X) to (XIII)

in which Ri and R2 independently of one another represent methyl, ethyl, propyl, butyl, pentyl, hexyl, benzyl, cyclohexyl, chloroethyl, cyanomethyl, cyanoethyl, hydroxy- ethyl, 2-hydroxypropyl, methoxyethyl, ethoxyethyl or a radical of the formula Xl represents O and X3 represents CH or Xl represents S and X3 represents N, CH or C-CN, R3 and R4 independently of one another represent methyl, ethyl, propyl, butyl, pentyl, hexyl, benzyl, cyclohexyl, chloroethyl, cyanoethyl, hydroxyethyl, 2-hydroxy- propyl, methoxyethyl, ethoxyethyl, methoxycarbonylethyl, ethoxycarbonyl- ethyl or acetoxyethyl or NR3R4 represents pyrrolidino, piperidino or morpholino,

R9 represents hydrogen, R R and R independently of one another represent hydrogen, methyl, methoxy, chloro, nitro or cyano, R16 and Rl7 independently of one another represent methyl, ethyl, propyl, butyl, pentyl, hexyl, benzyl, cyclohexyl, chloroethyl, cyanoethyl, hydroxyethyl, 2- hydroxypropyl, methoxyethyl, ethoxyethyl, methoxycarbonylethyl, ethoxy- carbonylethyl, acetoxyethyl or phenyl and R16 additionally represents hydrogen or NRt6Rl7 represents pyrrolidino, piperidino or morpholino, and An-represents tetrafluoroborate, perchlorate, hexafluorosilicate, hexafluoro- phosphate, iodide, rhodanide, cyanate, hydroxy acetate, methoxy acetate, lactate, citrate, methane sulphonate, ethane sulphonate, benzene sulphonate, toluene sulphonate, butylbenzene sulphonate, chlorobenzene sulphonate, do- decylbenzene sulphonate or naphthalene sulphonate, wherein all alkyl radicals can be branched.

In a very particularly preferred form the diaza hemicyanines used are those of the formulae (XIV) to (XVII)

in which R', R2 and R12 independently of one another represent methyl, ethyl, propyl, butyl, pentyl, hexyl, benzyl, cyclohexyl, chloroethyl, cyanomethyl, cyanoethyl, hydroxyethyl, 2-hydroxypropyl, methoxyethyl, ethoxyethyl or a radical of the formula

Rl3, R"and R"independently of one another represent hydrogen, methyl, methoxy, chloro, nitro or cyano, Rl6 and Rl7 independently of one another represent methyl, ethyl, propyl, butyl, pentyl, hexyl, benzyl, cyclohexyl, chloroethyl, cyanoethyl, hydroxyethyl, 2- hydroxypropyl, methoxyethyl, ethoxyethyl, methoxycarbonylethyl, ethoxy- carbonylethyl, acetoxyethyl or phenyl and R16 additionally represents hydrogen or NR16R17 represents pyrrolidino, piperidino or morpholino, Rll represents hydrogen, methyl or phenyl and An- represents tetrafluoroborate, perchlorate, hexafluorosilicate, hexafluoro- phosphate, iodide, rhodanide, cyanate, hydroxy acetate, methoxy acetate, lactate, citrate, methane sulphonate, ethane sulphonate, benzene sulphonate, toluene sulphonate, butylbenzene sulphonate, chlorobenzene sulphonate, do- decylbenzene sulphonate or naphthalene sulphonate, wherein all alkyl radicals can be branched.

In a very particularly preferred form the diaza hemicyanines used are those of the formulae (IX), (XIII) and (XVII).

For a recordable optical data storage medium according to the invention which is recorded on and read using light from a blue laser, such diaza hemicyanine dyes are preferred whose absorption maximum xmas2 ils in the range from 420 to 550 nm, wherein the wavelength #1/2 at which the extinction on the short-wavelength slope of the absorption maximum of the wavelength Xmax2 is half the extinction value at xmas2) and the wavelength kI/lo, at which the extinction on the short-wavelength slope of the

absorption maximum of the wavelength max2 is a tenth of the extinction value at Xmax2n are preferably in each case no further than 50 nm away from each other.

Preferably such a diaza hemicyanine dye does not display a shorter-wave maximum small at a wavelength below 350 nm, particularly preferably below 320 nm, and very particularly preferably below 290 nm.

Preferred diaza hemicyanine dyes are those with an absorption maximum Of 410 to 530 nm.

Particularly preferred diaza hemicyanine dyes are those with an absorption maximum Xmax2 of 420 to 510 nm.

Very particularly preferred diaza hemicyanine dyes are those with an absorption maximum xmas2 of 430 to 500 nm.

In these diaza hemicyanine dyes . 1/2 and #1/10, as defined above, are preferably no further than 40 nm, particularly preferably no further than 30 nm, and very particu- larly preferably no further than 20 nm away from each other.

For a recordable optical data storage medium according to the invention which is recorded on and read using light from a red laser, such diaza hemicyanine dyes are preferred whose absorption maximum Xmax2 iS in the range from 500 to 650 nm, wherein the wavelength XI/2 at which the extinction on the long-wavelength slope of the absorption maximum of the wavelength xmas2 ils half the extinction value at #max2, and the wavelength #1/10, at which the extinction on the long-wavelength slope of the absorption maximum of the wavelength xmas2 ils a tenth of the extinction value at xmas2, are preferably in each case no further than 50 nm away from each other.

Preferably such a diaza hemicyanine dye does not display a longer-wave maximum Xmax3 at a wavelength below 750 nm, particularly preferably below 800 nm, and very particularly preferably below 850 nm.

Preferred diaza hemicyanine dyes are those with an absorption maximum zu (max2 of 530 to 630 nm.

Particularly preferred diaza hemicyanine dyes are those with an absorption maximum Xmax2 of 550 to 620 nm.

Very particularly preferred diaza hemicyanine dyes are those with an absorption maximum max2 of 580 to 610 nm.

In these diaza hemicyanine dyes #1/2 and #1/10, as defined above, are preferably no further than 40 nm, particularly preferably no further than 30 nm, and very particu- larly preferably no further than 20 nm away from each other.

At the absorption maximum max2 the diaza hemicyanine dyes have a molar extinc- tion coefficient s of >30000 1/mol cm, preferably >40000 l/mol cm, particularly preferably >50000 1/mol cm and very particularly preferably >7000 l/mol cm.

The absorption spectra are, for example, measured in solution.

Suitable diaza hemicyanines having the required spectral properties are in particular those in which the change in the dipole moment A =#µg - µag#, i. e. the positive difference between the dipole moments in the ground state and the first excited state is as small as possible, i. e. preferably <5 D, and particularly preferably <2 D. A method of determining such a change in the dipole moment Ap is described, for example, in F. Wurthner et al., Angew. Chem. 1997,109,2933 and in the literature cited therein. Low solvatochromism (methanol/methylene chloride) is also a suitable criterion for selection. Preferred diaza hemicyanines are those whose solvato- chromism AS methylene chloride ~ Xmethanol|) i. e. the positive difference between the absorption wavelengths in the solvents methylene chloride and methanol, is <25 nm, particularly preferably <15 nm, and very particularly preferably <5 nm.

Diaza hemicyanines of the formulae (I) and (VI) to (XVII) are known, for example, from BE 825 455, DE-OS 1 044 023, DE-OS 2 811 258, DE-OS 1 163 775.

Another part of the invention are diaza hemicyanines of formula (I), wherein K means a radical of formula (III) and the other residues have the above meaning.

Another special part of the invention are diaza hemicyanines of the formulae (X), (XI), (XII) or (XIII), wherein the residues have the above meaning.

The light-absorbing substances described guarantee sufficiently high reflectivity (>10%) of the optical data storage medium in the unrecorded state and sufficiently high absorption for the thermal degradation of the information layer upon spotwise illumination with focussed light, if the wavelength of the light is in the range from 360 to 460 nm and 600 to 680 nm. The contrast between the recorded and unrecorded areas of the data storage medium is effected by the change in reflectivity in terms of the amplitude as well as the phase of the incident light as a result of the changed optical properties of the information layer following thermal degradation.

The diaza hemicyanine dyes are preferably applied to the optical data storage medium by spin-coating or vacuum coating. The diaza hemicyanines can be mixed with other dioaza hemicyanines or with other dyes having similar spectral properties.

The information layer can contain additives in addition to the diaza hemicyanine dyes, such as binders, wetting agents, stabilizers, diluents and sensitizers as well as other constituents.

In addition to the information layer, the optical data storage medium can contain other layers such as metal layers, dielectric layers and protective layers. Metals and dielectric layers are used, for example, for adjusting the reflectivity and the thermal balance. Depending on the laser wavelength, the metals can be gold, silver or aluminium, etc. Dielectric layers are, for example, silicon dioxide and silicon nitride. Protective layers are, for example, photocurable surface coatings, adhesive layers and protective films.

Adhesive layers can consist of a pressure-sensitive material.

Pressure-sensitive adhesive layers consist mainly of acrylic adhesives. Nitto Denko DA-8320 or DA-8310, which are disclosed in the patent JP-A 11-273147, can, for example, be used for this purpose.

The optical data storage medium has, for example, the following layer assembly (cf. Fig. 1) : a transparent substrate (1), optionally a protective layer (2), an information layer (3), optionally a protective layer (4), optionally an adhesive layer (5) and a top layer (6).

Preferably, the optical data storage medium assembly can contain: a preferably transparent substrate (1), onto whose surface at least one photorecordable information layer (3), which can be recorded on using light, preferably laser light, optionally a protective layer (4), optionally an adhesive layer (5) and a transparent top layer (6) are applied; a preferably transparent substrate (1), onto whose surface a protective layer (2), at least one information layer (3) which can be recorded on using light, preferably laser light, optionally an adhesive layer (5) and a transparent top layer (6) are applied; a preferably transparent substrate (1), onto whose surface optionally a protective layer (2), at least one information layer (3) which can be recorded on using light, preferably laser light, optionally a protective layer (4), optionally an adhesive layer (5) and a transparent top layer (6) are applied; a preferably transparent substrate (1), onto whose surface at least one information layer (3) which can be recorded on using light, preferably laser

light, optionally an adhesive layer (5) and a transparent top layer (6) are applied.

Alternatively, the optical data storage medium has for example the following layer assembly (cf. Fig. 2): a preferably transparent substrate (11), an information layer (12), optionally a reflecting layer (13), optionally an adhesive layer (14) and an additional, preferably transparent, substrate (15).

The invention also relates to optical data storage media according to the invention which are recorded on using blue or red light, in particular laser light.

The following examples illustrate the subject matter of the invention:

Examples Example 1 4 g of 2-amino-5- (diisopropylamino)-1, 3,4-thiadiazole were dissolved in 40 ml of glacial acetic acid. 8 ml of 85% by weight phosphoric acid and 6 ml of 48% by weight sulphuric acid were added dropwise at 10°C. 6.8 g of nitrosylsulphuric acid (40% by weight in sulphuric acid) were then added dropwise at 5°C over a period of 30 mins.. After 4 h at 0-5°C the nitrite excess was destroyed with amidosulphonic acid.

This diazotized product was added dropwise at 10°C over a period of 1 hour to a solution of 5 g of 2-morpholino-4-phenylthiazole in 30 ml of glacial acetic acid, a pH of 3 being maintained with a 20% by weight aqueous soda solution. After stirring overnight at a pH of 3.5 the mixture was filtered off with suction and the residue was washed with water. The solid was stirred into 100 ml of water and the mixture was adjusted to a pH of 7.5, filtered off with suction once again and the residue was washed with water. After drying, the crude product was dissolved in 100 ml of toluene. By slowly adding 400 ml of hexane with stirring, the product was precipitated, filtered off with suction, washed with hexane and afterwords with water and dried. 3.7 g (41% of theory) of a violet powder of the formula was obtained.

M. p. =155°C #max (dioxane) = 531 nm.

2.3 g of the above azo dye were dissolved in 20 ml of glacial acetic acid. 1.3 g of dimethyl sulfate were added and the mixture was stirred at 70°C for 5 hours. After cooling to room temperature 200 ml of water were added. The solution was extracted with 50 ml of toluene and afterwords with 100 ml of chloroform. The chloroform phase was evaporated to dryness. The resulting violet dye was solved in 30 ml of methanol. 0.6 g of lithium perchlorate were added. After stirring over night the precipitated product was filtered off with suction, washed with methanol and dried.

1.5 g (53% of theory) of a violet powder of the formula was obtained. max (methanol) = 592 nm £ =30100Vmolom Solubility: >2% in TFP (2,2,3,3-tetrafluoropropanol) a glassy film Diaza hemicyanine dyes which are also suitable are listed in the table: Ex. 2 K An-kmax s kII2-A%') CA/nmI)/I/mol 7illlo/nm CiA \+ cm/nm R 0 CH3 2 °S S (CH30SO3 508 36570 s H N H H, C 3""# N C104-602 79750 214) C3 N 4 H C + sN 3 k C104 580 56200 3 Hic CH 3 N-N.,. 5 _ "C104 582 56800 A _ CH3 0 CH3 CN 7"CW, C104-588 s CH3 c2H5 I /C2H5 8 BF4-590 47900 HNH S02 Ex. x \ An~ Amax £ 1/2-X2) xz A/nm')/I/mol killo \N+ RUZ Y I 9 BF,-590 52100 s iso 'vs 10, l m CH3 BF4-600 56010 244 l _/9 NCH3 N 11"I BF4 589 56680 CN CN 12 BF4-568 CN I _ 13 C104-583 60260 s cl3 //oH \ NCH 14 C104 602 59430 Cl3 CH3 CH, CH3 N-N+ 15 11 C104, 599 67110 234) 'S H3 N 16 t Ct04'587 82300 10 CN 17 e. CIO4 606 74560 23) Nu NCJ S Ex. X An~ XmaY R 1/2-X2) /nm/1/mol vlo/nm N + RUZ CH3 CH N-tl,. 18 N1S32 ; J¢ ; f C2H5 C104-606 77260 214) s H3c, y N 0 H 19"I \ N PF6'592 77300 / H I N 20 BF4-587 72570 CON -CH, NC N-N+ NGN""\ N 21 NC BF4-601 82610 zu N-N+ 22 Ho PF 599 56320 OH OH /QH3 CH 3 N-N N-. r0 r? 23 CH 3 BF4-597 63100 S xi po o / r I-,. \ N 25 J. ff) t C104'588 54700 ce \OH Ex, x 2 K Ari a,"max E T, li2- da, z> A/iun')/I/mol Xlllo/nm N\+ czn/nm RUZ CH CH3 423) N-N+ N 26 I BF4 526 53970 f \ m z N zon 27 N C104-492 52100 CN /CH3 28 CH, Bf 460 1 CH3 ; chez N-N+ N C104 538 z 5 C 3 CH3 /cl3 N-N+ H, CH3 /CH 3 S- 11 CIO 465 4 N H 32 N'CH, C104-495 CH 3 CH3 CH3 H3 33 ' NCN3 C104 590 S Ex. X > An Ama S í/2-ak2) A f//nm/1/mol ? "ia/nm 'N+ RUZ CONS 2 34 N SW C104 593 s Cl H3c\ N/ 0 c2H5 35 BF4 586 62000 HN iCHs Sou zon 36"I \ N, BF4 601 67750 con CN CCN _ _ zu 37 l (CH3SO3-607 71480 15 cru CH3 CONH2 _ ci nô 38 BF4-591 HN,-0 HNSOZ I

in methanol, unless indicated otherwise.

##=##methylene chloride - #methanol# 3) on the short-wave slope 4) on the long-wave slope

Example 39 A 4% by weight solution of the dye of Example 27 in 2,2,3,3-tetrafluoropropanol was prepared at room temperature. This solution was applied by means of spin- coating to a pre-grooved polycarbonate substrate. The pre-grooved polycarbonate substrate was produced in the form of a disc by injection-moulding. The dimensions of the disc and the groove structure corresponded to those usually employed for DVD-R's. The disc containing the dye layer as the information carrier was vapour- plated with 100 nm of silver. Then a UV-curable acrylic lacquer was applied by spin-coating and cured using a UV lamp. Using a dynamic recording test setup constructed on an optical bench and consisting of a diode laser (R = 405 nm) for producing linearly polarized light, a polarization-sensitive beam splitter, a 7/4-plate and a movably suspended collective lens with a numerical aperture NA of 0.65 (actuator lens), experiments on the recording (writing) and reading of data were carried out. The light reflected from the reflecting layer of the disc was coupled out of the beam path with the aid of the abovementioned polarization-sensitive beam splitter and focussed onto a four-quadrant detector through an astigmatic lens. At a linear velocity of V = 2.6 m/s and a recording (writing) power of Pw = 13. 2 mW a signal-to-noise ratio of CW = 42 dB was measured. The recording power was applied as an oscillating pulse sequence, the disc being irradiated alternately for 1 us with the abovementioned recording power Pw and for 4 us with the reading power P, ? 0.44 mW. The disc was irradiated with this oscillating pulse sequence until it had turned completely a single time. Then the marking produced was read with a reading power Pr ? 0.44 mW and the abovementioned signal-to-noise ratio C/N was deter- mined.

Optical data storage media were obtained analogously using the other examples from the above table.