Patent Grant
7041354
The invention relates to a write-once optical data carrier comprising a cyanine dye as light-absorbent compound in the information layer, to a process for its production and also to the application of the above-mentioned dyes to a polymer substrate, in particular polycarbonate, by spin coating or vapour deposition.
Write-once optical data carriers using specific light-absorbent substances or mixtures thereof are particularly suitable for use in high-density writeable optical data stores which operate with blue laser diodes, in particular GaN or SHG laser diodes (360–460 nm) and/or for use in DVD-R or CD-R disks which operate with red (635–660 nm) or infrared (780–830 nm) laser diodes.
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. Through the use of shorter-wave laser radiation (635–660 nm) and higher numerical aperture NA, the storage density can be increased. The writeable format in this case is DVD-R.
Today, optical data storage formats which use blue laser diodes (based on GaN, JP 08 191 171 or Second Harmonic Generation SHG JP 09 050 629) (360 nm–460 nm) with high laser power are being developed. Writeable optical data stores will therefore also be used in this generation. The achievable storage density depends on the focussing of the laser spot on the information plane. Spot size scales with the laser wavelength λ/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.
The patent literature describes dye-based writeable optical data stores which are equally suitable for CD-R and DVD-R systems (JP-A 11 043 481 and JP-A 10 181 206). To achieve a high reflectivity and a high modulation height of the read-out signal and also to achieve sufficient sensitivity in writing, use is made of the fact that the IR wavelength of 780 nm of CD-Rs is located at the foot of the long wavelength flank of the absorption peak of the dye and the red wavelength of 635 nm or 650 nm of DVD-Rs is located at the foot of the short wavelength flank 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 U.S. Pat. No. 5,266,699, this concept is extended to the 450 nm working wavelength region on the short wavelength flank and the red and IR region on the long wavelength flank of the absorption peak.
Apart from the abovementioned optical properties, the writeable 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 covering 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 to the light-absorbent information layer by sputtering or vapour deposition would 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 above-mentioned deposition of further layers by sputtering or vapour deposition in a high vacuum and thus reduce the layer thicknes to below the desired value. 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, in particular for high-density writeable optical data store formats in a laser wavelength range from 340 to 830 nm.
Surprisingly, it has been found that light-absorbent compounds selected from the group of cyanine dyes can satisfy the abovementioned requirement profile particularly well.
The invention accordingly provides an optical data carrier comprising a preferably transparent substrate which may, if desired, have previously been coated with one or more reflection layers and to whose surface a light-writeable 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 on or read by means of blue, red or infrared light, preferably laser light, where the information layer comprises a light-absorbent compound and, if desired, a binder, characterized in that at least one cyanine dye 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.
Preference is given to a cyanine dye of the formula (I)
where
Possible nonionic radicals are, for example, C1–C4-alkyl, C1–C4-alkoxy, halogen, cyano, nitro, C1–C4-alkoxycarbonyl, C1–C4-alkylthio, C1–C4-alkanoylamino, benzoylamino, mono- or di-C1–C4-alkylamino.
Alkyl, alkoxy, aryl and heterocyclic radicals may, if desired, bear further radicals such as alkyl, halogen, nitro, cyano, CO—NH2, alkoxy, trialkylsilyl, trialkylsiloxy 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 may together form a three- or four-membered bridge and the heterocyclic radicals can be benzo-fused and/or quaternized.
The radical of the formula II
particularly preferably represents benzothiazol-2-yl, thiazol-2-yl, thiazolin-2-yl, benzoxazol-2-yl, oxazol-2-yl, oxazolin-2-yl, benzimidazol-2-yl, imidazol-2-yl, imidazolin-2-yl, pyrrolin-2-yl, 3-H-indol-2-yl, benz[c,d]indol-2-yl, 2- or 4-pyridyl or 2- or 4-quinolyl,
The radical of the formula III
particularly preferably represents benzothiazol-2-ylidene, thiazol-2-ylidene, thiazolin-2-ylidene, isothiazol-3-ylidene, 1,3,4-thiadiazol-2-ylidene, 1,2,4-thiadiazol-5-ylidene, benzoxazol-2-ylidene, oxazol-2-ylidene, oxazolin-2-ylidene, 1,3,4-oxadiazol-2-ylidene, benzimidazol-2-ylidene, imidazol-2-ylidene, imidazolin-2-ylidene, pyrrolin-2-ylidene, 1,3,4-triazol-2-ylidene, 3H-indol-2-ylidene, benz[c,d]indol-2-ylidene, 2- or 4-pyridyl or 2- or 4-quinolyl, each of which bear the radical R2, which is as defined above, on X3 which represents N,
where the abovementioned rings may each be substituted by C1–C6-alkyl, C1–C6-alkoxy, fluorine, chlorine, bromine, iodine, cyano, nitro, C1–C6-alkoxycarbonyl, C1–C6-alkylthio, C1–C6-acylamino, C6–C10-aryl, C6–C10-aryloxy, C6–C10-arylcarbonylamino, mono- or di-C1–C6-alkylamino, N—C1–C6-alkyl-N—C6–C10-arylamino, pyrrolidino, morpholino or piperazino.
In a particularly preferred embodiment, the cyanine dyes used are ones of the formula (I),
in which
In a likewise particularly preferred embodiment, the cyanine dyes used are ones of the formula (I),
in which
In a likewise particularly preferred embodiment, the cyanine dyes used are ones of the formula (I),
in which
In a likewise particularly preferred embodiment, the cyanine dyes used are ones of the formula (I),
in which
Possible anions An− include all monovalent anions or one equivalent of a polyvalent anion or one equivalent of an oligomeric or polymeric anion. Preference is given to colourless anions. Examples of suitable anions are chloride, bromide, iodide, tetrafluoroborate, perchlorate, hexafluorosilicate, hexafluorophosphate, methosulphate, ethosulphate, C1–C10-alkanesulphonate, C1–C10-perfluoroalkanesulphonate, unsubstituted or chloro-, hydroxy- or C1–C4-alkoxy-substituted C1–C10-alkanoate, unsubstituted or nitro-, cyano-, hydroxy-, C1–C25-alkyl-, perfluoro-C1–C4-alkyl-, C1–C4-alkoxycarbonyl- or chloro-substituted benzenesulphonate, or naphthalenesulphonate or biphenylsulphonate, unsubstituted or nitro-, cyano-, hydroxy-, C1–C4-alkyl-, C1–C4-alkoxy-, C1–C4-alkoxycarbonyl- or chloro-substituted benzenedisulphonate, naphthalenedisulphonate or biphenyldisulphonate, unsubstituted or nitro-, cyano-, C1–C4-alkyl-, C1–C4-alkoxy-, C1–C4-alkoxycarbonyl-, benzoyl-, chlorobenzoyl- or toluyl-substituted benzoate, the anion of naphthalenedicarboxylic acid, (diphenyl ether)disulphonate, tetraphenylborate, cyanotriphenylborate, tetra-C1–C20-alkoxyborate, tetraphenoxyborate, 7,8- or 7,9-dicarba-nido-undecaborate(1-) or (2-), which may, if desired, be substituted on the B- and/or C atoms by one or two C1–C12-alkyl or phenyl groups, dodecahydro-dicarbadodecaborate(2-) or B—C1–C12-alkyl-C-phenyl-dodecahydro-dicarbadodecaborate(1-), polystyrenesulphonate, poly(meth)acrylate, polyallylsulphonate.
Preference is given to bromide, iodide, tetrafluoroborate, perchlorate, hexafluorophosphate, methanesulphonate, trifluoromethanesulphonate, benzenesulphonate, toluenesulphonate, dodecylbenzenesulphonate, tetradecanesulphonate, polystyrenesulphonate.
In a very particularly preferred embodiment, the cyanine dyes used are ones of the formulae (IV) to (XII)
where
In the formulae (IV) to (XII), it is especially preferred that
In a likewise very particularly preferred embodiment, the cyanine dyes used are ones of the formulae (XIII) to (XXV)
where
In the formulae (XIII) to (XXV), it is especially preferred that
In a likewise very particularly preferred embodiment, the cyanine dyes used are ones of the formulae (XXVI) to (XXXVII)
where
Exceptional preference is given to cyanine dyes of the formulae (XXVI) to (XXVIII) and (XXXII) to (XXXIV)
in which
In the case of a write-once optical data carrier according to the invention which is written on and read by means of the light of a blue laser, preference is given to cyanine dyes whose absorption maximum λmax1 is in the range from 340 to 410 nm, where the wavelength λ1/2 at which the absorbance in the long wavelength flank of the absorption maximum at the wavelength λmax1 is half of the absorbance value at λmax1 and the wavelength λ1/10 at which the absorbance in the long wavelength flank of the absorption maximum at the wavelength λmax1 is one tenth of the absorbance value at λmax1 are preferably not more than 50 nm apart. Such a cyanine dye preferably has no longer-wavelength maximum λmax2 up to a wavelength of 500 nm, particularly preferably 550 nm, very particularly preferably 600 nm.
Preference is given to cyanine dyes having an absorption maximum λmax1 of from 345 to 400 nm.
Particular preference is given to cyanine dyes having an absorption maximum λmax1 of from 350 to 380 nm.
Very particular preference is given to cyanine dyes having an absorption maximum λmax1 of from 360 to 370 nm.
In the case of these dyes, λ1/2 and λ1/10, as defined above, are preferably not more than 40 nm apart, particularly preferably not more than 30 nm apart, very particularly preferably not more than 10 nm apart.
Dyes which are suitable in this respect are ones of the formulae (IV) to (VI) and (X) to (XII), in which Y is N, and ones of the formulae (VII) to (IX) in which Y is CH.
In the case of a write-once optical data carrier according to the invention which is written on and read by means of the light of a blue laser, preference is also given to cyanine dyes whose absorption maximum λmax2 is in the range from 420 to 550 nm, where the wavelength λ1/2 at which the absorbance in the short wavelength flank of the absorption maximum at the wavelength λmax2 is half of the absorbance value at λmax2 and the wavelength λ1/10 at which the absorbance in the short wavelength flank of the absorption maximum at the wavelength λmax2 is one tenth of the absorbance value at λmax2 are preferably not more than 50 nm apart. Such a cyanine dye preferably has no shorter-wavelength maximum λmax1 down to a wavelength of 350 nm, particularly preferably down to 320 nm, very particularly preferably down to 290 nm.
Preference is given to cyanine dyes having an absorption maximum λmax2 of from 410 to 530 nm.
Particular preference is given to cyanine dyes having an absorption maximum λmax2 of from 420 to 510 nm.
Very particular preference is given to cyanine dyes having an absorption maximum λmax2 of from 430 to 500 nm.
In these cyanine dyes, λ1/2 and λ1/10, as defined above, are preferably not more than 40 nm apart, particularly preferably not more than 30 nm apart, very particularly preferably not more than 20 nm apart.
Dyes which are suitable in this respect are ones of the formulae (IV) to (VI) and (X) to (XII), in which Y represents CH, and ones of the formulae (XIII) to (XXIV).
In the case of a write-once optical data carrier according to the invention which is written on and read by means of the light of a red laser, preference is given to cyanine dyes whose absorption maximum λmax2 is in the range from 500 to 650 nm, 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 λmax2 and the wavelength λ1/10 at which the absorbance in the long wavelength flank of the absorption maximum at the wavelength λmax2 is one tenth of the absorbance value at λmax2 are preferably not more than 50 nm apart. Such a cyanine dye preferably has no longer-wavelength maximum λmax3 up to a wavelength of 750 nm, particularly preferably up to 800 nm, very particularly preferably up to 850 nm.
Preference is given to cyanine dyes having an absorption maximum λmax2 of from 530 to 630 nm.
Particular preference is given to cyanine dyes having an absorption maximum λmax2 of from 550 to 620 nm.
Very particular preference is given to cyanine dyes having an absorption maximum λmax2 of from 580 to 610 nm.
In these cyanine dyes, λ1/2 and λ1/10, as defined above, are preferably not more than 40 nm apart, particularly preferably not more than 30 nm apart, very particularly preferably not more than 20 nm apart.
Dyes which are suitable in this respect are ones of the formulae (XIII) to (XV) and (XIX) to (XXI).
In the case of a write-once optical data carrier according to the invention which is written on and read by means of the light of a infrared laser, preference is given to cyanine dyes whose absorption maximum λmax3 is in the range from 650 to 810 nm, where the wavelength λ1/2 at which the absorbance in the long wavelength flank of the absorption maximum at the wavelength λmax3 is half of the absorbance value at λmax3 and the wavelength λ1/10 at which the absorbance in the long wavelength flank of the absorption maximum at the wavelength λmax3 is one tenth of the absorbance value at λmax3 are preferably not more than 50 nm apart.
Preference is given to cyanine dyes having an absorption maximum λmax3 of from 660 to 790 nm.
Particular preference is given to cyanine dyes having an absorption maximum λmax3 of from 670 to 760 nm.
Very particular preference is given to cyanine dyes having an absorption maximum λmax3 of from 680 to 740 nm.
In these cyanine dyes, λ1/2 and λ1/10, as defined above, are preferably not more than 40 nm apart, particularly preferably not more than 30 nm apart, very particularly preferably not more than 20 nm apart.
Dyes which are suitable in this respect are ones of the formulae (XXV) to (XXVII) and (XXXI) to (XXXIII).
The cyanine dyes have a molar extinction coefficient ε of >40 000 l/mol cm, preferably >60 000 l/mol cm, particularly preferably >80 000 l/mol cm, very particularly preferably >100 000 l/mol cm, at the absorption maximum λmax2.
The absorption spectra are measured, for example, in solution.
Suitable cyanine dyes having the required spectral properties are, in particular, 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 Δμ 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 (methanol/methylene chloride) is likewise a suitable selection criterion. Preference is given to cyanine dyes whose solvent-induced wavelength shift Δλ=|λmethylene chloride−λmethanol|, i.e. the positive difference between the absorption wavelengths in the solvents methylene chloride and methanol, is <25 nm, particularly preferably <15 nm, very particularly preferably <5 nm.
Some cyanine dyes of the formula (I) are known, e.g. from DE-C 883 025, DE-A 1 070 316, DE-A 1 170 569, J. Chem. Soc. 1951, 1087, Ann. Soc. Chim. Pol. 1963, 225.
The invention further provides cyanine dyes of the formula
where
Preference is given to cyanine dyes of the formula (XL)
in which
Particular preference is given to p being 1 and the ring A representing 3,3-dimethyl-3H-indol-2-yl, 5-methyl-3,3-dimethyl-3H-indol-2-yl, 5-methoxy-3,3-dimethyl-3H-indol-2-yl, 5-nitro-3,3-dimethyl-3H-indol-2-yl, 5-chloro-3,3-dimethyl-3H-indol-2-yl or 5-methoxycarbonyl-3,3-dimethyl-3H-indol-2-yl, very particularly preferably 3,3-dimethyl-3H-indol-2-yl.
The invention further provides cyanine dyes of the formula
where
Preference is given to cyanine dyes of the formula (XLI)
in which
Particular preference is given to p being 1 and the ring A representing 3,3-dimethyl-3H-indol-2-yl, 5-methyl-3,3-dimethyl-3H-indol-2-yl, 5-methoxy-3,3-dimethyl-3H-indol-2-yl, 5-nitro-3,3-dimethyl-3H-indol-2-yl, 5-chloro-3,3-dimethyl-3H-indol-2-yl or 5-methoxycarbonyl-3,3-dimethyl-3H-indol-2-yl, very particularly preferably 3,3-dimethyl-3H-indol-2-yl.
Preference is likewise given to p being 0 and the ring A representing benzothiazol-2-yl, 5-methoxy-benzothiazol-2-yl, 5-chloro-benzothiazol-2-yl, 5-cyano-benzothiazol-2-yl, 3,3-dimethyl-3H-indol-2-yl, 5-methyl-3,3-dimethyl-3H-indol-2-yl, 5-methoxy-3,3-dimethyl-3H-indol-2-yl, 5-nitro-3,3-dimethyl-3H-indol-2-yl, 5-chloro-3,3-dimethyl-3H-indol-2-yl or 5-methoxycarbonyl-3,3-dimethyl-3H-indol-2-yl, very particularly preferably benzothiazol-2-yl or 3,3-dimethyl-3H-indol-2-yl.
The cyanine dyes can be prepared by methods known per se.
The light-absorbent compounds described guarantee a sufficiently high reflectivity (>10%) 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 light if the wavelength of the light is in the range from 360 to 460 nm and 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 cyanine dyes are preferably applied to the optical data carrier by spin coating or vacuum vapour deposition. The cyanine dyes can be mixed with one another or with other dyes having similar spectral properties. In particular, dyes containing different anions can also be mixed. The information layer can comprise not only the cyanine dyes but also additives such as binders, wetting agents, stabilizers, diluents and sensitizers and also further constituents.
It is likewise possible to use mixtures with other, preferably cationic dyes. The other dyes used for the mixture are preferably ones whose λmax differs by not more than 30 nm, preferably not more than 20 nm, very particularly preferably not more than 10 nm, from the λmax2 or λmax3 of the dye of the formula (I). Examples which may be mentioned are dyes of the classes of cyanines, streptocyanines, hemicyanines, diazahemicyanines, nullmethines, enamine dyes, hydrazone dyes, di- or tri(het)arylmethane dyes, xanthene dyes, azine dyes (phenazines, oxazines, thiazines) or, for example, from the classes of azo dyes, anthraquinone dyes, neutrocyanines, porphyrins or phthalocyanines. Such dyes are known, for example, from H. Berneth, Cationic Dyes in Ullmann's Encyclopedia of Industrial Chemistry, VCH, 6th edition.
Apart from the information layer, further layers such as metal layers, dielectric layers, barrier layers and protective layers may be present in the optical data carrier. Metals and dielectric and/or barrier 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. Barrier layers are dielectric or metal layers. 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 11-2731471, 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.
The invention further provides optical data supports according to the invention which have been written on by means of blue or red light, in particular laser light.
The following examples illustrate the subject-matter of the invention.
8.1 g of 2-amino-3-methyl-5-diisopropylamino-1,3,4-thiadiazolium methosulphate, prepared from 2-amino-5-diisopropylamino-1,3,4-thiadiazole and dimethyl sulphate, and 5 g of 1,3,3-trimethyl-2-methylene-3H-indol-ω-aldehyde were boiled in a mixture of 25 ml of toluene and 2,3 g of methanesulphonic acid for 12 hours using a water separator. After cooling, 50 ml of hexane were added and the oil which separated out was separated off. This was taken up in 200 ml of water. The aqueous phase was extracted three times with 200 ml each time of chloroform. The chloroform phase was evaporated on a rotary evaporator. This gave 2.3 g (19% of theory) of a red powder of the formula
m.p.=115° C. λmax (methanol)=544 nm ε=96235 l/mol cm λ1/2–λ1/10 (short wavelength flank)=36 nm λ1/2–λ1/10 (long wavelength flank)=13 nm Solubility: >2% in TFP (2,2,3,3-tetrafluoropropanol) Glass-like film
3.1 g of 1-methyl-2-methylthio-benzothiazolium methosulphate, prepared from 2-methylthiobenzothiazole and dimethyl sulphate, and 2.6 g of 1-ethyl-2-methyl-thiazolinium iodide, prepared from 2-methylthiazoline and ethyl iodide, were boiled in 50 ml of pyridine for 3 hours. After cooling, the solid was filtered off with suction, washed with 5 ml of pyridine and dried. This gave 1.1 g (27% of theory) of a colourless powder of the formula
m.p.=250–254° C. λmax (methanol)=384 nm ε=54621 l/mol cm λ1/2–λ1/10 (long wavelength flank)=10 nm Solubility: 5% in TFP (2,2,3,3-tetrafluoropropanol)
0.4 g of the above product were stirred under reflux in 15 ml of methanol together with 0.1 g of lithium perchlorate for 1 hour. After cooling, the solid was filtered off with suction, washed with 3 ml of methanol and dried. This gave 0.3 g (80% of theory) of a colourless powder of the formula
m.p.=220–225° C. λmax (methanol)=384 nm ε=56117 l/mol cm λ1/2–λ1/10 (long wavelength flank)=10 nm Solubility: 5% in TFP (2,2,3,3-tetrafluoropropanol) Glass-like film
Cyanine dyes which are likewise suitable are shown in the following table:
1)in methanol unless indicated otherwise.
2)Δλ = |λmethylene chloride − λmethanol|
3)on the short wavelength flank
4)on the long wavelength flank
5)in methanol/chloroform 1:1
6)in acetone
7)in NMP
A 2% strength by weight solution comprising 66.7% by weight of the dye from Example 24 and 33.3% by weight of the dye of the formula
in 2,2,3,3-tetrafluoropropanol was prepared at room temperature. This solution was applied by means of spin coating to a pregrooved polycarbonate substrate. The pregrooved polycarbonate substrate had been produced as a disk by means of injection moulding. The dimensions of the disk and the groove structure corresponded to those customarily used for DVD-Rs. The disk with the dye layer as information carrier was coated with 120 nm of gold and then, on top of the gold layer, 200 nm of SiO by vapour deposition. A UV-curable acrylic coating composition 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 tester bench comprising a diode laser (λ=656 nm) for generating linearly polarized light, a polarization-sensitive beam splitter, a λ/4 plate and a movably suspended collecting lens having a numerical aperture NA=0.6 (actuator lens). The light reflected from the reflection layer of 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=3.5 m/s and a writing power Pw=21 mW, a signal-noise ratio C/N=42 dB was measured. The writing power was applied as an oscillating pulse sequence, with the disk being irradiated alternately for 1 μs with the abovementioned writing power Pw and for 4 μs with the reading power Pr≈0.6 mW. The disk was irradiated with this oscillating pulse sequence until it had rotated once. The marking produced in this way was then read using the reading power Pr and the abovementioned signal/noise ratio C/N was measured.
| Number | Date | Country | Kind |
|---|---|---|---|
| 101 15 227 | Mar 2001 | DE | national |
| 101 36 064 | Jul 2001 | DE | national |
| 102 02 571 | Jan 2002 | DE | national |
This application is a Divisional of Ser. No. 10/101,793, filed Mar. 20, 2002 now U.S. Pat. No. 6,835,725 issued Dec. 28, 2004.
| Number | Name | Date | Kind |
|---|---|---|---|
| 2476525 | Anish et al. | Jul 1949 | A |
| 3071467 | Rauch | Jan 1963 | A |
| 3090782 | Coenen et al. | May 1963 | A |
| 3287465 | Brack et al. | Nov 1966 | A |
| 4751309 | Daltrozzo et al. | Jun 1988 | A |
| 5266699 | Naef et al. | Nov 1993 | A |
| 6214431 | Hua | Apr 2001 | B1 |
| Number | Date | Country |
|---|---|---|
| 883 025 | Jul 1953 | DE |
| 0 887 202 | Dec 1998 | EP |
| 1 178 083 | Feb 2002 | EP |
| 785939 | Feb 1956 | GB |
| 848016 | Jul 1958 | GB |
| 1024486 | Aug 1963 | GB |
| 6-336086 | Dec 1994 | JP |
| 8-191171 | Jul 1996 | JP |
| 2-557335 | Nov 1996 | JP |
| 9-50629 | Feb 1997 | JP |
| 10-58828 | Mar 1998 | JP |
| 10-181206 | Jul 1998 | JP |
| 11-43481 | Feb 1999 | JP |
| Number | Date | Country | |
|---|---|---|---|
| 20050042407 A1 | Feb 2005 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 10101793 | Mar 2002 | US |
| Child | 10953235 | US |
