Writable and erasable high-density optical storage media

Details Writable and erasable high-density optical storage media Writable and erasable high-density optical storage media

1998-04-29

2001-06-12

Evans, Elizabeth (Department: 1774)

Stock material or miscellaneous articles

Circular sheet or circular blank

C428S064200, C428S064400, C428S064800, C428S913000, C430S270140, C430S495100, C430S945000, C369S283000, C369S288000

Reexamination Certificate

active

06245403

ABSTRACT:

The invention relates to the field of optical data storage on writable and erasable high-density storage media, where the bits of information differ through the optical properties at the written and unwritten pits. The novel storage media contain, as storage elements, certain perylene pigments and can be used, for example, as disks having a diameter of 120 or 80 mm in the multi-rewritable DVD-RAM format.
The invention likewise relates to a process for the optical recording, storage, reproduction, modification or erasure of data at a wavelength of from 400 to 700 nm in which a novel storage medium is used.
In the multimedia age, the storage capacity of conventional CD disks is no longer sufficient [Oyo Butsuri 64, 208-219 (1995)]. Attempts are therefore being made to replace the CD format by the DVD format (“DVD” stands for “digital video disk” or “digital versatile disk”). The aim is a storage capacity of at least 4.7 Gbyte. However, DVD disks having a capacity of 4.7 Gbyte can only be produced by series embossing using a master (DVD-Video, DVD-Audio, DVD-ROM), and individually are neither writable nor erasable.
WO 90/01480 describes the use of fluorescent diketopyrrolopyrrole and perylenetetracarboxylic diamide dyes as optical data storage elements. These dyes can initially be in the form of crystals with a uniform size of from 0.1 to 200 &mgr;m and can be converted from a non-fluorescent modification into a fluorescent modification by irradiation with a laser beam. If the dyes are used together with a thermally stable auxiliary substance having a melting point of from 170 to 190° C., the written fluorescent data store can be erased again by heating to above 220° C. However, the erasing speed is very slow; in addition, these systems have an unsatisfactory life, and detection of the fluorescence is technically very complex.
U.S. Pat. No. 4,812,352 describes discontinuous microstructures of N,N′-di(3,5-xylyl)perylene-3,4:9,10-bis(dicarboximide) in the form of a coating on a substrate. Although it is claimed that they can be used for data storage, specific examples of this application are not disclosed. If data storage should nevertheless succeed, this would be an irreversible process, since the microstructures grow only very slowly in a high vacuum, so that they are impossible to regenerate reasonably easily (for example in a writing device). In addition, these microstructures have a length of 1.5 &mgr;m and have a low refractive index, so that they are unsuitable for the high capacity and high resolution desired.
Applied optics [26/7, 1240-5 (1987)] describes films comprising anthraquinone dyes which melt without decomposing and can be converted, using a modulated krypton ion laser having a wavelength of 647.1 nm, from an amorphous phase into a crystalline phase or vice versa, depending on the pulse length. However, the erasing speed, in the region of milliseconds, is much too slow for practical use.
However, the dye systems only meet the requirements of DVD-R and DVD-RAM to an unsatisfactory extent, in particular with respect to the high storage density and the erasing speed. In addition, dyes, in contrast to pigments, have poor light stability; in addition, heating, as is repeatedly necessary in DVD-RAM, causes dyes to decompose or diffuse into the adjacent high-molecular-weight medium, forming “holes”. Such systems therefore have a short life. Furthermore, crystallization is, in spite of the use of nucleating layers, too slow to enable targeted, selective erasure of individual pits or areas on the storage medium at normal recording or reading speeds.
Writable and erasable storage media comprising eutectic mixtures of Ga—Se—Te are disclosed in Journal of Non-Crystalline Solids 97&98, 1351-1354 (1987). The storage layer of these media can be converted from a crystalline phase into an amorphous phase and vice versa using a semiconductor laser having a wavelength of 830 nm, with an erasure time of 1 ,us being achievable under optimum conditions. The use of more recent compact, high-power red diode lasers, which emit in the range from 630 to 690 nm, in principle enables an improvement in the data packing density by allowing a reduction in the track separation (distance between 2 turns of the data track) and the size of the marks (pits).
However, the desired high storage density of 4.7 Gbyte per 120 mm disk side nevertheless cannot be achieved using these storage media, but instead only a storage density of 2.6 Gbyte. In addition, the precise composition of the eutectic mixture is extremely important, so that the production of such media is difficult and expensive. Moreover, mass consumer products containing Ga, Se and/or Te are very undesirable for ecotoxicological reasons. Also, systems based on material flow exhibit non-negligible phase separation on ageing [Optical Recording, A. B. Marchant, Addison-Wesley Publishing Company, 87 (1990)], so that their durability and the long-term security of the data written thereon is not guaranteed.
Surprisingly, it has now been found that writable and erasable high-density optical data storage media with a high writing and erasing speed and improved properties are obtained if certain perylene pigments are used in the storage layer. These media are suitable for use as DVD-R and in particular also as DVD-RAM.
The invention relates to an optical storage medium comprising a substrate and a storage layer, wherein the storage layer comprises a compound of the formula (I) or (II)
in which A and A′, independently of one another, are unsubstituted or mono- or di-halo-, -hydroxy-, —C
1
-C
6
alkyl-, —C
1
-C
6
alkoxy-, -cyano- or -nitro-substituted phenyl, pyridyl, pyrrolyl, imidazolyl, furyl or thienyl, which can, if desired, be fused to a benzene ring, are halide, tetrafluoroborate or unsubstituted or with one or more halogen substituted C
1
-C
6
alkane-sulfonate, benzenesulfonate, C
1
-C
6
alkylbenzenesulfonate, C
1
-C
6
alkylsulfate or di-C
1
-C
6
alkyl-phosphonate of N-C
1
-C
6
alkyl-pyridiniumyl, or are unsubstituted or mono- or di-hydroxy-substituted C
2
-C
6
alkyl or C
2
-C
6
alkenyl, whose chain may be uninterrupted or interrupted by one or two oxygen atoms,
B and B′, independently of one another, are 2 H, S, S
2
or SO
2
, and
n and n′, independently of one another, are each a number from 1 to 4.
A and A′ are preferably phenyl or C
2
-C
6
alkyl. Any substituents of phenyl are preferably hydroxyl, halogen, methyl or methoxy. C
2
-C
6
Alkyl is preferably unsubstituted or substituted with one hydroxy group.
B and B′ are preferably each 2 H.
n and n′ are preferably each the number 1 or 2, and are particularly preferably both the number 2.
Halogen is chlorine, bromine, fluorine or iodine, preferably chlorine or bromine.
Alkyl or alkenyl, for example C
1
-C
6
alkyl or C
2
-C
6
alkenyl, can be straight-chain, branched or cyclic. C
1
-C
6
alkyl is therefore, for example, methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, tert-butyl, cyclobutyl, n-pentyl, 2-pentyl, 3-pentyl, 2,2-dimethylpropyl, cyclopentyl, n-hexyl, 2-ethylbutyl or cyclohexyl.
C
1
-C
6
Alkanesulfonate is preferably methanesulfonate, ethanesulfonate or trifluoromethane-sulfonate, most preferably methanesulfonate. C
1
-C
6
Alkyl in C
1
-C
6
alkylbenzenesulfonate, C
1
-C
6
alkylsulfate or di-C
1
-C
6
alkyl-phosphonate is preferably methyl, ethyl or trifluoromethyl, most preferably methyl. C
1
-C
6
Alkyl in N—C
1
-C
6
alkyl-pyridiniumyl is preferably C
1
-C
4
alkyl, most preferably methyl.
C
2
-C
6
Alkenyl is C
2
-C
6
alkyl which is mono- or polyunsaturated, where two or more double bonds, if present, can be isolated or conjugated, for example vinyl, allyl, 2-propen-2-yl, 2-buten-1-yl, 3-buten-1-yl, 1,3-butadien-2-yl, 2-cyclobuten-1-yl, 2-penten-1-yl, 3-penten-2-yl, 2-methyl-1-buten-3-yl, 2-methyl-3-buten-2-yl, 3-methyl-2-buten-1-yl, 1,4-pentadien-3-yl, 2-cyclopenten-1-yl, 2-cyclohexen-1-yl, 3-cyclohexen-1-yl or 2,4-cyclohexadien-1-yl.
C
1
-C
6
Alkyl which is interrupted by oxygen is, for example, 3-

Affiliated with

Also associated with

Rating

Writable and erasable high-density optical storage media does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Writable and erasable high-density optical storage media, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Writable and erasable high-density optical storage media will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2506317