EP0738609B1 - Laser absorbierende ausbleichbare Zusammensetzungen - Google Patents

Laser absorbierende ausbleichbare Zusammensetzungen Download PDF

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Publication number
EP0738609B1
EP0738609B1 EP19960302793 EP96302793A EP0738609B1 EP 0738609 B1 EP0738609 B1 EP 0738609B1 EP 19960302793 EP19960302793 EP 19960302793 EP 96302793 A EP96302793 A EP 96302793A EP 0738609 B1 EP0738609 B1 EP 0738609B1
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Prior art keywords
dye
dyes
thermal imaging
imaging element
element according
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French (fr)
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EP0738609A1 (de
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Ranjan C. Patel
Andrew W. Mott
Robert J.D. Nairne
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3M Co
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Minnesota Mining and Manufacturing Co
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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
    • B41M—PRINTING, DUPLICATING, MARKING, OR COPYING PROCESSES; COLOUR PRINTING
    • B41M5/00—Duplicating or marking methods; Sheet materials for use therein
    • B41M5/26—Thermography ; Marking by high energetic means, e.g. laser otherwise than by burning, and characterised by the material used
    • B41M5/40—Thermography ; Marking by high energetic means, e.g. laser otherwise than by burning, and characterised by the material used characterised by the base backcoat, intermediate, or covering layers, e.g. for thermal transfer dye-donor or dye-receiver sheets; Heat, radiation filtering or absorbing means or layers; combined with other image registration layers or compositions; Special originals for reproduction by thermography
    • B41M5/46—Thermography ; Marking by high energetic means, e.g. laser otherwise than by burning, and characterised by the material used characterised by the base backcoat, intermediate, or covering layers, e.g. for thermal transfer dye-donor or dye-receiver sheets; Heat, radiation filtering or absorbing means or layers; combined with other image registration layers or compositions; Special originals for reproduction by thermography characterised by the light-to-heat converting means; characterised by the heat or radiation filtering or absorbing means or layers
    • B41M5/465—Infrared radiation-absorbing materials, e.g. dyes, metals, silicates, C black
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
    • B41M—PRINTING, DUPLICATING, MARKING, OR COPYING PROCESSES; COLOUR PRINTING
    • B41M5/00—Duplicating or marking methods; Sheet materials for use therein
    • B41M5/26—Thermography ; Marking by high energetic means, e.g. laser otherwise than by burning, and characterised by the material used
    • B41M5/28—Thermography ; Marking by high energetic means, e.g. laser otherwise than by burning, and characterised by the material used using thermochromic compounds or layers containing liquid crystals, microcapsules, bleachable dyes or heat- decomposable compounds, e.g. gas- liberating
    • B41M5/286—Thermography ; Marking by high energetic means, e.g. laser otherwise than by burning, and characterised by the material used using thermochromic compounds or layers containing liquid crystals, microcapsules, bleachable dyes or heat- decomposable compounds, e.g. gas- liberating using compounds undergoing unimolecular fragmentation to obtain colour shift, e.g. bleachable dyes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
    • B41M—PRINTING, DUPLICATING, MARKING, OR COPYING PROCESSES; COLOUR PRINTING
    • B41M5/00—Duplicating or marking methods; Sheet materials for use therein
    • B41M5/26—Thermography ; Marking by high energetic means, e.g. laser otherwise than by burning, and characterised by the material used
    • B41M5/382—Contact thermal transfer or sublimation processes
    • B41M5/385—Contact thermal transfer or sublimation processes characterised by the transferable dyes or pigments
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
    • B41M—PRINTING, DUPLICATING, MARKING, OR COPYING PROCESSES; COLOUR PRINTING
    • B41M5/00—Duplicating or marking methods; Sheet materials for use therein
    • B41M5/26—Thermography ; Marking by high energetic means, e.g. laser otherwise than by burning, and characterised by the material used
    • B41M5/382—Contact thermal transfer or sublimation processes
    • B41M5/392—Additives, other than colour forming substances, dyes or pigments, e.g. sensitisers, transfer promoting agents
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
    • B41M—PRINTING, DUPLICATING, MARKING, OR COPYING PROCESSES; COLOUR PRINTING
    • B41M5/00—Duplicating or marking methods; Sheet materials for use therein
    • B41M5/26—Thermography ; Marking by high energetic means, e.g. laser otherwise than by burning, and characterised by the material used
    • B41M5/382—Contact thermal transfer or sublimation processes
    • B41M5/392—Additives, other than colour forming substances, dyes or pigments, e.g. sensitisers, transfer promoting agents
    • B41M5/395—Macromolecular additives, e.g. binders
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
    • B41M—PRINTING, DUPLICATING, MARKING, OR COPYING PROCESSES; COLOUR PRINTING
    • B41M5/00—Duplicating or marking methods; Sheet materials for use therein
    • B41M5/50—Recording sheets characterised by the coating used to improve ink, dye or pigment receptivity, e.g. for ink-jet or thermal dye transfer recording
    • B41M5/52—Macromolecular coatings
    • B41M5/5227—Macromolecular coatings characterised by organic non-macromolecular additives, e.g. UV-absorbers, plasticisers, surfactants

Definitions

  • the invention relates to heat-sensitive imaging media which are imageable by laser address.
  • IR- emitting lasers such as YAG lasers and laser diodes
  • IR- absorbing dyes and pigments are most commonly used as the photothermal converter, although address at shorter wavelengths, in the visible region, is also possible as described in Japanese Patent Publication No. 51-88016.
  • thermal transfer imaging in which a colourant is transferred from a donor to a receptor in response to heat generated from laser irradiation, including dye diffusion transfer (as described in US-A- 5,126,760), mass transfer of dyed or pigmented layers (as described in JP 63-319192) and ablation transfer of dyes and pigments (as described in US-A-5,171,650 and WO90/12342).
  • laser thermal colour imaging media include those based on the formation or destruction of coloured dyes in response to heat (US-A-4602263), those based on the migration of toner particles into a thermally-softened layer (WO93/04411) and various peel-apart systems wherein the relative adhesion of a coloured layer to a substrate and a coversheet is altered by heat (WO93/03928, WO88/04237, DE4209873).
  • the absorber may be co-transferred with the colourant. Unless the cotransferred absorber has absolutely no absorption bands in the visible part of the spectrum, the colour of the image will be altered.
  • Various attempts have been made to identify IR dyes with minimal visible absorption (e.g., EP-A-0157568), but in practice the IR absorption band nearly always tails into the visible region, leading to contamination of the image.
  • EP-A-0675003 describes contacting the transferred image of laser thermal transfer imaging with a thermal bleaching agent capable of bleaching the absorber. This method complicates the imaging process and it has not been possible to bleach certain dyes, for example, Cyasorb 165TM (American Cyanamid) which is commonly used with YAG-lasers.
  • Cyasorb 165TM American Cyanamid
  • WO93/04411 and US-A-5219703 disclose an acid-generating compound which bleaches the IR absorbing dye.
  • an additional UV exposure is generally required (optionally in the presence of a UV absorber), again complicating the imaging process.
  • a photoexcited dye may accept an electron from a coreactant, the dye acting as a photo-oxidant.
  • this type of process has been used, although not in the context of laser-addressable thermal imaging media.
  • systems comprising a cationic dye in reactive association with an organoborate ion (see US-A-5329300, US-A-5166041, US-A-4447521, US-A-4343891 and J. Chem Soc. Chem Commun 1993 299).
  • organoborate ions fragment into free radicals which may initiate polymerisation reactions (J. Am. Chem. Soc. 1985 (110) 2326-8) or may react further and thus form an image (US-A-4447521 and US-A-4343891).
  • US-A-4816379 Another example of imaging involving photoreduction of a dye is disclosed in US-A-4816379.
  • This describes media comprising a photocurable layer containing a UV photoinitiator and photopolymerisable compounds, the layer additionally comprising a cationic dye of defined structure and a mild reducing agent capable of reducing said dye in its photoexcited state.
  • Imagewise exposure at a wavelength absorbed by the cationic dye causes photoreduction of same and generation of a polymerisation inhibitor, so that a subsequent uniform UV exposure gives polymerisation only in the previously unexposed areas.
  • Conventional wet development leaves a positive image.
  • the cationic dyes are described as visible-absorbing, and are of a type not known to be IR-absorbing.
  • Shifts in the absorbance of the cationic dyes are noted.
  • the preferred reducing agents are salts of N-nitrosocyclohexylhydroxylamine, but other possibilities include ascorbic acid and thiourea derivatives. There is no disclosure of thermal imaging media.
  • EP-A-O515133 and J. Org. Chem 1993 (58), 2614-8 disclose the photoreduction of neutral xanthene dyes by amines and other electron donors, for initiation of polymerisation and in photosynthetic applications.
  • a laser addressable thermal imaging medium comprising a photothermal converting dye in association with a heat-sensitive imaging system and a photoreducing agent, said photoreducing agent bleaching said dye during laser address of the medium.
  • Laser-addressable thermal imaging media refers to imaging media in which an image forms in response to heat, said heat being generated by absorption of coherent radiation (as is emitted by lasers, including laser diodes).
  • the image formed is a colour image
  • the thermal imaging medium is a colourant donor medium.
  • the media must comprise a "photothermal converter", i.e., a substance which absorbs incident radiation with concomitant generation of heat.
  • a dye absorbs radiation, a proportion of its molecules are converted to an electronically excited state, and the basis of photothermal conversion is the dissipation of this electronic excitation as vibrational energy in the surrounding molecules, with the dye molecules reverting to the ground state.
  • the mechanism of this dissipation is not well understood, but it is generally believed that the lifetime of the excited state of the dye is very short (e.g. of the order of picoseconds, as described by Schuster et al., J.Am.Chem.Soc 1990 (112), 6329).
  • a dye molecule might experience many excitation-deexcitation cycles during even the shortest laser pulses normally encountered in laser thermal imaging (of the order of nanoseconds).
  • Photoredox processes in which the photo-excited dye molecules donate or accept an electron to or from a reagent in its ground state. This may initiate further chemical transformations which destroy the dye's ability to undergo further excitation-deexcitation cycles.
  • photoreduction processes in which it is believed a suitable reducing agent donates an electron to fill the vacancy caused in the dye's lower energy orbitals when an electron is promoted to a higher energy orbital by photoexcitation.
  • the process is believed to occur most readily in the case of cationic dyes (which have a positive charge associated with the chromophore), but also has been observed in the case of neutral dyes such as xanthenes (see US-A-4816379, EP-A-0515133) but not in the context of thermal imaging media.
  • the process provides a convenient and effective method of bleaching a laser-absorbing dye without, surprisingly, significantly affecting the dye's ability to act as a photothermal converter.
  • Bleaching in the context of this invention means an effective diminution of absorption bands giving rise to visible colouration by the photothermal converting dye. Bleaching may be achieved by destruction of the aforementioned absorption bands, or by shifting them to wavelengths that do not give rise to visible colouration.
  • dyes suitable for use in the invention include cationic dyes such as polymethine dyes, pyrylium dyes, cyanine dyes, diamine dication dyes, phenazinium dyes, phenoxazinium dyes, phenothiazinium dyes, acridinium dyes, and also neutral dyes such as the xanthene dyes disclosed in EP-A-O515133 and squarylium dyes.
  • Preferred dyes have absorption maxima that match the output of the laser sources most commonly used for thermal imaging such as laser diodes and YAG lasers. Absorption in the range 600 - 1500nm is preferred, and in the range 700 - 1200nm is most preferred.
  • Preferred classes of cationic dyes for use in the invention include the tetraarylpolymethine (TAPM) dyes. These generally absorb in the 700 - 900nm region, making them suitable for diode laser address, and there are several references in the literature to their use as absorbers in laser address thermal transfer media, e.g. JP-63-319191, JP-63-319192 and US-A-4950639. When these dyes are co-transferred with the colourant, a blue cast is given to the transferred image because the TAPM dyes generally have absorption peaks which tail into the red region of the spectrum. European Patent Application No.
  • EP-A-675003 describes the thermal bleaching of TAPM dyes in the thermal transfer media via the provision of thermal bleaching agents in the receptor layer (EP-A 0 675 003 constitutes prior art according to Article 54(3)(4) EPC). It has now been found that TAPM dyes can bleach cleanly by a photoreductive process as described in the present invention.
  • tertiary amino groups include dialkylamino groups, diarylamino groups, and cyclic substituents such as pyrrolidino, morpholino, piperidino.
  • the tertiary amino group may form part of a fused ring system, e.g., one or more of Ar 1 - Ar 4 may represent a julolidine group.
  • the anion X is derived from a strong acid (e.g., HX should have a pKa of less than 3, preferably less than 1).
  • Suitable identities for X include ClO 4 , BF 4 , CF 3 SO 3 , PF 6 , AsF 6 , SbF 6 .
  • amine cation radical dyes also known as immonium dyes, described for example in WO90/12342 and JP51-88016.
  • Cyasorb IR165 American Cyanamid
  • Ar 1 - Ar 4 and X are as defined above.
  • these dyes show peak absorptions at relatively long wavelengths (ca.1050nm, suitable for YAG laser address), the absorption band is broad and tails into the red region.
  • EP-A-0675003 teaches that partial bleaching of diamine di-cation dyes is possible through a thermal process, but it has now been found that total bleaching may be achieved by a photoreductive process.
  • the reducing agent used in the invention may be any compound or group capable of interacting with the photothermal converting dye and bleaching the same under the conditions of photoexcitation and high temperature associated with laser address of thermal imaging media, but must not react with the dye in its ground state under normal storage conditions.
  • the reducing agent acts as a photoreductant towards the dye, i.e. it transfers an electron only to the photoexcited form of the dye, so that the composition is stable in the absence of photoexcitation.
  • the choice of reducing agent may depend on the choice of laser-absorbing dye.
  • Candidate combinations of dye and reducing agent may be screened for suitability by coating mixtures of dye and reducing agent (optionally in a mutually compatible binder) on a transparent substrate, and thereafter monitoring the effect on the absorption spectrum of the dye of (a) storage of the coating in the dark at moderately elevated temperatures for several days, and (b) irradiation of the coating at the absorption maximum of the dye by a laser source.
  • conditions (a) should have minimal effect and conditions (b) should bleach the dye.
  • Reducing agents suitable for use in the invention are generally good electron donors, i.e., have a low oxidation potential (Eox), typically less than 1.0V, and preferably not less than 0.40V.
  • Eox oxidation potential
  • they may be neutral molecules or anionic groups.
  • anionic groups include the salts of N-nitrosocyclohexylhydroxylamine disclosed in US-A-4816379, N-phenylglycine salts and organoborate salts comprising an anion of formula III :- in which:
  • US-A-5166041 describes the photobleaching of a variety of IR-absorbing cationic dyes by such species, but not in the context of laser addressed thermal imaging. Likewise, photobleaching of visible-absorbing cyanine dyes by alkylborate ion is described in US-A-4,447,521, US-A- 4,343,891. Anionic reducing agents may be formulated as the counterion to the cationic dye.
  • Neutral reducing agents suitable for use in the invention generally (but not necessarily) possess one or more labile hydrogen atoms or acyl groups which may be transferred to the dye subsequent to electron transfer, hence effecting irreversible bleaching of the dye.
  • neutral reducing agents include the thiourea derivatives mentioned in US-A-4816379, ascorbic acid, benzhydrols, phenols, amines and leuco dyes (including acylated derivatives thereof). It is highly desirable that the photo-oxidation products of the reducing agent should not themselves be visibly coloured. Surprisingly, in certain cases it has been found possible to employ leuco dyes as reducing agents without generating unwanted colouration.
  • a preferred class of reducing agent comprises the 1,4-dihydropyridine derivatives having a nucleus of general formula IV :- in which:
  • Alkyl refers to alkyl groups of up to 20 preferably up to 10, and most preferably lower alkyl, meaning up to 5 carbon atoms.
  • Aryl refers to aromatic rings or fused ring systems of up to 14, preferably up to 10, most preferably up to 6 carbon atoms.
  • Alicyclic refers to non-aromatic rings or fused ring systems of up to 14, preferably up to 10, most preferably up to 6 carbon atoms.
  • Heterocyclic refers to aromatic or non-aromatic rings or fused ring systems of up to 14, preferably up to 10, most preferably up to 6 atoms selected from C, N, 0 and S. As is well understood in this technical area, a large degree of substitution is not only tolerated, but is often advisable. As a means of simplifying the discussion, the terms, “nucleus”, “groups” and “moiety” are used to differentiate between chemical species that allow for substitution or which may be substituted and those which do not or may not be so substituted.
  • alkyl group is intended to include not only pure hydrocarbon alkyl chains, such as methyl, ethyl, octyl, cyclohexyl, iso-octyl, t-butyl and the like, but also alkyl chains bearing conventional substitutents known in the art, such as hydroxyl, alkoxy, phenyl, halogen (F, Cl, Br and I), cyano, nitro, amino etc.
  • substitutents such as hydroxyl, alkoxy, phenyl, halogen (F, Cl, Br and I), cyano, nitro, amino etc.
  • the term “nucleus” is likewise considered to allow for substitution.
  • alkyl moiety on the other hand is limited to the inclusion of only pure hydrocarbon alkyl chains, such as methyl, ethyl, propyl, cyclohexyl, iso-octyl, t-butyl etc.
  • Z is preferably an oxygen atom
  • R 5 is preferably H or phenyl (optionally substituted)
  • R 6 is preferably phenyl (optionally substituted)
  • R 7 is preferably lower alkyl (esp. methyl)
  • R 8 is preferably lower alkyl (e.g., ethyl).
  • the compound of formula IV or other reducing agent is typically coated in the same layer or layers as the dye, but may additionally or alternatively be present in one or more separate layers, provided that reactive association of the dye and reducing agent is possible during the photoirradiation. Absorption of laser pulses can cause extremely rapid rises in temperature and pressure, which may readily enable the ingredients of two or more adjacent layers to mix and interact.
  • At least one mole of reducing agent is present per mole of dye, but more preferably an excess is used, e.g., in the range of 5 - 50-fold.
  • a metal salt stabiliser may be incorporated, e.g., a magnesium salt, as this has been found to improve the thermal stability of the system without affecting the photoactivity. Quantities of about 10 mole% based on the compound of formula IV are effective.
  • the laser-addressable thermal imaging media may comprise any imaging media in which photothermal conversion is used to generate an image, but the invention finds particular use with media which generate a colour image which may be altered by the presence of unbleached photothermal converting dye.
  • Such media may take several forms, such as colourant transfer systems, peel-apart systems, phototackification systems and systems based on unimolecular thermal fragmentations of specific compounds.
  • Preferred laser addressable thermal imaging media include the various types of laser thermal transfer media.
  • a donor sheet comprising a layer of colourant and a suitable absorber is placed in contact with a receptor and the assembly exposed to a pattern of radiation from a scanned laser source.
  • the radiation is absorbed by the absorber, causing a rapid buildup of heat in the exposed areas of the donor which in turn causes transfer of colourant from those areas to the receptor.
  • a multicolour image can be assembled on a common receptor.
  • the system is particularly suited to the colour proofing industry, where colour separation information is routinely generated and stored electronically, and the ability to convert such data into hardcopy via digital address of "dry" media is particularly advantageous.
  • the heat generated may cause colourant transfer by a variety of mechanisms.
  • the colourant and associated binder materials may transfer in a molten state (“melt-stick transfer”), as described in JP63-319191. Both of these mechanisms produce mass transfer, i.e. there is essentially 0% or 100% transfer of colourant depending on whether the applied energy exceeds a certain threshold.
  • a somewhat different mechanism is diffusion or sublimation transfer, whereby a colourant is diffused (or sublimed) to the receptor without co-transfer of binder. This is described, for example, in US-A-5126760, and enables the amount of colourant transferred to vary continuously with the input energy.
  • the donor may be adapted for sublimation transfer, ablation transfer, or melt-stick transfer.
  • the donor element comprises a substrate (such as polyester sheet), a layer of colourant, a dye (preferably cationic) as photothermal converter and a reducing agent.
  • the dye and reducing agent may be in the same layer as the colourant, in one or more separate layers, or both.
  • Other layers may be present, such as dynamic release layers as taught in US-A-5171650.
  • the donor may be self-sustaining, as taught in EP-A-0491564.
  • the colourant comprises dyes or pigments that reproduce the colours shown by standard printing ink references provided by the International Prepress Proofing Association, known as SWOP colour references.
  • Particularly preferred donor elements are of the type described in EP-A-0602893 in which the colourant layer comprises a fluorocarbon compound in addition to pigment and binder.
  • the receptor elements used in the present invention are entirely conventional. Thus, they typically comprise a substrate such as paper or plastic sheet optionally bearing one or more resin coatings.
  • the choice of the resin for the receptor layer may depend on the type of transfer involved (ablation, melt-stick, or sublimation), but for use with the preferred donor elements, ButvarTM B76 polyvinyl butyral (Monsanto), polyvinyl resins, and similar thermoplastic materials are highly suitable.
  • the procedure for imagewise transfer of colourant from donor to receptor is entirely conventional.
  • the two elements are assembled in intimate face-to-face contact, e.g., by vacuum draw down, or alternatively by means of cylindrical lens apparatus as described in US-A-5475418, and scanned by a suitable laser.
  • the assembly may be imaged by any of the commonly-used lasers, depending on the absorber used, but address by near infrared and infrared emitting lasers such as diode lasers and YAG lasers, is preferred. Best results are obtained from a relatively high intensity laser exposure, e.g., of at least 10 23 photons/cm 2 /sec.
  • a laser diode emitting at 830nm this corresponds approximately to an output of 0.1W focused to a 20 micron spot with a dwell time of approximately 1 microsecond.
  • a flux of at least 3X10 24 photons/cm 2 /sec is preferred, corresponding roughly to an output of 2W focused to a 20 micron spot, with a dwell time of approximately 0.1 microsecond.
  • any of the known scanning devices may be used, e.g., flat-bed scanners, external drum scanners or internal drum scanners.
  • the assembly to be imaged is secured to the drum or bed (e.g., by vacuum draw-down) and the laser beam is focused to a spot (e.g., of about 10-25, preferably about 20 microns diameter) on the IR-absorbing layer of the donor.
  • This spot is scanned over the entire area to be imaged while the laser output is modulated in accordance with electronically stored image information.
  • Two or more lasers may scan different areas of the donor-receptor assembly simultaneously, and if necessary, the output of two or more lasers may be combined optically into a single spot of higher intensity.
  • Laser address is normally from the donor side, but may alternatively be from the receptor side if the receptor is transparent to the laser radiation. Peeling apart the donor and receptor reveals a monochrome image on the receptor. The process may be repeated one or more times using donor sheets of different colours to build a multicolour image on a common receptor. Because of the interaction of the photothermal converting dye and reducing agent during laser address, the final image can be free from contamination by the photothermal converter. In some situations, the receptor to which the colourant image is initially transferred is not the final substrate on which the image is viewed. For example, US-A-5126760 describes thermal transfer of the image from the first receptor to a second receptor for viewing purposes.
  • thermoplastic imaging media An alternative type of laser addressable thermal imaging media suitable for use in the present invention is an adaptation of the migration imaging described in WO93/04411. As detailed therein, this involves deposition of marking particles as a substantially continuous layer on a thermoplastic imaging element and establishing an attraction between the two (e.g., by electrostatic charging).
  • the particles, the thermoplastic imaging element, or both contain an IR absorbing dye such that when the assembly is imagewise exposed by a laser, softening of the thermoplastic element occurs, allowing the marking particles to migrate therein under the force of attraction and become embedded on subsequent cooling. Particles are removed from the non-image areas by wiping or other suitable means.
  • An acid-generating compound such as an iodonium salt, is incorporated in the particles, the thermoplastic element or both to enable bleaching of the IR dye either during laser address or (more effectively) by uniform UV exposure as an additional step.
  • This type of media may be adapted to the present invention by use of a dye in the marking particles as laser absorber, with a reducing agent present in the particles and/or the thermoplastic element. Effective bleaching of the laser absorber is then possible without the need for further UV exposure.
  • laser thermal colour imaging media within the scope of the present invention include those based on the formation or destruction of coloured dyes in response to heat (as described in US4602263), and various peel-apart systems wherein the relative adhesion of a coloured layer to a substrate and a coversheet is altered by heat (as described in WO93/03928, WO88/04237, DE4209873).
  • This example demonstrates the photoreductive bleaching of Dyes 1 and 2 by Donors 1 (a) and 2.
  • Elements 1 and 2 were pale blue/pink in appearance and Elements 3 and 4 pale grey.
  • Samples measuring 5cm x 5cm were mounted on a drum scanner and exposed by a 20 micron laser spot scanned at various speeds.
  • the source was either a laser diode delivering 115mW at 830nm at the image plane(Elements 1 and 2), or a YAG laser delivering 2W at 1068nm (Elements 3 and 4).
  • Donor 2 which may be regarded as an aroyl-protected leuco dye, did not give rise to any colouration attributable to the corresponding dye.
  • the example demonstrates thermal transfer media in accordance with the invention.
  • a millbase was prepared by dispersing 4g magenta pigment chips in 32g MEK using a McCrone Micronising Mill.
  • the pigment chips were prepared by standard procedures and comprised blue shade magenta pigment and VAGH binder in a weight ratio of 3:2.
  • the elements of the invention show much reduced contamination by the IR dye, and purer magenta images were obtained.

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  • Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Heat Sensitive Colour Forming Recording (AREA)
  • Thermal Transfer Or Thermal Recording In General (AREA)

Claims (17)

  1. Laseransprechbares thermisches Bildaufzeichnungselement, umfassend einen bleichbaren photothermischen Konversionsfarbstoff in Kombination mit einem wärmeempfindlichen Bildaufzeichnungsmedium und ein Photoreduktionsmittel für den Farbstoff, wobei das Photoreduktionsmittel den Farbstoff ausbleicht, wenn das Element von einem Laser angesprochen wird.
  2. Thermisches Bildaufzeichnungselement gemäß Anspruch 1, wobei der Farbstoff ein Absorptionsmaximum im Bereich von 600 bis 1500 nm aufweist.
  3. Thermisches Bildaufzeichnungselement gemäß Anspruch 1 oder 2, wobei der Farbstoff ein kationischer Farbstoff oder ein neutraler Farbstoff ist.
  4. Thermisches Bildaufzeichnungselement gemäß Anspruch 3, wobei der Farbstoff ausgewählt ist aus Polymethinfarbstoffen, Pyryliumfarbstoffen, Cyaninfarbstoffen, Diamindikationfarbstoffen, Phenazinfarbstoffen, Phenoxazinfarbstoffen, Acridinfarbstoffen, Xanthenfarbstoffen und Quadratsäurefarbstoffen.
  5. Thermisches Bildaufzeichnungselement gemäß Anspruch 4, wobei der Farbstoff die Formel:
    Figure 00270001
    Figure 00280001
    aufweist, wobei Ar1 bis Ar4 unabhängig voneinander Arylreste darstellen, so daß mindestens zwei aus Ar1 bis Ar4 eine tertiäre Aminogruppe in Position 4 besitzen und wobei X ein Anion ist.
  6. Thermisches Bildaufzeichnungselement gemäß Anspruch 5, wobei die tertiäre Aminogruppe aus Dialkylaminogruppen, Diarylaminogruppen oder cyclischen Substituenten, ausgewählt aus Pyrrolidino-, Morpholino- oder Piperidinogruppen ausgewählt ist oder einen Teil eines kondensierten Ringsystems darstellt und wobei X ClO4, BF4, CF3SO3, PF6, AsF6 oder SbF6 ist.
  7. Thermisches Bildaufzeichnungselement gemäß einem der vorstehenden Ansprüche, wobei das Reduktionsmittel ausgewählt ist aus Verbindungen mit einem Kern der Formel
    Figure 00280002
    wobei:
    R5 ausgewählt ist aus H, Alkyl-, Aryl-, alicyclischen oder heterocyclischen Resten;
    R6 einen Arylrest darstellt;
    R7 und R8 jeweils unabhängig voneinander ausgewählt sind aus Alkyl-, Aryl-, alicyclischen und heterocyclischen Resten, und
    Z eine kovalente Bindung oder ein Sauerstoffatom darstellt; und
    Salzen von N-Nitrosocyclohexylhydroxylamin, N-Phenylglycin und Organoboratsalzen, umfassend ein Anion der Formel
    Figure 00290001
    in der R1 bis R4 unabhängig voneinander Alkyl-, Aryl-, Alkaryl-, Aralkyl-, Alkenyl-, Alkinyl-, Silyl-, alicyclische oder gesättigte oder ungesättigte heterocyclische Reste darstellen, einschließlich substituierte Derivate dieser Reste mit der Maßgabe, daß mindestens einer der Reste R1 bis R4 ein Alkylrest mit bis zu 8 Kohlenstoffatomen ist; und
    neutralen Reduktionsmitteln, die ein oder mehrere labile Wasserstoffatome oder Acylreste aufweisen.
  8. Thermisches Bildaufzeichnungselement gemäß Anspruch 7, wobei R5 H oder eine Phenylgruppe ist, R6 eine Phenylgruppe ist, R7 und R8 niedere Alkylreste sind.
  9. Thermisches Bildaufzeichnungselement gemäß Anspruch 7, wobei das neutrale Reduktionsmittel ausgewählt ist aus Thioharnstoffderivaten, Ascorbinsäure, Benzhydrolen, Phenolen, Aminen und Leukofarbstoffen und acylierten Derivaten davon.
  10. Thermisches Bildaufzeichnungselement gemäß einem der vorstehenden Ansprüche, wobei mindestens 1 Mol Reduktionsmittel pro Mol Farbstoff anwesend ist.
  11. Thermisches Bildaufzeichnungselement gemäß einem der Ansprüche 1 bis 7, umfassend eine der folgenden Kombinationen eines Photokonversionsfarbstoffes und eines Photoreduktionsmittels:
    (i) ein Farbstoff der Formel (I) oder Formel (II) wie in Anspruch 5 definiert und ein Reduktionsmittel der Formel (IV) wie in Anspruch 7 definiert;
    (ii) ein kationischer Farbstoff und ein Reduktionsmittel der Formel (III) wie in Anspruch 7 definiert; und
    (iii) ein Cyanin- oder Quadratsäurefarbstoff und ein acylgeschützter Leukofarbstoff.
  12. Thermisches Bildaufzeichnungselement gemäß einem der vorstehenden Ansprüche, wobei das Element ein Farbstoffübertragungssystem, ein Abziehsystem, ein lichtaktivierbares Klebesystem oder ein unimolekulares thermisches Fragmentationssystem ist.
  13. Thermisches Bildaufzeichnungselement gemäß Anspruch 12 in Form eines Farbstoffübertragungsdonors, welches Pigmentpartikel in einem Binder dispergiert umfaßt.
  14. Thermisches Bildaufzeichnungselement gemäß Anspruch 13, welches zusätzlich ein Fluorkohlenstoff umfaßt.
  15. Bildaufzeichnungsverfahren, umfassend einen Schritt, in dem ein thermisches Bildaufzeichnungselement gemäß einem der vorstehenden Ansprüche Laserbestrahlung bei einer Wellenlänge, die der photothermische Konversionsfarbstoff absorbiert, ausgesetzt wird, wobei die Bedingungen der Aussetzung so gewählt werden, daß die Absorption durch den Farbstoff ausreichend Wärme erzeugt, um ein Bild auf dem hitzeempfindlichen Bildaufzeichnungsmedium zu erzeugen, und das Reduktionsmittel den Farbstoff bleicht.
  16. Verfahren gemäß Anspruch 15, wobei das thermische Bildaufzeichnungselement ein Farbstofftransfersystem, ein Abziehsystem, ein lichtaktivierbares Klebesystem oder ein unimolekulares thermisches Fragmentationssystem umfaßt.
  17. Verfahren zum Bleichen eines kationischen Farbstoffes, umfassend photobestrahlung des Farbstoffes, wobei der Farbstoff in einen elektronisch angeregten Zustand übergeht, in Gegenwart eines 1,4-Dihydropyridins mit einem Kern der allgemeinen Formel IV:
    Figure 00310001
    wobei
    R5 ausgewählt ist aus H, Alkyl-, Aryl-, alicyclischen und heterocyclischen Resten;
    R6 einen Arylrest darstellt; und
    R7 und R8 unabhängig voneinander ausgewählt sind aus Alkyl-, Aryl-, alicyclischen und heterocyclischen Resten,
    und
    Z eine kovalente Bindung oder ein Sauerstoffatom darstellt.
EP19960302793 1995-04-20 1996-04-19 Laser absorbierende ausbleichbare Zusammensetzungen Expired - Lifetime EP0738609B1 (de)

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Cited By (3)

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Publication number Priority date Publication date Assignee Title
US5945249A (en) 1995-04-20 1999-08-31 Imation Corp. Laser absorbable photobleachable compositions
DE10054803A1 (de) * 2000-11-04 2002-05-29 Kurz Leonhard Fa Kunststoffkörper, insbesondere massiver Kunststoffkörper oder Folie, z. B. Transferfolie oder Laminierfolie sowie Verfahren zur Herstellung eines Mehrfarbenbildes auf oder in einem solchen Kunststoffkörper
US7300694B2 (en) 2000-11-04 2007-11-27 Leonard Kurz Gmbh & Co. Kg Multilayer body with a first laser-sensitive layer and a second laser-sensitive layer and method for generation of a multilayer image in said multilayer body

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GB9617416D0 (en) * 1996-08-20 1996-10-02 Minnesota Mining & Mfg Thermal bleaching of infrared dyes
DE10011486A1 (de) * 1999-08-30 2001-03-01 Orga Kartensysteme Gmbh Kartenförmiger Datenträger und Verfahren zu seiner Herstellung
DE50011863D1 (de) * 1999-08-30 2006-01-19 Orga Kartensysteme Gmbh Kartenförmiger datenträger und verfahren zu seiner herstellung
EP1501983B1 (de) * 2002-05-08 2017-12-20 U-NICA Technology AG Mehrschichtenkörper mit einer lasersensitiven schicht
US7198879B1 (en) * 2005-09-30 2007-04-03 Eastman Kodak Company Laser resist transfer for microfabrication of electronic devices
US8257906B2 (en) * 2006-03-29 2012-09-04 Hewlett-Packard Development Company, L.P. Multi-layered radiation imageable coating

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GB8913444D0 (en) * 1989-06-12 1989-08-02 Minnesota Mining & Mfg Thermal dye bleach construction
GB9109948D0 (en) * 1991-05-08 1991-07-17 Minnesota Mining & Mfg Negative-acting thermographic materials
US5219703A (en) * 1992-02-10 1993-06-15 Eastman Kodak Company Laser-induced thermal dye transfer with bleachable near-infrared absorbing sensitizers
GB9225724D0 (en) * 1992-12-09 1993-02-03 Minnesota Mining & Mfg Transfer imaging elements
GB9406175D0 (en) * 1994-03-29 1994-05-18 Minnesota Mining & Mfg Thermal transfer imaging

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5945249A (en) 1995-04-20 1999-08-31 Imation Corp. Laser absorbable photobleachable compositions
US6171766B1 (en) 1995-04-20 2001-01-09 Imation Corp. Laser absorbable photobleachable compositions
US6291143B1 (en) 1995-04-20 2001-09-18 Imation Corp. Laser absorbable photobleachable compositions
DE10054803A1 (de) * 2000-11-04 2002-05-29 Kurz Leonhard Fa Kunststoffkörper, insbesondere massiver Kunststoffkörper oder Folie, z. B. Transferfolie oder Laminierfolie sowie Verfahren zur Herstellung eines Mehrfarbenbildes auf oder in einem solchen Kunststoffkörper
US7300694B2 (en) 2000-11-04 2007-11-27 Leonard Kurz Gmbh & Co. Kg Multilayer body with a first laser-sensitive layer and a second laser-sensitive layer and method for generation of a multilayer image in said multilayer body

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DE69600857T2 (de) 1999-06-17
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EP0738609A1 (de) 1996-10-23

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