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
• • 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
  • B41M5/38207—Contact thermal transfer or sublimation processes characterised by aspects not provided for in groups B41M5/385 - B41M5/395
• • 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
  • 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
  • B41M5/26—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

Definitions

• the present invention relates to the formation of a heat mode image.
• Conventional photographic materials based on silver halide are used for a large variety of applications. For instance, in the pre-press sector of graphic arts rather sensitive camera materials are used for obtaining screened images. Scan films are used for producing colour separations from multicolour originals.
• Phototype setting materials record the information fed to phototype- and image setters. Relative insensitive photographic materials serve as duplicating materials usually in a contact exposure process. Other fields include materials for medical recording, duplicating and hard copy, X-ray materials for non-destructive testing, black-and-white and colour materials for amateur- and professional still photography and materials for cinematographic recording and printing.
• Silver halide materials have the advantage of high potential intrinsic sensitivity and excellent image quality. On the other hand they show the drawback of requiring several wet processing steps employing chemical ingredients which are suspect from an ecological point of view.
• a dry imaging system known since quite a while is 3M's dry silver technology. It is a catalytic process which couples the light-capturing capability of silver halide to the image-forming capability of organic silver salts.
• Non-conventional materials as alternative for silver halide is based on photopolymerisation.
• photopolymerizable compositions for the production of images by information-wise exposure thereof to actinic radiation is known since quite a while. All these methods are based on the principle of introducing a differentiation in properties between the exposed and non-exposed parts of the photopolymerizable composition e.g. a difference in solubility, adhesion, conductivity, refractive index, tackiness, permeability, diffusibility of incorporated substances e.g. dyes etc..
• thermographic materials When the heat pattern is applied directly by means of a thermal head such elements are called thermographic materials. When the heat pattern is applied by the transformation of intense laser light into heat these elements are called heat mode materials or thermal imaging media. They offer the advantage in addition to an ecological advantage that they do not need to be handled in a dark room nor is any other protection from ambient light needed.
• Heat mode recording materials based on change of adhesion, are disclosed in e.g. US-P 4,123,309, US-P 4,123,578, US-P 4,157,412, US-P 4,547,456 and PCT publ. Nos.
• such a thermal imaging medium comprises a transparent support and an imaging layer containing carbon black, optionally additional layers and a stripping sheet.
• an imaging layer containing carbon black By the conversion of intense laser light into heat on information-wise exposure a surface part of the support liquefies and firmly locks the carbon black, so that after delamination a negative carbon black image is formed on the support.
• the laser exposure In order to obtain a sufficient development of heat the laser exposure must be performed through the transparent support so that the heat can be generated on the interface support/carbon layer.
• Still other heat mode image forming systems are based on ablation. Usually in these systems the recorded image is transferred to an acceptor sheet. As a consequence such an acceptor must be applied by lamination before the recording step, as disclosed e.g. in US 4,245,003.
• the image forming parts are image-wise released from a top carrier, as disclosed e.g. in unexamined Japanes patent publication JP-A 56-117965.
• a second foil must be applied before recording. This has as a consequence that the final image quality can be gravely deteriorated by physical defects, such as the occurence of pinholes, resulting from lamination faults or contact problems between acceptor and donor during recording. Furtheron most systems based on ablation suffer from too high a minimum density in the final image.
• the present invention extends the teaching of image formation based on heat mode.
• the objects of the present invention are realized by providing a method for the formation of a heat mode image comprising the following steps :
• the image forming substance is carbon black being at the same time the radiation to heat converting substance.
• the basic idea of the present invention is as follows. If it is not necessary to apply a laminate before laser exposure the above cited problems in connection with physical defects will not occur. Instead of applying a laminate a top layer is coated which has a very strong adhesion to the laser absorbing image forming layer. By intense laser exposure through the coated side (contrary to the embodiments of e.g. WO 88/04237 and WO 95/00342) the adhesion of this top layer to the image forming layer is lowered to a level below the adhesion of the image forming layer to the support. In this way an image-wise release in the exposed areas of the image forming layer from the top adhesive layer occurs.
• compositions of the different layers will now be discussed in detail.
• polyethylene terephthalate PET
• other transparent polymeric resins e.g. polycarbonate, polyvinylchloride, polyethylene, polypropylene or polystyrene can be used.
• the polymeric support is preferably unsubbed ; otherwise the easy removal of the unexposed parts would seriouly be hampered.
• an opaque support such as polyethylene- or polypropylene coated paper can be used, but most preferably the support is transparent. In this way the finished image can serve as intermediate for a further copying step or for exposure of a printing plate.
• the image forming substance is preferably a pigment, e.g. a magnetic pigment, e.g. iron oxides, a coloured piment, e.g. copper phtalocyanine, or metal particles.
• a pigment e.g. a magnetic pigment, e.g. iron oxides, a coloured piment, e.g. copper phtalocyanine, or metal particles.
• the most preferred pigment is carbon black. It can be used in the amorphous or in the graphite form.
• the preferred average particle size of the carbon black ranges from 0.01 to 1 ⁇ m. Different commercial types of carbon black can be used, preferably with a very fine average particle size, e.g.
• the image forming substance and the compound transforming intense laser radiation into heat is one and the same product.
• the image forming substance is another compound not absorptive for the laser radiation, which is preferably infra-red laser radiation
• an extra compound, preferably an infra-red absorbing compound is required for transforming the radiation into heat.
• This infra-red absorbing compound can be a soluble infra-red absorbing dye or a dispersable infrared absorbing pigment.
• Infra-red absorbing compounds are known since a long time and can belong to several different chemical classes, e.g. indoaniline dyes, oxonol dyes, porphine derivatives, anthraquinone dyes, merostyryl dyes, pyrylium compounds and squarylium derivatives.
• a suitable infra-red dye can be chosen from the numerous disclosures and patent applications in the field, e.g., from US-Patent No's 4,886,733, 5,075,205, 5,077,186, 5,153,112, 5,244,771, from Japanese unexamined patent publications (Kokai) No.'s 01-253734, 01-253735, 01-253736, 01-293343, 01-234844, 02-3037, 02-4244, 02-127638, 01-227148, 02-165133, 02-110451, 02-234157, 02-223944, 02-108040, 02-259753, 02-187751, 02-68544, 02-167538, 02-201351, 02-201352, 03-23441, 03-10240, 03-10239, 03-13937, 03-96942, 03-217837, 03-135553, 03-235940, and from the European published patent applications publ.
• binders for the image forming layer (b) gelatin polyvinylpyrrolidone, polyvinylalcohol, nitrocellulose, hydroxyethylcellulose, polyethyleneoxide and a broad variety of polymer latices can be considered. These latices can be film forming or non-film forming. They can comprise acid groups as a result of which they can swell in an alkaline coating medium and/or become totally or partially soluble. In this way the layer properties can be strongly influenced, e.g. less coating and drying point defects will appear. When choosing a particular type of carbon black and a particular type of polymeric binder the ratio of the amounts of both has to be optimized for each case.
• Preferred binders are copolymers of ethylacrylate, methylacrylate and methacrylic acid. Another preferred binder is nitrocellulose.
• the thickness of the image forming layer is preferably comprised between 0.5 and 1.5 micron.
• the adhesive layer (c) can contain a permanent adhesive, also called pressure-sensitive adhesive polymer, or a thermoadhesive, also called heat-sensitive polymer.
• a permanent adhesive also called pressure-sensitive adhesive polymer
• a thermoadhesive also called heat-sensitive polymer.
• pressure-sensitive adhesive resins are described in US-P 4,033,770 for use in the production of adhesive transfers (decalcomanias) by the silver complex diffusion transfer process, in the Canadian Patent 728,607 and in the United States Patent 3,131,106.
• Pressure-sensitive adhesives are usually composed of (a) thermoplastic polymer(s) having some elasticity and tackiness at room temperature (about 20°C), which is controlled optionally with a plasticizer and/or tackifying resin.
• a thermoplastic polymer is completely plastic if there is no recovery on removal of stress and completely elastic if recovery is instantaneous and complete.
• Particularly suitable pressure-sensitive adhesives are selected from the group of polyterpene resins, low density polyethylene, a copoly(ethylene/vinyl acetate), a poly(C 1 -C 16 )alkyl acrylate, a mixture of poly(C 1 -C 16 )alkyl acrylate with polyvinyl acetate, and copoly(vinylacetate-acrylate) being tacky at 20°C.
• an intrinsically non-tacky polymer may be tackified by the adding of a tackifying substance, e.g. plasticiser or other tackifying resin.
• a tackifying substance e.g. plasticiser or other tackifying resin.
• tackifying resins examples include the terpene tackifying resins described in the periodical "Adhesives Age", Vol. 31, No. 12, November 1988, p. 28-29.
• the adhesive layer (c) is a thermal adhesive layer (or thermoadhesive layer, or TAL) it contains one or more thermoadhesive polymers having a glass transition temperature T g preferably comprised between 20 and 60 °C.
• T g glass transition temperature
• the polymers are preferably incorporated as latices.
• Other additives can be present into the TAL to improve the layer formation or the layer properties, e.g. thickening agents, surfactants, levelling agents, thermal solvents and pigments.
• Preferred latices are styrene-butadiene latices. These latices can contain other comonomers which improve the stablitity of the latex, such as acrylic acid, methacrylic acid and acrylamide.
• Other possible polymer latices include polyvinylacetate, copoly(ethylene-vinylacetate), copoly(acrylonitrile-butadiene-acrylic acid), copoly(styrene-butylacrylate), copoly(methylmethacrylate-butadiene), copoly(methylmethacrylate-butylmethacrylate), copoly(methylmethacrylate-ethylacrylate), copolyester(terephtalic acid-sulphoisophtalic acid-ethyleneglycol), copolyester(terephtalic acid-sulphoisophtalic acid-hexanediol-ethyleneglycol).
• Particularly suitable polymers for use in the TAL layer are the BAYSTAL polymer types, marketed by Bayer AG, which are on the basis of styrene-butadiene copolymers. Different types with different physical properties are available. The styrene content varies between 40 and 80 weight %, while the amount of butadiene varies between 60 and 20 weight % ; optionally a few weight % (up to about 10 %) of acrylamide and/or acrylic acid can be present. Most suited are e.g. BAYSTAL KA 8558, BAYSTAL KA 8522, BAYSTAL S30R and BAYSTAL P1800 because they are not sticky at room temperature when used in a TAL layer. Other useful polymers are the EUDERM polymers, also from Bayer AG, which are copolymers comprising n.-butylacrylate, methylmethacrylate, acrylonitrile and small amounts of methacrylic acid.
• the (thermo)adhesive layer must be sufficiently thick so that most part of it remains intact after intense layer exposure. A thickness higher than 5 ⁇ m is preferred.
• the information-wise and/or overall scanning laser exposure can be performed by an Ar ion laser, a HeNe laser, a Kr laser, a frequency doubled Nd-YAG laser, a dye laser emitting in the visual spectral region.
• the laser is an infra-red laser.
• semiconductor diode lasers or solid state lasers such as a Nd-YAG laser emitting at 1064 nm, or a Nd-YLF laser emitting at 1053 nm.
• Other possible infra-red laser types include diode lasers emitting at 823 nm or diode lasers emitting at 985 nm.
• Important parameters of the laser recording are the spot diameter (D) measured at the 1/e 2 value of the intensity, the applied laser power on the film (P), the recording speed of the laser beam (v) and the number of dots per inch (dpi).
• the adhesive strenght of the (thermo)adhesive layer towards the image forming layer is lowered to a value below the adhesive strenght of this image forming layer towards the support. In this way the image forming layer is image-wise released from the top adhesive layer.
• a stripping sheet is laminated on top of the (thermo)adhesive layer.
• this cleaning foil is transparent it may be composed of any of the same polymeric resins suitable for use as support.
• the support (a) a polyethylene terephthalate sheet is preferred. Its thickness if preferably comprised between 10 and 200 ⁇ m. Preferably it is somewhat thinner than the support for ecological reasons.
• the stripping sheet may also be an opaque paper sheet.
• Lamination may be conducted by putting the two materials in contact and then introducing the materials into the nip of a pair of laminating rollers under suitable pressure.
• suitable laminating temperatures usually range from approximately 60°C to 100°C, preferably from 70°C to 90°C.
• the delamination can be performed manually or in a delamination apparatus.
• the stripping layer is held planar and the medium is peeled off at an angle of about 180° at a speed of about 10 m/min.
• the heat mode image can be used as a master for the exposure of a printing plate or a graphic arts contact material.
• a thermal imaging medium was prepared as follows. Onto an unsubbed polyethylene terephthalate support having a thickness of 100 ⁇ m a carbon black containing image forming layer (C-layer) was coated from an aqueous medium. On top of this layer a thermoadhesive layer (TAL) was coated. The composition of both layers after drying is represented in table 1.
• This thermal imaging medium was exposed information-wise to intense laser radiation according to the following specifications :
• a paper stripping sheet (Ideal Brillant Blanc Paper) was laminated on top of the exposed thermal imaging medium at 85 °C at a speed of 0.5 m/min. Then this stripping sheet was kept flat and the film was delaminated at an angle of 180° with a speed of 10 m/min approximately. The exposed areas of the carbon layer adhered to the original support giving rise there to a negative heat mode image while the unexposed aeras of the carbon layer were removed together with the thermoadhesive layer and the stripping sheet.
• the Dmax values in the full areas of the obtained negative image were 4.5 (visual filter) and 5.0 (UV filter).
• the Dmin values were 0.05 (visual) and 0.07 (UV). A resolution up to a 10 ⁇ m dot could be obtained.
• stripping sheet was a subbed polyethylene terephthalate foil having a thickness of 100 ⁇ m.
• a heat mode image with similar good properties as in the previous example was obtained.

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• Physics & Mathematics (AREA)
• Optics & Photonics (AREA)
• Electronic Switches (AREA)
• Thermal Transfer Or Thermal Recording In General (AREA)

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Cited By (2)

Citations (5)

• 1996
  • 1996-02-16 EP EP96200410A patent/EP0790137A1/de not_active Withdrawn

Patent Citations (5)

Non-Patent Citations (1)

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