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
  • B41M5/24—Ablative recording, e.g. by burning marks; Spark recording
• • 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
  • B41M5/42—Intermediate, backcoat, or covering layers

Definitions

• the present invention relates to an improved heat mode recording element containing a thin metal recording layer.
• Recording materials have been disclosed on which records are made thermally by the use of intense radiation like laser beams having a high energy density.
• information is recorded by creating differences in reflection and/or in transmission optical density on the recording layer.
• the recording layer has high optical density and absorbs radiation beams which impinge thereon.
• the conversion of radiation into heat brings about a local temperature rise, causing a thermal change such as evaporation or ablation to take place in the recording layer.
• the irradiated parts of the recording layer are totally or partially removed, and a difference in optical density is formed between the irradiated parts and the unirradiated parts (cf. US Pat. Nos. 4,216,501, 4,233,626, 4,188,214 and 4,291,119 and British Pat. No. 2,026,346)
• the recording layer of such heat mode recording materials is usually made of metals, dyes, or polymers. Recording materials like this are described in 'Electron, Ion and Laser Beam Technology", by M. L. Levene et al.; The Proceedings of the Eleventh Symposium (1969); “Electronics” (Mar. 18, 1968) , P. 50; “The Bell System Technical Journal”, by D. Maydan, Vol. 50 (1971), P. 1761; and “Science”, by C. O. Carlson, Vol. 154 (1966), P. 1550.
• DRAW direct read after write
• Human readable records are e.g. micro-images that can be read on enlargement and projection.
• An example of a machine readable DRAW recording material is the optical disc.
• tellurium and its alloys have been used most widely to form highly reflective thin metal films wherein heating with laser beam locally reduces reflectivity by pit formation (ref. e.g. the periodical 'Physik in phy Zeit', 15. Jahrg. 1984/Nr. 5, 129-130 the article "Optische aside” by Jochen Fricke).
• Tellurium is toxic and has poor archival properties because of its sensitivity to oxygen and humidity.
• Other metals suited for use in DRAW heat-mode recording are given in US-P-4499178 and US-P-4388400.
• Other relatively low melting metals such as bismuth have been introduced in the production of a heat-mode recording layer.
• Heat mode recording materials usually do not require development and fixing processes and do not require darkroom operations because of their insensitivity to room light. Therefore they constitute a valuable alternative to conventional photosensitive materials based on silver halide emulsions, e.g. for phototype-setting or image-setting applications.
• silver halide materials have the advantage of high potential intrinsic sensitivity and excellent image quality.
• they show the drawback of requiring several wet processing steps employing chemical ingredients which are suspect from an ecological point of view. For instance the commonly used developing agent hydroquinone is allergenic and the biodegradation of disposed phenidone is too slow. As a consequence it is undesirable that depleted solutions of this kind would be discharged into the public sewerage; they have to be collected and destroyed by combustion, a cumbersome and expensive process.
• a heat mode recording element comprising, in order :
• the metal layer is a vacuum-deposited thin bismuth layer having a thickness preferably comprised between 0.1 and 0.6 ⁇ m.
• the average particle size of the roughening agent preferably ranges between 0.3 and 2.0 ⁇ m, most preferably around 1.0 ⁇ m.
• a preferred roughening agent is composed of polymethylmethacrylate beads.
• the layer containing the roughening agent can be the subbing layer of the support or can be an extra layer between the subbing layer and the metal layer.
• the protective element preferably comprises a cover sheet and an adhesive layer.
• the support of the heat mode element can in principle be an opaque paper base preference is given to a transparent organic resin support.
• Useful transparent organic resin supports include e.g. cellulose nitrate film, cellulose acetate film, polyvinylacetal film, polystyrene film, polyethylene terephthalate film, polycarbonate film, polyvinylchloride film or poly-Alpha-olefin films such as polyethylene or polypropylene film.
• the thickness of such organic resin film is preferably comprised between 0.07 and 0.35 mm.
• the support is a polyethylene terephthalate layer provided with a subbing layer.
• the layer containing the roughening agent can be the subbing layer itself applied to the support or can be an extra layer between the subbing layer and the metal layer.
• Tis layer (b) can contain no binder at all but preferably it contains a binder.
• Tis layer (b) can be coated in principle from an organic solvent or from an aqueous medium depending on the chemical nature of the binder.
• Organic solvent-soluble binders include e.g. polymers derived from ⁇ , ⁇ -ethylenically unsaturated compounds such as e.g.
• organic solvents can be used for dissolving and coating these polymers.
• water-soluble binders coatable from an aqueous medium can be used, e.g. gelatin, polyvinyl alcohol, polyvinyl pyrrolidone, carboxymethyl cellulose, methyl cellulose, ethyl cellulose, gum arabic, casein, different kinds of water-soluble latices, etc.
• the roughening agent is incorporated in the subbing layer applied to the polyester support, in other words this subbing layer constitutes layer (b).
• This subbing layer can be applied before or after stretching of the polyester film support.
• the polyester film support is preferably biaxially stretched at an elevated temperature of e.g. 70-120°C, reducing its thickness by about 1/2 to 1/9 or more and increasing its area 2 to 9 times. The stretching may be accomplished in two stages, transversal and longitudinal in either order or simultaneously.
• the subbing layer is preferably applied by aqueous coating between the longitudinal and transversal stretch, in a thickness of 0.1 to 5 ⁇ m.
• the subbing layer preferably contains, as described in European Patent Application EP 0 464 906, a homopolymer or copolymer of a monomer comprising covalently bound chlorine.
• a homopolymer or copolymer of a monomer comprising covalently bound chlorine examples are e.g.
• polyvinyl chloride polyvinylidene chloride, a copolymer of vinylidene chloride, an acrylic ester and itaconic acid, a copolymer of vinyl chloride and vinylidene chloride, a copolymer of vinyl chloride and vinyl acetate, a copolymer of butylacrylate vinyl acetate and vinyl chloride or vinylidene chloride, a copolymer of vinyl chloride, vinylidene chloride and itaconic acid, a copolymer of vinyl chloride, vinyl acetate and vinyl alcohol etc.
• Polymers that are water dispersable are preferred since they allow aqueous coating of the subbing layer which is ecologically advantageous.
• Said homopolymer or copolymer may be prepared by various polymerization methods of the constituting monomers.
• the polymerization may be conducted in aqueous dispersion containing a catalyst and activator, e.g., sodium persulphate and meta sodium bisulphite, and an emulsifying and/or dispersing agent.
• a catalyst and activator e.g., sodium persulphate and meta sodium bisulphite
• an emulsifying and/or dispersing agent e.g., sodium persulphate and meta sodium bisulphite
• the homopolymers or copolymers used with the present invention may be prepared by polymerization of the monomeric components in the bulk without added diluent, or the monomers may be reacted in appropriate organic solvent reaction media.
• Chemical nature, concentration and particle distribution of the roughening agent must be chosen in such a way that a certain degree of uneveness can be introduced in the metal recording layer. It is shown that this uneveness can reduce the occurence of interference patterns because the reflectance gets more diffuse. It will be clear that the roughening agent must be closely packed in the layer.
• the thickness of layer (b), the average particle size and the coverage of the roughening agent must be tuned to each other in such a way that a sufficient number of the roughening particles must protrude above the interface layer (b) / metal layer in order to induce local deformation spots into this metal layer.
• the average particle size is too low the roughening agent will not be able to introduce uneveness in the metal layer.
• the average particle size is too great too high a coverage will be required which would make layer (b) too thick. So it is clear that an optimal particle size should be chosen for the roughening agent and that this optimum will depend on the mechanical strenght of the metal layer and therefore on its thickness.
• the average particle size of the roughening agent preferably ranges from 0.3 to 2.0 ⁇ m, and is most preferably about 1.0 ⁇ m.
• the coverage of the roughening agent preferably ranges from 0.05 to 1.0 g/m2, and is most preferably about 0.6 g/m2.
• the degree of roughness of layer (b) is best characterized by the so-called R a value.
• This so-called average roughness value is defined as the arithmic average value of the absolute amounts of all the measured distances of the roughness profile from the middle line within the measured interval.
• Layer (b) preferably has a R a value of at least 0.2 ⁇ m.
• the roughening agent can be chosen from a wide variety of chemical classes and commercial products provided the particles chosen show an excellent mechanical and thermal stability.
• Preferred roughening agents include following :
• a thin intermediate layer can be applied between layer (b) and the metal recording layer for reasons of protection against physical damage.
• the thin intermediate layer is coated together with layer (b) by slide hopper coating. It can contain the same kinds of binder as layer (b) at a coverage of lower than 1 g/m2 in order not to loose the roughening effect.
• the metal recording layer is positioned immediately on top of layer (b) in order to get the full effect of the uneveness introduced by the roughening agent.
• Possible metals for the recording layers in this invention include Mg, Sc, Y, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Mn, Re, Fe, Co, Ni, Ru, Rh, Pd, Ir, Pt, Cu, Ag, Au, Zn, Cd, Al, Ga, In, Si, Ge, Sn, As, Sb, Bi, Se, Te. These metals can be used alone or as a mixture or alloy of at least two metals therof. Due to their low melting point Mg, Zn, In, Sn, Bi and Te are preferred. The most preferred metal for the practice of this invention is Bi.
• the metal recording layer may be applied on top of the layer containing the roughening agent by vapor deposition, sputtering, ion plating, chemical vapor deposition, electrolytic plating, or electroless plating.
• the recording layer is preferably provided by vapor deposition in vacuo. A method and an apparatus for such a deposition are disclosed in EP 0 384 041.
• the thickness of this Bi layer is preferably comprised between 0.1 and 0.6 ⁇ m. When this thickness is too low the recorded images do not have sufficient density. When on the other hand the thickness is too high the sensitivity tends to decrease and the minimal density, i.e. the density after laser recording on the exposed areas tends to be higher.
• this protective element comprises a transparent organic resin, acting as cover sheet, and an adhesive layer.
• a method for applying such a protective element by lamination in the same vacuum environment as wherein the deposition of the metal layer took place is disclosed in EP 0 384 041, cited above.
• the cover sheet can be chosen from the group of polymeric resins usable for the support of the heat mode element.
• the cover sheet is also polyethylene terephthalate but preferably substantially thinner than the polyethylene terephthalate of the support.
• a layer of a pressure-sensitive adhesive resin can be used for the adherence of the hard protective outermost resin layer to the heat mode recording layer.
• a layer of a pressure-sensitive adhesive resin can be used for the adherence of the hard protective outermost resin layer to the heat mode recording layer.
• a layer of a pressure-sensitive adhesive resin is 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(C1-C16)alkyl acrylate, a mixture of poly(C1-C16)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. plasticizer or other tackifying resin.
• a tackifying substance e.g. plasticizer 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 protective element is laminated or adhered to the heat-mode recording layer by means of a heat-sensitive also called heat-activatable adhesive layer or thermoadhesive layer, examples of which are described also in US-P 4,033,770.
• a heat-sensitive also called heat-activatable adhesive layer or thermoadhesive layer
• the laminating material consisting of adhesive layer and abrasion resistant protective layer and/or the recording web material to be protected by lamination are heated in their contacting area to a temperature beyond the softening point of the adhesive. Heat may be supplied by electrical energy to at least one of the rollers between which the laminate is formed or it may be supplied by means of infra-red radiation.
• the laminating may proceed likewise by heat generated by high-frequency micro-waves as described e.g. in published EP-A 0 278 818 directed to a method for applying a plastic covering layer to documents.
• the adhesive layer may be heat-curable or ultra-violet radiation curable.
• heat-curable organic resins and curing agents therefore reference is made e.g. to the above mentioned “Handbook of Adhesive Raw Materials", and for UV curable resin layers reference is made e.g. to "UV Curing: Science and Technology” - Technology Marketing Corporation. 642 Westover Road - Stanford - Connecticut - USA - 06902 (1979).
• UV curable resin layers reference is made e.g. to "UV Curing: Science and Technology” - Technology Marketing Corporation. 642 Westover Road - Stanford - Connecticut - USA - 06902 (1979).
• heat mode recording with a meltable metal layer preference is given to an easily deformable adhesive layer so that it does not form a hindrance for the formation of small metal globules in the areas of the recording layer struck by high intensity radiation energy laser energy.
• the easy deformability of the adhesive interlayer is in favour of recording sensitivity.
• dimensional stability is of utmost importance.
• Fields of application where the requirements for dimensional stability are very stringent are e.g. those where the heat moded image serves as an intermediate for the exposure of a lithographic printing plate, or as a master mask for the production of microelectronic integrated circuits or printed circuit boards (PCB) .
• PCB printed circuit boards
• one or more barrier layers can be applied onto the heat mode recording element retarding the uptake of water vapour as disclosed in European Patent Application Appl. No. 93201366, filed 12 May, 1993.
• this barrier layer is a vapour-deposited glass layer substantially composed of SiO x , x ranging from 1.2.to 1.8.
• a barrier layer can be applied to one of or to both outermost sides of the complete finished heat mode element of the present invention, or to one of or to both sides of the support of the recording element before the element is further produced.
• any laser can be used which provides enough energy needed for the production of sufficient heat for this particular process of image formation.
• a powerful infra-red laser is used.
• a Nd-YLF laser is used emitting at 1053 nm.
• a bismuth layer of 0.3 ⁇ m thickness was applied by vacuum-deposition (vacuum of 10 ⁇ 2 Pa) in a Leybold apparatus, after a weak corona discharge of 0.05 Ampère.
• a protective element consisting of a 8 ⁇ m thick adhesive layer containing copoly(butylacrylate-vinylacetate), and of a cover sheet being a 12 ⁇ m thick polyethylene terephthalate foil.
• the macroscopic homogeneity was defined as the minimal laser power at which the full areas and lines showed no interference patterns or interference fringes any more. These values are summarized in table 2 : TABLE 2 element homogeneity full areas lines R-1 > 1330 > 1330 R-2 > 1330 > 1330 I-1 1200-1260 > 1330 I-2 1110-1200 1110-1200

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• Thermal Transfer Or Thermal Recording In General (AREA)

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Cited By (6)

Citations (5)

• 1995
  • 1995-05-08 EP EP19950201166 patent/EP0684145B1/de not_active Expired - Lifetime

Patent Citations (5)

Non-Patent Citations (3)

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