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
  • B41M5/405—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 layers cured by radiation

Definitions

• the invention relates to a heat-sensitive recording material which is a multilayer composite material, the carrier material of which is connected to the heat-sensitive layer via an intermediate layer and a protective layer over the recording layer and a backside coating are present.
• DE-A-3319299 describes a heat-sensitive recording material which has a protective layer on the recording layer which contains a water-soluble binder and silicon dioxide with an oil absorption of 150% or more. The proportion of Si0 2 can be 10-70% by weight.
• the application of protective layers made from aqueous coating colors which contain water-soluble binders has the disadvantage that part of the dissolved binder penetrates into the recording layer and adversely affects its behavior.
• Heat-sensitive recording materials with a protective layer protecting the recording layer and hardened by means of an electron beam are known from DE-A-3312716.
• Protective layer with a basis weight of 0.1 to 20 g per m which can contain 5 to 300 parts by weight of pigment per 100 parts by weight of film-forming resin, is formed from oligomers which are liquid at room temperature and have at least one ethylenically unsaturated bond per molecule and the oligomers converted into polymers by curing with electron beams.
• the formation of the heat-sensitive layer is not critical, and both metal salts of higher fatty acids, such as iron (III) stearate and gallic acid or other polyhydric phenols, and weakly basic dye precursor compounds in combination with organic acidic substances can be used as color-forming reactants .
• the known recording material can have a backside coating on the back of the carrier material made of a polymer hardened by electron beams as a film former.
• the object of the invention is to provide a heat-sensitive recording material which is a multi-layer composite material which is particularly stable against environmental influences and which shows a high dynamic sensitivity regardless of the carrier material.
• This object is achieved by the heat-sensitive recording material with a heat-sensitive recording layer arranged on the front of a carrier material, which contains color precursor compounds and acidic organic compounds as color-developing reactants and which has a protective layer over the recording layer and a back coating on the back of the carrier material , both of which are layers of crosslinked polymers hardened by means of electron beams, characterized in that an intermediate layer of crosslinked polymers hardened by means of electron beams is also present between the carrier material and the recording layer.
• the protective layer covering the heat-sensitive recording layer, the intermediate layer and the back coating are made from one or more oligomers which are liquid at room temperature and have at least one ethylenically unsaturated bond per molecule, the oligomers being polymerized and crosslinked by means of electron beams, so that a water-insoluble and solvent-insoluble protective layer is formed.
• an intermediate layer of polymers hardened and crosslinked by means of electron beams is present between the carrier material and the heat-sensitive recording layer.
• the intermediate layer is formed with a basis weight of 1 g per m 2 to 10 g per m 2 .
• Such an intermediate layer has the advantage that the influence of the backing material on the color formation reaction and the contrast of the resulting recording with respect to the image background is suppressed.
• Any coating base papers can be used, in particular when paper is used as the carrier material. Backing papers with special top surface smoothness is not required.
• the intermediate layer prevents the coating composition for the recording layer from penetrating into the carrier material and reduces the heat flow into the carrier material during use.
• plastic films can also be used as the carrier material.
• Suitable coating base papers preferably have a surface sizing which contains polymers which, under the influence of the electron beams, are capable of graft copolymerization with the oligomers of the intermediate layer. Such graft copolymerization can also occur with plastic films as the carrier material and improve the adhesion of the intermediate layer. .
• the multilayer composite material according to the invention also has a back coating on the back, the structure of which essentially corresponds to that of the intermediate layer.
• the back coating is 1 g / m 2 to 10 g / m 2 .
• the protective layer, the back coating and the intermediate layer can also contain pigments in addition to the film-forming polymer.
• Suitable pigments are inorganic pigments such as calcium carbonate, zinc oxide, aluminum oxide, titanium dioxide, silicon dioxide, aluminum hydroxide, barium sulfate, zinc sulfate, kaolin, clay, calcined clay.
• organic pigments such as polystyrene, microspheres, nylon powder, polyethylene powder, zinc stearate, magnesium stearate, calcium stearate and barium stearate can also be used.
• Suitable pigments have a particle size of 0.3-5 ⁇ m and can be used in amounts of 0.2 to 300 parts by weight per 100 parts by weight of polymer component. Amounts of 0.02 to 4.5 parts by weight per 100 parts by weight of the polymer component of the resin layer are particularly preferred.
• the protective layer is applied in amounts of 1 g per m 2 to 10 g per m 2 (as a crosslinked polymer coating). Amounts of 2 to 5 g per m 2 , based in each case on the weight of the crosslinked protective layer, are particularly preferred.
• Electron beam accelerators suitable for hardening the protective layer or the intermediate layer and the back coating are commercially available.
• the oligomer layer is irradiated with the electron beam of suitable dosage, the dosage being adapted to the requirements of the special oligomer or the oligomer mixture in such a way that the oligomers are polymerized and crosslinked to form a water-insoluble and solvent-insoluble layer.
• the radiation dose required is 0.1 Mrad to 20 Mrad, preferably 3 to 10 Mrad. If, according to a preferred embodiment of the invention, a graft copolymerization between monomers and oligomers and the synthetic polymers in the recording layer is desired at the interfaces between the recording layer and the protective layer and / or intermediate layer, a somewhat higher one becomes Radiation dose used as for the decomposition and curing of the oligomers in order to activate the synthetic polymers in the recording layer to such an extent that the desired graft copolymerization occurs.
• the yield of free radicals and graft copolymers formed by radiation can be expressed by a so-called G value, where
• G 100 ----- of radicals and molecules formed Number of absorbed energies in eV.
• the G value is an expression of the yield of the chemical reactions caused by radiation between the oligomers among one another and the polymers in the adjacent recording layer.
• the intermediate layer and possibly the backside coating are applied to the carrier materials such as paper or plastic films and then the recording layer.
• the polymer layer crosslinked by the electron beams is then formed on the dried, heat-sensitive recording layer as a protective layer.
• the intermediate layer, the backside coating and the protective layer are produced from a coating composition which contains one or more oligomers with at least one ethylenically unsaturated bond in the molecule.
• the oligomers which are liquid at room temperature can be used as oligomers or a mixture and generally have a molecular weight of up to 50,000. It is essential that the oligomers are combined, if necessary, in such a way that the viscosity of the coating composition allows the application of a uniform liquid film.
• Unsaturated polyesters such as condensation products of maleic acid, fumaric acid and other unsaturated dibasic acids, phthalic acid and ethylene glycol or other dihydric alcohols.
• Polyester acrylates or polyester methacrylates such as condensation products of phthalic acid, maleic acid, fumaric acid or other dibasic acids, ethylene glycol, glycerol, pentaerythritol or other polyhydric alcohols with acrylic acid or methacrylic acid.
• urethane acrylates or urethane methacrylates d. H. Condensation products of ethylene glycol or other polyhydric alcohols, adipic acid and other dibasic acids, polyisocyanates, especially di-isocyanates and acrylic acid or methacrylic acid.
• epoxy acrylates or epoxymethacrylates that are reaction products of an epoxy resin with acrylic acid or methacrylic acid.
• Polybutadiene acrylates or polybutadiene methacrylates these are reaction products of a polybutadiene oligomer of a polyisocyanate and hydroxyalkyl acrylate or hydroxyalkyl methacrylate.
• Polyether acrylates or polyether methacrylates these are condensation products of acrylic acid or methacrylic acid and addition products of trimethylol, propane, pentaerythritol and other polyhydric alcohols and alkylene oxide.
• meltamine acrylates or melamine methacrylate these are condensation products of methylolmelamine and hydroxyalkyl acrylate or hydroxyalkyl methacrylate.
• the heat-sensitive recording layer contains, as film-forming binder, at least one synthetic polymer which is capable of graft copolymerization, so that under the action of the electron beams when the liquid oligomers harden, a graft copolymerization of the oligomers with the polymer or polymers Binder system of the heat-sensitive recording layer at the boundary layer between - lo ⁇
• the protective layer and / or the intermediate layer takes place. This leads to a stronger bond between the layers with each other and with the carrier material.
• EP - A - 306916 as a color-developing compound bis (3 f -allyl-4'-hydroxyphen ⁇ l) - ulfone and or dibenzyl oxalate or their derivatives are required in order to achieve advantageous results
• organic acidic developer materials are used which can form a color with the special dye precursor. These include organic acidic materials such as phenolic compounds, e.g. B.
• Organic acidic developer materials which can form a color with the special dye precursor can be used for the heat-sensitive recording layer.
• organic acidic materials such as phenol compounds, e.g. B. 4-tert-butylphenol, 4-tert-octylphenol, 4-phenylphenol, 4-acetylphenol, " ⁇ -naphthol, i-naphthol, hydroquinone, 2,2'-dihydroxydiphenyl, 2,2'-meth len -bis (4-methyl-6-tert-butylphenol), 2,2'-methylene-bis- (4-chlorophenol), 4,4 * - -dihydroxy-diphenyl-methane, 4,4'-isopropylidenediphenol, 4 , 4'-isopropylfen-bis- (2-tert-butylphenol), 4,4'-sec-butylene diphenol, 4,4'-cyclohexylidenediphenol, 4,4'-dihydroxydiphenyl s
• benzoic acid p-tert-butylbenzoic acid, trichlorobenzoic acid, 3-sec-butyl-4-hydroxybenzoic acid, 3-C ⁇ clohexyl-4-hydroxybenzoic acid, 3,5-dimethyl-4-hydroxybenzoic acid, salicylic acid, 3-isopropylsalicylic acid, 3-tert-butyl salicylic acid, 3-benzylsalicylic acid, 3-GO-methylbenzyl) salicylic acid, 3 -Chlor-5 - ( «- methylbenzyl) salicylic acid, 3,5-di-tert-butylsalicylic acid, 3-phenyl-5- (ot, e ⁇ _ * -dimethylbenzyl) - salicylic acid, 3,5-di-fei.
• -methylbencyl salicylic acid and terephthalic acid furthermore the salts of such phenolic compounds or aromatic carboxylic acids with polyvalent metals such as e.g. B. zinc, magnesium, aluminum, calcium, titanium, manganese, tin and nickel.
• polyvalent metals such as e.g. B. zinc, magnesium, aluminum, calcium, titanium, manganese, tin and nickel.
• Bisphenol-A is very particularly preferred according to the invention as an acidic color developer.
• gallic acid is a preferred reaction partner.
• Dyes based on triacrylmethane e.g. 3,3-bis (p-dimethylaminophenyl) phthalide, 3- (p-dimethylaminophenyl) -3- (1,2-dimethylindol-3-yl) phthalide, 3- (p- Dimethylaminophenyl) -3- (2-methylindol-3-yl) phthalide, 3,3-bis (1,2-dimethylindol-3-yl) -5-dimethylaminophthalide, 3,3-bis (1,2-dimethylindol-3 -yl) -6-dimethylaminophthalide, 3,3-bis (9-ethylcarbazol-3-yl) -6-dimethylaminophthalide, 3,3-bis (2-phenylindol-3-yl) -6-dimethylamino- phthalide, 3,3-bis (4-dimethylamoniophenyl) -6-dimethylaminophthalide
• Color precursors based on metal salts Fe salts, in particular metal salts of higher fatty acids.
• the recording layer is formed by applying a coating composition which, in addition to the color runner compound (s), also contains the acidic developer compound in addition to the customary auxiliaries for this layer.
• the heat-sensitive recording layer contains starch, hydroxyethyl cellulose, methyl cellulose, CMC, casein, polyvinyl alcohol, mixed polymers of styrene and maleic anhydride or mixed polymers of styrene and acrylic acid or methacrylic acid and polymer dispersions which are used as binders for paper coatings .
• the binder content is 2 to 40, preferably 5-25, percent by weight, based on the total solids of the heat-sensitive recording layer.
• the heat-sensitive recording layer particularly preferably contains at least one synthetic polymer which is capable of graft copolymerization.
• Particularly suitable synthetic polymers are polyacrylates, polymethacrylates, polyacrylamides, polymethacrylamides, polystyrene copolymers, polyacrylonitrile, polymethacrylonitrile, polymethacrylonitrile, polyvinylidene chloride, polyvinyl alcohols, polyvinyl pyrrolidone, polyvinyl acetates, cellulose derivatives.
• the chemical valence bonds in these film-forming polymers are activated by high-energy electron beams until *. they are capable of reactions, in the presence of monomers and oligomers, in particular of graft copolymerization and crosslinking.
• the binder system of the recording layer preferably contains a proportion of such polymers.
• Suitable meltable compounds such as amide waxes, fatty acid amides, carnauba wax, paraffin wax, calcium stearate, ester waxes, dimethyltherephthalate and p-benzylbiphenyl are used to adjust the heat sensitivity of the recording layer.
• the recording layer can also contain inorganic pigments such as kaolin, clay, calcium carbonate, titanium dioxide, silicon dioxide.
• the amount of inorganic pigments in the recording layer can be 10 to 60 percent by weight, based on the total weight of the coating composition.
• auxiliaries can be added to the heat-sensitive coating composition, such as dispersants, antifoams, UV absorbers, stabilizers, etc.
• the amount of meltable compounds such as waxes, amides or organic compounds with melting ranges from 60 ° to 180 ° C. is generally 10 to 1000 parts by weight per 100 parts by weight of color-forming compounds.
• the components of the coating composition are dispersed using water as the dispersing medium with the aid of suitable dispersing devices.
• the reactants can be dispersed both separately and together, with separate dispersing being preferred. So-called agitator ball mills are particularly preferred as the dispersing device.
• the composition for the heat-sensitive recording layer can be applied using customary methods of paper coating technology.
• the amount of coating is generally 2 to 12 g per m 2 , preferably 3 to 10 g per m 2 , the values relating to dry weight.
• the heat-sensitive coating composition from the example mentioned above is applied to uncoated paper with a weight of 70 g / m 2 in an amount of 5 g / m 2 and then dried.
• the dyn. Sensitivity in an energy range of 12.6 to 37.8 mJ / mm 2 determined. The results are shown in Tab. 1.

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• Physics & Mathematics (AREA)
• Optics & Photonics (AREA)
• Heat Sensitive Colour Forming Recording (AREA)

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• 1990
  • 1990-04-14 DE DE19904012185 patent/DE4012185C1/de not_active Expired - Fee Related
• 1991
  • 1991-04-20 WO PCT/EP1991/000764 patent/WO1992018338A1/de not_active Ceased

Patent Citations (4)

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