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
  • B41M5/382—Contact thermal transfer or sublimation processes
  • B41M5/385—Contact thermal transfer or sublimation processes characterised by the transferable dyes or pigments
  • B41M5/388—Azo dyes
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10S428/00—Stock material or miscellaneous articles
  • Y10S428/913—Material designed to be responsive to temperature, light, moisture
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10S428/00—Stock material or miscellaneous articles
  • Y10S428/914—Transfer or decalcomania

Definitions

• the main heat source used is a thermal head with which short heating impulses lasting a fraction of a second can be emitted.
• a transfer sheet which contains the dye to be transferred together with one or more binders, a carrier material and possibly other auxiliaries such as release agents or crystallization-inhibiting substances is heated from the rear by the thermal head.
• the dye diffuses from the transfer sheet into the surface coating of the substrate, e.g. into the plastic layer of a coated paper.
• the main advantage of this method is that the amount of color transferred and thus the color gradation can be specifically controlled via the energy to be delivered to the thermal head.
• Thermal transfer printing generally uses the three subtractive primary colors yellow, magenta and cyan, possibly also black, whereby the dyes used for optimum color recording must have the following properties: easy thermal transferability, low tendency to migrate within or from the surface coating of the recording medium at room temperature , high thermal and photochemical stability as well as resistance to moisture and chemicals, no tendency to crystallize when storing the transfer sheet, a suitable color for the subtractive color mixture, a high molar absorption coefficient and easy technical accessibility.
• the azo dyes I themselves are known from the earlier German patent applications P 38 10 643.4 and P 38 16 698.4 or can be obtained by the methods mentioned there.
• the invention was therefore based on the object, suitable for thermal transfer printing red and To find yellow dyes that come closer to the required property profile than the previously known dyes.
• a method for transferring azo dyes by diffusion from a support onto a plastic-coated substrate using a thermal head was found, which is characterized in that a support is used for this purpose, on which one or more of the azo dyes I defined at the outset are located.
• Suitable alkyl radicals R 1 or R 2 are especially methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl and tert-butyl.
• Alkyl radicals R 1 can also be pentyl, isopentyl, neopentyl, tert-pentyl, hexyl and 2-methylpentyl.
• alkoxy radicals R 2 are methoxy, ethoxy, propoxy, isopropoxy, butoxy and isobutoxy.
• radical R 1 is a phenyl group bearing substituents, the following may be mentioned, for example: methyl, ethyl, methoxy, ethoxy, chlorine, bromine and cyanophenyl, the substituents of which are each in the 2, 3 or 4 position to sit.
• Suitable alkyl radicals R 3, R 3 ' , R 4, R 4 ', R S , R 6 , R 7 or R 8 are especially methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl and tert.- Butyl.
• Alkyl radicals R 3 , R 3 ', R 4 , R 4 ', R 7 or R 8 are also, for example, pentyl, isopentyl, neopentyl, tert-pentyl, hexyl, 2-methylpentyl, heptyl, octyl and 2-ethylhexyl, R 3 , R 3 ', R 4 or R 4 ' additionally, for example, nonyl and decyl.
• the C chain of the alkyl radicals R 3 , R 3 ', R 4 ' or R 4 ' is interrupted by one to three oxygen atoms
• the following groups may be mentioned, for example: 2-methoxy, 2-ethoxy, 2-propoxy , 2-butoxyethyl, 2- and 3-methoxypropyl, 1-methoxyprop-2-yl, 2-ethoxypropyl, 2-propoxypropyl, 4,7-dioxaoctyl, 4,7-dioxanonyl, 4,8-dioxadecyl, 4,7, 10-trioxaundecyl and 4,7,10-trioxadodecyl.
• Suitable alkoxy radicals R 5 or R 6 are, for example, methoxy, ethoxy, propoxy, isopropoxy, butoxy and isobutoxy.
• Preferred azo dyes I can be found in the examples.
• the dyes I to be used according to the invention are distinguished from the red and yellow dyes previously used for thermal transfer printing by the following properties: easier thermal transferability despite the relatively high molecular weight, improved migration properties in the recording medium at room temperature, significantly higher lightfastness, better resistance to moisture and chemicals , better solubility in the production of the printing ink, higher color strength and easier technical accessibility.
• the azo dyes show a significantly better color purity, especially in dye mixtures, and result in improved black prints.
• the transfer sheets required as dye donors for the thermal transfer printing process according to the invention are prepared as follows:
• the azo dyes I are dissolved in an organic solvent, e.g. Isobutanol, methyl ethyl ketone, methylene chloride, chlorobenzene, toluene, tetrahydrofuran or mixtures thereof, processed with one or more binders and possibly other auxiliaries such as release agents or crystallization inhibitors to give a printing ink which preferably contains the dyes in molecularly dispersed solution.
• the printing ink is then applied to an inert support and dried.
• Suitable binders for the use according to the invention of the azo dyes I are all materials which are soluble in organic solvents and are known to serve for thermal transfer printing, for example cellulose derivatives such as methyl cellulose, hydroxypropyl cellulose, cellulose acetate or cellulose acetobutyrate, especially ethyl cellulose and ethyl hydroxyethyl cellulose, starch, alginates, alkynyl alcohol and alkyd alcohol or polyvinylpyrrolidone and especially polyvinyl acetate and polyvinyl butyrate.
• cellulose derivatives such as methyl cellulose, hydroxypropyl cellulose, cellulose acetate or cellulose acetobutyrate, especially ethyl cellulose and ethyl hydroxyethyl cellulose, starch, alginates, alkynyl alcohol and alkyd alcohol or polyvinylpyrrolidone and especially polyvinyl acetate and polyvinyl butyrate.
• polymers and copolymers of acrylates or their derivatives such as polyacrylic acid, polymethyl methacrylate or styrene acrylate copolymers, polyester resins, polyamide resins, polyurethane resins or natural resins such as gum arabic.
• binders are often recommended, e.g. those made of ethyl cellulose and polyvinyl butyrate in a weight ratio of 2: 1.
• the weight ratio of binder to dye is usually 8: 1 to 1: 1, preferably 5: 1 to 2: 1.
• Inert carrier materials are, for example, tissue paper, blotting paper or glassine paper and films made of heat-resistant plastics such as polyesters, polyamides or polyimides, these films also being able to be metal-coated.
• the inert carrier can also be coated with a lubricant on the side facing the thermal head in order to prevent the thermal head from sticking to the carrier material.
• Suitable lubricants are, for example, silicones or polyurethanes, as are described in EP-A-216 483.
• the thickness of the dye carrier is generally 3 to 30 microns, preferably 5 to 10 microns.
• the substrate to be printed e.g. Paper
• a binder that absorbs the dye during the printing process.
• Polymeric materials whose glass transition temperature Tg is between 50 and 100 ° C., i.e. e.g. Polycarbonates and polyester. Further details can be found in EP-A-227 094, EP-A-133 012, EP-A-133 011, JP-A-199 997/1986 or JP-A 283 595/1986.
• a thermal head which can be heated to temperatures above 300 ° C., so that the dye transfer takes place in a maximum of 15 msec.
• transfer sheets were produced in a conventional manner from 8 ⁇ m thick polyester film, which was provided with an approx. 5 ⁇ m thick transfer layer made from a binder B, each of which contained 0.25 g of azo dye I.
• the weight ratio of binder to dye was 4: 1 in each case.
• the substrate to be printed consisted of paper approximately 120 ⁇ m thick, which was coated with an 8 ⁇ m thick plastic layer (Hitachi Color Video Print Paper).
• the coated side of the encoder and slave was placed on top of one another, wrapped with aluminum foil and heated to a temperature between 70 and 80 C for two minutes between two heating plates. With similar samples, this process was repeated three times at a higher temperature between 80 and 120 ° C.
• the amount of dye diffused into the plastic layer of the receiver is proportional to the optical density, which was determined as absorbance A photometrically after the respective heating to the temperatures given above.
• the temperature T * at which the absorbance reaches the value 2 can also be taken from the application, ie the transmitted light intensity is one hundredth of the incident light intensity.
• the smaller the temperature T * the better the thermal transferability of the investigated dye.
• Tables 1a to 9a list the azo dyes I tested for their thermal transfer behavior and their color.

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• Physics & Mathematics (AREA)
• Optics & Photonics (AREA)
• Thermal Transfer Or Thermal Recording In General (AREA)
• Plural Heterocyclic Compounds (AREA)

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Publications (2)

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Citations (6)

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• 1990
  • 1990-06-06 DE DE4018067A patent/DE4018067A1/de not_active Withdrawn
• 1991
  • 1991-05-24 EP EP91108420A patent/EP0460463B1/fr not_active Expired - Lifetime
  • 1991-05-24 DE DE59103852T patent/DE59103852D1/de not_active Expired - Lifetime
  • 1991-05-31 US US07/708,371 patent/US5200386A/en not_active Expired - Fee Related
  • 1991-05-31 JP JP3128943A patent/JPH04232093A/ja not_active Withdrawn

Patent Citations (6)

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