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
  • B41M5/42—Intermediate, backcoat, or covering layers
  • B41M5/44—Intermediate, backcoat, or covering layers characterised by the macromolecular compounds
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41M—PRINTING, DUPLICATING, MARKING, OR COPYING PROCESSES; COLOUR PRINTING
  • B41M2205/00—Printing methods or features related to printing methods; Location or type of the layers
  • B41M2205/30—Thermal donors, e.g. thermal ribbons

Definitions

• the invention relates to a method for producing a thermal ink ribbon, in particular thermocarbon ribbon, for thermal transfer printing with a wax and / or plastic-bound melting ink, which has a polymer layer on one side, and the product obtained thereafter.
• Thermal ribbons have been known for a long time. They point to a film-like carrier which, for. B. can consist of paper or plastic, a layer of a melting ink, so in the form of a meltable wax or plastic-bound colorant or carbon black layer.
• the melting ink is melted by means of a thermal print head and transferred to a recording paper or film. This is generally referred to as a thermal transfer ribbon or TCR ribbon ("Thermal Carbon Ribbon").
• Thermal printers that emboss a heat symbol during the printing process are e.g. B. from DE-ASen 2 062 494 and 2 406 613 and DE-OS 3 224 445 known.
• the procedure for printing with a thermal ribbon is generally as follows:
• the print head of a thermal printer presses the thermal ribbon onto the recording substrate. It develops temperatures that can be around 400 o C maximum.
• the uncoated back of the thermal ribbon or the film-like carrier are in direct contact with the print head or the thermal symbol formed thereon during the printing process.
• the relative speed between the thermal ink ribbon and the printing paper or film is zero.
• the melting color in the form of the symbol to be printed is melted by the Transfer thermal ribbon to the recording substrate.
• the thermal ink ribbon is detached from the recording substrate, the molten symbol adheres to it and solidifies.
• thermal ribbons with simple film-like carriers there are also those thermal ribbons in which the thermal symbol is not produced by a thermal print head, but by resistance heating of a specially designed film-like carrier or by a special design of the melting ink.
• the melting color which represents the actual "functional layer" during the printing process, also contains the materials already described above.
• electro-thermal transfer process (“Electro Thermal Ribbon”).
• Such a thermal transfer printing system is described, for example, in US Pat. No. 4,309,117.
• thermocarbon tapes regularly have, as can be seen from the above, a film-like carrier, which usually consists of a polyester or polycarbonate.
• a film-like carrier which usually consists of a polyester or polycarbonate.
• the use of these carriers is associated with high material costs. Recycle is regularly excluded after use.
• EP-A-0 120 230 proposes a thermal ribbon of a special structure which has no carrier film and is therefore inexpensive.
• the melting ink of the known thermal ink ribbon essentially consists of at least a first hard polymer, a film-forming material, a second polymer, which is primarily an adhesive or a medium with a low melting point, and a coloring material.
• This thermocarbon tape should have sufficient adhesive properties to allow its longitudinal pull as a continuous, self-supporting material. In the practical use of such a thermal ribbon, it is necessary to guide it over an endless ribbon for support, which means an increased mechanical and thus increased cost. A special printer must also be used for this.
• the invention was therefore based on the object of proposing a thermal ink ribbon or a method for its production which does not have the disadvantages mentioned above, ie no expensive carrier film required and when using it, an additional supportive endless belt, as described above, can be dispensed with.
• the invention accordingly starts from a layer of a wax and / or plastic-bound melting ink, which is not applied by a carrier film, but rather on the one side or one side, which faces the thermal printhead during the printing process, in the manner described a polymer layer becomes.
• the cheapest materials can be used here.
• the layer thickness of the polymer layer can preferably be set in ranges up to about 0.5 to 6 micrometers. It is decisive when setting the layer thickness alone that it is sufficient to prevent the thermal print head from being contaminated by contact with the melting ink during the thermal printing process. Furthermore, this minimal layer is necessary to enable the printing of closed letters, such as the letter "O". If the protective layer were omitted entirely, a full "o" would be imaged on the substrate to be printed.
• thermocarbon tapes available in the prior art regularly have carrier foils with a thickness of the order of about 3 to 20 micrometers.
• the plastic-bound melting ink can also easily have a certain proportion of waxes or wax-like materials.
• An essential component of the melting ink is preferably a thermoplastic. At normal temperature, thermoplastics are hard or even brittle plastics that soften reversibly when heat is applied and become mechanically easily deformable in order to finally change to a viscous liquid state at high temperatures. They go through a softening or melting range.
• thermoplastics are preferably used in the context of the invention: polystyrene, polyvinyl acetate, polyvinyl acetal, polyvinyl chloride, polyamide, polyethylene, polymers of vinyl acetate and vinyl chloride, polyvinyl ethers, polyvinyl propionates, polyacrylates, ethylene / vinyl acetate copolymers.
• thermoplastic binder or the melting ink e.g. B. phthalic acid esters such as di-2-ethylhexyl phthalate, diisononyl phthalate and di-isodecyl phthalate, aliphatic dicarboxylic acid esters such as that of adipic acid, in particular di-2-ethylhexyl adipate and diisodecyl adipate, phosphates such as tricresyl phosphate and triphenyl phosphate 2-triethylene glycol such as fatty acid esters such as fatty acid glycol -ethylbutyrate) and the like. In individual cases it may also be advantageous to incorporate stabilizers into the thermoplastic binder or the melting ink.
• stabilizers into the thermoplastic binder or the melting ink.
• the wax-based and / or plastic-bound melting ink contains customary colorants, i.e. Pigments and / or dyes.
• customary colorants i.e. Pigments and / or dyes.
• the wax and / or plastic-bound melting color layer which is provided with a polymer layer by the process according to the invention, can be produced using a variety of technologies. This can be done, for example, by a casting process, extrusion, blowing, coating on auxiliary supports and subsequent removal therefrom, by the screen printing process or from a melt or solution with subsequent evaporation of the solvent or dispersion medium.
• the term "dispersion” is not intended to include the term "solution”, although a dispersion may also contain dissolved particles in addition to emulsified suspended particles.
• the formation of the polymer layer by the method according to the invention can be carried out in a variety of ways.
• a dispersion or solution of a film-forming polymer that is not meltable during the thermal printing process can be applied in a thin layer and then the dispersing agent can be applied, for example, by passing warm air, e.g. B. at 80 o C, evaporated.
• warm air e.g. B. at 80 o C
• ethanol and / or water can be considered as solvents.
• Water as a dispersant has the advantage of being environmentally friendly.
• polyvinylpryrrolidone and / or polyvinyl alcohol are particularly suitable as the polymer.
• the dispersions of the different polymers are preferably used in a concentration of about 10 to 40% by weight.
• the dispersion can be applied by any suitable technique, for example by spraying or printing on a dispersion, either with water or with an organic solvent, such as alcohol, or by application with a doctor blade in the form of the dispersion or solution.
• the polymer After evaporation of the dispersing agent or solvent, the polymer remains with film formation as a non-meltable protective layer of the desired thin layer of in particular about 0.5 to 15 micrometers, preferably about 0.5 to 6 micrometers.
• the protective layer can also be formed by using a suitable monomer, e.g. B. styrene, substituted acrylate or a suitable prepolymer, e.g.
• the advantages associated with the invention can be seen in particular in the fact that an expensive carrier film is no longer necessary.
• the thickness of the polymer layer may be less than 1 micron in individual cases. It only has to be so strong that it excludes the contact between the melting ink layer and the thermal print head during the thermal printing process. This enables it to write out closed letters.
• a thinner polymer layer compared to a thicker carrier film also promotes heat transport during the thermal printing process.
• more ribbon material can be accommodated in a thermal ribbon cassette. If a water-soluble polymer is used to form the protective layer, there is the possibility of reprocessing, in that the water-soluble polymer is detached from, for example, the wax material and the latter is returned to the production process for a thermocarbon tape.
• Example 2 Using the recipe described in Example 1, a color layer was formed on an auxiliary carrier film. A polymer layer was applied to this using the following recipe: 100 parts by weight of water, 12 parts by weight of 25% ammonia and 30 parts by weight of vinyl acetate-crotonic acid copolymer. The water was removed by passing warm air over it. An approximately 4-5 micrometer thick polymer layer was formed.
• Examples 1 and 2 were repeated with the modification that the following formulation was used instead of the formulation given in Example 1 for the colored layer: 40 parts by weight of ester wax, 33 parts by weight of paraffin wax, 2 parts by weight of polyvinyl isobutyl ether, 5 parts by weight of mineral oil and 20 parts by weight of carbon black. This applied mass was treated as in the previous examples by passing warm air over it.

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• Physics & Mathematics (AREA)
• Optics & Photonics (AREA)
• Thermal Transfer Or Thermal Recording In General (AREA)
• Impression-Transfer Materials And Handling Thereof (AREA)

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Citations (4)

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• 1988
  • 1988-05-16 DE DE3816636A patent/DE3816636A1/de active Granted
• 1989
  • 1989-04-19 EP EP19890107007 patent/EP0342371A3/fr not_active Withdrawn
  • 1989-05-12 US US07/351,624 patent/US5019421A/en not_active Expired - Lifetime
  • 1989-05-16 JP JP1120577A patent/JPH0218078A/ja active Pending

Patent Citations (4)

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