EP0358968A2 - Matériau d'enregistrement thermosensible - Google Patents

Matériau d'enregistrement thermosensible Download PDF

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Publication number
EP0358968A2
EP0358968A2 EP89115142A EP89115142A EP0358968A2 EP 0358968 A2 EP0358968 A2 EP 0358968A2 EP 89115142 A EP89115142 A EP 89115142A EP 89115142 A EP89115142 A EP 89115142A EP 0358968 A2 EP0358968 A2 EP 0358968A2
Authority
EP
European Patent Office
Prior art keywords
recording material
mixture
microcapsules
heat
material according
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP89115142A
Other languages
German (de)
English (en)
Other versions
EP0358968A3 (fr
Inventor
Reinhold Uhlemayr
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Drescher Geschaftsdrucke GmbH
Original Assignee
Drescher Geschaftsdrucke GmbH
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Drescher Geschaftsdrucke GmbH filed Critical Drescher Geschaftsdrucke GmbH
Publication of EP0358968A2 publication Critical patent/EP0358968A2/fr
Publication of EP0358968A3 publication Critical patent/EP0358968A3/fr
Withdrawn legal-status Critical Current

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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
    • B41M5/30—Thermography ; Marking by high energetic means, e.g. laser otherwise than by burning, and characterised by the material used using chemical colour formers

Definitions

  • the invention relates to a heat-sensitive recording material, in particular a paper which can be locally discolored by the action of heat, as is used as printing paper in so-called thermal printers, and a method for producing such a recording material.
  • the state of the art is that a dye precursor is finely ground in ball or pearl mills and mixed together with pigments, a binder and a color developer.
  • the chemical reaction of the color developer substance with the dye precursor then forms the actual dye to an appreciable extent only when the temperature rises, which then becomes visible in the printing process as a contrasting trace on the recording material.
  • the coating machine for the production of the recording material must have a high technical outlay in terms of performance and temperature control.
  • the drying process of the heat-sensitive recording material is very difficult since the drying must be carried out at relatively low temperatures with a high air conversion.
  • the object of the invention is to apply the components undergoing a color reaction to the carrier material in such a way that conventional coating machines are used and special temperature control during the drying process can be omitted.
  • This object is achieved in that of several, together a change in color when exposed to heat showing mixture resulting components at least one in broken microcapsules together with the other mixture components on a carrier of the recording material.
  • the basic idea of the invention is to put one of the components causing the color reaction in a microcapsule in the mixture, the capsule wall separating the dye precursor and the dye developer substance and thus reliably preventing a reaction even at higher temperatures. Coating and drying can thus take place in wide temperature ranges, so that conventional coating machines, as are known, for example, from the coating of carbonless papers, can also be used in the same way for the production of thermal papers.
  • the recording materials thus produced only have to be subjected to a subsequent step in which, after the recording material has cooled, the capsules are broken in a targeted manner so that the dye precursor and the developer substance come into contact with one another and the color reaction can take place when the temperature rises.
  • the dye precursor is present in the end product in finely divided form, optionally with an appropriate solvent, in fully active form. In this way, an optimal color yield of the usually very expensive dye precursors can be achieved.
  • the component contained in the microcapsules will be contained in a liquid, at least when exposed to heat.
  • a solvent is then available for the actual color reaction, so that the color reaction is no longer a solid-state reaction, but rather a reaction in solution which can proceed much faster and therefore with a higher yield and / or requires less activation energy.
  • the dye precursor is preferably introduced into the microcapsules because this enables the proportion of the dye precursor to be reduced without the color development being less under otherwise unchanged conditions.
  • the heat sensitivity of the paper that is to say the reaction temperature required when printing on the paper, can be influenced by the choice of the medium in which the dye precursor is placed in the capsules.
  • Preferred media contain petroleum jelly as a relatively viscous solvent or carrier.
  • waxes obtained on the basis of raw montan wax are ester and / or acid waxes.
  • their solvency for the dye precursor can be influenced via the acid and the saponification number, so that, for example, a solid solution of the dye precursor can be kept in the capsules.
  • the developer substance which is usually placed in the mixture outside the microcapsules, depends on the type of dye precursor.
  • Frequently occurring developer / dye precursor combinations contain phenol groups on the part of the developer substance.
  • One of the developer substances containing the preferred phenol groups is bisphenol A.
  • a very low recording temperature that is to say a very low reaction temperature
  • problems arise from this for example the formation of gray veils on the paper, which can be attributed to a creeping color development reaction even at room temperature, that is to say the usual storage temperature for the recording materials.
  • so-called acid catalysts can be used for the same dye precursors instead of the phenolic developer substances, in which the acid function is blocked at the storage temperature of the paper, that is to say at room temperature, and which forms an active acid function only when exposed to heat.
  • the problem with these developer substances is the relatively high temperature which is required to release the acid functions.
  • the high activation temperatures can be remedied by the addition of sulfonamides in the coating mixture, which allow a significant reduction in the reaction temperature, in particular in the case of developer substances with blocked acid function.
  • a completely different color former system are colored metal chelate complexes, a metal salt being the dye precursor and the chelating agent being the developer substance. Since these systems dispense with economic considerations such as those made with the dye precursors - none of the components are particularly expensive - either the metal salt or the chelating agent can be encapsulated and applied to the paper.
  • One of the preferred metal salts is zinc hydroxy acid, which undergoes color reactions in very good yield with the appropriate chelating agents.
  • the recording materials are thus obtained by encapsulating at least one of several components which together result in a mixture which changes color when exposed to heat, in microcapsules, in that a carrier of the recording material is coated with the mixture, and in that the microcapsules are then broken up .
  • a calender or a Velcro mechanism is particularly suitable for breaking up the microcapsules.
  • the dye precursor is preferably encapsulated in microcapsules, the capsules are mixed together with pigments and binders, and the mixture thus obtained is removed added developer substances that have the ability to convert the dye precursor to its color form when the temperature rises.
  • the microcapsules are broken in a targeted manner. Since a fully usable recording material is only obtained by breaking the capsules and the color reaction cannot take place if the microcapsule walls are intact, the recording material can be coated like any other paper before the last process step, in particular like carbonless papers, without fear of a premature dye reaction . This saves special precautionary measures during temperature control during the coating and drying of the carrier materials.
  • FIG. 1 schematically shows a section through a recording material according to the invention, although the binders present between the individual mixture components are not shown.
  • the carrier 10 identified overall by the reference number 10, will often be a paper layer.
  • the capsules consist of a capsule wall 18 which is formed, for example, from melamine resins and which surrounds the so-called core medium or core solvent 20, in which the dye precursor is preferably present in solution.
  • the individual components of the mixture namely the microcapsules 12, the developer particles 14 and the pigment particles 16 are held on the carrier 10 by a binder (not shown).
  • the paper layer is dried in the customary form, drying temperatures being permitted here which are above the temperature value which triggers the writing effect or the color development when the recording material is used.
  • the microcapsules are deliberately destroyed and broken open, for example by calendering, and the paper material then obtained is shown schematically in FIG. 2 in the sectional view.
  • the core solvent which is generally viscous to solid, still contains the dye precursor in dissolved form, while the developer particles 14 can be in direct contact with the core solvent regions.
  • a reaction does not initially take place at room temperature because, on the one hand, a relatively highly viscous to solid medium can be selected as the core solvent and because the color reaction itself requires a certain activation temperature.
  • the developer substances are generally relatively inexpensive, they are dispersed in large numbers in the mixture submitted and the process limiting the color development is then only the diffusion of the dye in the core solvent to the developer substances.
  • the dye according to the invention is finely distributed or dissolved in the core solvent, it is possible to work with significantly lower amounts of dye precursors than according to the prior art, in which only a solid-solid reaction can be used for the color development.
  • thermal paper according to the invention shows the production of thermal paper according to the invention on the basis of typical dye precursor / developer substances.
  • Solutions A and B are mixed together with stirring.
  • a permanent coating solution is obtained.
  • a paper with a basis weight of 50 g / m2 is coated with a doctor blade.
  • the coating weight is 8 g / m2 dry. After drying at 90 o C in a forced air oven, this paper is treated by calendering. During this process it must be ensured that the capsules are destroyed.

Landscapes

  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • General Chemical & Material Sciences (AREA)
  • Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Heat Sensitive Colour Forming Recording (AREA)
  • Color Printing (AREA)
EP19890115142 1988-09-16 1989-08-17 Matériau d'enregistrement thermosensible Withdrawn EP0358968A3 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE3831591 1988-09-16
DE3831591 1988-09-16

Publications (2)

Publication Number Publication Date
EP0358968A2 true EP0358968A2 (fr) 1990-03-21
EP0358968A3 EP0358968A3 (fr) 1991-05-08

Family

ID=6363117

Family Applications (1)

Application Number Title Priority Date Filing Date
EP19890115142 Withdrawn EP0358968A3 (fr) 1988-09-16 1989-08-17 Matériau d'enregistrement thermosensible

Country Status (2)

Country Link
EP (1) EP0358968A3 (fr)
PT (1) PT91730A (fr)

Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE1421418A1 (de) * 1961-04-29 1968-10-10 Lumoprint Zindler Kg Verfahren zur Herstellung von Kopien und Material zur Durchfuehrung dieses Verfahrens
CA942953A (en) * 1970-02-28 1974-03-05 Fuji Photo Film Co. Recording material
JPS60214990A (ja) * 1984-03-26 1985-10-28 Fuji Photo Film Co Ltd 感光感熱記録材料
US4630079A (en) * 1984-04-21 1986-12-16 Mitsubishi Paper Mills, Ltd. Pressure sensitive copying paper
JPH0686152B2 (ja) * 1985-01-23 1994-11-02 富士写真フイルム株式会社 感熱記録材料

Also Published As

Publication number Publication date
PT91730A (pt) 1990-05-31
EP0358968A3 (fr) 1991-05-08

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