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
  • B41M5/333—Colour developing components therefor, e.g. acidic compounds
  • B41M5/3333—Non-macromolecular compounds

Definitions

• the invention relates to a heat-sensitive recording material having a heat-sensitive layer applied to a support, which contains a color-forming substance, which is normally colorless or only slightly colored, and an organic compound which, when heated, causes the color-forming substance to form a color.
• the known heat-sensitive recording materials generally consist of a support, e.g. B. made of paper or a plastic film or sheet on which the heat-sensitive layer is applied.
• the colorless or only slightly colored heat-sensitive layer usually contains a color-forming substance and a substance (activator) which is capable of causing the color-forming substance to form when the heat-sensitive layer is heated.
• Suitable color-forming substances are, in particular, leuco bases of di- or triphenylmethane, fluorane, phenothiazine, xanthene, thioxanthene, acridine dyes or other dye derivatives which release the actual dye when the acid concentration is increased, while activators for the Color formation especially acidic organic substances, such as. B. phenols can be used.
• the known heat-sensitive recording materials are not entirely satisfactory. For example, their response to heat is often inadequate for fast recording and high recording density.
• the heat-sensitive recording materials are composed inhomogeneously, i. that is, the color former and activator are present as discrete particles or crystals next to one another, and only when heat-induced melting does mixing occur with the formation of color. This is associated with a low resolution of the recording materials. There is therefore a need for further, new, heat-sensitive recording materials with improved properties.
• the object of the present invention was to provide new heat-sensitive recording materials with a wide range of uses.
• the new recording materials are said to largely overcome the disadvantages of the previously known products of this type, in particular to have a high sensitivity to heat and high recording density and a high resolution, so that they can also be used as transparent thermographic films.
• the invention accordingly relates to a heat-sensitive recording material having a heat-sensitive layer which is applied to a support and which contains a color-forming, normally colorless or only slightly colored substance and an activator which, under the action of heat, brings about the color formation of the color-forming substance, which is characterized in that that a sulfonic acid ester, in particular of a secondary alcohol, is contained as an activator in the heat-sensitive layer.
• the heat-sensitive layer of the recording materials according to the invention contains, as a color-forming component, the substances customary for recording materials of this type, as described in the relevant literature.
• the substances customary for recording materials of this type include the leuco bases or leuco-lactone forms of di- or triarylmethane, fluorane, phenothiazine, xanthene, thioxanthene, spiropyran or acridine dyes.
• all colorless or only weakly colored dye derivatives are suitable which release the actual dye when the acid concentration is increased.
• color formers examples include leuco crystal violet, leukomalachite green, benzoyl leukomethylene blue, Michler's hydrol [4,4'-bis (dimethytamino) benzhydro], Michler's hydrolbenzyl ether, 3,3-bis (p-dimethylaminophenyl) -6- dimethylamino-phthalide, 7-diethylamino-2,2'-spirodi- (2H-1-benzopyran) and 3-diethylamino-7-o-chloroanilinofluoranes.
• the heat-sensitive recording materials contain sulfonic acid esters as the activator which causes the color to form when the recording materials are heated.
• Sulfonic acid esters of secondary alcohols are particularly suitable as activators.
• Preferred sulfonic acid esters are those derived from secondary, saturated aliphatic alcohols having 3 to 12 carbon atoms or from cycloaliphatic alcohols.
• the secondary alcohols can be both monoalcohols and diols or polyols. Examples of particularly advantageous aliphatic secondary alcohols are isopropanol, 2-butanol, 2,3-butanediol and 2,5-n-hexanediol. Cyclohexanol is an example of cycloaliphatic alcohols.
• the sulfonic acid esters according to the invention are derived in particular from aromatic sulfonic acids, preferably from benzenesulfonic acid or toluenesulfonic acid.
• aromatic sulfonic acids preferably from benzenesulfonic acid or toluenesulfonic acid.
• sulfonic acid esters which have proven to be particularly advantageous when used in the heat-sensitive recording materials are cyclohexyl tosylate, 2,3-butanediol di-tosylate, sec-butyl tosylate and 2,5-hexanediol di-tosylate.
• sulfonic acid esters of aliphatic sulfonic acids for example methylsulfonic acid
• sulfonic acid esters of aliphatic sulfonic acids for example methylsulfonic acid
• activators according to the invention albeit with somewhat less advantage of primary, saturated aliphatic alcohols, for example n-butanol, n-octanol, neopentyl glycol or glycerol, or of unsaturated or aromatic alcohols, for example allyl alcohol, benzyl alcohol or phenylpropanediol- (1).
• the ratio of color former to activator can vary within wide limits in the recording materials according to the invention.
• the activator is always present in such quantities that the desired color change and color intensity is obtained after the recording material has been heated.
• Color formers and activators are usually used in a molar ratio in the range from 1: 100 to 1: 2.
• binders consist of compounds which do not discolor themselves in the heat and cause the color formers and activators and also any other additives which may be used to adhere firmly to the surface of the carrier of the heat-sensitive recording material.
• Waxes such as vegetable, mineral and / or petroleum waxes as well as fatty acid amide waxes and, in particular, film-forming polymers can be used as such binders.
• film-forming polymers which are particularly suitable as binders are ethylene polymers, propylene polymers, styrene polymers, acrylate and methacrylate polymers, vinyl acetate polymers, vinyl alcohol polymers, vinyl chloride polymers, acrylonitrile polymers, butadiene polymers. and isoprene polymers, epoxy resins, cellulose derivatives, natural and synthetic rubbers, polyamides, polyurethanes and polycarbonates, polyvinyl chloride, polystyrene, polyvinyl alcohol and polymethyl methacrylate being particularly preferred.
• the heat-sensitive layer of the recording materials contains further additives known per se, such as, for example, plasticizers for the binder, polymer stabilizers, optical brighteners, white or colored pigments, etc.
• additives are in the heat-sensitive layer generally in amounts up to a maximum of 30 wt .-%, based on the heat-sensitive layer.
• Suitable supports for the heat-sensitive layer are the supports which are known and customary per se for heat-sensitive recording materials of the type in question. These include in particular any, optionally surface-coated, natural or synthetic papers, including photographic papers, plastic films or foils, metals or glass. Plastic films or sheets, e.g. B. made of polyester or polyamides, are particularly suitable as a carrier when a transparent image is to be generated with the heat-sensitive recording material.
• the carrier is generally dimensionally stable, it can be flexible or rigid. For better adhesion of the heat-sensitive layer, the carrier can be mechanically and / or chemically pretreated or provided with an adhesive layer.
• the heat-sensitive recording material according to the invention can be produced, for example, by dissolving the components of the heat-sensitive layer in a suitable solvent, applying the solution to the support in the desired layer thickness in accordance with known techniques, evaporating the solvent and drying the heat-sensitive layer at temperatures below the color formation temperature .
• the amount of the heat-sensitive layer applied to the support in the dry state is preferably 2 to 25 g / m 2 .
• the heat-sensitive layer can be subjected to a surface treatment after application to the support, for example to produce a particularly smooth surface.
• the heat-sensitive recording materials according to the invention are notable for their high thermal responsiveness and, associated therewith, their recording speed, their resolving power and their recording fidelity.
• the temperatures for color formation correspond to those of the known heat-sensitive recording materials.
• the heat-sensitive recording materials are therefore suitable for use in all known fields of application for these products, in particular for thermography and for the production of storage-stable, heat-sensitive, transparent films, such as heterogeneously coated thermographic papers.
• the table clearly shows that in principle all sulfonic acid esters are suitable as activators in heat-sensitive recording materials.
• the sulfonic acid esters of unsaturated, aromatic or secondary, saturated alcohols show a significantly higher sensitivity than that of primary, saturated alcohols. Because of their particular resistance to hydrolysis, the sulfonates of secondary, saturated alcohols are particularly preferred.
• the solution was spread with the aid of a doctor knife onto a 30 1 1 m thick polyester film in such an amount that a layer of 20 ⁇ m remained after drying. After a metal mask had been placed on top, an image was generated in the heat-sensitive layer using a stream of warm air.
• the heat-sensitive papers produced according to Examples 12 to 15 were written in a small thermal printer. Perfect thermal prints were obtained in all cases.

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• 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)

Applications Claiming Priority (2)

Publications (3)

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• 1982
  • 1982-11-27 DE DE19823243945 patent/DE3243945A1/de not_active Withdrawn
• 1983
  • 1983-11-17 DE DE8383111500T patent/DE3361241D1/de not_active Expired
  • 1983-11-17 EP EP83111500A patent/EP0110252B1/de not_active Expired
  • 1983-11-22 US US06/554,326 patent/US4523208A/en not_active Expired - Fee Related
  • 1983-11-28 JP JP58222277A patent/JPS59109388A/ja active Pending

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