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Publication numberUS3684552 A
Publication typeGrant
Publication dateAug 15, 1972
Filing dateNov 16, 1970
Priority dateNov 16, 1970
Publication numberUS 3684552 A, US 3684552A, US-A-3684552, US3684552 A, US3684552A
InventorsJoseph A Wiese Jr, George Van Dyke Tiers
Original AssigneeMinnesota Mining & Mfg
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Heat-sensitive sheet material
US 3684552 A
Abstract  available in
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Claims  available in
Description  (OCR text may contain errors)

United States Patent 3,684,552 HEAT-SENSITIV E SHEET MATERIAL Joseph A. Wiese, Jr., and George Van Dyke Tiers, St.

Paul, Minn., assignors to Minnesota Mining and Manufacturing Company, St. Paul, Minn. No Drawing. Filed Nov. 16, 1970, Ser. No. 90,117

Int. Cl. B41m /22 US. Cl. 117-36.8 5 Claims ABSTRACT OF THE DISCLOSURE Colored sheet material, preferably in clear film form, contains an amine-reactive dye and a tetralkylammonium cyanoacetate salt dissolved in a binder. When subjected to a thermographically induced heat-pattern the color is permanently diminished or destroyed, producing a visible image and, when using the preferred film product, a negative projection transparency.

This invention relates to heat-sensitive copy-sheets useful in the thermographic copying of differentially radiation-absorptive graphic originals. While not restricted thereto, the invention in a preferred embodiment consists of a transparent colored film which is at least changed in color and preferably rendered colorless at heated image areas, whereby to provide a negative projection transparency.

The copy-sheet consists generally of a carrier or support having on one surface a coating of a colored aminereactive dye and a tetraalkylammonium cyanoacetate salt dissolved in a film-forming non-reactive binder. Paper is useful as a carrier but transparent heat-resistant films, of which Mylar polyester film is an excellent example, are preferred; or the film-forming binder may itself serve as a carrier. Low concentrations of the dye are sufiicient to provide good color contrast while still permitting color projection and facilitating color change or disappearance of color. Polyvinyl chloride-acetate is a preferred binder material, both the dye and the salt in the amounts used being fully soluble therein to provide a clear colored non-light-difiusing film. Polyvinyl acetate, ethyl cellulose and cellulose acetate are also useful.

In an example, a thin transparent Mylar polyester film is coated over one surface with a three mil layer of a composition containing 0.075 gm. of Genacryl Red 6B (Color Index 48020) and two drops of a solution, of one gram of tetraethylammonium cyanoacetate in two grams of 95% ethyl alcohol, in five grams of a solution of ten grams of VYHH polyvinyl chloride-acetate in 90 grams of methyl ethyl ketone. The dry coating is a clear intense magenta. The film is placed against a printed original which is then briefly exposed to intense infra-red radiation in a thermographic copying machine. The areas of the film corresponding to the printed areas are bleached and rendered clear and transparent. Projection from an overhead projector produces a clear white image against a magenta background on the projection screen. No apparent change is noted after several hours of image projection.

In another example the magenta dye is replaced with a mixture of 0.025 gm. of Color Precursor No. 1 and 0.100 gm. of dichloromaleic acid to produce a cyan colored film which yields a clear colorless image. As the acid component may be used a chemically equivalent 3,684,552 Patented Aug. 15, 1972 'ice amount of any organic acid having a pKa value less than 4.0. Another color precursor which may be similarly acidified to provide a useful color body is bis-(4-dimethylaminophenyl)-carbinol. Similarly, substitution of Genacryl Yellow SGF (CI 48065) for the magenta dye produces an intense yellow film and a clear colorless image. These several films may therefore be combined to provide any desired image or background color or combination of colors.

Other color bodies which have been found useful in the practice of the invention include Genacryl Pink 6G (CI 48015), and acidified Color Precursors X-4405 and X- 4406. These and other effective color bodies are identified, for the purposes of this invention, as decolorizable by brief heating in dilute solution in an inert solvent in the presence of a small amount of a mixture of one mole of tetrabutylammonium cyanoacetate and four moles of cyanoacetic acid.

The characterizing test is run as follows. A least amount of the color body suflicient to give a distinctive color to the solution is dissolved in 2 /2 ml. of 3-methylsulfolane. To the solution is added one drop of one molal solution of cyanoacetic acid and two drops of one-tenth molal solution of tetrabutyl ammonium hydroxide (2.5 gm. of the reagent in gm. of dioxane and 7.5 gms. of methanol). The solution is heated at 150 C. in a closed vial. A gross change in color, or disappearance of color, within not more than four minutes shows the color body to be effective for the purposes of this invention.

Tetramethyl ammonium cyanoacetate and tetraethyl ammonium cyanoacetate are preferred salts for use in the sheet materials of the invention. Other useful but somewhat less elfective salts include tetramethyl guanidinium cyanoacetate, tetramethylammonium sec-butyl cyanoacetate, diphenylguanidinium cyanoacetate, methylenediamine cyanoacetate, octadecyl dimethyl ammonium cyanoacetate. More generally, there is used a salt of a moderately strong organic nitrogenous base, having a pKb value no greater than about 4.0 and a boiling point of at least about C. or preferably C., and cyanoacetic acid or an alpha-alkyl-substituted cyanoacetic acid. However the tetraalkylammonium cyanoacetates are readily available, produce rapid and complete decolorization of the most useful color bodies, and are greatly preferred.

What is claimed is as follows:

1. A heat-sensitive copy-sheet including a heat-decolorizable color layer containing, in solution in a non-reactive film-forming binder, (a) a salt of an organic nitrogenous base, having a pKb value no greater than about 4.0 and a boiling point of at least about 100 C., and cyanoacetic acid or alpha-alkyl-substituted cyanoacetic acid, and (b) an amine-reactive color body characterized by its ability to undergo rapid reduction in color in solution in an inert solvent on heating in presence of a reactant solution containing a 1:4 molal ratio of tetrabutylammonium cyanoacetate and cyanoacetic acid.

2. Copy-sheet of claim 1 wherein said salt is a tetraalkylammonium cyanoacetate.

3. Copy-sheet of claim 1 wherein said color layer is transparent and non-light-diifusing.

4. Copy-sheet of claim 3 wherein said layer is supported on a transparent heat-resistant carrier film.

5. Copy-sheet of claim 4 wherein said color body is Genacryl Red 6B, Color Precursor No. 1 acidified with an organic acid having a pKa value less than about 4.0, or Genacryl Yellow 5GP.

References Cited UNITED STATES PATENTS 3,166,583 1/1965 Martin et a1. l1736.8 3,293,061 12/1966 Lawton 117--36.8

3,413,138 11/1968 Georgalas l17--36.8

4 Futaki 117-368 Berg et a1. 117 36.2 Small 11736.8 Wiese et a1 117-36.9

MURRAY KATZ, Primary Examiner US. Cl. X.R.

117--138.8 F, 155 UA

Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US3852093 *Dec 13, 1972Dec 3, 1974Minnesota Mining & MfgHeat-sensitive copy-sheet
US5258274 *May 22, 1992Nov 2, 1993Minnesota Mining And Manufacturing CompanyAlkoxystyryl substituted indolinium dye and thermal nucleophile-generating agent; photography
US5266452 *Apr 30, 1992Nov 30, 1993Minnesota Mining And Manufacturing CompanyPhotographic element containing a thermal dye bleach system
US5306686 *May 4, 1992Apr 26, 1994Minnesota Mining And Manufacturing CompanyNegative-acting thermographic materials
US5314795 *Dec 21, 1992May 24, 1994Minnesota Mining And Manufacturing CompanyThermal-dye-bleach construction comprising a polymethine dye and a thermal carbanion-generating agent
US5324627 *Dec 21, 1992Jun 28, 1994Minnesota Mining And Manufacturing CompanyThermal carbanion generating agent
US5384237 *Jan 25, 1994Jan 24, 1995Minnesota Mining And Manufacturing CompanyQuaternary-ammonium phenylsulfonylacetate thermal-dye-bleach agents
US5395747 *Dec 20, 1993Mar 7, 1995Minnesota Mining & Manufacturing CompanyPolylactones as stabilizers in antihalation systems where an anion is thermally generated to decolor dyes formed by scattered light
DE3808802A1 *Mar 16, 1988Sep 29, 1988Fuji Photo Film Co LtdWaermeempfindliches aufzeichnungsmaterial
EP0138741A2 *Aug 21, 1984Apr 24, 1985Matsumoto Kosan Kabushiki KaishaTemperature-indicating sheet
EP0605285A1 *Dec 20, 1993Jul 6, 1994Minnesota Mining And Manufacturing CompanyTetra-alkylammonium phenylsulfonylacetate thermal-dye-bleach agents
Classifications
U.S. Classification428/483, 428/918, 428/913
International ClassificationG03F1/00, B41M5/28
Cooperative ClassificationY10S428/913, Y10S428/918, G03F1/00, B41M5/28
European ClassificationG03F1/00, B41M5/28