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WO1994016904A1 - A heat sensitive imaging element - Google Patents

A heat sensitive imaging element Download PDF

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Publication number
WO1994016904A1
WO1994016904A1 PCT/EP1993/003635 EP9303635W WO9416904A1 WO 1994016904 A1 WO1994016904 A1 WO 1994016904A1 EP 9303635 W EP9303635 W EP 9303635W WO 9416904 A1 WO9416904 A1 WO 9416904A1
Authority
WO
WIPO (PCT)
Prior art keywords
imaging element
film layer
amino
methyl
image
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.)
Ceased
Application number
PCT/EP1993/003635
Other languages
French (fr)
Inventor
Wolfgang Podszun
Robert Bloodworth
Herman Jozef Uytterhoeven
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.)
Agfa Gevaert NV
Original Assignee
Agfa Gevaert NV
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 Agfa Gevaert NV filed Critical Agfa Gevaert NV
Publication of WO1994016904A1 publication Critical patent/WO1994016904A1/en
Anticipated expiration legal-status Critical
Ceased 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
    • B41M5/40—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
    • 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
    • B41M5/305—Thermography ; Marking by high energetic means, e.g. laser otherwise than by burning, and characterised by the material used using chemical colour formers with reversible electron-donor electron-acceptor compositions
    • 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
    • B41M5/3335—Compounds containing phenolic or carboxylic acid groups or metal salts thereof
    • 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
    • B41M5/41—Base layers supports or substrates
    • 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
    • B41M2205/04—Direct thermal recording [DTR]
    • 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
    • B41M2205/40—Cover layers; Layers separated from substrate by imaging layer; Protective layers; Layers applied before imaging
    • 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
    • B41M5/323—Organic colour formers, e.g. leuco dyes
    • 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
    • B41M5/323—Organic colour formers, e.g. leuco dyes
    • B41M5/327—Organic colour formers, e.g. leuco dyes with a lactone or lactam ring
    • B41M5/3275—Fluoran compounds
    • 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
    • B41M5/337—Additives; Binders
    • B41M5/3372—Macromolecular compounds

Definitions

  • This invention relates to an imaging element that can be imaged by means of heat, and to a method of protecting said imaging elements, and more particularly to imaging elements for the preparation of negative copies of graphic images.
  • the invention relates to coloured imaging products which are decolourised by brief heating to thermographic copying temperatures. Such products are useful e.g. in the preparation of negative colour projection transparencies, e.g. by thermal printers.
  • the coloured reaction product can be decolourized simply by heating, the acid component being readily removed and the coloured imaging body becomes returned to a colourless or leuco state.
  • the above imaging elements are inherently unstable and are difficult to store both before use, and after receiving a graphic image.
  • the present invention provides a more stable thermographic imaging element containing a heat-decomposable coloured reaction product of a dye precursor and a volatizable organic acid.
  • an imaging element comprising a support having a colour layer of polymeric binder including a reaction product of a dye-precursor and a volatizable organic acid, characterised in that the colour layer is covered by a transparent polymeric film layer containing compounds having amino groups.
  • the film layer polymer and/or copolymer has a glass transition temperature (Tg) of at least 60° C and preferably about 80° C.
  • Tg glass transition temperature
  • the film layer is formed from amino modified polysaccharide for example, amino modified dextran or an amino modified pullulan as disclosed in EP-A-514990.
  • Pullulan is a polysaccharide that is produced by micro-organisms of the Aureobasidium pullans type (Pullaria pullulans) and that contains maltotriose repeating units connected by an «_ -1,6 glycosidic bond. Pullulan is generally produced on an industrial scale by the fermentation of partially hydrolysed starch or by bacterial fermentation of sucrose . Pullulan is commercially available from Shodex Pharmacosmos.
  • amino containing materials are amino modified cellulose (both natural and synthetic ) , homo- and co-polymers of vinylmonomers having an amino group, amino modified methacrylates e.g. a methacrylate co-polymer including at least 25% by weight of N-tert-butylamino ethyl methacrylate. Low molecular weight amino group containing compounds may also be added to the polymeric film layer.
  • the cover layer may contain additives such as matting agents, ultra-violet radiation absorbers, and anti-oxidants.
  • an imaging element comprising a support having a colour layer of polymeric binder including a reaction product of a dye precursor and a volatizable organic acid, characterised in that the colour layer is coated with a polymeric film layer containing compounds having amino groups.
  • the film layer is applied as an aqueous dispersion or solution of polymeric material.
  • triarylmethanelactone compounds such as 3,3-bis (p-dimethylaminophenyl)-6- dimethylaminophthalide, 3,3-bis (p-dimethylaminophenyl)phthalide, 3- (p-dimethylaminophenyl) 3-(1,2-dimethylindole-3-yl)phthalide, 3-(p- dimethylaminophenyl) -3-(2-methylindole-3-yl)phthalide, 3,3-bis (1,2- dimethylindole-3-yl)-5-dimethylaminophthalide, 3,3-bis (1,2- dimethylindole-3-yl)-6-dimethylaminophthalide, 3,3-bis (9- ethylcarbazole-3-yl) -6-dimethylaminophthalide, 3,3-bis (2- phenylindole-3-yl)-6-d
  • Still further dye precursors for use in connection with the present invention are disclosed in e.g. US-P-4.803.148, EP-A-302529, DE-A-3.807.744, DE-A-3.942.227, DE-A-3.810.207, US-P4.753.759 and the references cited therein.
  • the dye precursors may be used either solely or in combination.
  • the dye precursor and colour developer are arranged in a polymeric layer on the support of the imaging element.
  • binders for these layers there can be used e.g. polyesters, polyamides, e.g. N-methoxymethyl polyhexamethylene adipamide, vinylidene chloride copolymers, e.g. vinylidene chloride/acrylonitrile, vinylidene chloride/methylacrylate and vinylidene chloride/vinylacetate copolymers etc., ethylene/vinyl acetate copolymers, cellulosic ethers, e.g. methyl cellulose, ethyl cellulose and benzyl cellulose, polyethylene, synthetic rubbers, e.g.
  • butadiene/acrylonitrile copolymers and chloro-2-butadiene-l,3 polymers, cellulose esters, e.g. cellulose acetate, cellulose acetate succinate and cellulose acetate butyrate, cellulose nitrate, polyvinyl esters, e.g. polyvinyl acetate/acrylate, polyvinyl acetate/methacrylate and polyvinyl acetate, polyacrylate and alpha-alkyl polyacrylate esters, e.g. polymethyl methacrylate and polyvinyl acetate, high molecular weight polyethylene oxides of polyglycols having average molecular weights from about 4,000 to 1, 000, 000,.
  • cellulose esters e.g. cellulose acetate, cellulose acetate succinate and cellulose acetate butyrate, cellulose nitrate
  • polyvinyl esters e.g. polyvinyl acetate/acrylate, polyvinyl acetate/
  • polyvinyl chloride and copolymers e.g. polyvinyl chloride/acetate, polyvinylchloride/acetate/alkohol, polyvinyl acetal, e.g. polyvinyl butyral, polyvinyl formal, polyformaldehydes, polyurethanes and copolymers, polycarbonate and copolymers, polystyrenes and copolymers e.g.
  • polystyrene/acrylonitrile polystyrene/acrylonitrile/butadiene
  • polyvinyl alcohol polystyrene/acrylonitrile
  • cellulose polystyrene/acrylonitrile/butadiene
  • polyvinyl alcohol polyvinyl alcohol
  • cellulose anhydrous gelatin
  • phenolic resins and melamine-formaldehyde resins etc. or mixtures of one ore more of the above polymers.
  • Suitable supports for the imaging element in connection with the present invention are supports that are stable at the heating temperatures used for image-wise or overall heating the imaging element to obtain an image.
  • useful supports are e.g. polyester film supports e.g. polyethylene terephthalate, glass, wood, paper, polyethylene coated paper, cellulose esters e.g. cellulose acetate, cellulose propionate, cellulose butyrate, poly carbonate, polyvinyl chloride, polyimide, polypropylene etc.
  • An adhesive layer (sometimes called a subbing layer ) may be placed between the support and the colour layer.
  • the colour layer may be imaged under thermographic copying procedures in which the colour disappears at the heated image areas. This may be achieved by use of a thermal head , or by using laser techniques together with an imaging element capable of converting light into heat by use of a suitable colour complex in the colour layer or an additional light sensitive substance.
  • Leuco dye L-2 (formula see below) 2.50%
  • Copolymer (vinyl chloride/vinyl acetate) (SOLVIC 560 RA, Solvay) 1.50%
  • Leuco dye L-3 (formula see below) 2.50%
  • Polymer dispersion F (water) 3.00%
  • Polymer dispersion G (water) 3.00% Copolymer of 75% methyl methacrylate 25% ethyl methacrylate
  • the dye solution and the polymer solution or dispersion respectively were coated with a wet film thickness of 50 ⁇ each in the described order on a polyethylene terephthalate base with a thickness of 63 ⁇ m and dried at 50° C to leave a coloured coating or layer.
  • Each of the samples was imaged with a thermal head, causing the coloured layer to discolour in the heat imaged areas ,in a Hitachi VY 100 videoprinter.
  • the density in the image-areas (Dmax) and non- image areas (Dmin) of each of the obtained images was then measured.
  • the polymeric protection film prevents escape of the acid which can then re-react with the dye precursor to maintain the coloured layer.
  • the amino groups in the polymer reacts with any released acid to tip the equilibrium and cause a faster imaging reaction to give improved images.
  • the protective film layer becomes sufficiently porous to allow volatilization of the acid to form the image.
  • reaction between the acid and the amino polymer help create an additional barrier to the volatilization of the acid during storage.

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  • Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • General Chemical & Material Sciences (AREA)
  • Heat Sensitive Colour Forming Recording (AREA)

Abstract

An imaging element comprising a support having a colour layer of polymeric binder including a reaction product of a dye precursor and volatizable organic acid. When subjected to heat imaging during thermographic copying the coloured compound decomposes and the liberated acid volatilizes leaving a clear transparent image. The image can be stabilized by covering the colour layer with a clear transparent polymeric film layer containing compounds having amino groups such as amino modified polysaccharides.

Description

A HEAT SENSITIVE IMAGING ELEMENT.
DESCRIPTION
1. Field of the invention.
This invention relates to an imaging element that can be imaged by means of heat, and to a method of protecting said imaging elements, and more particularly to imaging elements for the preparation of negative copies of graphic images.
2. Background of Invention
The invention relates to coloured imaging products which are decolourised by brief heating to thermographic copying temperatures. Such products are useful e.g. in the preparation of negative colour projection transparencies, e.g. by thermal printers.
Such a product is described in US Patent 3609360 in which a carrier sheet is coated with a thin uniform colour layer of polymeric binder containing a heat-decomposable coloured reaction product of a dye-precursor and a volatizable acid.
The coloured reaction product can be decolourized simply by heating, the acid component being readily removed and the coloured imaging body becomes returned to a colourless or leuco state.
The above imaging elements are inherently unstable and are difficult to store both before use, and after receiving a graphic image.
3. Ob ect of the Invention
The present invention provides a more stable thermographic imaging element containing a heat-decomposable coloured reaction product of a dye precursor and a volatizable organic acid.
4. Statement of Invention
According to the invention there is provided an imaging element comprising a support having a colour layer of polymeric binder including a reaction product of a dye-precursor and a volatizable organic acid, characterised in that the colour layer is covered by a transparent polymeric film layer containing compounds having amino groups.
Preferably the film layer polymer and/or copolymer has a glass transition temperature (Tg) of at least 60° C and preferably about 80° C.
Conveniently the film layer is formed from amino modified polysaccharide for example, amino modified dextran or an amino modified pullulan as disclosed in EP-A-514990. Pullulan is a polysaccharide that is produced by micro-organisms of the Aureobasidium pullans type (Pullaria pullulans) and that contains maltotriose repeating units connected by an «_ -1,6 glycosidic bond. Pullulan is generally produced on an industrial scale by the fermentation of partially hydrolysed starch or by bacterial fermentation of sucrose . Pullulan is commercially available from Shodex Pharmacosmos.
Other amino containing materials are amino modified cellulose ( both natural and synthetic ) , homo- and co-polymers of vinylmonomers having an amino group, amino modified methacrylates e.g. a methacrylate co-polymer including at least 25% by weight of N-tert-butylamino ethyl methacrylate. Low molecular weight amino group containing compounds may also be added to the polymeric film layer.
The cover layer may contain additives such as matting agents, ultra-violet radiation absorbers, and anti-oxidants.
Also according to the invention there is provided a method of improving the longevity of an imaging element comprising a support having a colour layer of polymeric binder including a reaction product of a dye precursor and a volatizable organic acid, characterised in that the colour layer is coated with a polymeric film layer containing compounds having amino groups.
Preferably the film layer is applied as an aqueous dispersion or solution of polymeric material.
As dye precursors comprised in the imaging element according to the present invention, there are exemplified triarylmethanelactone compounds such as 3,3-bis (p-dimethylaminophenyl)-6- dimethylaminophthalide, 3,3-bis (p-dimethylaminophenyl)phthalide, 3- (p-dimethylaminophenyl) 3-(1,2-dimethylindole-3-yl)phthalide, 3-(p- dimethylaminophenyl) -3-(2-methylindole-3-yl)phthalide, 3,3-bis (1,2- dimethylindole-3-yl)-5-dimethylaminophthalide, 3,3-bis (1,2- dimethylindole-3-yl)-6-dimethylaminophthalide, 3,3-bis (9- ethylcarbazole-3-yl) -6-dimethylaminophthalide, 3,3-bis (2- phenylindole-3-yl)-6-dimethylaminophthalide, 3-p- dimethylaminophenyl-3-(1-methylaminophthalide and the like; diphenylmethane compounds such as 4,4-bis-dimethylaminobenzhydryl benzyl ether, N-halophenyl-leuσoauramine, N-2,4,5-trichlorophenyl- leuσoauramine and the like; thiazine compounds such as benzoyl- leucomethylene bleu, p-nitrobenzoyl-leucomethylene blue and the like; spiro compounds such as 3-methyl-spiro-dinaphthopyran, 3- ethyl-spiro-dinaphthopyran, 3-benzyl-spiro-dinaphthopyran, 3-methyl- naphtho-(6-methoxybenzo) spiropyran, 3-propyl-spiro-dibenzopyran and the like; lactam compounds such as Rhodamine-B anilinelactam, Rhodamine(p-nitroanilino) lactam, Rhodamine(o-chloroanilino) lactam and the like; and fluoran compounds such as 3-dimethylamino- 7methoxyfluoran, 3-diethylamino-6-methoxyfluoran, 3-diethylamino-7- methoxyfluoran, 3-diethylamino-6-methyl-7-chlorofluoran, 3- diethylamino-6,7-dimethylfluoran, 3-(N-ethyl-p-toluidino)-7- methyIfluoran, 3-diethylamino-7-N-acetyl-N-methylaminofluoran, 3- diethylamino-7-N-methylaminofluoran, 3-diethylamino-7—dibenzylamino- 7-N-methyl-N-benzylaminofluoran, 3-diethylamino-7-N-chloroethyl-N- methylaminofluoran, 3-diethylamino-7-N-diethylaminofluoran, 3-(N- ethyl-p-toluidino)-6-methyl-7-phenylaminofluoran, 3-(N-ethyl-p- toluidino)-6-methyl-7-(p-toluidino) fluoran, 3-diethylamino-6-methyl- 7-phenylaminofluoran, 3—di-n-butylaminofluoran, 3-diethylamino-7-(2- carbomethoxyphenylamino) fluoran, 3-(N-cyclohexyl-N—methyla ino)-6- methyl-7-phenylaminofluoran, 3-(N-cyclopentyl-N-methylamino) —6- methyl-7-phenylaminofluoran, 3-(N-cyclopentyl-N-ethylamino) -6- methyl-7-phenylaminofluoran, 3-(N-cyclohexyl-N-ethylamino) -6-methyl- 7-phenylaminofluoran, 3-(N-3' ,3' ,5'-trimethylcyclohexyl-N- methylamino)-6-methyl-7-phenylaminofluoran, 3-pyrrolidino-6-methyl- 7-phenylaminofluoran, 3-piperidino-6-methyl-7-phenylaminofluoran, 3- diethylamino-6-methyl-7-xylidinofluoran, 3-diethylamino-7-(o- chlorophenylamino)-fluoran, 3-dibutylamino-7-(o- chlorophenylamino) fluoran, 3-pyrrolidino-6-methyl-7-p-butylphenyl aminofluoran, 3-diethylamino-7-(o-fluorophenylamino) fluoran, 3- dibutylamino-7-(o-fluorophenylamino) fluoran, 3-(N-methyl-N-n- amyl) amino-6-methyl-7-phenylaminofluoran, 3-(N-ethyl-N-n-amyl) amino- 6-methyl-7-phenylaminofluoran, 3-(N-methyl-N-n-hexyl) amino—6-methyl- 7-phenylaminofluoran, 3-(N-ethyl-N-n-hexyl) amino-6-methyl-7- phenylaminofluoran, 3-(N-ethyl-N-6-ethylhexyl)-amino-6-methyl-7- phenylaminofluoran, 3-(N-ethyl-N-tetrahydrofurfurylamino)-6-methyl- 7-phenylfluoran and the like. Still further dye precursors for use in connection with the present invention are disclosed in e.g. US-P-4.803.148, EP-A-302529, DE-A-3.807.744, DE-A-3.942.227, DE-A-3.810.207, US-P4.753.759 and the references cited therein. The dye precursors may be used either solely or in combination.
Among the colour developers, there are many volatizable acidic compounds which develop a colour by contacting with the above dye precursors, for example, salicylic acid, oxallic acid, benzoic acid.
According to the present invention the dye precursor and colour developer are arranged in a polymeric layer on the support of the imaging element. As binders for these layers there can be used e.g. polyesters, polyamides, e.g. N-methoxymethyl polyhexamethylene adipamide, vinylidene chloride copolymers, e.g. vinylidene chloride/acrylonitrile, vinylidene chloride/methylacrylate and vinylidene chloride/vinylacetate copolymers etc., ethylene/vinyl acetate copolymers, cellulosic ethers, e.g. methyl cellulose, ethyl cellulose and benzyl cellulose, polyethylene, synthetic rubbers, e.g. butadiene/acrylonitrile copolymers, and chloro-2-butadiene-l,3 polymers, cellulose esters, e.g. cellulose acetate, cellulose acetate succinate and cellulose acetate butyrate, cellulose nitrate, polyvinyl esters, e.g. polyvinyl acetate/acrylate, polyvinyl acetate/methacrylate and polyvinyl acetate, polyacrylate and alpha-alkyl polyacrylate esters, e.g. polymethyl methacrylate and polyvinyl acetate, high molecular weight polyethylene oxides of polyglycols having average molecular weights from about 4,000 to 1, 000, 000,. polyvinyl chloride and copolymers, e.g. polyvinyl chloride/acetate, polyvinylchloride/acetate/alkohol, polyvinyl acetal, e.g. polyvinyl butyral, polyvinyl formal, polyformaldehydes, polyurethanes and copolymers, polycarbonate and copolymers, polystyrenes and copolymers e.g. polystyrene/acrylonitrile, polystyrene/acrylonitrile/butadiene, polyvinyl alcohol, cellulose, anhydrous gelatin, phenolic resins and melamine-formaldehyde resins etc., or mixtures of one ore more of the above polymers.
Suitable supports for the imaging element in connection with the present invention are supports that are stable at the heating temperatures used for image-wise or overall heating the imaging element to obtain an image. Examples of useful supports are e.g. polyester film supports e.g. polyethylene terephthalate, glass, wood, paper, polyethylene coated paper, cellulose esters e.g. cellulose acetate, cellulose propionate, cellulose butyrate, poly carbonate, polyvinyl chloride, polyimide, polypropylene etc.
An adhesive layer ( sometimes called a subbing layer ) may be placed between the support and the colour layer.
The colour layer may be imaged under thermographic copying procedures in which the colour disappears at the heated image areas. This may be achieved by use of a thermal head , or by using laser techniques together with an imaging element capable of converting light into heat by use of a suitable colour complex in the colour layer or an additional light sensitive substance.
The present invention is illustrated by the following examples without however limiting it thereto. All parts are by weight unless otherwise specified.
EXAMPLES
The following coating solutions were used in the examples:
Coating solutions for the dye precursor layer
Dye solution A (methyl ethyl ketone) :
Leuco dye L-l (formula see below) 2.50%
Salicylic acid 1.25%
Copolymer (vinyl chloride/vinyl acetate) (SOLVIC 560 RA, marketed by Solvay) 1.50%
Dye solution B (methyl ethyl ketone) :
Leuco dye L-2 (formula see below) 2.50%
Salicylic acid 1.25%
Copolymer (vinyl chloride/vinyl acetate) (SOLVIC 560 RA, Solvay) 1.50%
Dye solution C (methyl ethyl ketone) :
Leuco dye L-3 (formula see below) 2.50%
Salicylic acid 1.25%
Copolymer (vinyl chloride/vinyl acetate ) (SOLVIC 560 RA, Solvay) 1.50%
Coating polymer solutions/dispersions for the protective film layer.
Polymer solution D (water)
Amino modi ied dextran 3.00% containing -O-C-NH-(CH2 ) 2~N~ (CΆ2 - 2~NH2^ 2 9rouPs O Polymer dispersion E (water) 3.00%
Copolymer of 43% methyl methacrylate
27% ethyl hexyl acrylate
30% N-tert-butylaminoethyl methacrylate
Polymer dispersion F (water) 3.00%
Copolymer of 45% methyl methacrylate 15% ethyl hexyl acrylate 40% N-tert-butylaminoethyl methacrylate
Polymer dispersion G (water) 3.00% Copolymer of 75% methyl methacrylate 25% ethyl methacrylate
Formulas of the dye precursors used:
Leuco dye L-l
Figure imgf000008_0001
L-2
Figure imgf000008_0002
Leuco dye L— 3
Figure imgf000009_0001
Preparations 1 - 7
The dye solution and the polymer solution or dispersion respectively were coated with a wet film thickness of 50 μ each in the described order on a polyethylene terephthalate base with a thickness of 63 μm and dried at 50° C to leave a coloured coating or layer.
Preparation no. Dye solution Polymer solution/ dispersion
D D D E
F
Figure imgf000009_0002
Each of the samples was imaged with a thermal head, causing the coloured layer to discolour in the heat imaged areas ,in a Hitachi VY 100 videoprinter. The density in the image-areas (Dmax) and non- image areas (Dmin) of each of the obtained images was then measured.
The samples were then stored for 1 week at 60°C and the Dmax of image-areas was measured again for comparison with the original values. Preparation no.
1
2
3
4
5
6 (comparison
7 (comparison
Figure imgf000010_0001
From the above table it can be seen that the images obtained with the samples 1 to 5 according to the invention were effectively stabilized against heat during storage. Whereas sample 6 a prior art sample without the protective coating was so unstable as to have lost its image during storage at an elevated temperature. Further sample 7 with a protective coating containing no compounds having amino groups did not provide a good image.
The polymeric protection film prevents escape of the acid which can then re-react with the dye precursor to maintain the coloured layer.
With the compound having amino groups present in the protective film layer, preferably in the form of an amino polymer, the amino groups in the polymer reacts with any released acid to tip the equilibrium and cause a faster imaging reaction to give improved images.
During thermal imaging the protective film layer becomes sufficiently porous to allow volatilization of the acid to form the image.
Further the reaction between the acid and the amino polymer help create an additional barrier to the volatilization of the acid during storage.

Claims

1. An imaging element comprising a support having a colour layer of polymeric binder including a reaction product of a dye-precursor and a volatizable organic acid, characterised in that the colour layer is covered by a transparent polymeric film layer containing compounds having amino groups.
2. An imaging element as claimed in Claim 1, characterised in that the film layer is formed from an amino containing polymer.
3. An imaging element as claimed in Claim 2 characterised in that the film layer is formed from an amino modified polysaccharide.
4. An imaging element as claimed in Claim 3 characterised in that the film layer is formed from an amino modified dextran.
5. An imaging element as claimed in Claim 2, characterised in that the film layer is a methacrylate co-polymer including at least 25% by weight of N-tert-butylamino ethyl methacrylate.
6. A method of improving the longevity of an imaging element comprising a support having a colour layer of polymeric binder including a reaction product of a dye precursor and a volatizable organic acid, characterised in that the colour layer is coated with a polymeric film layer containing compounds having amino groups.
7. A method for making an image comprising image-wise heating an imaging element as defined in any of claims 1 to 5.
8. A method according to claim 7 wherein a thermal head is used for image-wise heating said imaging element.
PCT/EP1993/003635 1993-01-28 1993-12-16 A heat sensitive imaging element Ceased WO1994016904A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
EP93200214 1993-01-28
EP93200214.0 1993-01-28

Publications (1)

Publication Number Publication Date
WO1994016904A1 true WO1994016904A1 (en) 1994-08-04

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PCT/EP1993/003635 Ceased WO1994016904A1 (en) 1993-01-28 1993-12-16 A heat sensitive imaging element

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WO (1) WO1994016904A1 (en)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1065049A1 (en) * 1999-06-29 2001-01-03 Agfa-Gevaert N.V. Heat-sensitive imaging element with cover layer for providing a lithographic printing plate
US6503684B1 (en) 1999-06-29 2003-01-07 Agfa-Gevaert Processless thermal printing plate with cover layer containing compounds with cationic groups

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0179492A2 (en) * 1984-10-25 1986-04-30 Kanzaki Paper Manufacturing Company Limited Heat-sensitive recording material
EP0400485A2 (en) * 1989-05-24 1990-12-05 Kanzaki Paper Manufacturing Co., Ltd. Heat-sensitive recording material
EP0492628A1 (en) * 1990-12-26 1992-07-01 Ricoh Company, Ltd Reversible thermosensitive coloring composition, recording medium, recording method and image display apparatus using the recording medium

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0179492A2 (en) * 1984-10-25 1986-04-30 Kanzaki Paper Manufacturing Company Limited Heat-sensitive recording material
EP0400485A2 (en) * 1989-05-24 1990-12-05 Kanzaki Paper Manufacturing Co., Ltd. Heat-sensitive recording material
EP0492628A1 (en) * 1990-12-26 1992-07-01 Ricoh Company, Ltd Reversible thermosensitive coloring composition, recording medium, recording method and image display apparatus using the recording medium

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1065049A1 (en) * 1999-06-29 2001-01-03 Agfa-Gevaert N.V. Heat-sensitive imaging element with cover layer for providing a lithographic printing plate
US6503684B1 (en) 1999-06-29 2003-01-07 Agfa-Gevaert Processless thermal printing plate with cover layer containing compounds with cationic groups

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