Thermal imaging process and products using image rigidification

Abstract

Improved processes and products for laser thermal imaging are described. These improved processes and products utlilize an image rigidification element and significantly reduce halftone dot movement, swath boundary cracking and banding.

What is claimed is:  
     
         1 . A method for making a color image comprising: 
 (1) imagewise exposing to laser radiation a laserable assemblage comprising: 
 (A) the thermally imageable element comprising a thermally imageable layer; and  
 (B) a receiver element in contact with the thermally imageable layer of the thermally imageable element; the receiver element comprising: 
 (a) an image receiving layer; and  
 (b) an receiver support;  
 whereby the exposed areas of the thermally imageable layer are transferred to the receiver element to form a colored image on the image receiving layer;  
 
   (2) separating the thermally imageable element (A) from the receiver element (B), thereby revealing the colored image on the image receiving layer of the receiver element;    (3) contacting the colored image on the image receiving layer of the receiver element with an image rigidification element comprising: 
 (c) a support having a release surface, and  
 (d) a thermoplastic polymer layer,  
 the colored image being adjacent to the thermoplastic polymer layer during said contacting whereby the color image is encased between the thermoplastic polymer layer and the image receiving layer of the receiving element;  
   (4) removing the support having a release surface thereby revealing the thermoplastic polymer layer; and    (5) contacting the revealed thermoplastic polymer layer from step (4) with a permanent substrate.    
     
     
         2 . The method of  claim 1  wherein the receiver support is transparent.  
     
     
         3 . The method of  claim 1  further comprising: 
 (1) removing the receiver support.  
 
     
     
         4 . The method of  claim 1  wherein the permanent substrate is paper.  
     
     
         5 . The method of  claim 1  wherein the permanent substrate is a polyester film.  
     
     
         6 . The method of  claim 1  wherein the exposure step is effected at a laser fluence of at most 600 mJ/cm 2 .  
     
     
         7 . The method of  claim 1  wherein the thermally imageable element is prepared by coating the thermally imageable layer on a base element.  
     
     
         8 . The method of  claim 7  wherein the thermally imageable layer is applied as an aqueous coating.  
     
     
         9 . The method of  claim 7  wherein the base element comprises: 
 (a) an ejection or subbing layer; and  
 (b) a heating layer.  
 
     
     
         10 . The method of  claim 9  wherein (a) is an ejection layer.  
     
     
         11 . The method of  claim 9  wherein (a) is an subbing layer.  
     
     
         12 . The method of  claim 7  wherein the base element comprises: 
 (a) a heating layer, and  
 (b) a base element support.  
 
     
     
         13 . The method of  claim 1  or  3  wherein the thermally imageable element comprises a colorant and a polymeric binder.  
     
     
         14 . The method of  claim 13  wherein the polymeric binder is a low decomposition temperature polymer having a decomposition temperature greater than about 350° C.  
     
     
         15 . The method of  claim 13  wherein the colorant comprises a pigment dispersion.  
     
     
         16 . The method of  claim 13  wherein the colorant comprises a dye.  
     
     
         17 . The method of  claim 1  or  3  wherein the thermally imageable element or the image receiving layer of the receiver element comprises a thermal amplification additive.  
     
     
         18 . The method of  claim 17  wherein the thermal amplification additive is selected from the group consisting essentially of diazo alkyls, diazonium salts, azido (—N3) compounds; ammonium salts; oxides which decompose to form oxygen; carbonates; peroxides and mixtures thereof.  
     
     
         19 . The method of  claim 17  wherein the thermal amplification additive is 4-diazo-N,N′ diethyl-aniline fluoroborate.  
     
     
         20 . The method of  claim 17  wherein the thermal amplification additive is an near infrared absorbing (NIR) dye.  
     
     
         21 . The method of  claim 17  wherein the NIR dye is selected from the group consisting of poly(substituted) phthalocyanine compounds, metal-containing phthalocyanine compounds; cyanine dyes; squarylium dyes; chalcogenopyryioacrylidene dyes; croconium dyes; metal thiolate dyes; bis(chalcogenopyrylo) polymethine dyes; oxyindolizine dyes; bis(aminoaryl) polymethine dyes; merocyanine dyes; quinoid dyes and mixtures thereof.  
     
     
         22 . The method of  claim 1  or  3  wherein the image receiving layer of the receiver element comprises a crystalline polymer.  
     
     
         23 . The method of  claim 22  wherein the image receiving layer has a melting point of 50 to 64° C.  
     
     
         24 . The method of  claim 23  wherein the image receiving layer has a melting point of 56 to 64° C.  
     
     
         25 . The method of  claim 24  wherein the image receiving layer has a melting point of 58 to 62° C.  
     
     
         26 . The method of  claim 22  wherein the crystalline polymer is polycaprolactone.  
     
     
         27 . The method of  claim 1  or  3  wherein the image rigidification element support having a release surface comprises a support and a release layer.  
     
     
         28 . The method of  claim 27  wherein the release layer is selected from the group consisting of silicones; melamine acrylic resins; vinyl chloride polymers; vinyl chloride copolymers; vinyl acetate polymers; ; vinyl acetate copolymers; plasticized polyvinyl alcohols; ethylene; propylene polymers and propylene copolymers.  
     
     
         29 . The method of  claim 1  or  3  wherein the thermoplastic polymer is selected from the group consisting essentially of polyester, methacrylate, acrylate, polyvinylacetate, polyvinylbutyral, polyvinylformal, styrene-isoprene-styrene and styrene-ethylene-butylene-styrene polymers.  
     
     
         30 . The method of  claim 1  or  3  wherein the thermoplastic polymer is amorphous.  
     
     
         31 . The method of  claim 30  wherein the thermoplastic polymer has a Tg in the range of 30 to 150° C.  
     
     
         32 . The method of  claim 31  wherein the thermoplastic polymer has a Tg in the range of 40 to 70° C.  
     
     
         33 . The method of  claim 32  wherein the thermoplastic polymer has a Tg in the range of 40 to 55° C.  
     
     
         34 . The method of  claim 30  wherein the thermoplastic polymer is compatible with the image receiving layer.  
     
     
         35 . The method of  claim 30  wherein the thermoplastic polymer is polyester.  
     
     
         36 . The method of  claim 20  wherein the thermoplastic polymer layer comprises an NIR dye bleaching agent.  
     
     
         37 . The method of  claim 36  wherein the NIR dye bleaching agent is selected from the group consisting of amines, azo compounds, carbonyl compounds and, organometallic compounds, carbanions, peroxides, diacylperoxides, peroxy acids, hydroperoxides, persulfates, and halogen compounds.  
     
     
         38 . The method of  claim 1  or  3  further comprising before step (3): 
 (2a) repeating steps (1) to (2) at least once using a different thermally imageable element to from a colored image comprising at least two colors on the same image receiving layer.  
 
     
     
         39 . The method of  claim 38  wherein step (1) and (2) are repeated at least twice to form a colored image comprising at least four colors.  
     
     
         40 . The method of  claim 1  or  3  wherein contact of the colored image on the image receiving layer of the receiver element with the image rigidification element is accomplished by lamination.  
     
     
         41 . The method of  claim 40  wherein lamination takes place at speeds of at least 600 mm/min.  
     
     
         42 . The method of  claim 40  wherein lamination takes place at speeds of at least 800 mm/min.  
     
     
         43 . The method of  claim 1  or  3  wherein contact of the revealed thermoplastic polymer layer to the permanent substrate is accomplished by lamination.  
     
     
         44 . The method of  claim 43  wherein lamination takes place at speeds of at least 600 mm/min.  
     
     
         45 . A method of bleaching a polymethine type NIR dye contained in a laserable assemblage which comprises contacting the dye in the laserable assemblage with a oxidant type bleaching agent selected from the group consisting of hydrogen peroxide, organic peroxides, hexaaryl biimidazoles, halogenated organic compounds, persulfates, perborates, perphosphates, hypochlorites and azo compounds; whereby the NIR dye is bleached by the bleaching agent.  
     
     
         46 . An image proofing system comprising: 
 (a) a laser generated halftone dot color thermal image formed on a crystalline polymer layer, the crystalline polymer layer being located on a first temporary carrier; and    (b) a thermoplastic polymer layer laminated to the crystalline polymer layer whereby the color image is encased between the crystalline polymer layer and the thermoplastic polymer layer, the thermoplastic polymer layer being located on a second temporary carrier.    
     
     
         47 . The image proofing system of  claim 46  wherein the crystalline polymer is polycaprolactone.  
     
     
         48 . The image proofing system of  claim 47  wherein the crystalline polymer has a melting point of 50 to 64° C.  
     
     
         49 . The image proofing system of  claim 48  wherein the crystalline polymer has a melting point of 56 to 64° C.  
     
     
         50 . The image proofing system of  claim 49  wherein the crystalline polymer has a melting point of 58 to 62° C.  
     
     
         51 . The image proofing system of  claim 46  wherein the thermoplastic polymer has a Tg in the range of 30 to 150° C.  
     
     
         52 . The image proofing system of  claim 51  wherein the thermoplastic polymer has a Tg in the range of 40 to 70° C.  
     
     
         53 . The image proofing system of  claim 52  wherein the thermoplastic polymer has a Tg in the range of 40 to 55° C.  
     
     
         54 . The image proofing system of  claim 46  wherein the thermoplastic polymer is polyester.  
     
     
         55 . The image proofing system of  claim 46  wherein the first and second temporary carriers comprise polyester.  
     
     
         56 . The image proofing system of  claim 46  wherein the first and second temporary carriers have release surfaces.  
     
     
         57 . The image proofing system of  claim 46  wherein the crystalline polymer layer comprises an NIR dye.  
     
     
         58 . The image proofing system of  claim 57  wherein the thermoplastic polymer layer contains an NIR dye bleaching agent.  
     
     
         59 . A printed proof comprising: 
 (a) a laser generated halftone halftone dot color thermal image formed on a crystalline polymer layer; and    (b) a thermoplastic polymer layer is laminated on one surface to the crystalline polymer layer and on the other surface to a permanent substrate, whereby the color image is encased between the crystalline polymer layer and the thermoplastic polymer layer.    
     
     
         60 . The printed proof of  claim 59  wherein the crystalline polymer has a melting point of 50 to 64° C.  
     
     
         61 . The printed proof of  claim 60  wherein the crystalline polymer has a melting point of 56 to 64° C.  
     
     
         62 . The printed proof of  claim 61  wherein the crystalline polymer has a melting point of 58 to 62° C.  
     
     
         63 . A printed proof of  claim 59  wherein the crystalline polymer is polycaprolactone.  
     
     
         64 . The printed proof of  claim 59  wherein the thermoplastic polymer has a Tg in the range of 30 to 150° C.  
     
     
         65 . The method of  claim 64  wherein the thermoplastic polymer has a Tg in the range of 40 to 70° C.  
     
     
         66 . The method of  claim 65  wherein the thermoplastic polymer has a Tg in the range of 40 to 55° C.  
     
     
         67 . The printed proof of  claim 59  wherein the thermoplastic polymer is polyester.  
     
     
         68 . The printed proof of  claim 59  wherein the color image comprises a pigment.  
     
     
         69 . The printed proof of  claim 59  wherein the color image comprises a dye.  
     
     
         70 . The printed proof of  claim 59  wherein the color image contains an NIR dye.  
     
     
         71 . The printed proof of  claim 70  wherein the thermoplastic polymer layer contains a dye bleaching agent which has effectively bleached the NIR dye.  
     
     
         72 . The printed proof of  claim 59  wherein the permanent substrate is paper.  
     
     
         73 . A printed proof comprising in order: 
 (a) a receiver support;    (b) an image receiving layer;    (c) a thermal halftone dot color image;    (d) a thermoplastic polymer layer; and    (e) a paper substrate; wherein the color image is encased between the image receiving layer and the thermoplastic polymer layer.    
     
     
         74 . The printed proof of  claim 73  wherein the receiver support is transparent.  
     
     
         75 . The printed proof of  claim 73  wherein the receiver support is removed.  
     
     
         76 . The printed proof of  claim 73  which comprises at least four thermal halftone dot color images of different colors encased between the image receiving layer and the thermoplastic polymer layer.  
     
     
         77 . A method for improving color purity in a thermal transfer color imaging process utilizing an NIR dye, comprising encasing the color image between a crystalline polymer layer and a thermoplastic polymer layer containing an NIR dye bleaching agent.  
     
     
         78 . The method of  claim 77  wherein the thermoplastic polymer layer further comprises a plasticizer.  
     
     
         79 . The method of  claim 78  wherein the plasticizer is present in the amount of about 1 to 20%, based on the total weight of the thermoplastic polymer layer.  
     
     
         80 . The method of  claim 77  wherein the NIR dye is selected from the group consisting of poly(substituted) phthalocyanine compounds; metal-containing phthalocyanine compounds; cyanine dyes; squarylium dyes; chalcogenopyryioacrylidene dyes; croconium dyes; metal thiolate dyes; bis(chalcogenopyrylo) polymethine dyes; oxyindolizine dyes; bis(aminoaryl) polymethine dyes; merocyanine dyes; and quinoid dyes.  
     
     
         81 . The method of claim  80  wherein the NIR dye bleaching agent is selected from the group consisting of hydrogen peroxide, organic peroxides, hexaaryl biimidazoles, halogenated organic compounds, persulfates, perborates, perphosphates, hypochlorites and azo compounds.