Multicolor thermal imaging method and thermal imaging member for use therein

Abstract

Described herein are methods, devices and reagents for direct thermal imaging and, more particularly, for multicolor direct thermal imaging, wherein a direct thermal imaging member comprising different image-forming compositions is imaged at different speeds by a source of heat to form a multicolored image.

1 . A multicolor thermal imaging method, comprising:
 (a) using heat to form an image in a first color at a first speed of travel with respect to the source of said heat of a thermal imaging member comprising at least a first image-forming layer forming the first color when heated and a second image-forming layer forming a second color when heated, said first and second colors being different from each other; and   (b) using heat to form an image in said second color at a second speed of travel of said thermal imaging member with respect to said source of said heat;   wherein said first speed of travel and said second speed of travel are substantially different speeds of travel; whereby a multicolor image is formed in said thermal imaging member.   
   
   
       2 . The thermal imaging method of  claim 1 , wherein said first speed of travel is greater than 0.5 inches/second and said second speed of travel is less than 0.5 inches/second. 
   
   
       3 . The thermal imaging method of  claim 1 , wherein said first speed of travel is greater than 0.7 inches/second and said second speed of travel is less than 0.3 inches/second. 
   
   
       4 . The thermal imaging method of  claim 1 , wherein said source of said heat comprises a thermal printing head. 
   
   
       5 . The thermal imaging method of  claim 4 , wherein the heat sink of said thermal printing head is maintained at an approximately constant temperature during steps (a) and (b). 
   
   
       6 . The thermal imaging method of  claim 5 , wherein said approximately constant temperature is at least about 5° C. above ambient temperature. 
   
   
       7 . The thermal imaging method of  claim 6 , wherein said approximately constant temperature is at least about 20° C. above ambient temperature. 
   
   
       8 . The thermal imaging method of  claim 4 , wherein the heat sink of said thermal printing head is maintained at a first temperature during step (a) and a second temperature during step (b), said first and said second temperatures differing by at least about 5° C. 
   
   
       9 . The thermal imaging method of  claim 1 , wherein said source of said heat comprises a laser. 
   
   
       10 . The thermal imaging method of  claim 1 , wherein said source of said heat comprises more than one heating means. 
   
   
       11 . The thermal imaging method of  claim 10 , wherein said source of said heat comprises a first heating means capable of being modulated so as to form an image in said thermal imaging member and a second heating means capable of providing uniform preheating. 
   
   
       12 . The thermal imaging method of  claim 1 , wherein said first heating means and said second heating means make contact with different points on the same surface of said thermal imaging member at any given instant. 
   
   
       13 . The thermal imaging method of  claim 12 , wherein said second heating means is maintained at an approximately constant temperature during steps (a) and (b). 
   
   
       14 . The thermal imaging method of  claim 13 , wherein said approximately constant temperature is at least about 5° C. above ambient temperature. 
   
   
       15 . The thermal imaging method of  claim 13 , wherein said approximately constant temperature is at least about 20° C. above ambient temperature. 
   
   
       16 . The thermal imaging method of  claim 12 , wherein said second heating means is maintained at a first temperature during step (a) and at a second temperature during step (b), said first and said second temperatures differing by at least about 5° C. 
   
   
       17 . The thermal imaging method of  claim 1 , wherein said first image-forming composition has an activating temperature that is higher by at least about 5° C. than that of said second image-forming composition. 
   
   
       18 . The thermal imaging method of  claim 17 , wherein said first speed of travel is greater than said second speed of travel. 
   
   
       19 . A multicolor thermal imaging method comprising:
 (a) using heat to form an image in a first color at a first speed of travel with respect to the source of said heat of a thermal imaging member comprising at least a first image-forming layer forming the first color when heated, a second image-forming layer forming a second color when heated, and a third image-forming composition forming a third color when heated, said first, second and third colors being different from each other;   (b) using heat to form an image in said second color at a second speed of travel of said thermal imaging member with respect to said source of said heat; and   (c) using heat to form an image in said third color at a third speed of travel of said thermal imaging member with respect to said source of said heat;   wherein at least two of said first, second and third speeds of travel are substantially different speeds of travel; whereby a multicolor image is formed in said thermal imaging member.   
   
   
       20 . The thermal imaging method of  claim 19 , wherein two of said first, second and third speeds of travel are the same. 
   
   
       21 . The thermal imaging method of  claim 20 , wherein an image is formed in at least two of said colors in one pass of said thermal imaging member relative to said source of said heat and an image is formed in at least a third of said colors in another pass of said thermal imaging member relative to said source of said heat. 
   
   
       22 . The thermal imaging method of  claim 19 , wherein each of said first, second and third speeds of travel are substantially different speeds of travel. 
   
   
       23 . The thermal imaging method of  claim 19 , wherein said source of said heat comprises a thermal printing head. 
   
   
       24 . The thermal imaging method of  claim 23 , wherein an image is formed in at least two of said image-forming layers in one printing pass of said thermal printing head and an image is formed in at least a third of said image-forming layers in another printing pass of said thermal printing head, wherein the speeds of travel of said thermal imaging member with respect to said thermal printing head in said printing passes are substantially different speeds of travel. 
   
   
       25 . The thermal imaging method of  claim 24 , wherein the heat sink of said thermal printing head is maintained at a first temperature during one printing pass and a second temperature during the other printing pass, wherein said first temperature differs from said second temperature by at least about 5° C. 
   
   
       26 . The thermal imaging method of  claim 24 , wherein the heat sink of said thermal printing head is maintained at a first temperature during one printing pass and a second temperature during the other printing pass, wherein said first temperature differs from said second temperature by less than about 5° C. 
   
   
       27 . The thermal imaging method of  claim 23 , wherein an image is formed in one of said image-forming layers in a first printing pass of said thermal printing head, an image is formed in another of said image-forming layers in a second printing pass of said thermal printing head, and an image is formed in a third of said image-forming layers in a third printing pass of said thermal printing head, wherein the speeds of travel of said thermal imaging member with respect to said thermal printing head in at least two of said first, second and third printing passes are substantially different speeds of travel. 
   
   
       28 . The thermal imaging method of  claim 27 , wherein the heat sink of said thermal printing head is maintained at a first temperature during the first of said passes, a second temperature during the second of said passes, and a third temperature during the third of said passes, at least one of said first, second, and third temperatures differing from at least another of said first, second and third temperatures by at least about 5° C. 
   
   
       29 . The thermal imaging method of  claim 27 , wherein the heat sink of said thermal printing head is maintained at a first temperature during the first of said passes, a second temperature during the second of said passes, and a third temperature during the third of said passes, wherein none of said first, second, and third temperatures differ from any other of said first, second and third temperatures by more than about 5° C. 
   
   
       30 . The thermal imaging method of  claim 19 , wherein said source of said heat comprises more than one heating means. 
   
   
       31 . The thermal imaging method of  claim 30 , wherein said source of said heat comprises a first heating means capable of being modulated so as to form an image in said thermal imaging member and a second heating means capable of providing uniform preheating. 
   
   
       32 . The thermal imaging method of  claim 31 , wherein said first heating means and said second heating means make contact with different points on the same surface of said thermal imaging member at any given instant. 
   
   
       33 . The thermal imaging method of  claim 31 , wherein an image is formed in at least two of said image-forming layers in one pass of said first and second heating means and an image is formed in at least a third of said image-forming layers in another pass of said first and second heating means, the speeds of travel of said thermal imaging member with respect to said first and second heating means in said passes being substantially different speeds of travel. 
   
   
       34 . The thermal imaging method of  claim 33 , wherein said second heating means is maintained at a first temperature during one pass and at a second temperature during the other pass, wherein said first temperature differs from said second temperature by at least about 5° C. 
   
   
       35 . The thermal imaging method of  claim 33 , wherein said second heating means is maintained at a first temperature during one pass and at a second temperature during the other pass, wherein said first temperature differs from said second temperature by less than about 5° C. 
   
   
       36 . The thermal imaging method of  claim 31 , wherein an image is formed in one of said image-forming layers in a first pass of said first and second heating means, an image is formed in another of said image-forming layers in a second pass of said first and second heating means, and an image is formed in a third of said image-forming layers in a third pass of said first and second heating means, wherein the speeds of travel of said thermal imaging member with respect to said first and second heating means in at least two of said first, second and third printing passes are substantially different speeds of travel. 
   
   
       37 . The thermal imaging method of  claim 36 , wherein said second heating means is maintained at a first temperature during the first of said passes, at a second temperature during the second of said passes, and at a third temperature during the third of said passes, wherein at least two of said first, second, and third temperatures differ from each other by at least about 5° C. 
   
   
       38 . The thermal imaging method of  claim 36 , wherein said second heating means is maintained at a first temperature during the first of said passes, at a second temperature during the second of said passes, and at a third temperature during the third of said passes, none said first, second, and third temperatures differing from any other of said first, second and third temperatures by more than about 5° C. 
   
   
       39 . The thermal imaging method of  claim 19 , wherein said first image-forming composition has an activating temperature that is higher than that of said second image-forming composition, and said second image-forming composition has an activating temperature that is higher than that of said third image-forming composition. 
   
   
       40 . The thermal imaging method of  claim 39 , wherein said first speed of travel is greater than said second speed of travel, and said second speed of travel is greater than said third speed of travel.