UV-absorbing support layers and flexographic printing elements comprising same

Abstract

The present invention provides a method for producing direct-imaged flexographic printing elements such that both the front and back exposure times are economically efficient for the manufacturer. In one embodiment, the method comprises providing at least one solid photocurable element. The solid photocurable element comprises a solid photocurable material comprising an oxygen scavenger, a support layer having an actinic radiation absorbing compound integrated uniformly throughout such that it absorbs at least some actinic radiation during exposure, and a photoablative mask layer. The methods of the invention involve creating a floor in the solid photocurable material by back exposure through the support layer having the actinic radiation absorbing compound, transferring a negative image directly onto the solid photocurable material by photoablating the photoablatable mask layer, followed by front exposure effective to cure the solid photocurable material.

1. A method comprising:
 a) providing at least one solid photocurable printing element comprising: 
 a support layer having an actinic radiation absorbing compound uniformly distributed throughout said support layer;  
 a layer of solid photocurable material that has first and second opposing major faces, said first opposing major face disposed upon said support layer, wherein said layer of solid photocurable material comprises an oxygen scavenger; and  
 a photoablative mask layer that is disposed on said second opposing major face, that is substantially opaque to actinic radiation, and is capable of being photoablated by a laser;  
 
 b) transferring graphic data to said solid photocurable printing element by photoablating said photoablative mask layer with a laser, thereby providing ablated and unablated areas forming an image, said ablated areas exposing said second opposing major face of said solid photocurable layer;  
 c) exposing said first opposing major face of said photocurable layer through said support layer;  
 d) exposing said ablated areas of said solid photocurable material to actinic radiation effective to cure said solid photocurable material; and  
 e) removing uncured photocurable material and said unablated areas of said photoablative mask layer from said element.  
 
     
     
       2. A method according to  claim 1  wherein said support layer is polyethylene terephthalate. 
     
     
       3. A method according to  claim 1  wherein said support layer having an actinic radiation absorbing compound uniformly distributed throughout said support layer absorbs between about 85 and about 95 percent actinic radiation. 
     
     
       4. A method according to  claim 1  wherein said oxygen scavenger comprises a phosphine compound. 
     
     
       5. A method according to  claim 4  wherein said phosphine compound is selected from the group consisting of triphenylphosphine, triphenyl phosphite, tri-p-tolylphosphine, diphenylmethylphosphine, diphenylethylphosphine, diphenylpropylphosphine, dimethylphenylphosphine, diethylphenylphosphine, dipropylphenylphosphine, divinylphenylphosphine, divinyl-p-methoxyphenylphosphine, divinyl-p-bromophenylphosphine, divinyl-p-tolylphosphine, diallylphenylphosphine, diallyl-p-methoxyphenylphosphine, diallyl-p-bromophenylphosphine and diallyl-p-tolylphosphine. 
     
     
       6. A method according to  claim 4  wherein said phosphine compound is present at a concentration of from about 0.075 to about 0.75 weight percent of said solid photocurable material. 
     
     
       7. A method according to  claim 1  wherein said solid photocurable material comprises a plurality of layers. 
     
     
       8. A method according to  claim 1  wherein said solid photocurable element further comprises a cap layer upon which said photoablative mask layer is disposed. 
     
     
       9. A method according to  claim 8  wherein said cap layer comprises an actinic radiation absorbing dye. 
     
     
       10. A method comprising:
 a) providing at least one solid photocurable printing element comprising: 
 an inherently UV-absorbing support layer;  
 a layer of solid photocurable material that has first and second opposing major faces, said first opposing major face disposed upon said support layer, wherein said layer of solid photocurable material comprises an oxygen scavenger; and  
 a photoablative mask layer that is disposed on said second opposing major face, that is substantially opaque to actinic radiation, and is capable of being photoablated by a laser;  
 
 b) transferring graphic data to said solid photocurable printing element by photoablating said photoablative mask layer with a laser, thereby providing abalted and unablated areas forming an image, said ablated areas exposing said second opposing major face of said solid photocurable layer;  
 c) exposing said first opposing major face of said photocurable layer through said support layer;  
 d) exposing said ablated areas of said solid photocurable material to actinic radiation effective to cure said solid photocurable material; and  
 e) removing uncured photocurable material and said unablated areas of said photoablative mask layer from said element.  
 
     
     
       11. A method according to  claim 10  wherein the support layer is polyethylene naphthalate. 
     
     
       12. A printing element according to  claim 11  wherein the polyethylene naphthalate support layer is from about 3 to 5 mils thick. 
     
     
       13. A method for producing a flexographic printing plate, said method comprising:
   a )  providing at least one solid photocurable printing element comprising:    ( i )  a support layer having an actinic radiation absorbing compound uniformly distributed throughout said support layer;      ( ii )  a layer of solid photocurable material disposed on said support layer;      ( iii )  an ablation layer that is disposed on said layer of solid photocurable material, wherein said ablation layer is substantially opaque to actinic radiation and is capable of being ablated by a laser;         b )  transferring graphic data to said solid photocurable printing element by selectively ablating portions of said ablation layer with a laser to create an image;        c )  back exposing said solid photocurable printing element to actinic radiation through said support layer;        d )  exposing said solid photocurable printing element to actinic radiation through the portions of the ablation layer that have been ablated to cure the solid photocurable printing element; and        e )  removing uncured photocurable material and any remaining ablation layer from said solid photocurable printing element.     
     
     
       14. A method according to  claim 13  wherein said support layer comprises a material selected from the group consisting of polyethylene terephthalate, polyethylene naphthalate, polyether, polyethylene, polyamide and nylon. 
     
     
       15. A method according to  claim 13  wherein said support layer comprises polyethylene terephthalate. 
     
     
       16. A method according to any one of claims  13 ,  14 , or  15  wherein said support layer absorbs between about  80 %  and  99   %  of the actinic radiation used in said back exposing.   
     
     
       17. A method according to any one of claims  13 ,  14 , or  15  wherein said support layer absorbs between about  85 %  and  95   %  of the actinic radiation used in said back exposing.   
     
     
       18. A method according to any one of claims  13 ,  14 , or  15  wherein the actinic radiation has a wavelength in the range from  300  nm to  400  nm and said support layer absorbs between about  80 %  and  99   %  of the actinic radiation used in said back exposing.   
     
     
       19. A method for producing a flexographic printing plate, said method comprising:
   a )  providing at least one solid photocurable printing element comprising:    ( i )  an inherently UV - absorbing support layer;      ( ii )  a layer of solid photocurable material disposed on said support layer;      ( iii )  an ablation layer that is disposed on said layer of solid photocurable material, wherein said ablation layer is substantially opaque to actinic radiation and is capable of being ablated by a laser;          b )  transferring graphic data to said solid photocurable printing element by selectively ablating portions of said ablation layer with a laser to create an image;        c )  back exposing said solid photocurable printing element to actinic radiation through said support layer;        d )  exposing said solid photocurable printing element to actinic radiation through the portions of the ablation layer that have been ablated; and        e )  removing uncured photocurable material and any remaining ablation layer from said solid photocurable printing element.     
     
     
       20. A method according to  claim 19  wherein the inherently UV- absorbing support layer comprises polyethylene naphthalate.   
     
     
       21. A method according to  claim 20  wherein the support layer is from about  3  to  5  mils thick. 
     
     
       22. A method according to any one of claims  19 ,  20 , or  21  wherein said support layer absorbs between about  80 %  and  99   %  of the actinic radiation used in said back exposing.   
     
     
       23. A method according to any one of claims  19 ,  20 , or  21  wherein said support layer absorbs between about  85 %  and  95   %  of the actinic radiation used in said back exposing.   
     
     
       24. A flexographic printing plate element comprising:
   a )  a support layer which is capable of absorbing between about  80   %  and  99   %  of the actinic radiation used to back expose said printing plate element;        b )  at least one layer of solid photocurable material disposed on said support layer; and        c )  an ablation layer capable of being ablated by laser radiation and which is substantially opaque to actinic radiation.     
     
     
       25. A flexographic printing plate element according to  claim 24  wherein said support layer comprises polyethylene terephthalate. 
     
     
       26. A flexographic printing plate element according to  claim 24  wherein said support layer comprises a material selected from the group consisting of polyethylene terephthalate, polyethylene naphthalate, polyether, polyethylene, polyamide and nylon, and wherein said material has an actinic radiation absorbing compound uniformly distributed throughout. 
     
     
       27. A flexographic printing plate element according to any one of claims  24 ,  25 , or  26  wherein the support layer is from about  3  to  5  mils thick. 
     
     
       28. A flexographic printing plate element according to any of claims  24 ,  25 , or  26  wherein said solid photocurable material comprises an oxygen scavenger. 
     
     
       29. A flexographic printing plate element according to  claim 28  wherein the oxygen scavenger is a compound selected from the group consisting of triphenylphosphine, triphenyl phosphite, tri- p - tolylphosphine, diphenylmethylphosphine, diphenylethylphosphine, diphenylpropylphosphine, dimethylphenylphosphine, diethylphenylphosphine, dipropylphenylphosphine, divinylphenylphosphine, divinyl - p - methoxyphenylphosphine, divinyl - p - bromophenylphosphine, divinyl - p - tolylphosphine, diallylphenylphosphine, diallyl - p - methoxyphenylphosphine, diallyl - p - bromophenylphosphine and diallyl - p - tolylphsphine.   
     
     
       30. A flexographic printing plate element comprising:
   a. a support layer comprising an actinic radiation absorbing compound uniformly distributed throughout said support layer;        b. at least one layer of solid photocurable material disposed on said support layer; and        c. an ablation layer capable of being ablated by laser radiation and which is substantially opaque to actinic radiation.     
     
     
       31. A flexographic printing plate element according to  claim 30  wherein the support layer comprises polyethylene terephthalate.