Method and apparatus for thermal processing a photosensitive element

A method for forming a relief pattern from a photosensitive element comprising a flexible substrate having an exterior surface and an interior surface, and a composition layer on the substrate capable of being partially liquefied, the composition layer having an exterior surface and an interior surface, with the composition layer and flexible substrate joined at their respective interior surfaces, comprising:

• supporting the element with the exterior surface of the flexible substrate in contact with an outer circumferential surface of a drum mounted for rotation in a second frame portion;
• contacting an absorbent material to the exterior surface of the composition layer by passing the material over an exterior surface of a roller mounted for rotation in a first frame portion, wherein at least one of the first and second frame portions are moveable relative to the other;
• heating the exterior surface of the composition layer to a temperature T1 which is equal to or greater than a temperature T2 sufficient to cause a portion of the layer to liquefy, while maintaining the exterior surface of the flexible substrate at a temperature T3 at least 20° F. below temperature T1;
• heating the absorbent material to a temperature capable of heating the exterior surface of the composition layer to a temperature T4 which is equal to or greater than temperature T2;
• pressing the absorbent material against the composition layer by urging the first frame portion supporting the roller and the second frame portion supporting the drum toward each other at a pressure sufficient for the heated absorbent material to liquefy at least a portion of the exterior surface of the layer and to absorb the liquefied material;
• maintaining the exterior surface of the flexible substrate at a temperature T3 at least 20° F. below temperature T4 during said pressing and heating of the absorbent layer;
• and
• separating the photosensitive element from the absorbent material, thereby removing the absorbed liquefied material from the photosensitive element.

A method for forming a relief pattern from a photosensitive element comprising a flexible substrate having an exterior surface and an interior surface, and a composition layer on the substrate capable of being partially liquefied, the composition layer having an exterior surface and an interior surface, with the composition layer and flexible substrate joined at their respective interior surfaces, comprising:

• supplying an absorbent material to the exterior surface of the composition layer with a roller operating at a temperature Tr that heats the absorbent material;
• delivering the photosensitive element to the absorbent material with a rotating drum and supporting the element with the exterior surface of the flexible substrate in contact with an outer circumferential surface of the drum, wherein each rotation of the drum defines a cycle;
• heating the exterior surface of the composition layer sufficient to cause a portion of the layer to liquefy with a heater operating at a temperature Th;
• pressing the photosensitive element and the heated absorbent material into contact between the drum operating at a rotation speed, S, and the roller at a pressure, P, sufficient for the heated absorbent material to liquefy at least a portion of the exterior surface of the composition layer and to absorb the liquefied material;
• separating the photosensitive element from the absorbent material;
• repeating the supplying, delivering, heating, pressing and separating steps for a predetermined number of cycles;
• and
• changing at least one of the process parameters selected from the group consisting of temperature of the roller Tr, temperature of the heater Th, pressure P, and rotation speed S, during at least one of the supplying, delivering, heating, and pressing steps for at least one of the predetermined number of cycles.

A method of forming a flexographic printing plate from a photosensitive element comprising a flexible substrate having an exterior surface and an interior surface, at least one composition layer capable of being partially liquified and comprising a photosensitive layer and an infrared-sensitive layer, the photosensitive layer having an interior surface opposite the infrared-sensitive layer, with the photosensitive layer and the flexible substrate joined at their respective interior surfaces, the method comprising:

• (a) exposing the infrared-sensitive layer imagewise with infrared laser radiation to form in-situ a mask having actinic radiation opaque areas on the photosensitive layer, the mask and the photosensitive layer not covered by the mask forming the exterior surface of the composition layer;
• (b) exposing the photosensitive element of (a) with actinic radiation through the mask;
• (c) treating the element of (b) with heat to form the relief pattern in the element, wherein the treating step is selected from a method I or II, wherein
• method I comprises:
• supporting the element with the exterior surface of the flexible substrate in contact with an outer circumferential surface of a drum mounted for rotation in a second frame portion;
• contacting an absorbent material to the exterior surface of the composition layer by passing the material over an exterior surface of a roller mounted for rotation in a first frame portion, wherein at least one of the first and second frame portions are moveable relative to the other;
• heating the exterior surface of the composition layer to a temperature T1 which is equal to or greater than a temperature T2 sufficient to cause a portion of the layer to liquefy, while maintaining the exterior surface of the flexible substrate at a temperature T3 at least 20° F. below temperature T1;
• heating the absorbent material to a temperature capable of heating the exterior surface of the composition layer to a temperature T4 which is equal to or greater than temperature T2;
• pressing the absorbent material against the composition layer by urging the first frame portion supporting the roller and the second frame portion supporting the drum toward each other at a pressure sufficient for the heated absorbent material to liquefy at least a portion of the exterior surface of the layer and to absorb the liquefied material;
• maintaining the exterior surface of the flexible substrate at a temperature T3 at least 20° F. below temperature T4 during said pressing and heating of the absorbent layer;
• and
• separating the photosensitive element from the absorbent material, thereby removing the absorbed liquefied material from the photosensitive element;
• and, method II comprises:
• supplying an absorbent material to the exterior surface of the composition layer with a roller operating at a temperature Tr that heats the absorbent material;
• delivering the photosensitive element to the absorbent material with a rotating drum, operating at a rotation speed, S, and supporting the element with the exterior surface of the flexible substrate in contact with an outer circumferential surface of the drum, wherein each rotation of the drum defines a cycle;
• heating the exterior surface of the composition layer sufficient to cause a portion of the layer to liquefy with a heater operating at a temperature Th;
• pressing the photosensitive element and the heated absorbent material into contact between the drum and the roller at a pressure, P, sufficient for the heated absorbent material to liquefy at least a portion of the exterior surface of the composition layer and to absorb the liquefied material;
• separating the photosensitive element from the absorbent material;
• repeating the supplying, delivering, heating, pressing and separating steps for a predetermined number of cycles;
• and
• changing at least one of the process parameters selected from the group consisting of temperature of the roller Tr, temperature of the heater Th, pressure P, and rotation speed S, during at least one of the supplying, delivering, heating, and pressing steps for at least one of the predetermined number of cycles.