US-12619153-B2 - Thermal processor and method for using the same

US12619153B2US 12619153 B2US12619153 B2US 12619153B2US-12619153-B2

Abstract

A thermal development apparatus for forming a relief structure on a photosensitive printing element. The apparatus comprises conveying means upon which the photosensitive printing element is securable, (b) a heatable roller mounted in the enclosure, wherein the heatable roller is heated to and maintained at an operating temperature at which the uncured portions of photosensitive material begins to liquefy or soften; (c) an absorbent material covering at least a portion of the heatable roller that is capable of absorbing liquefied or softened uncured portions of photosensitive material from the photosensitive printing element when the photosensitive printing element comes into contact with the absorbent material on the portion of the heatable roller; and (d) an auxiliary heating zone arranged relative to the conveying means that is configured to heat the photosensitive printing element from a first temperature at a location at which the photosensitive printing element enters or re-enters the thermal development apparatus to the operating temperature of the heatable roller.

Inventors

Tyler Hatmaker

Assignees

MACDERMID GRAPHICS SOLUTIONS, LLC

Dates

Publication Date: 20260505
Application Date: 20240611

Claims (20)

1 . A thermal development apparatus for forming a relief structure on a photosensitive printing element, wherein the photosensitive printing element comprises a flexible substrate and at least one layer of photosensitive material comprising cured portions of photosensitive material and uncured portions of photosensitive material on the flexible substrate, the apparatus comprising: a) an enclosure; b) conveying means upon which the photosensitive printing element is securable, wherein the conveying means comprises a conveyor supported by at least a first roller and a second roller, wherein the first roller is arranged adjacent to a position at which the photosensitive printing element is brought into contact with a web of absorbent material and the second roller is positioned at a distance from the first roller; c) a heatable roller mounted in the enclosure, wherein the heatable roller is heated to and maintained at an operating temperature at which the uncured portions of photosensitive material begins to liquefy or soften; d) an absorbent material covering at least a portion of the heatable roller, wherein the absorbent material is capable of absorbing liquefied or softened uncured portions of photosensitive material from the photosensitive printing element when the photosensitive printing element comes into contact with the absorbent material on the portion of the heatable roller; e) an auxiliary heating zone arranged relative to the conveying means, wherein the auxiliary heating zone is configured to heat the photosensitive printing element from a first temperature at a location at which the photosensitive printing element enters or re-enters the thermal development apparatus to the operating temperature of the heatable roller; and f) an external heating means for applying heat to the photosensitive printing element on the conveying means.
2 . The thermal development apparatus according to claim 1 , wherein the auxiliary heating zone comprises one or more plate heaters and or blowers mounted relative to the conveying means.
3 . The apparatus according to claim 2 , wherein the one or more plate heaters are infrared heaters.
4 . The apparatus according to claim 2 , wherein the one or more plate heaters are positioned at a distance from a top surface of the photosensitive printing element.
5 . The apparatus according to claim 4 , wherein the distance from the top surface of the photosensitive printing element is adjustable, whereby the intensity of the one or more plate heaters is controlled.
6 . The apparatus according to claim 2 , wherein the one or more plate heaters are arranged in a rail system that permits vertical movement and/or horizontal movement, wherein the one or more plate heaters traverse across the width of the photosensitive printing element and/or to adjust the distance or location of the one or more plate heaters relative to the surface of the photosensitive printing element.
7 . The apparatus according to claim 3 , wherein the one or more plate heaters comprise at least two plate heaters, wherein the at least two plate heaters are used in series.
8 . The apparatus according to claim 7 , wherein the at least two plate heaters comprise infrared plate heaters that operate at different wavelength outputs.
9 . The apparatus according to claim 1 , comprising a control system coupled to the thermal development apparatus, wherein the control system comprises one or more temperature sensors.
10 . The apparatus according to claim 9 , wherein at least one of the one or more temperature sensors measure a temperature of the photosensitive printing element.
11 . The apparatus according to claim 1 , comprising a cooling system positioned below the continuous loop of the conveying means, wherein the cooling system controls a temperature of the flexible substrate.
12 . The apparatus according to claim 11 , wherein the cooling system comprises a thermoelectric cooler, wherein the thermoelectric cooler is connected to the control system.
13 . The apparatus according to claim 1 , further comprising blowers, wherein the blowers directed heated air towards a surface of the photosensitive printing element.
14 . The apparatus according to claim 1 , wherein said heating means are positioned adjacent to a point where the absorbent material contacts the photosensitive printing element on the conveying means.
15 . A method of thermally developing a photopolymer relief image printing element, wherein the photosensitive printing element comprises a flexible substrate and at least one layer of photosensitive material comprising cured portions of photosensitive material and uncured portions of photosensitive material on the flexible substrate, the method comprising the steps of: a. securing a photosensitive printing element to a conveying means, wherein the conveying means comprises a conveyor supported by at least a first roller and a second roller, wherein the first roller is adjacent to a position at which the photosensitive printing element is brought into contact with a web of absorbent material and the second roller is positioned at a distance from the first roller; b. heating the photosensitive printing element from a first temperature to an operating temperature of a heatable roller in an auxiliary heating zone, where the auxiliary heating zone is configured to heat the photosensitive printing element from a first temperature to the operating temperature of the heatable roller, and wherein the operating temperature of the heatable roller is a temperature sufficient to cause at least a portion of the photosensitive printing element to soften or liquefy when an absorbent material is brought into contact with the at least one layer of photosensitive material; c. applying heat to the photosensitive printing element on the conveyor from an external heater positioned adjacent to a point where the absorbent material contacts the photosensitive printing element on the conveyor; d. supplying an absorbent material to at least a portion of an outer surface of the heatable roller, said heatable roller being mounted for rotation in the frame, wherein the absorbent material is capable of absorbing material that is liquefied or softened from the photosensitive printing element when the heatable roller is heated and the absorbent material contacts at least a portion of the photosensitive printing element; and e. causing the photosensitive material and the absorbent printing element to come into contact at a point between the conveyor and the heatable roller such that at least a portion of the liquefied or softened material is absorbed by the absorbent material.
16 . The method according to claim 15 , wherein the first temperature is less than about 50° C. and the operating temperature is greater than about 100° C.
17 . The method according to claim 15 , wherein the auxiliary heating zone comprises one or more plate heaters and/or one or more blowers.
18 . The method according to claim 17 , wherein the one or more plate heaters and/or blowers are arranged in a rail system that permits vertical movement and/or horizontal movement, the method further comprising the step of traversing the one or more plate heaters and/or blowers across the width of the relief image printing element and/or adjusting a distance or a location of the one or more plate heaters and/or blowers relative to the surface of the photosensitive printing element.
19 . The method according to claim 15 , further comprising a step of controlling a temperature of the flexible substrate, wherein a cooling system is positioned below the continuous loop of the conveying means to cool the backside of the photosensitive printing element.
20 . The method according to claim 19 , wherein the cooling system comprises a thermoelectric cooler, wherein the thermoelectric cooler is connected to the control system.

Description

FIELD OF THE INVENTION The present invention is directed to a thermal development apparatus and a method of using the same to thermally develop photosensitive relief image printing elements. BACKGROUND OF THE INVENTION Flexography is a method of printing that is commonly used for high-volume runs and is employed for printing on a variety of substrates such as paper, paperboard stock, corrugated board, films, foils and laminates. Newspapers and grocery bags are prominent examples. Coarse surfaces and stretch films can be economically printed only by means of flexography. Flexographic printing plates are relief plates with image elements raised above open areas. Such plates offer a number of advantages to the printer, based chiefly on their durability and the case with which they can be made. Although photopolymer printing elements are typically used in “flat” sheet form, there are applications that utilize the printing element in a continuous cylindrical form, as a continuous in-the-round (CITR) photopolymer sleeve. A typical flexographic printing blank as delivered by its manufacturer is a multilayered article made of, in order, a backing or support layer, one or more unexposed photosensitive or photocurable layers, a protective layer, slip film and/or laser ablatable layer, and a cover sheet. The flexographic relief image printing element is generally produced from a photosensitive printing blank by imaging the photosensitive printing blank to produce a relief image on the surface of the photosensitive printing element. This can be accomplished by selectively exposing the photosensitive material to actinic radiation, which exposure acts to harden or crosslink the photosensitive material in the irradiated areas. The photosensitive printing blank contains one or more layers of uncured photosensitive material on a suitable backing layer. The photosensitive printing blank can be in the form of a flat, planar plate that is mounted on a carrier sleeve or a continuous (seamless) sleeve. The photosensitive relief image printing element may be selectively exposed to actinic radiation in one of three related ways. In a first alternative, a photographic negative with transparent areas and substantially opaque areas is used to selectively block the transmission of actinic radiation to the printing element. In a second alternative, the photopolymer layer is coated with an actinic radiation (substantially) opaque layer that is sensitive to laser ablation. A laser is then used to ablate selected areas of the actinic radiation opaque layer creating an in situ negative. This technique is well-known in the art, and is described for example in U.S. Pat. Nos. 5,262,275 and 6,238,837 to Fan, and in U.S. Pat. No. 5,925,500 to Yang et al., the subject matter of each of which is herein incorporated by reference in its entirety. In a third alternative, a focused beam of actinic radiation is used to selectively expose the photopolymer. Any of these methods is acceptable, with the criteria being the ability to selectively expose one or more layers of photosensitive material to actinic radiation thereby selectively curing portions of the one or more layers of photosensitive material. Thereafter, the one more layers of photosensitive material are developed to remove uncured (i.e., non-crosslinked) portions of the one or more layers, without disturbing the cured portions of the one or more layers of photocurable or photosensitive material, to produce the relief image. The development step can be accomplished in a variety of ways, including water washing, solvent washing, and thermal development. Upon completion of the development step, the relief image printing element may be subjected to one or additional steps, including, for example, post-exposure to further actinic radiation and/or detackification, and is then cooled and is ready to use. BACKGROUND OF THE INVENTION It is an object of the present invention to improve quality of photosensitive printing elements processed using thermal development. It is another object of the present invention to reducing machine processing issues in a thermal development apparatus that can adversely affect the quality of the photosensitive relief image printing elements processed therein. It is still another object of the present invention to improve temperature control during thermal development. It is another object of the present invention to reduce temperature variations of the photosensitive printing element during thermal development. It is still another object of the present invention to control the temperature of the photosensitive printing element at entry or reentry of the photosensitive printing element into the thermal development apparatus. It is another object of the present invention to provide a means of gradually heating the photosensitive printing element so that the temperature of the photosensitive printing element approaches the processing temperature of the thermal development a