METHOD FOR THERMALLY DEVELOPING RELIEF PRECURSORS

Abstract

A method for thermally developing a relief precursor comprising a supporting layer and photopolymer layer having cured and uncured portions comprising the steps: (a) fixing the relief precursor with the supporting layer adjacent to a movable support; (b) repeatedly moving the support with the relief precursor fixed thereon in a multitude of movement cycles; (c) heating the relief precursor to a temperature sufficient to cause the uncured portions of the photopolymer layer to soften or liquefy; (d) contacting the relief precursor with a development medium to allow the liquefied material of the uncured portions to be adhered to and removed by the development medium;
wherein the heating and contacting is carried out in cycles A, B, C or D each corresponding to a single movement cycle such that (i) in a cycle A, the relief precursor is heated with higher heating power and not contacted the relief precursor with the development medium; (ii) in a cycle B, the relief precursor is heated with higher heating power and contacted with the development medium; (iii) in a cycle C, the relief precursor is not heated or heated with lower heating power and contacted with the development medium; (iv) in a cycle D, the relief precursor is not heated or heated with lower heating power and not contacted with the development medium;
wherein cycle B is carried out once or more and at least one of cycles A, C or D is carried out once or more.

Claims

1.-15. (canceled)

16. A method for thermally developing a relief precursor comprising a supporting layer and photopolymer layer having cured and uncured portions comprising the steps: (a) fixing the relief precursor with the supporting layer adjacent to a movable support; (b) repeatedly moving the support with the relief precursor fixed thereon in a multitude of movement cycles; (c) heating the relief precursor to a temperature sufficient to cause the uncured portions of the photopolymer layer to soften or liquefy; (d) contacting the relief precursor with a development medium to allow the liquefied material of the uncured portions to be adhered to and removed by the development medium; wherein the heating and contacting is carried out in cycles A, B, C or D each corresponding to a single movement cycle such that (i) in a cycle A, the relief precursor is heated with higher heating power and not contacted the relief precursor with the development medium; (ii) in a cycle B, the relief precursor is heated with higher heating power and contacted with the development medium; (iii) in a cycle C, the relief precursor is not heated or heated with lower heating power and contacted with the development medium; (iv) in a cycle D, the relief precursor is not heated or heated with lower heating power and not contacted with the development medium; wherein cycle B is carried out once or more and at least one of cycles A, C or D is carried out once or more.

17. The method of claim 16, wherein a sequence of at least two cycles B is carried out.

18. The method of claim 16, wherein at least one cycle A is carried out before the first cycle B is carried out.

19. The method of claim 16, wherein at least one cycle A is carried out after the last cycle B has been carried out.

20. The method of claim 16, wherein at least one cycle C is carried out after at least one cycle B has been carried out.

21. The method of claim 16, wherein at least one cycle D is carried out after at least one cycle B has been carried out.

22. The method of claim 16, wherein a sequence of alternating cycles B and D is carried out.

23. The method of claim 21, wherein a sequence of at least two cycles B is carried out, followed by a sequence of alternating cycles B and D.

24. The method of claim 16, wherein 2 to 50 cycles are carried out.

25. The method of claim 16, wherein the movable support is a rotating drum.

26. The method of claim 16, wherein the heating is carried out by means of infrared heating.

27. The method of claim 16, wherein in cycles B or C the development medium contacting the relief precursor is pressed against the surface of the relief precursor by means of a heated roll.

28. The method of claim 27, wherein in cycles A or B the relief precursor is heated to a temperature from 50 to 300 C.

29. The method of claim 16, wherein the movable support is moving with a speed of 0.2 to 10 m/min.

30. The method of claim 16, wherein the development medium is selected from the group consisting of non-woven fibrous materials, fibrous woven materials, a porous material, a foam and combinations thereof.

Description

EXAMPLES

Example 1

[0051] Plate precursors with a SIS based photopolymer layer on a polyester substrate, an integrated mask layer and a thickness of 114 mm was used for the following procedures. First a mask comprising different structures was created by ablation using a Thermoflexx 80 apparatus (Xeikon) under the following conditions: The mask comprised lines with a width of about 90 m and different orientation. 6 lines with a length of 305 mm perpendicular and 6 lines with a length of 485 mm parallel to the short side of the precursor. The length of the lines created during mask formation La was measured using a glass ruler (Electronic Scale ESM-25/1000). Then the precursors were exposed for 8 minutes using a nyloflex NExT FV Exposure apparatus with 19 mW/cm2. These precursors were then processed in an nyloflex Xpress Thermal Processor FIV (Flint Group) comprising an unwinding and winding mechanism for the developing material, a rotating rum whereon the precursor is attached, a heated roll with a maximum power of 3300 W and an IR heater delivering 3825 W at 100% power (80% relate to 3060 W and 40% relates to 1530 W). These precursors were processed at a precursor speed of 1,778 cm/sec (0.7 inch/second) for all cycles, temperature of heated roll at 162.8 C. (325 F.), with a pressure of 413.7 kPa (60 PSI), the IR power at 40% in case of cycle B. For cycle C the heated roll was heated to 162.8 C. with a pressure of 413.7 kPa (60 PSI) and the IR heater was switched off. For cycle D the heated roll did not touch the plate precursor and the IR heater was switched off. The sequences according table 1 were used. Afterwards the length of the lines created on the clich Lc were measured using a glass ruler and compared to the length of the lines created during mask formation (after ablation) La. For each line the difference ac=LaLc was calculated. In the following the standard deviation SD for ac was calculated and is used as a measure for the accuracy and registration quality. The smaller SD the better the accuracy and the registration quality.

TABLE-US-00001 TABLE 1 SD normalized Registration Example Cycle sequence to 1a on print 1a 10 B 1 poor (reference) 1b 10 BD alternating 0.58 Very good 1c 3 BD alternating followed by 0.94 poor 7 B 1d 7 B followed by 3 BD 0.87 Acceptable alternating 1e 7 B followed by 3 C Not Acceptable determined 1f 7 B followed by 2 C Not Acceptable and 1 D determined

[0052] The results from table 1 show that using cycles D and/or C improves the registration quality which might be due to relaxation of the photopolymer layer during the additional cycles and/or due to less thermal stress.

Example 2

[0053] Plate precursors with a SBS based photopolymer layer on a polyester substrate, an integrated mask layer based on polyamide and a thickness of 114 mm was used for the following procedures. First a mask comprising different structures was created by ablation using a Thermoflexx 80 apparatus (Xeikon) under the following conditions: The mask comprised different areas, one of which represents a solid area of 70 mm by 25 mm. Then the precursors were exposed for 10 minutes using a nyloflex NExT FV (Flint Group) Exposure apparatus with 19 mW/cm2. After Exposure the precursors were processed in an nyloflex Xpress Thermal Processor FIV (Flint Group) according to the settings in table 2. An Erichsen mini glossmaster 60 (Modell 507 M) was used to determine the gloss of the solid area created. The measurement was repeated 10 times and the average was calculated. The higher the gloss value, the smoother the surface.

TABLE-US-00002 TABLE 2 Tempera- ture IR Pres- Precursor Gloss 60 heated roll power sure speed normal- Example Cycles ( C.) (%) (kPa) (cm/sec) ized to 2a 2a 10 B 162.8 40 413.7 1.778 1 reference 2b 10 B 162.8 40 413.7 1.778 1.01 1 A 40 0 1.778 2c 10 B 162.8 40 413.7 1.778 1.04 3 A 40 0 1.778 2d 10 B 162.8 40 413.7 1.778 1.16 1 A 80 0 1.778 2e 10 B 162.8 40 413.7 1.778 1.27 3 A 80 0 1.778 2f 9 B 162.8 40 413.7 1.778 1.18 1 A 80 0 1.778

[0054] From table 2 it is obvious that using cycles A and B can be used to generate smoother surfaces by reducing the marks formed by the web structure.

Example 3

[0055] Plate precursors with a SIS based photopolymer layer on a polyester substrate, an integrated mask layer based on polyvinyl acetate and a thickness of 114 mm was used for the following procedures. The precursors were processed in a nyloflex Xpress Thermal Processor FIV (Flint Group) according to the settings in table 3. When a lot of mask material remained after the cycles the result was rated . When some mask material remained after the cycles the result was rated 0. When almost all mask material was removed the result was rated +. When all mask material was removed the result was rated ++.

TABLE-US-00003 TABLE 3 Tempera- ture IR Pres- Precursor removal heated roll power sure speed of mask Example Cycles ( C.) (%) (kPa) (cm/sec) layer 3a 1 B 162.8 40 413.7 1.778 reference 3b 2 B 162.8 40 413.7 1.778 reference 3c 2 A 20 0 1.778 + 1 B 162.8 40 413.7 1.778 3d 1 A 20 0 1.778 0 1 B 162.8 40 413.7 1.778 3e 1 A 40 0 1.778 + 1 B 162.8 40 413.7 1.778 3f 1 A 70 0 1.778 ++ 1 B 162.8 40 413.7 1.778

[0056] From table 3 it is obvious that using cycles A improves the removal of the integrated mask layer significantly and with increasing IR power the results are improving.