Photopolymer plates

Fig. 10. Photopolymer plate stmcture and process of use A, upon exposure to laser light, V B, upon heating to 120°C and C, after development, rinsing,...

Newer technology involves aqueous-processible photopolymer plates. Many plate-makers and printers are eager to switch to water processing in order to eliminate volatile organic solvents. The chemistry and process of use are similar to that of the solvent-processible plate except that in the aqueous plate, the elastomer has pendent carboxyl, hydroxyl, or other water-soluble groups to allow aqueous processing. 

Manufacture of Photopolymer Plate used as Master Plate for Duplicate Plate... 

Figure 4. Structure of photopolymer printing plate for duplicate plate. ( ) The plate of the present development (hereafter referred to as the Photopolymer Plate).

As shown in Fig. 5, chemical lamp or ultra high pressure mercury lamp is considered to be a suitable light source for the Photopolymer Plate. 

After the protective cover sheet is peeled off from the Photopolymer Plate, a negative film is placed on the plate in a complete contact with the plate under vacuum. The negative film used here, should have a density of below 0.08 in the light transmitting area and over 2.6-3.0 in the non-light-transmitting area. 

The Photopolymer Plate can be washed out with water alone. In the actual operation, the Photopolymer Plate is processed on an Automatic Processor as shown in Fig. 6 7. 

On Profile of the Photopolymer Plate for making Paper Mold and Matrix... 

The shoulder angle of the plate obtained from the Photopolymer Plate has been so designed in the original formula that it will be around 23° (e) from the time of exposure. Furthermore, the shoulders are flat and smooth. (See Fig. 10)... 

Figure 13. Comparison of reliefs between the Photopolymer Plate and Zn pow-derless-etched plate (A) the Photopolymer Plate (100 pm line) (B) Zn powderless-etched plate (100 pm line) (C) plate made from the Photopolymer Plate (picture taken from 43° angle, magnification 30 X, showing dot 25% ir 65 lines) (D) Zn plate obtained by powderless etching (picture taken from 45° angle, magnification 30 X)...

On Reproduceability from the Photopolymer Plate to Paper-Mold The images in a negative film can be reproduced with good fidelity. Presently used zinc plates, because of their suspected low color loss, show a less fidelity compared with photopolymer plates, but their reproduceability are very similar as shown in Table 2. 

Density Dot dia. in nega. film Zinc Plate The Photopolymer plate ... 

The comparison of reproduceability of diameters of dots in the highlight areas between the Photopolymer Plate and zinc plate from a negative film, showed 90-95% for the Photopolymer Plate and about 75% for a zinc plate because the latter showed color loss. (See Fig. 15)... 

Comparison of Reproduceability of Halftones between the Photopolymer Plate and Powderless Etched Zinc or Magnesium Plate As shown in Fig. 16, the Photopolymer Plate will reproduce the halftone almost completely from the negative film. This is in comparison with photopolymer plates, zinc plates or magnesium plates which give much less reproduceability. 

Comparison of Reproduceability of Isolated Image Lines between the Photopolymer Plate and Powderless Etched Zinc or Magnesium Plate. 

The Photopolymer Plate produces images by simple dissolution of unexposed areas of the photopolymer resin. However, in case of... 

Figure 15. Comparison of dot diameters in the highlight areas of the Zn plate and the Photopolymer Plate (O) dot diameter of negative (A) dot diameter of the Photopolymer Plate (9) dot diameter of Zn plate (%) halftone % of dot...

Figure 16. Comparison of reproduceability of halftones between the metal plate and the Photopolymer Plate (9) the Photopolymer Plate (A) Zn plate (powder-less-etched) (O) Mg plate (powderless-etched)...

On Reproduceability of Paper Mold made from the Photopolymer Plate to Stereo of Lead... 

As is clear from Table 2, zinc plates gave relatively deep images compared with those of the Photopolymer Plate. However, there is not much difference in the depth between those stereos obtained from zinc plates and the Photopolymer Plate, as shown in Table 3. This means that in reproduction work from a paper mold into a stereo, even if an effort is made to give more depth beyond necessity, it is not actually reproduced in the stereo. The Photopolymer Plate can show a satisfactory reproduceability if it has 30-40 urn depth in the shadow area. Further evaluations were made on isolated lines (in case of 60-150 jim line width) and depth in reverse area for their reproduceability onto paper surface, and the results were more stable than those with metal plates. Stereos can be also made with polypropylene as well as with lead. 

The Photopolymer Plate of over 85° Shore D hardness can stand temperatures over 160°C, and it could be successfully used as a master plate for making thermoformed matrix of phenol group resin to be used for thermoformed polymer printing plates such as rubber plates and the like under conditions of 30 kg/cm2 pressure... 

Table 3- Comparison of Reproduceability of Dot Diameters in Stereos made from Zinc Plate and the Photopolymer Plate...

No toxic substance is contained in the waste water of the Photopolymer Plate washout solution, and it is safe. 

Influence of the Photopolymer Plate to the health Acute toxic tests with mouses show that the exposed Photopolymer Plate has no toxidity at all and even the unexposed Photopolymer Plate has only a very weak toxidity therefore, there are no bad influences to the health and the Photopolymer Plate can be handled safely. 

The Photopolymer Plate, a water developable photopolymer relief printing master plate made by modification of polyvinyl alcohol with urea group oligomer having a functional polyvinyl base, for making paper mold and matrix for printing master plates, has characteristics which are very close to those of the conventionally etched metal relief printing plates and has some superior points to them. 

Furthermore, the Photopolymer Plate does not require handling of dangerous chemicals which must be handled with care and which create pollution problems, and it can be safely processed with water alone. 

Because of these advantages, the Photopolymer Plate has been accepted by most of the leading Japanese newspaper companies and it is attracting more people in different field of the printing industry. 

We would like to express our sincere appreciation to the engineers of the major newspaper companies in Japan for their cooperation in presenting their valuable information and data on the evaluation of the Photopolymer Plate. 

Title IR Radical Polymerization-Type Photopolymer Plate Using Specific Binder Polymer... 

Fred Shubert (13) of our laboratory has made some studies using commercial photopolymer plates and exper-mental inks which were also studied for their emulsification and rheological behavior and are reported on later in this paper. 

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