No treatment CTP plate (3)
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Technical problem of developing type CTP without printing on a printing machine
As already mentioned above, the expectation for the second generation of unprocessed CTP plates is that the open system of the existing thermal imager can be used in the same way as the developed CTP plate. From the second half of 2005 to 2006, Fuji and Kodak produced unprocessed CTP plates (ECO & FREE SYSTEM ET-S, hereinafter referred to as ET-S) and Thermal Digital, but these were all on the press. The negative-type plate of the development mode has become the mainstream of the development-free CTP on the printing press. The following focuses on ET-S.
ET-S started with the four points listed in Table 3 as the main goal:
Main objective design policy
No treatment, on-board development 1. Implementation of development on a stripping machine
Excellent printing performance (using printability, aluminum hydrophilicity) 2. Treatment of development waste
High performance with thermal imaging machine High-speed thermal polymerization (high sensitivity) 3. High sensitivity design
Image clarity after exposure Introduced visible image formation reaction 4. Coexistence of high contrast coloring and printed image formation
As a basic design policy, the on-press development method is based on the use of a high-speed thermal polymerization system to achieve the same printability and sensitivity as the development type CTP plate. At the same time, the image sharpness after exposure, that is, for the plateau, introduces a visible image forming reaction. At the time of practical application, the main subjects of the picking are the realization of the development on the peeling machine, the processing of the waste after development on the printing machine, the design of the high-sensitivity photosensitive layer, the coexistence of the visible image formation and the formation of the printed image.
Main technology of untreated CTP plate ET-S
1. Stripping on-machine development
In order to achieve on-press development, if the functional design is carried out in the presence of the syrup, ink, and rolling, it is always in the developing environment during the printing process. If the photosensitive layer is designed to be dissolved in a syrup, development is easy, but it is not guaranteed to be resistant to India, but also contaminates the dampening solution, which affects printing performance. Therefore, it is necessary to remove a hydrophobic film which is insoluble to the medicinal water in the presence of a syrup, an ink, and a roll. The development profile shown in Fig. 1, that is, the formation of blisters in the photosensitive layer due to the penetration of the syrup, the formation of a water film which reduces the adhesion at the interface due to the roll pressure, and the mechanism of the peeling due to the viscosity of the ink, The process is an indicator, and the design of the photosensitive layer and the photosensitive layer-printing interface is implemented. As for the image portion, the penetration of the syrup is hindered by the curing of the photosensitive layer, and it is not developed even when exposed to the developing environment during the printing process.
2. High sensitivity design
In the case of the conventional non-treated CTP, the method of rinsing or utilizing hot-melt is the mainstream, but it is a very low sensitivity as the practical sensitivity is about 300 mJ/cm2. In the high-sensitivity image curing method combined with on-board development, a thermal CTP plate of a high-speed thermosensitive polymerization system has been used in the newspaper industry (see Fig. 2). Further, in order to adapt to the unprocessed CTP plate material, the following technical construction was adopted.
In the past, in order to suppress polymerization inhibition by oxygen in order to suppress polymerization inhibition by a polymerization-based photosensitive material, an uppermost layer having an oxygen barrier property of 2 μm thick is provided. However, in order to coexist with the on-machine development speed, it is necessary to change the film thickness of the uppermost layer to 0.20 μm or less of 1/10. The high-thickness-thickness plate-like particles are added to the oxygen-depleting layer, and the desired oxygenation is achieved by the extremely thin layer according to the gas impermeability caused by the long distance.
As a result of the above, the practical sensitivity was 100 mJ/cm, and the sensitivity of the conventional untreated CTP plate was about three times, and the same sensitivity and equivalent productivity as those of the developed CTP plate which has been a problem for many years were completed. Furthermore, it can correspond to the FM screen of 20 μm, and achieves good performance in terms of resolution.