Packaging and Printing Process (2)

PS version of the sun for the strict requirements of the original version, the density of the positive image of the field should reach more than 4,0, clear outlets, blank film base fog is small, the original should be clean, collage should not be too much. The light source is a metal halide or ultra-high pressure mercury lamp.
The PS plate has fine sand and smooth surface. When the plate is vacuum-operated, the air between the PS plate and the bottom plate tends to be drawn out first and close to each other, while the middle part of the air is sealed due to the surrounding parts. A gap was formed between the bottom plates, and the middle part of the sun-printing site was made empty.
In order to avoid this kind of trouble, the PS plate that is produced abroad is often surface treated, that is, on the photosensitive layer of the PS plate, a layer of 25-35 lines/cm is printed by screen printing or gravure printing, and the thickness is about 1UM. Soluble polyvinyl alcohol colorless transparent material, surface convex shape such as 3-4 into a network of points and countless channels, in the printing plate suction, it is conducive to all the air between the PS plate and the bottom plate. In addition, the second suction method can solve the poor adhesion failure, the specific method is, when the suction plate found on the bottom of the interference pattern, stop pumping, until the bottom of the PS and the plate between the end of the air pressure to the surrounding, After destroying the sealed state, secondary air evacuation is performed to achieve uniform adhesion between the bottom plate and the PS plate, which is ready for exposure.
Determining the correct exposure time is the key to printing. Every purchase of a PS version requires testing to find the correct exposure time. Generally, step exposure can be performed according to the number of poles of the continuously adjustable density step scale that should be sunscreened according to the product specification. That is, once each exposure, increase 0, 5MIN or 1MIN. After several times of exposure and development, find out the specification The exposure time of the set number of sun exposures is determined as the correct exposure time of the product.
If there is no specific requirement for the product, the Bruner test strip can be used for testing. The method is to use a test strip to perform step-by-step exposure, and after development, select the black dots (positive points) that are true and not false and their corresponding The exposure time used for the unpopulated hollow point (female) is the correct exposure time for the product.
As the printing pressure is greater than the proofing pressure, the dots are increased when printing, so the printing plate should be lighter than the proofing plate. The difference is generally around 1%:
Proofing version: 1%～99% Yang Dian printing plate: 2%～98% When the positive point is controlled by Bruner signal bar, if there are many sun spots and fewer positive spots, the exposure time is too long. If there are fewer shade points and more masculine points, the exposure time is too short. The positive PS version is within the control range of exposure latitude. It is advisable to expose some more to facilitate the development and layout cleanliness. Generally, the exposure of the printing plate can be one time, but when there are many side marks, dirty spots, and redundant gauges on the plate, it is very troublesome to remove the dirt in the latter stage, and the optical film can be removed by the diffusion film exposure method.
Scattering film is a frosted film of transparent film that is roughened on both sides and is mounted on the side of the frame glass of the printing machine. The roll-up device controls its rolling. The use of a scattering film to remove dirt requires two exposures. The first time for the main exposure without the diffusion film, the master has less than 1/5 less than the normal exposure time; the second time is the secondary exposure with the diffuser film, and the main exposure time bench is 1/2. When the dirt removal method is used to treat a large area and the exposed layer is firmly bonded, the dirt removal effect is poor, and the net point has a certain influence (reduction). It is more suitable for text, newspapers and magazines in addition to dirty version.
(2) Development of PS plates for different types of sensitizers requires developers with different compositions and different concentrations. It is generally supplied with the PS version.
The development time can be controlled at about 2MIN. When the layout is clean, the development time should be shorter, which is good for the graphic part of the good lipophilicity, the network point is clean and complete. The developing method is shown in the table:
(3) Exfoliate (correction fluid) by applying a thin layer of ink on the surface of the brush, dissolve it, and rinse with water.
(4) The revised revision fluid is supplied by the finished product. Before use, the place to be repaired should be washed with clean water. It is best to use a 2% phosphoric acid solution for cleaning and dry it with hot air. Use a dry brush to apply repair solution to fill the defect area. Then dry it with hot air. Can also be used for gravure with gravure or positive PS type photosensitive resin patch repair.
(5) Erasing After the plate is repaired, evenly apply a layer of gum arabic protection liquid to protect the printing plate. (to be continued)