Discussion on the printing process of PS

In the printing industry (whether it is printing paper or printing iron), the PS plate is used as the medium for lithographic offset printing. It is usually an aluminum alloy plate with a thickness of 0.15-0.30mm and is coated with a layer of photosensitive liquid; it is used according to different occasions. Requirements, size can be selected or decided. In the printing industry, the printing pattern is transferred to the surface of the iron sheet through the principle of ink-ink balance under the proper printing pressure by the three-drums of printing plate cylinder, blanket cylinder and impression cylinder. The quality of the printing plate depends on the PS plate. The process of drying and other influencing factors, it should be said that the quality of the printing plate is a prerequisite and fundamental for the quality assurance of printed products.

This article only describes and discusses some of the details that should be noted in the process of drying the PS plate.

PS printing process can be simply illustrated as three basic links, namely exposure - development - protective plastic.

One, exposure

The exposure of the PS plate with the photosensitive layer is placed on the platen of the plate, the film is placed, and the pattern on the plate is displayed on the PS plate by double exposure of the main light and the light transmission. (Note: Each model For the PS version, it is recommended to use a 1KW light source with a 3kW iodine lamp and a 1M lamp version.

The work program of the printing plate is controlled automatically, but pay attention to the following basic details, mainly including:

1. The position of fangs or bite should meet the technological requirements. (1) When the plates are the same size as the sheet metal, it should be noted that the 1mm in front of the layout must show crosshairs in left-empty county, and the left and right sides should also expose the + word line; (2) If the sheet size is surplus, it is necessary to negotiate with the merchants clearly. The position of the iron is left blank; for customers with special residual iron requirements, they must meet the corresponding standard requirements, so that they are reserved during the printing; (3) When the size of the printing plate exceeds the size of the metal sheet, the original position can be covered with the iron sheet after the exposure. Expose and remove unwanted images. These are special circumstances, and the general version must be consistent with the size of the sheet metal, so that it is economical and reasonable and meets the process requirements.

For example, when using the 0.23*712*512/MRT4 tinplate as the crown cover, the size of the core is 712*505mm2. When the printing is in front of the printing version, the blank space can be appropriately 1-3mm, and the position of the teeth can be set aside. 6mm gap (this example refers to Japan Fuji Machinery PRIMEX-F450 printing plate description).

2. Before starting the power of the printing machine, it is necessary to check whether there are foreign objects such as a ruler and a revised knife on the work table. Otherwise, the glass frame of the machine table will be exploded.

3. After positioning the PS plate to be positioned, it must be noted that the vacuum vents on the side of the machine table must not be covered.

4, the setting of exposure time: the main exposure time is usually set at 90-100S, auxiliary light at 15-20S. (1) The exposure time is too long, the pattern on the PS plate is brittle, and it is easy to fall off and lose some of the cable, and the printing plate is resistant to printing force; (2) The exposure time is not enough, and the exposure is not enough, the color of the pattern will appear light and empty. False; (3) When the lamp's long-term use performance deteriorates, the exposure time can be extended or replaced.

5, PS version of the take: should be careful not to make a "dead mark", otherwise it is easy to print patterns blurred, ink emptiness, poor coloring.

Second, development

After the development, the exposed PS plate is placed flat on the developer tank, and the developer is fully wetted. About 1 minute later, the coating is removed and placed on the plate cleaning station to wash away the dissolved coating, thus showing “image”. . The main points to note when developing:

1, the ratio of developer and water preparation. Generally, when the PS plate is purchased, a certain amount of developer is distributed with the plate. The ratio of the developer and the water is preferably slightly greater than or equal to the proportion of the original concentrate, particularly with respect to summer. If the concentration of the developer is too large to clear the effective dots, the concentration will be insufficient, the development time will be longer, and the layout will be dirty and affect the durability of the PS plate.

2, the development time control. Under normal circumstances, about 1 minute after the PS plate is placed in the liquid crystal display tank (conspicuous bubbles appear on the surface during development). Excessive development time will remove the “image” on the layout. If not enough time will be dirty on the layout.

3. If there are any extra spots or images on the plate after development, it can be removed with a revised paste and then rinsed with water. (Available in the revised version, a brush can be used to draw a moderate amount of paste, lightly applied to excess images or spots, and stay for a moment. Rinse with water).

4, the development temperature. It is suitable to perform at room temperature (23+2). Excessively high room temperature will degrade the reproducibility of the plate, and the temperature will lower the developing ability.

5, development should be carried out in the dark, avoid natural light.

Third, plastic protection

After the development, the graphic image part and the non-image graphic part of the surface of the PS plate shall be coated with a layer of gum arabic in order to prevent the plate from being dirty and the plate being scratched in the printing process. Although the plate protection work is simple and easy, The actual operation should also pay attention to, mainly in the following two aspects:

1, wipe the glue. (1) After the developed PS plate is cleaned with water, wipe the excess surface moisture with a rubber scraper or sponge to apply the glue. Can not be used when smear afraid of cotton towels or sponges to take appropriate amount of protective plastic in the vertical and horizontal lines in both directions to wipe, so that you can even thin flat (apply too thick and easy to peel off, too thin or uneven not Protective effects). (2) After wiping the glue, place the plate on the workbench to dry (you can use the fan in summer, use far-infrared light in winter, and store it in a stool, if conditions permit, you can use a baking machine to achieve better results).

2, clear version. For the reusable printing plate, after each use, the ink on the surface can be washed with gasoline or ink cleaning agent, cleaning paste, etc. to expose the "primary color" and then gluing. In addition to paying attention to the above three basic links, the printing work also needs to understand the closely related daily protection, school edition and other common sense.

(1) School edition. The school edition is the proofreading and proofreading of the originals on the school's edition table. The main contents include: 1. Size specification of the drafts; 2. Size of the cores; 3. Whether the “+” word line and the standard of the layout are coincident; Whether the network cable is clear; 5, the film does not have any scratches on the back of the bone (if necessary, use an opaque adhesive tape or drawing pen, add a pen, and remove the pen to repair the layout).

Note: 1. The size of the printing plate should be consistent with the size of the metal sheet; 2. The layout must have the "+" word line and the quasi-standard center line, which is the basic mark of the standard version; 3. The printing plate is usually marked with Y, M, C , K (respectively yellow, red, blue, black) four basic marks, and -10% -100% of the network lines indicate the color bars directly above the layout to show the sparse and dense contrast of the network lines with the main pattern.

(2) Storage and protection of printing plates. (1) When the PS plate is stored, moisture and high temperature should be avoided. The recommended storage condition is 10-30, and the relative humidity is not greater than the case that the plateau is easily alkalized to destroy the PS plate. (2) The room should be kept clean and dust-free to prevent direct sunlight; (3) When the reusable printing plate is stored, it is necessary to pay attention to the relative layout of the plates, and at the same time, it is better to separate them with a paper lining; (4) When the phenomenon of dirty spots, scratches, etc. occurs during printing, the machine can be shut down. The PS plate cleaning solution was applied to the layout and a small amount of fountain solution was added to the fountain to improve the print resistance of the plate to obtain excellent printing quality.

In short, the printing plate is an auxiliary work for the preparation of the printing process. Although the process is relatively simple, the quality of the printing plate directly affects the quality of the printed product.

In view of the above, during the actual operation, in addition to paying attention to the basic operation of the printing process and the various factors affecting the quality of printing, the status and role of the printing plate in the printing process cannot be ignored because: A well-qualified standard version will not show up again.