Comparative analysis of the three most popular pla

2022-08-01
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Comparison and analysis of three plate making methods for plate printing release date: Source: China paper

in various processes of packaging and printing, various plate making methods are often used. Today, we will adjust the push board to the inside. China paper industry will take you into the cardboard way and introduce the relevant contents in detail

classification of plate making

plate making methods using materials

direct plate making method includes light paste photosensitive film for energy-saving vehicles and electric vehicles, wind turbines and hydrogen and natural gas storage tanks

direct and indirect plate making photosensitive film

1. Direct plate making method

⑴ photosensitive paste direct plate making method

method: coating a certain thickness of photosensitive paste (usually diazonium salt photosensitive paste) on the stretched plate, After coating, it is dried, and then it is exposed in a plate printer with a plate making negative. After development, washing and drying, it becomes a silk printing plate

process flow: preparation of photosensitive paste stretched degreasing drying coating drying exposure development drying revision final exposure sealing methods and functions of each section degreasing: degreasing agent is used to remove the grease on the silk so that the photosensitive paste and the silk can be completely glued together to prevent the film from falling off

drying: dry the moisture to avoid the tension change of the cloth due to excessive temperature. The temperature should be controlled at 40-45 ℃

photosensitive paste preparation: mix the photosensitizer with pure water, add it into the photosensitive paste, stir it evenly, and then reuse it after 8 hours

coating: the photosensitive paste is evenly coated on the silk by the scraping groove. It is divided into automatic coating machine coating and manual coating according to the coating method. The coating times can be determined according to the actual situation

when coating, the scraper surface should be coated first, in order to fill the gap between the yarn and the ground to avoid bubbles, and then the printed surface (the side in contact with PCB) should be coated. The automatic coating machine currently used can increase the film thickness by about 3um each time, Therefore, the coating method of solder mask is mostly selected as follows: two times of coating on the scraper surface - drying - three times of coating on the printing surface - turn off the workbench hand wheel - drying - three times of coating on the printing surface - drying

correct and incorrect description of coating method:

a. the correct thickness of coating scraper surface and printing surface is appropriate, Meet the requirements

b. thin film (printing surface) disadvantages: poor durability

c. the film on the scraper surface is too thick disadvantages: because the photosensitive paste on the scraper surface is too thick, the photosensitivity is uneven. During development, after water washing, the rough surface ink is poured into the film layer, causing the film layer to fall off, resulting in shorter plate life

d. the film on the scraper surface is too thin: poor durability

drying: dry the photosensitive paste evenly to avoid drying the outside and wetting the inside. Too high a temperature will make the outside photosensitive paste dry first but the inside is not dry, and shorten the service life of the plate. The temperature should be kept at 40-45 ℃ for 10 minutes. The drying time should be adjusted appropriately according to different film thickness

exposure: proper exposure can make the photosensitive paste photosensitive and polymerized, and the external wall insulation material is pushed to the forefront of the storm through the plate development to produce a clear image

factors affecting the quality of the plate:

a. correct exposure energy

b. exposure and vacuum degree

c. cleaning of the exposure machine glass

generally, the exposure energy is adjusted by the exposure time. During the production, the correct exposure time of various plates should be determined by using the exposure measuring film according to the plate mesh and film thickness

how to use the measuring film:

① expose it with the pre estimated exposure time and double the time, develop it in a normal way, select the one with the best effect, that is, the clearest image range, and multiply the actual exposure time by the marked coefficient on the selected image, that is, the better exposure time

there are 5 coefficients on the measured film, i.e. 1.0 0.7 0.5 0.33 0.25. Each coefficient corresponds to a circular target pattern and point respectively.

② if the coefficient 1.0 seems to be the best coefficient, it is necessary to double the previous exposure time and re make the exposure test

③ if the coefficient of 0.25 seems to be the best coefficient, reduce the exposure time by half and repeat the plate making exposure test

④ if several consecutive coefficients are satisfied, the coefficient with a smaller upper limit shall be used when drying the dot pattern, that is, the exposure time is shorter, and the coefficient with a higher lower limit shall be used when drying the thicker lines, that is, the exposure time is longer

⑤ if several consecutive coefficients are satisfied, select the best coefficient by comparing the sharpness of the thinnest line or point of the circular target according to the type of plate making

in addition, the close pasting of the negative film, the glass cleaning of the exposure machine, and the degree of vacuum pumping all have an important impact on the print quality

development: make use of the water solubility of the photosensitive paste, wash the unexposed photosensitive paste with water, and the development method has a great impact on the fine version. Before development, water must be sprayed to make the photosensitive paste absorb water and dissolve, let it stand for 1-2 minutes, and then use the high-pressure water gun to develop back and forth in a fan shape until the image is completely clear

note: high pressure water washing should not be too close to the plate, generally 0.8-1m, otherwise the lines are prone to serration due to too much pressure, and some points will be washed away in serious cases

drying: dry the water on the plate, and the temperature should not be too high, otherwise the plate tension will change, generally 40-45 ℃

revision and inspection: repair and inspect the pinholes and some npth holes

final exposure: further improve the adhesion between the photosensitive paste and the yarn, and increase the service life

sealing: fill the empty part of the plate with sealing paste to avoid ink leakage during printing

⑵ photographic film direct plate making method

process flow: stretched - - degreased - - wetted - - film pasted - - dried - - reinforced - - exposed - - developed - - dried - - revised - - sealed

method

photographic film is commonly known as water film. It is made of a transparent plastic film with a thickness of 0.1mm as the film base and coated with a layer of photographic emulsion with a certain thickness on one side. When using it, the silk is fully wetted and then the film is pasted, The film is adsorbed to the silk through capillary action, and then the plastic film base is torn off after drying for exposure and development, and finally the desired pattern is obtained

wetting: wetting is used to promote the formation of a uniform water film on the surface of the silk, so that the photosensitive film can be transferred smoothly

film: stick the photosensitive film onto the wet blade surface of the plate according to the plate type, and scrape off the excess water with the blade after pasting

drying: generally, it should be dried below 40 ℃. After drying, tear off the plastic sheet base and allow it to dry for a few more minutes.

reinforcement: if you need to increase the number of printing plates, you can apply a layer of photosensitive paste on the scraper surface after the film is dry and dry it after coating

other operations are the same as the photosensitive paste plate making method

2. Direct and indirect plate making method

method

direct and indirect plate making method is to first lay the wrist base photosensitive film coated with photosensitive material face up on the worktable, lay the stretched wrist frame flat on the film base, then put photosensitive paste in the frame and apply it with a soft scraper under pressure. After drying, remove the plastic film base, attach the wrist wire of the photosensitive film, and then use it for plate printing. After development and drying, a silk printing plate is made

process flow:

stretched - degreased - dried - stripped film base - exposure - Development - drying - Revision - sealing

3. Indirect plate making method

method

indirect plate making method is to expose the indirect film first, harden it with 1.2% H2O2, develop it with warm water, and dry it to make a strippable graphic negative. During plate making, stick the adhesive film surface of the graphic negative to the stretched wire, compact the adhesive film with the wet wire by extrusion, and remove the film base, The screen printing plate is made by air drying

process flow:

1 Stretched - degreased - dried

2 Indirect film - exposure - hardening - development

1and2- fitting - drying - Revision - blocking

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