Screen printing screen making process

Screen printing screen making process

Silk screen is the core tool of screen printing technology. It is made by screen printing mesh, screen printing frame and photosensitive emulsion layer. The main principle is to utilize the exposure and development characteristics of the photosensitive emulsion to form a contrast structure on the screen surface, which is printing area and non-printing area.

Before making the screen printing screen, we need to choose suitable screen printing accessories, such as screen printing mesh opening, screen printing frame material, inkjet film and so on. After the preparation, we can start making screen.

First, we need clean the screen printing frame. Commonly we choose aluminum material frame because of its high flatness and anti-deformation ability. Use a knife or a special scraper to thoroughly scrape off the old mesh, photosensitive emulsion, ink and other residues on the screen frame. The cleaned screen printing frame must be completely dry. It can be air-dried naturally or dried with a cold air blower to avoid moisture affecting the subsequent application of photosensitive emulsion or mesh attachment.

Second step is to tension the screen printing mesh and paste it on the screen printing frame. The screen printing mesh is stretched to the target tension (usually 18-25N/cm²) by a screen stretching machine to ensure average tension. Apply screen frame adhesive evenly along the edge of the frame to secure the mesh and leave it to cure for 24 hours. After that, we need to use a tensiometer to detect the tension of the four corners and the center of the screen, the error should be controlled within ± 1N/cm². Next, we can use a thermal cutter or sharp hobby knife to remove excess screen printing mesh along the outer edge of the frame to avoid tension changes caused by pulling.

Third one is wash the screen printing screen. Clean the screen with a neutral degreaser (e.g. 5% sodium carbonate solution) to remove grease and dust and enhance photosensitive emulsion adhesion. It should be noted that after washing, it needs to be dried with non-woven cloth. And it is prohibited to touch the mesh surface directly with hands.

There comes the most important step, apply photosensitive emulsion. In this step, we need to use the emulsion coater. The emulsion coater is a total of 3" larger than your printer area. Just a reminder, to have coaters work best please clean the coating edge each time after use. A emulsion coater is used to uniformly apply the photosensitive emulsion on both sides of the screen printing screen. The thickness of the photosensitive emulsion layer is controlled by coater pressure and speed (usually 5-8 μm). Coat the printing side that touches the substrate first, then coat the squeegee side, repeat 2-3 times to obtain an average emulsion layer.

After applying the photosensitive emulsion, we need to exposure the screen printing screen to cure the emulsion layer. Proper screen exposure is crucial for sharp image reproduction. Before exposure, be sure to check the inkjet film carefully for damage to ensure the quality of the screen. Place the inkjet film with the pattern side laminated to the screen in a screen printing exposure unit. The exposure time is determined by the intensity of the light source and the type of photosensitive emulsion (usually 30-120 seconds), and the optimum length is determined by exposure testing.

Thoroughly wet both sides of the screen in room temperature water for 1-2 minutes. Subsequently, use a high-pressure water gun to rinse the screen evenly until all the patterns are clearly visible. In this process, need to pay attention to the distance between the water gun pressure and the screen to prevent too much pressure or distance too close to the edge of the line resulting in jagged or broken dots, lost. After the developing process is completed, the screen will be placed in the oven at 40 ℃ drying to remove excess moisture. 

Last part is checking and repairing. If there are pinholes or white spots on the screen after developing, we can use the screen sealer to make spot repairs, paying attention to controlling the thickness of the adhesive to avoid over-thickness or over-thinness. After the glue is dry, the second exposure on the surface of the printing , the exposure time is set to twice the time of the plate, which will help to improve the print resistance of the screen plate. The finished screen should be labeled with a clear number and time label to facilitate subsequent tracing and searching.

Screen printing screen making is a technology that combines science and experience, and precision control of each step is crucial. With the development of digital technology, part of the process (e.g. tension control, exposure parameters) can be accurately regulated by automated equipment, but the operator's accumulated experience is still the core of quality assurance.

If you want to know more details about screen printing screen, please contact at +86 15097355251