Screen Printing Technology for TV Plastic Cases

Fuzhou Huaqiao Plastics Factory in Fujian Province uses screen printing technology to print characters and designs on plastic cases such as television sets, remote controls, CDs, and monitors. These printed objects have flat surfaces, curved surfaces, and low-spherical surfaces. I have been engaged in screen printing technology for 13 years and have accumulated some experience. These experiences are now introduced to comrades in the industry for reference.

1. Ink preparation

The factory is commonly used by the Japanese Empire and Toyo ink; screen printing effect is good. It is said that Empire ink screen printing is better, and Toyo ink gravure printing is better. Take a small amount of ink on the screen before each screen printing and dilute it with a thinner. If the temperature is high or the climate is dry, add 709 slow-drying agent or benzyl alcohol slow-drying agent.

To determine the degree of thickening and deciding: After the ink has passed through the screen, the printed surface is free from screen reticulation or drawing. The degree of leanness is placed on the screen, and the ink can reach through the mesh with its own weight, but it is not preferable to drop it. When the printed lines are thin, the spots should be thinned. On the contrary, the thick spots should be adjusted.

2. Screen selection

The quality of silk cloth is best in Switzerland. The wire diameter is uniform, the number of meshes is exactly the same, and the wire quality is stable. The silk market in Murakami, Japan used by the factory is also good.

The mesh used by the plant is 450-500 mesh. Thin substrates with high fineness, high ink density, and poor absorption should use screens with a high number of screens. Conversely, screens with a low number of screens should be used.

The position of the graphic and text on the screen and the size of the screen during plate making should be determined according to the structure and size of the substrate and the position of the graphic on the substrate. If the design is not good, it will affect the quality of screen printing, and even screen printing. In addition, it is better to use a screen printing for the graphic on the same printed matter. If divided into two online printing, the process will reduce the silk screen pass rate.

3. Scraper selection

The factory uses a squeegee made of polyurethane. Polyurethane rubber blade wear resistance, solvent resistance and resilience are better. Its hardness is selected from 60 to 80 Shore. Screen tension, good surface smoothness, should use high hardness scraper. On the contrary, low hardness should be used.

When printing on curved, low-spherical or poorly flat (partially convex) substrates, the width of the doctor blade should be narrow and not wide.

4. Screen positioning

The fixture materials used in this factory include metal, wood, plywood, and PVC transparent sheet. If it is difficult to position and the size of the substrate is small, metal fixtures should be used.

As the picture is closer to the edge of the sheet, a flat piece of wood that is as high as the edge of the sheet should be fixed beside the sheet so that the text is not easily pasted.

The net distance is generally 1.0-2.5mm. If the printing pattern is easy to be lumpy or there are reticulations, the net pitch should be adjusted.

5. Screen printing process
If the squeegee pressure is high, the amount of ink discharged is large, but the screen plate is easily deformed, so the squeegee pressure should not be high. The squeegee speed is usually 60 to 200 mm/s. Squeegee speed is quick and there is less ink, but it is not easy to block the net. So easy to block the network of ink, scraping speed should be faster.

The squeegee routes are straight, oblique, and curved. The choice should be based on the flatness of the substrate and the distribution of the graphic on the substrate. When the length of the squeegee line and the ink consumption are large, the amount of squeegee should be more or even a layer of ink, and then the squeegee should be squeegeed.

The screen printing experience introduced in this article is not only applicable to plastic substrates for television sets, but also to screen printing on other rigid plastic shells.



Source: Fuzhou Huaqiao Plastic Factory Huang Yaofeng