In the large-volume screen printing production process, if a specific link does not pay much attention, it will bring a series of troubles to the production, and this situation will not be resolved a day, it will always plague production.
Here, Bixun Xiaobian mainly discusses several problems that are often encountered in production but are easily overlooked.
—, the color of the screen
The colors of the screen are white, yellow, amber, red, and the like, of which the yellow screen is preferred. Our production of commonly used Japanese or German imports of 270 ~ 280T yellow screen, for particularly delicate prints, we often import 350T yellow screen.
Why use a yellow silk screen? We know that the brilliant colors of the natural world are all due to the effect of light. Without light, there is no color. The color of light is determined by the frequency of light waves. Red, orange, yellow, green, green, basket, and purple are the light that people's optic nerves can feel, called visible light. The surface of the object absorbs light selectively and reflects it to get different colors. In short, any color we can see is the color of light. That is, when a beam of light hits the surface of a yellow object, only the yellow light is reflected, irritating our visual nerves and coloring, while other colored light is absorbed, so we see that the color of the object is yellow.
Since the screen printing uses ultraviolet light during the exposure of the printing plate, the purple light is reflected by the mixture of two colors of cyan and magenta in the color, that is, it lacks a yellow hue in the black. At the time of exposure, the yellow of the purple screen mesh is superimposed on black, so the surface of the yellow screen (ie, the bottom of the emulsion layer) is not sensitive or less exposed, so that the phenomenon of “back exposure†does not occur and the resulting image has high definition. Does not produce vignetting.
What is back sun? That is, when light reaches the emulsion layer through the transparent portion of the film, reflections, refractions, and slow shots are generated on the surface of the white screen at the center or bottom of the coating layer, which is just exposed from the bottom and the inside of the coated surface. This phenomenon is called "back sun." It can cause halo when exposed, affecting the reproduction of tones.
Second, the coating of emulsion
The prepared photosensitive liquid was placed in a stainless steel tank, and the photosensitive liquid accounted for about half of the tank. The coating tank is in contact with the lower end of the inclined screen, and while the tank is tilted out of the photosensitive liquid, the tank is slowly and evenly lifted up and applied along the screen surface. The coating speed should not be too fast. If it is too fast, it will cause foaming of the emulsion and pinholes on the film surface. If it is too slow, it will cause uneven emulsion coating. In order to obtain the best coating effect, it is best to apply the coating from the side that is in contact with the substrate during printing. The area to be coated should be slightly smaller than the screen frame, and then turn the screen upside down and apply it again. Finally, The backside of the screen was coated and dried to allow the emulsion to fill the mesh. It is best to dry with 30-35°C hot air so that the drying time can be shortened. If the temperature is higher than 40°C, the screen will produce hot fog.
Sensitive emulsions have low sensitivity in the liquid phase, the sensitivity rises with the drying of the coating film, and can only reach the specified sensitivity after being completely dried. Therefore, sufficient drying is performed before the printing, and the printing is completed in a short time after drying. .
Of course, due to the different production conditions of various manufacturers, there are also differences in their coating methods and times. The coating method adopted by our factory is once in place, that is, coating the positive and negative surfaces three times at a time, and then drying in a concentrated manner.
Since the screen is covered with dust, the screen will have pinholes, so keep the room clean. At the same time, poor handling of screens can also result in excessive pinning of the screen surface. When the emulsion is coated, the drying place is too bright, which will cause the fog of the screen full-length image, and affect the clarity and saturation of the printed matter.
The screen printing of our factory mainly produces daily ceramic decals, mainly export products, supplemented by domestic products. The 20-piece tableware, noodle bowl, and cook plate that are exported to the United States, the United Kingdom, Canada, and other countries all year round are popular.
Third, printing, trimming
Before printing, you should check the photosensitive surface of the film and the glass surface of the printing table for dirty work or dust. It is best to clean it with cotton and alcohol before cleaning. The surface of the film with silver halide attachment is frontal, and the glossy side of the film is negative. When printing, the film surface of the film and the emulsion surface of the screen should be closely attached, leaving the bite line for exposure. Exposure time should be based on the type of photosensitive thorn, the coating thickness of the photosensitive film, the degree of blackness of the positive picture, and the printing requirements. The thicker the coating layer of the photosensitive film, the longer the exposure time required for the film to be completely cured. If the image on the Yang picture is not solid enough, ie gray but not black, the exposure time should be shortened and the development time should be extended accordingly so that the unilluminated image part is completely transparent.
Here, Bixun Xiaobian mainly discusses several problems that are often encountered in production but are easily overlooked.
—, the color of the screen
The colors of the screen are white, yellow, amber, red, and the like, of which the yellow screen is preferred. Our production of commonly used Japanese or German imports of 270 ~ 280T yellow screen, for particularly delicate prints, we often import 350T yellow screen.
Why use a yellow silk screen? We know that the brilliant colors of the natural world are all due to the effect of light. Without light, there is no color. The color of light is determined by the frequency of light waves. Red, orange, yellow, green, green, basket, and purple are the light that people's optic nerves can feel, called visible light. The surface of the object absorbs light selectively and reflects it to get different colors. In short, any color we can see is the color of light. That is, when a beam of light hits the surface of a yellow object, only the yellow light is reflected, irritating our visual nerves and coloring, while other colored light is absorbed, so we see that the color of the object is yellow.
Since the screen printing uses ultraviolet light during the exposure of the printing plate, the purple light is reflected by the mixture of two colors of cyan and magenta in the color, that is, it lacks a yellow hue in the black. At the time of exposure, the yellow of the purple screen mesh is superimposed on black, so the surface of the yellow screen (ie, the bottom of the emulsion layer) is not sensitive or less exposed, so that the phenomenon of “back exposure†does not occur and the resulting image has high definition. Does not produce vignetting.
What is back sun? That is, when light reaches the emulsion layer through the transparent portion of the film, reflections, refractions, and slow shots are generated on the surface of the white screen at the center or bottom of the coating layer, which is just exposed from the bottom and the inside of the coated surface. This phenomenon is called "back sun." It can cause halo when exposed, affecting the reproduction of tones.
Second, the coating of emulsion
The prepared photosensitive liquid was placed in a stainless steel tank, and the photosensitive liquid accounted for about half of the tank. The coating tank is in contact with the lower end of the inclined screen, and while the tank is tilted out of the photosensitive liquid, the tank is slowly and evenly lifted up and applied along the screen surface. The coating speed should not be too fast. If it is too fast, it will cause foaming of the emulsion and pinholes on the film surface. If it is too slow, it will cause uneven emulsion coating. In order to obtain the best coating effect, it is best to apply the coating from the side that is in contact with the substrate during printing. The area to be coated should be slightly smaller than the screen frame, and then turn the screen upside down and apply it again. Finally, The backside of the screen was coated and dried to allow the emulsion to fill the mesh. It is best to dry with 30-35°C hot air so that the drying time can be shortened. If the temperature is higher than 40°C, the screen will produce hot fog.
Sensitive emulsions have low sensitivity in the liquid phase, the sensitivity rises with the drying of the coating film, and can only reach the specified sensitivity after being completely dried. Therefore, sufficient drying is performed before the printing, and the printing is completed in a short time after drying. .
Of course, due to the different production conditions of various manufacturers, there are also differences in their coating methods and times. The coating method adopted by our factory is once in place, that is, coating the positive and negative surfaces three times at a time, and then drying in a concentrated manner.
Since the screen is covered with dust, the screen will have pinholes, so keep the room clean. At the same time, poor handling of screens can also result in excessive pinning of the screen surface. When the emulsion is coated, the drying place is too bright, which will cause the fog of the screen full-length image, and affect the clarity and saturation of the printed matter.
The screen printing of our factory mainly produces daily ceramic decals, mainly export products, supplemented by domestic products. The 20-piece tableware, noodle bowl, and cook plate that are exported to the United States, the United Kingdom, Canada, and other countries all year round are popular.
Third, printing, trimming
Before printing, you should check the photosensitive surface of the film and the glass surface of the printing table for dirty work or dust. It is best to clean it with cotton and alcohol before cleaning. The surface of the film with silver halide attachment is frontal, and the glossy side of the film is negative. When printing, the film surface of the film and the emulsion surface of the screen should be closely attached, leaving the bite line for exposure. Exposure time should be based on the type of photosensitive thorn, the coating thickness of the photosensitive film, the degree of blackness of the positive picture, and the printing requirements. The thicker the coating layer of the photosensitive film, the longer the exposure time required for the film to be completely cured. If the image on the Yang picture is not solid enough, ie gray but not black, the exposure time should be shortened and the development time should be extended accordingly so that the unilluminated image part is completely transparent.
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