Abstract: This article introduces the screen printing process of silicone rubber, analyzes the difference between it and ordinary screen printing process, explains its technical characteristics, and summarizes its own opinions on technical control.
Keywords: silicone rubber, screen printing, printing quality With the rapid development of communications, electronics industry, rubber button production has also developed into a mature technology. These key products are made of silicone rubber through high temperature molding, forming the required key surface, and then formed by spraying, screen printing, punching and stripping. I am here to make a preliminary discussion of this screen printing process.
First, the characteristics of silicone rubber buttons as the key material of silicone rubber, the hardness is generally around 45 °, printing a single key surface convex, concave solitary surface and plane, all printed on the field lines. In addition to the requirement for accurate printing and clear graphics, printing requires the ink to be suitable for printing silicone rubber. The ink layer reaches a certain thickness, has strong adhesion and wear resistance, and does not change color after baking at high temperature. Therefore, it puts forward special technical requirements for the screen printing process.
Second, screen printing process
There are many screen printing platemaking methods, mainly photolithography method, that is, the photosensitive adhesive is directly coated on the Internet, and a certain thickness of the photosensitive film is formed into a graphic carrier after drying. The process flow is:
Network selection→selection frame→stretching→cleaning wire mesh→drying→emulsion coating→exposure→developing→printing specific process is as follows:
1. The aluminum frame is generally made of aluminum alloy, which is easy to operate and has great strength and is not easily deformed. Before the net is stretched, the net frame is wiped with cyclohexanone to remove the remaining grease and dirt, then wiped with industrial alcohol, and finally washed with water, and then dried the net frame. In the screen printing plate operation, it is necessary to dry many times, so the drying conditions and cleaning should be strictly controlled.
2. Stretch nets are firstly screened. Nylon silk screens are used for rubber screen printing. The ink has a good mesh rate and a constant tension. The screen can be used to cover the edge of the mesh frame, and the outer screen of the frame is 6 to 10 cM. The net machine stretches the net and uses a tensiometer to perform a six-point test. After the required tension is reached, the adhesive is coated so that the wire mesh sticks to the frame, and the hot air is used to speed the drying. After about 5 Min. The net machine sticks the extra screen to the outside of the frame to help maintain the fastness of the screen. Cut off the excess mesh and dry it after washing the mesh with cyclohexanone and industrial alcohol. If the tension of the stretch net is not stable, the font may be misaligned and blurred, and the substrate with the chord surface may cause a difference in ink layer thickness. Flat-faced printing needs to use a large-scale screen plate, and the arc-shaped printing surface needs to use a small-scale screen plate. The screen tension range of the process application is 3N/cM to 7N/cM. The general tension of the screen has a short service life, and the process should be selected according to needs: 100 mesh straight wire screen for printing conductive ink, 200 to 300 mesh diagonal screen for printing the right word, and color blocks to ensure the ink layer thickness and graphics. The integrity.
3. Manual lacquer coating is applied manually, the blank screen is leaned against the wall, coated with stainless steel coating tank for 2 to 3 times, the angle is about 50°, the bottom color of the adhesive layer is observed, and the thickness is measured with a film thickness meter. . The thickness of the emulsion with black ink and background color is 20-25μM. The thickness of the screen-printed emulsion with arc is 28±3μM. The thickness of the emulsion in different processes is different. It should be taken from the material and the thickness of the emulsion must be uniform. Into the oven drying temperature is controlled at about 40 °, to avoid the high temperature affect the performance of the photosensitive light, the safety of the light during the drying process, should adopt yellow lighting, avoid white light into the room, dry screen 10Min after exposure .
4. The exposure exposure is to chemically react the photosensitive film at the non-image area after exposure to light, and the molecular structure between the films is cross-linked and hardened. From soluble to insoluble, after the development, the light-blocking layer (hardened part) and the image part of the transparent mesh hole (no light-sensitive glue is dissolved in water) are formed so that the ink passes through the mesh to form a printing pattern. Exposure using a vacuum stencil machine, using transparent tape to paste the film on the screen, the film is facing up, the stencil is attached to the film, covered with a black cloth frame, put down the lid, start the suction device (pressure about 110 ~ 120pA), etc. The pressure is stable. After the cover is pressed against the glass, the exposure device is activated. The exposure time is set according to the nature of the photoresist, the thickness of the film, and the thickness of the image. Usually controlled between 20S and 60S.
5. Development Exposure of the screen plate to water after immersion 3 ~ 4Min, and then placed on a certain pressure under the water tube to rinse both sides of the film, until °C °C °C film part of the film washed clean, the image of the mesh thoroughly penetrated so far . After the graphic part and the non-graphic part are revealed, touch the surface with hands to have a smooth feeling, no trace of dissolution, filter the water droplets and send it to the drying box for drying. Drying screens generally require secondary exposures to enhance screen life.
6.Adjusting printing ink Silicone printing ink must be suitable for the physical and chemical properties of silicone rubber, and can be firmly attached to the printing surface. It is mixed with other inks by a certain proportion of pigments, binders, and solvents. Processed. Kerosene is usually used as a diluent, and a single-liquid type ink is added with a vulcanizing agent (a trace amount) to enhance the imprint adhesion and abrasion resistance, and the double liquid ink is directly printed. The storage temperature of the ink is controlled at 0 to 10°C, and it is dried at a high temperature after printing.
7.Prepare jigs, screens, and inks before printing and printing. The clean printing surface is free of oil stains. The surface is too smooth and must be treated with flame and corona to ensure that the ink adhesion is good. The slick screen rule is fixed on the machine. On the stage, the printing button is fixed on the fixture, the hardness of the scraper should be equal to the hardness of the rubber (about 55°), the positioning of the gauge line, the alignment of the screen on the screen and the alignment line on the cover plate, Accurately position the sample overprint. Adjust the distance between the screen and the printing surface so that the squeegee can contact the substrate well. The coverage of the ink stroke must be greater than 2 to 5 cM. The angle of the scraper is controlled at about 75°, and the first inspection must be performed during the printing. The sample is compared and the sampling is performed on time so that the product quality can be fully controlled.
Third, the process technology to discuss the screen copy of the film copy location must correspond with the fixture, when making the screen, the film and the screen close contact, to prevent the location of the movement, in the design process, thin lines should not rely too close, otherwise Can easily cause adhesions. If the background color printing is required, the background color is usually 0.1-0.2M smaller than the color of the surface, so that the printing surface can be completely covered and the product quality can be ensured. In the above process of copy screen printing, because the substrate is relatively soft and the tension of the screen is small, font blurring, inaccurate positioning, and inconsistency in the thickness of the ink layer are liable to occur during the processing of these problems. Must be carefully analyzed, there is a curved print surface with a small tension screen, and the scraper should not be too hard, the ink is better fluidity (but to control the font thicker), the squeegee scraping speed is controlled at 12 ~ 24cM / S. In the baking process of printed products, the oven temperature and baking time must be controlled to improve the product's adhesion.
Conclusion: Silicone rubber is a special kind of screen printing. In addition to soft substrates, soft squeegees are required. In addition to special inks, it is necessary to master the processes in order to print the ideals. The product. (Zhongda Printing Group Co., Ltd. Shenzhen Peng Ziyang)
Keywords: silicone rubber, screen printing, printing quality With the rapid development of communications, electronics industry, rubber button production has also developed into a mature technology. These key products are made of silicone rubber through high temperature molding, forming the required key surface, and then formed by spraying, screen printing, punching and stripping. I am here to make a preliminary discussion of this screen printing process.
First, the characteristics of silicone rubber buttons as the key material of silicone rubber, the hardness is generally around 45 °, printing a single key surface convex, concave solitary surface and plane, all printed on the field lines. In addition to the requirement for accurate printing and clear graphics, printing requires the ink to be suitable for printing silicone rubber. The ink layer reaches a certain thickness, has strong adhesion and wear resistance, and does not change color after baking at high temperature. Therefore, it puts forward special technical requirements for the screen printing process.
Second, screen printing process
There are many screen printing platemaking methods, mainly photolithography method, that is, the photosensitive adhesive is directly coated on the Internet, and a certain thickness of the photosensitive film is formed into a graphic carrier after drying. The process flow is:
Network selection→selection frame→stretching→cleaning wire mesh→drying→emulsion coating→exposure→developing→printing specific process is as follows:
1. The aluminum frame is generally made of aluminum alloy, which is easy to operate and has great strength and is not easily deformed. Before the net is stretched, the net frame is wiped with cyclohexanone to remove the remaining grease and dirt, then wiped with industrial alcohol, and finally washed with water, and then dried the net frame. In the screen printing plate operation, it is necessary to dry many times, so the drying conditions and cleaning should be strictly controlled.
2. Stretch nets are firstly screened. Nylon silk screens are used for rubber screen printing. The ink has a good mesh rate and a constant tension. The screen can be used to cover the edge of the mesh frame, and the outer screen of the frame is 6 to 10 cM. The net machine stretches the net and uses a tensiometer to perform a six-point test. After the required tension is reached, the adhesive is coated so that the wire mesh sticks to the frame, and the hot air is used to speed the drying. After about 5 Min. The net machine sticks the extra screen to the outside of the frame to help maintain the fastness of the screen. Cut off the excess mesh and dry it after washing the mesh with cyclohexanone and industrial alcohol. If the tension of the stretch net is not stable, the font may be misaligned and blurred, and the substrate with the chord surface may cause a difference in ink layer thickness. Flat-faced printing needs to use a large-scale screen plate, and the arc-shaped printing surface needs to use a small-scale screen plate. The screen tension range of the process application is 3N/cM to 7N/cM. The general tension of the screen has a short service life, and the process should be selected according to needs: 100 mesh straight wire screen for printing conductive ink, 200 to 300 mesh diagonal screen for printing the right word, and color blocks to ensure the ink layer thickness and graphics. The integrity.
3. Manual lacquer coating is applied manually, the blank screen is leaned against the wall, coated with stainless steel coating tank for 2 to 3 times, the angle is about 50°, the bottom color of the adhesive layer is observed, and the thickness is measured with a film thickness meter. . The thickness of the emulsion with black ink and background color is 20-25μM. The thickness of the screen-printed emulsion with arc is 28±3μM. The thickness of the emulsion in different processes is different. It should be taken from the material and the thickness of the emulsion must be uniform. Into the oven drying temperature is controlled at about 40 °, to avoid the high temperature affect the performance of the photosensitive light, the safety of the light during the drying process, should adopt yellow lighting, avoid white light into the room, dry screen 10Min after exposure .
4. The exposure exposure is to chemically react the photosensitive film at the non-image area after exposure to light, and the molecular structure between the films is cross-linked and hardened. From soluble to insoluble, after the development, the light-blocking layer (hardened part) and the image part of the transparent mesh hole (no light-sensitive glue is dissolved in water) are formed so that the ink passes through the mesh to form a printing pattern. Exposure using a vacuum stencil machine, using transparent tape to paste the film on the screen, the film is facing up, the stencil is attached to the film, covered with a black cloth frame, put down the lid, start the suction device (pressure about 110 ~ 120pA), etc. The pressure is stable. After the cover is pressed against the glass, the exposure device is activated. The exposure time is set according to the nature of the photoresist, the thickness of the film, and the thickness of the image. Usually controlled between 20S and 60S.
5. Development Exposure of the screen plate to water after immersion 3 ~ 4Min, and then placed on a certain pressure under the water tube to rinse both sides of the film, until °C °C °C film part of the film washed clean, the image of the mesh thoroughly penetrated so far . After the graphic part and the non-graphic part are revealed, touch the surface with hands to have a smooth feeling, no trace of dissolution, filter the water droplets and send it to the drying box for drying. Drying screens generally require secondary exposures to enhance screen life.
6.Adjusting printing ink Silicone printing ink must be suitable for the physical and chemical properties of silicone rubber, and can be firmly attached to the printing surface. It is mixed with other inks by a certain proportion of pigments, binders, and solvents. Processed. Kerosene is usually used as a diluent, and a single-liquid type ink is added with a vulcanizing agent (a trace amount) to enhance the imprint adhesion and abrasion resistance, and the double liquid ink is directly printed. The storage temperature of the ink is controlled at 0 to 10°C, and it is dried at a high temperature after printing.
7.Prepare jigs, screens, and inks before printing and printing. The clean printing surface is free of oil stains. The surface is too smooth and must be treated with flame and corona to ensure that the ink adhesion is good. The slick screen rule is fixed on the machine. On the stage, the printing button is fixed on the fixture, the hardness of the scraper should be equal to the hardness of the rubber (about 55°), the positioning of the gauge line, the alignment of the screen on the screen and the alignment line on the cover plate, Accurately position the sample overprint. Adjust the distance between the screen and the printing surface so that the squeegee can contact the substrate well. The coverage of the ink stroke must be greater than 2 to 5 cM. The angle of the scraper is controlled at about 75°, and the first inspection must be performed during the printing. The sample is compared and the sampling is performed on time so that the product quality can be fully controlled.
Third, the process technology to discuss the screen copy of the film copy location must correspond with the fixture, when making the screen, the film and the screen close contact, to prevent the location of the movement, in the design process, thin lines should not rely too close, otherwise Can easily cause adhesions. If the background color printing is required, the background color is usually 0.1-0.2M smaller than the color of the surface, so that the printing surface can be completely covered and the product quality can be ensured. In the above process of copy screen printing, because the substrate is relatively soft and the tension of the screen is small, font blurring, inaccurate positioning, and inconsistency in the thickness of the ink layer are liable to occur during the processing of these problems. Must be carefully analyzed, there is a curved print surface with a small tension screen, and the scraper should not be too hard, the ink is better fluidity (but to control the font thicker), the squeegee scraping speed is controlled at 12 ~ 24cM / S. In the baking process of printed products, the oven temperature and baking time must be controlled to improve the product's adhesion.
Conclusion: Silicone rubber is a special kind of screen printing. In addition to soft substrates, soft squeegees are required. In addition to special inks, it is necessary to master the processes in order to print the ideals. The product. (Zhongda Printing Group Co., Ltd. Shenzhen Peng Ziyang)
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