Screen printing technology decorative flat glass
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According to the principle of silk screen printing, the ink is printed on the surface of the flat glass, and then the curing action of the ink is adopted to make the pattern durable and durable. The process is as follows:
Stretching net→sizing→drying→printing→developing→drying
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Flat glass → cutting → edging → cleaning and drying → printing
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Sintering
Suitable for printing glass
According to the user's requirements, the glass can be cut into regular shapes or irregular shapes, then be edged and ground, then cleaned and dried for use. Special attention should be paid here to the fact that the surface of the flat glass cannot have water marks.
Screen selection
The screen printing plate for flat glass printing is the same as the general screen printing plate, and the glass screen printing plate is made of synthetic fiber mesh, stainless steel wire mesh and natural fiber mesh. When printing general color materials, the above-mentioned one kind of wire mesh can be generally used as an inexpensive synthetic fiber mesh; when it is decorated as gold and silver, stainless steel wire mesh cannot be selected. The specifications of the wire mesh are generally 270 to 300 mesh.
Frame selection
At present, the frame that is relatively regular and has little deformation is an aluminum alloy frame, and its size should be larger than the pattern. The specific size should be that the outer edge of the pattern should be between 70 and 100 mm from the frame. In addition to selecting the frame, its strength is very important, the key is that the rigidity in the horizontal direction is sufficient.
Stretch
I chose the net and the net frame to combine the two. This is the stretch net. There are many ways to stretch the net. It can be manually, maneuvered or pneumatic. At present, the more advanced, high-quality screen version is a pneumatic stretcher. The requirement of the stretch net is that the tension is uniform, the latitude and longitude of the screen is kept vertical, and the adhesive mesh is firm and cannot be relaxed.
Select photosensitive adhesive
Currently, commercially available photosensitive adhesives are dichromate, diazonium, and iron salts. The requirement of silk screen printing for photosensitive adhesive is: good plate making performance and easy coating. The sensitizing spectrum ranges from 340 to 440 nm, with good developing performance, high resolution, good stability, easy storage, economical, non-toxic and pollution-free. The requirement for printing on photosensitive materials is that the film formed by the photosensitive material is adapted to the performance requirements of different types of inks. It has considerable printing durability and can withstand the scraping pressure of the squeegee plate. The bonding force with the screen is good, no filming failure occurs during printing; it is easy to peel off, which is beneficial to the recycling of the screen plate. The DS series of photosensitive adhesive produced by Beijing Taipingqiao Printing Materials Factory has a good effect and basically meets the requirements of flat glass screen printing.
Printing
After selecting the above materials, the photosensitive adhesive is applied in the dark room; the requirements are uniform and then dried, and it is generally required to be applied twice. The printing plate is required to be exposed on a cold light source printing machine, and the exposure time is determined according to the pattern, generally between 12 and 30 minutes. Screen printing screens are produced after exposure and development.
Printing
There are several types of flat glass printers: manual, semi-automatic and fully automatic. The manual press is suitable for small-volume, small-size flat glass. The semi-automatic and fully automatic printing machine is suitable for printing in large quantities and large specifications, and has the advantages of accuracy and speed. The largest semi-automatic press can print glass of 2000 × 1500mm size. Fully automatic printing presses are generally used for the printing of automotive windshields, and several companies abroad can provide such equipment.
Oil ink
Flat glass decorative inks are divided into two types: organic inks and inorganic inks. The coloring agent and connecting material of the organic ink are all organic substances. The effect of the ink to decorate the flat glass is also good, but the film has poor firmness and poor chemical stability, and is a short-life decorative method. The inorganic ink is composed of a coloring agent, a fluxing agent and a connecting agent, and the coloring agent is an inorganic coloring agent such as chromium oxide, cobalt oxide or the like. Flux is a low melting point glass, and common lead oxide and borosilicate glass. The most important thing about the performance of the flux is that it does not differ much from the coefficient of thermal expansion of the printed glass. The composition of the typical flux is: SiO2 19182%, As2O3 2113%, MgO 0146%, PbO 62110%, CaO 0127%, K2O 1183%, B2O3 10175%, Al2O3 1163%, Na2O 1176%. The binder in inorganic inks - the scraper oil is an organic substance that is completely burned off during the sintering process, but has no effect on the decorative effect.
The composition of the scraper oil is: ethyl cellulose 3g, terpineol 100ml, turpentine 10ml, alkyd resin 5ml. The ratio of the pigment of the inorganic ink to the binder is 10 g: 8 ml, which can be obtained by stirring and grinding.
Burnt knot
Glass is an amorphous inorganic material that softens as the temperature increases, and when heated to the softening temperature of the glass, the glass deforms. The glass glaze is decorated on the surface of the flat glass by silk screen printing, and needs to be fixed to the glass surface by high temperature sintering, but the sintering temperature must be lower than the softening temperature of the decorative glass to ensure that the decorative glass is not deformed. Generally, the glass glaze has a sintering temperature of not higher than 520 ° C, and is usually controlled at 480 to 520 ° C.
Low-temperature glass glazes are produced by several domestic manufacturers and the prices are relatively low. There are several companies in the world that can provide similar products, but the price is one to twenty times different from that of domestic ones. Domestic consumption levels have not yet reached the level of using such glazes, but the glazes provided abroad are indeed much better than the domestic colors and levels. To improve the quality of decorative glass, it is inevitable to improve the grade of glaze. The sintering equipment has a flame furnace and a resistance furnace. The electric resistance furnace is divided into a vertical hanging type and a horizontal roller type according to the hanging manner of the glass. The vertical hanging sintering furnace has the advantages of small sintering deformation and a yield of over 95%, but the equipment is complicated. Horizontal roller type adjustment is not easy to occur, large deformation, low yield, etc. In addition, the use of horizontal steel furnace to produce decorative glass is also feasible, the product grade is improved, safety is also guaranteed, is the ideal sintering method