Application of glass screen printing technology

From the traditional glass screen printing to the emerging LED and touch panel printing, silk screen printing technology runs through the entire glass industry and plays an important role in it.

Then, as one of the important fields in the silk screen industry, how important is the role of glass screen printing in the silk screen industry?

Glass Screen Printing Technology

Glass screen printing is the use of screen printing plates, the use of glass glaze, decorative printing on glass products. Glass glaze is also called glass ink and glass printing material. It is a paste-like printing material that is mixed and stirred by coloring material and linking material. The coloring material consists of inorganic pigments and low-melting fluxes (lead glass powder); the linking material is commonly referred to as linoleum oil in the glass screen printing industry. After printing, the glass products are placed in a stove and fired at a temperature of 520 to 600° C. The glaze printed on the glass surface can be consolidated on the glass to form a colorful decorative pattern. If you use silk screen printing with other processing methods, you will get better results. For example, by polishing, engraving, etching, etc., the glass surface is processed before or after printing, and the printing effect can be doubled.

Application of glass screen printing technology

The application of screen printing plate glass and its market prospect Screen printing plate glass is widely used in every corner of people's lives: You can easily find it in display windows, building space partition, building beautification, car windshield and mosaic glass and other places. Their presence. Simultaneously. They are also widely used in furniture decoration and game tools, as well as countless decorations and artistic creations. Screen printing has also become part of the creative design work for glass manufacturing. One can print color images directly to the glass surface by screen printing. In addition, it can also be used to temporarily cover the untouched part of the glass surface, or to print preservatives and other additives on a part of the surface of the glass, so that it is not affected by the etching or sanding process. In contrast, special inks can also be screen printed directly to create etched or matte finishes. sometimes. People can also use the strong hiding power of screen printing, such as printing a thin layer of conductive material on glass, to make anti-ice (frost) devices for windows.

Screen printing continues to expand in the field of flat glass decoration. In addition to its application to a variety of materials, printing materials, another important factor is that it can meet a wide range of different sizes, different weights of flat glass substrates. Moreover, due to the absolute superiority of screen printing in super-large-format image printing, it has further strengthened its leading position in the development of the entire flat glass printing industry. Especially in recent years, the demand for large-format flat glass printing has risen sharply. In fact, due to the rapid development of screen printing in the field of large-format flat glass decoration, printing equipment manufacturers are also constantly improving to meet more demanding printing requirements, especially in areas such as flat glass, resulting in many of the world's most flexible Equipment is widely used in the printing of building boards. The application of screen printing in flat glass decoration will continue to develop and it will continue to expand its applications in glass decoration. Screen printer has faster printing material transfer system, and more advanced power supply system, combined with powerful PLC (Logical controllable device)

In addition, the demand for glass screen printing technology in the automotive industry is also very strong In addition to the pure optical color application using screen printing, various functional layers (such as the heat conductor on the rear window) have also been modified conductive path and the most Good structures (such as rear window heaters) must be imprinted in a timely manner in a stable manner and ensure excellent quality.

Glass detection technology attracts attention

At this year's Shanghai Glass Fair, we noticed another prominent feature is that glass detection technology and equipment have received widespread attention, especially for some high-tech value-added glass screen printing products, such as LED, touch screen and The above-mentioned automotive glass, solar substrate, and the like. These products have strict requirements on quality and yield, so with the development of science and technology, more and more glass screen printing companies have begun to strictly monitor and control the quality of finished glass products, making glass inspection technology another hot topic in the glass industry. field.

What are the quality problems that often arise in the processing of glass screen printing technology?

Glass screen printing process is prone to problems

Paste version

1. The paste version, also known as plugging, refers to the phenomenon that the hole of the screen printing plate can not transfer ink to the printing material during printing. The appearance of this phenomenon will affect the printing quality, even if it is severe, it will not be able to print normally. The cause of the stencil phenomenon in the screen printing process is intricate. The reasons for squashing can be analyzed from the following aspects: 1 Causes of glass: The glass surface is not treated cleanly, and there are also watermarks, paper prints, mimeographs, fingerprints, dust particles, and other contaminants. Thus resulting in paste version; 2 workshop temperature, humidity and ink properties. Screen printing workshops are required to maintain a certain temperature of about 20°C and a relative humidity of about 50%. If the temperature is high and the relative humidity is low, the volatile solvents in the ink will evaporate quickly, and the viscosity of the ink on the screen will become high, thereby blocking the Live network. Another point that should be noted is that if the downtime is too long, it will produce a paste version phenomenon, the longer the paste version becomes more serious. Second, if the ambient temperature is low, poor ink flowability is also easy to produce paste; 3 screen printing reasons. The prepared screen plate can be used after being rinsed with water and dried before use. If you make a good version, do not print it too late. In the process of preservation, dust adheres more or less, and if it is not cleaned during printing, it will cause a paste. 4 reasons for printing pressure. Excessive embossing force during the printing process will cause the blade to bend. The blade is not in line contact with the screen plate and glass, but is in surface contact, so that each scratch can clean the ink and leave residual ink. After a certain period of time, the conjunctiva will cause a paste. 5 Reasons for improper clearance between screen plate and glass. The gap between the screen printing plate and the glass should not be too small. When the gap is too small, the screen plate cannot be detached from the glass in time after the squeegee is printed. When the screen plate is lifted, a certain ink is stuck on the bottom of the printing plate, which is easy to cause paste. board. 6 The reason for the ink is that when the pigment and other solid particles in the screen printing ink are large, the phenomenon of blocking the mesh hole is likely to occur. In addition, the mesh size and through-hole area of ​​the selected mesh are smaller than those of the ink, so that it is one of the reasons why the coarse-grained ink does not easily pass through the mesh. For stencils caused by large particles of ink, it is possible to solve the problems when manufacturing the ink. The main method is to strictly control the fineness of the ink.

In the printing process, the increase in ink viscosity caused by paste version, the main reason is that the screen printing ink solvent evaporation, resulting in increased ink viscosity, and closure of the network phenomenon. If the area for printing graphics is large, the ink on the screen printing plate will consume more, and the stencil printing will be less. If the picture area is small, the ink consumption on the screen printing plate is small, it is easy to cause paste printing. The countermeasure is to use a small amount of ink refilling principle. Poor flow of ink will cause the ink to produce a paste when not passed through the screen. This can be solved by lowering the viscosity of the ink and improving the fluidity of the ink without affecting the print quality. After a paste failure occurs, an appropriate solvent scrub can be used depending on the nature of the ink on the plate. The method of scrubbing starts from the printing surface and gently wipes from the center to the periphery. Check the plate after wiping, if any defects should be promptly repaired, and re-start printing after repair. It should be noted that the plate is thinned each time it is scrubbed, and if it is wiped out, it causes a major defect in the plate. 2. Insufficient fixation of ink on glass When printing on glass, it is important that the glass is subjected to strict degreasing and pre-treatment checks before printing. When the surface of the glass adheres to substances such as greases, binders, and dust, poor adhesion between the ink and the glass can result. 2 Insufficient adhesion of the ink itself causes the ink film to be stuck firmly. It is better to replace other inks for printing. Improper use of dilute solvent can also cause the phenomenon of ink film not adhered firmly. When selecting the dilution solvent, the nature of the ink should be taken into account to avoid the occurrence of the phenomenon that the ink and the substrate are not firmly bonded. 3. The uneven ink film thickness varies due to a variety of causes. In terms of ink, the ink is poorly formulated, or the normally formulated ink is mixed with ink. When printing, the solvent expands and softens due to the effect of the solvent. The ink-permeable mesh plugs up and acts as a plate, preventing the ink from passing through. In order to prevent such failures, the formulated ink (especially the old ink) should be screen-filtered before use. When you reuse a used plate, you must completely remove the old ink that has adhered to the plate. When the plates are stored after printing, they must be fully washed (including scrapers). If the tip of the ink return plate is damaged, a trace will appear along the direction of movement of the squeegee. When printing glass, there will be obvious ink inconsistencies. Therefore, it is necessary to protect the front end of the squeegee so as not to cause damage. If it is damaged, it must be grinded with a grinder. In addition, the unevenness of the printing table also affects the uniform ink. The convex ink layer is thin, and the recessed ink layer is thick. This phenomenon is also called ink inhomogeneity. In addition, if the back surface of the substrate or the printing table adheres with dust, the above failure may occur.

Pinhole phenomenon

The phenomenon of pinholes is the biggest headache for workers engaged in glass screen printing. The reasons for the occurrence of pinholes are also varied, many of which are currently unexplained, and some are still problems of quality management. Pinholes are one of the most important inspection items in the inspection of printed products. 1 Dust and foreign objects attached to the plate. At the time of plate making, there are some sols mixed into the water wash image. In addition, when the emulsion is applied, dust may be mixed in, and pinholes may be formed on the screen. These tests can be found and repaired promptly if they are checked. If dust and foreign matter adhere to the screen, blocking the screen openings can also cause pinholes. Before the formal printing, carefully check the screen plate and eliminate the dirt on the plate; 2. Clean the glass surface. Before printing, the glass plate should be pre-treated to make its surface clean and printed immediately. If the glass is processed, it will not be printed immediately and it will be recontaminated. After pre-treatment, dirt such as grease can be removed, and dust attached to the surface can also be removed. Pay special attention to the fact that the fingerprints of the hand will also adhere to the printed surface when the glass is moved by hand, forming pinholes during printing.

Bubbles appear

Bubble glass bubbles appear on the ink after printing. The main reasons for the bubbles are as follows: 1 The substrate is poorly processed before printing. Substrate surface attached to dust and oil traces and other substances; 2 ink bubbles. In order to adjust the ink, adding solvents and additives to stir, the ink will be mixed with some bubbles, if placed regardless of the low viscosity of the ink will naturally deaeration, high viscosity inks and some can not be natural deaeration. Some of these bubbles are naturally eliminated in the printing process due to the transfer of ink, while others become larger and larger. In order to remove these bubbles, defoamers should be used. The amount of defoamer added in the ink is generally about 0.1 to 1%. If it exceeds the prescribed amount, it will have a foaming effect. After the ink is transferred, even if it is foamed, as long as the wettability of the substrate and the ink flowability are good, the bubbles on the surface of the printing ink film will be gradually eliminated, and the ink forms a flat printing ink film. If ink bubbles are not eliminated, the ink film will form a ring-shaped uneven film surface. Bubbles in general inks can also be degassed due to the action of the screen when they pass through the screen. 3 Bubbles can also occur if the printing speed is too fast or the printing speed is uneven. The printing speed should be properly reduced to maintain the uniformity of the printing speed. 6. Electrostatic fault electrostatic current is generally small, the potential difference is very large, and there may be attracted, repelled, conductive, discharge and other phenomena. 1 adverse effects on screen printing. In the screen during printing, the rubber portion and the screen are charged by the pressure scraping of the blade rubber. The screen itself is charged, it will affect the normal ink, resulting in blockage failure; it will be absorbed by the screen at the moment of the output of the substrate; 2 methods to prevent static electricity. The methods for preventing static electricity generation include: adjusting the ambient temperature and increasing the air humidity; the appropriate temperature is generally about 20° C. and the relative humidity is about 60%; static electricity can be transferred in the wet air; the net pitch is reduced, and the printing speed is reduced.

Print size expansion

The main reason for the increase in printing size is the relatively low viscosity of the ink and excessive fluidity; the size of the screen printing plate is also the cause of the increase in the printing size. In order to avoid the ink flowability caused by the overflow of the ink after printing, causing the print size becomes larger, consider increasing the viscosity of the ink to reduce the ink's fluidity. When making screen printing plates, we must strictly guarantee the quality of screen printing plates and ensure the screen plate tension. 8. Part of the ink leaked from the printing plate of the printing plate is called ink leakage failure. The reason is: a part of the squeegee is damaged; the pressure of the squeegee is large; the gap between the plate and the glass is too large; the plate frame is deformed to a large extent; Insufficient printing pressure: ink is not uniform; the screen is too thin; printing speed is too fast. If dust is mixed on the glass and in the ink and printing is performed without processing, the plate will be damaged due to the pressure of the squeegee; when the plate is under-exposed, pinholes, etc., will cause ink leakage in the plate. At this time, adhesive tapes, etc. can be used for emergency handling from the back of the plate. If this operation is not very fast, the ink on the layout will be dried, and the whole of the plate will have to be wiped with solvent. Wipe plates are also the cause of delamination of the plate, so it is best avoided. The ink leakage of the printing plate often occurs in the ink staying part, so it is better to strengthen this part in the plate making.

Graphical and dark parts appear spotted

Moist ink refers to dot-like blots on graphic and dark areas of the glass surface. This phenomenon damages the printing effect. Glass screen printing is easy and this phenomenon occurs. The reasons are as follows: printing speed and ink drying are too slow; ink layer is too thin; ink thixotropic; electrostatic effects; Dot blots. The improved methods are: improving the fluidity of the ink; using a quick-drying flux; printing with a high-viscosity ink as much as possible: increasing the wet film thickness of the ink, using an ink made of a pigment with a small oil absorption amount as much as possible: minimizing the influence of static electricity . 10. When the image is deformed and printed, the pressure applied by the squeegee to the plate can make the line contact between the plate and the object to be printed. It should not exceed. If the printing pressure is too high, the printing plate contacts with the printing material and the screen may expand and contract, causing the printing image to be deformed. Screen printing is the smallest type of printing in various printing methods. If we forget this, we cannot print good prints. If the pressure cannot be printed without increasing the pressure, the gap between the plate surface and the glass surface should be reduced, so that the pressure of the blade can be reduced.

Conclusion

At present, the glass screen printing technology is shifting to high-tech, high-tech value-added processing areas. Including previously mentioned touch screens, liquid crystal substrates, solar photovoltaic substrates and other products have gradually become an integral part of the current electronic information products. It is believed that with the passage of time, glass screen printing technology will provide more support for the glass industry and even electronics, construction, energy and other fields.

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