Glass Screen Printing Technology and Common Problems Analysis
From the traditional glass screen printing to the emerging LED, touch panel printing, screen printing technology runs through the entire glass industry, and in which play a decisive role.
So as one of the important areas in the screen printing industry, glass screen printing in the screen printing industry, what kind of important role?
First, the glass screen printing technology profile
Glass screen printing, is the use of screen printing plate, the use of glass glaze, decorative decorative glass products. Glass glaze, also known as glass ink, glass printing material, which is made from the coloring material, mixing material made of paste printed material. Coloring materials from inorganic pigments, low melting point flux (lead glass powder) composition; commonly known in the glass screen printing industry as a plate oil. After the printing of glass products, to set the stove, to 520 ~ 600 ℃ temperature firing, glaze printed on the glass surface can be consolidated in the glass, forming a colorful decorative patterns. If the silk screen with other processing methods used, it will be more desirable results. For example, the use of polishing, engraving, etching and other methods before or after printing on the glass surface processing, can double to improve the printing effect.
Second, the application of glass screen printing technology
Screen printing plate glass applications and market prospects Screen printing plate glass is widely used in every corner of the people's lives: you can easily find the showcase, the building space partition, building landscaping, car windshield and mosaic glass and other places Their figure. Simultaneously. They are also widely used in furniture decoration and game tools, as well as countless decorative and artistic creation. Screen printing has also become a part of creative design for glassmaking. One can print color images directly to the glass surface by screen printing. It can also be used to temporarily cover the non-graphic part of the glass surface or to print a preservative and other additives in parts of the surface of the glass to protect it from etching or frosting. In contrast, special inks can be directly screen-printed to create an etch or matte finish. sometimes. People also rely on the strong ability to cover screen printing, such as the glass printed with a thin layer of conductive material used to make windows anti-icing (frost) device.
Screen printing in the field of flat glass decoration continues to expand. In addition to its suitable for a variety of materials, printing materials, the other important factor is that it can meet a wide range of different sizes, different weights of flat glass substrates. Moreover, due to the absolute advantage of screen printing in VLF printing, it further strengthens the dominance it leads the development of the flat glass printing industry. In particular, the demand for large format flat glass printing has risen sharply in recent years. In fact, due to the rapid development of screen printing in the area of large-format flat glass decoration, printing equipment manufacturers are also constantly improving to meet the increasingly demanding printing requirements, especially in the field of flat glass, etc., resulting in many of the most flexible Equipment is widely used in construction printing plate. Screen printing in the flat glass decorative applications will continue to develop and continuously expand its application in the field of glass decoration. Screen printer has a faster delivery system of printing materials, as well as more advanced power supply system, combined with powerful PLC (logic controllable device)
In addition, the demand for glass screen printing technology in the automotive industry is also very strong. In addition to pure optical color applications using screen printing, various functional layers (such as the thermal conductor on the rear window) are also modified for conductor paths and most Good structures such as the rear window heating must be stamped in a stable manner in time and with excellent quality.
Third, the glass screen printing process prone to problems
So glass screen printing technology, the process of which often appear quality problems?
1, paste version
Paste version also known as plug version, refers to the screen printing plate graphic through part of the hole in the printing ink can not be transferred to the substrate on the phenomenon. The appearance of this phenomenon will affect the printing quality, even in severe cases will not be able to print normally. The reason for the paste-plate phenomenon in the screen printing process is complicated. Paste version of the reason can be analyzed from the following aspects:
① glass reason: the glass surface is not handled clean, there are still watermarks, paper, offset, fingerprints, dust particles and other dirt. Thus resulting in paste version;
② workshop temperature, humidity and ink properties of the reasons. Screen printing workshop requires the maintenance of a certain temperature of about 20 ℃ and relative humidity of about 50%, if the temperature is high, the relative humidity is low, the volatile solvent in the ink will evaporate quickly, the viscosity of the ink on the screen becomes high, Live cell Another point should be noted is that if the downtime is too long, there will be paste-like phenomenon, the longer the more serious paste. Second, if the ambient temperature is low, poor ink flow is also prone to paste version;
③ screen printing plate reasons. Make a good screen printing plate before use, rinse with water and dry before use. If a good version of the system placed too long after the printing. More or less in the preservation process will be attached to the dust, printing, if not cleaned, it will result in paste version.
④ printing pressure reasons. Imprinting force is too large during printing, will make the scraper bending, scraper and screen printing plate and the glass is not in line contact, and the surface contact, so that each scratch can scratch the ink clean, leaving the residual ink , After a certain period of time will result in conjunctival paste version.
⑤ screen printing plate and glass gap reason. Screen printing plate and the gap between the glass can not be too small, the gap is too small Screen after scraping the screen can not be timely from the glass, screen printing plate raised, the bottom of the plate sticky ink, it is also easy to paste board. ⑥ ink reasons, in the screen printing ink pigment and other solid particles larger, it is easy to block the phenomenon of mesh. In addition, the choice of screen mesh and through-hole area and the ink particle size is smaller, so that the coarser particles of ink is not easy to seal through the mesh phenomenon is also one of the reasons. Due to the large particles of ink caused by the paste, you can start from the manufacture of ink, the main method is to strictly control the fineness of the ink.
In the printing process, the viscosity of the ink caused by paste, the main reason is that the ink on the screen printing plate evaporation solvent, resulting in increased viscosity of the ink, and the occurrence of net phenomenon. If the printing graphic area is relatively large, screen printing ink consumption on the plate, the paste version of the phenomenon less. If the graphic area is small, less consumption of ink on the screen printing plate, it is easy to cause paste version, the countermeasure is to use a small amount of ink several times the principle. The poor fluidity of the ink causes the ink to produce a paste when it is not passed through the screen. This can be done by reducing the viscosity of the ink and improving the ink's flowability without affecting the print quality. Paste version of the fault occurs, you can print on the nature of the ink, using a suitable solvent scrub. Scrub the essentials is from the printing surface, gently wipe the middle to the periphery. Check the plate after wiping, if defects should be promptly repaired, repaired after the resumption of printing. It should be noted that each version of the membrane scrub, it thinner, such as wiping the membrane caused a major defect, had to change the new printing.
2, ink is not firmly fixed on the glass
① When printing on glass, it is very important that the glass undergo strict degreasing and pre-treatment inspection before printing. When the glass surface attached to grease, adhesives, dust and other substances, it will result in poor adhesion of ink and glass. ② ink itself is not enough adhesion caused by sticking ink film is not strong, it is best to replace other types of ink for printing. Dilution of solvent improper use of ink film adhesion may appear not strong phenomenon, the choice of diluted solvent to consider the nature of the ink, in order to avoid the phenomenon of ink and substrate adhesion is not strong.
3, uneven ink
Ink film thickness unevenness, because a variety of ink in terms of bad ink deployment, or the normal deployment of the ink mixed with the ink, printing, due to the role of solvent expansion, softening, will be through the ink Mesh blocked, played a role of version of the film, so that ink can not be passed. In order to prevent this failure, the deployment of ink (especially the old ink), before use net filter once again re-use. When reusing a used printing plate, the old ink attached to the plate must be completely removed. After printing plate storage, to be fully washed (also including scraper). If there is any damage to the tip of the front plate, a trace will appear along the direction of movement of the squeegee. In the printing of glass, there will be obvious uneven ink. Therefore, the front end of the scraper must be well protected from damage, and if it is damaged, it must be carefully ground with a grinder. In addition, the unevenness of the printing station also affects the ink uniformity. Convex thin ink layer, concave ink layer thickness, this phenomenon is also known as uneven ink. In addition, the back of the substrate or printing station sticky dust, it will have the above failure.
4, pinhole phenomenon
Pinhole phenomenon for the staff engaged in glass screen printing, is the most troublesome problem. The causes of pinholes are also varied, many of which are unexplained primitives, and some of which are quality management issues. Pinhole is one of the most important inspection items in printing product inspection. ① attached to the version of the dust and foreign body. Plate making, washing and developing will have some sol mixed into it. In addition, when the emulsion coating, but also mixed with dust, attached to the screen will produce pinholes. These in the test, if you check the words, you can find and make timely repairs. If the dust and foreign objects attached to the screen, plug the screen openings can cause pinholes. Before the official printing, we must carefully check the screen, to eliminate the dirt on the plate; ② glass surface cleaning. Glass before printing should be pre-treatment to make its surface clean, immediately printing. Such as glass after treatment, do not print immediately, will be polluted again. After pretreatment, grease and other dirt can be removed, at the same time, can also remove the dust attached to the surface. Pay special attention to the hand when moving the glass, the fingerprints will be attached to the printing surface, the formation of pinholes when printing.
5, there bubble
Bubble glass bubbles in the print sometimes appear on the bubble, the bubble generated by the following main reasons: ① substrates pre-press treatment is not good. Substrate attached to the surface of the dust and traces of oil and other substances; ② bubbles in the ink. To adjust the ink, add solvent, additives, stirring, the ink will be mixed with some bubbles, if left in place, low viscosity of the ink will naturally degassing, high viscosity of the ink, while some are not natural degassing. Some of these bubbles in the printing, due to the transfer of ink and natural elimination, but some have become more and more. In order to remove these bubbles, the defoaming agent is used. The amount of the defoaming agent in the ink is generally about 0.1 to 1%. If the defoaming agent is used in excess of the specified amount, the defoaming agent may play a role of foaming. Even after the ink foam transfer, as long as the wettability of the substrate and the ink flow well, the printing ink film on the surface of the bubble will gradually eliminate the ink to form a flat printing ink film. If the ink bubble is not eliminated, the ink film will form a ring-shaped uneven surface. Bubbles in general ink through the screen, but also because of the role of the screen can be defoaming; ③ printing speed too fast or uneven printing speed will produce bubbles. Should be appropriate to reduce the printing speed, printing speed to maintain the uniformity.
6, static electricity failure
Electrostatic current is generally small, the potential difference is very large, together there may be attractive, repellent, conductive, discharge and so on. ① to screen printing adverse effects. Screen printing, due to squeegee squeegee rubber scraping the rubber part and the screen charged. Screen itself charged, will affect the normal inking, blocking version of the failure; in the moment of printing substrates will be sucked wire; ② prevent static methods. Methods to prevent static electricity are: adjust the ambient temperature, increase the air humidity, the appropriate temperature is generally about 20 ℃, relative humidity of about 60%; static electricity can be passed in the wet air; reduce the network distance and reduce the printing speed.
7, printing size expansion
Printing size is mainly due to the expansion of the ink is relatively low viscosity and fluidity is too large; screen printing plate in the production of the size of the expansion, also contributed to the expansion of the print size reasons. In order to avoid excessive ink flow caused by the ink after printing spill around, resulting in larger print size, consider increasing the viscosity of ink to reduce the mobility of the ink. In the production of screen printing plate, we must strictly guarantee the quality of the screen version to ensure the tension of the screen.
8, printing plate leak ink
Part of the membrane leakage of ink, known as leakage of ink failure, the reason is: a part of the scraper injury; scraping ink pressure; plate and the gap between the glass is too large; large deformation box, the local pressure is not enough: Uneven ink; screen too thin; printing speed too fast. If the glass and ink mixed with dust, without processing on the printing, then because of squeegee pressure will make the film damage; plate exposure underexposed pinholes, etc., will make the film leak ink phenomenon. At this time, available tape from the back of the plate affixed to do emergency handling. If this operation is not very fast, it will make the layout of the ink dry, had to wipe the whole version of the solvent. Wipe version is also the reason leading to release of the film, it is best to avoid. Version of the ink leakage in the ink part of the stay, so it is best to strengthen this part of the plate.
9, part of the text and shadow spots appear spotted
Ink refers to the glass surface of the graphic part and dark spots appear spot-like imprint, this phenomenon undermines the printing effect. Glass screen printing is easy, resulting in this phenomenon. The reasons are as follows: printing speed and ink drying too slow; too thin ink layer; ink thixotropy large; static electricity; ink pigment poorly dispersed, due to the role of pigment particles, the particles aggregate each other, there color Dot blotting. Improved methods are: to improve the fluidity of the ink; the use of fast-drying flux; as far as possible with high viscosity ink printing: increase the wet film thickness of the ink, try to use a small amount of oil-based paint made of ink: to minimize the impact of static electricity .
10, the image deformation
Printing by scraper added to the plate on the printing pressure, printing plate can be printed material line contact between the can, not more than. Printing pressure is too large, plate and substrate contact inside, will make the screen stretching, resulting in deformation of the printing image. Screen printing is the smallest of all kinds of printing in India, a printing, if we forget that this is not printed good prints come. If not increase the pressure can not be printed, should narrow the gap between the layout and the glass surface, so the pressure of the squeegee can be reduced.
At present, the glass screen printing technology is toward high-tech, high-tech value-added processing areas change. Including the aforementioned touch screen, LCD substrates, solar photovoltaic substrates and other products have gradually become nowadays an integral part of electronic information products. Believe 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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