Glass screen printing has been widely used in China, due to the wide variety of ink on the market, the glass matrix also has its diversity, the printing process often has some problems. The following is a summary of the problems in the process of glass screen printing, and the solution to the problem of glass screen printing.
First, paste plate:
Paste plate, also known as blocking plate, refers to the phenomenon that the through hole part of the screen plate can not transfer the ink to the substrate in the printing. The appearance of this phenomenon will affect the printing quality, and even the normal printing will not be possible in serious cases. The reasons for the phenomenon of pasting produced in the process of screen printing are complicated. The reasons for paste can be analyzed from the following aspects:
(1) The reason for the glass: the glass surface is not treated clean, and there are watermarks, paper prints, mimeograph prints, handprints, dust particles and other dirt. Thus resulting in paste plate;
(2) Reasons for workshop temperature, humidity and ink properties. Screen printing workshop requires to maintain a certain temperature of about 20 ° C and relative humidity of about 50%, if the temperature is high, the relative humidity is low, the volatile solvent in the ink will quickly evaporate, the viscosity of the ink on the screen becomes high, thus blocking the mesh.
(3) The reason for the screen printing plate. The finished screen plate can be used after rinsing with water and drying before use. If it is placed too long after making a good version, it is not printed in time. In the preservation process more or less will adhere to the dust, if not cleaned when printing, it will cause paste.
(4) The cause of printing pressure. During the printing process, the printing force is too large, which will bend the scraper, and the scraper is not in line contact with the screen printing plate and the glass, but is in surface contact, so that each scraping can scrape the ink clean, leaving the residual ink, and after a certain time, the conjunctiva will cause the paste plate.
(5) The reason for improper gap between the screen plate and the glass. The gap between the screen plate and the glass can not be too small, the gap is too small after scraping the screen plate can not be timely out of the glass, when the screen plate is lifted, the bottom of the plate is glued to a certain ink, which is also easy to cause paste board.
(6) The reason for the ink, in the printing process, the ink viscosity increases resulting in paste plate, because the ink solvent on the screen plate evaporates, resulting in increased ink viscosity, and the phenomenon of sealing the screen. The second is the fluidity of the ink, poor fluidity will make the ink in the screen when it does not produce paste.
Second, pinhole phenomenon
The pinhole phenomenon is the most headache for the staff engaged in glass screen printing. Pinholes occur for a variety of reasons, many of which are currently unexplained, and pinholes are one of the most important inspection items in the inspection of printed products. The causes of pinhole phenomenon are:
(1) Dust and foreign matter on the plate. When making plates, some sol will be mixed into the washing development. If dust and foreign matter are attached to the screen plate, blocking the screen plate opening will also cause pinhole phenomenon. Before the formal printing, to carefully check the screen plate, eliminate the dirt on the plate;
(2) The glass surface is not cleaned. The glass plate should be pre-treated before printing to make its surface clean and printed immediately. Pay special attention to when moving the glass by hand, the fingerprint of the hand will also be attached to the printing surface, and the pinhole will be formed when printing. The main reason for the emergence of bubbles is that the printing material is poorly treated before printing, which may be caused by substances such as dust and oil stains attached to the surface of the substrate, or by bubbles in the ink.
(3) Too fast or uneven printing speed will also produce bubbles. The printing speed should be properly reduced to maintain the uniformity of the printing speed.
Three, the graphic part and the dark part appear speckled
Ink refers to the appearance of blotchy marks on the graphic part and the dark part of the glass surface, which damages the printing effect. Glass screen printing is easy, resulting in this phenomenon.
(1) Printing speed and ink drying is too slow
(2) The ink layer is too thin and the ink thixotropy is large
(3) The influence of static electricity
The pigment dispersion in the ink is poor, because of the polarity of the pigment particles, the particles agglutinate with each other, and the color blotches appear.
Improved method
1. Improve ink fluidity
2. Use a quick-drying flux
3. As far as possible, use high viscosity ink printing, increase the thickness of the wet film of the ink, and try to use ink made of pigments with small oil absorption to minimize static
The effect of electricity.
4. When the image is deformed, the printing pressure added to the printing plate by the scraper can make the line contact between the printing plate and the printed object, and do not exceed. Printing pressure is too large, the plate and the substrate inside contact, will make the screen telescopic, resulting in deformation of the printed image. Screen printing is a kind of printing with the smallest printing pressure in various printing methods. If the pressure cannot be printed without increasing the pressure, the gap between the plate and the glass surface should be reduced, so that the pressure of the scraper can be reduced.
