A brief discussion on screen printing of glass（one）

Glass screen printing refers to the screen printing method used with glass plates or glass containers as the main products. The use of glass has a long history in my country. Even in modern times, glass still occupies an important position in our lives. Screen printing companies should rationally combine the actual situation of the company and the characteristics of the products to serve customers with the lowest production cost and the highest production efficiency. Under the current conditions of coexistence of opportunities and challenges, the application of screen printing on glass products is undoubtedly a very effective response measure, which can increase the market development efforts and open up a variety of marketing channels.

As a building decoration material, glass has the advantages of being flat and transparent, able to block wind and rain, and easy to scrub. Glass that has been screen-printed is more popular for indoor and outdoor decoration, which greatly meets people's life and aesthetic needs. Various beautiful patterns compete with each other, and are ingenious and ingenious. Now glass containers have begun to develop into medical supplies and industrial supplies. The high quality of glass products decorated with screen printing technology will become a new growth point for glass printing.

1. Screen printing process of glass

According to the principle of screen printing, the ink is printed on the surface of the glass, and then the ink curing measures are adopted, so that the printed pattern is firm and durable. The process flow is as follows:

Stretching the screen → sizing → drying → exposure → development → drying

↓

Flat glass → cutting → edge grinding → cleaning and drying → printing

↓

Sintering

1. Glass suitable for printing

Cut the glass according to the user's requirements, which can be regular or irregular shapes, and then grind the edges, clean, dry and standby. Special attention should be paid here that there should be no water marks on the glass surface.

2. Selection of screen

The screen printing plate used for glass printing is the same as the general screen printing plate. The glass screen printing plate uses synthetic fiber screen, stainless steel screen, and natural fiber screen. When printing general colorants, the above screens can be used, and generally cheap synthetic fiber screens are selected; when used as gold and silver decorations, stainless steel screens cannot be selected. The specifications of the screen are generally 270-300 mesh.

3. Selection of screen frame

At present, the more regular and less deformed screen frame is the aluminum alloy screen frame, which 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 screen frame. In addition, the strength of the screen frame is very important, and the key is that the horizontal rigidity is sufficient.

4. Stretch the screen

Choose the screen and the screen frame, and combine the two, this is the stretching of the screen. There are many ways to stretch the screen, which can be manual, motorized, and pneumatic. At present, the more advanced one that can stretch high-quality screens is the pneumatic stretching machine. The requirements for stretching the screen are uniform tension, the warp and weft of the screen are kept vertical, and the screen glue must be firm and not loose.

5. Choose photosensitive adhesive

Currently, the commercially available photosensitive adhesives are dichromate, diazonium, and iron salt. The requirements for photosensitive adhesives in screen printing are: good plate-making performance and easy coating. The photosensitive spectrum range is 340-440nm, with good development performance, high resolution, good stability, easy storage, economical and hygienic, non-toxic and pollution-free. The requirements for photosensitive materials in printing are: the plate film formed by the photosensitive material adapts to the performance requirements of different types of inks, has considerable printing resistance, and can withstand a considerable number of scraping pressures by the squeegee; it has good bonding with the screen, and does not produce film removal failure during printing; it is easy to peel off, which is conducive to the recycling of the screen plate material.

6. Plate Exposure

After selecting the above materials, apply the photosensitive glue in a dark room; it is required to be uniform and then dry, and generally requires two coats. Plate exposure requires exposure on a cold light source plate exposure machine, and the exposure time should be determined according to the pattern, generally between 12 and 30 minutes. After exposure and development, the screen printing plate is obtained.

7. Printing

There are several types of printing machines for flat glass: manual, semi-automatic, and fully automatic. Manual printing machines are suitable for small batches and small specifications of flat glass. Semi-automatic and fully automatic printing machines are suitable for large-scale, large-scale, multi-color printing, with the advantages of accuracy and speed. The largest semi-automatic printing machine can print glass with a size of 2000×1500mm. Fully automatic printing machines are generally used for printing car windshields. Several foreign companies can provide such equipment.

8. Ink

There are two types of inks for inorganic glass screen printing. One is that inorganic pigments are ground to a certain fineness. Then acrylic resin is added and screen printed on the glass surface. It needs to be baked at high temperature (above 600℃) for 1 to 2 minutes. The ink layer and the glass surface are melted together, and the fastness is excellent. The heat-resistant temperature of this ink is above 600℃. However, because this screen printing process is expensive and complicated, it is rarely used in the screen printing industry.

The other is inorganic glass ink with polymer compounds as binders. Both amino and epoxy types need to be baked, and the domestic market is wide. The ink used is baked at 1300-1 400℃ for 30 minutes after screen printing. The heat resistance temperature of this ink is relatively low. However, the baking time is long, the ink has good fastness and hardness, and the brightness is also very good. It can withstand the corrosion of low-concentration electrolytes and solvents such as ethanol, acetone, benzene, and cyclohexanone.

9. Sintering

Glass is an amorphous inorganic material. It softens with the increase of temperature. When the temperature of the glass is reached, the glass will deform. The glass glaze is decorated on the surface of the glass by silk screen printing. It needs to be solidified on the surface of the glass by high-temperature sintering, but the sintering temperature must be lower than the softening temperature of the decorated glass to ensure that the decorated glass does not deform. The sintering temperature of general glass glaze is not higher than 520℃, and is usually controlled at 480-520℃. There are several domestic manufacturers producing low-temperature glass glazes, and the price is also relatively low. Several foreign companies can also provide similar products, but the price is 10 to 20 times different from that of domestic products. Domestic consumption level has not yet reached the level of using this type of glaze, but the glaze provided by foreign countries is indeed much better than the domestic color and layering.

To improve the quality of decorative glass, it is inevitable to improve the grade of glaze. Sintering equipment includes flame furnace and resistance furnace. Resistance furnace is divided into vertical hanging type and horizontal roller type according to the hanging method of glass. Vertical hanging sintering furnace has the advantages of small sintering deformation and a yield rate of more than 95%, but the equipment is complicated. Horizontal roller type is prone to large deformation and low yield rate if it is not adjusted properly. In addition, it is also feasible to use horizontal tempering furnace to produce decorative glass. The grade of the product is improved and the safety is guaranteed. It is an ideal sintering method.