Screen Printing
Screen printing has strong adaptability: Offset, relief, and intaglio printing methods can generally only be used on flat substrates. However, screen printing can be used not only on flat surfaces but also on curved, spherical, and irregular surfaces. Furthermore, screen printing can be applied to both hard and soft substrates, without being limited by the texture of the substrate. In addition to direct printing, screen printing can also be used for indirect printing as needed, by first screen printing onto gelatin or silicone plates, and then transferring it to the substrate. Therefore, screen printing has strong adaptability and a wide range of applications.
Strong three-dimensional effect: The ink layer thickness of conventional offset and relief printing is generally around 5 microns, while intaglio printing is around 12 microns, and flexographic printing (aniline) is 10 microns. However, the ink layer thickness of screen printing far exceeds the thickness of these ink layers, generally reaching around 30 microns. Thick screen printing ink layers result in rich texture and a strong three-dimensional effect, which other printing methods cannot compare with. Screen printing can not only print in single color but also perform color overlay and halftone color printing.
Strong light resistance: Due to its porous nature, screen printing can use various inks and coatings. It can not only use paste, adhesives, and various pigments but also use coarser pigments. In addition, screen printing ink mixing is simple. For example, light-resistant pigments can be directly added to ink, which is another major feature of screen printing. Screen-printed products have the great advantage of strong light resistance. Practical tests have shown that, compared with the maximum density value range measured after one impression using black ink on copperplate paper, offset printing is 1.4, relief printing is 1.6, intaglio printing is 1.8, while the maximum density value range of screen printing can reach 2.0. Therefore, screen-printed products have stronger light resistance than other types of printed products and are more suitable for outdoor advertising and signage.
Large printing area: The maximum area size printed by conventional offset and relief printing methods is generally the full sheet size. Beyond the full sheet size, mechanical equipment limitations apply. However, screen printing can be used for large-area printing. Today, screen printing products can have a maximum size of up to 3 meters by 4 meters, or even larger.
The above four points are the differences between screen printing and other printing methods, as well as the characteristics and advantages of screen printing. Understanding the characteristics of screen printing allows for leveraging its strengths when choosing a printing method, achieving ideal printing results.
Screen printing usually comes in two forms: manual printing and mechanical printing.
Manual printing refers to the entire process from continuous paper to receiving paper, including moving the printing plate up and down, as well as squeegee printing, which are all manual operations.
Mechanical printing refers to the printing process being completed by mechanical actions. It can be further divided into semi-automatic and fully automatic printing, where semi-automatic means that substrate insertion and removal are manually operated, while printing is mechanically completed, and fully automatic means that the entire printing process is mechanically completed.
There is also a rapid and simple curved surface screen printing method called "direct surface screen printing," where the screen printing plate is removed and directly pressed against the substrate for printing. This method can be used to print a large number of processed products, such as latex plastic barrels, pure water buckets, basins, thermos bottles, cups, bowls, plates, and other products. This method can also be used to print signage on cars or print on irregular surfaces.
Preparation of direct surface screen: First, dry and repair the photosensitive text and graphics film, then remove it, and cut it to size. Use wooden or aluminum strips as frames to firmly attach them to the ends of the screen with adhesive tape or directly with adhesive. This creates the required direct surface screen. Operating method for direct surface screens: Depending on the substrate, different inks are prepared: firstly, using flat plates and dishes, prepare the ink, then one person holds the direct screen with both hands and presses it firmly against the substrate, while another person evenly coats the ink on the screen using the squeegee on the ink plate. After that, the squeegee is evenly placed on the plate to carry out uniform printing.
If the area to be printed is too large, ink can be poured onto the plate as needed, but care should be taken not to let the ink flow out of the substrate. Pay attention to the ink mixture not being too thin or too dry, and maintain moderate humidity. For small-area printing of text or graphics, one person can operate by tightly attaching one end of the direct screen to the substrate as needed, and then using the other hand to pull the screen tightly against the substrate for printing. When starting printing, always start lightly from the end where the tape is attached. If two people are operating, the same principle applies. This printing method is convenient to operate, flexible in substrate requirements, suitable for large and small quantities, and has the advantages of low cost and energy savings.