Binder

In screen printing, binder, or adhesive, is an important component of screen printing ink or paste. The following is a detailed introduction to it:

Function:
Bonding effect: It can bond various solid particles such as pigments and fillers in screen printing inks or pastes together, and after printing, make these components firmly adhere to the surface of the substrate to form a complete film layer, preventing problems such as peeling and cracking during use, thereby improving the durability and stability of the printed matter.
The properties and amount of binder have a significant impact on the appearance and performance of printed materials, such as gloss, adhesion, wear resistance, and solvent resistance. Different Binders can endow printed materials with different surface characteristics to meet various application requirements. For instance, some special Binders can endow printed materials with different visual effects such as high gloss, low gloss or matte, and can also enhance the wear resistance, water resistance, oil resistance and other properties of printed materials.
Provide film-forming performance: During the drying process of ink or paste, the binder can form a continuous film, giving the printed matter a good visual effect and protective function. The quality of its film-forming performance is directly related to the quality and service life of the printed matter. A good binder should have excellent film-forming properties and be able to form uniform, dense and defect-free film layers on the surface of different substrates.

Classification:
Natural resin types: such as shellac, gum Arabic, etc. Shellac has good adhesion and durability, but its solubility in alcohol solvents is poor. Gum Arabic is widely available and inexpensive, but its adhesive force is relatively weak. It is mainly used in water-based screen printing inks.
Synthetic resin types: including acrylic resin, polyester resin, epoxy resin, polyurethane resin, etc. Acrylic resin has excellent weather resistance, solvent resistance and adhesion. It is soluble in a variety of organic solvents and suitable for various substrates. Polyester resin has good heat resistance, but its flexibility is slightly poor. Epoxy resin has strong adhesion and good chemical corrosion resistance, but it needs to be used in combination with a curing agent. Polyurethane resin combines excellent wear resistance, cold resistance and oil resistance, and has good elasticity, allowing its performance to be adjusted as needed.
Rubber products: such as natural rubber, nitrile rubber, etc. Natural rubber has good elasticity but poor aging resistance. Nitrile rubber has good oil resistance and wear resistance, and is often used for some special printing purposes, such as the printing of signs and patterns with high requirements for oil resistance.

Characteristics:
Viscosity: The viscosity of the binder affects the fluidity of the ink or paste, thereby influencing the smooth progress of the printing process. High-viscosity Binders help maintain the clarity and accuracy of printed patterns, but they require greater pressure during printing. Low-viscosity Binders are conducive to the flow and filling of ink, but problems such as uneven edges may occur when printing fine patterns.
Drying speed: Different Binders have different drying speeds. In screen printing, the appropriate drying speed should be selected based on the substrate and printing requirements. Quick-drying binder can enhance production efficiency, but it may cause the ink to dry on the screen, thereby affecting the printing effect. Slow-drying Binders can offer longer printability, but they require subsequent drying treatment.
Flexibility: To adapt to different materials of substrates and the usage environment of printed products, the binder needs to have a certain degree of flexibility. For some printed materials that need to be bent, folded or stretched, such as textiles and flexible packaging, using a binder with good flexibility can prevent the printed layer from cracking or peeling off.

Application:
In the electronics industry, in the production of electronic components, such as circuit boards and solar cells, conductive silver pastes containing specific Binders and other pastes are used in screen printing to achieve the printing and connection of conductive circuits, ensuring the electrical conductivity and reliability of electronic components. For instance, during the manufacturing process of printed circuit boards, the binder in the conductive silver paste can bond conductive particles such as silver powder together and firmly attach them to the circuit board substrate, forming a stable conductive circuit.
The glass and ceramic industry: In the screen printing inks used for glass and ceramics, the binder needs to have good heat resistance and adhesion. Because the firing temperature of glass and ceramics is relatively high, the printed ink must be able to firmly bond with the substrate at high temperatures while maintaining its decorative effect and functionality, such as the colored patterns and logos printed on glass products. Common ones, such as Binders in glass glazes, can form a good bond with the glass surface during the glass sintering process, ensuring that the patterns firmly adhere to the glass and maintaining bright colors and intact patterns during use.
Textile printing: In textile screen printing, the selection of binder should take into account its affinity and compatibility with fibers, so that the printed pattern can firmly adhere to the textile and have good hand feel and water wash resistance and other properties. For instance, the binder in reactive dye inks can form chemical bonds with fibers, endowing the patterns with high fastness and vividness on textiles. The binder in coatings and inks mainly adheres the pigment particles to the fiber surface through physical adsorption.
In the metal processing industry, for screen printing on metal surfaces, such as metal signs and metal handicrafts, the binder needs to be able to resist oxidation and corrosion on the metal surface, and have good wear resistance and weather resistance to ensure that the printed patterns do not fade or wear out during long-term use. For instance, in the printing of metal signs, the ink binder used can form a strong bond with the metal surface and withstand the erosion of the external environment, ensuring that the patterns and text on the sign remain clear and aesthetically pleasing at all times.