In the production process of LCD assembly, adhesive is one of the key materials. Efficient production rhythm requires the use of adhesives with better performance and faster curing. Therefore, UV UV-curable adhesives are widely used to assemble LCDs. In the manufacturing process of LCDs, there are five parts that need to be assembled with UV-curable adhesives: temporary positioning of optoelectronic components, sealing of the motherboard, sealing of metal lead terminals, flexible sealing, assembly of bare chips, and assembly of protective coatings.

1. Temporary Positioning of Optoelectronic Components

The positioning of the upper and lower glass layers is the most important step in the assembly process of the LCD. When using a thermosetting epoxy adhesive to seal the motherboard, a uv adhesive can be used to position the two glasses. This uv-curing adhesive must be able to soften when heated and be removed when cutting and trimming individual LCDs.

2. Motherboard Sealing

Main board sealing is the bonding and sealing together of two glass substrates with a defined gap to confine the liquid crystal material in the two glass interlayers. Because liquid crystal is a highly reactive solvent, it requires a high adhesive for sealing liquid crystal. In addition to high bonding strength to glass, indium oxide, tin oxide, and polyimide, it should also have good moisture and heat resistance, otherwise there will be image stains, reduced contrast, increased power consumption, liquid crystal bubbles and even glass peeling.

3. End Sealing

After sealing the motherboard, it leaves a liquid crystal filling port from which liquid crystal material can be injected by vacuum infusion method and finally sealed with adhesive. Epoxy adhesives have been used as sealing adhesives, due to the slow curing of epoxy adhesives and long contact time with the liquid crystal before curing, it is easy to penetrate the liquid crystal material. The new LCD is very sensitive to foreign matter, the migration of foreign matter will directly lead to program confusion and bring losses to the manufacturer. UV curing adhesive is suitable for liquid crystal sealing, short curing time (a few seconds to tens of seconds), can reduce the direct contact time between liquid crystal and UV adhesive before curing, and effectively prevent liquid crystal migration into the adhesive. UV adhesive for sealing ends requires low viscosity for easy application; after all, the purity is high and the uncured adhesive will come into contact with the liquid crystal.

4. Soldering of Metal Lead Terminals

The metal lead terminal is soldered by jamming the metal pin into the glass and coating it with UV adhesive. This bonding, although not as strict as the above requirements for direct contact between the adhesive and liquid crystal materials, but requires a moderate adhesive viscosity, after coating, not flowing, UV curing, good surface dryness, good electrical insulation, and glass, metal bonding strength, excellent resistance to moisture and heat aging performance.

5. Flexible Sealing

Flexible sealing refers to the two ends of the LCD through the flexible wire or ribbon wire and drive integrated circuit connection, easy to cause interference due to dust or humidity, the two ends of the interface should be protected by sealant. UV-curable adhesive used for flexible sealing end should have low viscosity, easy to flow into the protected area, good adhesion, high purity and no pollution.

6. Bare Chip Assembly

Several flip chip (FCOG) technologies have been developed to bond integrated circuit chips directly to the glass backing of LCDs. This assembly is done with UV-curable adhesives, requiring UV-curable adhesives to the glass and bare IC chips have excellent adhesion and low water absorption, especially UV-curable adhesives to have a high purity and very low ionic content.

7. FCOG Coating

In the assembly of high-grade LCDs, FCOG technology for flip glass is widely used, but flip glass chips need protective coatings, usually using solvent coatings. Currently, UV-curable protective adhesives are more widely used for environmental protection, safety and production efficiency. Because bare chips are more susceptible to external interference, the requirements for uv-curable sealants are more stringent than those for flexible terminals.