①Adhesive glue, adhesive tape
The most common structure of resistive and capacitive touch screens. As mentioned before, the touch screen unit is a laminate composed of various layers. The material of each layer is selected according to its purpose and use environment. For example, when robustness and transparency are required, glass can be selected; when lightweight, thin film, and low cost are required, PET film can be selected. The support body is required to be strong, so glass or polycarbonate are more choices, and adhesives are used to bond each layer. If it is placed under heating or warm conditions to bond different materials together, it will be affected by various thermal expansion or contraction phenomena, and problems will occur.
(I) Transparency, appearance
The touch screen is installed at the front end of the LCD or plasma screen, which will affect the screen display effect. Therefore, the materials and adhesives used in the touch screen must have good transparency. Acrylic-based adhesives are inherently transparent, but in order to find out the characteristics of the target substance, a tackifier is sometimes used. At this time, it is necessary to pay attention to the occurrence of coloring and turbidity. In addition, it is necessary to strengthen the management in the process in order to prevent the intrusion of foreign matter and the problem of sinking.
(2) Durability and reliability
Like LCD and plasma screens, touch screens are also used for various purposes, and they may also be placed in high temperature or low temperature, or even high temperature and high humidity environments. In such an environment, the adhesive cannot cause problems such as foaming and peeling.
•High temperature conditions
Under high temperature conditions, the adhesive is most prone to foaming. During installation, although foreign matter may be mixed in sometimes, in most cases fine bubbles are mixed in. It is not easy to see at room temperature, but it expands at high temperature and is very easy to see. For the fine air bubbles mixed in, the most effective treatment method is high pressure treatment. In addition, it is also possible to increase the cross-linking agent and increase the cohesive force to suppress foaming.
If polycarbonate is used on the substrate, unreacted substances and moisture mixed in the material may cause Out Gas, which may lead to defects such as bubbles and peeling. C. Improve the adhesion of the adhesive to the polycarbonate. The adhesive force to prevent such defects.
Another defect that occurs due to high temperature is curling. The reason for this is that various materials have different degrees of thermal expansion and contraction when they are bonded. When curling occurs, it is not only a problem of bending, but also peeling when it is severe. The effective solution is to improve the cohesive force of the adhesive and conduct strong bonding, just like suppressing the dimensional change of each material.
