Production problems of foam pressure sensitive tape

Many enterprises at home and abroad began to try to develop better foam tape. For example, by adjusting the manufacturing process of foam, the foam with closed cell structure was produced. The foam tape produced by using this as the base material could reduce the intrusion of water vapor and dust. Or introduce some oligomers to improve the surface energy in the manufacture of polyurethane foam, so as to improve the surface energy of the foam, so as to reduce the cost of pretreatment when the foam is transferred to pressure sensitive adhesive layer. Although these two methods can improve the performance of foam tape, the closed cell structure of the former is only suitable for the application of large size devices.

Once the closed cell structure of small size devices is damaged in the die cutting process, there will still be a full pass situation. While the latter can only slightly improve the surface energy of foam, the manufacture of high viscosity foam tape still needs to be pretreatment. 3M adopted the solution of core material of viscoelastic body with very low crosslinked density and surface layer of viscoelastic body with high crosslinked density. By taking advantage of the high loss factor characteristic of core material under high-frequency shear, the external impact was converted into mechanical relaxation of core material, and in this way, the buffering performance similar to foam tape was obtained.

However, the buffering performance of this scheme is worse than that of the foam base material tape, which still needs the foam structure to reinforce. Prior art reports that expandable polymer microspheres are used in adhesives to obtain pressure sensitive film material by extrusion of die head, which is then laminated with the liner to form adhesive tape.

This method has the following drawbacks: (1) it is not possible to produce pressure sensitive adhesive tape with thinner thickness (less than 200 microns), so it is difficult to apply in ultra-thin Spaces; (2) Expandable polymer microspheres are only partially expanded before the adhesive composition is discharged from the die head, and can still continue to expand after being heated. In the bonding of electronic devices, there is a risk of device damage due to continued expansion; (3) The shell of the polymer microsphere is fixed after expansion.

The elasticity/compressibility of the eventually formed pressure-sensitive film material is limited by the mechanical strength of the microsphere shell. The elasticity of the microsphere needs to be changed by adjusting the material and thickness of the shell. (4) The production process of expandable polymer microspheres is complicated, the shell material has high mechanical strength, and needs high temperature above 100℃ to achieve expansion; (5) Using melt extrusion process manufacturing, feeding equipment is huge and complex, need more than 100℃ high temperature to achieve polymer microsphere expansion, high energy consumption, the process is more complicated. The aforementioned pressure-sensitive film is not suitable for today’s light and thin smart electronic products.