Preparation and Performance of Colorless, Transparent Polyimide Film(4)
(10) Non-toxic, having good bio-compatibility and a wide range of application in medical equipment.
For above excellent performance of PI and characteristics of the chemical synthesis and various processing methods, it is difficult to find such a wide range of applications such as PI, the PI are widely used:
(1) One of the earliest products, mainly used for flexible printed circuit board;
(2) Heat coating, as insulation paint for electromagnetic wire or as a high temperature resistant coating;
(3) Advanced composite materials for aerospace structural components;
(4) Engineering plastics, thermosetting plastic；
(5) Adhesive: used as high temperature structural adhesive;
(6) Microelectronic devices application, it is used as a dielectric layer interlayer insulation, as a buffer layer to reduce stress;
(7) Opto-electronic materials used as passive or active waveguide material;
(8) Liquid crystal display using the alignment agent,widely used in liquid crystal display;
(9) Separation membrane, proton transmission film and photo-resist and other fields.
1.3 Overview of fluorinated polyimide
In polymer materials, PTFE, as representative of containing fluorine polymer has become an important class of materials in the field of industrial technology ,for the polyimide, The introduction of trifluoromethyl also received amazing results, fluorine atomic is smallest in addition to hydrogen, F-C bond can be very high. Colorless PI film is from the traditional yellow PI film due to the formation of the intra-molecular and inter-molecular charge transfer complex, the main method to reduce CTC is to introduce containing-fluorine groups in the molecular chain according to structure of fluorine substituted.
PI with the introduction of fluorinated groups can be incorporated from the introduction of fluorinated dianhydride, or from fluorine- containing diamine[5], resulting in low crystallization, low selectivity, and the PI films have low dielectric constant and low refractive index, lower activity and adesion performance is poor. fluorinated groups give PI film excellent performance, so that it has wide range of application: (1) Gas separation membrane containing fluorine groups makes the membrane gas permeation rate greatly improved, and the selectiveness reduced; (2) Low water absorption and low dielectric constant material,PI has a low water absorption rate and dielectric constant; (3) Photoelectric field: Maximum value in the LCD screen of this fluorinated PI has a wide range of applications; (4) Bio-compatible materials: luorinated PI as biocompatible materials in medical equipment research and application value.
1.4 Overview of silicon-containing polyimide
Silicon-containing polyimide is often referred to as polyimide siloxane. The patent appeared in 1970s, Siloxane segment was introduced to improve the processability of PI and increase the adesion with metal, silicon,glass and its bonding[6-7] and reduce the internal stress, low electric constant, low water absorption rate, high resistance to atomic oxygen properties,good solubility and gas transmittance, and used as dielectric films in the microelectronics industry and packaging materials, can also be used for gas me-mbrane separation and wire, Tsai[8] used copolymerization of amino phenyl trimethoxy silane (APTS), aromatic diamineand ODPA , to prepared silicon-containing polyimide(PI) with excellent heat resistance silicon-containing monomer which can be pided into silicon-containing dianhydride and silicon-containing diamine.
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