Aromatic polyimide films

Aromatic polyimides have excellent thermal stability in addition to their good electrical properties, light weight, flexibility, and easy processability. The first aromatic polyimide film (Kapton, produced by DuPont) was commercialized in the 1960s and has been developed for various aerospace applications. The structure of a typical polyimide PMDA/ODA prepared from pyromellitic dianhydride (PMDA) and 4,4 -oxydianiline (ODA), which has the same structure as Kapton, is shown in (1). Aromatic polyimides have excellent thermal stability because they consist of aromatic and imide rings. 

Aromatic polyimide films that are spin-coated or solution-cast with thicknesses under 15 jm exhibit structural anisotropy in the condensed state. This anisotropy is associated with the tendency of the chains to align parallel to the substrate surface, undergoing what is described as in-plane orientation. 

S. Katsuki and H. Mii. Process for preparing metal-coated aromatic polyimide film. US Patent 7232610, assigned to UBE Industries, Ltd. (Yam-aguchi, JP), June 19, 2007. 

Linear Optical Anisotropy in Aromatic Polyimide Films and Its Applications in Negative Birefrii ent Compensators of Liquid-Crystal Displays... 

It has been recognized since the 1960s that aromatic polyimide films exhibit... 

Several experiments have been customarily utilized to characterize the structural anisotropy in films. One of the most widely used methods is wide angle X-ray diffraction WAXD) experiments (1-4). Figure 2 shows a set of WAXD patterns under both the reflection and transmission modes on a crystalline aromatic polyimide films synthesized from 3,3, 4,4 -biphenyltetracarboxylic dianhydride (BPDA) and 2,2-... 

Aromatic polyimide films of varying thickness were prepared to study the effect of the thickness on the refractive indices. Figure 6 shows that the refi active indices are fairly independent of the film thickness in the range of 1 pm to 15 pm for 6FDA-PFMB. For thicknesses above 15 pm, the difference between the in-plane and out-of-plane refractive indices ( and ) gradually decreases with increasing the film thickness. This indicates that the thin film linear optical properties gradually approach the bulk properties which should be three-dimensionally isotropic. 

We have investigated many macroscopic properties of the organo-soluble aromatic polyimide films and all of them exhibit anisotropic behaviors which are closely associated with the anisotropic structure in the films. One question still remains is whether we can find a common physics background to describe these properties. If we consider the fi-ee energy (or internal energy or energy) term, the first derivative of... 

In summary, we have briefly reviewed our understanding in the development of organo-soluble aromatic polyimides via molecular design and architecture control and the establishment of relationships between the anisotropic structure and properties in the films. These anisotropic structures and properties are also found to be film thickness and molecular weight dependent. In particular, the LOA behavior has led to a invention where these aromatic polyimide films can be used as UNB retardation compensators in LCDs to increase viewing angles. This technology initiated from our researches has been commercialized to produce compensators for wide applications in LCDs,... 

The aromatic polyimide films (i 5) used in this study are listed in Table I. The dianhydride monomers 2,2-bis(3,4-dicarboxy-phenyl)hexafluoropropanedian-... 

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