Photosensitive polyimides

The polymer-dispersed liquid crystal was used as a modulating medium in optically controlled modulators instead of the liquid crystal [261-264], The sandwiched structure from polyimide photosensitive film and the polymer dispersed liquid crystal film - i.e. the optically controlled solid state modulator -had the characteristics presented in Fig. 36 [261]. Contrast ratio 35 1, response time > 400 ps, decay time 80 ms and sensitivity 5 x 10 sJcm 2 were obtained. 

Direct Patterning of Photosensitive Polyimides. Photosensitive polyi-mides (PSPIs) are recently developed materials that can be directly photo-patterned like a negative photoresist (80,85,88,146-148). The most common PSPIs are polyamic acids that have been esterified with photoreactive alcohols and combined with photoinitiators to form a polymer that will crosslink under exposure to UV radiation and become insoluble. The unexposed material is selectively dissolved in a developer solution, and the patterned film is then cured to convert the cross-linked polyamic acid to a polyimide and drive off the cross-linking groups. 

OGG Microelectronic Materials, Olin/CIBA-GEIGY venture photosensitive polyimides, high performance semiconductors... 

Photosensitive functions are in many cases also heat sensitive, so the preparation of photosensitive polyimides needs smooth conditions for the condensations and imidization reactions. Some chemical reactants, which can be used for polyamide preparation, have been patented for the synthesis of polyimides and polyimide precursors. For example, chemical imidization takes place at room temperature by using phosphonic derivative of a thiabenzothiazoline.102 A mixture of N -hydroxybenzotriazole and dicyclohexylcarbodiimide allows the room temperature condensation of diacid di(photosensitive) ester with a diamine.103 Dimethyl-2-chloro-imidazolinium chloride (Fig. 5.25) has been patented for the cyclization of a maleamic acid in toluene at 90°C.104 The chemistry of imidazolide has been recently investigated for the synthesis of polyimide precursor.105 As shown in Fig. 5.26, a secondary amine reacts with a dianhydride giving meta- and para-diamide diacid. The carbonyldiimidazole... 

K. Horie and T. Yamashita, Photosensitive Polyimides, Technomic, Lancaster, PA, 1995. 

Phosphoms pentoxide-methanesulfonic acid (PPMA), 315 Phosphorylation, 187 Photoacid generator (PAG), 317 Photoluminescence, 490 Photosensitive polyimides, 270-271, 292 PHRRs. See Peak heat release rates (PHRRs)... 

Positive imaging techniques, 19 201 Positive ion spectroscopy, 24 107 Positive photochromism, 6 588 Positive photoresists, 20 280-281 Positive photosensitive polyimides,... 

High-performance polyimide-positive photosensitive heat resistance resins, (id, were prepared by Yamanaka et al. (3) and used in photosensitive compositions. 

Poly(amic acids) in which the ortho-carboxylic group has been chemically modified to either an ester- or amide moiety have been known for many years. However, their commercial significance was non-existent until very recent applications involving dielectric insulators [48] and photosensitive polyimide precursors [49, 50]. As with many synthetic pathways, there are generally several ways to arrive at the same goal. Similarly, the preparation of derivatized poly(amic acids) can be divided into two general categories ... 

Compared to Kapton, more sensitive soluble polyimide films were investigated [235-236]. A photosensitivity of up to 30 m2 J 1 was achieved in electrophotographic regimes. The photogeneration of the charge carriers occured via exiplex formation and the holes are the predominant carriers. The spectral... 

Fig. 31. Photosensitivity spectra of the photoconductive polyimide-licjuid crystal modulator for positive right) and negative (left) bias on the photoconductor. Voltages in V 80 (/,/ ) 20 (2,2) [259]...

Besides polyimides, photoconductive polymers with conjugated bonds also can be successfully used in liquid crystal spatial light modulators [262-264], The high resolution, mechanical and electrical stability and possibility for sensitization of the photosensitivity make the use of organic polymer photoconductors in spatial light modulators very attractive. Devices such as phase... 

Polyimides based on 2,6-diamino-p-cresol were acylated with acryloylchloride [71, 72] to impart photosensitivity to these polymers. The acylation was carried out in accordance with Scheme 5.12. The extent of esterification of hydroxyl groups, as determined by H-NMR spectroscopy, ranged from 60 to 40% for various polyimides (Table 5.14). 

Figure 19. Process steps for patterning polyimides by wet etching and dry etching and for direct photopatterning of a photosensitive polyimide. The abbreviation PR stands for photoresist.

An all-polyimide microchannel chip was created by patterning two photosensitive polyimide layers, and then by laminating the two layers based on a partially imidized interfacing layer [228,229]. 

K. Horie, Introduction to Photopolymers and Microelectronics, in K. Horie, T. Yamashita (Eds.), Photosensitive Polyimides, Technomic Publishing Company, Inc., Lancaster, PA, 1995. 

Some new electronic applications of polyimide-siloxane adhesives have been already partially reviewed. In addition, the development of photo-crosslinkable copolymers has been of great interest for the development of components of electronic devices [126]. The general field of photosensitive polymers was reviewed by Horie and Hamishita in 1995 [127]. A number of papers have investi-... 

Sashida N, Hirano T, Tokoh A (1989) Photosensitive polyimides with excellent adhesive property for integrated circuit devices. Proc Electron Compon Conf 39th 167070 82... 

Horie K, Hamashita T (1995) Photosensitive polyimides fundamentals and applications. Technomic, Lancaster Basel... 

Efforts continue in the Far East, particularly in Japan, by Horie et al., on photosensitive polyimides containing epoxide groups [44,45]. These studies focus on the chemical amplification of photo crosslinks in the resulting materials for use in making mask materials in silicon chip fabrication. 

Title Photosensitive Polyimides for Optical Alignment of Liquid Crystals... 

Polyimides derived from 1,2,3,4-cyclobutanetetracarboxylic dianhydride and selected aromatic diamines have been found effective as photosensitive materials. These materials have applications as liquid crystals aligners, liquid crystal displays, and related liquid crystal optical elements. The fdm preparation uses a noncontact method that can reduce dust and static charge buildup and improve resolution. 

The preparation of other aromatic diamines, (III), useful in preparing photosensitive polyimides effective as liquid crystal alignment agents is provided by the author [2]. 

---