Intrinsically Negative Photosensitive Polyimides with Enhanced High-Temperature Dimensional Stability and Optical Transparency for Advanced Optical Applications via Simultaneous Incorporation of Trifluoromethyl and Benzanilide Units: Preparation and Properties

Abstract

Negative photosensitive polyimides (PSPIs) with the photo-patterned ability via the photocrosslinking reactions induced by the i-line (365 nm) and h-line (426 nm) emitting wavelengths in high-pressure mercury lamps have been paid increasing attention in semiconductor fabrication, optical fiber communications, and other advanced optoelectronic areas. In the current work, in view of the optical and thermo-mechanical disadvantages of the currently used negative PSPIs, such as the intrinsically photosensitive or auto-photosensitive systems derived from 3,3’,4,4’-benzophenonetetracarboxylic dianhydride (BTDA) and the ortho-alkyl- substituted aromatic diamines, a series of modified negative PSPIs with the enhanced optical transparency in the wavelength of 365~436 nm and apparently reduced coefficients of linear thermal expansion (CTE) were developed. For this purpose, a specific aromatic diamine with both of trifluoromethyl and benzanilide units in the molecular structures, 2,2’-bis(trifluoromethyl)-4,4’-bis[4-(4-amino-3-methyl)benzamide]biphenyl (MABTFMB) was copolymerized with BTDA and the standard 3,3’,5,5’-tetramethyl-4,4’-diaminodiphenylmethane (TMMDA) diamine via a two-step chemical imidization procedure. As compared with the pristine PI-1 (BTDA-TMMDA) system, the new-developed fluoro-containing PSPI systems (FPI-2~FPI-7) exhibited the same-level solubility in polar aprotic solvents, including N-methyl-2-pyrrolidone (NMP) and N,N- dimethylacetamide (DMAc). The FPI films cast from the corresponding FPI solutions in NMP showed the optical transmittances of 78.3–81.3% at the wavelength of 436 nm (T436, h-line), which were much higher than that of the PI-1 (T436 = 60.9%). The FPI films showed the CTE values in the range of 40.7 × 10−6/K to 54.0 × 10−6/K in the temperature range of 50 to 250 °C, which were obviously lower than that of PI-1 (CTE = 56.5 × 10−6/K). At last, the photosensitivity of the FPI systems was maintained and the micro-pattern with the line width of 10 μm could be clearly obtained via the standard photolithography process of FPI-7 with the molar ratio of 50% for MABTFMB in the diamine moiety.

Advancements in Synthesis Strategies and Optoelectronic Applications of Bio-Based Photosensitive Polyimides

“…Tese materials broke through the traditional design framework, achieving both excellent photoresponsiveness and improved thermal stability and dimensional stability at high temperatures. In exploring the improvement of optical transparency and thermomechanical properties, a study [43] creatively developed a novel aromatic diamine unit, called MABTFMB, and copolymerized it with BTDA and standard TMMDA, as shown in Figure 3. Tus, a series of optimized PSPIs were successfully developed.…”

Quaternary copolymerized polyimides and negative photosensitive polyimides: preparation and properties

“…[1][2][3][4][5][6][7][8] Photosensitive polyimide (PSPI) simplifies traditional PI processing. 7,[9][10][11][12][13] The graphic technology of PI has also developed. 14 Fabricating PI pattern becomes more convenient.…”

“…This rewritable pattern could be explained by dynamic phototriggered cis–trans isomerization of the azobenzene. Gao 12 reported an intrinsically negative photoresist with high optical transparency and high-temperature dimensional stability based on a poly (acid amid) (PAA) copolymer. A ternary photosensitive polyimide was synthesized by Xu 23 for liquid crystal display (LCD) based on BTDA, 6FDA and 2,2-bis (3-amino-4-hydroxyphenyl) propane (BAP).…”