Pyrromethene dye sensitized photopolymer—photochemical behavior in polymer matrix and application to photoresist for printed circuit board

The photochemical behavior of the visible light initiating system that consists of a sensitizing dye, 2,6‐diethyl‐8‐phenyl‐1,3,5,7‐tetramethylpyrromethene BF₂ complex (EPP), and a photoacid generator, N‐trifluoromethylsulfonyloxy‐1,8‐naphthalimide (NIOTf), was studied mainly by means of absorption and fluorescence spectrometry not in solution but in a polymer matrix which is a closer medium to the one currently employed in the field of photoresists. Excited singlet electron transfer from EPP to NIOTf was considered as the main reaction pathway in this system. The EPP/NIOTf system was applied to a photoresist for printed circuit board with an appropriate binder polymer which contains an acetal protection group. A pattern profile of the photoresist was exceedingly affected by the amount of photogenerated acids, their diffusion, and amine in the atmosphere. Finally, by controlling exposure energy and the post‐exposure bake (PEB) process, a photoresist with a high resolution (8 µm line and space) was obtained under argon ion laser irradiation. Copyright © 2006 John Wiley & Sons, Ltd.     

Visual pigments. V. Ground and excited-state acid dissociation constants of protonated all-trans retinal schiff base and correlation with theory.

Abstract— The acid dissociation constants of protonated all-trans retinal Schiff base (SB-H⁺) in a 50% water-methanol solution at 0°C is 6–95 for the ground state and nominally 16–65 for the first excited singlet state, with a potential range of ? 12–21. These values are in qualitative agreement with the results of semiempirical MO calculations, which indicate that the total charge density on nitrogen is greater in the first excited singlet than in the ground state (Q_N* > Q_N). However, pertinent to vision, CNDO/2 calculations on all-trans and 11-cis Schiff base and SB-H⁺ indicate that, for torsional angles of approximately 80–100° around the 11–12 double bond, Q_N* < Q_N. This result suggests that it may be possible for the proton to come off the imine nitrogen during isomerization from 11 -cis SB-H⁺ to all-trans SB-H⁺. The potential consequence of this during isomerization of rhodopsin is the initiation of unfolding of the protein opsin.     

Holographic recording using visible-light sensitive polymers based on cationic polycondensation

Negative-working photopolymers based on a cationic polycondensation mechanism were developed. The photopolymers are highly sensitive to 488 nm argon ion laser light, because they use a chemically amplified reaction and are not sensitive to ambient oxygen. These photopolymers are composed of a poly(p-hydroxystyrene) matrix, a hexamethoxy methylmelamine crosslinker and a 2,4,6-tris(trichloromethyl)-1,3,5-triazine–coumarin dye combination as a photo-initiator. They exhibit 0.6 mJ/cm² (D^0.7_g) sensitivity to 488 nm light, as well as a high resolution of 0.5 μm. Due to their high sensitivity and high resolution, a relief-type hologram, larger than 50 × 50 cm, can be recorded in a short exposure time using them.     

The crystal structure of Li2WO4II: A structure related to spinel

Li₂WO₄II, synthesized at 3 kbar and 630°C, has tetragonal symmetry, $\text{I4}{}_1\text{amd}\text{, a = 11.954(2)}$ and c = 8.410(1)Å, Z = 16, D_calc = 5.78 g cm^?3. The structure was determined by countermeasuring 469 independent reflections from a single crystal and was refined up to R = 0.032 by the full-matrix least-squares method. It is based on cubic closest packing of oxygen atoms and is closely related to the β-phase structure of Mg₂SiO₄. W and Li(2) are in octahedral sites and Li(1), in tetrahedral sites. Four Li(1)O₄ tetrahedra form a Li₄O₁₂ group, WO₆ and Li(2)O₆ construct a octahedral double chain along the a axis, and four WO₆ octahedra build a W₄O₁₆ group by sharing their octahedral edges.     

Radiation-induced postpolymerization of nitroethylene

Radiation-induced postpolymerization of nitroethylene in 2-methyltetrahydrofuran glass has been studied and discussed in reference to the results obtained from ESR measurements. No postpolymerization occurred at the temperature below ?150°C. In the temperature range between ?135°C and ?78°C, the polymer yield decreased with increasing postpolymerization temperature. The polymer yield increased linearly with the increase of the preirradiation dose in the range below 0.9 × 10⁶ r. The mean value for chain initiation was estimated to be about 1.3. The following correlations were observed between the results of the postpolymerization and ESR measurements. The postpolymerization started in the temperature range between ?140°C and ?135°C, where the ESR spectrum due to the anion radicals of nitroethylene disappeared. The polymer yield of the postpolymerization decreased with the photoirradiation at ?196°C before warming the samples in parallel with the photobleachability of the anion radicals observed in the glassy mixture by the ESR method. It was concluded from these results that the radiation-induced postpolymerization was initiated by the anion radicals of nitroethylene formed by the capture of electons.     

ESR study on radiation chemical processes in polyvinyl alcohol films at 77°k

Abstract

Trapped electrons (e_t ^?) were detected in irradiated PVA films at 77°K. Yield of e_t ^? was decreased as evaporating water from the films, indicating that water molecules contribute to construct pre-existing traps in the polymer. The radical produced at 77°K was identified as a precursor of the radical produced at room temperature.     

Triethylborane-induced intermolecular radical addition to ketimines

The intermolecular carbon radical addition to ketimines was investigated by using triethylborane as a radical initiator. The screening of reactive radical acceptors showed that pyruvic hydrazone 3 and isatin hydrazone 7 exhibit good reactivities toward nucleophilic alkyl radicals. The reaction of 3 and 7 proceeded effectively even under aqueous-medium reaction conditions. In the presence of BF(3).OEt(2), the radical addition to chiral ketimine 11 proceeded with good diastereoselectivities.     

Influence of nonlinear perturbed terms on the oscillation of elliptic equations

Our concern is to solve the nonlinear perturbation problem for the semilinear elliptic equation in an exterior domain of with . The lower limit of the nonlinear perturbed term is given for all nontrivial solutions to be oscillatory. The tools for obtaining our theorems are the so-called ``supersolution-subsolution' method and some results concerning the oscillation and nonoscillation of solutions of the ordinary differential equation associated with the elliptic equation. A simple example is given to illustrate the main results.