Developer solutions

Dichromated Resists. The first compositions widely used as photoresists combine a photosensitive dichromate salt (usually ammonium dichromate) with a water-soluble polymer of biologic origin such as gelatin, egg albumin (proteins), or gum arabic (a starch). Later, synthetic polymers such as poly(vinyl alcohol) also were used (11,12). Irradiation with uv light (X in the range of 360—380 nm using, for example, a carbon arc lamp) leads to photoinitiated oxidation of the polymer and reduction of dichromate to Ct(III). The photoinduced chemistry renders exposed areas insoluble in aqueous developing solutions. The photochemical mechanism of dichromate sensitization of PVA (summarized in Fig. 3) has been studied in detail (13). 

Heat or thermal development is another example of amplification that does not require the use of aqueous development solutions. 

The process by which a solubility differential between exposed and unexposed areas occurs is well known (74). Photodegradation products of the naphthoquinone diazide sensitizer, eg, a l,2-naphthoquinonediazide-5-sulfonic acid ester (11), where Ar is an aryl group, to an indene carboxylic acid confers much increased solubility in aqueous alkaline developer solutions. 

Although the varied uses for which DIR couplers are employed call for precise control over where the inhibitor diffuses, the very complexation mechanism by which inhibitors work would seem to preclude such control. The desired ability to target the inhibitor can be attained by the use of delayed release DIR couplers, which release not the inhibitor itself, but a diffusable inhibitor precursor or "switch" (Fig. 16) (98). Substituents (X, R) and stmctural design of the precursor permit control over both diffusivity and the rate of inhibitor release. Increasing the effective diffusivity of the inhibitor, however, means that more of it can diffuse into the developer solution where it can affect film in an undesirable, nonimagewise fashion. This can be minimized by the use of self-destmcting inhibitors that are slowly destroyed by developer components and do not build up or "season" the process (99). 

A basic tenet of risk communication is that people have a right to participate in decisions that affect their lives. The goal of risk communication should be to inform the community about the risks and potential health effects of your activities and to involve the public in developing solutions to any related problems. 

In addition to a near-shock and an acoustic region, Deshaies and Clavin (1979) distinguished a third—a near-piston region—where nonlinear effects play a role as well. As already pointed out by Taylor (1946), the near-piston flow regime may be well approximated by the assumption of incompressibility. For each of these regions, Deshaies and Clavin (1979) developed solutions in the form of asymptotic expansions in powers of small piston Mach number. These solutions are supposed to hold for piston Mach numbers lower than 0.35. 

This is where mentoring comes in. Its powerful methodology picks up where the other solutions fail. Its dialogues will support your employees both by providing a cathartic element and by helping mentees to define their (change) problems and to develop solution strategies. 

Micro reactors are continuous-flow devices consuming small reaction volumes and allowing defined setting of reaction parameters and fast changes. Hence they are ideal tools for process screening and optimization studies to develop solution-based chemistries. 

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