Photographic systems

Materials are being developed to exhibit both photochromic and photographic behaviors one such system is based on a substituted indolinospiro-hen opyrene embedded in a polystyrene matrix (26). This system acts as a photochromic system at low exposure in the uv range and at high exposure it functions as a photographic system. The image can be devisualized by heat and can be restored many times with uv irradiation. 

Heat-processed photographic systems have been described that utilize silver behenate, silver laurate, and silver stearate. These silver salts are coated on paper in the presence of organic reducing agents (78,79). 

For most color photographic systems, development is the rate determining step, and within that step the formation of semiquinone is the slow process (37). The fate of the highly reactive QDI is deterrnined by the relative rates of a number of competing processes (38). The desired outcome is reaction with ionized coupler to produce dye (eq. 3). Typically, the second-order rate constant for this process with ionized coupler is about 10 to 10 ... 

Dye Stability. The dyes used in photographic systems can degrade over time, both by thermal reactions and, if the image is displayed for extended periods of time, by photochemical processes. The relative importance of these two mechanistic classes, known as dark fade and light fade. 

The perceived color stabiUty of a photographic system is usually limited by the fa ding of its least stable dye, which can produce an undesirable shift in color balance. Whereas recovery of such faded images is often possible, a so-called neutral fade, in which all three color records lose density at approximately the same rate, is usually preferred. 

Complexes of rf-elements with heterocyclic ligands as promising components of non-silver photographic systems 97UK735. 

Triphenylmethane leuco dyes are used for photographic materials. The photographic system requires a polymer binder such as acrylic acid-methyl methacrylate copolymer115 or a copolymer of isophthalic and terephthalic acids116 a sensitizer such as 4-(4-n-amyloxyphenyl)-2,6-bis(3-ethylphenyl)-thiapyrilium perchlorate,117 a photo initiator such as hexaarylbisimi-dazole,118 and phenyl tribromomethyl sulfone, cycloalkane such as 1,2,3, 4,5-pentabromo-6-chlorocyclohexane,119 or 3-benzylidene-9-methyl-2,3-dihydro- 1 TZ-cyclopenta [b] quinoline.120... 

The use of conventional photographic systems for data acquisition, printing and archiving results of planar chromatography [401] has now largely been superseded by video documentation systems. A sample method for documentation of TLC plates has been described by a combination of computer, scanner, and digital colour thermal printer resulting in a very... 

Heat-process photographic systems, silver compounds in, 22 686 Heat pumps, 20 146... 

SILVER LAURATE, IN HEAT-PROCESS PHOTOGRAPHIC SYSTEMS... 

Photoconductivity in photographic systems. II. Some applications to the phenomena of supersensitization, desensitization and the Becquerel effect. J. chem. Physics 15, 539 (1947)-... 

It should also be borne in mind that cation-radicals are strong Lewis acids and can act as acceptors of the nucleophile electron pair to form a coordinative bond. Such a process was well documented (Gould et al. 2003, references therein). The Lewis-type binding of water by the aminosilane cation-radical appeared to be crucial for fragmentation with the formation of an a-amino carborad-ical. The latter plays an important role in the efficiency of photographic systems. Scheme 5.18 illustrates this coordinative-promoted fragmentation of the cation-radical. 

Charged Particle and Photon Interactions in Metal Clusters and Photographic Systems Studies... 

A proposal made about 70 years ago (13MI11400) to use p-phenylenediamines and p-aminophenols as developers which give dyes with a variety of couplers is the basis of present day practice. Since the original idea was formulated numerous developers and couplers have been synthesized. Many subtle effects within the photographic systems can be achieved as a result of the specific structure of the developers and couplers. 

The initial limited interest can be partially attributed to the complete reversibility of the photoreaction and the consequent fugitive nature of the image. Much attention has been given to stabilizing photochromic images, but often another photographic system is employed to record the image before it fades. On the other hand, the reversibility of the reaction renders photochromic materials re-useable. 

The coverage has been limited to the applications of coordination compounds or of the coordination chemistry of relatively soluble ligands and metal species. Numerous chemical agents in photographic systems function by means of adsorption on silver halide grains and silver metal surfaces. Such chemical interactions lie outside the confines of coordination chemistry defined for this work and have not been discussed. 

---