Colour Reversal Film

The two basic types of colour film are the colour reversal film for transparencies and the colour negative film used to produce prints on colour papers. 

The basic structure of a colour negative film is the same as in a colour reversal film, with the relevant colour coupler incorporated into each layer. The difference between the two films is that after development the dye image, is complementary to the final colour required in the resultant hard copy print (see Figure 2.28). 

Figure 2.27 Schematic of colour reversal film and E-6 processing.

Cyan Couplers and Dyes. Cyan couplers need to produce very bright dyes absorbing in the region of 630-700 nm and to date only phenols and, to a much lesser degree, naphthols have been found to be commercially acceptable. Typical is the phenol (2.89) used in both eolour reversal and colour negative films, depending on the nature of the R group, to produee indophenols, e.g. (2.90). 

Colour formers such as compounds 243 and 245 are not inherently thermochromic. For example, they melt without any change in colour. However, they may be used to generate colour thermally, either irreversibly or reversibly, as composite materials. In thermally sensitive paper, the colour former and an acidic developer, usually a phenol, are dispersed as insoluble particles in a layer of film-forming material. When brought into contact with a thermal head at around 80-120 °C, the composite... 

Similar results are found for doped polyvinyl alcohol44. This system is of interest because its colour changes when the polymer is stretched, and the stretched film is a good polarizer. At low iodine content, the film is brown or yellow, but becomes blue on stretching this change is reversible. The colour can also be enhanced by adding boric acid to the iodinedoping solution. 

The colour of ICPs can also be sensitive to temperature. Substituted polythiophenes, in particular, show a marked blue shift of the highest wavelength absorption band when films or solutions are heated [7-9]. These reversible colour changes have been attributed to a twisting of the polymer backbone to a less ordered non-planar conformation. Less dramatic thermochromic effects have also been reported for polyanilines [3,10,11] where circular dichroism studies of... 

An interesting property of thin films of the iron(II) complexes in the mesophase is their thermochromism. A reversible colour change from purple (low-spin state) to whitish (high-spin state) was observed by heating or cooling the compound around 60 °C. This work was extended to complexes in which the tosylate counter ions were replaced by tetrafluoro-borate and triflate ions. The resulting compounds were polymeric with a one-dimensional structure. Several of the complexes were liquid-crystalline at room temperature and their mesophase was either hexagonal... 

Other common members of the anodic ECM family are niobium and cobalt oxides. The lithiated versions of these oxides appear as convenient counterelectrodes in WO3 windows. Thin films of these lithiated oxides, prepared by sputtering on ITO-glasses, show reversible removal of lithium ions accompanied by electrochromic colour changes [44-46]. For instance, films of Lio.sCo02 can be cycled with good reversibility between a pale transparent bronze to a deep brown colour, this allowing the realization of windows of the type ... 

Adhesive materials used in vinyl lamination processes are discussed in detail. Characteristics of cold line epoxies and water-based emulsions are discussed. Information is presented on the lamination processes and applying the adhesive. Vinyls most commonly used are said to be Opaque Top Printed Laminate (OTPL)ZKlear View, Opaque Embossed (OE)/Solid Colour Film, Reverse Printed (RP) and Top Printed (TP). 

The direct electrochemistry of redox proteins such as ferredoxin and blue copper protein was studied. The additional effect of poly(L-lysine) on the redox behaviour of horse heart cyt c at functional electrodes has been reported Electropolymerized films such as PAn undergo redox reactions producing a colour change. This is described in Sect. 5.2. The anodic oxidation of poly(iV-vinylcarbazole) films was shown to involve initially the cross-linking of the polymer chains by oxidation of the carbazole moieties and dimerization of the resulting pendant carbazole cation radicals The resulting dimeric carbazole unit is more easily oxidized than the monomer and undergoes a further (reversible) two-electron oxidation. 

Leclerc et al. [64] have reported that electro-polymerized PMT and POT films exhibit multiple and reversible colour changes from pale-yellow to green to blue-violet and bear a relationship to their cyclic voltammograms. They have recorded the electronic absorption spectra of these polymers in 0.1 M H2SO4... 

Electrochromism. Electrochromic materials have the property of a reversible and visible change in transmittance and/or reflectance associated with an electrochemically induced redox process involving electroactive species typically deposited onto an electrode surface as a thin film. The redox state of the material may be switched by an electron transfer reaction at an electrode and the observed colour change results from the generation of different electronic absorption bands according to the redox state. Such a colour change is commonly reported between a transparent ( bleached ) state and a coloured state, or between two coloured states. or even between multiple coloured states (multichromic). ... 

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