Colour Negative 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 systems used to produce colour transparencies from exposed film are based on the Kodak E-6 process, or further developments, using compatible films. A simph-fication of the process is as follows  

Processing is usually carried out by the Kodak C-41 process. This is simpler than the E-6 colour reversal process, involving only colour development, using a different 

White areas of original image are black Black areas of original image are white Blue areas of original image are yellow 

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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 2.28 Schematic of colour negative film and C-41 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). 

Extra colour negative films (400 ISO), batteries for the camera and flash must be carried in the field. 

Finally, CTA films play an important role in optical applications due to their anti-curl property and their low in-plane birefringence even when the polymer is oriented in combination with high transmittancy (as PMMA), low haze (better than PMMA), and a refractive index of 1.48 [44], Anti-curl is basically a bad shape memory when rolled off from the storage roll, a requirement for the colour negative film, the only left application of CTA film in the category of photography. 

Figure 5.5. Transmission electron micrograph of a thin ( 100 nm thick) cross-section of commercial VRIOO amateur colour-negative film. The top overcoat layer is at the far right. The next is a UV layer with a Lippmann emulsion, followed by the fa.st and slow blue-sensitive layers, two interlayers, fast and slow green-sensitive layers, an interlayer, fast and slow red-sensitive layers, an antihalation layer, and a portion of the PET support. The overall width of the figure corresponds to a total thickness of 53 pm...

Light from the original is absorbed by R,G B sensitive layers of the colour-negative film. 

Atomic silver forms in illuminated regions of the film, and hence the dark colour silver does not form in regions of the film shielded from light, which is why a photographic negative remains colourless in the dark. 

Interest has developed in electrochromic light transmission modulators, which are called smart windows , for control of temperature and lighting in buildings and automobiles. A cross section of an electrochromic light transmission modulator is shown in Fig. 11.31 (Rauh and Cogan, 1988). The two electrochromic elements of the structure are designated ECl and EC2, and are sandwiched between two thin film, optically transparent, electrodes of ITO and separated by an electrolyte. The ECl layer should colour when a negative potential is applied and the EC2 layer should either colour under positive potentials or remain in a transparent state. This is indicated by the chemical reactions ... 

CD-4 1% pet paper prints Colour developer for negative colour film... 

Although these alternatives can be applied in specific systems, their overall performance does not match up to that of cobalt based driers the paint films usually remain too soft, whereas manganese also has a negative impact on the film colour. At A F a biomimetic approach is being followed to develop alternative cobalt free drying catalysts. 

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