Xerographic sensitivity

Figure 14. The spectral dependence of the xerographic sensitivity of the nonaggregated homogeneous dye-polymer film, the aggregated film, and the aggregated and sensitized film. The sensitivity is the reciprocal of the energy required for a photodischarge from 500 to 250 V. (Reprinted with permission from Ref. [31].)...

In an attempt to improve the synthetic yield of high-sensitivity squaraines, e.g., Sq-1 and Sq-8, mixtures of squaraines were synthesized by reacting either squaric acid or dialkyl squarate with a mixture of N,N-dimethylanilines [171-173]. The resulting squaraine mixtures show very similar solution and solid state properties as comparable symmetrical squaraines. More importantly, they also exhibit acceptable xerographic sensitivity. Structural analyses indicated that each of these mixtures consists of two symmetrical squaraines and one unsymmetrical squaraine. The observation of favorable photoconductive properties from these compositions was initially a surprise because it is generally... 

The XeroX Copier Machine Model A was announced in 1949, and involved compHcated manual operation. Copies of acceptable quaUty were operator dependent. The Copyflo printer, introduced in 1955, was the first automated xerographic machine and enabled the production of copies on a continuous web of ordinary paper. Early electrophotographic products used paper coated with dye-sensitized zinc oxide Electrofax which had met market resistance in terms of aesthetics and cost, so that in 1958 the total market was only about 100 million (1—3,5). 

The advantage of this process over other xerographic processes using conventional photoconductors is that the most sensitive part of the photoconductor is protected from the corrosive environment. This helps to increase the useful life of the device. The process itself, however, is rather comphcated. 

A highly sensitive CdS pigment was also developed for a conventional xerographic appHcation. Optimum xerographic properties were obtained using copper doping at Cu concentrations of 200—300 ppm (26). 

Just as the growth of xerographic copying and laser-printing, which derives from xerography, was a physicists triumph, the development of fax machines was driven by chemistry, in the development of modern heat-sensitive papers most of which have been perfected in Japan. 

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