We have studied the new environmental resisting developer which acts as electron acceptor in the color forming reaction with leuco dye as electron donor by use of electronic molecular orbital calculation. We have newly found 2,4-Dihydoxy-2'-methoxybenzanilide (SV-3) as the excellent developer which improves the enviromental resistance of thermal image density. The SV-3 was also conirmed to be non-mutagenic in Ames-test.
The molecular orbital calculations show that the SV-3 is easy to form a stable charge transfer complex with leuco dye and also suggest that color forming stability and enviromental resistance in the thermal paper greatly depend on the degree of overlapping orbitals between the leuco dye and the developer.

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Positive charged toner particle for an electrophotography was attracted to the tip of the tungsten pin electrode by an attractive coulomb's force between the toner particle and the pin electrode. The tip of the tungsten pin electrode was sharpened by an electro-chemical etching and closed to the toner particle on the metal electrode. The value of applied voltage to the pin electrode was 12.8 V for attraction of one toner particle from the single toner layer on the metal electrode to the tip of pin electrode. One toner on the tip of the pin electrode can be transferred to the plain paper by the repulsive coulomb's force.

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This paper describes adhesive force measurements using centrifuge method and effects of toner surface treatments in terms of non-electrostatic adhesive force (van der Waals force) between photoreceptor and toner particles in electrophotography.
Non-electrostatic adhesive force of toner is about 10-40 nN, and is proportional to toner particles size. It has been found that non-electrostatic adhesive force is reduced about 1/10 by treating the toner surface with fine particles, resulting in the force becoming almost independent of toner particles size.
Considering the experimental results based on Langbein equation, it has been clarified to reduce the adhesive force it is effective to use a slightly larger size additives so that the contact points on the photoreceptor can be reduced.

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Mixing Properties of ferrite carrier and small toner particles in a developing unit have been investigated using a newly developed toner concentration sensor with an inductance coil. A measurement equipment with the sensor can measure a toner concentration of two component developer at a sensitivity of 0.01 %. Time responses of the toner concentration in the developing unit are measured precisely by the sensor when toner is consumed and fresh toner is supplied impulsively. From these measurements of time response, it is found that the mixing property of fresh toner supplied into the developer mainly depends on a charging process of the fresh toner. Using the response property of toner mixture, a toner supply rate, and a toner consumption rate, time variation of toner concentration in the developer unit can be simulated. Calculated results of toner concentration based on the simulation are consistent with experimental results.

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