In contrast with the experiment by Mason who showed the superadditivity of Phenidone and Metol on ordinary colour development of an iodo-bromide emulsion layer using soluble couplers in the developer, in our experiments using an ordinary colour developer and a diffusion-fast coupler in a chloro-bromide emulsion layer, Phenidone shows no activation on colour densities and only a little activation on silver deposits.
On the contrary, however, profound increase of sensitivity and densities (both colour and silver) are shown on negatives and also significant increase of apparent speed and dramatical reduction of fog level are shown on positives of diffusion-transfer colour development by the introduction of Phenidone (or Metol) in the developer.
And it is concluded that the marked effect observed comes from the enhanced efficiency of the repeated use of the regenerated Phenidone (or Metol) by the restriction of the volume of the developer involved in this closed system.

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The relationship between the ability of spectral sensitization and the quenching of fluorescence of 4-aminonaphthalimide derivatives was studied to obtain the informations regarding the kind of electronic excited state of the dye moleculeswhich participated in the spectral sensitization of different photographic systems, namely electrophotographic zinc oxide layers, electrophotographic titanium dioxide layers, photothermographic papers, and silver chloride emulsions.
Experimental results suggested that a complete quenching of fluorescence of a dye upon adsorption to photosensitive crystals was one of the requirements for it to be a good sensitizer for the photographic system consisting of the adsorbent concerned.
The assumptions that the first excited singlet state of the dye molecules took part in the spectral sensitazation in the zinc oxide electrophotography, but, on the contrary, the first excited triplet state of them did in the photothermography were proposed from the facts that 4-aminonaphthalimide derivatives could begood sensitizers for both electrophotographic zinc oxide layers and photothermographic papers, but in the latter only an iodinated derivative was effective in the spectral sensitization, and that the fluorescence of a 4-aminonaphthalimide was somewhat quenched by iodination possibly due to the inner heavy atom effect.
The inverse order of the intensities of fluorescence emitted by the electrophotographic zinc oxide layers sensitized with 4-aminonaphthalimide derivativesagreed with the order of abilities of adsorption or sensitization of the derivatives in the zinc oxide electrophotography. This evidenced that a dye possessing apolar group interacted strongly with zinc oxide grains even in the dried photosensitive layers, which is otherwise difficult to be proved directly.

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By using a commercial lith-type film as negative, a gray-scale image printed on the negative is developed and finally fixed after 4 to 5 times transfer to afresh film-positive for every transfer by means of usual silver-complex diffusiontransfer process. Both density and amount of silver deposited on each step of the gray-scale image in these successive positives and those in the first and the final negatives are measured. It is found that almost 70% of total silver halide coated on the sensitive film is either developed in the final negative or transfered to the succesive positives. The rest of silver halide (about 30% on averageof the total silver) is considered to be lost in the precessing solution as complexed form. The relation between masses of silver deposited on negative and positivelayer (n and p respectively) is found to be expressed by the following general equation, n/N+p/P=1. It can be said that usually N≥P and the value of P approaches to that of N at an optimum condition.
The result of determination of covering power of silver images shows a considerable difference between negative-images (0.25-0.52) and positive-images (2.0-3.2) and also between the negative-images and the usual chemically-developed images (0.85-1.1) of the same material. These values are also found to vary abnormally with exposure in this process. The fact shows that there is substan -tial difference of image structure between them.

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Novel couplers combined chemically with a polymer by a covalent bond to prevent diffusion were synthesized and named “Reactive Couplers ”.
The couplers are shown by the general formula Q-T-X in which Q represents a coupler residual group that can couples with an oxidation product of a color developer to form a dye, X represents a reactive group, and T representsa group for combining X with Q.
Five types of coupler having such reactive groups as chloro-s-triazine, chloropyrimidine, ethyleneimine, active chloromethyl and sulfonylfluoride were synthesized.

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