Color development - Hashokugenzo

This is the process of forming dyes in the developed silver when a silver halide photographic emulsion is exposed to light and developed. Dyes are usually produced by reacting the oxidation product of the developing agent with an organic compound called a coupler. p -Phenylenediamine compounds are commonly used as developing agents, and active methylene compounds, phenols, and aromatic amines are used as couplers. There are two types of couplers: one that contains the coupler in the emulsion and one that contains it in the developer, and these are called internal type and external type color development, respectively. All color films with three layers of emulsion are internal type, except for a very small number of reversal films. External type films require the three layers to be developed separately, but internal type films can be developed simultaneously. After development, the remaining silver halide and the developed silver are chemically removed. In color materials with three layers of emulsion, dyes are produced that are complementary to the color to which each layer is exposed. Various measures are taken to prevent the coupler from diffusing into adjacent layers.

Source: Morikita Publishing "Chemical Dictionary (2nd Edition)" Information about the Chemical Dictionary 2nd Edition

ハロゲン化銀写真乳剤を，感光後，現像するときに現像銀の部分に色素を形成させる過程をいう．通常，現像主薬の酸化生成物と，カプラーとよばれる有機化合物とを反応させて色素をつくる．現像主薬としてはp-フェニレンジアミン系化合物がよく使われ，カプラーとしては活性メチレン化合物，フェノール類，芳香族アミン類が用いられる．カプラーを乳剤中に含む形式と現像液中に含む形式があり，それぞれ内型，外型発色とよばれる．3層に乳剤を重ねたカラーフィルムでは，ごく一部の反転フィルム以外はすべて内型である．外型は3層を別々に現像しなくてはならないが内型は同時に現像できる．現像後，残ったハロゲン化銀と生成した現像銀は化学的に除去される．乳剤が3層構成のカラー感材では，各層が感光する色の補色にあたる色素が生成される．また，カプラーの隣層への拡散を防ぐため，種々の工夫がなされる．

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