METHOD FOR MANUFACTURING SILVER HALIDE PARTICLE, PHOTOSENSITIVE SILVER HALIDE PARTICLE, AND THERMAL DEVELOPMENT SENSITIVE MATERIAL USING THE SAME

PROBLEM TO BE SOLVED: To provide a method for manufacturing photosensitive silver halide particles suppressing an increase in a particle size with a temperature rise in chemical sensitization and capable of forming fine particles without inhibiting the chemical sensitization and spectral sensitization, and to provide a photosensitive silver halide particles obtained by the manufacturing method.SOLUTION: A particle forming process for forming a silver halide by reacting a silver supply compound with a halogen supply compound includes: a step for adding a synthetic polymer of not less than 2 pts.mass and not more than 10 pts.mass with respect to 100 pts.mass of gelatin that is used as a protective colloid, and chemically sensitizing the formed particles under an ambient air temperature of 55°C or more. The average equivalent circle diameter of the obtained silver halide particles is 35 nm or less.