Heat sensitive color developing material and heat sensitive element using the same

A thermal-sensitive element comprising a base substrate and a thermal sensitive color developing material held by the base substrate, wherein:

• the thermal-sensitive color developing material contains metal particles a d a matrix substance;
• the size of the metal particles are irreversibly increased at room temperature due to cohesion;
• and
• the metal particles are formed from a mixture of a metal ion and an .alpha.-hydrogen-containing alcohol upon irradiation with light, and the metal ion is at least one member selected from the group consisting of gold, platinum, silver, copper, tin, rhodium, palladium and iridium.

A method for producing a thermal-sensitive color developing material, comprising the steps of:

• preparing a mixture containing metal ion, an .alpha.-hydrogen-containing alcohol and a matrix-forming material;
• and
• irradiating the mixture with light,
• wherein the metal ion is at least one member selected from the group consisting of gold, platinum, silver, copper, tin, rhodium, palladium and iridium.

A method for producing a thermal-sensitive element including a base substrate and a thermal-sensitive color developing material held by the base substrate, comprising the steps of:

• preparing a mixture containing metal ion, an .alpha.-hydrogen-containing alcohol and a matrix-forming material;
• making the mixture held by the base substrate;
• and
• irradiating the mixture held by the base substrate with light so as to form the thermal-sensitive color developing material,
• wherein the metal ion is at least one member selected from the group consisting of gold, platinum, silver, copper, tin, rhodium, palladium and iridium.

A method for producing a thermal-sensitive element including a base substrate containing metal particles, comprising the steps of:

• preparing a mixture containing metal ion and an .alpha.-hydrogen-containing alcohol;
• impregnating the mixture into the base substrate;
• and
• irradiating the mixture impregnated in the base substrate with light so as to form the metal particles,
• wherein the metal ion is at least one member selected from the group consisting of gold, platinum, silver, copper, tin, rhodium, palladium and iridium.