Process for generation of unbuffered super-acid and for imaging

An imaging process comprising:

• providing an imaging medium having an acid-generating layer comprising a superacid precursor and an infra-red dye capable of absorbing infra-red radiation having a wavelength within the range of about 700 to about 1200 nm, the superacid precursor being capable of being decomposed by ultraviolet radiation having a wavelength in the range of about 180 to about 400 nm in the absence of the infra-red dye to form a superacid, the superacid precursor not being decomposed by infra-red radiation having a wavelength within the range of about 700 to about 1200 nm in the absence of the infra-red dye but being decomposed by infra-red radiation having a wavelength within the range of about 700 to about 1200 nm in the presence of the infra-red dye, the acid-generating layer further comprising a secondary acid generator capable of acid-catalyzed decomposition by unbuffered superacid to form a secondary acid, and the imaging medium further comprising a color-forming layer comprising an acid-sensitive material which changes color in the presence of the secondary acid;
• imagewise exposing the imaging medium to infra-red radiation of a frequency absorbed by the infra-red dye, with absorption of the infra-red radiation and decomposition of part but not all, of the superacid precursor without formation of unbuffered superacid but with formation of a protonated product derived from infra-red dye;
• thereafter exposing the medium to ultraviolet radiation having a wavelength in the range of about 180 to about 400 nm, the ultra-violet exposure causing decomposition of additional superacid precursor and being continued for a time such that in areas of the medium exposed to both the infra-red and ultra-violet radiation, unbuffered superacid is present, but in areas of the medium exposed only to the ultra-violet radiation, no unbuffered superacid is present;
• thereafter heating the medium and thereby, in areas of the medium exposed to both the infra-red and ultra-violet radiation, causing the unbuffered superacid present to cause decomposition of the secondary acid generator, with formation of the secondary acid, the areas of the medium exposed only to the ultra-violet radiation remaining essentially free from the secondary acid;
• and
• mixing the acid-generating and color-forming layers so that, in areas of the medium exposed to both the infra-red and ultra-violet radiation, the secondary acid causes the color change of the acid-sensitive material, while in areas of the medium exposed only to the ultra-violet radiation, essentially no color change of the acid-sensitive material occurs.

A process for generation of unbuffered superacid and subsequent generation of a secondary acid, which process comprises:

• providing a medium containing a mixture of a superacid precursor and a dye capable of absorbing actinic radiation of a first wavelength, the superacid precursor being capable of being decomposed by actinic radiation of a second wavelength shorter than the first wavelength in the absence of the dye, but not being decomposed by actinic radiation of the first wavelength in the absence of the dye, the superacid precursor being decomposed by actinic radiation of the first wavelength in the presence of the dye;
• irradiating part of the medium with actinic radiation of the first wavelength, thereby causing, in the irradiated part of the medium, absorption of the actinic radiation, and decomposition of part, but not all, of the superacid precursor, without formation of unbuffered superacid but with formation of a protonated product derived from the dye;
• thereafter irradiating a larger portion of the medium with actinic radiation of the second wavelength, thereby causing, in the part of the medium exposed to the radiation of both the first and second wavelengths, decomposition of additional superacid precursor, with formation of unbuffered superacid, without generation of unbuffered superacid in the part of the medium exposed to the radiation of the second wavelength but not to the radiation of the first wavelength;
• thereafter, heating the medium containing the unbuffered superacid while the superacid is admixed with a secondary acid generator capable of superacid-catalyzed decomposition to form a secondary acid, such that, in the part of the medium irradiated with the actinic radiation of the first wavelength, the unbuffered superacid catalyzes the thermal decomposition of the secondary acid generator and the secondary acid is formed, whereas the part of the medium not irradiated with the actinic radiation of the first wavelength remains essentially free from the second acid,
• wherein the secondary acid generator is an oxalic acid diester and the secondary acid generated therefrom is oxalic acid or an oxalic acid monoester having one carboxyl group.