It is known to use various kinds of phenol compounds as electron accepting compounds for pressure-sensitive recording materials or heat-sensitive recording materials, as disclosed in Japanese Patent Publication Nos. 9309/65, 14039/70 (corresponding to British Pat. 1,135,540) and 29830/76, etc. These known phenol compounds, however, are not always satisfactory as electron accepting compounds. In some detail, they are associated with problems such that a color image developed upon reaction with an electron donating leuco dye does not have sufficient density; the density of a color image developed is reduced with time; a white powder is precipitated on the surface (so-called blooming); and the like.
USPTO Backgrounds
USPTO Backgrounds