| abstract |
1,168,136. Electrophotographic materials. NATIONAL LEAD CO. 15 June, 1967 [22 June, 1966], No. 27756/67. Heading H1K. [Also in Division C1] A photoreactive TiO 2 material of anatase crystal structure and suitable for use in copypaper systems, comprising particles of average size 0.05 to 0À15 microns with at least 70% by weight of the particles in the range 0.03 to 0.13 microns and having a sulphur content not more than 0.15% calculated as S on a TiO 2 weight basis, a surface area of 14 to 35 m.<SP>2</SP>/g., a spectral characteristic (measured as described in the Specification) of at least + 4 and a loss in reflectance measured in 0.5M mandelic acid, of at least 5 units in 10 minutes, is claimed per se and prepared by forming a titanium hydrate which is separated by filtration, bleached and washed to remove iron in particular, optionally heated with up to 0.3% of a phosphate compound, e.g. potassium phosphate, prepared in situ from H 2 PO 4 and KOH, and/or 0.3% of a potassium salt (calculated respectively as P 2 O 5 and K 2 O on a TiO 2 weight bases), calcined at 760‹ to 825‹ C. and milled to a particle size as defined above. The statement of prior art refers to the excellent photoconductivity of carbon black. |