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AssigneeMizusawa Industrial Chemicals, Ltd.
InventorsKoichi Usui, Masahide Ogawa, Kunio Goto, Teiji Sato, Masanori Tanaka, Seikichi Takahashi, Kinichi Ono, Seiji Kojima
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Disclosed is a filler for a heat-sensitive recording paper comprising finely divided amorphous silica having a BET specific surface area of 10 to 100 m.sup.2 /g and a bulk density of 0.14 to 0.30 g/cc, said finely divided amorphous silica having such a secondary particle size distribution that secondary particles having a size smaller than 4 microns, as measured by the centrifugal precipitation method, occupy at least 90% by weight of the total particles. This filler is excellent in the effects of preventing the background coloration, improving the lubricating property, preventing the adhesion of scum and improving the image density.
A filler for a heat-sensitive recording paper comprising finely divided amorphous silica having a BET specific surface area of 10 to 100 m.sup.2 /g and a bulk density of 0.14 to 0.30 g/cc, said finely divided amorphous silica having such a secondary particle size distribution that secondary particles having a size smaller than 4 microns, as measured by the centrifugal precipitation method, occupy at least 90% by weight of the total particles.
A composite filler for a heat-sensitive recording paper, which comprises an amorphous silica filler having a BET specific surface area of 10 to 100 m.sup.2 /g and a bulk density of 0.14 to 0.30 g/cc, which has such a secondary particle size distribution that secondary particles having a size smaller than 4 microns, as measured by the centrifugal precipitation method, occupy at least 70% by weight of the total particles, and an organic filler composed of fine particles of an amino resin obtained by condensing substantially equimolar amounts of a functional amino group-containing component and a formaldehyde component in the presence of a catalyst, which has an oil absorption of 20 to 90 ml/100 g and a specific surface area smaller than 20 m.sup.2 /g at a weight ratio of from 90/10 to 10/90.
Dependencies are inferred from the claim text.