Oji Paper Co., Ltd.

Osamu Kitao

Masasuke Watanabe

Masashi Matsuda

Motohide Wada

Hitoshi Okada

Harumi Watanabe

Hiroyuki Wakasa

Atsushi Myojo

A coated paper sheet provided with a coating layer formed on a paper sheet substrate and containing a pigment and a binder and optionally a pre-coated polyacrylamide-containing anionic acrylic resin layer formed between the substrate and coating layer, and having a 75&#xb0; specular gloss of 70% or more, an air permeability of 4000 seconds or less, a Clark stiffness, in terms of critical strength L, of 12 cm or more in a cross direction and an internal bond strength of 200 mJ or more, exhibits high resistance to blistering, excellent printer-passing property, and high quality image-recording property and useful for both of offset printing and electrophotographic duplicating or printing.

Coated paper sheet

Process for producing silica particles suitable for use as filler for paper

The present invention relates to a process for easily and efficiently producing silica particles having a narrow particle size distribution and a high porosity from inexpensive starting materials such as sodium silicate. The silica particles of the present invention can be obtained in the form of a slurry containing them by (1) forming a slurry by mixing first particles difficultly soluble in an alkali and soluble in an acid, with an aqueous alkali silicate solution to form a first slurry containing the first particles, (2) neutralizing the first slurry with a mineral acid to prepare a second slurry containing second particles wherein silica is deposited on the first particles, and (3) adding a mineral acid to the second slurry to dissolve the first particles from the second particles, to prepare a third slurry containing silica particles. When the silica particles of the present invention are used as a filler even in a small amount for paper making, the resultant papers have excellent brightness, opacity, opacity-after-printing, etc.

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Yokohama, Japan

Osamu Kitao