Coated paper sheet
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° 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.
1. A coated paper sheets usable for on-demand-printing purposes using an offset press or an indirect drying electrophotographic printer,
comprising:
a paper sheet substrate and
a coating layer formed on at least one surface of the sheet substrate by coating an aqueous dispersion liquid comprising, as principal components, a pigment and a binder, drying the coated liquid layer and smoothing the dried coating layer, and having a 75 degrees specular gloss of 70% or more, determined in accordance with TAPPI T480 om-92, wherein the paper sheet substrate is one surface-sizepressed, during a paper-forming procedure for the paper sheet substrate, with an aqueous sizepress liquid containg an anionic acrylic resin which comprises a copolymer of 50% by mass or more of acrylamide with 1 to 40% by mass of acrylonitrile and 1 to 20% by mass of at least one member selected from acrylic acid and methacrylic acid, in a dry solid amount of 0.5 to 3 g/m 2 and has a basis mass of 50 to 110 g/m 2 ,
wherein the coated paper sheet has an air permeance, and
wherein the coated paper sheet exhibits, as a whole,
(1) an air permeability of 4000 seconds or less, determined in accordance with JIS P 8117 using Type B testing device,
(2) a Clark stiffness, in terms of a critical length L, of 12 cm or more, determined in a cross direction of the coated paper sheet in accordance with JIS P 8143 using a Clark stiffness tester and a specimen having a width of 30 mm, and
(3) an internal bond strength of 200 mJ or more, determined in accordance with TAPPIUM 403.
2. The coated paper sheet as claimed in claim 1 , wherein the paper sheet substrate exhibits, when immersed in water having a temperature of 20° C. for 5 seconds, a increase in thickness of 40% or less, calculated in accordance with the following equation:
A (%)={( T 1 −T 0 )/ T 0 }×100
wherein A represents a increase in thickness of the paper sheet substrate, T 0 represents a thickness of the paper sheet substrate before the immersion in water, and T 1 represents a thickness of the paper sheet substrate after the immersion in water.
3. The coated paper sheet as claimed in claim 1 , in which the paper sheet substrate has an apparent density in the range of 0.7 to 0.9 g/cm 3 , and satisfies the relationships (1) and (2):
Y 1≦61 X −34 (1)
Y 2≧−107 X + 123 (2)
wherein X represents an apparent density of 0.7 to 0.9 g/cm 3 of the paper sheet substrate, Y1 represents an air permeability of the paper sheet substrate determined in accordance with JIS P 8117 using Type B testing device, and Y2 represents a Clark stiffness of the paper sheet substrate determined in accordance with JIS P 8143, in the cross direction of the coated paper sheet.