Abstract: A novel method for measurement of dynamic water break resistance capable of predicting a degree of paper-cutting at the time of an offset printing and an apparatus for carrying out this method are provided. Both ends of a specimen paper having a size of short-side of from 3 to 15 mm and a long-side of from 120 to 320 mm are kept by a fixed chuck and a movable chuck positioned with a fixed spun length on a measurement table; from 1 to 30 .mu.l of water is attached from a device unit for automatically attaching water onto a central portion of the specimen paper; after the attachment of water, a load is rapidly applied from the both ends of the specimen paper to measure a tensile strength of the specimen paper at the time of attachment of water; and a tensile strength of the specimen paper at the time of drying, i.e.

Abstract: Printing paper such as newspaper printing paper, the water absorbency of which is controlled by coating material for controlling water absorbency on the surface of base paper, wherein the coating material contains component A which is at least one water-soluble polyacrylamide selected from nonionic polyacrylamides, cationic polyacrylamides, and water-soluble polyacrylamides, and component B which is water-soluble anionic polymers of monomers having hydrophobic substitute(s) and monomers having at least carboxyl group(s) or sulfone group(s).

Abstract: In a thermal recording material having a thermal recording layer containing a colorless or pale colored dye precursor and a color developer reactable with the dye precursor upon heating to develop a color of the dye precursor, the color developer is a bisurea compound, for example, Compound A-2. The thermal recording material is superior in stability of background color.

Abstract: In an optical recording sheet having a thermal recording layer containing a colorless or pale colored dye precursor and a color developer reactable with the dye precursor upon heating to develop a color, a dimerized or trimerized urea compound is used as the color developer to obtain an optical recording sheet which is superior in ground color stability and an optical recording sheet having a reversible recordability.

Abstract: In a thermal recording sheet having a thermal recording layer containing a colorless or pale colored dye precursor and a color developer reactable with the dye precursor upon heating to develop a color, a dimerized or trimerized urea compound is used as the color developer to obtain a thermal recording sheet which is superior in ground color stability and a thermal recording sheet having a reversible recordability.