The present invention provides a novel pressure-sensitive adhesive label which curls little even under the coldest conditions and which has as a surface material a microporous stretched resin film obtained by stretching a crystalline polyolefin resin film containing an inorganic fine powder, a pressure-sensitive adhesive layer provided on one side of the surface material and a release paper provided on the pressure-sensitive adhesive layer, where the microporous stretched resin film satisfies the following physical properties (1) and (2): (1) the linear thermal expansion coefficient in a machine direction at -10.degree. C. (JIS K-7197) is from 10 to 70 .mu.m/m.multidot..degree.C.; and (2) the linear thermal expansion coefficient in the machine direction at 0.degree. C. is from 10 to 75 .mu.m/m.multidot..degree.C.

This invention provides polypropylene-based resin-coated paper using paper as substrate and having excellent smoothness, especially the one which, when used for printing or heat transfer recording, keeps free from formation of white dots and occurrence of density unevenness in images, and thus is suited for printing use or heat transfer recording use. At least one side of the paper substrate is coated with a resin. The paper used as substrate is characterized by the fact that the unevenness in film thickness in machine direction (unevenness index) as measured by a film thickness meter is less than a specified value. The resin used for coating is a compounded resin composition comprising a polyethylene-based resin and a random polypropylene-based resin obtained by randomly copolymerizing principally ethylene and propylene, with the ethylene proportion being in a specified range, wherein the ratio by weight of the polyethylene-based resin to the random polypropylene-based resin is in a specified range, and the composition has been subjected to at least one round of kneading.

A porous resin film which comprises 30 to 90 wt % of a thermoplastic resin containing a hydrophilic thermoplastic resin component; and 70 to 10 wt % of an inorganic or organic fine powder was disclosed. The porous resin film of the present invention is valuable as an ink-jet recording medium since the film shows excellent ink absorbing and drying properties even when a large amount of ink is discharged thereon, and thus can produce thereon a high-definition image.

A process which combines a calender with a stretching system and a set of heating rolls is provided in this invention to produce films of polypropylene resin of wide thickness range. The polypropylene films which have cavities distributed in the film and on the surfaces are suitable for writing or printing and have a low density. The films have surface qualities of each side of surface within .+-.2.times.10.sup.-6 inch of the average depth of the cavities, .+-.2% of the average of the gloss at 45.degree. angle and .+-.0.02 of the average of coefficient of friction. Such a film is obtained by passing the molded film from the calender through a set of heating rolls at temperatures revealed in this invention before entering the stretching system. The obtained polypropylene film has superior printability, low density and high stiffness, and thus is suitable for use as a paper substitute.

Polypropylene films which have cavities distributed in the film and on the surfaces are suitable for writing or printing and have a low density. The films have surface qualities of each side of surface within .+-.2.times.10.sup.-6 inch of the average depth of the cavities, .+-.2% of the average of the gloss at 45.degree. angle and .+-.0.02 of the average of coefficient of friction. Such a film is obtained by passing the molded film from the calender through a set of heating rolls at temperatures revealed in this invention before entering the stretching system. The obtained polypropylene film has superior printability, low density and high stiffness, and thus is suitable for use as a paper substitute.