High gloss coated paper

Abstract

A coated paper product having high gloss and brightness is prepared by a process wherein a paper substrate is coated on at least one side with an aqueous coating formulation comprising an effective amount of a plastic pigment, and finished in a supercalender device containing heated rolls to produce a surface which is comparable to a cast coated surface.

Description

BACKGROUND OF INVENTION[0001] The present invention relates generally to a coated paper product having high gloss and brightness and the method of manufacturing such a product. In particular, the invention relates to a process for manufacturing a coated paper product with a surface comparable to a cast coated surface, that may be used, for example, as the facing sheet of a pressure sensitive laminate. In addition to this intended use, the product of the present invention is suitable for a variety of other printing and converting operations such as metallizing, foil laminating and printing, security label applications and, specialty packaging as well as upscale gift wrap and labels.[0002] Such paper products have in the past been produced almost exclusively by a cast coating process. During cast coating, gloss development relies on a replication of the mirror-like finish on a dryer roll, as the applied coating is dried. However, production rates for the cast coating process are consi...

AI Technical Summary

Benefits of technology

[0007] The coatings disclosed herein for practicing the present invention include conventional inorganic pigments such as clay and calcium carbonate in conjunction with elevated amounts of thermoplastic polymer latex beads. The beads are either hollow or solid in composition. Upon applying these coatings onto an uncoated but smoothened basestock, or onto a precoated basestock, it is possible to achieve a high gloss and smoothness with good printing properties when the coated surface is finished in a calendar device such as a supercalender containing heated rolls.

[0010] In addition, the size of the plastic pigment plays a role in the performance of the coating, vis-a-vis gloss development. For example, paper gloss achieved with a 0.45 micron diameter solid sphere plastic pigment is not as good as that obtained with a hollow sphere plastic pigment when the percent of surface area is taken into consideration. It is postulated that this ineffectiveness may be related to the diameter and curvature of the sphere presented to incoming light and subsequent light scattering. For example, five 0.45 micron diameter solid spheres will occupy approximately the same space as a 1.0 micron diameter hollow sphere. However, hollow spheres can flatten upon calendering and create a plurality of multiple flat surfaces for more efficient light reflection and gloss development. Meanwhile, the use of a 0.20 micron diameter solid sphere plastic pigment will more closely simulate a flatter surface than the 0.45 micron diameter spheres because approximately twenty five 0.20 micron diameter spheres will occupy the same space as a single 1.0 micron diameter hollow sphere.

Problems solved by technology

However, production rates for the cast coating process are considerably slower than the production of coated paper on a high speed papermachine.

However, in the latter case, the glossy surface produced is not generally useful for offset printing because of the excessive ink drying time required.

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