Method for forming multilayer release liners and liners formed thereby

Abstract

Disclosed herein is a multilayer silicone release surface comprising a backing, a support layer on the backing, and a silicone layer of the support layer. The various layers of the multilayer release surface are deposited substantially simultaneously, as for example by a dual die or using curtain coating techniques.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS [0001] This application is a divisional of U.S. patent application Ser. No. 09 / 918,652, filed Mar. 22, 2000, which is a continuation-in-part of U.S. patent applicatin Ser. No. 09 / 389,167, filed Sep. 2, 1999, which is a continuation of U.S. patent application Ser. No. 08 / 616,859, filed Mar. 16, 1996, now issued as U.S. Pat. No. 5,962,075, which is a continuation-in-part of U.S. patent application Ser. No. 08 / 483,509, filed Jun. 7, 1995, now issued as U.S. Pat. No. 5,728,430, the entirety of each of which are incorporated by reference as if fully set forth herein.FIELD OF THE INVENTION [0002] The present invention generally relates to release surfaces of the type used with pressure-sensitive adhesive (PSA) constructions. More particularly, the present invention relates to multilayer release liners and their methods of manufacture. BACKGROUND OF THE INVENTION [0003] A pressure-sensitive adhesive construction, such as a label, generally comprises ...

AI Technical Summary

Benefits of technology

[0008] The present invention advantageously provides an efficient method of creating multilayer release liners, thereby overcoming the problems resulting from the prior art processes. The present invention achieves these benefits by providing a method of coating both a support layer and a release layer on a substrate substantially simultaneously. Consequently, separate coating steps are eliminated, and a corresponding savings in both time and costs are achieved.

[0009] Generally, these advantageous results may be achieved by at least two different coating methods. The first method achieves these results by modifying the die used to coat the support layer and a release layer (e.g., silicone layer) so that the die can dispense the fluids of both layers substantially simultaneously at a single coating station. The die dispenses the support layer onto the substrate, and substantially simultaneously, the release layer on the support layer. There is no need for a separate drying, hardening or curing step to prevent the layers from intermixing. By controlling the coating gap between the die and substrate, the processing conditions of the modified die may be optimized to achieve the most stable and efficient deposition of these layers. In some embodiments, application of controlled vacuum to the dual die coating process may be used to improve coating efficiency, increase coating tolerances and provide for less penetration of coated fluids onto the substrate to be coated. The multilayer release surfaces resulting from the simultaneous dual die coating of support layer and silicone-containing layer are also believed to have a unique morphology and advantageous properties.

[0010] Simultaneous coating of the support and release layers to form a multilayer release surface may also be achieved by curtain coating. For example, a slide coat die may be modified to have two slots, with the upper slot metering the release layer and the lower slot the support layer. The release layer and support layer combine on the die face surface, and fall to the moving substrate as a multilayer liquid sheet. The distance between the die and the substrate may range from 5 cm to 50 cm, and more preferably, from 10 cm to 30 cm. Advantageously, curtain coating techniques do not require as precise an optimization of the coating gap between the die and the substrate to generate high speed coatings, and high coating speeds are easily obtained.

Problems solved by technology

However, use of these high quality papers increases the cost of the end product adhesive construction, because such papers are typically much more expensive than regular open papers.

Growing concern over the environment has imposed stringent restrictions regarding recovery of the solvent used in applying the solvent based silicone to the high-holdout backing paper or other materials.

When applied to porous low cost papers, such as machine finished (MF) or machine glazed (MG) papers, these materials soak into the paper (penetrate the paper surface) to give ineffective coverage of the paper fibers unless excessively high quantities of expensive silicone are used.

Ineffective coverage of the paper fibers provides unsuitable release liners for PSA applications, especially where high speed convertibility is an essential performance feature.

However, there are several drawbacks to this prior art process.

First, additional costs are incurred because the prior art methods require two coating steps.

Otherwise, there is a potential for undesirable intermixing or destruction of the respective layers.

Second, because two separate coating steps are required, more time is needed for the overall formation of the release liner.

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