Adhesives having microreplicated topography and methods of making and using same

Abstract

Adhesives having a microreplicated topography are prepared from contacting a microembossed pattern to a layer of adhesive. When an adhesion interface is established between the layer of adhesive and a supporting substrate, the topography of the adhesive surface controls the performance of the adhesion interface. Articles having microreplicated adhesive surfaces are also disclosed that have an advantage of providing microchannels for fluid egress for an effective period of time. Multiple microembossed patterns produce microreplicated adhesive surfaces having both microchannels for fluid egress and pegs for improved adhesive properties.

Description

[0001] This invention relates to adhesives having a controlled topographical surface of microchannels and the methods of making and using them.BACKGROUND OF INVENTION[0002] Pressure sensitive adhesives are useful for the joining of two materials. The interfaces between the adhesive and the materials are vital to the performance of the joined materials. The loss of adhesion at either interface can doom the usage of the materials.[0003] One example of an adhesion interface requiring peak performance is a durable film displaying image graphics adhered to substrates, where the film is a backing material upon which an adhesive layer is added for adhesion to the substrate. Adhesion of a large image graphic film to substrates encounters the problem of entrapped air between the film and the substrate. Anyone who has ever attempted to hang wallpaper can appreciate the frustration that can arise when entrapped air beneath an adhesive-backed film can not be removed easily. The most common solu...

AI Technical Summary

Benefits of technology

This solution enables controlled fluid egress and air bleeding from the adhesive interface, improving the installation process and maintaining the uniform appearance of the backing material, while ensuring effective adhesion and reducing manufacturing and labor costs.

Problems solved by technology

The loss of adhesion at either interface can doom the usage of the materials.

Adhesion of a large image graphic film to substrates encounters the problem of entrapped air between the film and the substrate.

Multiple attempts to adhere the same film to a substrate can compromise the pressure sensitive adhesive or increase the probability of uneven or misaligned film on the substrate.

The removal of air bubbles is also labor intensive.

This complicated procedure of generating the adhesion of the layer to the backing and then generating the adhesion to the final substrate minimizes utility of the construction for use in large format graphics and other industrial requirements.

(1) An adhesive without channels provides no effective route for egress of fluids in the X-Y dimensions of the interface between the adhesive and the substrate, especially if the backing material, adhesive, and / or the substrate are fluid-impermeable. But if the channels are too large, a path of fluid egress could also be a path of passive ingress of the same or other fluids.

(2) The backing material, and especially its outer imagable surface, can not be adversely affected by the adhesive topography chosen, thereby limiting the size of the channels in the adhesive and also limiting the method of construction. The backing material needs a flat, uniform surface for imaging and other aesthetic reasons. The formation of large channels into the laminate of backing and adhesive will adversely disrupt the flat, uniform surface of the backing material. Also, adhesive topographies that are too large will create undesired undulations or other imperfections in the appearance of the backing material on the final substrate. Such undulations or other imperfections make the image graphic unacceptable for most commercial markets.

(3) The area of adhesive actually contacting the substrate and the holding power (i.e., shear and peel adhesion) of the adhesive affect bonding performance of the backing material to the substrate. If either the holding power is too weak or the area of the adhesive contact is too small, or both, the performance of the adhesive is entirely inadequate. Microspheres or other large abrupt surface patterns have been used to reduce the area of adhesive surface on the substrate, either temporarily or permanently, which can affect holding power of the adhesive or area of adhesive contact. If the size of the surface features is increased, air channels in the topography are formed but there is insufficient adhesive interface remaining to provide effective permanent adhesion.

While the air bubble and fluid egress problems associated with large format graphics are easy to understand, these problems also exist for small graphics and decals where speed of application or applications without pre-masking are significant for economic or manufacturing considerations.

The problem of fluid egress is even more acute whenever the two materials contacting the adhesive effectively inhibit any egress in the Z axis through either or both materials.

Further if the materials are inflexible as well as fluid impermeable, such as metallic plates, there is no avenue that can be created, during application, for fluid egress.

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