# US 2014/0193598 A1 · Multilayer Adhesive Film, in Particular for Bonding Optical Sensors > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2014/0193598 A1 - Document ID: US20140193598A1 - Status: Published application - Kind: A1 - Application number: 14/237,113 - Filed: 2012-08-08 - Published: 2014-07-10 - Earliest claimed: 2011-08-10 - Assignees: 3M Innovative Properties Company - Inventors: Steffen Traser; Jan D. Forster; Bernd Kuehneweg; Tobias Pick - Web page: https://patentgrep.com/patent/US20140193598A1 ## CPC - B32B 17/10: of synthetic resin - C09J 7/10: without carriers - C09J 133/02: Homopolymers or copolymers of acids; Metal or ammonium salts thereof - C09J 133/06: of esters containing only carbon, hydrogen and oxygen, the oxygen atom being present only as part of the carboxyl radical - C08L 2312/00: Crosslinking - C09J 2301/1242: the opposite adhesive layers being different - C09J 2301/208: the adhesive layer being constituted by at least two or more adjacent or superposed adhesive layers, e.g. multilayer adhesive - C09J 2301/312: parameters being the characterizing feature - C09J 2433/00: Presence of (meth)acrylic polymer - Y10T 428/1452: Polymer derived only from ethylenically unsaturated monomer - Y10T 428/24942: including components having same physical characteristic in differing degree - Y10T 428/24959: of adhesive layers - B32B: LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM - C09J: ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES (preparation of glue or gelatine C09H) - C08L: COMPOSITIONS OF MACROMOLECULAR COMPOUNDS (compositions based on polymerisable monomers C08F, C08G; artificial filaments or fibres D01F; textile treating compositions D06) - Y10T: TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION ## Abstract A multilayer pressure sensitive adhesive (PSA) film having a first acrylic pressure sensitive adhesive layer and an opposing second acrylic pressure sensitive adhesive layer, wherein the first pressure sensitive adhesive layer has a glass transition temperature Tg≧0° C. and a content of a strongly polar acrylate of 7.5 to 15 wt.-% in its precursor, and the second pressure sensitive adhesive layer has a Tg≦0° C. and contains 0.5 to 12 wt.-% of a strongly polar acrylate in its precursor, wherein the content of the strongly polar acrylate of the precursor of the first pressure sensitive adhesive layer exceeds the content of the strongly polar acrylate of the precursor of the second pressure sensitive adhesive layer by at least 2 wt.-% and wherein the Tg of the first pressure sensitive adhesive layer exceeds the Tg of the second pressure sensitive adhesive layer by at least 5° C. ## Claims ### Claim 1 A multilayer pressure sensitive adhesive (PSA) film having a first acrylic pressure sensitive adhesive layer and a second acrylic pressure sensitive adhesive layer, wherein the first pressure sensitive adhesive layer has a glass transition temperature Tg≧0° C. and a content of a strongly polar acrylate of 7.5 to 15 wt.-% in its precursor, in particular at least 10 wt.-%, and the second pressure sensitive adhesive layer has a Tg≦0° C. and contains 0.5 to 12 wt.-% of a strongly polar acrylate in its precursor, in particular up to 10 wt.-%, wherein the content of the strongly polar acrylate of the precursor of the first pressure sensitive adhesive layer exceeds the content of the strongly polar acrylate of the precursor of the second pressure sensitive adhesive layer by at least 2 wt.-% and wherein the Tg of the first pressure sensitive adhesive layer exceeds the Tg of the second pressure sensitive adhesive layer by at least 5° C. ### Claim 2 (depends on 1) The pressure sensitive adhesive film according to claim 1, wherein the strongly polar acrylate is chosen from the group comprising acrylic acid, methacrylic acid, itaconic acid, hydroxyalkyl acrylates, acrylamides and substituted acrylamides or mixtures thereof. ### Claim 3 (depends on 1) The pressure sensitive adhesive film according to claim 1, wherein the precursor of the first pressure sensitive adhesive layer has a content of the strongly polar acrylate of 10 to 13 wt.-%, in particular from 10 to 12.5 wt.-%. ### Claim 4 (depends on 1) The pressure sensitive adhesive film according to claim 1, wherein the film is substantially free of filler particles, cavities in the form of microspheres, expendable microspheres, in particular pentane filled expendable microspheres or gaseous cavities, glassbeads, glass microspheres, (hydrophobic/hydrophilic) silica type fillers, fibers, electrically and/or thermally conducting particles, nano particles. ### Claim 5 (canceled) ### Claim 6 (depends on 1) The pressure sensitive adhesive film according to claim 1, wherein the ratio of layer thickness of the second acrylic pressure sensitive adhesive layer to the first acrylic pressure sensitive adhesive layer ranges from 1:1 to 15:1, in particular from 3:1 to 10:1. ### Claim 7 (depends on 1) The pressure sensitive adhesive film according to claim 1, wherein the thickness of the film is from 1.0 mm to 5.0 mm, in particular from 1.5 to 3.0 mm. ### Claim 8 (depends on 1) The pressure sensitive adhesive film according to claim 1, wherein the first pressure sensitive adhesive layer is provided on both major surfaces of the second pressure sensitive adhesive layer or the second pressure sensitive adhesive layer is provided on both major surfaces of the first pressure sensitive adhesive layer. ### Claim 9 (depends on 1) The pressure sensitive adhesive film according to claim 1, wherein at least one intermediate layer is present between the first and second pressure sensitive adhesive layers. ### Claim 10 A continuous self-metered process of forming a multilayer pressure sensitive adhesive film comprising at least two polymer layers with a first acrylic pressure sensitive adhesive layer and a second acrylic pressure sensitive adhesive layer, the process comprising the steps of: (i) providing a substrate (4); (ii) providing two or more coating knives (2, 3) which are offset, independently from each other, from said substrate (4) to form a gap normal to the surface of the substrate (4); (iii) moving the substrate (4) relative to the coating knives (2, 3) in a downstream direction (5), (iv) providing curable liquid precursors of the polymers to the upstream side of the coating knives (2, 3) thereby coating the two or more precursors through the respective gaps as superimposed layers (9, 10) onto the substrate (4); (v) optionally providing one or more solid films (8) and applying these essentially simultaneously with the formation of the adjacent lower polymer layer, and (vi) curing the precursor of the multilayer film thus obtained; wherein a lower layer of a curable liquid precursor is covered by an adjacent upper layer of a curable liquid precursor or a film, respectively, wherein the precursor of the first pressure sensitive adhesive layer has a content of a strongly polar acrylate of 7.5 to 15 wt.-%, in particular at least 10 wt.-%, and the precursor of the second pressure sensitive adhesive layer has a content of a strongly polar acrylate of 0.5 to 12 wt.-%, in particular up to 10 wt.-%, wherein the content of the strongly polar acrylate of the precursor of the first pressure sensitive adhesive layer exceeds the content of the strongly polar acrylate of the precursor of the second pressure sensitive adhesive layer by at least 2 wt.-% and wherein after the curing step (vi) the first pressure sensitive adhesive layer has a glass transition temperature Tg≧0° C. and the second pressure sensitive adhesive layer has a Tg≦0° C. and the Tg of the first pressure sensitive adhesive layer exceeds the Tg of the second pressure sensitive adhesive layer by at least 5° C. ### Claim 11 (depends on 10) The process according to claim 10, wherein the liquid precursors are applied under ambient pressure or an over-pressure. ### Claim 12 (depends on 10) The process according to claim 10, wherein the liquid precursors of the polymer material are provided in one or more coating chambers (6) essentially abutting each other and being bordered in downstream direction by a front wall, optionally one or more intermediate walls and a back wall, and, optionally, by a rolling bead positioned up-web relative to the front wall, whereas in particular the upstream intermediate walls, the back wall and, if a rolling bead is present upstream relative to the front wall, the front wall are formed by coating knives (2, 3). ### Claim 13 (depends on 10) The process according to any of the claim 10, wherein the solid films (8) are attached to form the lowest layer and/or the topmost layer and/or an intermediate layer of the precursor of the multilayer film. ### Claim 14 (depends on 10) The process according to any of the claim 10, wherein at least the exposed surface of the substrate (4) and/or at least one surface of a solid film (8) facing the precursor of the multilayer film, is a release surface. ### Claim 15 (depends on 10) The process according to any of the claim 10, wherein the substrate (4) forms an integral part of the multilayer film subsequent to the curing step. ### Claim 16 (depends on 10) The process according to any of the claim 10, wherein the precursor layers are cured thermally and/or by exposing them to actinic radiation after they have passed the back wall of a coating apparatus (1). ### Claim 17 (depends on 10) The process according to any of the claim 10, wherein at least one of the precursors comprises at least one compound having a radiation curable ethylene group. ### Claim 18 (depends on 10) The process according to any of the claim 10, wherein the liquid precursors have a Brookfield viscosity of at least 1,000 mPa·s at 25° C. ### Claim 19 (depends on 10) A pressure sensitive adhesive film obtainable by the process according to claim 10. ### Claim 20 (depends on 19) The pressure sensitive adhesive film according to claim 19, wherein the film is light-transmissive whereas each of the layers has a transmission of at least 80% relative to visible light wherein the multilayer film exhibits a transmission relative to visible light which is higher than the transmission of a comparative multilayer film obtained by a method differing from the above method in that the release liner is attached to the exposed surface of the top layer surface at a position downstream to the formation of the top layer of the precursor of the multilayer film. ### Claim 21 (depends on 20) The pressure sensitive adhesive film according to claim 20, wherein the ratio of the transmission of the multilayer film over the transmission of the comparative multilayer film is at least 1.002. ### Claim 22 (depends on 1) An assembly comprising a substrate having a surface energy of >40 mJ/m2 or more, in particular a glass substrate, and a pressure sensitive adhesive film according to claim 1, wherein the pressure sensitive adhesive film is attached to the substrate surface with its first pressure sensitive adhesive layer. ### Claim 23 (depends on 22) The assembly according to claim 22, wherein when subjecting the film to stretching force mostly parallel to the substrate surface so that a 5% elongation of the film is achieved with an stretching speed of 10% per minute, no bubbles occur at the interface between the substrate and the film within 24 h after the film is stretched to 5% elongation. ### Claim 24 (depends on 1) The pressure sensitive adhesive film according to claim 1, wherein that the content of the strongly polar acrylate in the precursor of the second pressure sensitive adhesive layers is from 5 to 10 wt.-%, in particular from 7.5 to 10 wt.-%. ### Claim 25 (depends on 1) The pressure sensitive adhesive film according to claim 1, wherein that the content of the strongly polar acrylate of the precursor of the first pressure sensitive adhesive layer exceeds the content of the strongly polar acrylate of the precursor of the second pressure sensitive adhesive layer by at least 2 to 5 wt.-%, in particular by at least 2.5 wt.-%.