WO2022104499A1

WO2022104499A1 - Electrically conductive multilayer stack and hollow gasket including same

Info

Publication number: WO2022104499A1
Application number: PCT/CN2020/129275
Authority: WO
Inventors: Su Zhang; Jie Huang; Xuetao YU; Jing Fang; Bing Huang
Original assignee: 3M Innovative Properties Company; Su Zhang
Priority date: 2020-11-17
Filing date: 2020-11-17
Publication date: 2022-05-27
Also published as: CN220711937U

Abstract

An electrically conductive multilayer stack(100) includes a first polymeric layer(110), an electrically conductive layer(120) bonded to a first side(112) of the first polymeric layer(110), and a second polymeric layer(130) disposed on an opposite second side(114) of the first polymeric layer(110). The first and second polymeric layers(110, 130) and the electrically conductive layer(120) are substantially coextensive with one another. When the multilayer stack(100) is wound to form a flexible closed loop(200) with the electrically conductive layer(120) forming an outside layer of the closed loop(200), the closed loop(200) regains at least about 80% of its initial diameter after a force compressing the closed loop(200) across the initial diameter by at least about 80%is removed, and the closed loop(200) regains at least about 70%of its initial diameter after a compression force per unit length of the loop(200) of about 0.8 kgf/cm compressing the closed loop(200) across the initial diameter is removed.

Description

ELECTRICALLY CONDUCTIVE MULTILAYER STACK AND HOLLOW GASKET INCLUDING SAME

Background

Electronic devices may use conductive gaskets to form electrical paths between opposing conductive structures.

Summary

The present description relates generally to multilayer stacks that can be used to form hollow gaskets for providing an electrical path between two conductive surfaces.

In some aspects of the present description, an electrically conductive multilayer stack for providing an electrical path between two conductive surfaces is provided. The multilayer stack includes a first polymeric layer; an electrically conductive layer bonded to a first side of the first polymeric layer; and a second polymeric layer disposed on an opposite second side of the first polymeric layer. The first and second polymeric layers and the electrically conductive layer are substantially coextensive with one another. When the multilayer stack is wound to form a flexible closed loop with the electrically conductive layer forming an outside layer of the closed loop: the closed loop regains at least about 80%of its initial diameter after a force compressing the closed loop across the initial diameter by at least about 80%is removed; and the closed loop regains at least about 70%of its initial diameter after a compression force per unit length of the closed loop of about 0.8 kgf/cm compressing the closed loop across the initial diameter is removed. In some embodiments, the closed loop regains at least about 90%of its initial diameter after a force compressing the closed loop across the initial diameter by at least about 80%is removed.

In some aspects of the present description, an electrically conductive multilayer stack for providing an electrical path between two conductive surfaces is provided. The multilayer stack includes a first polymeric layer extending along a first direction between opposing end portions of the first polymeric layer where the first direction is orthogonal to a thickness direction of the multilayer stack; an electrically conductive layer bonded to a first side of the first polymeric layer; a second polymeric layer disposed on an opposite second side of the first polymeric layer. The first and second polymeric layers and the electrically conductive layer are substantially coextensive with one another. The second polymeric layer extends along the first direction between opposing end portions of the second polymeric layer. The first and second polymeric layers are attached to one another only along the end portions of the first and second polymeric layers. When the multilayer stack is wound to form a flexible closed loop with the electrically conductive layer forming an outside layer of the closed loop and with the end portions of the first polymeric layer overlapping one another, the closed loop regains at least about 80%of its initial diameter after a force compressing the closed loop across the initial diameter by at least about 80%is removed. In some embodiments, the closed loop regains at least about 90%of its initial diameter after a force compressing the closed loop across the initial diameter by at least about 80%is removed and/or the closed loop regains at least about 70%of its initial diameter after a compression force per unit length of the closed loop of about 0.8 kgf/cm compressing the closed loop across the initial diameter is removed.

In some aspects of the present description, an electrically conductive multilayer stack for providing an electrical path between two conductive surfaces is provided. The multilayer stack includes a first polymeric layer; an electrically conductive layer bonded to a first side of the first polymeric layer; a pressure sensitive adhesive layer disposed on an opposite second side of the first polymeric layer and being substantially coextensive with the first polymeric layer and the electrically conductive layer; and powder disposed on a first major surface of the pressure sensitive adhesive layer facing away from the first polymeric layer to reduce tack of the pressure sensitive adhesive layer, such that when the multilayer stack is wound to form a flexible closed loop with the electrically conductive layer forming an outside layer of the closed loop, the closed loop regains at least about 80%of its initial diameter after a force compressing the closed loop across the initial diameter by at least about 80%is removed. In some embodiments, the closed loop regains at least about 90%of its initial diameter after a force compressing the closed loop across the initial diameter by at least about 80%is removed and/or the closed loop regains at least about 70%of its initial diameter after a compression force per unit length of the closed loop of about 0.8 kgf/cm compressing the closed loop across the initial diameter is removed.

These and other aspects will be apparent from the following detailed description. In no event, however, should this brief summary be construed to limit the claimable subject matter.

Brief Description of the Drawings

FIGS. 1A-1D are schematic cross-sectional views of electrically conductive multilayer stacks, according to some embodiments.

FIG. 1E is a schematic cross-sectional view of an electrically conductive layer bonded to a polymeric layer, according to some embodiments.

FIG. 2A is a schematic cross-sectional view of a multilayer stack wound to form a flexible closed loop, according to some embodiments.

FIG. 2B is a schematic cross-sectional view of the flexible closed loop of FIG. 2A after it has been compressed across its diameter.

FIG. 2C is a schematic cross-sectional view of the flexible closed loop of FIG. 2B after it has been further compressed across its diameter.

FIG. 2D is a schematic cross-sectional view of end portions of a multilayer stack wound to form a loop, according to some embodiments.

FIGS. 3A-3B are schematic top views of hollow gaskets, according to some embodiments.

FIGS. 4-5 are schematic cross-sectional views of hollow gaskets formed by winding multilayer stacks, according to some embodiments.

FIG. 6A is a schematic cross-sectional view of a hollow gasket formed by bending a multilayer stack, according to some embodiments.

FIG. 6B is a schematic cross-sectional view of the hollow gasket of FIG. 6A after it has been compressed across its diameter.

FIG. 7 is a schematic cross-sectional view of an electronic device including a compressed cylinder, according to some embodiments.

FIG. 8 is a schematic cross-sectional view of an electronic device including two compressed cylinders, according to some embodiments.

Detailed Description

In the following description, reference is made to the accompanying drawings that form a part hereof and in which various embodiments are shown by way of illustration. The drawings are not necessarily to scale. It is to be understood that other embodiments are contemplated and may be made without departing from the scope or spirit of the present description. The following detailed description, therefore, is not to be taken in a limiting sense.

Electronic devices may use conductive gaskets to form electrical paths between opposing conductive structures as generally described in U.S. Pat. No. 9,119,285 (Tarkington et al. ) , for example. According to some embodiments of the present description, a conductive gasket may be made from a multilayer stack having a layer structure that provides improved recovery after a force compressing the gasket is removed compared to conventional conductive gaskets.

It may be desired that a conductive gasket recovers most of its initial diameter after being compressed by a specified fraction of its initial diameter, or after being compressed by a specified force per unit length of the gasket, or both. However, it has been found that conventional conductive closed loop gaskets cannot simultaneously achieve a high recovery after being compressed a large fraction of its initial diameter (e.g., the closed loop regains at least about 80%of its initial diameter after a force compressing the closed loop across the initial diameter by at least about 80%is removed) and a high recovery after a substantial force has compressed the closed loop (e.g., the closed loop regains at least about 70%of its initial diameter after a compression force per unit length of the closed loop of about 0.8 kgf/cm compressing the closed loop across the initial diameter is removed) . According to some embodiments of the present description, both of these recovery attributes are achieved. A hollow gasket can be formed by winding an electrically conductive multilayer stack in the shape of a flexible closed loop. According to some embodiments, it has been found that desired recovery properties can be achieved by using first and second polymeric layers behind a conductive layer in a multilayer stack where the first and second polymeric layers are attached to one another only along opposing end portions of the first and second polymeric layers such that when the multilayer stack is wound to form the flexible closed loop, the end portions of at least the first polymeric layer overlap one another. According to some embodiments, it has been found that desired recovery properties can be achieved by using a polymeric layer between a conductive layer and a pressure sensitive adhesive layer in a multilayer stack where the pressure sensitive adhesive layer is not used for bonding to another layer, but is instead used for its mechanical properties which have been found to provide desired recovery properties for the closed loop formed by the multilayer stack. In some embodiments, powder is disposed on the major surface of the pressure sensitive adhesive layer facing away from the conductive layer to reduce tack.

FIGS. 1A-1D are schematic cross-sectional views of illustrative electrically conductive multilayer stacks 100, 100’, 100”, 100”’, respectively, which may be used for providing an electrical path between two conductive surfaces (e.g., after forming a closed loop or hollow gasket from the multilayer stack) . The

multilayer stack

100, 100’, 100”, 100”’ includes a first polymeric layer 110; an electrically conductive layer 120 bonded to a first side 112 of the first polymeric layer 110; and a layer 130 disposed on an opposite second side 114 of the first polymeric layer 110. The first polymeric layer 110, the layer 130 and the electrically conductive layer 120 may be substantially coextensive with one another. The layer 130 may be a second polymeric layer and/or may be a pressure sensitive adhesive layer.

Layers can be described as substantially coextensive with each other if at least about 60%by area of each layer is coextensive with at least about 60%by area of each other layer. In some embodiments, for layers describes as substantially coextensive, at least about 70%, or at least about 80%, or at least about 90%by area of each layer is coextensive with at least about 70%, or at least about 80%, or at least about 90%by area of each other layer.

In some embodiments, as schematically illustrated in FIG. 1B, the layer 130 is a pressure sensitive adhesive, which may be substantially coextensive with the first polymeric layer 110 and the electrically conductive layer 120, and the multilayer stack 100’ includes powder 128 disposed on a first major surface 127 of the pressure sensitive adhesive layer 130 facing away from the first polymeric layer 110 to reduce tack of the pressure sensitive adhesive layer 130. The powder may partially sink into the pressure sensitive adhesive layer 130. It has been found that using a pressure sensitive adhesive results in desired recovery properties. The pressure sensitive adhesive may be any suitable pressure sensitive adhesive (e.g., an acrylate-based pressure sensitive adhesive) and typically satisfies the Dahlquist criterion (storage shear modulus G' less than 0.3 MPa) . In some embodiments, the pressure sensitive adhesive layer 130 has a storage shear modulus G' less than about 0.1 MPa. In some embodiments, the power 128 is disposed to reduce tack of at least about 60%of a total area of the first major surface 127 of the pressure sensitive adhesive layer 130. For example, the powder can prevent a spherical object having a diameter of about 1 cm from contacting the first major surface 127 over at least about 60%of the total area of the first major surface 127. In some embodiments, the power 128 is disposed to reduce tack of at least about 70%, or at least about 80%, or at least about 90%of the total area of the first major surface 127 of the pressure sensitive adhesive layer 130.

According to some embodiments, it has been found that using a thicker pressure sensitive adhesive layer can result in improved recovery properties. In some embodiments, an average thickness t2 of the pressure sensitive adhesive layer 130 is greater than an average thickness t1 of the first polymeric layer 110. In some embodiments, t2 is at least about 1.2, or at least about 1.5, or at least about 2, or at least about 2.5, or at least about 3 times t1. In some such embodiments, or in other embodiments, t2 is no more than about 10 times t1, or no more than about 7 times t1. For example, t2 may be in a range of about 2 to about 7 times t1.

In some embodiments, an additional polymeric layer is bonded to the pressure sensitive adhesive layer opposite the first polymeric layer 110. However, it has been found that including such an additional layer can be detrimental to the recovery properties of the loop or gasket formed from the multilayer stack. When such an additional layer is included it is typically preferred that the layer has a low modulus and/or is thin (e.g., thinner than the first polymeric layer 110 and/or thinner than the adhesive layer) . In some embodiments, as schematically illustrated in FIG. 1C, the layer 130 is a second polymeric layer, which may be a non-adhesive low-modulus layer, and the multilayer stack 100” includes a pressure sensitive adhesive layer 125 bonding together, and substantially coextensive with, the first and second and second

polymeric layers

110 and 130. In some embodiments, a Young’s modulus E1 (see, e.g., FIG. 1A) of the first polymeric layer 110 is greater than a Young’s modulus E2 of the second polymeric layer 130. In some embodiments, a Young’s modulus E1 of the first polymeric layer 110 is at least 30%, or at least 50%, or at least 80%, or at least 100%, or at least 150%, or at least 200%, or at least 250%greater than a Young’s modulus E2 of the second polymeric layer. The Young’s modulus can be determined according to Method A of the ASTM D412-16 test standard, for example.

In some embodiments, the first and second

polymeric layers

110 and 130 are bonded to one another with a pressure sensitive adhesive layer 130 substantially coextensive with the first and second

polymeric layers

110 and 130, where the second polymeric layer 130 has a Young’s modulus less than about 0.3 times, or less than about 0.2 times, or less than about 0.1 times a Young’s modulus of the first polymeric layer 110. In some such embodiments, or in other embodiments, the second polymeric layer 130 is or includes an elastomer. For example, the first polymeric layer 110 may be or include polyethylene terephthalate (PET) , while the second polymeric layer 130 may be or include thermoplastic polyester elastomer (TPEE) . Using computer simulations of multilayer stacks including a 20 micrometer thick PET layer bonded to various 20 micrometer thick polymeric backing layers with a 10 micron thick pressure sensitive adhesive, it has been found that a low modulus TPEE backing layer gives significantly improved recovery compared to higher modulus backing layers.

In some embodiments, the first polymeric layer 110 includes polyethylene terephthalate (PET) or polyimide. In some such embodiments, or in other embodiments, the second polymeric layer 130 includes polyvinylchloride (PVC) , latex, nitrile, polypropylene, polyethylene (e.g., high-density polyethylene (HDPE) or low-density polyethylene (LDPE) ) , or thermoplastic polyester elastomer (TPEE) . In some such embodiments, or in other embodiments, the second polymeric layer 130 includes polyvinylchloride (PVC) , latex, nitrile, low-density polyethylene (e.g., density in the range of 917-930 kg/m ³) , or thermoplastic polyester elastomer (TPEE) . In some embodiments, the second polymeric layer 130 is a PVC layer having a Young’s modulus less than about 0.5 MPa, or less than about 0.1 MPa, for example. In some embodiments, the second polymeric layer 130 is a nitrile layer having a Young’s modulus less than about 4 MPa, or less than about 3 MPa, or less than about 2 MPa, for example. In some embodiments, the second polymeric layer 130 is a latex layer having a Young’s modulus less than about 5 MPa, or less than about 3 MPa, for example. In some embodiments, the second polymeric layer 130 is a TPEE layer having a Young’s modulus less than about 350 MPa, or less than about 300 MPa, for example. In some embodiments, the second polymeric layer 130 is a LDPE layer having a Young’s modulus less than about 300 MPa, or less than about 270 MPa, for example. It has been found that such soft layers (compared to PET, for example, which has a Young’s modulus greater than about 2 GPa) give significantly improved recovery compared to higher modulus backing layers when the layer is bonded to the first polymeric layer 110 with a pressure sensitive adhesive. In some embodiments, the second polymeric layer 130 includes polyvinylchloride (PVC) , latex or nitrile and has a Young’s modulus less than about 5 MPa. In some embodiments, the second polymeric layer 130 is an adhesive layer which may be a pressure sensitive adhesive layer (PSA) such as an acrylate-based PSA. In some embodiments, the electrically conductive layer 120 is a metal layer. In some embodiments, the electrically conductive layer 120 includes one or more of copper, nickel, silver, aluminum, gold, indium tin oxide (ITO) , and tin.

In some embodiments, as schematically illustrated in FIG. 1D, for example, the first polymeric layer 110 extends along a first direction (e.g., the x-direction of FIG. 1D or a direction along a circumference of a closed loop when the multilayer stack is wound into the closed loop) between opposing

end portions

111 and 113 of the first polymeric layer 110 and the layer 130 is a second polymeric layer extending along the first direction between opposing

end portions

131 and 133 of the second polymeric layer. The first direction is orthogonal to the thickness direction (e.g., z-direction of FIG. 1D) of the multilayer stack. The multilayer stack can have a length along the first direction that is at least 10 times (e.g., 10 to 10 ⁶ times) a thickness of the multilayer stack. An end portion of a layer can be understood to be a portion of the layer that is closer to an end of the layer than to a center of the layer along the first direction. An end portion of a layer having a length L0 along the first direction may have a length L1 or L2 along the first direction that is less than about 0.25, or less than about 0.2, or less than about 0.15, or less than about 0.1 times the length L0. In some embodiments, for each layer of the first and second

polymeric layers

110 and 130, the layer has a length L0 along the first direction, where each end portion has a length (e.g., L1, L2) along the first direction of less than 0.2 times the length L0 of the layer. In some embodiments, the first and second

polymeric layers

110 and 130 are attached to one another only along the opposing end portions of the first and second

polymeric layers

110 and 130. Adhesive strips 124 and 126 (e.g., extending in the y-direction) may be used to bond the opposing end portions of the first and second

polymeric layers

110 and 130 together. The adhesive strips may have a length along the first direction about equal to the length (e.g., L1, L2) of the end portions of the first and second

polymeric layers

110 and 130. When the multilayer stack 100”’ is wound to form the flexible closed loop 200 described elsewhere herein (see, e.g., FIGS. 2A-2C) with the electrically conductive layer forming an outside layer of the closed loop, the loop can be wound such that the end portions of the first polymeric layer overlap one another. The end portions of the second polymeric layer typically also overlap one another (e.g., the loop can be wound such that the end portions of each of the first and second polymeric layers overlap one another) . For example, as schematically illustrated in FIG. 2D which shows portions of a multilayer stack in an overlap region of a closed loop, the

end portions

111 and 113 of the first polymeric layer 110 overlap one another and the

end portions

131 and 133 of the second polymeric layer 130 overlap one another. In the closed loop, each end portion of the first and second

polymeric layers

110 and 130 may overlap each other end portion of the first and second

polymeric layers

110 and 130 as schematically illustrated in FIG. 2D, for example.

The electrically conductive layer 120 may be bonded to the first polymeric layer 110 by virtue of having been formed on the first polymeric layer 110. In some embodiments, the electrically conductive layer 120 is electrodeposited (e.g., directly) onto the first polymeric layer 110. In some embodiments, the electrically conductive layer 120 is bonded to the first polymeric layer 110 via an adhesive layer 115 as schematically illustrated in FIG. 1E. In some embodiments, the electrically conductive layer 120, the adhesive layer 115 and the first polymeric layer are substantially coextensive with each other.

In some embodiments, when the

multilayer stack

100, 100’, 100”, 100”’ is wound to form a flexible closed loop 200 (see, e.g., FIGS. 2A-2C) with the electrically conductive layer 120 forming an outside layer of the closed loop 200: the closed loop 200 regains at least about 80%of its initial diameter after a force compressing the closed loop 200 across the initial diameter by at least about 80% (e.g., about 80%or about 85%) is removed; and/or the closed loop 200 regains at least about 70%of its initial diameter after a compression force per unit length of the closed loop (length in y-direction referring to the x-y-z coordinate system of FIGS. 2A-2C) of about 0.8 kgf/cm compressing the closed loop across the initial diameter is removed. In some such embodiments, or in other embodiments, the closed loop 200 regains at least about 85%, or at least about 90%of its initial diameter after a force compressing the closed loop 200 across the initial diameter by at least about 80%is removed. In some such embodiments, or in other embodiments, the closed loop 200 regains at least about 80%, or at least about 85%, or at least about 90%of its initial diameter after a force compressing the closed loop 200 across the initial diameter by at least about 85%is removed.

FIG. 2A is a schematic cross-sectional view of the multilayer stack 300 (e.g., corresponding to any of

multilayer stacks

100, 100’, 100”, or 100”’ or other multilayer stacks described elsewhere herein) wound to form a flexible closed loop 200 having an outside diameter D0 with the conductive layer 120 forming an outside layer of the loop 200. In some embodiments, the outside diameter D0 is no more than about 25 mm, or no more than about 20 mm, or no more than about 15 mm, or no more than about 12 mm. In some such embodiments, or in other embodiments, the outside diameter D0 is at least about 0.2 mm, or at least about 0.5 mm, or at least about 1 mm, or at least about 2 mm, or at least about 3 mm, or at least about 4 mm. In some embodiments, the outer diameter D1 is in a range from any one of these lower limits to any one of these upper limits. FIG. 2B schematically illustrates the flexible closed loop 200 after it has been compressed across the diameter to a smaller outer diameter D1. FIG. 2C schematically illustrates the flexible closed loop 200 after it has been further compressed across the diameter to an even smaller outer diameter D1’. D0 may be compressed (e.g., by a force F (or F’) as schematically illustrated in FIG. 2B (or FIG. 2C) ) to D1 (or D1’) by at least about 20% ( (D0-D1) /D0*100%at least about 20%) , or at least about 50%, or at least about 60%, or at least about 70%, or at least about 80%, or at least about 85%, or at least about 90%, or in a range between any two of these compressions (e.g., in a range from about 20%to about 50%) . FIG. 2D is schematic cross-sectional view of portion of a closed loop formed from the multilayer stack 100”’ in a region of the closed loop where opposite ends of the multilayer stack 100”’ overlap each other.

In some embodiments, when the multilayer stack 300 is wound to form the flexible closed loop 200 having the outside diameter D0 with the conductive layer 120 forming an outside layer of the loop 200, an electrical resistance of the closed loop 200 across a diameter of the closed loop remains less than about 2 Ω when the loop is compressed across the diameter by at least 20%. In some embodiments, the resistance of the closed loop 200 across a diameter of the closed loop remains less than about 1 Ω, or less than about 0.5 Ω, or less than about 0.4 Ω, or less than about 0.3 Ω when the loop is compressed across the diameter by at least 20%. In some embodiments, the resistance of the closed loop across the diameter of the closed loop changes by less than about 50%when the compression of the loop is changed from about 20%to about 50%. In some embodiments, when the multilayer stack is wound to form a flexible closed loop with the electrically conductive layer forming an outside layer of the loop, an electrical conductance per unit length (see, e.g., conductance per unit length σ schematically depicted in FIG. 2C where the length is the length in y-direction) of the closed loop across a diameter of the closed loop remains greater than about 1.9 mhos/cm when the loop is compressed across the diameter by at least 20%. In some embodiments, the electrical conductance per unit length of the closed loop across a diameter of the closed loop remains greater than about 2.2 mhos/cm when the loop is compressed across the diameter by at least 50%. The conductance can be increased by increasing the thickness of the electrically conductive layer (e.g., depositing a thicker metal layer) .

The thickness and/or modulus of the various layers (e.g., of the first and second polymeric layers) can be selected to provide a desired compression when a specified force or ranges of force is applied. In some embodiments, a compression force per unit length of the loop of no more than about 0.8kgf/cm applied across the diameter along the length of the loop compresses the loop across the diameter by at least about 80%. The compression force per unit length is the force F (see, e.g., FIG. 2B) divided by the length L (see, e.g., FIGS. 3A or 3B) . In some embodiments, the closed loop 200 regains at least about 80%of its initial diameter D0 after a force compressing the closed loop 200 across the initial diameter by at least about 70%, or at least about 80%, or at least about 85%, or at least about 90%is removed. In some embodiments, the closed loop 200 regains at least about 90%of its initial diameter D0 after a force compressing the closed loop 200 across the initial diameter by at least about 70%, or at least about 80%, or at least about 85%, or at least about 90%is removed. In some embodiments, the closed loop 200 regains at least about 70%of its initial diameter after a compression force F per unit length of the closed loop of about 0.8 kgf/cm applied across the initial diameter of the closed loop 200 is removed. In some embodiments, the closed loop 200 regains at least about 75%, or at least about 80%of its initial diameter D0 after the force per unit length of about 0.8 kgf/cm is removed.

In some embodiments, a hollow gasket 250 is formed by winding a multilayer stack (e.g.,

multilayer stack

100, 100’, 100”, 100”’ or other multilayer stacks described elsewhere herein) in a shape of a flexible hollow loop 200 and bonding first and

second portions

253 and 251 of opposing first and second sides of the multilayer stack (e.g., sides 102 and 104 of the multilayer stack) to each other to form the flexible hollow closed loop 200, where the electrically conductive layer 120 forms an outermost layer of the closed loop. The first and

second portions

253 and 251 may be bonded to each other via an adhesive 255 which may be an electrically conductive adhesive. In other embodiments, a hollow gasket (see, e.g., FIG. 6A) is formed by bending the multilayer stack in a shape of a flexible hollow loop and bonding first and second portions of a same side of the multilayer stack (e.g., side 104 of the multilayer stack) to each other to form the flexible hollow closed loop, where the electrically conductive layer 120 forms an outermost layer of the closed loop.

FIGS. 3A-3B are schematic top view of

hollow gaskets

350a and 350b, respectively, either of which may correspond to hollow gasket 250 or other hollow gaskets described elsewhere herein. The hollow gaskets have a length L and a diameter D (e.g., corresponding to an initial diameter D0) . The length L and diameter D may be selected as desired for a given application. For hollow gasket 350a, L/D < 1 and for hollow gasket 350b, L/D > 1. In some embodiments, L/D is greater than about 0.5, or greater than about 1, or greater than about 2. In some such embodiments, or in other embodiments, L/D is less than about 20, or less than about 10. In some embodiments, L/D is in a range of about 0.5 to about 2.

FIG. 4 is a schematic cross-sectional view of a hollow gasket 450 formed by winding a multilayer stack (e.g.,

multilayer stack

100, 100’, 100”, 100”’ or other multilayer stacks described elsewhere herein) in a shape of a flexible hollow loop 400 and bonding first and second portions 453 and 451 (e.g., corresponding to end portions of the first and/or second polymeric layers of the multilayer stack) of opposing first and second sides of the multilayer stack (e.g., sides 102 and 104 of the multilayer stack) to each other to form the flexible hollow closed loop 400. The first and

second portions

453 and 451 may be bonded to each other via an adhesive 455, which may be an electrically conductive adhesive. An electrically conductive adhesive 457 is included in the illustrated embodiment for bonding and electrically connecting the hollow gasket 450 to a first electrically conductive surface (e.g., a surface of an electrode in an electronic device) . The electrically conductive adhesive 457 may be an electrically conductive pressure sensitive adhesive, for example. A top portion of the loop 400 may contact a second electrically conductive surface so that the multilayer stack provides an electrical path between the two conductive surfaces (see, e.g., FIGS. 7-8) . The first and

second portions

453 and 451 are adjacent respective first and second

opposite edges

463 and 461 of the multilayer stack.

FIG. 5 is a schematic cross-sectional view of a hollow gasket 550 formed by winding a multilayer stack (e.g.,

multilayer stack

100, 100’, 100”, 100”’ or other multilayer stacks described elsewhere herein) in a shape of a flexible hollow loop 500 and bonding first and

second portions

553 and 551 of opposing first and second sides of the multilayer stack (e.g., sides 102 and 104 of the multilayer stack) to each other to form the flexible hollow closed loop 500. The first and

second portions

553 and 551 may be bonded to each other via an adhesive 555 which may be an electrically conductive adhesive. The first portion 553 is adjacent a first edge 563 of the multilayer stack and an opposite second edge 561 of the multilayer stack is spaced apart from the second portion 551 by a distance d greater than a width W of the second portion 551. An adhesive 557 is included adjacent second edge 561 for bonding the hollow gasket to a substrate. In some embodiments, the hollow loop is used to electrically connect electrically conductive first and second surfaces and the adhesive 557 bonds the hollow loop to an electrically insulative substrate adjacent at least one of the first and second surfaces. In some embodiments, the adhesive 557 is electrically insulative. In some embodiments, the

hollow gasket

450 or 550 regains at least 80%, or at least about 90%of its initial diameter D0 (see, e.g., FIG. 2A) after a force compressing the gasket across the initial diameter D0 by at least about 80%is removed. In some such embodiments, or in other embodiments, the

hollow gasket

450 or 650 regains at least about 70%of its initial diameter after a compression force per unit length of the gasket of about 0.8 kgf/cm compressing the gasket across the initial diameter is removed.

FIG. 6A is a schematic cross-sectional view of a hollow gasket 650 formed by bending a multilayer stack (e.g.,

multilayer stack

100, 100’, 100”, 100”’ or other multilayer stacks described elsewhere herein) in a shape of a flexible hollow loop 600 and bonding first and second portions 653 and 651 (e.g., corresponding to end portions of the first and/or second polymeric layers of the multilayer stack) of a same side 604 (e.g., corresponding to side 104 of

multilayer stack

100, 100’, 100”, or 100”’) of the multilayer stack to each other to form a flexible hollow closed loop 600. In the illustrated embodiment, the first and

second portions

653 and 651 are adjacent edges of the multilayer stack. In other embodiments, one of the first and

second portions

653 and 651 may be spaced apart from an edge of the multilayer stack to provide a segment having a length d (see, e.g., FIG. 5) . In some embodiments, an electrically conductive adhesive layer 657 for bonding the hollow gasket 650 to an electrically conductive surface is included. FIG. 6B is a schematic cross-sectional view of hollow gasket 650 after it has been compressed across its initial diameter D0 to a compressed diameter D1. In some such embodiments, the hollow gasket 650 regains at least 80%, or at least about 90%of its initial diameter D0 (see, e.g., FIG. 2A) after a force compressing the gasket across the initial diameter D0 by at least about 80%is removed. In some such embodiments, the hollow gasket 650 regains at least about 70%of its initial diameter after a compression force per unit length of the gasket of about 0.8 kgf/cm compressing the gasket across the initial diameter is removed.

FIG. 7 is a schematic cross-sectional view of an electronic device 1000 including electrically conductive first and

second surfaces

10 and 20 spaced apart along a first direction (z-direction) and facing each other. The electronic device 1000 further includes a first compressed cylinder 30 disposed between the first and

second surfaces

10 and 20. The first compressed cylinder 30 may include any hollow gasket described elsewhere herein and extends along a longitudinal second direction (y-direction) orthogonal to the first direction (z-direction) . The cylinder 30 includes an electrically conductive external layer 31 (e.g., corresponding to electrically conductive layer 120) disposed on an internal layer 32 (e.g., corresponding to layer 130) , which may be electrically insulative. The first compressed cylinder 30 may correspond to any hollow gasket described elsewhere herein and/or may be formed from any multilayer stack described elsewhere herein. For example, the cylinder 30 may be formed by winding a multilayer stack to form a cylinder and may include overlapping portions as described further elsewhere herein. The electrically conductive external layer 31 may include a metal layer, for example, and may further include an electrically conductive adhesive (e.g., corresponding to electrically conductive adhesive 457) proximate a portion of at least one of the first and

second surfaces

10 and 20 to electrically connect the metal layer to the surface. A polymeric layer 37 (e.g., corresponding to first polymeric layer 110) may be disposed between the external layer 31 and the internal layer 32. In some embodiments, the external layer 31 provides an electrically conductive path between the first and

second surfaces

10 and 20 by virtue of making electrical contact with the first and

second surfaces

10 and 20. In some embodiments, the external layer 31 (which may be the electrically conductive layer 120) makes physical contact with one of the first and second surfaces and makes electrical contact with the other of the first and second surfaces through a conductive adhesive (e.g., corresponding to electrically conductive adhesive 457) . The compressed cylinder may also include an adhesive (e.g., corresponding to adhesive 455) bonding end portions of the multilayer stack to one another. In some embodiments, the first compressed cylinder has an outer dimension D1 along the first direction and an outer dimension D3 along a third direction (x-direction) orthogonal to the first and second directions. In some embodiments, D3/D1 ≥ 1.2, or D3/D1 ≥ 1.5, or D3/D1 ≥ 2.

In some embodiments, the electronic device 1000 further includes a second compressed cylinder. This is schematically illustrated in FIG. 8 which is a schematic cross-sectional view of an electronic device 2000 that corresponds to electronic device 1000 except that a second compressed cylinder 33 is between the first and

second surfaces

10 and 20. The second compressed cylinder 33 may be as described for the first compressed cylinder 30. Additional compressed cylinders may also be included.

Examples

Multilayer stacks were made with metal (nickel) plated onto a polyethylene terephthalate (PET) layer with at least one additional layer (e.g., a pressures sensitive adhesive (PSA) layer and/or a second PET layer) disposed on a side of the PET layer opposite the metal layer. 2.54 cm x 2.54 cm samples of the multilayer stacks were wound into loops having a length (e.g., corresponding to the length L depicted in FIGS. 3A-3B) of 2.54 cm and having ends overlapping by about 2 mm. Recovery was measured after a 2 kgf (about 0.8 kgf/cm) force compressing the loop was removed and after a force compressing the loop by 80%was removed. The thicknesses of the various layers and the recovery results are reported in the following table. The layers behind the metal are listed in order starting with the layer facing the metal layer.

In Examples 1-2, the PSA layer was bonded only to the 20 μm PET layer and no other backing layer was present. In Example 3, the two PET layers were attached to one another only along end portions of the layers.

Testing of various 80 μm thick backing layers bonded to PET with a PSA showed that backings of nitrile, latex, and PVC gave at least 80%recovery after a 2kgf was removed and at least 86%recovery after 80%compression; that backings of TPEE and LDPE gave at least 75%recovery after a 2kgf was removed and at least 84%recovery after 80%compression; and that backings of HDPE and polypropylene (PP) when bonded to the PET layer with the PSA resulted in no more than 59%recovery after a 2kgf was removed and no more than 73%recovery after 80%compression. The HDPE and PP layers had significantly higher Young’s modulus than the TPEE and LDPE layers which had significantly higher Young’s modulus than the nitrile, latex, and PVC layers.

Computer simulations of loops formed from multilayer stacks including a 20 micrometer thick PET layer (first polymeric layer) bonded to various 20 micrometer thick polymeric backing layers (second polymeric layer) with a 10 micron thick pressure sensitive adhesive, showed that a low modulus TPEE backing layer gave significantly improved recovery compared to higher modulus (e.g., PET) backing layers. Computer simulations also showed that when the pressure sensitive adhesive was omitted so that the backing layer was not bonded to the PET layer except along opposing ends of the layers, that a variety of backing layers (e.g., PET, polyurethane, TPEE) gave suitable recovery results.

Terms such as “about” will be understood in the context in which they are used and described in the present description by one of ordinary skill in the art. If the use of “about” as applied to quantities expressing feature sizes, amounts, and physical properties is not otherwise clear to one of ordinary skill in the art in the context in which it is used and described in the present description, “about” will be understood to mean within 5 percent of the specified value. A quantity given as about a specified value can be precisely the specified value. For example, if it is not otherwise clear to one of ordinary skill in the art in the context in which it is used and described in the present description, a quantity having a value of about 1, means that the quantity has a value between 0.95 and 1.05, and that the value could be 1.

All references, patents, and patent applications referenced in the foregoing are hereby incorporated herein by reference in their entirety in a consistent manner. In the event of inconsistencies or contradictions between portions of the incorporated references and this application, the information in the preceding description shall control.

Descriptions for elements in figures should be understood to apply equally to corresponding elements in other figures, unless indicated otherwise. Although specific embodiments have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that a variety of alternate and/or equivalent implementations can be substituted for the specific embodiments shown and described without departing from the scope of the present disclosure. This application is intended to cover any adaptations, or variations, or combinations of the specific embodiments discussed herein. Therefore, it is intended that this disclosure be limited only by the claims and the equivalents thereof.

Claims

An electrically conductive multilayer stack for providing an electrical path between two conductive surfaces, comprising:

a first polymeric layer;

an electrically conductive layer bonded to a first side of the first polymeric layer; and

a second polymeric layer disposed on an opposite second side of the first polymeric layer, the first and second polymeric layers and the electrically conductive layer being substantially coextensive with one another, such that when the multilayer stack is wound to form a flexible closed loop with the electrically conductive layer forming an outside layer of the closed loop:

the closed loop regains at least about 80%of its initial diameter after a force compressing the closed loop across the initial diameter by at least about 80%is removed; and

the closed loop regains at least about 70%of its initial diameter after a compression force per unit length of the closed loop of about 0.8 kgf/cm compressing the closed loop across the initial diameter is removed.
The electrically conductive multilayer stack of claim 1, wherein the first and second polymeric layers are attached to one another only along opposing end portions of the first and second polymeric layers such that when the multilayer stack is wound to form the flexible closed loop, the end portions of the first polymeric layer overlap one another.
The electrically conductive multilayer stack of claim 1, wherein a Young’s modulus of the first polymeric layer is at least 30%greater than a Young’s modulus of the second polymeric layer.
The electrically conductive multilayer stack of claim 1, wherein the first polymeric layer comprises polyethylene terephthalate (PET) or polyimide, and wherein the second polymeric layer comprises polyvinylchloride (PVC) , latex, nitrile, polypropylene, polyethylene, or thermoplastic polyester elastomer (TPEE) .
The electrically conductive multilayer stack of claim 1, wherein the first and second polymeric layers are bonded to one another with a pressure sensitive adhesive layer substantially coextensive with the first and second polymeric layers, the second polymeric layer having a Young’s modulus less than about 0.3 times a Young’s modulus of the first polymeric layer.
The electrically conductive multilayer stack of claim 1, wherein the second polymeric layer is an adhesive layer.
An electrically conductive multilayer stack for providing an electrical path between two conductive surfaces, comprising:

a first polymeric layer extending along a first direction between opposing end portions of the first polymeric layer, the first direction being orthogonal to a thickness direction of the multilayer stack;

an electrically conductive layer bonded to a first side of the first polymeric layer;

a second polymeric layer disposed on an opposite second side of the first polymeric layer, the first and second polymeric layers and the electrically conductive layer being substantially coextensive with one another, the second polymeric layer extending along the first direction between opposing end portions of the second polymeric layer, the first and second polymeric layers attached to one another only along the end portions of the first and second polymeric layers, such that when the multilayer stack is wound to form a flexible closed loop with the electrically conductive layer forming an outside layer of the closed loop and with the end portions of the first polymeric layer overlapping one another, the closed loop regains at least about 80%of its initial diameter after a force compressing the closed loop across the initial diameter by at least about 80%is removed.
The electrically conductive multilayer stack of claim 7, wherein when the multilayer stack is wound to form the flexible closed loop with the electrically conductive layer forming an outside layer of the closed loop, the closed loop regains at least about 90%of its initial diameter after a force compressing the closed loop across the initial diameter by at least about 80%is removed.
An electrically conductive multilayer stack for providing an electrical path between two conductive surfaces, comprising:

a first polymeric layer;

an electrically conductive layer bonded to a first side of the first polymeric layer;

a pressure sensitive adhesive layer disposed on an opposite second side of the first polymeric layer and being substantially coextensive with the first polymeric layer and the electrically conductive layer; and

powder disposed on a first major surface of the pressure sensitive adhesive layer facing away from the first polymeric layer to reduce tack of the pressure sensitive adhesive layer, such that when the multilayer stack is wound to form a flexible closed loop with the electrically conductive layer forming an outside layer of the closed loop, the closed loop regains at least about 80%of its initial diameter after a force compressing the closed loop across the initial diameter by at least about 80%is removed.
The electrically conductive multilayer stack of claim 9, wherein the power is disposed to reduce tack of at least about 60%of a total area of the first major surface of the pressure sensitive adhesive layer.
The electrically conductive multilayer stack of claim 9, wherein an average thickness of the pressure sensitive adhesive layer is greater than an average thickness of the first polymeric layer.
The electrically conductive multilayer stack of claim 9, wherein when the multilayer stack is wound to form the flexible closed loop with the electrically conductive layer forming an outside layer of the closed loop, the closed loop regains at least about 70%of its initial diameter after a compression force per unit length of the closed loop of about 0.8 kgf/cm compressing the closed loop across the initial diameter is removed.
The electrically conductive multilayer stack of any one of claims 1 to 12, wherein the electrically conductive layer comprises one or more of copper, nickel, silver, aluminum, gold, indium tin oxide (ITO) , and tin.
The electrically conductive multilayer stack of any one of claims 1 to 12, wherein the electrically conductive layer is electrodeposited onto the first polymeric layer.
A hollow gasket formed by winding the electrically conductive multilayer stack of any one of claims 1 to 12 in a shape of a flexible hollow loop and bonding first and second portions of opposing first and second sides of the multilayer stack to each other to form a flexible hollow closed loop, the electrically conductive layer forming an outermost layer of the closed loop.