A tape

Abstract

The present invention discloses an adhesive tape, which includes a first layer of conductive adhesive having an outermost first major surface and a second major surface facing each other. The first layer includes a conductive porous medium and an adhesive, the adhesive being disposed in the porous medium and extending through the thickness of the porous medium to define a first area of ​​exposed adhesive and a first area of ​​exposed porous medium at the first major surface, and a second area of ​​exposed adhesive and a second area of ​​exposed porous medium at the second major surface. The second major surface has a higher fraction of exposed porous medium than the first major surface. The porous medium may be a nonwoven fabric, and the area of ​​exposed porous medium may be an area of ​​exposed fibers.

Description

Technical Field

[0001] The invention relates to an adhesive tape, in particular to an adhesive tape comprising a conductive porous medium. Background Art

[0002] The conductive tape may include a plurality of conductive particles in its adhesive layer. The conductive particles may contact each other, thereby forming a conductive path. Summary of the invention

[0003] In some aspects of the specification, a tape is provided, the tape comprising a first layer of conductive adhesive having an outermost first major surface and a second major surface facing each other. The first layer comprises a conductive nonwoven layer and an adhesive, the conductive nonwoven layer comprising metal-coated polymer fibers, the adhesive being disposed in the nonwoven layer and extending through the thickness of the nonwoven layer to define a first area of ​​exposed adhesive and a first area of ​​exposed fibers of the nonwoven layer at the first major surface, and a second area of ​​exposed adhesive and a second area of ​​exposed fibers of the nonwoven layer at the second major surface. In a plan view, the first major surface comprises a first area of ​​exposed fibers accounting for an area percentage of P1, and the second major surface comprises a second area of ​​exposed fibers accounting for an area percentage of P2, wherein 15%<P1<70%, 30%<P2<95%, and P2-P1>5%.

[0004] In some aspects of the specification, there is provided an adhesive tape comprising a first layer of an electrically conductive adhesive having an outermost first major surface and a second major surface facing each other. The first layer comprises an electrically conductive porous medium and an adhesive disposed in the porous medium and extending through the thickness of the porous medium to define a first region of exposed adhesive and a first region of exposed porous medium at the first major surface, and a second region of exposed adhesive and a second region of exposed porous medium at the second major surface. In a plan view, the first major surface comprises a first region of exposed porous medium accounting for an area percentage of P1, and the second major surface comprises a second region of exposed porous medium accounting for an area percentage of P2, wherein 15% < P1 < 70%, 30% < P2 < 95%, and P2-P1 > 5%.

[0005] These and other aspects will become apparent from the following detailed description.This brief summary, however, should not be construed in any way as limiting the claimed subject matter. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Figure 1 is a schematic cross-sectional view of an adhesive tape according to some embodiments.

[0007] Figure 2 is a schematic cross-sectional view of an adhesive tape including layers on opposite sides of an adhesive layer according to some embodiments.

[0008] Figure 3 is a plan view image of a portion of a major surface of a conductive layer of an exemplary tape.

[0009] Figure 4 is a plan view of a major surface of a conductive layer according to some embodiments, the major surface being divided into regions having a width W1 and a length L1.

[0010] Figure 5 Schematically illustrates the Figure 4 The distribution of the area percentage of exposed porous medium or exposed fibers in terms of area.

[0011] Figure 6 is a schematic cross-sectional view illustrating coating a porous medium, such as a nonwoven fabric, with a binder, according to some embodiments.

[0012] Figure 7 is a schematic cross-sectional view of an adhesive tape disposed between and bonding two substrates together, according to some embodiments.

[0013] Figure 8 is a schematic cross-sectional view illustrating 180 degree peeling of a tape from a substrate, according to some embodiments. DETAILED DESCRIPTION

[0014] In the following description, reference is made to the accompanying drawings, which form a part of the present invention and in which various embodiments are shown by way of example. The drawings are not necessarily drawn to scale. It should be understood that other embodiments may be conceived and carried out without departing from the scope or essence of the present description. Therefore, the following specific embodiments should not be considered to have a limiting meaning.

[0015] Conductive tape can utilize conductive nonwoven fabric and the adhesive material containing conductive filler particles to bond adjacent substrates together and provide electrical conduction between substrates, wherein the exposed portion of nonwoven fabric provides electrical contact with substrate. However, such adhesive tapes usually have an exposed area of ​​relatively low nonwoven fabric at the main surface of adhesive layer or have relatively high variation in the exposed area. This can lead to poor and / or variable performance in the final application. According to some embodiments of this specification, the porous medium can be coated from one side of a conductive porous medium (such as conductive nonwoven fabric) by using adhesive so that the adhesive is forced to pass through the porous medium, thereby forming an adhesive tape. According to some embodiments, it has been found that this can make the adhesive tape have an area fraction of the exposed conductive medium higher than conventional conductive tape. In addition, according to some embodiments, it has been found that the exposed area can have a sufficiently uniform distribution so that there will be no exposure to be too low for electrical contact or to be exposed to be too high for sufficient bonding. In some applications, adhesive tape is used between different substrates so that a side of the adhesive layer is expected to have a porous medium exposure higher than the opposite side. According to some embodiments, the coating process described herein can naturally achieve this result. In addition, according to some embodiments, it has been found that the conductive tape has improved electrical properties compared to conventional tapes. For example, according to some embodiments, without the addition of conductive particles, the conductive tape can have low passive intermodulation (PIM) and / or low resistance.

[0016] Conductive tape can be prepared by laminating an adhesive layer on one or both sides of a conductive porous (e.g., nonwoven) carrier. A problem with this type of tape is a short shelf life. Since the porous carrier is laminated with an adhesive layer after drying, the holes of the carrier are not immediately filled with adhesive. However, the adhesive can be slowly (e.g., within a few months) pushed into the holes of the carrier and this can cause problems with poor tape surface smoothness and adhesion. According to some embodiments, the porous medium can be coated with an adhesive from one side of the porous medium so that the adhesive is forced to pass through the porous medium, thereby forming the tape described herein. This can make the holes substantially filled with adhesive, thereby enhancing the stability and performance of the tape. According to some embodiments, it has also been found that the process described herein allows the preparation of tapes thinner than those tapes prepared in conventional processes.

[0017] Conductive tapes typically include conductive filler particles in the adhesive to achieve the desired conductivity. According to some embodiments of the present specification, even when the adhesive is substantially free of conductive filler particles, the desired conductivity can be achieved, at least in part due to appropriate exposure of the conductive porous medium at the major surface of the conductive adhesive layer.

[0018] Figure 11 is a schematic cross-sectional view of a tape 100 according to some embodiments, the tape comprising a first layer 110 of conductive adhesive having an outermost first major surface 112 and a second major surface 114 that are opposed to each other. The first layer 110 comprises a conductive porous medium 120 and an adhesive 130 disposed in and extending through the thickness of the porous medium 120 to define a first region 132 of exposed adhesive and a first region 126 of exposed porous medium at the first major surface 112, and a second region 134 of exposed adhesive and a second region 128 of exposed porous medium at the second major surface 114. In some embodiments, in a plan view (see, e.g., Figure 3 to Figure 4 ), first major surface 112 includes first areas 126 of exposed porous medium that account for an area percentage of P1, and second major surface 114 includes second areas 128 of exposed porous medium that account for an area percentage of P2, wherein 15%<P1<70%, and 30%<P2<95%. In some embodiments, first major surface 112 includes a substantially uniform distribution of first areas 126 of exposed porous medium 120. In some embodiments, second major surface 114 includes a substantially uniform distribution of second areas 128 of exposed porous medium 120.

[0019] The exposed portion (e.g., exposed portion 132, 126, 134, or 128) of a major surface (e.g., major surface 112 or 114) of a layer (e.g., first layer 110) refers to a portion exposed to any adjacent layer present at the major surface. For example, the adjacent layer may be an air layer, in which case the exposed portion may be described as being exposed to the air. For example, the adjacent layer may be a peeling layer or a bonded substrate, in which case the exposed portion may be described as being exposed to the peeling layer or the bonded substrate.

[0020] In some embodiments, the porous medium 120 is or includes a nonwoven fabric including polymer fibers 122 coated with a metal 123. In other embodiments, the porous medium is or includes a different type of fabric (e.g., a woven fabric) coated with a metal or other electrical conductor or a different type of porous medium, such as a different type of open-cell polymer porous medium coated with a metal or other electrical conductor. Figure 1 In the embodiment schematically shown in , the porous medium 120 is a nonwoven fabric including metal-coated polymer fibers 122. The metal coating 123 may be or include, for example, copper, nickel, silver, gold, tin, cobalt, chromium, aluminum, or a combination thereof. The metal coating 123 may be applied by, for example, plating or sputtering. The polymer fibers 122 may be or include, for example, polyester, nylon, polyurethane, vinylon, polyvinyl acetate, acrylate, cellulose polymer, or a combination thereof. The fibers may be metallized after the nonwoven fabric has been formed or the nonwoven fabric may be made of metallized fibers.

[0021] In embodiments where the porous medium 120 is a nonwoven fabric, the tape 100 may be described as comprising a first layer 110 of conductive adhesive having an opposed outermost first major surface 112 and a second major surface 114, wherein the first layer 110 comprises a conductive nonwoven layer 120 and an adhesive 130, the conductive nonwoven layer comprising metal-coated polymer fibers 122, the adhesive being disposed in the nonwoven layer 120 and extending through the thickness of the nonwoven layer to define a first area 132 of exposed adhesive and a first area 126 of exposed fibers of the nonwoven layer at the first major surface 112, and a second area 134 of exposed adhesive and a second area 128 of exposed fibers of the nonwoven layer 120 at the second major surface 114. In some embodiments, in a plan view, the first major surface 112 comprises the first area 126 of exposed fibers as an area percentage of P1, and the second major surface 112 comprises the second area 128 of exposed fibers as an area percentage of P2, wherein 15%<P1<70%, and 30%<P2<95%. In some embodiments, the first major surface 112 has a substantially uniform distribution of first areas 126 of exposed fibers. In some embodiments, the second major surface 114 has a substantially uniform distribution of second areas 128 of exposed fibers.

[0022] In some embodiments, the first major surface and / or the second major surface consists essentially of exposed porous media (e.g., exposed fibers) and exposed binder. In other words, in some embodiments, in a plan view, the first (and / or second) major surface includes exposed binder accounting for about 100-P1 (or 100-P2) area percentage at the major surface.

[0023] In some embodiments, such as Figure 1 Schematically shown in, for example, P2>P1. In some embodiments, P2-P1>5%, or P2-P1>10%, or P2-P1>15%, or P2-P1>20%. In some such embodiments, or in other embodiments, 15%<P1<60%, 20%<P1<60%, or 20%<P1<50%, or 20%<P1<40%. In some such embodiments, or in other embodiments, 30%<P2<90%, or 35%<P2<85%, or 40%<P2<80%, or 40%<P2<75%, or 40%<P2<70%.

[0024] Adhesive 130 may be a pressure sensitive adhesive (PSA). In order to achieve the desired properties, the polymer used for the adhesive may be regulated so that the resulting glass transition temperature (Tg) is less than about 0°C. Examples of suitable PSA materials include, for example, rubber-based PSA, silicone-based PSA, and acrylic-based PSA. Particularly suitable pressure sensitive adhesives are (meth) acrylate copolymers. Such copolymers are typically derived from monomers containing about 40% to about 98% by weight, often at least about 70% by weight, or at least about 85% by weight, or even at least about 90% by weight of at least one (meth) acrylate alkyl ester monomer, which has a Tg of less than about 0°C as a homopolymer. Examples of such (meth) acrylate alkyl ester monomers include those in which the alkyl group contains about 4 to about 14 carbon atoms, and include, for example, n-butyl acrylate, 2-ethylhexyl acrylate, isooctyl acrylate, isononyl acrylate, isodecyl acrylate, and mixtures thereof. Optionally, other vinyl monomers and (meth) alkyl acrylate monomers (which have a Tg greater than 0°C as a homopolymer, such as, for example, methyl acrylate, methyl methacrylate, isobornyl acrylate, vinyl acetate, and / or styrene) can be used in combination with one or more low Tg alkyl (meth) acrylate monomers and copolymerizable polar monomers. The term (meth) acrylate is used to refer to both acrylate and methacrylate materials. Other useful adhesives are described, for example, in U.S. Patent Application Publication No. 2016 / 0333232 (Choi et al.) and U.S. Patent No. 9,061,478 (Choi et al.).

[0025] It has been found that softer adhesives can produce better surface uniformity and have better aging characteristics than harder adhesives. In some embodiments, adhesive 130 has a Young's modulus E' of less than about 1 MPa at 25°C and / or a loss modulus E" of less than about 0.4 MPa at 25°C and / or a loss tangent (tan δ) of less than about 0.7 at 25°C. The elastic properties of the adhesive can be adjusted by appropriate selection of monomers in the adhesive formulation (for example, aliphatic monomers can produce softer adhesives than aromatic monomers and / or monomers that can produce linear molecules can produce softer adhesives than monomers that can produce branched molecules), as will be understood by those of ordinary skill in the art.

[0026] In some embodiments, tape 100 further includes at least one release liner. Figure 2is a schematic cross-sectional view of tape 200 according to some embodiments, which tape may correspond to tape 100 but includes first layer 141 and second layer 142 disposed on respective first major surface 112 and second major surface 114. In some embodiments, each of first layer 141 and second layer 142 is a release liner, and tape 200 may be described as a double-sided tape. In some embodiments, one of first layer 141 and second layer 142 is a release liner, and the other of first layer 141 and second layer 142 is a backing layer, such as a metal foil, and tape 200 may be described as a single-sided tape.

[0027] Figure 1 The adhesive tape 100 and the first layer 110 have an average thickness h1. Figure 2 The adhesive tape 200 has an average thickness h2. In some embodiments, the adhesive tape 100 or 200 has an average thickness (h1 or h2) in the range of about 10 microns to about 200 microns, or 10 microns to about 100 microns, or about 15 microns to about 60 microns, or about 20 microns to about 50 microns. In some embodiments, the first layer 110 has an average thickness h1 in the range of about 10 microns to about 200 microns, or about 10 microns to about 100 microns, or about 15 microns to about 60 microns, or about 20 microns to about 50 microns, or about 20 microns to about 40 microns, or about 20 microns to about 35 microns.

[0028] The fractions of exposed binder and exposed porous medium at the major surface can be determined using optical microscopy. Figure 3 1 is an image of a portion of a major surface of an exemplary first layer (e.g., corresponding to first layer 110) in which areas of exposed adhesive appear darker than areas of exposed porous medium. Line 160 has been drawn around the areas of exposed adhesive. Standard digital image processing techniques can be used to determine the area within line 160. The area percentage of exposed porous medium at the major surface is then 100 area percentage minus the area percentage within line 160.

[0029] Machine learning models such as object detection, defect classification, segmentation detection, and custom image feature extraction computer vision algorithms and methods can be applied to determine the area fraction of exposed porous media. Both rule-based models and deep learning-based models can be effectively and efficiently applied to irregular shapes such as protruding fibers. One type of suitable instance image segmentation model is called a Mask-RCNN model in the art. Such models can detect objects (e.g., exposed fibers or other porous media) and accurately segment them from the background. Once the model has been trained with a set of suitable similarly labeled images, these objects can be segmented and covered with masks of the same size. The advantage of using Mask-RCNN over conventional computer vision techniques is that Mask-RCNN is insensitive to background noise. For example, small dots with sizes that are significantly different from the target object will not be detected in Mask-RCNN and will not be segmented from the background. Rule-based algorithms and non-neural network methods are also suitable methods for determining exposure areas. Another suitable method is to use a hybrid model including a deep neural network and a non-neural network computer vision machine learning model.

[0030] Figures 4 to 5 Determining the mean and standard deviation of the percentage of exposed porous medium (eg, exposed fibers) area is schematically illustrated according to some embodiments. Figure 4 is a plan view of a major surface of the first layer 110, the major surface being divided into a plurality of rectangular regions 178 having a width W1 and a length L1. A plan view of a major surface of a layer is a view along a direction substantially perpendicular to the layer. Figure 4 The main surface in the first major surface 112 or the second major surface 114 may correspond to the first major surface 112 or the second major surface 114. For example, the width W1 and the length L1 may each be in the range of about 0.7mm to about 5mm, or about 1mm to about 5mm, or about 2mm to about 5mm, or about 3mm to about 5mm, or about 0.7mm to about 3mm, or about 0.7mm to about 2mm. Rectangular area 178 may each have the same width and length, or different lengths and widths may be used for different rectangular areas 178, wherein each length and each width are in the range of about 0.7mm to about 5mm or in another range described elsewhere herein. A square is a special case of a rectangle, and in some embodiments, W1 and L1 are equal. In some embodiments, for each area 178, W1 and L1 are each about 1mm or about 3mm or about 5mm. Each area 178 may be marked with an available area number so that the i-th area includes an area 126 or 128 accounting for a Pi area percentage. Figure 5 Schematically shown is the distribution of Pi values ​​for region 178. The average value (mean) Pavg and the standard deviation σ are indicated. Figures 4 to 5The analysis can be applied to the first major surface 112 and the second major surface 114 separately. The values ​​P1 and P2 of the first major surface 112 and the second major surface 114 can be approximated as Pavg determined for these surfaces. The total number of zones 178 is selected to be high enough so that the mean and standard deviation of the percentage of exposed porous media (e.g., exposed fibers) area determined using zones 178 represent the mean and standard deviation of the main surface. For example, the total number of zones 178 can be selected to be high enough so that the mean and standard deviation of the percentage of exposed porous media (e.g., exposed fibers) area will not change significantly when more zones are included. In some embodiments, for example, the total number of zones 178 is at least 10 or at least 15 or at least 20, and can be at most 100 or at most 50.

[0031] The distribution of first region 126 (respectively, second region 128) can be described as being substantially uniform when the standard deviation σ of the percent exposed porous medium area or percent exposed fiber area measured within rectangular regions 178 of first major surface 112 (respectively, second major surface 114) is less than 0.35P1 (respectively, 0.35P2), wherein each rectangular region 178 has a length L1 and a width W1, respectively, in the range of about 0.7 mm to about 5 mm. A rectangular region should be understood to be rectangular in plan view.

[0032] In some embodiments, the first major surface 112 has a substantially uniform distribution of first areas 126 of exposed porous medium. In some embodiments, the first major surface has a distribution of first areas of exposed porous medium 120, the distribution having a standard deviation σ of the percentage of exposed porous medium area 112 less than about 15%, less than about 10%, less than about 7%, or less than about 5%, when measured within a rectangular area of ​​the first major surface, such that each rectangular area has a length L1 and a width W1, respectively, in the range of about 0.7 mm to about 5 mm, or in the ranges described elsewhere herein. For example, the standard deviation σ of the first major surface can be as low as about 3%, about 2%, or about 1%. In some embodiments, the second major surface 114 has a distribution of second areas 128 exposing porous media 120, the distribution having a standard deviation σ of the percentage of exposed porous media area of ​​the second major surface 114 less than about 30% or less than about 25% or less than about 20% or less than about 18% measured within a rectangular area of ​​the second major surface, such that each rectangular area has a length L1 and a width W1 each in the range of about 0.7 mm to about 5 mm or within the ranges described elsewhere herein. For example, the standard deviation σ of the first major surface can be as low as about 6% or about 4% or about 3%. In some embodiments, the first major surface 112 has a distribution of first areas exposing porous media 120, the distribution having a standard deviation σ of the percentage of exposed porous media area less than about 0.35P1 or less than about 0.3P1 or less than about 0.28P1 or less than about 0.26P1 or less than about 0.25P1 or less than about 0.24P1 or less than about 0.23P1 when measured within a rectangular area of ​​the first major surface 112, as further described elsewhere herein. In some embodiments, second major surface 114 has a distribution of second areas 128 of exposed porous medium 120, the distribution having a standard deviation σ of the percentage of exposed porous medium area of ​​less than about 0.4P2, or less than about 0.38P2, or less than about 0.36P2, or less than about 0.35P2, or less than about 0.34P2, or less than about 0.33P2, when measured within a rectangular area of ​​first major surface 112, as further described elsewhere herein.

[0033] In some embodiments, for a total of at least 20 regular arrays of rectangular regions of the first major surface 112, each rectangular region includes, in a plan view, a first area 126 of exposed porous medium 120 that is greater than about 15 area percent, or greater than about 18 area percent, or greater than about 20 area percent, or greater than about 22 area percent, wherein each rectangular region has a length L1 and a width W1, each in the range of about 0.7 mm to about 5 mm, or in the ranges described elsewhere herein. In some such embodiments, for a total of at least 20 regular arrays of rectangular regions of the first major surface 112, each rectangular region includes, in a plan view, a first area 126 of exposed porous medium 120 that is less than about 70 area percent, or less than about 65 area percent, or less than 60 area percent. In some embodiments, for a total of at least 20 regular arrays of rectangular regions of the second major surface 114, each rectangular region includes, in a plan view, a second area 128 of the exposed porous medium 120 that is greater than about 30 area percent, or greater than about 35 area percent, or greater than about 40 area percent, wherein each rectangular region has a length L1 and a width W1, each in the range of about 0.7 mm to about 5 mm, or in a range described elsewhere herein. In some such embodiments, for a total of at least 20 regular arrays of rectangular regions of the second major surface 114, each rectangular region includes, in a plan view, a second area 128 of the exposed porous medium 120 that is less than about 95 area percent, or less than about 90 area percent, or less than about 85 area percent, or less than about 80 area percent. The regular array of rectangular regions may be a two-dimensional periodic array in which there are no gaps between adjacent rectangular regions.

[0034] In some embodiments, the porous medium is a nonwoven fabric. In some embodiments, the first major surface 112 has a substantially uniform distribution of first areas 126 of exposed fibers 122. In some embodiments, the first major surface has a distribution of first areas 126 of exposed fibers 122, when measured within a rectangular area of ​​the first major surface, the distribution has a standard deviation σ of the exposed fiber area of ​​less than about 15% or less than about 10% or less than about 7% or less than about 5%, so that each rectangular area has a length L1 and a width W1, each in the range of about 0.7 mm to about 5 mm or in the range described elsewhere herein. In some embodiments, the second major surface 114 includes a distribution of second areas 128 of exposed fibers 122, when measured within a rectangular area of ​​the second major surface, the distribution has a standard deviation of the exposed fiber area of ​​less than about 30% or less than about 25% or less than about 20% or less than about 18%, so that each rectangular area has a length L1 and a width W1, each in the range of about 0.7 mm to about 5 mm or in the range described elsewhere herein. In some embodiments, the first major surface 112 has a distribution of first areas 126 of exposed fibers 122, when measured within a rectangular area, the distribution having a standard deviation σ of the exposed fiber area of ​​less than about 0.35P1, or less than about 0.30P1, less than about 0.28P1, or less than about 0.26P1, or less than about 0.25P1, or less than about 0.24P1, or less than about 0.23P1, as further described elsewhere herein. In some embodiments, the second major surface 114 includes a distribution of second areas 128 of exposed fibers 122, when measured within a rectangular area, the distribution having a standard deviation of the exposed fiber area of ​​less than about 0.4P2, or less than about 0.38P2, or less than about 0.36P2, or less than about 0.35P2, or less than about 0.34P2, or less than about 0.33P2, as further described elsewhere herein.

[0035] In some embodiments, for a total of at least 20 regular arrays of rectangular regions of the first major surface 112, each rectangular region includes, in a plan view, a first region 126 of exposed fibers 122 that is greater than about 15 area percent, or greater than about 20 area percent, or greater than about 25 area percent, or greater than about 30 area percent, wherein each rectangular region has a length L1 and a width W1, each in the range of about 0.7 mm to about 5 mm, or in the ranges described elsewhere herein. In some such embodiments, for a total of at least 20 regular arrays of rectangular regions of the first major surface 112, each rectangular region includes, in a plan view, a first region 126 of exposed fibers 122 that is less than about 70 area percent, or less than about 65 area percent, or less than about 60 area percent. In some embodiments, for a total of at least 20 regular arrays of rectangular regions of the second major surface 114, each rectangular region includes, in a plan view, a second region 128 of exposed fibers 122 that is greater than about 30 area percent, or greater than about 35 area percent, or greater than about 40 area percent, wherein each rectangular region has a length L1 and a width W1, each in the range of about 0.7 mm to about 5 mm, or in the ranges described elsewhere herein. In some such embodiments, for a total of at least 20 regular arrays of rectangular regions of the second major surface 114, each rectangular region includes, in a plan view, a second region 128 of exposed fibers 122 that is less than about 95 area percent, or less than about 90 area percent, or less than about 85 area percent, or less than about 80 area percent. The regular array of rectangular regions may be a two-dimensional periodic array in which there are no gaps between adjacent rectangular regions.

[0036] The tape described herein can be formed by coating the porous medium with an adhesive from one side of the porous medium so that the adhesive penetrates the porous medium. Any suitable coating method can be used. One suitable method is to use a Meyer rod. A Meyer rod includes a wire wound around a drum and is characterized by a Meyer rod specification number that gives the wire diameter in mils. Figure 62 is a schematic cross-sectional view of a porous medium 120 (such as a nonwoven fabric) coated with an adhesive 130 using a Meyer rod 222 at a contact angle α according to some embodiments. It has been found that using a Meyer rod with a lower Meyer rod specification number (e.g., 15 to 26) can provide better coating uniformity, thereby generating a higher peel force, compared to using a Meyer rod with a higher Meyer rod specification number (e.g., 30 to 33). It has also been found that increasing the contact angle α can improve the penetration of the adhesive through the porous medium so that when the porous medium is coated from the first major surface 112, there is a sufficient amount of adhesive at the second major surface 114. It has also been found that when the porous medium is a nonwoven fabric, the tension in the fabric near the Meyer rod can be adjusted to further control how the adhesive is deposited. For example, a higher tension keeps the fabric and the Meyer rod in closer contact, thereby causing higher fiber exposure. The coated side generally has a lower percentage of exposed porous medium area than the opposite side. A backing layer, such as a release liner, may be applied to the side of the porous medium 120 opposite the Meyer rod. The adhesive may be applied in a solvent, which is then evaporated in an oven. The solids percentage of the adhesive in solvent may be in the range of 30 to 45 weight percent, and may be adjusted to obtain the appropriate rheology for coating.

[0037] It has been discovered that tapes made by coating a porous medium from one side thereof with an adhesive such that the adhesive penetrates the porous medium can produce improved electrical properties (e.g., low resistance and / or low passive intermodulation) and / or improved adhesion compared to conventional tapes.

[0038] Figure 7 is a schematic cross-sectional view of a tape 100' disposed between substrates 252 and 251 and bonding the two substrates together according to some embodiments. The tape 100' and the first layer 110' may correspond to the tape 100 and the first layer 110, respectively, except that the first layer 110' includes optional conductive filler particles 333. The conductive filler particles 333 may be included to reduce electrical resistance, or may be included in a sufficiently low volume loading of the conductive filler particles so that the effect on the electrical properties of the tape 100' is negligible. If included, the conductive filler particles 333 may be in the form of, for example, metal particles or metal-coated insulating (e.g., polymer) particles, or a combination thereof. If the conductive filler particles 333 are removed and replaced with an equal volume of adhesive 130 so that the conductive filler particles 333 are not removed in the thickness direction ( Figure 7In some embodiments, the first layer 110, 110' may be described as being substantially free of conductive filler particles 333 if the resistance Rz of the first layer 110, 110' in the thickness direction (z direction, refer to the xyz coordinate system shown) changes by less than about 10%. In some embodiments, the conductive filler particles 333 are removed and replaced with an equal volume of the adhesive 130 so that the resistance Rz of the first layer 110, 110' in the thickness direction (z direction) of the first layer 110, 110' changes by less than about 5%, less than about 3%, or less than about 2%. In some embodiments, less than about 5 volume percent, less than about 3 volume percent, or less than about 2 volume percent of the conductive filler particles 333 are included. In some embodiments, the first layer 110, 110' has a resistance Rz of less than about 300 mΩ, less than about 200 mΩ, less than about 100 mΩ, less than about 50 mΩ, less than about 35 mΩ, less than about 30 mΩ, less than about 29 mΩ, or less than about 28 mΩ in the thickness direction (z direction) of the first layer. In some such embodiments, or in other embodiments, the first layer 110, 110' contains no or substantially no conductive filler particles 333. For example, the resistance Rz can be as low as about 24 mΩ, or as low as about 20 mΩ, or as low as about 16 mΩ. For example, as the exposed fraction of the porous conductive medium increases, the resistance generally decreases.

[0039] In some embodiments, the tape has low passive intermodulation (PIM). When two or more signals at different frequencies mix with each other, PIM is generated due to electrical nonlinearity. In some cases, the PIM signal may have a frequency close to the input frequency and this may cause undesirable interference. Substrates 251 and 252 have respective major surfaces 261 and 262 facing the first layer 110'. Substrate 252 may be gold and / or include a gold major surface 262 (e.g., by plating with gold). Substrate 251 may be stainless steel and / or include a stainless steel major surface 261. The first layer 110' may be arranged so that the second major surface 114 faces the gold surface 262 and the first major surface 112 faces the stainless steel surface 261. In some embodiments, when the first electrical signal 401 and the second electrical signal 402 propagate between the gold surface 262 and the stainless steel surface 261 along the thickness direction (z direction) of the first layer 110, 110' at respective frequencies F1 and F2, any intermodulation signal 403 generated by the first electrical signal and the second electrical signal and having a frequency F3 equal to nF1+mF2 (where m and n are positive or negative integers) has a power of less than about -88 dB, or less than about -90 dB, or less than about -94 dB, or less than about -95 dB, or less than about -97 dB, or less than about -98 dB, or less than about -99 dB, or less than about -100 dB, or less than about -101 dB relative to the total power of the first signal 401 and the second signal 402. The power may be as low as about -110 dB, or as low as about -105 dB relative to the total power of the first signal 401 and the second signal 402. F1 and F2 are each selected from the frequency range of fa to fb. For example, frequency fa can be about 100MHz or about 200MHz or about 300MHz or about 500MHz or about 700MHz or about 800MHz or about 850MHz, and frequency fb can be about 10GHz or about 5GHz or about 3GHz or about 1GHz or about 900MHz. In some embodiments, each of F1 and F2 is in the range of about 100MHz to 10GHz, and the difference between F1 and F2 is in the range of about 5MHz to about 1GHz, or about 10MHz to about 800MHz, or about 10MHz to about 700MHz, or about 10MHz to about 100MHz, or about 20MHz to about 40MHz, or about 25MHz to about 35MHz. In some embodiments, each of F1 and F2 is in the range of about 850MHz to about 900MHz. For example, in some embodiments, F1 can be 869MHz, and F2 can be 894MHz. When these signals combine to form third order (when the sum of the absolute values ​​of m and n is 3) products, PIM signals having frequencies of, for example, 2F1-F2=844 MHz and 2F2-F1=919 MHz may be generated.

[0040] Figure 82 is a schematic cross-sectional view according to some embodiments, which shows the 180 degree peeling of the adhesive tape 100 from the substrate 270 having the main surface 273. The substrate 270 may be, for example, a stainless steel substrate. In some embodiments, the adhesive tape 100 or any adhesive tape described herein may have a 180 degree peel strength from the stainless steel surface 273 of at least about 0.1N / mm or at least about 0.2N / mm or at least about 0.25N / mm or at least about 0.3N / mm. The peel strength can be determined using a peeling speed of, for example, about 300mm / min (e.g., 304.8mm / min). For at least one of the first major surface 112 and the second major surface 114 facing the stainless steel surface 273, the peel strength may be in any of these ranges. In some embodiments, when the first major surface 112 faces the stainless steel surface 273 and when the second major surface 114 faces the stainless steel surface 273, the peel strength is in any of these ranges. The peel strength can be determined, for example, according to ASTM D3330 / D3330M-04 (revised in 2018) "Standard Test Method for Peel Adhesion of Pressure-Sensitive Tape". Test Method C of this standard can be used when the tape is double-sided, and Test Method A of this standard can be used when the tape is single-sided (e.g., when layer 142 is the backing layer of tape 200).

[0041] In some embodiments, the adhesive tape 300 has a peel strength within any range described herein and a resistance within any range described herein. In some such embodiments, or in other embodiments, the adhesive is substantially free of conductive fillers. In some such embodiments, or in other embodiments, the adhesive tape causes intermodulation within any range described herein.

[0042] Example

[0043] Sample preparation

[0044] Various samples were prepared by coating 30 micron thick conductive nonwoven fabrics (available from Jiaxin Purification Equipment Co. Ltd.) with an acrylic ester pressure-sensitive adhesive composition comprising about 40 weight percent solids. The acrylic ester pressure-sensitive adhesive composition comprises a bisamide crosslinking agent and is similar to those described in U.S. Patent 6,893,718 (Melancon et al.). The conductive nonwoven fabric is a polyethylene terephthalate (PET) nonwoven with a multilayer nickel / copper / nickel coating of sputtering. A Meyer rod was used to apply the conductive nonwoven from one side with an adhesive composition without a support pad or roller below. The nonwoven fabric coated was then sent to an oven to evaporate the solvent. Various Meyer rods (characterized by Meyer rod specification numbers) were used to prepare samples with a total thickness of about 40 microns, and the peel strength was measured as described under "test method". The results are provided in the following table.

[0045]

[0046] Various other samples (Examples 1 to 3) were prepared in a similar manner to those described above, but with smaller coating thicknesses. The conductive adhesive layer of Example 1 had an average thickness of about 35 microns (e.g., corresponding to Figure 1 The conductive adhesive layers of Examples 2 to 3 each have an average thickness of about 30 micrometers (eg, corresponding to Figure 1 The coating conditions (total coating weight and tension in the nonwoven) of Examples 1 to 3 were varied to obtain different thicknesses and different distributions of exposed fibers shown under "Test Results". The total coating weight was reduced in Examples 2 to 3 compared to Example 1, resulting in a thinner adhesive layer. In Examples 2 to 3, a greater tension was used in the nonwoven near the coater compared to Example 1, thereby increasing fiber exposure.

[0047] Comparative Example CE1 was 3M 5113DF, a double-sided conductive tape available from 3M Company, St. Paul, MN.

[0048] Comparative Example CE2 is 3M Conductive Transfer Tape 9701, available from 3M Company, St. Paul, MN, which is a double-sided tape with a nickel / copper coated conductive nonwoven carrier. Comparative Example CE2 has a 50 micron thick conductive adhesive layer.

[0049] Test Method

[0050] Peel test sample preparation: Use a paper towel soaked with isopropyl alcohol to wipe the stainless steel panel three times by firm hand pressure. Air dry the cleaned panel for 10 minutes. Place a 25.4 mm × 200 mm tape sample onto the stainless steel panel and roll a 1 kg rubber roller back and forth once on top of the tape to adhere the tape sample to the surface of the stainless steel panel.

[0051] 180° Peel Test (23°C, 60% Relative Humidity): All samples were kept at 23°C and 60% relative humidity for 20 minutes before peeling at room temperature (about 23°C). The process of room temperature peel test is as described in ASTM D3330 / D3330M-04 (Re-approved in 2018) "Standard Test Method for Peel Adhesion of Pressure-Sensitive Tape". The peel strength test was performed using an INSTRON tensile tester (available from Instron, Norwood, MA, US) at a peel speed of 304.8 mm / min. The sample was tested with the coated side (first major surface) facing the stainless steel panel and the opposite side (second major surface) facing the stainless steel panel.

[0052] Conductivity (Z-axis resistance through adhesive): Two strips of conductive tape were placed 10 mm x 10 mm on the center of the electrodes on the PCB board. The dimensions of the PCB board were 50 (X-axis) mm x 75 (Y-axis) mm and 1.6 mm thick. The electrodes on the board were 10 mm wide. The distance between the electrodes was 30 mm. After initial hand lamination to provide a 10 mm x 10 mm contact area between the tape and the electrodes, another PCB board was attached to the other side of the tape, the dimensions of the board being 10 mm x 50 mm. A 2 kg rubber roller was then applied across the board to simulate a typical manufacturing process that might be used to apply the tape to a surface. After a 20 minute dwell time, the DC resistance between the electrodes was measured using a micro-ohmmeter.

[0053] Passive intermodulation (PIM) test: A conductive tape is placed in a test fixture between a gold surface and a stainless steel surface. Two currents with frequencies of 860 and 890 MHz are transmitted through the thickness of the conductive tape from the gold surface to the stainless steel surface and the reflected third-order intermodulation signals are measured. This test is performed as generally described for CCIF3 IMD in Hongwei, "Measurements of Various Intermodulation Distortions (IMD, TD+N, DIM) using Multi-Instrument", Virtins Technology, August 2020.

[0054] Percent exposed fiber area: Digital images of the outermost major surface of the conductive tape were obtained using an optical microscope (Keyence VHX-5000 with VH-100R lens, available from Keyence Corporation, Osaka, Japan) and plotted relative to Figure 3 The percent exposed fiber area for each surface was determined as generally described. The average (mean) and standard deviation were determined by measuring at least 10 about 3 to 4 mm by about 3 to 4 mm areas for each surface.

[0055] Test Results

[0056] The conductive tapes were measured as described in the Test Methods. The results of the electrical properties and peel strength are reported in the following table.

[0057]

[0058] The results for exposed fiber area are reported in the table below.

[0059]

[0060]

[0061] Terms such as "about" will be understood by one of ordinary skill in the art in the context of use and description in this specification. If it is not clear to one of ordinary skill in the art in the context of use and description in this specification that "about" should be used to express the amount of feature size, quantity, and physical properties, then "about" will be understood to mean within 10% of the specified value. A quantity given as about a specified value may be exactly the specified value. For example, if it is not clear to one of ordinary skill in the art in the context of use and description in this specification, a quantity having a value of about 1 means that the quantity has a value between 0.9 and 1.1, and the value may be 1.

[0062] All references, patents, and patent applications cited above are hereby incorporated by reference in their entirety in a consistent manner. In the event of inconsistencies or conflicts between an incorporated reference portion and the present application, the information in the foregoing description shall prevail.

[0063] Unless otherwise indicated, the description of the elements in the drawings should be understood to apply equally to the corresponding elements in the other drawings. Although specific embodiments have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that the specific embodiments shown and described may be replaced with a variety of alternative and / or equivalent implementations without departing from the scope of the present disclosure. The present application is intended to cover any modification or variation or combination of the specific embodiments discussed herein. Therefore, the present disclosure is intended to be limited only by the claims and their equivalents.

Claims

1. An adhesive tape, characterized in that: The tape comprises a first layer of an electrically conductive adhesive having an outermost first major surface and a second major surface that are opposed to each other, the first layer comprising: a conductive nonwoven layer comprising metal-coated polymer fibers; and an adhesive disposed in the nonwoven layer and extending through the thickness of the nonwoven layer to define a first adhesive-exposed area and a first fiber-exposed area of ​​the nonwoven layer at the first major surface and a second adhesive-exposed area and a second fiber-exposed area of ​​the nonwoven layer at the second major surface, Wherein, in plan view, the first major surface includes the first area of ​​exposed fibers accounting for P1 area percentage, the second major surface includes the second area of ​​exposed fibers accounting for P2 area percentage, 20% < P1 < 40%, 40% <P2 < 70%,P2-P1 >20%.

2. The adhesive tape according to claim 1, characterized in that The first major surface has a distribution of the first areas of exposed fibers, and when measured within the rectangular areas of the first major surface, the distribution has a standard deviation of the exposed fiber area percentage of less than 10%, so that each rectangular area has a length and width respectively in the range of 0.7 mm to 5 mm.

3. The adhesive tape according to claim 1, characterized in that The first major surface has a distribution of the first areas of exposed fibers, the distribution having a standard deviation of exposed fiber area less than 0.28 P1 when measured within rectangular areas of the first major surface, such that each rectangular area has a length and width each within the range of 0.7 mm to 5 mm.

4. The adhesive tape according to claim 1, characterized in that The second major surface has a distribution of the second areas of exposed fibers, the distribution having a standard deviation of the exposed fiber area percentage less than 25% when measured within a rectangular area of ​​the second major surface, such that each rectangular area has a length and width respectively within the range of 0.7 mm to 5 mm.

5. The adhesive tape according to claim 1, characterized in that The second major surface has a distribution of the second areas of exposed fibers, the distribution having a standard deviation of the percentage of exposed fiber area less than 0.35 P2 when measured within the rectangular areas of the second major surface, such that each rectangular area has a length and width respectively within the range of 0.7 mm to 5 mm.

6. The adhesive tape according to claim 1, characterized in that For a regular array of rectangular areas of the first major surface totaling at least 20, each rectangular area comprising, in plan view, greater than 15 area percent of the first area of ​​exposed fibers, each rectangular area having a length and width each in the range of 0.7 mm to 5 mm.

7. The adhesive tape according to claim 1, characterized in that For a regular array of rectangular areas of the second major surface totaling at least 20, each rectangular area comprises, in plan view, greater than 30 area percent of the second region of exposed fibers, each rectangular area having a length and width each in the range of 0.7 mm to 5 mm.

8. An adhesive tape, characterized in that: The tape comprises a first layer of an electrically conductive adhesive having an outermost first major surface and a second major surface that are opposed to each other, the first layer comprising: Conductive porous media; and an adhesive disposed in the porous medium and extending through a thickness of the porous medium to define a first area at the first major surface where the adhesive is exposed and a first area at the porous medium is exposed, and a second area at the second major surface where the adhesive is exposed and a second area at the porous medium is exposed, Wherein, in a plan view, the first major surface includes the first area of ​​the exposed porous medium accounting for an area percentage of P1, the second major surface includes the second area of ​​the exposed porous medium accounting for an area percentage of P2, 20% < P1 <40%, 40% < P2 <70%, P2-P1 > 20%.

9. The adhesive tape according to claim 8, characterized in that The first major surface includes a distribution of the first areas of exposed porous media, and the distribution has a standard deviation of the percentage of exposed porous media area of ​​less than 10% when measured within the rectangular areas of the first major surface, so that each rectangular area of ​​the first major surface has a length and width respectively in the range of 0.7 mm to 5 mm, and wherein the second major surface includes a distribution of the second areas of exposed porous media, and the distribution has a standard deviation of the percentage of exposed porous media area of ​​less than 25% when measured within the rectangular areas of the second major surface, so that each rectangular area of ​​the second major surface has a length and width respectively in the range of 0.7 mm to 5 mm.

10. The adhesive tape according to any one of claims 1 to 9, characterized in that The first layer has a resistance of less than 300 mΩ in a thickness direction of the first layer, and wherein the first layer does not contain conductive filler particles.

11. The adhesive tape according to any one of claims 1 to 9, characterized in that The first layer has a resistance of less than 30 mΩ in a thickness direction of the first layer.

12. The adhesive tape according to claim 11, characterized in that The first layer is free of conductive filler particles.

13. The adhesive tape according to any one of claims 1 to 9, characterized in that The tape has a 180 degree peel strength from a stainless steel surface of at least 0.25 N / mm.

14. The adhesive tape according to any one of claims 1 to 9, characterized in that When a first electrical signal and a second electrical signal propagate between the gold surface and the stainless steel surface along the thickness direction of the first layer at respective frequencies F1 and F2, any intermodulation signal generated by the first electrical signal and the second electrical signal and having a frequency F3 equal to nF1+mF2 has a power less than -95 dB relative to the total power of the first signal and the second signal, where m and n are positive or negative integers.

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